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Last Updated :2024/07/25

研究者情報

マスター

アカウント（マスター）

  • 氏名

    HUANG　XIAOJING(ホアン　シヤオジン), ホアン　シヤオジン

所属（マスター）

  • 情報科学研究院　ビッグデータとIoTに関する共同センター

所属（マスター）

  • 情報科学研究院　ビッグデータとIoTに関する共同センター

researchmap

プロフィール情報

所属

  • シドニー工科大学, Professor
  • 北海道大学, 教授

学位

  • Ph.D., Electronic Engineering（1989年01月 Shanghai Jiao Tong University, Shanghai, China）

プロフィール情報

  • 姓

    Huang

  • 名

    Xiaojing

  • ID各種

    202401008343438571

所属

  • シドニー工科大学, Professor
  • 北海道大学, 教授

業績リスト

論文

  • Hongyang Zhang, Xiaojing Huang, J. Andrew Zhang
    IEEE Transactions on Vehicular Technology 73 1 799 - 811 2024年01月01日 
    Existing channel estimation techniques for orthogonal time frequency space (OTFS) transmission are mostly based on the pilots embedded in the two-dimensional delay-Doppler domain, which significantly increases the signaling overhead. In this paper, three variants of OTFS transmission, i.e., frequency-domain pilot-aided (FD-PA) OTFS, time-domain pilot-aided (TD-PA) OTFS, and time-domain training sequence (TD-TS) OTFS, are proposed. They enable one-dimensional channel estimation and corresponding equalization to be applied in either frequency or time domain. The relationships among different channel representations for fast fading channels are first formulated with discrete Fourier transform (DFT) and inverse DFT matrices. The transmission frame construction and associated channel estimation methods are then presented in detail for FD-PA-OTFS, TD-PA-OTFS, and TD-TS-OTFS respectively. The theoretical mean-square-error (MSE) for each of the proposed channel estimation methods is also derived. Finally, simulation results are provided to verify the MSE analyses and demonstrate that the proposed FD-PA-OTFS is the most effective transmission technique for high-mobility wireless communications in terms of diversity performance, signaling overhead, and power efficiency.
  • Xi Yang, Hang Li, Qinghua Guo, J. Andrew Zhang, Xiaojing Huang, Zhiqun Cheng
    IEEE Transactions on Vehicular Technology 2024年 
    In this work, we study sensing-aided uplink transmission in an integrated sensing and communication (ISAC) vehicular network with the use of orthogonal time frequency space (OTFS) modulation. To exploit sensing parameters for improving uplink communications, the parameters must be first associated with the transmitters, which is a challenging task. We propose a scheme that jointly conducts parameter association, channel estimation and signal detection by formulating it as a constrained bilinear recovery problem. Then we develop a message passing algorithm to solve the problem, leveraging the bilinear unitary approximate message passing (Bi-UAMP) algorithm. Numerical results validate the proposed scheme, which show that relevant performance bounds can be closely approached.
  • Anh Tuyen Le, Xiaojing Huang, Can Ding, Hao Zhang, Y. Jay Guo
    IEEE Transactions on Microwave Theory and Techniques 2024年 
    In-band full-duplex (IBFD) technology has been extensively researched over the last decade, and numerous techniques have been proposed to cancel self-interference (SI) caused by the simultaneously transmitted local in-band signal. Although some prototypes for SI cancellation (SIC) have been published, there are limited works demonstrating the communication performance of the IBFD system. The noise enhancement caused by analog and/or digital SIC is mostly ignored in the literature. This article presents a prototype for an IBFD system with solutions in three domains of SI mitigation. A practical structure for joint analog and digital SIC is proposed and implemented using off-the-shelf components. The transmit data frame is designed to align with the track/hold control signaling so that the irreducible noise caused by the analog SIC can be avoided. By combining a full-duplex antenna, an analog SIC filter, and a field-programmable gate array (FPGA) platform, this prototype successfully demonstrates the performance of the desired IBFD communications. Experiments on the prototype with 50-MHz bandwidth signaling show that under a certain hardware condition, the proposed SIC solution can sufficiently mitigate the SI with 75 dB of cancellation, and a low bit error rate (BER $< $ $10^{-4}$ ) is demonstrated to allow practical applications.
  • Le Chung Tran, Anh Tuyen Le, Xiaojing Huang, Eryk Dutkiewicz, Duy Ngo, Attaphongse Taparugssanagorn
    IEEE Sensors Letters 7 11 2023年11月01日 
    Unmanned aerial vehicles (UAVs)-assisted wireless sensor networks (WSNs) have tremendous potential applications due to their flexibility and rapid deployment. Hybrid time-of-arrival (TOA) and angle-of-arrival (AOA) localization techniques are commonly used due to their high accuracy. The conventional TOA/AOA localization algorithms require both zenith and azimuth angle estimations at each agent. Since a zenith-and-azimuth AOA estimation requires an L-shape antenna array and complicated 2-D signal processing, conventional TOA/AOA algorithms lead to both hardware and computational complexity and high power consumption at each agent. This letter proposes a hybrid TOA/AOA localization algorithm, named $\text{T1A}_{a}$, to reduce the agents' complexity. $\text{T1A}_{a}$ only combines TOA-ranging with the azimuth angle estimation. Thereby, agents only require a 1-D antenna array, less complicated signal processing, and thus, lower power consumption. Such improvements are important for power-limited WSNs and Internet-of-Things (IoT) systems. Simulations are conducted to prove that the proposed $\text{T1A}_{a}$ technique can achieve similar performance as conventional TOA/AOA methods, while significantly simplifying agents' complexity.
  • Mingfei Tong, Xiaojing Huang, J. Andrew Zhang
    IEEE Transactions on Communications 71 8 4851 - 4861 2023年08月01日 
    Faster-than-Nyquist (FTN) signaling can improve spectral efficiency and enable high-speed transmission for next-generation communication systems. One of the most significant challenges in FTN transmission is how to remove the inter-symbol interference (ISI). In this paper, we propose a novel decision-directed successive interference cancellation (DDSIC) based on frequency-domain minimum-mean-square-error (MMSE) equalization for practical FTN systems. To reduce the computational complexity, the detection process is performed frame-by-frame in the frequency domain. In addition, we derive the theoretical bit error rate (BER) expression for each iteration in DDSIC as well as the BER lower bound for M -ary quadrature amplitude modulated FTN systems. The simulation results verify the theoretical analyses and demonstrate that our proposed method enables lower complexity and better performance compared with state-of-the-art methods.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Robert W. Heath, Y. Jay Guo
    IEEE Communications Magazine 61 7 172 - 178 2023年07月01日 
    Joint communications and sensing (JCAS) is potentially a hallmark technology for the sixth generation mobile network (6G). Most existing JCAS designs are based on digital arrays, analog arrays with tunable phase shifters, or hybrid arrays, which are effective but are generally complicated to design and power inefficient. This article introduces the energy-efficient and easy-to-design multi-beam antenna arrays (MBAAs) for JCAS. Using pre-designed and fixed analog devices, such as lens or Butler matrix, MBAA can simultaneously steer multiple beams yet with negligible power consumption compared with other techniques. Moreover, MBAAs enable flexible beam synthesis, accurate angle-of-arrival estimation, and easy handling/utilization of the beam squint effect. All these features have not been well captured by the JACS community yet. To promote the awareness of them, we intuitively illustrate them and also exploit them for constructing a multi-beam JCAS framework. Finally, the challenges and opportunities are discussed to foster the development of green JCAS systems.
  • Peisen Cai, Hang Li, Qinghua Guo, Xiaojing Huang
    IEEE Wireless Communications Letters 12 7 1164 - 1168 2023年07月01日 
    Dual pulse shaping (DPS) transmissions enable the use of A/D and D/A converters with half of the symbol rate, alleviating the requirement of high speed conversion devices in wideband millimeter wave communications. In this letter, we focus on DPS equalization and propose a unitary approximate message passing (UAMP) based equalization technique. Two DPS transmission schemes are considered, and by exploiting the special structure of the system transfer matrix, two low-complexity equalizers are developed with the fast Fourier transform (FFT). Simulation results show that significant performance gains can be achieved by the UAMP-based equalizers, compared to the conventional DPS equalizer.
  • J. Andrew Zhang, Kai Wu, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Vehicular Technology 72 6 8152 - 8157 2023年06月01日 
    Beam alignment is a process for receive and transmit antenna arrays to find the correct beamforming directions. It is typically based on beam scanning and peak-energy searching, which lead to time-consuming beam training process in communication protocols, such as 802.11ad for vehicular networks. In this correspondence, we propose a fast beam alignment method for analog arrays, based on directly estimating the angle-of-arrival (AoA) of the incoming signals. We propose simple and highly efficient AoA estimators, by approximating the power of the array response as a Gaussian function. One estimator is based on the power ratio and can coherently combine multiple measurements scanned at arbitrary intervals and with different beam widths. The other two are based on an innovative idea of Gaussian curve fitting with weighted least square techniques, and one of them can even work without knowing the beam width. Simulation results validate the effectiveness of the proposed scheme.
  • Xiaojing Huang, Anh Tuyen Le, Y. Jay Guo
    IEEE Transactions on Wireless Communications 22 4 2364 - 2378 2023年04月 
    An effective and practical joint analog and digital self-interference cancellation (SIC) scheme without additional signalling overhead for an I/Q imbalanced full duplex transceiver is proposed in this paper. This scheme combines an I/Q imbalanced analog least mean square (ALMS) loop at the transceiver radio frequency frontend and a two-stage digital signal processing (DSP) at the digital baseband to achieve excellent SIC performance with low complexity. The steady state weighting coefficients of the I/Q imbalanced ALMS loop with periodical transmitted signal and the loop's convergence behaviour are firstly analysed. The residual SI is then modelled as the output of a time-varying widely linear system. With a track/hold control mechanism applied to the ALMS loop, the system model for digital SIC is further presented, followed by the DSP algorithms suitable for real-time implementation. The noise enhancement in each stage digital cancellation is also analysed and formulated. Finally, simulation results are provided to verify the theoretical analyses and demonstrate the overall SIC performance.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Lajos Hanzo
    IEEE Transactions on Communications 71 3 1785 - 1797 2023年03月01日 
    Beamspace millimeter-wave (mmWave) and terahertz (THz) massive MIMO constitute attractive schemes for next-generation communications, given their abundant bandwidth and high throughput. However, their user and beam selection problem has not been efficiently addressed yet. Inspired by this challenge, we develop low-complexity solutions explicitly. In contrast to the zero forcing in the prior art, we introduce the dirty paper coding (DPC) into the joint user and beam selection problem. We unveil the compelling properties of the DPC sum rate in beamspace massive MIMO, showing its monotonic evolution against the number of users and beams selected. We then exploit its beneficial properties for substantially simplifying the joint user and beam selection problem. Furthermore, we develop a set of algorithms striking unique trade-offs for solving the simplified problem, facilitating simultaneous user and beam selection based on partial beamspace channels for the first time. Additionally, we derive the sum rate bound of the algorithms and analyze their complexity. Our simulation results validate the effectiveness of the proposed design and analysis, confirming their superiority over prior solutions.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Internet of Things Journal 10 3 1973 - 1989 2023年02月01日 
    Effective wireless communications are increasingly important in maintaining the successful closed-loop operation of mission-critical Industrial Internet of Things (IIoT) applications. To meet the ever-increasing demands on better wireless communications for IIoT, we propose an orthogonal time-frequency space (OTFS) waveform-based joint communication and radio sensing (JCAS) scheme - an energy-efficient solution for not only reliable communications but also high-accuracy sensing. OTFS has been demonstrated to have higher reliability and energy efficiency than the currently popular IIoT communication waveforms. JCAS has also been highly recommended for IIoT, since it saves cost, power, and spectrum compared to having two separate radio frequency systems. Performing JCAS based on OTFS, however, can be hindered by a lack of effective OTFS sensing. This article is dedicated to filling this technology gap. We first design a series of echo preprocessing methods that successfully remove the impact of communication data symbols in the time-frequency domain, where major challenges, such as intercarrier and intersymbol interference and noise amplification, are addressed. Then, we provide a comprehensive analysis of the signal-to-interference-plus-noise ratio (SINR) for sensing and optimize a key parameter of the proposed method to maximize the SINR. The extensive simulations show that the proposed sensing method approaches the maximum-likelihood estimator with respect to the estimation accuracy of target parameters and manifests applicability to wide ranges of key system parameters. Notably, the complexity of the proposed method is only dominated by a 2-D Fourier transform.
  • Junwen Deng, Hang Li, Jian Andrew Zhang, Xiaojing Huang, Zhiqun Cheng
    Micromachines 14 2 2023年02月 
    The performance of millimeter wave (mmWave) line-of-sight multiple input multiple output (LOS MIMO) systems using hybrid arrays of planar subarrays was studied. We characterized the achievable maximum spatial multiplexing gain for such LOS MIMO systems by the measures of spectral efficiency and effective degree of freedom (EDoF). By proposing a joint plane-wave and spherical-wave-based general 3D channel model, we derived the optimal design parameters in the analog domain, i.e., the optimal subarray separation products, and analyzed their sensitivity on the system performance. We also gave analytical eigenvalue expressions of the equivalent LOS MIMO channel matrix, which are applicable to the case of a non-optimal design, as well as the upper and lower bounds of the EDoF for system performance evaluation. A piecewise uniform quantization codebook was further designed for quantizing phase shifter values in practical applications. The numerical and simulation results show that planar subarrays are superior to traditional arrays in terms of spectral efficiency and EDoF in Ricean fading channels because they are more robust to the change in the communication distance and the deviation from the optimal design. The use of hybrid arrays of planar subarrays effectively removes the limitation of mmWave LOS MIMO systems using traditional arrays, through which, the conventional Rayleigh distance criterion has to be satisfied to achieve the optimal performance.
  • Trong Dai Hoang, Xiaojing Huang, Peiyuan Qin
    IEEE Signal Processing Letters 30 838 - 842 2023年 
    In this letter, we investigate a novel optimization approach to direction-of-arrival (DoA) estimation for a lens antenna array. Inspired by a property of the sinc function and ${\ell _{2 } }$-norm optimization, we develop the gradient descent-based spatial spectrum reconstruction (GD-SSR) to estimate the DoAs based on the sum signal covariance vector (SSCV). Our proposed algorithm does not require a priori knowledge of signal number and has a lower complexity compared with existing techniques while achieving a better estimation performance, even in a low-SNR regime. In addition, the proposed model does not require any pretraining process as prior learning-based methods. The simulation results show that our scheme not only outperforms other techniques but also resolves the angular ambiguity problem.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE International Conference on Communications 2023-May 2747 - 2752 2023年 
    Integrating sensing into wifi platforms, referred to as wifi sensing, provides an efficient and device-free means for indoor monitoring/localization with low cost. Clock asynchrony is one of the most challenging issues in wifi sensing. A mainstream solution to date employs cross-antenna processing to suppress the clock offsets that are common to all antennas. Such methods, however, may suffer from issues such as mirrored targets and noise enhancement etc. This paper develops a novel wifi sensing scheme. It embodies accurate and low-complexity methods for estimating the timing and frequency offsets as well as the angle-of-arrival (AoA), all from the LoS path. It also involves a coherent Doppler processing method which effectively suppresses static paths and accurately estimates the Doppler by enjoying the coherent processing gain. Corroborated by experimental results using open Widar2.0 data, the proposed design is able to precisely recover the velocity traces in various indoor scenarios.
  • Kai Wu, J. Andrew Zhang, Zhitong Ni, Xiaojing Huang, Y. Jay Guo, Shanzhi Chen
    IEEE Internet of Things Journal 2023年 
    Joint communications and sensing (JCAS) have the potential to improve the overall energy, cost and frequency efficiency of Internet-of-Things (IoT) systems. As a first effort, we propose to optimize the MIMO-OFDM data symbols carried by sub-carriers for better time-and spatial-domain signal orthogonality. This can reduce inter-target and inter-antenna interference, enabling high-quality sensing. We establish an optimization problem that modifies data symbols on sub-carriers to enhance the above-mentioned signal orthogonality. We also develop an efficient algorithm to solve the problem based on the majorization-minimization framework. Moreover, we discover unique signal structures and features from the newly modeled problem, which substantially reduce the complexity of majorizing the objective function. We also develop new projectors to enforce the feasibility of the obtained solution. Simulations show that to achieve the same sensing performance, the optimized waveform can reduce the signal-to-noise ratio (SNR) requirement by 3~4.5 dB compared with the original waveform, while the SNR loss for the uncoded bit error rate is only 1~1.5 dB.
  • Ting Zhang, Hao Zhang, He Zhu, Xiaojing Huang, Hajime H. Suzuki, Joseph Pathikulangara, Ken W. Smart, Jia Du, Jay Y. Guo
    22nd International Symposium on Communications and Information Technologies, ISCIT 2023 387 - 388 2023年 
    A wireless communications system with a carrier frequency of 245 GHz and a data rate of 30 gigabits per second (Gbps) at a 1.2 m distance is demonstrated. The system consists of low-complexity and real-time baseband modules to provide the high-speed wideband signal processing capability. Multi-channel base-band signals are combined and converted to 15.65±6.25 GHz wideband intermediate frequency (IF) signals. The semiconductor-based THz front-end modules, including mixers and amplifiers, are applied for signal up-and down-conversion and transmission at 245 GHz. A 50 Gbps wireless communication system is currently development, and the technical progress will be presented at the conference. The new wireless communication technology will find great potential for future high-speed communications beyond 5G technology, especially, for space applications, such as intersatellite communication where atmospheric attenuation is negligible.
  • Hongyang Zhang, Xiaojing Huang, J. Andrew Zhang
    22nd International Symposium on Communications and Information Technologies, ISCIT 2023 1 - 6 2023年 
    Orthogonal time frequency space (OTFS) modulation offers attractive performance in coping with doubly selective channels. In this paper, we propose a time-domain trainingsequence-aided transmission and an offset gradient descent equalization to reduce channel estimation and equalization complexity and enable better adaption to channels with either integer or fractional Doppler shift. Our proposed scheme leverages an extendedframe OTFS structure, which consists of multiple original OTFS frames, to achieve finer Doppler resolution and hence alleviate the impact of fractional Doppler when the frame is sufficiently long. We also propose an offset gradient descent equalization method, which exploits the structure of the channel matrix to significantly reduce the complexity. Simulation results validate the scheme and demonstrate that our proposed transmission scheme can achieve similar performance with MMSE equalization at significantly reduced complexity.
  • Anh Tuyen Le, Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications Letters 11 11 2425 - 2429 2022年11月01日 
    High transmit power in-band full-duplex (IBFD) systems are promising due to their tremendous advantages in both civilian and military applications. However, mitigating self-interference (SI) in such a high transmit power condition is significantly challenging. A two-stage analog filtering structure is proposed in this letter to tackle this problem successfully. The first stage is based on a vector modulator and a balun to cancel the direct leakage SI component. The second stage is constructed from an analog least mean square (ALMS) loop to adaptively cancel the residual SI. The performance of the second stage with nonlinear transmit signals is investigated analytically. Simulation results show that a total 75 dB of SI cancellation can be achieved by the proposed structure, ensuring the residual SI falls into the linear range of the analog-to-digital converter.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    Sensors 22 22 2022年11月 
    Employing a cyclic prefixed OFDM (CP-OFDM) communication waveform for sensing has attracted extensive attention in vehicular integrated sensing and communications (ISAC). A unified sensing framework was developed recently, enabling CP-OFDM sensing to surpass the conventional limits imposed by underlying communications. However, a false target issue still remains unsolved. In this paper, we investigate and solve this issue. Specifically, we unveil that false targets are caused by periodic cyclic prefixes (CPs) in CP-OFDM waveforms. We also derive the relation between the locations of false and true targets, and other features, e.g., strength, of false targets. Moreover, we develop an effective solution to remove false targets. Simulations are provided to confirm the validity of our analysis and the effectiveness of the proposed solution. In particular, our design can reduce the false alarm rate caused by false targets by over 50% compared with the prior art.
  • Anh Tuyen Le, Xiaojing Huang, Le Chung Tran, Y. Jay Guo
    IEEE Transactions on Vehicular Technology 71 10 10683 - 10693 2022年10月01日 
    Frequency-dependent in-phase/quadrature-phase imbalance (IQI) is a critical hardware impairment, which affects the performance of the self-interference (SI) cancellation structure in full-duplex systems. A novel frequency-dependent IQI model is proposed in this paper, providing a theoretical tool to evaluate the impacts of this impairment in the analog domain. The model is then applied to investigate the performance of the analog least mean square (ALMS) loop under both frequency-selective and frequency-independent IQI. The degradation in the SI cancellation performance of the ALMS loop is revealed and its upper bound is derived. Numerical results show that the ALMS loop is resilient to both types of IQI with the maximum level of only 3.5 dB performance degradation even when the image rejection ratio is just 15 dB.
  • Hang Li, Xiaojing Huang, Jian Andrew Zhang, Hao Zhang, Zhiqun Cheng
    IET Communications 16 17 2091 - 2104 2022年10月 
    Due to difficulties in manufacturing, data conversion devices with extremely high sampling rate are becoming the bottleneck in realising high-speed communication systems with a large bandwidth. Dual pulse shaping (DPS) transmission allows half-symbol-rate conversion devices to be used for two parallel data streams to achieve full-rate transmission, and is proved to be an effective solution. Here, two sets of ideal sinc-function based complementary Nyquist pulses for DPS transmission are proposed. Theoretically, it is shown that the proposed pulses satisfy the inter-symbol and cross-symbol interference-free conditions, and can achieve full-Nyquist-rate transmission with half of the sampling rate. With reference to commercially available D/As, two sets of practical dual spectral shaping pulses are further proposed, and the close relationship between the ideal and practical pulses are disclosed. Performance analysis for linear equalisation is provided in the presence of both timing offset between dual shaping pulses and carrier-frequency offset. Two approaches are then proposed to improve the system robustness by adjusting the clock phase of the D/As and A/Ds. Simulation results are presented to provide a comparison between the proposed DPS transmission schemes and the state of the art, in terms of the performance metrics of peak-to-average power ratio and bit error rate.
  • Ting Zhang, Hao Zhang, Xiaojing Huang, Hajime Suzuki, Joseph Pathikulangara, Ken Smart, Jia Du, Jay Guo
    Photonics 9 10 2022年10月 
    This paper presents a 245 GHz wireless communications system with a data rate of 30 Giga bits per second (Gbps) at a 1.2 m distance, which proves the potential for future high-speed communications beyond 5G technology. The system consists of low-complexity and real-time base-band modules to provide the high-speed wideband signal processing capability. Multi-channel base-band signals are combined and converted to 15.65 ± 6.25 GHz wideband intermediate frequency (IF) signals. A novel 245 GHz waveguide bandpass filter (BPF) with low loss and high selectivity is designed and applied to a terahertz (THz) front-end for image rejection and noise suppression. Configuration of the base-band, IF, and THz front-end modules is also given in detail. The 245 GHz wireless communication link is demonstrated over a distance of 1.2 m.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Wireless Communications 21 7 5392 - 5405 2022年07月01日 
    Dual-function radar-communication (DFRC) based on frequency hopping (FH) MIMO radar (FH-MIMO DFRC) achieves symbol rate much higher than radar pulse repetition frequency. Such DFRC, however, is prone to eavesdropping due to the spatially uniform illumination of an FH-MIMO radar. In this paper, we reveal the potential of using permutations of hopping frequencies to achieve secure and high-speed FH-MIMO DFRC. Specifically, we identify the angle-dependent issue in detecting permutations and develop an element-wise phase compensation (EPC) to solve the issue for a legitimate user (Bob). EPC makes the demodulation at an eavesdropper (Eve) conditioned on knowing the angle-of-departure (AoD) of Bob. We also propose the random sign reversal (RSR) technique which randomly selects several antennas over hops and reverses their signs. Owing to EPC, there is a sign rule available for Bob. We employ the rule and develop a low-complexity algorithm for Bob to remove RSR. We further prove that, given the same signal-to-noise ratio, RSR plus EPC make the demodulation performance of Eve inferior to that of Bob in most angular regions. Confirmed by simulation, our design achieves substantially high physical layer security for FH-MIMO DFRC, improves demodulation performance compared with existing designs, and reduces mutual interference among radar targets.
  • Xiaolu Yu, Hang Li, Jian Andrew Zhang, Xiaojing Huang, Zhiqun Cheng
    Sensors 22 14 2022年07月 
    The millimeter wave (mmWave) channel is dominated by line-of-sight propagation. Therefore, the acquisition of angle-of-arrival (AoA) and polarization state of the wave is of great significance to the receiver. In this paper, we investigate AoA and polarization estimation in a mmWave system employing dual-polarized antenna arrays. We propose an enhanced AoA estimation method using a localized hybrid dual-polarized array for a polarized mmWave signal. The use of dual-polarized arrays greatly improves the calibration of differential signals and the signal-to-noise ratio (SNR) of the phase offset estimation between adjacent subarrays. Given the estimated phase offset, an initial AoA estimate can be obtained, and is then used to update the phase offset estimation. This leads to a recursive estimation with improved accuracy. We further propose an enhanced polarization estimation method, which uses the power of total received signals at dual-polarized antennas to compute the cross-correlation-to-power ratio instead of using only one axis dipole. Thus the accuracy of polarization parameter estimation is improved. We also derive a closed-form expression for mean square error lower bounds of AoA estimation and present an average SNR analysis for polarization estimation performance. Simulation results demonstrate the superiority of the enhanced AoA and polarization parameter estimation methods compared to the state of the art.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Journal on Selected Areas in Communications 40 6 1873 - 1889 2022年06月01日 
    Integrating sensing into standardized communication systems can potentially benefit many consumer applications that require both radio frequency functions. However, without an effective sensing method, such integration may not achieve the expected gains of cost and energy efficiency. Existing sensing methods, which use communication payload signals, either have limited sensing performance or suffer from high complexity. In this paper, we develop a novel and flexible sensing framework which has a complexity only dominated by a Fourier transform and also provides the flexibility in adapting to different sensing needs. We propose to segment a whole block of echo signal evenly into sub-blocks; adjacent ones are allowed to overlap. We design a virtual cyclic prefix (VCP) for each sub-block that allows us to employ two common ways of removing communication data symbols and generate two types of range-Doppler maps (RDMs) for sensing. We perform a comprehensive analysis of the signal components in the RDMs, proving that their interference-plus-noise (IN) terms are approximately Gaussian distributed. The statistical properties of the distributions are derived, which leads to the analytical comparisons between the two RDMs as well as between the prior and our sensing methods. Moreover, the impact of the lengths of sub-block, VCP and overlapping signal on sensing performance is analyzed. Criteria for designing these lengths for better sensing performance are also provided. Extensive simulations validate the superiority of the proposed sensing framework over prior methods in terms of signal-to-IN ratios in RDMs, detecting performance and flexibility.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Aerospace and Electronic Systems Magazine 37 4 42 - 54 2022年04月 
    Enabled by the advancement in radio frequency technologies, the convergence of radar and communication systems becomes increasingly promising and is envisioned as a key feature of future sixth-generation networks. Recently, the frequency-hopping (FH) MIMO radar has been introduced to underlay dual-function radar-communication (DFRC) systems. Superior to many previous radar-centric DFRC designs, the symbol rate of FH-MIMO radar-based DFRC (FH-MIMO DFRC) can exceed the radar pulse repetition frequency. However, many practical issues, particularly those crucial to achieving effective data communications, are unexplored or unsolved. To promote the awareness and general understanding of the novel DFRC, this article is devoted to providing a timely introduction of FH-MIMO DFRC. We comprehensively review many essential aspects of the novel DFRC: channel/signal models, signaling strategies, modulation/demodulation processing, and channel estimation methods, to name a few. We also highlight major remaining issues in FH-MIMO DFRC and suggest potential solutions to shed light on future research directions.
  • Juthatip Wisanmongkol, Attaphongse Taparugssanagorn, Le Chung Tran, Anh Tuyen Le, Xiaojing Huang, Christian Ritz, Eryk Dutkiewicz, Son Lam Phung
    IET Wireless Sensor Systems 12 2 33 - 55 2022年04月 
    The authors investigate the use of deep learning in wireless indoor localization to address the shortcomings of the existing range-based (e.g. trilateration and triangulation) and range-free (e.g. fingerprinting) localization. Instead of relying on geometric models and hand-picked features, deep learning can automatically extract the relationship between the observed data and the target's location. Nevertheless, a deep neural network (DNN) model providing a satisfactory accuracy might perform differently when it is retrained in the deployment. To mitigate this issue, the authors propose an ensemble method where DNN models obtained from multiple training sessions are combined to locate the target. In the authors' evaluation, several DNN models are trained on the data, which consists of the received signal strength (RSS), angle of arrival (AOA), and channel state information (CSI), used in the existing hybrid RSS/AOA and RSS/CSI fingerprinting, and their root-mean-square error (RMSE) values are compared accordingly. The results show that the proposed method achieves the lower RMSE than the existing methods, and the RMSE can be lowered by up to 1.47 m compared with the ones obtained from a single model. Moreover, for some DNN models, the RMSE values are even lower than the minimum RMSE obtained by their single-model counterparts.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Microwave Theory and Techniques 70 4 2499 - 2511 2022年04月 
    This article proposes a low-cost three-dimensional (3-D) millimeter-wave (MMW) holographic imaging system using helical scanning with multiple receivers to achieve a fast continuous scanning over a large two-dimensional (2-D) cylindrical surface. First, the system geometry and its imaging process based on the back-projection algorithm (BPA) are presented. The corresponding imaging point spread function (PSF) and resolutions are analyzed accordingly. To reduce the computational cost significantly, a novel 3-D helical imaging algorithm is then proposed based on the piecewise constant Doppler (PCD) principle. The slant range difference resulting from the helical scanning can be compensated jointly along angular and vertical directions. The proposed imaging is prototyped using the AWR1843 radar sensor from Texas Instruments (TIs) and a moving platform composed of step motors and a micro-controller unit (MCU). The digital imaging process and the number of the required complex multiplications are also discussed in detail. Finally, simulation and experimental results are provided to validate the accuracy and efficiency of the proposed imaging system.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Diep N. Nguyen, Asanka Kekirigoda, Kin Ping Hui
    Sensors 22 6 2022年03月02日 
    The proliferation of wireless applications, the ever-increasing spectrum crowdedness, as well as cell densification makes the issue of interference increasingly severe in many emerging wireless applications. Most interference management/mitigation methods in the literature are problem-specific and require some cooperation/coordination between different radio frequency systems. Aiming to seek a more versatile solution to counteracting strong interference, we resort to the hybrid array of analog subarrays and suppress interference in the analog domain so as to greatly reduce the required quantization bits of the analog-to-digital converters and their power consumption. To this end, we design a real-time algorithm to steer nulls towards the interference directions and maintain flat in non-interference directions, solely using constant-modulus phase shifters. To ensure sufficient null depth for interference suppression, we also develop a two-stage method for accurately estimating interference directions. The proposed solution can be applicable to most (if not all) wireless systems as neither training/reference signal nor cooperation/coordination is required. Extensive simulations show that more than 65 dB of suppression can be achieved for 3 spatially resolvable interference signals yet with random directions.
  • Kai Wu, Jian Andrew Zhang, Xiaojing Huang, Yingjie Jay Guo
    Sensors 22 4 2022年02月02日 
    Joint communications and sensing (JCAS) has recently attracted extensive attention due to its potential in substantially improving the cost, energy and spectral efficiency of Internet of Things (IoT) systems that need both radio frequency functions. Given the wide applicability of orthogonal frequency division multiplexing (OFDM) in modern communications, OFDM sensing has become one of the major research topics of JCAS. To raise the awareness of some critical yet long-overlooked issues that restrict the OFDM sensing capability, a comprehensive overview of OFDM sensing is provided first in this paper, and then a tutorial on the issues is presented. Moreover, some recent research efforts for addressing the issues are reviewed, with interesting designs and results highlighted. In addition, the redundancy in OFDM sensing signals is unveiled, on which, a novel method is based and developed in order to remove the redundancy by introducing efficient signal decimation. Corroborated by analysis and simulation results, the new method further reduces the sensing complexity over one of the most efficient methods to date, with a minimal impact on the sensing performance.
  • Qiaolin Shi, Nan Wu, Diep N. Nguyen, Xiaojing Huang, Hua Wang, Lajos Hanzo
    IEEE Transactions on Communications 70 2 1261 - 1275 2022年02月01日 
    The integration of terrestrial and satellite communications (Satcom) is advocated for satisfying the challenging requirements of seamless, high-performance services. However, both the bandwidth and the power available are limited over satellite channels. In this paper, we propose index modulation (IM) and code-aided Satcom by conveying information by a pair of distinguishable constellation modes and their permutations. In order to combat both the linear and nonlinear distortion imposed by satellite channels, we conceive a factor graph (FG)-based iterative detection algorithm for Satcom relying on dual-mode (DM) IM (Sat-DMIM). The correlation amongst Sat-DMIM symbols imposed by both the channel-induced dispersion and the mode-selection mapping is explicitly represented by the FG constructed. Then the amalgamated belief propagation (BP) and mean field (MF) message passing algorithm is derived over this FG for detecting both the IM bits and the classic constellation mapping bits, while eliminating both the linear and nonlinear distortions. The complexity of the iterative detection algorithm is reduced by linearizing some high-order terms appearing in nonlinear distortion components using the a posteriori estimates of the Sat-DMIM symbols obtained from the previous iteration. Our simulation results demonstrate the power of the proposed amalgamated BP-MF-based and partial linearization approximation-based iterative detection algorithms.
  • Zhitong Ni, J. Andrew Zhang, Kai Yang, Xiaojing Huang, Theodoros A. Tsiftsis
    IEEE Transactions on Communications 70 2 1276 - 1289 2022年02月01日 
    Joint communication and radar sensing (JCAS) integrates the two functions into one system, sharing one transmitted signal. In this paper, we investigate JCAS waveform optimization in communication-centric systems, where a base station (BS) detects radar targets and communicates with mobile users simultaneously. Different from existing works, we study multi-metric optimizations for a practical low-cost system and establish their connections. To relax the requirement of full-duplex technology, we add a single receive antenna for sensing at the BS, which is synchronized with and spatially separated from the JCAS transmit array. We first optimize precoders for communications and radar, individually. Then, we formulate a JCAS waveform optimization problem that constrains either mutual information (MI) or Cramér-Rao bound (CRB) of radar and maximizes the relaxed signal-to-interference-plus-noise rate (SINR) of communications. Exploiting the geometric characteristic of the relaxed SINR, we provide a closed-form solution under certain conditions and propose a numerical iteration algorithm that works in all situations. We also disclose the connections between optimizations with constraining MI and CRB, using numerical results. Finally, simulation results are provided and validate the proposed optimization solutions.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Geoscience and Remote Sensing 60 2022年 
    This article presents an universal circular synthetic aperture radar (SAR) (UCSAR) by which the targets to be observed at any radial distance can be imaged, thus making SAR imaging possible in a more general scenario with a circular movement of the radar platform. The UCSAR point spread function (PSF) is firstly analyzed based on the time-domain correlation imaging approach, and thus a three-dimension (3-D) spatial variant PSF of the target can be formulated. The closed-form PSF expressions with single-frequency and frequency-modulated continuous wave (FMCW) transmitted signals are derived respectively to quantify the imaging resolutions, showing that the PSF is a product of a sinc function and a zeroth-order Bessel function when using a wideband FMCW signal. Secondly, a fast UCSAR imaging algorithm and its further simplified version are proposed to reduce the computational cost significantly based on the piecewise constant Doppler (PCD) principle. To quantify the imaging performance, we derive an error function of the slant range approximation for the proposed algorithm, serving as a practical guideline for the UCSAR parameter selection. Finally, the simulation and experimental results are provided to validate the PSF analysis, the fast imaging algorithm, and the implementation of the proposed UCSAR.
  • J. Andrew Zhang, Md Lushanur Rahman, Kai Wu, Xiaojing Huang, Y. Jay Guo, Shanzhi Chen, Jinhong Yuan
    IEEE Communications Surveys and Tutorials 24 1 306 - 345 2022年 
    Mobile network is evolving from a communication-only network towards one with joint communication and radar/radio sensing (JCAS) capabilities, that we call perceptive mobile network (PMN). Radio sensing here refers to information retrieval from received mobile signals for objects of interest in the environment surrounding the radio transceivers, and it may go beyond the functions of localization, tracking, and object recognition of traditional radar. In PMNs, JCAS integrates sensing into communications, sharing a majority of system modules and the same transmitted signals. The PMN is expected to provide a ubiquitous radio sensing platform and enable a vast number of novel smart applications, whilst providing non-compromised communications. In this paper, we present a broad picture of the motivation, methodologies, challenges, and research opportunities of realizing PMN, by providing a comprehensive survey for systems and technologies developed mainly in the last ten years. Beginning by reviewing the work on coexisting communication and radar systems, we highlight their limits on addressing the interference problem, and then introduce the JCAS technology. We then set up JCAS in the mobile network con and envisage its potential applications. We continue to provide a brief review of three types of JCAS systems, with particular attention to their differences in design philosophy. We then introduce a framework of PMN, including the system platform and infrastructure, three types of sensing operations, and signals usable for sensing. Subsequently, we discuss required system modifications to enable sensing on current communication-only infrastructure. Within the con of PMN, we review stimulating research problems and potential solutions, organized under nine topics: performance bounds, waveform optimization, antenna array design, clutter suppression, sensing parameter estimation, resolution of sensing ambiguity, pattern analysis, networked sensing under cellular topology, and sensing-assisted communications. We conclude the paper by listing key open research problems for the aforementioned topics and sharing some lessons that we have learned.
  • Xiaojing Huang, Yijiang Nan, Y. Jay Guo
    IEEE Transactions on Geoscience and Remote Sensing 60 2022年 
    A novel noncoherent microwave imaging principle with periodical or random radio frequency (RF) illumination is proposed in this article. Implemented with circular array synthetic aperture radar (SAR) frontend and low-complexity signal processing algorithms, the imaging device, called RF camera, achieves some desired properties similar to an optical camera, such as the capability to operate with multiple uncoordinated illuminators. Different from conventional multistatic imaging, the RF camera does not require any knowledge about an illuminator's location or signal waveform. A static illumination sensor (IS) can be used to provide a reference signal for image reconstruction. With periodical illumination, the RF camera can even operate without IS, but the imaging performance can be improved with IS. With random illumination, the IS is necessary for the RF camera operation, and the imaging distortion can be described by a point blur function. Theoretical analyses on the imaging signal-to-noise ratios are performed under different RF camera operation modes. Simulation and experimental tests are conducted using 77-GHz millimeter wave frequency to verify the noncoherent imaging principle and its performance.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Geoscience and Remote Sensing 60 2022年 
    This article proposes a new synthetic aperture radar (SAR), named as panoramic SAR, based on a combination of linear and rotational SARs, by which a large 360° panoramic view of the observed scene can be reconstructed. First, the system geometry and its imaging process based on the back-projection algorithm (BPA) are presented. The combined movement constitutes a 2-D synthetic aperture, and thus higher imaging resolutions can be obtained. The corresponding resolution analysis and the sampling criteria are discussed accordingly. Then, a novel dynamic piecewise compensation (DPC) algorithm, a recursive imaging process, is proposed to reduce the processing complexity significantly. The imaging implementation and the complexity are also studied respectively. Finally, a prototype of panoramic SAR is built based on an frequency-modulated continuous wave (FMCW) radar and a moving platform, and the simulation and experimental results are provided to validate the proposed panoramic SAR principle and the DPC algorithm.
  • Zhitong Ni, J. Andrew Zhang, Xiaojing Huang, Kai Yang
    2022 IEEE International Conference on Communications Workshops, ICC Workshops 2022 824 - 829 2022年 
    This paper proposes a scheme that solves two challenging problems in parameter estimation using communication signals: (1) asynchronous transmitter and receiver; and (2) sensing receiver with a small number of antennas. These problems exist in parameter estimation for perceptive mobile networks and WiFi. The geometrically-separated transmitter and receiver in communications are typically asynchronous at clock level. For a small base-station or WiFi, the number of antenna elements in an array is usually limited, which limits the resolution of estimating the angle-of-arrivals (AOAs) of multipath signals. In this paper, we employ cross-antenna cross-correlation (CACC) operation to resolve the asynchronous issue and use the CACC outputs to generate a multi-domain signal block that combines three-domain receive samples to efficiently increase the resolution of AOAs. The proposed scheme enables the direct use of uplink communication signals for radio sensing, without requiring any modifications on infrastructure or advanced hardware, such as a full-duplex transceiver. It also enables the estimation of more number of paths than the number of antennas, hence sensing in a small base-station or WiFi becomes possible.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Vehicular Technology Conference 2022-June 2022年 
    Employing cyclic prefixed OFDM (CP-OFDM) communication waveform for sensing has attracted extensive attention in vehicular integrated sensing and communications (ISAC). A unified sensing framework is developed recently, greatly extending the ranging capability of CP-OFDM sensing. However, a false target issue still remains unsolved. In this paper, we investigate and solve this issue. Specifically, we unveil that false targets are caused by periodic cyclic prefixes (CPs) in CP-OFDM waveform. We also derive the relation between the locations of false and true targets, and other features, e.g., strength, of false targets. Moreover, we develop an effective solution to removing false targets. Simulations are provided to confirm the validity of our analysis and the effectiveness of the proposed solution.
  • Mingfei Tong, Xiaojing Huang, J. Andrew Zhang
    2022 IEEE GLOBECOM Workshops, GC Wkshps 2022 - Proceedings 1670 - 1674 2022年 
    In this paper, we propose a frame-based decision directed successive interference cancellation to improve the detection performance of Faster-than-Nyquist (FTN) signaling. The main idea of this method is to directly decide all data symbols in a complete transmission frame after minimum-mean-square-error (MMSE) equalization and regenerate the noise-free signal with the decided symbols. The difference between the equalized and regenerated signals represents the residual inter-symbol interference (ISI) which depends on the bit-error-rate (BER) of the decision. After adding the normalized residual ISI to the decided symbols, the date symbols in the transmission frame are decided recursively, leading to a decision directed successive interference cancellation (DDSIC) scheme. The simulation results in both Gaussian and multipath fading channels demonstrate that our proposed method enables lower complexity and better performance FTN systems compared with existing symbol-by-symbol interference cancellation methods.
  • Hongyang Zhang, Xiaojing Huang, J. Andrew Zhang
    IEEE Transactions on Wireless Communications 20 11 7420 - 7430 2021年11月01日 
    In this paper, the emerging orthogonal time frequency space (OTFS) modulation is firstly restructured as a precoded orthogonal frequency division multiplexing (OFDM) system, so that the well-established frequency-domain approach can be applied to perform signal in fast fading channels. Then a frequency-domain minimum mean squared error (MMSE) equalizer for OTFS is introduced and its performance is analyzed based on the eigenvalue decomposition of the channel matrix. Inspired by the frequency-domain precoding structure, an adaptive transmission scheme with frequency-domain precoding matrix composed of the eigenvectors of the channel matrix is proposed to improve the system performance under MMSE equalization, and its optimized performance is derived with simple expression. Finally, considering two extreme channel conditions, the lower and upper bounds for the diversity performance of the adaptive transmission scheme are derived. Simulation results show that the proposed adaptive transmission achieves significantly better performance for short signal frames and can work well with imperfect channel state information (CSI). The derived performance bounds can serve as benchmarks for OTFS and other precoded OFDM systems.
  • Xiaojing Huang, Anh Tuyen Le, Y. Jay Guo
    IEEE Transactions on Wireless Communications 20 10 6467 - 6480 2021年10月01日 
    Joint analog and digital self-interference cancellation (SIC) is essential for enabling in-band full duplex (IBFD) communications. Analog least mean square (ALMS) loop is a promising low-complexity high-performance analog SIC technique with multi-tap adaptive filtering capability, but its properties on the tap coefficient variation have not been fully understood. In this paper, analysis based on higher-order statistics of the transmitted signal is performed to solve the problem of evaluating the variance of the ALMS loop's weighting coefficient error, which reveals two additional types of irreducible residual self-interference (SI) produced by an ALMS loop if it runs freely. The residual SI channel impulse response in digital baseband is also analysed and its unique properties are investigated. By introducing a simple track and hold control to the ALMS loop's tap coefficients, a joint analog and digital SIC scheme is proposed to stop the tap coefficient variation and achieve very low residual SI close to the IBFD receiver's noise floor. In a coordinated application scenario, the noise figure of the digital SIC algorithm is proved to be only 1.76 dB at most. Simulation results are provided to verify the theoretical analyses.
  • Linh Manh Hoang, J. Andrew Zhang, Diep N. Nguyen, Xiaojing Huang, Asanka Kekirigoda, Kin Ping Hui
    IEEE Transactions on Vehicular Technology 70 10 10489 - 10500 2021年10月01日 
    Effective suppression of inadvertent or deliberate jamming signals is crucial to ensure reliable wireless communication. However, as demonstrated in this paper, when the transmitted jamming signals are highly correlated, and especially when the correlation coefficient varies, nullifying the jamming signals can be challenging. Unlike existing techniques that often assume uncorrelated jamming signals or non-zero but constant correlation, we analyze the impact of the non-zero and varying correlations between transmitted jamming signals on the suppression of the jamming signals. Specifically, we observe that by varying the correlation coefficients between transmitted jamming signals, jammers can 'virtually change' the jamming channels hence their nullspace, even when these channels do not physically change. This makes most jamming suppression techniques that rely on steering receiving beams towards the nullspace of jamming channels no longer applicable. To tackle the problem, we develop techniques to effectively track the jamming nullspace and correspondingly update receiving beams. Monte Carlo simulations show that our proposed techniques can suppress/nullify jamming signals for all considered scenarios with non-zero and varying correlation coefficients amongst transmitted jamming signals.
  • Anh Tuyen Le, Xiaojing Huang, Y. Jay Guo
    IEEE Communications Letters 25 9 3075 - 3079 2021年09月 
    Full-duplex (FD) technology combined with dual-polarization (DP) multiple-input multiple-output (MIMO) systems is attractive to improve spectral efficiency and to enhance link capacity. Cancelling self-interference (SI) in such DPFD MIMO systems using beamforming techniques is very challenging due to a significant difference of the co-polarization and cross-polarization SI channels. In this letter, an analog adaptive filter structure is proposed to mitigate both co-polarization and cross-polarization SIs in DPFD MIMO systems. Stationary analysis is applied to evaluate the performance of the proposed structure. Simulation results show that about 45 dB to 55 dB of SI cancellation can be achieved regardless of the isolation differences between cross-polarization and co-polarization channels.
  • Muralikrishnan Srinivasan, Sarath Gopi, Sheetal Kalyani, Xiaojing Huang, Lajos Hanzo
    IEEE Transactions on Vehicular Technology 70 9 9345 - 9354 2021年09月 
    A high-rate yet low-cost air-to-ground (A2G) communication backbone is conceived for integrating the space and terrestrial network by harnessing the opportunistic assistance of the passenger planes or high altitude platforms (HAPs) as mobile base stations (BSs) and millimetre wave communication. The airliners act as the network-provider for the terrestrial users while relying on satellite backhaul. Three different beamforming techniques relying on a large-scale planar array are used for transmission by the airliner/HAP for achieving a high directional gain, hence minimizing the interference among the users. Furthermore, approximate spectral efficiency (SE) and area spectral efficiency (ASE) expressions are derived and quantified for diverse system parameters.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Jinhong Yuan
    IEEE Transactions on Communications 69 8 5502 - 5513 2021年08月 
    Frequency-hopping (FH) MIMO radar is recently introduced as an underlying system for realizing dual-function radar-communication (DFRC), increasing communication symbol rates to multiples of the radar pulse repetition frequency. As a newly conceived DFRC system, many realistic issues, such as channel estimation and synchronization, are not effectively solved yet. In this paper, we develop a multi-antenna receiver-based downlink communication scheme for the FH-MIMO DFRC, addressing the above issues in multi-path channels. By exploring the unique FH-MIMO radar waveform, we suppress both inter-antenna and inter-hop interference, and introduce minimal constraints on the radar waveform to facilitate DFRC. We then develop accurate estimation methods for timing offset and channel parameters. These methods are further employed to design reliable demodulation methods. We also derive performance bounds for the proposed estimation methods and embedded communications. Simulation results validate the efficacy of our receiving scheme, showing that the performance of estimators and data communications approaches analytical bounds.
  • Yijiang Nan, Xiaojing Huang, Xiang Gao, Y. Jay Guo
    IEEE Transactions on Geoscience and Remote Sensing 59 8 6771 - 6783 2021年08月 
    A novel 3-D time-domain terahertz (THz) imaging system based on piecewise constant Doppler (PCD) algorithm and step-frequency continuous-wave (SFCW) signaling is proposed in this article. First, the SFCW THz imaging system configuration and the Gaussian beam propagation model are introduced. Then, the conventional time-domain correlation imaging algorithm is reviewed, and the closed-form expression of its point spread function (PSF) is derived to quantify the range and lateral resolutions. To reduce the computational complexity, a 2-D recursive imaging process based on the plane approximation of the range surface is proposed, by which the original PCD algorithm is extended for 3-D imaging with 2-D aperture synthesis. The 3-D PCD imaging principle, implementation, and complexity analysis are discussed afterward. Finally, simulation and experimental results are provided to validate the theoretical analysis of the 3-D time-domain THz imaging and demonstrate the high quality of the proposed imaging algorithm at a low computational cost.
  • Ngoc Phuc Le, Le Chung Tran, Xiaojing Huang, Jinho Choi, Eryk Dutkiewicz, Son Lam Phung, Abdesselam Bouzerdoum
    IEEE Transactions on Vehicular Technology 70 7 6881 - 6897 2021年07月 
    In this paper, we propose a mixture gamma distribution based analytical framework for NOMA wireless systems over composite fading channels. We analyze the outage probability (OP), delay-limited throughput (TP) and effective capacity (EC) in uplink NOMA with imperfect successive interference cancellation (SIC) due to the presence of residual hardware impairments and delay constraints. A mixture gamma distribution is used to approximate the probability density functions of fading channels. Based on this, we obtain closed-form expressions in terms of Meijer-G functions for the OP, the TP and the EC. We also perform asymptotic analysis of these metrics to characterize system behaviors at the high signal-to-noise ratio regime. Moreover, upper-bounds for the EC is derived. Efficacy of NOMA over orthogonal multiple access is analytically examined. Unlike the existing works, our analytical expressions hold for NOMA systems with an arbitrary number of users per cluster over a wide range of channel models, including lognormal-Nakagami-m, KG, η-μ, Nakagami-q (Hoyt), κ-μ, Nakagami-n (Rician), Nakagami-m, and Rayleigh fading channels. This unified analysis facilitates evaluations of impacts of the residual interference, the power allocation among users, the delay quality-of-service exponent as well as the shadowing and small-scale fading parameters on the performance metrics. Simulation results are provided to validate theoretical analysis.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Vehicular Technology 70 7 7267 - 7271 2021年07月 
    Frequency estimation is a fundamental problem in many areas. The well-known A&M and its variant estimators have established an estimation framework by iteratively interpolating the discrete Fourier transform (DFT) coefficients. In general, those estimators require two DFT interpolations per iteration, have uneven initial estimation performance against frequencies, and are incompetent for small sample numbers due to low-order approximations involved. Exploiting the iterative estimation framework of A&M, we unprecedentedly introduce the Padé approximation to frequency estimation, unveil some features about the updating function used for refining the estimation in each iteration, and develop a simple closed-form solution to solving the residual estimation error. Extensive simulation results are provided, validating the superiority of the new estimator over the state-the-art estimators in wide ranges of key parameters.
  • Andrew Zhang, Md Lushanur Rahman, Xiaojing Huang, Yingjie Jay Guo, Shanzhi Chen, Robert W. Heath
    IEEE Vehicular Technology Magazine 16 2 20 - 30 2021年06月 
    Joint communication and radar/radio sensing (JCAS), also known as dual-function radar communications, enables the integration of communication and radio sensing into one system, sharing a single transmitted signal. The perceptive mobile network (PMN) is a natural evolution of JCAS from simple point-to-point links to a mobile/cellular network with integrated radio-sensing capability. In this article, we present a system architecture that unifies three types of sensing, investigate the required modifications to existing mobile networks, and exemplify the signals applicable to sensing. We also provide a review to stimulate research problems and potential solutions, including mutual information, joint design and optimization for waveform and antenna grouping, clutter suppression, sensing parameter estimation and pattern recognition, and networked sensing under the cellular topology.
  • Xiaojing Huang, Anh Tuyen Le, Y. Jay Guo
    IEEE Transactions on Wireless Communications 20 6 3760 - 3769 2021年06月 
    The performance of transmit beamforming for both optimized precoding and self-interference cancellation (SIC) in full duplex multiple input multiple output (MIMO) transceivers is analysed in this paper. With sub-space dimension larger than that of the null-space of the self-interference channels, the precoding error is reduced but the interference suppression ratio (ISR) is degraded, resulting in a trade-off between multibeam communication and MIMO SIC. An analytical approach for the ISR evaluation is proposed assuming known eigenvalue distribution of the self-interference channels, and a closed-form ISR expression is derived after applying a uniform distribution approximation. The ISR and precoding error trade-off curves are also formulated. Joint SIC by transmit beamforming and beam-based analog adaptive filters over both propagation and analog domains is proposed to achieve better SIC performance and enable more flexible receive antenna selection. Simulation results verify the theoretical analyses.
  • Penglu Liu, Yong Li, Wei Cheng, Xiang Gao, Xiaojing Huang
    IEEE Transactions on Vehicular Technology 70 5 4419 - 4434 2021年05月 
    In this paper, we propose a downlink intelligent reflecting surface (IRS) aided non-orthogonal multiple access (NOMA) for millimeter-wave (mmWave) massive MIMO with lens antenna array, i.e., IRS-aided mmWave beamspace NOMA, where the single-antenna users without direct-link but connected to the base station (BS) with the aid of the IRS are grouped as one NOMA group. Considering the power leakage problem in beamspace channel and the per-antenna power constraint, we propose two multi-beam selection strategies for the BS-IRS link under two channel models, i.e., 2-dimension (2D) channel model and 3-dimension (3D) channel model, respectively, where two corresponding RF chain configuration strategies are designed, respectively. Then, we formulate and solve the optimization problem for maximizing the weighted sum rate by jointly optimizing the active beamforming at the BS and the passive beamforming at the IRS, where we propose the alternating optimization (AO) method to solve the above joint optimization problem. Especially, different from the stochastic method, based on the beam-splitting technique, we propose the method to initialize the feasible solution for the proposed AO method, where the conditional transmit power minimization problem is formulated and solved. Through simulations, the weighted sum rate performance of the proposed IRS-aided mmWave beamspace NOMA is verified.
  • Ngoc Phuc Le, Le Chung Tran, Xiaojing Huang, Eryk Dutkiewicz, Christian Ritz, Son Lam Phung, Abdesselam Bouzerdoum, Daniel Franklin, Lajos Hanzo
    IEEE Transactions on Vehicular Technology 70 2 1632 - 1647 2021年02月 
    In this paper, we propose a wireless localization system based on energy-harvesting aided unmanned aerial vehicles (UAV). Our proposed system consists of a ground station (GS), a UAV, and multiple users located on the ground, in which both the ground station and all the ground users (GUs) want to know the locations of the ground users. To this end, the UAV first harvests energy from the GS, and then broadcasts signals to the GUs for localization. Each GU will estimate its location, and then transmits data, including its location information, to the GS with the help of the UAV. The links between nodes experience both large-scale lognormal shadowing and small-scale Nakagami-m fading. We first derive the Cramer-Rao lower bound (CRLB) under spatially correlated shadowing for localization performance evaluation. Next, we analyze the system throughput under delay-limited and delay-tolerant transmission modes. To derive exact closed-form expressions as well as high signal-to-noise ratio (SNR) approximations of the performance metrics, we consider a mixture gamma distribution approximation for the probability density functions (PDF) of the composite fading channels. We evaluate the impact of several key system parameters such as the number of waypoints and the altitude of the UAV, correlated shadowing and energy-harvesting time both on the localization performance and on the achievable throughput. Simulations are provided to validate the theoretical analysis.
  • Kai Wu, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Robert W. Heath
    IEEE Transactions on Communications 69 2 1244 - 1258 2021年02月 
    Frequency-hopping (FH) MIMO radar-based dual-function radar communication (FH-MIMO DFRC) enables communication symbol rate to exceed radar pulse repetition frequency, which requires accurate estimations of timing offset and channel parameters. The estimations, however, are challenging due to unknown, fast-changing hopping frequencies and the multiplicative coupling between timing offset and channel parameters. In this article, we develop accurate methods for a single-antenna communication receiver to estimate timing offset and channel for FH-MIMO DFRC. First, we design a novel FH-MIMO radar waveform, which enables a communication receiver to estimate the hopping frequency sequence (HFS) used by radar, instead of acquiring it from radar. Importantly, the novel waveform incurs no degradation to radar ranging performance. Then, via capturing distinct HFS features, we develop two estimators for timing offset and derive mean squared error lower bound of each estimator. Using the bounds, we design an HFS that renders both estimators applicable. Furthermore, we develop an accurate channel estimation method, reusing the single hop for timing offset estimation. Validated by simulations, the accurate channel estimates attained by the proposed methods enable the communication performance of DFRC to approach that achieved based on perfect timing and ideal knowledge of channel.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Y. Jay Guo, Lajos Hanzo
    IEEE Wireless Communications 28 1 12 - 18 2021年02月 
    In-band full duplex (IBFD) radio represents one of the key technologies for future wireless communication and radar applications. A major challenge of this technology is to mitigate the strong self-interfer-ence (SI) so that the residual SI level falls below the receiver's noise floor. Radio frequency (RF) self-inter-ference cancellation (SIC) is essential for preventing an IBFD receiver from becoming saturated by the SI. We commence with an in-depth review of the promising analog least mean square (ALMS) adaptive filtering architecture, conceived for RF SIC in the IBFD radio RF front-end. The cancellation circuits employing this architecture can be implemented purely by analog components without any involvement of more power-thirsty digital signal processing. The behaviors, performance, and implementation of the ALMS loop are presented. Finally, their applications in various IBFD radios are discussed, and future research directions are provided.
  • Zhitong Ni, J. Andrew Zhang, Xiaojing Huang, Kai Yang, Jinhong Yuan
    IEEE Transactions on Signal Processing 69 1287 - 1300 2021年 
    Perceptive mobile network (PMN) is a recently proposed next-generation network that integrates radar sensing into communications. One major challenge for realizing sensing in PMNs is how to deal with spatially-separated asynchronous transceivers. The asynchrony between sensing receiver and transmitter will cause both timing offsets (TOs) and carrier frequency offsets (CFOs) and lead to degraded sensing accuracy in both ranging and velocity measurements. In this paper, we propose an uplink sensing scheme for PMNs with asynchronous transceivers, targeting at resolving the sensing ambiguity and improving the sensing accuracy. We first adopt a cross-antenna cross-correlation (CACC) operation to remove the sensing ambiguity associated with both TOs and CFOs. Without sensing ambiguity, both actual propagation delay and actual Doppler frequency of multiple targets can be obtained using CACC outputs. To exploit the redundancy of the CACC outputs and reduce the complexity, we then propose a novel mirrored-MUSIC algorithm, which halves the number of unknown parameters to be estimated, to obtain actual values of delays and Doppler frequencies. Finally, we propose a high-resolution angles-of-arrival (AoAs) estimation algorithm, which jointly processes all measurements from spatial, temporal, and frequency domains. The proposed AoAs estimation algorithm can achieve significantly higher estimation accuracy than that of using samples from the spatial domain only. We also derive the theoretical mean-square-error of the proposed algorithms. Numerical results are provided and validate the effectiveness of the proposed scheme.
  • Hongyang Zhang, Xiaojing Huang, J. Andrew Zhang
    IEEE Vehicular Technology Conference 2021-September 2021年 
    Achieving better performance in high mobility scenarios has become an emerging topic for next generation wireless communications. Compared with traditional modulation techniques, the recently proposed orthogonal time frequency space (OTFS) shows outstanding performance over fast fading channels. In this paper, the OTFS system is first represented in the form of precoded orthogonal frequency division multiplexing (OFDM), enabling traditional estimation and equalization techniques to work under fast fading channels. Then, a novel frequency-domain pilot-aided channel estimation scheme is proposed to obtain the channel state information at the receiver. Simulation results show that the new channel estimation scheme works efficiently in different channel scenarios. Meanwhile, the overhead of the proposed scheme is also lower than those of the current popular schemes.
  • Xiang Gao, Jia Du, Ting Zhang, Hao Zhang, Xiaojing Huang, Yingjie Jay Guo
    2021 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications, IMWS-AMP 2021 142 - 144 2021年 
    This paper presents the terahertz communication demonstration by using a quasi-optically coupled high-T_{\mathrm{c } } superconducting (HTS) Josephson receiver. The receiver consists of a broadband HTS Josephson-junction mixer integrated with a cryogenic low noise amplifier inside a miniature cryocooler. The noise and conversion properties of the broadband HTS mixer versus the bias current and local oscillator (LO) power, are thoroughly investigated for different operating temperatures and frequencies. Based on such HTS receiver frontend, a 320-GHz wireless communication link was established at the UTS laboratory and demonstrated by using the QPSK and 16QAM modulations, respectively.
  • Md Lushanur Rahman, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Zhiping Lu
    IET Communications 14 22 3977 - 3988 2020年12月27日 
    Radio sensing can be integrated with communication in what the authors call future perceptive mobile networks. Due to the complicated signal structure, it is challenging to estimate sensing parameters such as delay, angle of arrival, and Doppler when joint communication and radar/radio sensing is applied in perceptive mobile networks. Radio sensing with signals compatible with a fifth-generation (5G) new radio standard using one-dimension (1D) to 3D compressive sensing (CS) techniques under 5G channel conditions is studied. In the case of 1D–3D CS techniques, they formulate the parameter estimation as a sparse signal recovery problem. These algorithms demonstrate respective advantages, but also show shortcomings in dealing with clustered channels. To effectively exploit the cluster structure in multipath channels, they also propose a 2D cluster Kronecker CS algorithm for significantly improved sensing parameter estimation via introducing a prior probability distribution. Simulation results are provided and they focus the respective advantages and disadvantages of these techniques that validate the effectiveness of the proposed algorithms.
  • Qingqing Cheng, Zhipeng Lin, J. Andrew Zhang, Diep Nguyen, Xiaojing Huang, Asanka Kekirigoda, Kin Ping Hui
    2020 14th International Conference on Signal Processing and Communication Systems, ICSPCS 2020 - Proceedings 2020年12月14日 
    Being spectrum-efficient and robust to adversarial interference caused by jammers are critical to tactical wireless systems. Leveraging multiple-input multiple-output (MIMO) techniques, this paper investigates the realization of spectrum-efficient multi-user MIMO communications in the presence of high-power jammers. Unlike most existing work that only exploits the MIMO degree of freedom to nullify the jamming signal, we also aim to improve the spectral efficiency of the system with the MIMO spatial multiplexing capability. To that end, we first design a combiner at the receiver spanning the null space of the jamming channels, which can completely remove the jamming signals and optimize the communication reception. We further propose two methods for the design of precoders at the transmitter to mitigate multi-user interference. Simulation results are presented to verify the effectiveness of the proposed schemes in radio-frequency contested environments.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Christian Ritz, Eryk Dutkiewicz, Abdesselam Bouzerdoum, Daniel Franklin
    2020 14th International Conference on Signal Processing and Communication Systems, ICSPCS 2020 - Proceedings 2020年12月14日 
    Unmanned aerial vehicles (UAVs) are considered as a great solution for a flexible and rapid deployment of wireless sensor networks (WSN) in emergency scenarios. Hybrid time-of-arrival (TOA) and angle-of-arrival (AOA) localization is widely used to estimate agents' positions in WSN. Conventional TOA/AOA localization methods normally require both elevation and azimuth AOA estimations to estimate agents' positions, leading to complicated L-shape antenna arrays and power-thirsty two-dimensional signal processing at the agents. We propose a hybrid TOA/1AOA localization approach which only requires elevation AOA estimations to combine with TOA measurements. A weighted least square algorithm is proposed to solve the non-linear problem. The performance of the proposed method is compared with that of the conventional approach under various scenarios. Simulation results show that, by adjusting different parameters such as transmit power, signal bandwidth, and the number of anchors, the proposed method outperforms the conventional counterpart while significantly reduces the complexity of the agents.
  • J. Andrew Zhang, Linh Hoang, Diep Nguyen, Xiaojing Huang, Asanka Kekirigoda, Kin Ping Hui
    2020 14th International Conference on Signal Processing and Communication Systems, ICSPCS 2020 - Proceedings 2020年12月14日 
    In this paper, we present a technique for realizing reliable multi-user MIMO communications in the presence of interference in time-varying channels. The null space of interfering channels is estimated and exploited for interference mitigation. We first introduce an improved superframe structure to enable frequent tracking of user channels and the null space of interfering channels. The different natures of the received user signals and interference require different processing methods. We improve and compare several adaptive equalizers to deal with time-varying user channels, and propose to use a subspace-based tracking algorithm to handle time-varying interfering channels. We simulate the proposed tracking algorithms in various settings, including when the interference signals are correlated. Simulation results are provided and validate the effectiveness of the proposed technique.
  • Qiaolin Shi, Nan Wu, Hua Wang, Diep N. Nguyen, Xiaojing Huang
    Proceedings - IEEE Global Communications Conference, GLOBECOM 2020-January 2020年12月 
    This paper proposes a low-complexity joint phase noise (PHN) estimation and decoding algorithm for orthogonal frequency division multiplexing relying on index modulation (OFDM-IM) systems. A factor graph (FG) is constructed based on the truncated discrete cosine transform (DCT) expansion model for the variation of PHN. In order to explicitly take into account the structured and sparse a priori information of the frequency-domain symbols provided by the soft-in soft-out (SISO) decoder, the generalized approximate message passing (GAMP) algorithm is employed. Furthermore, to solve the unknown and nonlinear transform matrix problem introduced by the PHN, the mean-field (MF) method is invoked at the observation nodes on the FG. Monte Carlo simulations show the superiority of the proposed algorithm over the existing variational inference (VI) and extended Kalman filter (EKF) methods in terms of their bit error rate (BER) performance and complexity. In addition, we demonstrate that the OFDM-IM scheme outperforms its conventional OFDM counterpart in the presence of PHN.
  • Hongyang Zhang, Xiaojing Huang, J. Andrew Zhang, Y. Jay Guo
    IEEE Vehicular Technology Conference 2020-November 2020年11月 
    The sixth generation (6G) mobile systems will enable high mobility applications in both space and ground based networks. In this paper, we investigate low-complexity equalization and adaptive transmission schemes to combat fast fading channels due to high mobility. We first derive signal and channel models in fast fading channels, which allow low complexity minimum mean square error (MMSE) equalization. We then analyze the output signal-to-noise ratio (SNR) using eigenvalue decomposition for a generalized modulation representation. Assuming the channel state information (CSI) is known at the transmitter, we propose an adaptive transmission technique which utilizes the CSI to precode data symbols in order to improve the output SNR at the receiver. Simulation results show that the adaptive transmission scheme effectively improves the MMSE equalization performance in non-line-of-sight channels especially when the transmission signal frame is short.
  • Yijiang Nan, Xiaojing Huang, Yingjie Jay Guo
    IEEE Transactions on Aerospace and Electronic Systems 56 5 3613 - 3631 2020年10月 
    The piecewise constant Doppler (PCD) algorithm is a novel radar imaging process recently proposed for the generalized continuouswave synthetic aperture radar (GCW-SAR). This article presents a detailed theoretical analysis on the PCD algorithm's performance and proposes a further complexity-reduced PCD algorithm with motion compensation (MOCO) suitable for practical applications. First, the difference between conventional SAR imaging and PCD imaging, i.e., the zeroth-order versus the first-order slant range approximation, is revealed. Exact ambiguity function expressions of the PCD imaging in range and azimuth directions, respectively, are then derived. An error function of the PCD imaging as compared with the ideal matched filtering method is further defined and shown to be a function of an image quality factor, which can be used to quantify the PCD imaging performance. Finally, a faster and more flexible imaging process, called decimated PCD algorithm, is proposed, by which the image azimuth spacing can be easily extended, and hence, the computational complexity can be significantly reduced. The decimated PCD implementation incorporated with the MOCO is developed for practical GCW-SAR applications, and its imaging error lower-bounded by the PCD imaging error function is analyzed accordingly. Simulation and experimental results validate the theoretical analysis of the PCD imaging and show that the decimated PCD algorithm can achieve a high imaging quality at low cost.
  • Chuan Qin, J. Andrew Zhang, Xiaojing Huang, Kai Wu, Y. Jay Guo
    IEEE Transactions on Wireless Communications 19 10 6425 - 6439 2020年10月 
    Angle-of-Arrival (AoA) estimation is a challenging problem for analog antenna arrays. Typical schemes use time-consuming beam scanning, and the resolution is limited to the scanning beam width. In this paper, we propose a virtual-subarray based AoA (ViSA) estimation scheme, which divides an analog array into two virtual subarrays and exploits phase difference between one pair of measurements for AoA estimation. The basic ViSA algorithm can obtain a direct AoA estimate from every two temporal measurements. We propose different subarray constructions which can lead to different accuracy of estimation. We provide closed-form expressions for the statistics of the estimation error. Based on the basic ViSA estimator, we develop two methods to combine multiple pairs of measurements, when they are obtained via sequential and multi-resolution scanning, respectively. Near-optimal estimators are derived for both methods, employing the maximum likelihood principle. Novel techniques are also proposed to address the typical phase ambiguity problem due to the periodic phase function. Simulation results demonstrate that the proposed scheme significantly outperforms existing ones.
  • Yuyue Luo, J. Andrew Zhang, Xiaojing Huang, Wei Ni, Jin Pan
    IEEE Transactions on Vehicular Technology 69 10 11000 - 11013 2020年10月 
    Multibeam technology enables the use of two or more subbeams for joint communication and radio sensing, to meet different requirements of beamwidth and pointing directions. Generating and optimizing multibeam subject to the requirements is critical and challenging, particularly for systems using analog arrays. This paper develops optimal solutions to a range of multibeam design problems, where both communication and sensing are considered. We first study the optimal combination of two pre-generated subbeams, and their beamforming vectors, using a combining phase coefficient. Closed-form optimal solutions are derived to the constrained optimization problems, where the received signal powers for communication and the beamforming waveforms are alternatively used as the objective and constraint functions. We also develop global optimization methods which directly find optimal solutions for a single beamforming vector. By converting the original intractable complex NP-hard global optimization problems to real quadratically constrained quadratic programs, near-optimal solutions are obtained using semidefinite relaxation techniques. Extensive simulations validate the effectiveness of the proposed constrained multibeam generation and optimization methods.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Christian Ritz, Eryk Dutkiewicz, Son Lam Phung, Abdesselam Bouzerdoum, Daniel Franklin
    Sensors (Switzerland) 20 14 1 - 16 2020年07月02日 
    Source positioning using hybrid angle-of-arrival (AOA) estimation and received signal strength indicator (RSSI) is attractive because no synchronization is required among unknown nodes and anchors. Conventionally, hybrid AOA/RSSI localization combines the same number of these measurements to estimate the agents’ locations. However, since AOA estimation requires anchors to be equipped with large antenna arrays and complicated signal processing, this conventional combination makes the wireless sensor network (WSN) complicated. This paper proposes an unbalanced integration of the two measurements, called 1AOA/nRSSI, to simplify the WSN. Instead of using many anchors with large antenna arrays, the proposed method only requires one master anchor to provide one AOA estimation, while other anchors are simple single-antenna transceivers. By simply transforming the 1AOA/1RSSI information into two corresponding virtual anchors, the problem of integrating one AOA and N RSSI measurements is solved using the least square and subspace methods. The solutions are then evaluated to characterize the impact of angular and distance measurement errors. Simulation results show that the proposed network achieves the same level of precision as in a fully hybrid nAOA/nRSSI network with a slightly higher number of simple anchors.
  • Hao Zhang, Xiaojing Huang, J. Andrew Zhang, Y. Jay Guo
    IEEE Transactions on Circuits and Systems I: Regular Papers 67 7 2372 - 2382 2020年07月 
    Analog-to-digital and digital-to-analog conversion devices for signals with very large bandwidth are not always available due to technical or cost issues. This limits the realization of very high data-rate digital communication systems. In this paper, we propose a dual pulse shaping (DPS) transmission scheme, which can achieve full Nyquist rate transmission with only a half of the sampling rate for each of the two data streams. Two classes of ideal complementary Nyquist pulses are formulated assuming raised-cosine (RC) pulse shaping. The condition for cross-symbol interference (CSI) free transmission is derived and validated for the proposed pulses. Structures of the DPS transmitter and receiver are described and low-complexity equalization techniques tailored to DPS are proposed. With DPS, a millimeter wave system with commercially available and affordable data conversion devices is exemplified for achieving high-speed low-cost wireless communications. Simulation results with two sets of practical dual spectral shaping pulses are provided. The results verify the effectiveness of the proposed scheme, with comparison to the benchmark conventional Nyquist pulse shaping system.
  • Md Lushanur Rahman, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Robert W. Heath
    IEEE Transactions on Aerospace and Electronic Systems 56 3 1926 - 1941 2020年06月 
    In this paper, we develop a framework for a novel perceptive mobile/cellular network that integrates radar sensing function into the mobile communication network. We propose a unified system platform that enables downlink and uplink sensing, sharing the same transmitted signals with communications. We aim to tackle the fundamental sensing parameter estimation problem in perceptive mobile networks, by addressing two key challenges associated with sophisticated mobile signals and rich multipath in mobile networks. To extract sensing parameters from orthogonal frequency division multiple access and spatial division multiple access communication signals, we propose two approaches to formulate it to problems that can be solved by compressive sensing techniques. Most sensing algorithms have limits on the number of multipath signals for their inputs. To reduce the multipath signals, as well as removing unwanted clutter signals, we propose a background subtraction method based on simple recursive computation, and provide a closed-form expression for performance characterization. The effectiveness of these methods is validated in simulations.
  • Zhitong Ni, J. Andrew Zhang, Xiaojing Huang, Kai Yang, Fei Gao
    2020 IEEE International Conference on Communications Workshops, ICC Workshops 2020 - Proceedings 2020年06月 
    Joint communication and radar sensing (JCAS) integrates communication and radar sensing into one system, sharing one transmitted signal. In this paper, we study a JCAS system that uses a dedicated low-cost single-antenna receiver for sensing. We provide sensing parameter estimation algorithms for the JCAS system, and investigate the optimization of the precoding matrix to balance communication and sensing performance. A MUSIC-based estimation approach is proposed to obtain time delays and angle-of-arrivals of targets. A weighted signal optimization to balance between communication and sensing is then proposed. Numerical results are provided and verify the effectiveness of the proposed scheme.
  • Kai Wu, Y. Jay Guo, Xiaojing Huang, Robert W. Heath
    2020 IEEE International Conference on Communications Workshops, ICC Workshops 2020 - Proceedings 2020年06月 
    Dual-function radar communications (DFRC) is proposed recently to embed information into radar waveform, and hence performs data communications by sharing radar apertures and frequency resources. Exploiting a frequency-hopping (FH) MIMO radar, DFRC can achieve the symbol rate that is larger than the radar pulse frequency. However, this requires an accurate channel estimate, which is challenging to achieve due to the radar-prioritized transmission and the fast-changing FH waveform. In this paper, we propose an accurate channel estimation method for the DFRC based on FH-MIMO radars. We design a new FH-MIMO radar waveform which incurs no change to the ranging performance of the radar. The new waveform also enables a communication receiver to estimate the channel without knowing the pairing between hopping frequencies and antennas. We also develop a new angle estimation method at a single-antenna communication receiver using as few as one symbol, i.e., a single hop. Simulations are provided to validate the efficacy of the proposed channel estimation method. Specifically, the symbol error rate achieved based on the estimated channel approaches that based on the ideal channel.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Wireless Communications 19 4 2460 - 2471 2020年04月 
    Self-interference (SI) cancellation for full-duplex (FD) multiple input multiple output (MIMO) systems is challenging due to both hardware and signal processing complexity. In this paper, a beam-based adaptive filter structure with analog least mean square (ALMS) loops is proposed to significantly reduce the complexity of SI cancellation for FD MIMO systems. With this structure, the number of adaptive filters required for SI cancellation scales linearly with the number of transmit beams rather than quadratically with the number of antennas. Furthermore, to avoid additional transmit chains used to up-convert the beam signals to generate reference signals for the ALMS loops, a novel method is proposed to select the optimized reference signals from all transmitted signals. In addition, our stationary analysis shows that the proposed structure for FD MIMO systems outperforms the ALMS loop employed for an FD single input single output system. Simulations are conducted to confirm the theoretical analyses.
  • Chuan Qin, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications Letters 9 2 194 - 197 2020年02月 
    Angle-of-arrival (AoA) estimation is a challenging problem for analog antenna arrays. Typical algorithms are based on beam scanning which can be time-consuming. In this letter, we propose a virtual-subarray based recursive AoA estimation scheme that can get an AoA estimate from every two measurements and recursively improve the performance by updating beamforming weights with soft probability-based information. Simulation results validate the high efficiency of the proposed scheme, demonstrating its superiority for initial AoA estimation in analog arrays.
  • Weijie Yuan, Nan Wu, Andrew Zhang, Xiaojing Huang, Yonghui Li, Lajos Hanzo
    IEEE Transactions on Wireless Communications 19 2 915 - 928 2020年02月 
    The sparse code multiple access (SCMA) is a promising candidate for bandwidth-efficient next generation wireless communications, since it can support more users than the number of resource elements. On the same note, faster-than-Nyquist (FTN) signaling can also be used to improve the spectral efficiency. Hence in this paper, we consider a combined uplink FTN-SCMA system in which the data symbols corresponding to a user are further packed using FTN signaling. As a result, a higher spectral efficiency is achieved at the cost of introducing intentional inter-symbol interference (ISI). To perform joint channel estimation and detection, we design a low complexity iterative receiver based on the factor graph framework. In addition, to reduce the signaling overhead and transmission latency of our SCMA system, we intrinsically amalgamate it with grant-free scheme. Consequently, the active and inactive users should be distinguished. To address this problem, we extend the aforementioned receiver and develop a new algorithm for jointly estimating the channel state information, detecting the user activity and for performs data detection. In order to further reduce the complexity, an energy minimization based approximation is employed for restricting the user state to Gaussian. Finally, a hybrid message passing algorithm is conceived. Our Simulation results show that the FTN-SCMA system relying on the proposed receiver design has a higher throughput than conventional SCMA scheme at a negligible performance loss.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Yingjie Jay Guo
    Sensors (Switzerland) 20 1 2020年01月01日 
    Self-interference (SI) is the key issue that prevents in-band full-duplex (IBFD) communications from being practical. Analog multi-tap adaptive filter is an efficient structure to cancel SI since it can capture the nonlinear components and noise in the transmitted signal. Analog least mean square (ALMS) loop is a simple adaptive filter that can be implemented by purely analog means to sufficiently mitigate SI. Comprehensive analyses on the behaviors of the ALMS loop have been published in the literature. This paper proposes a practical structure and presents an implementation of the ALMS loop. By employing off-the-shelf components, a prototype of the ALMS loop including two taps is implemented for an IBFD system operating at the carrier frequency of 2.4 GHz. The prototype is firstly evaluated in a single carrier signaling IBFD system with 20 MHz and 50 MHz bandwidths, respectively. Measured results show that the ALMS loop can provide 39 dB and 33 dB of SI cancellation in the radio frequency domain for the two bandwidths, respectively. Furthermore, the impact of the roll-off factor of the pulse shaping filter on the SI cancellation level provided by the prototype is presented. Finally, the experiment with multicarrier signaling shows that the performance of the ALMS loop is the same as that in the single carrier system. These experimental results validate the theoretical analyses presented in our previous publications on the ALMS loop behaviors.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Geoscience and Remote Sensing 58 1 680 - 690 2020年01月 
    A novel generalized continuous-wave synthetic aperture radar (GCW-SAR) based on deramp-on-receive operating in millimeter-wave frequency is proposed in this article. With deramp-on-receive, the receiver sampling rate is drastically reduced, and the downsampled 1-D raw data can be obtained from the received beat signal. Further adopting piecewise constant Doppler (PCD) imaging in the digital domain, a GCW-SAR image can be easily reconstructed by using the existing frequency-modulated continuous-wave (FMCW) radar system. The effects of deramp-on-receive in PCD imaging are analyzed accordingly. The short wavelength of the millimeter-wave carrier used in the proposed GCW-SAR enables high azimuth resolution as well as a short synthetic aperture, which, in turn, significantly reduces the imaging computational complexity. Simulation and experimental results confirm the advantages of the proposed GCW-SAR.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Y. Jay Guo
    2019 29th International Telecommunication Networks and Applications Conference, ITNAC 2019 2019年11月 
    Analog least mean square (ALMS) loop is a simple and efficient adaptive filter to cancel self-interference (SI) in inband full-duplex (IBFD) radios. This paper proposes a practical structure and presents an implementation of the ALMS loop. By employing off-the-shelf components, a prototype of the ALMS loop including two taps is implemented. The prototype is evaluated in IBFD systems which have 20 MHz and 50 MHz bandwidths, respectively, with the carrier frequency of 2.4 GHz. The performance of the prototype with different roll-off factors of the transmit pulse shaping filter is also examined. Experimental results show that the ALMS loop can provide 39 dB and 33 dB of SI cancellation for the two systems, respectively. Furthermore, when the roll-off factor of the pulse shaping filter changes, different levels of cancellation given by the prototype are also demonstrated accordingly. These experimental results validate the theoretical analyses presented in our previous publications on the ALMS loop behavior.
  • Asanka Kekirigoda, Kin Ping Hui, Qingqing Cheng, Zhipeng Lin, J. Andrew Zhang, Diep N. Nguyen, Xiaojing Huang
    Proceedings - IEEE Military Communications Conference MILCOM 2019-November 2019年11月 
    Survivability of wireless communications segments in tactical military networks is an enormous challenge in the present and future defence forces, especially as these networks usually operate in radio frequency (RF) contested environments. Therefore, it is necessary to develop techniques to provide effective and efficient communication in RF contested environments. Massive multiple-input-multiple-output (MIMO) techniques use a large number of antennas enabling higher degrees of freedom that can improve communications network's survivability and efficiency compared to conventional MIMO or single antenna systems. This paper presents a novel massive MIMO communications system which enhances the throughput of the network, reduces the bit-error-rate and mitigates the interference from high powered jammers. Simulation results in contested environments verify the effectiveness of this system.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Yingjie Jay Guo
    IEEE Transactions on Vehicular Technology 68 10 9848 - 9860 2019年10月 
    Analog least mean square (ALMS) loop is a promising structure for self-interference (SI) mitigation in full-duplex radios due to its simplicity and adaptive capability. However, being constructed from in-phase/quadrature (I/Q) demodulators and modulators to process complex signals, the ALMS loop may face I/Q imbalance problems. Thus, in this paper, the effects of frequency-independent I/Q imbalance in the ALMS loop are investigated. It is revealed that I/Q imbalance affects the loop gain and the level of SI cancellation. The loop gain can be easily compensated by adjusting the gain at other stages of the ALMS loop. Meanwhile, the degradation on cancellation performance is proved to be insignificant even under severe conditions of I/Q imbalance. In addition, an upper bound of the degradation factor is derived to provide an essential reference for the system design. Simulations are conducted to confirm the theoretical analyses.
  • Xiaojing Huang, J. Andrew Zhang, Ren Ping Liu, Y. Jay Guo, Lajos Hanzo
    IEEE Vehicular Technology Magazine 14 3 84 - 91 2019年09月 
    As demand for wireless connectivity increases, communication technology is moving toward integrating terrestrial networks with space networks. Creating this integrated space and terrestrial network (ISTN) is critically important for industries such as logistics, mining, agriculture, fisheries, and defense. However, a number of significant technological challenges must be overcome for ISTN through low-cost airborne platforms and high-data-rate backbone links.
  • Xiaojing Huang, Hao Zhang, Jian A. Zhang, Y. Jay Guo, Rui Liang Song, Xiao Fan Xu, Chun Ting Wang, Zhou Lu, Wei Wu
    IEEE Vehicular Technology Conference 2019-September 2019年09月 
    The concept of complementary Nyquist pulse is introduced in this paper. Making use of a half rate Nyquist pulse and its complementary one, a dual pulse shaping transmission scheme is proposed, which achieves full Nyquist rate transmission with only a half of the sampling rate required by conventional Nyquist pulse shaping. This is essential for realizing high-speed digital communication systems with available and affordable data conversion devices. The condition for cross-symbol interference free transmission with the proposed dual pulse shaping is proved in theory, and two classes of ideal complementary Nyquist pulses are formulated assuming raised-cosine pulse shaping. Simulation results are also presented to demonstrate the improved spectral efficiency with dual pulse shaping and compare other system performance against conventional Nyquist pulse shaping.
  • Chuan Qin, J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Vehicular Technology Conference 2019-September 2019年09月 
    Angle-of-arrival (AoA) estimation is a challenging problem for analog antenna arrays. Typical algorithms use beam scanning and sweeping, which can be time-consuming, and the resolution is limited to the scanning step. In this paper, we propose a virtual-subarray based AoA estimation scheme, which divides an analog array into two virtual subarrays and can obtain a direct AoA estimate from every two temporal measurements. We propose different subarray constructions which lead to different range and accuracy of estimation. We provide detailed beamforming vector designs for these constructions and provide a performance lower bound for the estimator. We also present how to apply the estimator to AoA acquisition and tracking. Simulation results demonstrate that the proposed scheme significantly outperforms existing ones when the signal-to-noise ratio is not very low.
  • Hang Li, Thomas Q. Wang, Xiaojing Huang, J. Andrew Zhang
    IEEE Vehicular Technology Conference 2019-September 2019年09月 
    With balanced system performance, implementation complexity and hardware cost, hybrid antenna array is regarded as an enabling technology for massive multiple-input and multiple-output communication systems in millimeter wave (mmWave) frequencies. Angle-of-arrival (AoA) estimation using a localized hybrid array faces the challenges of the phase ambiguity problem due to its localized nature of array structure and susceptibility to noises. This paper discusses AoA estimation in an mmWave system employing dual-polarized antennas. We propose an enhanced AoA estimation algorithm using a localized hybrid dual-polarized array for a polarized mmWave signal. First, the use of dual-polarized arrays effectively strengthens the calibration of differential signals and resulting signal-to-noise ratio with coherent polarization combining, leading to an enhanced estimate of the phase offset between adjacent subarrays. Second, given the phase offset, an initial AoA estimate can be obtained, which is used to update the phase offset. By employing the updated one, the AoA is re- estimated with improved accuracy. The closed-form mean square error (MSE) lower bounds of AoA estimation are derived and compared with simulated MSEs. The simulation results show that the proposed algorithm in combination with hybrid dual- polarized arrays significantly improves the estimation accuracy compared with the state of the art.
  • Hao Zhang, Xiaojing Huang, Ting Zhang, Jian A. Zhang, Y. Jay Guo
    Proceedings - 2019 19th International Symposium on Communications and Information Technologies, ISCIT 2019 260 - 264 2019年09月 
    A high-speed wideband terahertz (THz) communication system with low-complexity and real-time digital signal processing (DSP) is presented in this paper. The architectures of baseband platform, intermediate frequency (IF) module and radio frequency (RF) frontend are described. For real-time DSP implementation with affordable field programmable gate array (FPGA) device, some effective strategies are discussed to reduce resource usage and ensure that the clock constraints are met. Adopting these strategies, all physical layer DSP modules are implemented in two FPGAs with more than 300 MHz system clock. The experimental test results using the developed real-time digital modem prototype demonstrate the superb performance for THz wireless communications.
  • Yuyue Luo, J. Andrew Zhang, Xiaojing Huang, Wei Ni, Jin Pan
    IEEE Transactions on Communications 67 9 6468 - 6482 2019年09月 
    Joint communication and radio sensing (JCAS) in millimeter-wave (mmWave) systems requires the use of a steerable beam. For analog antenna arrays, a single beam is typically used, which limits the sensing area within the direction of the communication. Multibeam technology can overcome this limitation by separately generating package-level direction-varying sensing subbeams and fixed communication subbeams and then combine them coherently. In this paper, we investigate the optimal combination of the two subbeams and the quantization of the beamforming (BF) vector that generates the combined beam. When either the full channel matrix or only the angle of departure (AoD) of the dominating line-of-sight (LOS) path is known at the transmitter, we derive the closed-form expressions for the optimal combining coefficients that maximize the received communication signal power. For the quantization of the BF vector, we focus on the two-phase-shifter array where two phase shifters are used to represent each BF weight. We propose novel joint quantization methods by combining the codebooks of the two phase shifters. The mean squared quantization error is derived for various quantization methods. Extensive simulation results validate the accuracy of the analytical results and the effectiveness of the proposed multibeam optimization and joint quantization methods.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    2019 International Radar Conference, RADAR 2019 2019年09月 
    The generalized continuous wave synthetic aperture radar (GCW-SAR) adopts one-dimensional data recording without the slow time dimension and hence offers many advantages compared with the conventional SAR system. In this paper, a fast piecewise constant Doppler algorithm is proposed based on further zero-th order approximation on top of the linear approximation of the slant range, leading to a flexible azimuth imaging spacing. Significant reduction of the complexity can be achieved by extending the azimuth imaging spacing and downsampling the received signal in digital domain. Simulation results validate the advantages of the proposed algorithm.
  • Hongyang Zhang, Xiaojing Huang, J. Andrew Zhang
    2019 IEEE/CIC International Conference on Communications in China, ICCC 2019 828 - 833 2019年08月 
    Orthogonal time frequency space (OTFS) modulation shows great performance improvement over high-mobility wireless channels compared with traditional orthogonal frequency division multiplexing (OFDM). In this paper, we first derive the input and output relationship of OTFS signal in the delay-time domain, which shows that OTFS can be regarded as a combination of OFDM and single-carrier frequency-division multiple access (SC-FDMA). We then examine the diversity order of an OTFS system through received signal-to-noise ratio analysis and predict that this modulation technique can potentially achieve full diversity in both delay and Doppler domains. Finally, we simulate the OTFS performance based on 5G tapped-delay-line channel models under both slow and fast fading conditions. Extensive simulation results confirm that OTFS performs significantly better than other modulation techniques in fast fading channels.
  • Gordon J. Sutton, Jie Zeng, Ren Ping Liu, Wei Ni, Diep N. Nguyen, Beeshanga A. Jayawickrama, Xiaojing Huang, Mehran Abolhasan, Zhang Zhang, Eryk Dutkiewicz, Tiejun Lv
    IEEE Communications Surveys and Tutorials 21 3 2488 - 2524 2019年07月 
    Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements.
  • Hang Li, Thomas Q. Wang, Xiaojing Huang, J. Andrew Zhang, Y. Jay Guo
    IEEE Transactions on Communications 67 5 3512 - 3524 2019年05月 
    In this paper, we study the low complexity reception of multiuser signals in uplink millimeter wave (mmWave) communications using a partially connected hybrid antenna array. Exploiting the mmWave channel property, we propose a low-complexity user-directed multiuser receiver with three novel schemes for allocating subarrays to users. This receiver only requires the knowledge of angles-of-Arrival (AoAs) for dominating paths and a small amount of equivalent channel information instead of perfect channel state information. For comparison, we also derive a successive interference cancellation-based solution as a performance benchmark. We design two types of reference signals with the channel estimation method to enable efficient and simple estimation for AoA and equivalent baseband channel. Also, we provide analytical results for the performance of the AoA estimation, using the lower bounds of mean square errors in line-of-sight dominated mmWave channels. The simulation results validate that the proposed channel estimation method is effective when employed in combination with a zero-forcing equalizer.
  • Yuyue Luo, J. Andrew Zhang, Shaode Huang, Jin Pan, Xiaojing Huang
    IEEE International Conference on Communications 2019-May 2019年05月 
    We propose a novel joint quantization scheme for hybrid antenna array systems using the two-phase-shifter (2-PS) structure, where two phase shifters are combined to represent one beamforming weight. Conventional quantization using a single phase shifter for each beamforming weight cannot represent the magnitude. We propose a new codebook design that combines the two codebooks of the two phase shifters in the recently proposed 2-PS structure. We also study the scaling problem of the beamforming vector and propose a low-complexity searching algorithm for finding a near-optimal scalar based on element-wise quantization. The mean squared quantization error and signal-to-noise ratio (SNR) degradation are derived analytically. Simulation results validate the accuracy of the analytical results and the effectiveness of the proposed quantization methods.
  • Hang Li, Thomas Q. Wang, Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications Letters 8 2 540 - 543 2019年04月 
    This letter proposes a novel hybrid dual-polarized antenna array which exploits two orthogonally collocated dipoles to capture the full power of a polarized millimeter wave signal. To maximize the received signal-to-noise ratio (SNR), we study the adaptive angle-of-arrival and polarization state estimation, and develop a differential beam tracking algorithm and a cross-correlation-to-power ratio polarization tracking algorithm for interleaved hybrid dual-polarized arrays. Simulation results verify the superior performance of the proposed algorithms, and confirm the significant improvement of SNR obtained by using the proposed array and algorithms.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang, Y. Jay Guo, J. Yiannis C. Vardaxoglou
    IEEE Transactions on Communications 67 1 682 - 692 2019年01月 
    Analog least mean square (ALMS) loop is a promising method to cancel self-interference (SI) in in-band full-duplex (IBFD) systems. In this paper, the steady state analyses of the residual SI powers in both analog and digital domains are firstly derived. The eigenvalue decomposition is then utilized to investigate the frequency domain characteristics of the ALMS loop. Our frequency domain analyses prove that the ALMS loop has an effect of amplifying the frequency components of the residual SI at the edges of the signal spectrum in the analog domain. However, the matched filter in the receiver chain will reduce this effect, resulting in a significant improvement of the interference suppression ratio (ISR). It means that the SI will be significantly suppressed in the digital domain before information data detection. This paper also derives the lower bounds of ISRs given by the ALMS loop in both analog and digital domains. These lower bounds are joint effects of the loop gain, tap delay, number of taps, and transmitted signal properties. The discovered relationship among these parameters allows the flexibility in choosing appropriate parameters when designing the IBFD systems under given constraints.
  • Thomas Q. Wang, Hang Li, Xiaojing Huang
    IEEE Transactions on Communications 67 1 564 - 577 2019年01月 
    Due to the limited dynamic range of the off-the-shelf electrical and optical components, deliberate digital clipping (DDC) is widely applied to optical orthogonal frequency division multiplexing (OFDM) based visible light communication systems. In this paper, we present a theoretical characterization of the layered asymmetrically clipped optical OFDM (ACO-OFDM) signals subject to peak clipping. We decouple a clipped L-layer ACO-OFDM symbol to L single-layer ACO-OFDM symbols, each corresponding to a layer, and show that these symbols are subject to symmetrical peak clippings at random levels. Using Bussgang's theorem, the resulting attenuation factors and variances of the additive noise associated with each layer are derived. It is shown that the clipping noise caused by the DDC mainly falls onto the first layer, and its impact is gradually reduced in the subsequent layers. In order to combat the clipping noise, a novel receiver based on decision aided reconstruction is proposed. Simulation results show that the proposed receiver can effectively mitigate the clipping noise, leading to significant improvement of bit error rates over the conventional receiver.
  • J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Jinhong Yuan, Robert W. Heath
    IEEE Transactions on Vehicular Technology 68 1 671 - 685 2019年01月 
    Beamforming has a great potential for joint communication and radar sensing (JCAS), which is becoming a demanding feature on many emerging platforms, such as unmanned aerial vehicles and smart cars. Although beamforming has been extensively studied for communication and radar sensing respectively, its application in the joint system is not straightforward due to different beamforming requirements by communication and sensing. In this paper, we propose a novel multibeam framework using steerable analog antenna arrays, which allows seamless integration of communication and sensing. Different to conventional JCAS schemes that support JCAS using a single beam, our framework is based on the key innovation of multibeam technology: providing fixed subbeam for communication and packet-varying scanning subbeam for sensing, simultaneously from a single transmitting array. We provide a system architecture and protocols for the proposed framework, complying well with modern packet communication systems with multicarrier modulation. We also propose low-complexity and effective multibeam design and generation methods, which offer great flexibility in meeting different communication and sensing requirements. We further develop sensing parameter estimation algorithms using conventional digital Fourier transform and one-dimensional compressive sensing techniques, matching well with the multibeam framework. Simulation results are provided and validate the effectiveness of our proposed framework, beamforming design methods, and the sensing algorithms.
  • Hao Zhang, Xiaojing Huang, Jian A. Zhang, Y. Jay Guo, Rui Liang Song, Chun Ting Wang, Wei Wu, Xiao Fan Xu, Zhou Lu
    Proceedings - IEEE International Symposium on Circuits and Systems 2019-May 2019年 
    A millimeter wave system with commercially available and affordable data conversion devices is presented in this paper for achieving high-speed and low-cost wireless communications. By adopting the proposed dual pulse shaping (DPS) transmission scheme, the system can achieve full Nyquist rate transmission with only half of the sampling rate required by conventional Nyquist pulse shaping. Structures of the DPS transmitter and receiver are described and effective symbol rate equalization techniques suitable for DPS transmission are presented. Simulation results with two sets of practical dual spectral shaping pulses are also provided to compare system performance with the conventional Nyquist pulse shaping system.
  • Hang Li, Thomas Q. Wang, Xiaojing Huang
    IEEE Access 7 76353 - 76366 2019年 
    The propagation of a millimeter wave (mmWave) signal is dominated by its line-of-sight component. Therefore, the knowledge of angle-of-arrival and polarization state of the wave is of great importance for its reception at the receiver. In this paper, we estimate these parameters for an information-bearing signal in mmWave systems using hybrid antenna arrays with dual-polarized dipoles. The estimation is studied in the context of both the interleaved and localized arrays. Two blind adaptive algorithms, namely, the joint differential beam tracking and cross-correlation-to-power ratio polarization tracking, and the differential beam and polarization search, are developed, each tailored for an array. It is shown that the use of dual-polarized dipoles in combination with the developed algorithms effectively lead to polarization diversity which significantly enhances the signal-to-noise ratio at the decoder. The simulation results also show that the antennas with dual dipoles provide improved accuracy and convergence rate for the estimations compared with the conventional arrays.
  • Weijie Yuan, Nan Wu, Qinghua Guo, Xiaojing Huang, Yonghui Li, Lajos Hanzo
    IEEE Transactions on Communications 67 10 6952 - 6962 2019年 
    Passive localization based on time of arrival (TOA) measurements is investigated, where the transmitted signal is reflected by a passive target and then received at several distributed receivers. After collecting all measurements at receivers, we can determine the target location. The aim of this paper is to provide a unified factor graph-based framework for passive localization in wireless sensor networks based on TOA measurements. Relying on the linearization of range measurements, we construct a Forney-style factor graph model and conceive the corresponding Gaussian message passing algorithm to obtain the target location. It is shown that the factor graph can be readily modified for handling challenging scenarios such as uncertain receiver positions and link failures. Moreover, a distributed localization method based on consensus-aided operation is proposed for a large-scale resource constrained network operating without a fusion center. Furthermore, we derive the Cramér-Rao bound (CRB) to evaluate the performance of the proposed algorithm. Our simulation results verify the efficiency of the proposed unified approach and of its distributed implementation.
  • Yuyue Luo, J. Andrew Zhang, Wei Ni, Jin Pan, Xiaojing Huang
    Proceedings - IEEE Global Communications Conference, GLOBECOM 2019年 
    Multibeam technology has recently been proposed for joint communication and radio sensing (JCAS) in millimeter wave systems using analog antenna arrays. Generation of the multibeam satisfying both communication and sensing requirements is yet to be developed. In this paper, we develop closed-form solutions for optimizing the coefficient that combines communication and sensing subbeams to generate a multibeam. Our solutions maximize the received signal power for communication, in the cases (1) without constraint on sensing beamforming (BF) waveform, (2) with minimum BF gain constraints on discrete sensing directions, and (3) with a minimum total power constraint on a range of sensing directions. Simulation results are provided and validate the effectiveness of the proposed solutions.
  • Hao Zhang, Xiaojing Huang, Y. Jay Guo
    ISCIT 2018 - 18th International Symposium on Communication and Information Technology 171 - 175 2018年12月24日 
    A low-complexity digital modem is presented in this paper for achieving high-speed and wideband point-To-point (P2P) wireless communications. By combining multiple functionalities into the transmitter and receiver filters, the signal processing complexity in the digital baseband can be significantly reduced. The structures and the implementation using field programmable gate array (FPGA) for the transmitter and receiver filters are described in details. Pre-equalization for reducing the impact of practical channel frequency response can be easily incorporated into the transmitter filter structure. The experimental test results using a 20 Gigabits per second (Gbps) digital modem prototype demonstrate the satisfactory performance with low FPGA resource usage.
  • Weijie Yuan, Nan Wu, Chaoxing Yan, Yonghui Li, Xiaojing Huang, Lajos Hanzo
    IEEE Transactions on Vehicular Technology 67 12 12398 - 12403 2018年12月 
    Sparse code multiple access (SCMA) has emerged as a promising non-orthogonal multiple access technique for the next-generation wireless communication systems. Since the signal of multiple users is mapped to the same resources in SCMA, its detection imposes a higher complexity than that of the orthogonal schemes, where each resource slot is dedicated to a single user. In this paper, we propose a low-complexity receiver for SCMA systems based on the radical variational free energy framework. By exploiting the pairwise structure of the likelihood function, the Bethe approximation is utilized for estimating the data symbols. The complexity of the proposed algorithm only increases linearly with the number of users, which is much lower than that of the maximum a posteriori detector associated with exponentially increased complexity. Furthermore, the convergence of the proposed algorithm is analyzed, and its convergence conditions are derived. Simulation results demonstrate that the proposed receiver is capable of approaching the error probability performance of the conventional message-passing-based receiver.
  • Yijiang Nan, Xiaojing Huang, Yingjie Jay Guo
    IEEE Transactions on Geoscience and Remote Sensing 56 12 7217 - 7229 2018年12月 
    A generalized continuous wave synthetic aperture radar (GCW-SAR) concept is proposed in this paper. By using full-duplex radio frontend and continuous wave signaling, the GCW-SAR system can overcome a number of limitations inherent within the existing SAR systems and achieve high-resolution and wide-swath remote sensing with low-power signal transmission. Unlike the conventional pulsed SAR and the frequency-modulated continuous-wave SAR, the GCW-SAR reconstructs a radar image by directly correlating the received 1-D raw data after self-interference cancellation with predetermined location-dependent reference signals. A fast imaging algorithm, called the piecewise constant Doppler (PCD) algorithm, is also proposed, which produces the radar image recursively in the azimuth direction without any intermediate step, such as range compression and migration compensation, as required by conventional algorithms. By removing the stop-and-go assumption or slow-time sampling in azimuth, the PCD algorithm not only achieves better imaging quality but also allows for more flexible waveform and system designs. Analyses and simulations show that the GCW-SAR tolerates significant self-interference and works well with a large selection of various system parameters. The work presented in this paper establishes a solid theoretical foundation for next-generation imaging radars.
  • Weijie Yuan, Qiaolin Shi, Nan Wu, Qinghua Guo, Xiaojing Huang
    IEEE Vehicular Technology Conference 2018-June 1 - 5 2018年07月20日 
    This paper considers the issue of passive localization based on time of arrival (TOA) measurement in the presence of receiver detection failures. In passive localization, the signal sent from the transmitter is reflected or relayed by «passive» target and then received at several distributed receivers. The target's position can be determined by collecting range mea- surements from all receivers. With a linearized model for range measurements, we build a factor graph model and implement Gaussian message passing algorithm to obtain target location and detect link failures. The Cramer-rao bound (CRB) is also derived to evaluate the performance of proposed algorithm. Simulation results verify the effectiveness of proposed factor graph approach.
  • Anh Tuyen Le, Yijiang Nan, Le Chung Tran, Xiaojing Huang, Y. Jay Guo, Yiannis Vardaxoglou
    IEEE Vehicular Technology Conference 2018-August 2018年07月02日 
    Generalized continuous wave synthetic aperture radar (GCW-SAR) is a promising new imaging radar system since it applies the full-duplex (FD) transmission technique to achieve continuous signaling in order to overcome several fundamental limitations of the conventional pulsed SARs. As in any FD wireless communication system, self-interference (SI) is also a key problem which can impact on the GCW-SAR system. In this paper, the analog least mean square (ALMS) loop in the radio frequency domain is adopted to cancel the SI for a GCW-SAR system with periodic chirp signaling. The average residual SI power after the ALMS loop is analyzed theoretically by a stationary analysis. It is found that the ALMS loop not only works with random signals in general FD communication systems, but also works well with the periodic signal in GCW-SAR systems. Simulation results show that over 45 dB SI cancellation can be achieved by the ALMS loop which ensures the proper operation of the GCW-SAR system.
  • Hang Li, Thomas Q. Wang, Xiaojing Huang, Y. Jay Guo
    IEEE Vehicular Technology Conference 2018-August 2018年07月02日 
    The superiority of exploring millimeter wave (mmWave) frequencies for future wireless communication systems has pushed forward the development of large-scale antenna arrays for achieving sufficient array gain and high spectral efficiency. In this paper, we study the matrix normalization (MN) based zero-forcing (ZF) hybrid precoding in multi-user multi-input-multi-output (MU-MIMO) mmWave systems. We derive the upper bounds of the achievable rate for two representative hybrid array structures, i.e., fully-connected structure and partially-connected structure. Analytical and simulation results validate the tightness of the proposed performance upper bounds for both hybrid structures using massive array, and provide a comparison of the achievable rate using MN and vector normalization (VN).
  • Thomas Q. Wang, Hang Li, Xiaojing Huang
    Journal of Lightwave Technology 36 11 2100 - 2113 2018年06月01日 
    In this paper, we study a novel two-stage receiver to demodulate layered asymmetrically clipped optical orthogonal frequency division multiplexing for intensity modulation direct detection based visible light communications. Designed for avoiding the error propagation of the conventional receiver, the first stage of the receiver is a soft interference cancellation (SIC) module which evaluates the minimum mean square error (MMSE) estimates of the signals in different layers. For this stage, we derive the exact formula of the MMSE estimator, and compare the achieved mean square error and bit error rate (BER) with those of the existing simplified SIC receiver. We show that the estimation error in a layer has negligible impact on the design of estimators in the subsequent layers. Using the outputs of the SIC module, the second stage performs noise clipping to suppress the additive noise. For this stage, we present two schemes, the SIC-based iterative noise clipping (SIC-INC) and the SIC-based direct noise clipping (SIC-DNC). The simulation results show that SIC-INC can achieve BERs similar to those of the SIC-based diversity combining receiver with optimum combining coefficients. It is also shown that SIC-DNC outperforms the existing advanced receivers by up to 0.8 dB at the BER of 10{-4}.
  • Thomas Q. Wang, Xiaojing Huang
    IEEE Transactions on Communications 66 4 1565 - 1578 2018年04月 
    In this paper, fractional reverse polarity optical orthogonal frequency division multiplexing (FRPO-OFDM) is studied to enable dimming compatible visible light communications. The scheme combines a layered asymmetrically clipped optical OFDM (ACO-OFDM) sequence with an information-carrying brightness control sequence (BCS) in the form of M -ary pulse position modulation. We derive the expressions of the FRPO-OFDM signal and its achievable brightness level, and develop an effective detector which can recover information from both sequences based on maximum likelihood detection. We show that when the detector is to be implemented, the use of multi-layer ACO-OFDM imposes strong periodicity on the BCS, which leads to a trade-off between spectral efficiency and brightness resolution for dimming control. It is shown that high spectral efficiency can be achieved with practical dimming requirements. Simulation results show that the extra information carried by the BCS can be decoded with extremely low bit error rate and thus has negligible impacts on the demodulation of the ACO-OFDM signal, when the system nonlinearity is not dominating.
  • Gordon J. Sutton, Jie Zeng, Ren Ping Liu, Wei Ni, Diep N. Nguyen, Beeshanga A. Jayawickrama, Xiaojing Huang, Mehran Abolhasan, Zhang Zhang
    IEEE Network 32 2 70 - 77 2018年03月 
    In this article, we aim to address the question of how to exploit the unlicensed spectrum to achieve URLLC. Potential URLLC PHY mechanisms are reviewed and then compared via simulations to demonstrate their potential benefits to URLLC. Although a number of important PHY techniques help with URLLC, the PHY layer exhibits an intrinsic trade-off between latency and reliability, posed by limited and unstable wireless channels. We then explore MAC mechanisms and discuss multi-channel strategies for achieving low-latency LTE unlicensed band access. We demonstrate, via simulations, that the periods without access to the unlicensed band can be substantially reduced by maintaining channel access processes on multiple unlicensed channels, choosing the channels intelligently, and implementing RTS/CTS.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang
    IEEE Communications Letters 21 12 2738 - 2741 2017年12月 
    Analog least mean square (ALMS) loop is a promising mechanism to suppress self-interference (SI) in an in-band full-duplex (IBFD) system. In this letter, a general solution for the weighting error function is derived to investigate the performance of the ALMS loop employed in any IBFD system. The solution is then applied to IBFD systems with single carrier and multicarrier signaling. Due to the cyclostationary property of the transmitted signal, the weighting error function in the multicarrier system varies more significantly than in the single carrier. Therefore, if the ALMS loop can perfectly mimic the SI channel, SI in the single carrier system can be suppressed to a much smaller level than that in the multi-carrier counterpart.
  • Hao Zhang, Xiaojing Huang, Y. Jay Guo
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    The rapid growth of mobile broadband wireless services in recent years demands high speed data transmission for both access and backhaul networks. With the increase of data rate for 5G access to tens of Gigabits per second (Gbps), higher speed transmission for backhaul network is necessary. Current wireless backhaul systems have been able to achieve the data rate of multiple Gbps, but the ability to deal with significant practical impairments such as large carrier frequency offset and IQ mismatch is still a technical challenge. In this paper, a 20 Gbps digital modem for wireless backhaul applications is proposed. Simulation and field programmable gate array implementation show that the the proposed design and signal processing algorithms meet the targeted system performance.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    Attention has been devoted to Synthetic Aperture Radar (SAR) for half a century. Though it is a well-proven remote sensing technique, conventional pulsed SAR has several inherent limitations. In this paper, we present a new SAR concept, called Generalized Continuous Wave SAR (GCW-SAR). By using continuous wave signaling, the GCW-SAR system achieves better performance and overcomes the limitations such as the minimum antenna area in conventional SAR. Unlike the frequency modulated continuous wave SAR (FMCW-SAR) system, the GCW-SAR image is reconstructed by correlation between the sampled raw data and the location dependent reference signals. A fast image reconstruction algorithm is also presented in the paper. The principle of GCW-SAR and the effectiveness of the proposed algorithm are validated by numerical simulation results.
  • J. Andrew Zhang, Hang Li, Xiaojing Huang, Y. Jay Guo, Antonio Cantoni
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    Beamforming design for millimeter-Wave hybrid array with the subarray structure is very challenging. There is neither known optimal solution that maximizes the sum rate capacity nor near-optimal solution. This paper proposes some low-complexity user-directed analog radio- frequency (RF) beamforming design schemes. The basic idea is to iteratively allocate different subarrays to different users such that users' channel correlation can be efficiently reduced via RF beamforming. Several new but less efficient schemes are also presented to shed light on RF beamforming design, and to serve as comparisons for the user-directed schemes. Simulation results are provided for these proposed schemes, existing ones in the literature and an upper-bound for hybird array with a fully-connected structure. The user-directed schemes demonstrate significantly better sum-rate and BER performance over other schemes, although the gap to the upperbound is still large.
  • J. Andrew Zhang, Antonio Cantoni, Xiaojing Huang, Y. Jay Guo, Robert W. Heath
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    In this paper, we develop a framework for an innovative perceptive mobile (i.e. cellular) network that integrates sensing with communication, and supports new applications widely in transportation, surveillance and environmental sensing. Three types of sensing methods implemented in the base-stations are proposed, using either uplink or downlink multiuser communication signals. The required changes to system hardware and major technical challenges are briefly discussed. We also demonstrate the feasibility of estimating sensing parameters via developing a compressive sensing based scheme and providing simulation results to validate its effectiveness.
  • Thomas Q. Wang, Xiaojing Huang
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    In this paper, we study a novel optical orthogonal frequency division multiplexing (OFDM) scheme, fractional reversed polarity optical OFDM (FRPO- OFDM), which enables dimmable visible light communications. The scheme combines an asymmetrically clipped optical OFDM (ACO-OFDM) sequence with an information-carrying brightness control sequence (BCS). We show that the new scheme can create a wide range of brightness levels whilst transmitting extra information using the BCS to enhance the spectral efficiency. The detector which can recover information from both sequences is derived based on maximum likelihood (ML) detection and estimation. It is shown that the information carried by the BCS using variable on-off keying (VOOK) can be detected with extremely low bit error rate (BER) and that the resulting overall BER of FRPO-OFDM is constant over a wide dimming range.
  • Anh Tuyen Le, Le Chung Tran, Xiaojing Huang
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    This paper evaluates the performance of an analog least mean square (ALMS) loop employed to cancel self-interference in in-band full-duplex (IBFD) orthogonal frequency division multiplexing (OFDM) systems. Cyclostationary analysis is applied to investigate the behavior of the ALMS filter. It is revealed that the performance of the ALMS filter for OFDM systems primarily depends on windowing function rather than pulse shaping as in single carrier systems. It is also noticed that the ALMS loop in OFDM systems provides a much higher level of sel-interference (SI) suppression because OFDM signals lead to reduced the error of the interference channel modelling with the adaptive filter. Simulations are then conducted to verify the theoretical findings.
  • J. Andrew Zhang, Antonio Cantoni, Xiaojing Huang, Y. Jay Guo, Robert W. Heath
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    Beam-steering has great potentials for joint communications and sensing, which is becoming a demanding feature on many emerging platforms such as unmanned aerial vehicles and smart cars. Although beam-steering has been extensively studied for communications and radar sensing respectively, its application in the joint system is not straightforward due to different beamforming requirements by communications and sensing. In this paper, we propose a low-cost system framework which allows seamless operation of communications and sensing, using two small- size steerable analog antenna arrays. We provide system architecture, high-level protocols, detailed signal model, novel beamforming design and advanced 1D compressive sensing algorithms for joint communications and sensing. We also provide preliminary simulation results which validate the effectiveness of the proposed technique in resolving closely located objects.
  • Wei Wu, Renping Liu, Wei Ni, Dali Kaafar, Xiaojing Huang
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    The logically-centralized controllers have largely operated as the coordination points in software-defined networking(SDN), through which applications submit network operations to manage the global network resource. Therefore, the validity of these network operations from SDN applications are critical for the security of SDN. In this paper, we analyze the mechanism that generates network operations in SDN, and present a fine-grained access control model, called Access Control Protector(AC-PROT),that employs an attribute-based signature scheme for network applications. The simulation result demonstrates that AC-PROT can efficiently identify and reject unauthorized network operations generated by applications.
  • Hang Li, Thomas Q. Wang, Xiaojing Huang, Jian A. Zhang
    IEEE Vehicular Technology Conference 2017-June 2017年11月14日 
    Due to the enormous needs for signal processing and hardware constraints, the full digital implementation for a large antenna array at mmWave frequencies becomes intractable. Hence, receiver design for MIMO system with massive hybrid array is very demanding, particularly for subarray structure. In this paper, we propose two low- complexity uplink multiuser receiver design schemes (single-beam and multi-beam) under the circumstances of only users' angles of arrival (AOAs) available at base station, which greatly simplify the analog beamforming structure and reduce the complexity of channel estimation especially when the number of antenna elements is considerably large. In the single-beam scheme, subarrays are mapped to different users one by one such that each subarray serves a specific user. In the multibeam scheme, all subarrays use the same analog beamforming and any subarray's beamforming signal potentially points at all users. Digital beamforming is then employed to combine all subarray signals followed by equalization. Simulations are performed to compare the proposed schemes with other schemes that need channel information available at the subarray output. Since only AOAs are required for analog and digital beamformings, the proposed schemes are more suitable for mmWave MIMO system with massive hybrid array in spite of slight sum-rate loss.
  • Md Lushanur Rahman, J. Andrew Zhang, Xiaojing Huang, Y. Jay Quo
    2017 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2017 2017-January 199 - 202 2017年10月06日 
    In this paper, we consider an alternative low-cost and flexible solution of using an analog antenna array for radio sensing at the base station receiver in the recently proposed perceptive mobile networks. We provide receiver beamforming design, and advanced compressive sensing (CS) signal processing techniques for sensing parameter estimation in a multiuser-MIMO (MU-MIMO) communications system. Simulation results are provided and validate the effectiveness of the proposed solution and sensing algorithms.
  • J. Andrew Zhang, Xiaojing Huang, Y. Jay Guo, Md Lushanur Rahman
    2017 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2017 2017-January 67 - 70 2017年10月06日 
    We propose signal stripping based approaches for estimating detailed channel composition parameters for sensing in the recently proposed perceptive mobile networks where simultaneous communication and radar sensing is performed. Via reconstructing a (differentiated) channel matrix, we obtain a signal model which can be solved by conventional compressive sensing (CS) techniques. Parameter estimation methods based on a 1-D CS algorithm are proposed and their effectiveness is validated by provided simulation results.
  • Yijiang Nan, Xiaojing Huang, Y. Jay Guo
    2017 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2017 2017-January 41 - 44 2017年10月06日 
    This paper presents a non-cooperative space-surface bistatic synthetic aperture radar (SS-BSAR) with a novel image reconstruction algorithm. Exploiting the continuous wave signal from the transmitters of opportunity, the new algorithm produces better imaging performance. Unlike the conventional passive SAR, the image reconstruction is achieved by correlation in time-domain without distinction between fast time and slow time. With the movement of the radar, the range curve can be linearized within multiple segments. In each segment, the Doppler frequency shift incurred in the reflected signal from a target can be assumed to be constant and thus the SAR image can be reconstructed recursively. The proposed piecewise constant Doppler (PCD) algorithm is validated by the simulation results.
  • Hang Li, Xiaojing Huang
    IEEE Transactions on Vehicular Technology 66 10 8835 - 8844 2017年10月 
    Multicasting is emerging as an efficient method to deliver the same data to a group of users, thereby saving network resources. The fairness between different multicast groups is an important quality-of-service (QoS) indication, but it has not been given significant attention. In this paper, we propose a normalized signal-To-noise ratio (SNR)-based fair scheduling for multiple multicast groups in multicast systems. The system fairness and capacity are then analyzed and compared for both fair scheduling and greedy scheduling over independent but non-identically distributed (i.n.d.) fading channels. Closed-form expressions in terms of the system spectral efficiency, outage probability, system fairness, and average bit error rate (BER) are derived in an uncoded/coded M-Ary quadrature amplitude modulation based adaptive transmission multicast system over i.n.d. Rayleigh fading channels. Numerical results show that compared with greedy scheduling, fair scheduling achieves considerably high fairness at the cost of slight system capacity loss, regardless of the number of multicast groups. Our focus is on the physical layer without rate loss, but we also briefly discuss applications of the proposed scheduling in a cross-layer design subject to the loss rate QoS constraint.
  • Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Microwave Theory and Techniques 65 9 3336 - 3350 2017年09月 
    A multitap adaptive filter with analog least mean-square (ALMS) loop is proposed in this paper for effective and low complexity self-interference cancellation implemented as part of the radio frequency frontend in a full duplex transceiver. Comprehensive analyses of the ALMS loop's behaviors at both micro and macroscales are presented for a wireless communication system with single carrier signaling. It is revealed that there is always an irreducible residual interference due to the cyclostationary property of the transmitted signal. The interference suppression ratio (ISR) lower bound is derived accordingly, which can be used as a design rule for determining the ALMS loop parameter. Stationary analysis shows that the convergence speed and achievable ISR of the ALMS loop are determined by the loop gain and the autocorrelation function of the transmitted signal. The interference channel modeling error with the adaptive filter also accounts for part of the residual interference power. These theoretical findings are verified by simulation and experimental results.
  • Licai Fang, Hang Li, Defeng David Huang, Xiaojing Huang
    2017 17th International Symposium on Communications and Information Technologies, ISCIT 2017 2018-January 1 - 5 2017年07月01日 
    The great potential of exploiting millimeter wave (mmwave) frequency spectrum for emerging fifth-generation (5G) wireless networks has motivated the study of massive multiple-input multiple-output (MIMO) for achieving high data rate. For medium-size massive MIMO with orthogonal frequency division multiplexing (OFDM) uplink systems, the minimum mean square error (MMSE) based soft-output detector is often used due to its better bit error rate (BER) performance compared to the matched filter detector. Although the multipath channel can be converted into a set of parallel flat-fading channels by using OFDM thus reducing the complexity of receiver design, the tone by tone (per subcarrier) detection methods based on the state-of-The-Art low complexity MMSE still incur considerably high computational complexity since the number of tones is typically very large. To reduce the complexity, the interpolation-based matrix inversion algorithms for small-size MIMO-OFDM systems have been proposed, which compute the matrix inversion by interpolating separately the adjoint and determinant. In this paper, we find that the (regularized) Gram matrix inversions have strong correlation between different subcarriers. By exploiting this strong correlation, we propose a linear interpolation based MMSE detection algorithm that directly interpolates the inverted MMSE matrices for a small number of subcarriers to obtain matrix inversions for all other subcarriers, thereby significantly reducing the number of matrix inversion required. Extensive simulations show that with small BER performance loss compared to the exact MMSE detector, the proposed algorithm can reduce the complexity to the level of the matched filter algorithm.
  • Thomas Q. Wang, Hang Li, Xiaojing Huang
    IEEE Communications Letters 21 6 1309 - 1312 2017年06月 
    In this letter, we present a novel diversity combining receiver for demodulating layered asymmetrically clipped optical orthogonal frequency division multiplexing. The receiver consists of a soft successive interference cancellation (SIC) module which cancels the inter-layer interference (ILI) using the minimum mean square error (MMSE) estimates of the information symbols, and a diversity combining module which extracts the diversity components from the clipping noise. We show that the soft SIC module alone can effectively suppress the ILI, leading to bit error rates (BERs) resembling those of a genie receiver which is free of error propagation. It is also shown that the diversity combining receiver which combines the MMSE estimates with their diversity components outperforms the genie receiver by up to 2 dB at the BER of 10-6.
  • J. A. Zhang, X. Huang, V. Dyadyuk, Y. Jay Guo
    mmWave Massive MIMO: A Paradigm for 5G 39 - 61 2017年 
    This chapter introduces the massive hybrid array architecture, where antenna elements are grouped into multiple analog subarrays, and a single digital signal is received from or sent to each subarray. It provides an affordable and spatially feasible solution for millimeter-wave (mmWave) massive array, and can achieve comparable performance with a full digital array thanks to the temporal and spatial sparsity of mmWave propagation channels. This chapter starts by presenting the hybrid array architecture, highlighting two typical configurations of interleaved and localized arrays. It then presents four optional hardware implementations of this architecture. Array construction is then discussed through quasi-Yagi antenna arrays and stacked patch antenna with perpendicular feed substrate. Two prototypes, developed by CSIRO and Samsung, are also introduced. After reviewing the hardware development, this chapter further discusses signal processing techniques for hybrid arrays, with focus on angle-of-arrival estimation, single-user line-of-sight multiple-input multiple-output and its capacity, and spatial division multiple access techniques. Overall, this chapter shows that massive hybrid array is a very promising technique for 5G mmWave cellular communications, with vast open research challenges.
  • Hang Li, Xiaojing Huang, Y. Jay Guo
    2016 16th International Symposium on Communications and Information Technologies, ISCIT 2016 73 - 76 2016年11月21日 
    This paper proposes an Improved Quality-Based Channel State Feedback (IQCF) scheme in multicast systems with greedy scheduling for multiple multicast groups. The proposed scheme outperforms the Quality-Based Channel State Feedback (QCF) scheme in the literature by selecting a scheduling outage group for data transmission when scheduling outage happens. We also analyze its performance in terms of average capacity and outage probability, and present a closed-form system average capacity expression over Rayleigh fading channels. The numerically evaluated analytical results are verified by simulations.
  • Meriam Gay Bautista, Eryk Dutkiewicz, Xiaojing Huang, Diep Nguyen, Forest Zhu
    2016 16th International Symposium on Communications and Information Technologies, ISCIT 2016 597 - 601 2016年11月21日 
    This paper reviews the state of the art of a polyphase complex filter for RF front-end low-IF transceivers applications. We then propose a multi-stage polyphase filter design to generate a quadrature I/Q signal to achieve a wideband precision quadrature phase shift with a constant 90 ° phase difference for self-interference cancellation circuit for full duplex radio. The number of the stages determines the bandwidth requirement of the channel. An increase of 87% in bandwidth is attained when our design is implemented in multi-stage from 2 to an extended 6 stages. A 4-stage polyphase filter achieves 2.3 GHz bandwidth.
  • Songlin Sun, Xiaojing Huang, Ju Liu, Xinzhou Cheng
    2016 16th International Symposium on Communications and Information Technologies, ISCIT 2016 2016年11月21日
  • Xiaojing Huang, Y. Jay Guo, Jian A. Zhang
    IEEE Transactions on Wireless Communications 15 11 7657 - 7669 2016年11月 
    Frequency-dependent I/Q imbalance estimation and compensation are of significant practical importance to low-cost wideband systems with an I/Q modulation architecture. To enable multichannel transmission without inter-channel interference, transmitter I/Q imbalance must be pre-compensated to meet stringent transmit mask requirement. In this paper, a simple frequency domain joint transmitter and receiver I/Q imbalance estimation method is proposed for self-calibration of such wideband multichannel transceivers. Using two frequency domain training signals and a phase shifter inserted in the transceiver local loopback channel, the transmitter and receiver I/Q imbalances can be estimated separately. The estimation errors are also analyzed and the mean square error lower bounds are derived. Simulation results are in good agreement with analytical ones. Compared with existing methods, the proposed technique demonstrates better image rejection performance and quicker adaptation to parameter changes, making it more applicable to many wireless systems, especially the multichannel microwave backhaul, for achieving high data rates with high-order modulation and wide transmission bandwidth.
  • Zhangfeng Li, Guoqiang Zhao, Shiyong Li, Houjun Sun, Ran Tao, Xiaojing Huang, Y. Jay Guo
    IEEE Geoscience and Remote Sensing Letters 13 10 1512 - 1516 2016年10月 
    A rotation parameter extraction method based on temporal differencing and image edge detection from range-Doppler images is presented in this letter. The proposed method first detects the motion trail of the moving pixels caused by the rotating parts in temporal differential range-Doppler images using image edge detection. A Doppler-slow-time image is then generated from the edge pixels on the motion trail. Finally, the rotation parameters are extracted from the Doppler-slow-time image. The proposed method is simple, rapid, and practical. Computer simulations and experimental results demonstrate its effectiveness in terms of computation time compared with existing methods.
  • Jian A. Zhang, Zhuo Chen, Peng Cheng, Xiaojing Huang
    Signal Processing 118 153 - 158 2016年07月25日 
    Abstract Sparse Bayesian learning (SBL) has high computational complexity associated with matrix inversion in each iteration. In this paper, we investigate complexity reduced multiple-measurement vector (MMV) based implementation for single-measurement vector SBL problems. For problems with special structured sensing matrices, we propose two sub-optimal SBL schemes with significantly reduced complexity and slight estimation performance degradation, by exploiting the deterministic correlation in the converted MMV model explicitly. Two application scenarios on channel estimation in multicarrier systems and direction of arrival estimation are presented. Simulation results validate the effectiveness of the schemes.
  • Zhi Lin, Lin Wang, Eryk Dutkiewicz, Xiaojing Huang
    IEEE Vehicular Technology Conference 2016-July 2016年07月05日 
    Compressed sensing based noncoherent UWB systems have been proved to be feasible with a sub-Nyquist sampling rate. As a kind of noncoherent UWB systems, code-shifted differential chaos shift keying (CS- DCSK) UWB system has drawn much attention recently. However, its receiver cannot directly be combined with compressed sensing to reduce the sampling rate. With this motivation, in this paper, we redesign the receiver of the CS-DCSK UWB system and further design two compressed sensing based receivers where the measurement matrix is redesigned. Bit error rate (BER) expression is derived over UWB channel. It is shown that the simulation results are in good agreement with the theoretical ones.
  • Xianjun Yang, Qimei Cui, Eryk Dutkiewicz, Xiaojing Huang, Xiaofeng Tao, Gengfa Fang
    IEEE Wireless Communications and Networking Conference, WCNC 275 - 280 2016年04月 
    Denoising recovery algorithms are very important for the development of compressed sensing (CS) theory and its applications. Considering the noise present in both the original sparse signal x and the compressive measurements y, we propose a novel denoising recovery algorithm, named Regularized Subspace Pursuit (RSP). Firstly, by introducing a data pre-processing operation, the proposed algorithm alleviates the noise-folding effect caused by the noise added to x. Then, the indices of the nonzero elements in x are identified by regularizing the chosen columns of the measurement matrix. Afterwards, the chosen indices are updated by retaining only the largest entries in the Minimum Mean Square Error (MMSE) estimated signal. Simulation results show that, compared with the traditional orthogonal matching pursuit (OMP) algorithm, the proposed RSP algorithm increases the successful recovery rate (and reduces the reconstruction error) by up to 50% and 86% (35% and 65%) in high noise level scenarios and inadequate measurements scenarios, respectively.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang
    IEEE Wireless Communications and Networking Conference, WCNC 1224 - 1229 2016年04月 
    In this paper, spectral efficiency (SE) is investigated for cooperative ultra-wideband (UWB) based on-body area networks (OBANs). To optimize SE for single-relay cooperation, an equivalent generic cooperative model in UWB based OBANs is established first. With the proposed model, joint optimal relay location and power allocation for cooperation is then derived to solve the SE maximization problem. Simulation results show that direct transmission is preferable for UWB based OBANs when the transmitter and receiver are located on the same side of the human body. However, the joint optimal cooperative transmission scheme can achieve a significant improvement on SE compared with direct transmission when the transmitter and receiver are located on the different sides of the human body, which indicates that cooperation is more feasible to be applied in this case due to its robustness to the significant path loss.
  • Xiaojing Huang, Jian A. Zhang, Y. Jay Guo
    2015 15th International Symposium on Communications and Information Technologies, ISCIT 2015 209 - 212 2016年04月 
    This paper proposes a simple frequency domain joint transmitter and receiver I/Q imbalance estimation method which exploits the phase rotation introduced by carrier frequency offset. Using two frequency domain training sequences inserted in each transmission frame, the transmitter and receiver I/Q imbalances can be jointly estimated over multiple frames. The transmitter I/Q imbalance parameter can be fed back to the transmitter for I/Q imbalance pre-compensation, whereas the receiver I/Q imbalance can be compensated locally followed by conventional frequency domain equalization. Numerical simulation results show that the image rejection ratios for both transmitter and receiver after I/Q imbalance compensation can be improved to over 50 dB which is necessary for multichannel systems with high order modulation and wide transmission bandwidth.
  • Sanjeeb Shrestha, Gengfa Fang, Eryk Dutkiewicz, Xiaojing Huang
    2016 13th IEEE Annual Consumer Communications and Networking Conference, CCNC 2016 824 - 828 2016年03月30日 
    In Multi-User Multiple Input Multiple Output (MU-MIMO) Wireless Local Area Networks (WLANs), the optimal-solution such as Dirty Paper Coding (DPC) or the sub-optimal solution Zeroforcing Beamforming (ZFB) with perfect Channel State Information (CSI), is practically limited due to the complexity and the non-availability of perfect CSI at the Access Points (APs)/transmitters. In such a context, ZFB based on channel quantization available at the APs (ZFQ) is the obvious choice for the Multi-User transmission strategy. However, since the quantized CSI is used instead of the perfect CSI at the APs, the quantization error and its impact on the average rate for ZFQ have to be quantified in MU-MIMO WLAN settings. In this paper, we derive a closed-form expression for the upper bound of the channel quantization error and the average rate reduction due to the quantization error with respect to the perfect CSI at the APs. In MU-MIMO WLAN settings, our analytical and numerical studies show that, with an increasing number of antennas at the clients, both the quantization error bound and the average rate reduction increase for ZFQ, in comparison to the ZFB with the perfect CSI.
  • L. C. Tran, A. Mertins, X. Huang, F. Safaei
    IEEE Access 4 8737 - 8756 2016年 
    While relay-based cooperative networks (widely known in the literature as cooperative communication), where relays only forward signals from the sources to the destination, have been extensively researched, fully cooperative systems have not been thoroughly examined. Unlike relay networks, in a fully cooperative network, each node acts as both a source node sending its own data and a relay forwarding its partner's data to the destination. Mutual cooperation between neighboring nodes is believed to improve the overall system error performance, especially when space-time codes are incorporated. However, a comprehensive performance analysis of space-time-coded fully cooperative communication from all three perspectives, namel,y error performance, outage probability, and energy efficiency, is still missing. Answers to the commonly asked questions of whether, in what conditions, and to what extent the space-time-coded fully cooperative communication is better than direct transmission are still unknown. Motivated by this fact and inspired by the increasing popularity of healthcare applications in wireless body area networks (WBANs), this paper derives for the first time a comprehensive performance analysis of a decode-and-forward space-time coded fully cooperative communication network in Rayleigh and Rician fading channels in either identically or non-identically distributed fading scenario. Numerical analysis of error performance, outage probability, and energy efficiency, validated by simulations, show that fully cooperative communication is better than direct transmission from all three aspects in many cases, especially at a low-power and low signal-to-noise ratio regime, which is a typical working condition in WBANs.
  • Lin Ye, Kai Cao, Jay Guo, Xiaojing Huang, Peter Beadle, Ahmadreza Argha, Massimo Piccardi, Guangquan Zhang, Steven W. Su
    Proceedings of the 3rd IASTED International Conference on Telehealth and Assistive Technology, TAT 2016 36 - 43 2016年 
    One of the major public health problems among elderly people is falling injury. This study investigates fall detection and prevention by using inertial sensors for which the major existing challenging is how to significantly reduce false alarming in order to enhance the acceptance of elderly users during rehabilitation and daily exercises. Different from most existing approaches in the literature, the behavior after falling will be analyzed in details, which can not only greatly reduce false alarming, but also significantly improves the accuracy of the assessment of the severity of falling injuries.
  • Sanjeeb Shrestha, Gengfa Fang, Eryk Dutkiewicz, Xiaojing Huang
    Proceedings - 15th IEEE International Conference on Computer and Information Technology, CIT 2015, 14th IEEE International Conference on Ubiquitous Computing and Communications, IUCC 2015, 13th IEEE International Conference on Dependable, Autonomic and Secure Computing, DASC 2015 and 13th IEEE International Conference on Pervasive Intelligence and Computing, PICom 2015 1638 - 1645 2015年12月22日 
    We exploit the Degrees of Freedom (DoF) resulting from the deployment of multiple antennas, both at the Access Points (APs) and the clients, to address the Hidden Terminal problem in Multi User (MU) Multiple Input Multiple Output (MIMO) Wireless Local Area Networks (WLANs). This approach permits concurrent transmissions and is able to maintain a constant gain in network throughput in a Hidden Terminal scenario. We treat concurrent transmissions as an integral part of our design, so we adopt and extend the traditional Point Coordination Function (PCF) to manage them. Specifically, contention free period of the traditional PCF is used in uplink and downlink. In addition, based on DoF at APs, our MAC decides the Transmission Opportunity (TXOP) of APs/Transmitters in contrast to many traditional approaches. Besides, our MAC runs a concurrent algorithm at APs which forms an important part for the calculation of precoding vectors (based on the Zeroforcing) in the Physical Layer (PHY). Additionally, a seamless channel sounding process is designed to support the ZF precoding at the PHY which has 98.67μs signaling overhead, lower than IEEE802.11ac. Simulation studies in a typical 6-antenna AP and client scenario show that our MAC provides a remarkable constant network throughput gain of 4-5 times in comparison to traditional RTS/CTS, and a lower signaling overhead than IEEE802.11ac. Besides, our simple fairness algorithm provides a fair share in the throughput among APs, with the Jain Fairness Index greater than 90%.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang
    Eurasip Journal on Wireless Communications and Networking 2015 1 2015年12月01日 
    In this paper, we study the joint optimal relay location and power allocation problem for single-relay-assisted ultra-wideband (UWB)-based wireless body area networks (WBANs). Specifically, to optimize spectral efficiency (SE) for single-relay cooperative communication in UWB-based WBANs, we seek the relay with the optimal location together with the corresponding optimal power allocation. With proposed relay-location-based network models, the SE maximization problems are mathematically formulated by considering three practical scenarios, namely, along-torso scenario, around-torso scenario, and in-body scenario. Taking into account realistic power considerations for each scenario, the optimal relay location and power allocation are jointly derived and analyzed. Numerical results show the necessity of utilization of relay node for the spectral and energy-efficient transmission in UWB-based WBANs and demonstrate the effectiveness of the proposed scheme in particular for the around-torso and in-body scenarios. With the joint optimal relay location and power allocation, the proposed scheme is able to prolong the network lifetime and extend the transmission range in WBANs significantly compared to direct transmission.
  • Jie Zhou, Eryk Dutkiewicz, Ren Ping Liu, Xiaojing Huang, Gengfa Fang, Yuanan Liu
    IEEE Transactions on Broadcasting 61 4 698 - 709 2015年12月 
    Significant reduction of the peak-to-average power ratio (PAPR) is an implementation challenge in orthogonal frequency division multiplexing (OFDM) systems. One way to reduce PAPR is to apply a set of selected partial transmission sequence (PTS) to the transmit signals. However, PTS selection is a highly complex NP-hard problem and the computational complexity is very high when a large number of subcarriers are used in the OFDM system. In this paper, we propose a new heuristic PTS selection method, the modified chaos clonal shuffled frog leaping algorithm (MCCSFLA). MCCSFLA is inspired by natural clonal selection of a frog colony, it is based on the chaos theory. We also analyze MCCSFLA using the Markov chain theory and prove that the algorithm can converge to the global optimum. Simulation results show that the proposed algorithm achieves better PAPR reduction than using others genetic, quantum evolutionary and selective mapping algorithms. Furthermore, the proposed algorithm converges faster than the genetic and quantum evolutionary algorithms.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang, Gengfa Fang
    IEEE International Conference on Communications 2015-September 1559 - 1564 2015年09月09日 
    Energy efficiency is one of the most critical parameters in ultra-wideband (UWB) based wireless body area networks (WBANs). In this paper, the energy efficiency optimization problem is investigated for cooperative transmission with a single relay in UWB based WBANs. Two practical onbody transmission scenarios are taken into account, namely, along-torso scenario and around-torso scenario. With a proposed single-relay WBAN model, a joint optimal scheme for the energy efficiency optimization is developed, which not only derives the optimal power allocation but also seeks the corresponding optimal relay location for each scenario. Simulation results show that the utilization of a relay node is necessary for the energy efficient transmission in particular for the around-torso scenario and the relay location is an important parameter. With the joint optimal relay location and power allocation, the proposed scheme is able to achieve up to 30 times improvement compared to direct transmission in terms of the energy efficiency when the battery of the sensor node is very limited, which indicates that it is an effective way to prolong the network lifetime in WBANs.
  • Jian A. Zhang, Xiaojing Huang, Y. Jay Guo
    2015 IEEE International Conference on Communication Workshop, ICCW 2015 1095 - 1100 2015年09月08日 
    Angle-of-Arrival estimation in localized hybrid array is very challenging due to the phase ambiguity problem. A differential beam searching (DBS) algorithm was proposed to solve the problem. However, it converges slowly and suffers from a zigzag effect where estimates may jump between correct and wrong estimates. In this paper, we first propose an improved DBS algorithm to mitigate the zigzag effect. We then analyze the error sources for general DBS algorithms, and propose a new adaptive searching and tracking (AST) algorithm. By using carefully designed updating functions and exit conditions, the proposed AST algorithm allows automatic switching between searching and tracking modes, and can significantly speed up estimation process and reduce estimation error. Numerical results are provided to verify the effectiveness of the proposed schemes.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang, Gengfa Fang
    IEEE Vehicular Technology Conference 2015 2015年07月01日 
    In this paper, we investigate a distributed beamforming problem to optimize energy efficiency (EE) in ultra-wideband (UWB) based implant body area networks (IBANs). To evaluate the impact of relay location on the EE, a relay location based cooperative network model is proposed, where multiple on-body relays are employed to assist an implant node to communicate with a BAN coordinator. With the proposed model, the EE optimization problem is mathematically formulated as a non-convex optimization problem. Sequential quadratic programming (SQP) combined with scatter search are applied to find the corresponding optimal solution. Simulation results illustrate that the proposed beamforming scheme outperforms other transmission schemes. A remarkable improvement can be achieved not only in EE but also in spectral efficiency (SE) compared to direct transmission. Moreover, numerical examples show that the relay location has a significant impact on the EE performance.
  • Sanjeeb Shrestha, Gengfa Fang, Eryk Dutkiewicz, Xiaojing Huang
    2015 22nd International Conference on Telecommunications, ICT 2015 283 - 288 2015年06月16日 
    This paper focuses on the Medium Access Control (MAC) layer design for an inevitable Hidden Terminal problem in Multi User Multiple Input Multiple Output (MU-MIMO) Wireless Local Area Networks (WLANs). Specifically, our MAC design is supported by the precoding vectors obtained by Zeroforcing technique which are used to address the Hidden Terminals. An efficient channel sounding process is used by our MAC protocol to obtain the Channel State Information (CSI) from the desired and undesired clients which are used to calculate the precoding vectors at the transmitters (Access Points). Our MAC design then uses these precoding vectors in order to null interferences among the undesired clients to avoid collision of signals and to maintain the concurrent transmissions among the desired clients. The the parameters such as network capacity, signaling overheads and fairness are considered in the design. Our MAC layer design shows a slightly higher signaling overhead compared to RTS/CTS scheme. However, due to the concurrent transmissions after the handshaking process, the cost of singling overheads are compensated. The simulation study of our MAC layer design shows a remarkable constant network capacity gain of 4-5 times in comparison to traditional RTS/CTS. Moreover, the gain is irrespective to the available air-time.
  • Xiaojing Huang, Jian A. Zhang, Y. Jay Guo
    IEEE Communications Magazine 53 6 151 - 159 2015年06月01日 
    OFDM has been regarded as a promising candidate for use in cognitive radio systems with dynamic spectrum reuse capability. However, conventional OFDM has significant OOBE, which can cause severe interference to systems operating in adjacent frequency bands. In addition to conventional techniques such as spectral shaping filtering, guard band insertion, and time domain windowing, new OOBE reduction techniques, including cancellation carrier and spectral precoding, have been proposed in recent years. This article reviews various OOBE reduction techniques and proposes a generalized lowcomplexity OOBE reduction framework for discrete Fourier transform precoded OFDM. With the allocation of explicit frequency domain cancellation subcarriers and data domain cancellation symbols, the proposed framework enables various configurations to achieve significant OOBE reduction with low implementation complexity, and provides flexibility in balancing OOBE reduction and other performance metrics such as peak-to-average power ratio.
  • Rowan Gilmore, Xiaojing Huang, Richard Harris
    Australian Journal of Telecommunications and the Digital Economy 3 1 1 - 15 2015年03月 
    Fibre is commonly perceived to be the dominant transport mechanism for transferring data from access points back to a central office, where it is aggregated onto the core network. However, high speed and long range wireless backhaul remains a cost-effective alternative to fibre networks. In some areas, wireless backhaul is dominant and becoming more and more attractive. However, commercially available wireless backhaul systems do not meet the requirements for both high speed and long range at the same time with sufficiently low latency for some applications. Traditional microwave systems can achieve long transmission range, but the data rates are then limited to a few hundred megabits per second. Multi-gigabit per second wireless communications can be achieved using millimetre-wave (mm-wave) frequency bands, especially in E-band, but the practical transmission range has then always been a major weakness. In this article, the world's first 5Gbps radio solution' and the fastest commercial backhaul product - developed by EM Solutions Pty Ltd with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) - is described. As well as achieving a state-of-the-art data rate, other key design features include maximal path length, minimal latency, and constant antenna pointing under wind and tower vibration.
  • Jian A. Zhang, Xiaojing Huang, Val Dyadyuk, Y. Jay Guo
    IEEE Wireless Communications 22 1 79 - 87 2015年02月01日 
    A massive hybrid array consists of multiple analog subarrays, with each subarray having its digital processing chain. It offers the potential advantage of balancing cost and performance for massive arrays and therefore serves as an attractive solution for future millimeter-wave (mm- Wave) cellular communications. On one hand, using beamforming analog subarrays such as phased arrays, the hybrid configuration can effectively collect or distribute signal energy in sparse mm-Wave channels. On the other hand, multiple digital chains in the configuration provide multiplexing capability and more beamforming flexibility to the system. In this article, we discuss several important issues and the state-of-the-art development for mm-Wave hybrid arrays, such as channel modeling, capacity characterization, applications of various smart antenna techniques for single-user and multiuser communications, and practical hardware design. We investigate how the hybrid array architecture and special mm-Wave channel property can be exploited to design suboptimal but practical massive antenna array schemes. We also compare two main types of hybrid arrays, interleaved and localized arrays, and recommend that the localized array is a better option in terms of overall performance and hardware feasibility.
  • Jie Zhou, Eryk Dutkiewicz, Ren Ping Liu, Gengfa Fang, Yuanan Liu, Xiaojing Huang
    IEEE Region 10 Annual International Conference, Proceedings/TENCON 2015-January 2015年01月26日 
    Reducing peak-to-average power ratio (PAPR) is an implementation challenge in orthogonal frequency division multiplexing (OFDM) systems. One way to reduce PAPR is to apply a set of selected partial transmission sequence (PTS) to the transmit signals. However, PTS selection is a highly complex NP-hard problem and the computational complexity is very high when a large number of subcarriers are used in the OFDM system. In this paper, we propose a new heuristic PTS selection method, the modified chaos clonal shuffled frog leaping algorithm (MCCSFLA-PTS). The MCCSFLA-PTS is inspired by natural clonal selection of frog colony and based on chaos theory. Simulation results show that the proposed MCCSFLA-PTS achieves better PAPR reduction than genetic, quantum evolutionary and selective mapping algorithms. Furthermore, the proposed algorithm converges faster than the genetic and quantum evolutionary algorithms.
  • Sanjeeb Shrestha, Gengfa Fang, Eryk Dutkiewicz, Xiaojing Huang
    14th International Symposium on Communications and Information Technologies, ISCIT 2014 249 - 253 2015年01月15日 
    We present here a new technique that can be used to address a well-known Hidden Terminal problem in Wireless Local Area Networks. Specifically, Zero Forcing Coordinated Beamforming can be applied, in a hidden terminal scenario, in order to null the signal of the interfering transmitter so that desired transmission can take place without collision at the receiver. Basically, a precoding range of a receiver is used as a determinant in order to take a nulling decisions based on the notion that a successful transmission depends on the interference free condition at the receiver. We demonstrate the feasibility of the approach in an USRP2/GNURadio test-bed prototype. Our scheme improves the SNR and Effective SNR from about 5 to 11 dB in a hidden terminal scenario and maintains collision free simultaneous transmissions.
  • Xiaojing Huang, Y. Jay Guo, Jian A. Zhang
    14th International Symposium on Communications and Information Technologies, ISCIT 2014 542 - 546 2015年01月15日 
    High speed and long range wireless backhauls are cost-effective alternatives to fibre networks and becoming more and more attractive as the demand for broadband wireless services grows rapidly in recent years. However, current commercially available wireless backhaul systems neither provide sufficiently high speed nor meet the requirements to achieve both high speed and long range at the same time with sufficiently low latency for targeted applications. Traditional microwave systems can achieve long transmission range, but the data rates are limited to a few hundred Mega bits per second only. Multi-Gigabit wireless communications can be achieved using millimetre-wave (mm-wave) frequency bands, especially the E-bands, but the practical transmission range is still a major weakness. In this paper, the state-of-the-art microwave and mm-wave technologies developed at the Commonwealth Scientific and Industrial Research Organization (CSIRO) are introduced to demonstrate CSIRO's technology leadership in multi-Gigabit wireless communications research and development. The technology trends in multi-Gigabit wireless communications are also discussed and various recently developed microwave and mm-wave systems are compared. It is hoped that this paper will stimulate further research interest and industry development.
  • Jie Zhou, Eryk Dutkiewicz, Ren Ping Liu, Xiaojing Huang, Gengfa Fang, Yuanan Liu
    14th International Symposium on Communications and Information Technologies, ISCIT 2014 503 - 507 2015年01月15日 
    Orthogonal frequency division multiplexing (OFDM) is a leading technology in the field of broadband wireless communications. In OFDM systems, a high peak-to-average power ratio (PAPR) is a critical issue, which may cause a nonlinear distortion and reduce power efficiency. To reduce the PAPR, partial transmit sequences (PTS) technique can be applied to the transmit data. However, the phase factor sequence selection in PTS technique is a non-linear optimization problem and it suffers from high complexity and memory use when there is a large number of non-overlapping sub-blocks in one symbol. In this paper a novel modified elite chaotic artificial fish swarm algorithm for PTS method (MECAFSA-PTS) is proposed to generate the optimum phase factors. The MECAFSA-PTS method is evaluated with extensive simulations and its performance is compared with quantum evolutionary and selective mapping algorithms. Our results show that the proposed MECAFSA-PTS algorithm is efficient in PAPR reduction.
  • Xiaojing Huang, Jian A. Zhang, Y. Jay Guo
    2014 IEEE/CIC International Conference on Communications in China, ICCC 2014 523 - 527 2015年01月12日 
    This paper proposes a unified out-of-band emission (OOBE) reduction framework with linear complexity for orthogonal frequency-division multiplexing (OFDM) systems. Unlike conventional spectral precoding approaches which use orthogonal precoding matrixes, this framework composes cancellation signals from the linear combinations of data symbols and minimizes the average OOBE power with a general least-squares solution. A joint frequency domain cancellation subcarrier and data domain cancellation symbol allocation scheme is also proposed for discrete Fourier transform precoded OFDM, by which the overall signal processing complexity of the OFDM transceiver is further reduced without impact on other system performance. The advantages of the proposed scheme is verified both analytically and by simulation as compared with some well-known low-complexity OOBE reduction schemes.
  • Mohammad Sadegh Mohammadi, Eryk Dutkiewicz, Qi Zhang, Xiaojing Huang
    IEEE Communications Letters 18 12 2193 - 2196 2014年12月01日 
    We propose a novel link adaptation mechanism to maximize energy efficiency in IEEE 802.15.6 impulse radio ultra wideband (IR-UWB) wireless body area networks (WBANs). We consider noncoherent energy detection and autocorrelation receivers, suitable for low complexity implementations. The amount of captured energy is first modeled for the on-body WBAN channel. Using our energy capture model and Gaussian approximations for the decision statistic, the error performance of various physical layer modes of the IEEE 802.15.6 standard is derived assuming intra-symbol interference. We refer to the IEEE 802.15.6 specification as a use case. The proposed adaptation scheme can be applied to any other IR-UWB system with noncoherent receivers and is based on the estimated signal to noise ratio and the channel's energy capture index for which we propose unbiased estimators.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang, Gengfa Fang
    BODYNETS 2014 - 9th International Conference on Body Area Networks 32 - 38 2014年11月21日 
    In this paper, a distributed beamforming problem is investigated based on spectral efficiency (SE) optimization for ultra-wideband (UWB) based implant body area networks (IBANs). We consider a relay network consisting of one implant source, several wearable relays, and one body network coordinator under the assumption that the individual relay power is constrained due to the Federal Communications Commission (FCC) regulations for UWB signals. Taking into account realistic wireless channels and relay locations, the SE optimization problem is mathematically formulated and solved by using convex optimization. Simulation results show that the proposed beamforming scheme is superior to other transmission schemes. Moreover, our numerical examples reveal that the relay location has a significant impact on the beamforming performance and the proposed beamforming scheme provides an efficient way to prolong the lifetime of the implant node.
  • Mohammad Sadegh Mohammadi, Qi Zhang, Eryk Dutkiewicz, Xiaojing Huang
    IEEE Wireless Communications Letters 3 4 397 - 400 2014年08月 
    Energy efficiency is a major requirement in wireless body area networks (WBANs). In this letter, we optimize the length of the medium access control (MAC) frame body to maximize the energy efficiency in IEEE 802.15.6 ultra-wideband (UWB) WBANs. To achieve this, we derive the probability of packet detection as well as the probability of successful reception of the physical layer header and data payload for the two UWB physical layer modes i.e., the default mode and the high QoS mode. The analysis includes the impact of forward error correction and type II hybrid ARQ on the packet success rate. We further extend the existing model of energy efficiency by incorporating separate energy consumption costs for uplink and downlink channels as well as data transmission and reception. The correctness of the theoretical model is assessed and verified by means of system level simulations, and a closed form expression for optimal frame length is given for the default mode. © 2012 IEEE.
  • Jian A. Zhang, Wei Ni, John Matthews, Chang Kyung Sung, Xiaojing Huang, Hajime Suzuki, Iain Collings
    2014 IEEE International Conference on Communications Workshops, ICC 2014 592 - 597 2014年 
    Wireless backhaul is one of the main challenges in small cell deployment. Current wireless backhaul systems have one or more limitations on capacity, link distance and supporting line-of-sight (LOS) links. In this paper, we propose a novel two-tier small-cell backhaul architecture which provides a future-proof, powerful, flexible and scalable solution by using aggregation nodes and integrating sub-6GHz point-to-multipoint (P2MP) and point-to-point E-band links. In the bottom tier of the proposed architecture, local small cells are connected to an aggregation node by P2MP and low-cost mega bits per second (Mbps) E-band links; in the top tier, aggregation nodes are inter-connected by LOS giga bits per second (Gbps) E-band links. PHY and higher layer protocols, which integrate the three different links into a comprehensive solution, are introduced. Designs of devices used in the architecture, which are being developed in CSIRO, are provided. Novel techniques that have been developed for achieving low-latency are detailed. Simulation results show that the backhaul latency can be as low as a few microseconds when only E-band backhaul links are involved. © 2014 IEEE.
  • Xiaojing Huang, Jian A. Zhang, Y. Jay Guo
    2014 IEEE International Conference on Communications, ICC 2014 5932 - 5937 2014年 
    This paper proposes a comprehensive solution to reduce peak-to-average power ratio (PAPR), cancel out-of-band emission (OOBE), and alleviate the impact of phase noise for precoded orthogonal frequency-division multiplexing (OFDM) systems. Making use of the cancellation and pilot symbols and subcarriers in both data and frequency domains, this solution integrates a number of novel schemes to overcome OFDM's inherent drawbacks and mitigate practical impairments for high speed wireless communications. These schemes include a layered precoding structure, a low complexity OOBE cancellation using both data domain cancellation symbols and frequency domain cancellation subcarriers, and an effective phase noise compensation using data domain pilot symbols. The improved overall system performance of the proposed solution is verified by simulation results. © 2014 IEEE.
  • Jian A. Zhang, Xiaojing Huang
    2014 IEEE International Conference on Communications, ICC 2014 3359 - 3364 2014年 
    This paper investigates discrete Fourier Transform (DFT)-precoded OFDM systems (DFT-OFDM) for intensity modulated direct-detection optical communications. Such scheme can be used to support both single and multiple user communications. Two DFT-OFDM systems using real modulation and DC-biasing are proposed. Performance analysis based on signal-to-interference-and-noise ratio (SINR) is provided. Insights are provided for designing choices between different modulations, and between using DC-biasing and asymmetrical clipping approaches. Simulation results show that the proposed schemes largely outperform systems using asymmetrical clipping, particularly in the case of using higher order modulations. © 2014 IEEE.
  • Mohammad Sadegh Mohammadi, Qi Zhang, Eryk Dutkiewicz, Xiaojing Huang, Rein Vesilo
    Proceedings - IEEE Global Communications Conference, GLOBECOM 4014 - 4019 2014年 
    In this paper we address the problem of rate scheduling in the Impulse Radio (IR) ultra-wideband (UWB) wireless body area networks (WBANs) and the minimum energy required to stabilize the queuing system. Targeting low complexity WBAN applications, we assume noncoherent receivers based on energy detection and autocorrelation for all nodes. The coordinating node can minimize the average energy consumption of the system and achieve the queue backlog stability of the sensor nodes by controlling the number of pulses per symbol. We first illustrate the necessary and sufficient conditions of network stability for a multi-mode UWB system and then propose a feasible rate scheduling algorithm based on the Lyapunov optimization theory. The scheduling algorithm uses the instantaneous channel state information and the length of the local queue of all sensor nodes and can approach the optimal energy-delay tradeoff of the network. We apply our theoretical framework to the IR-UWB physical layer of the IEEE 802.15.6 standard and extract the optimal physical layer modes that can achieve the desired energy-delay tradeoff.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang
    BODYNETS 2013 - 8th International Conference on Body Area Networks 29 - 34 2013年10月29日 
    In this paper, we study the energy efficiency of single relay cooperative transmission for ultra-wideband (UWB) based in-body area networks (IBANs). A simple relay-based cooperative IBAN system model is introduced first. With a target threshold of the received signal-to-noise ratio (SNR), outage probabilities for direct and cooperative transmissions are derived respectively. Afterwards, the average energy consumption per bit is given for both transmission schemes. The optimal relay location for cooperation is also derived and analyzed to minimize the average bit energy consumption. Simulation verifies the analysis and shows that cooperative transmission can achieve a satisfactory improvement on energy efficiency compared with direct transmission over a range of relay locations for UWB based IBANs. The improvement is more significant with a higher SNR threshold or with the implanted sensor having a deeper depth inside the body.
  • Xianjun Yang, Xiaofeng Tao, Eryk Dutkiewicz, Xiaojing Huang, Y. Jay Guo, Qimei Cui
    IEEE Transactions on Wireless Communications 12 10 5087 - 5099 2013年10月 
    Recently, distributed data storage (DDS) for Wireless Sensor Networks (WSNs) has attracted great attention, especially in catastrophic scenarios. Since power consumption is one of the most critical factors that affect the lifetime of WSNs, the energy efficiency of DDS in WSNs is investigated in this paper. Based on Compressed Sensing (CS) and network coding theories, we propose a Compressed Network Coding based Distributed data Storage (CNCDS) scheme by exploiting the correlation of sensor readings. The CNCDS scheme achieves high energy efficiency by reducing the total number of transmissions Nttot and receptions Nrtot during the data dissemination process. Theoretical analysis proves that the CNCDS scheme guarantees good CS recovery performance. In order to theoretically verify the efficiency of the CNCDS scheme, the expressions for Nttot and Nrtot are derived based on random geometric graphs (RGG) theory. Furthermore, based on the derived expressions, an adaptive CNCDS scheme is proposed to further reduce N ttot and Nrtot. Simulation results validate that, compared with the conventional ICStorage scheme, the proposed CNCDS scheme reduces Nttot, Nrtot, and the CS recovery mean squared error (MSE) by up to 55%, 74%, and 76% respectively. In addition, compared with the CNCDS scheme, the adaptive CNCDS scheme further reduces Nttot and N rtot by up to 63% and 32% respectively. © 2002-2012 IEEE.
  • Xianjun Yang, Eryk Dutkiewicz, Qimei Cui, Xiaojing Huang, Xiaofeng Tao, Gengfa Fang
    IEEE International Conference on Communications 4941 - 4945 2013年 
    Recently, the recovery performance of analog Compressed Sensing (CS) has been significantly improved by representing multiband signals with the modulated and merged Slepian basis (MM-Slepian dictionary), which avoids the frequency leakage effect of the Discrete Fourier Transform (DFT) basis. However, the MM-Slepian dictionary has a very large scale and corresponds to a large-scale measurement matrix, which leads to high recovery computational complexity. This paper resolves the above problem by modulating and band-limiting the multiband signal rather than modulating the Slepian basis. Specifically, instead of using the MM-Slepian dictionary to represent the whole multiband signal, we propose to use the non-modulated Slepian basis to represent the modulated and band-limited version of the multiband signal based on the recently proposed Modulated Wideband Converter (MWC). Furthermore, based on the analytical derivation with the non-modulated Slepian basis, we propose an Interpolation Recovery (IR) algorithm to take full advantage of the Slepian basis, whereas the Direct Recovery (DR) algorithm using the Moore-Penrose pseudo-inverse cannot achieve this. Simulation results verify that, with low recovery computational load, the non-modulated Slepian basis combined with the IR algorithm improves the recovery SNR by up to 35 dB compared with the DFT basis in noise-free environment. © 2013 IEEE.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang, Daiming Qu, Tao Jiang
    Proceedings - IEEE Global Communications Conference, GLOBECOM 4192 - 4197 2013年 
    For non-contiguous (NC) OFDM based cognitive radio (CR) systems, schemes have been developed in literature to acquire spectrum synchronization information (SSI) with perfect carrier frequency offset (CFO) synchronization. However, OFDM is extremely sensitive to the CFO in practice, which leads to inter-carrier interference (ICI), hence degrading the spectrum synchronization performance for existing schemes. An accurate CFO estimation is therefore required before setting up the SSI. In this paper, we present a novel scheme based on the maximum likelihood (ML) algorithm to estimate the CFO for the NC-OFDM receiver when the SSI is unknown. A corresponding Cramér-Rao lower bound (CRB) with the ideal SSI is derived to demonstrate the efficiency of the proposed scheme. Simulation results show that the proposed scheme is robust against interference and achieves a satisfactory accuracy of estimation, which is close to the relevant CRB. © 2013 IEEE.
  • Jian A. Zhang, Xiaojing Huang, Hajime Suzuki, Zhuo Chen
    IEEE Transactions on Wireless Communications 12 3 1407 - 1417 2013年 
    Channel matrix inversion, which requires significant hardware resource and computational power, is a very challenging problem in MIMO-OFDM systems. Casting the frequency-domain channel matrix into a polynomial matrix, interpolation-based matrix inversion provides a promising solution to this problem. In this paper, we propose novel algorithms for interpolation based matrix inversion, which require little prior information of the channel matrix and enable the use of simple low-complexity interpolators such as spline and low pass filter interpolators. By invoking the central limit theorem, we show that a Gaussian approximation function well characterizes the power of the polynomial coefficients. Some low-complexity and efficient schemes are then proposed to estimate the parameters of the Gaussian function. With these estimated parameters, we introduce phase shifted interpolation and propose two algorithms which can achieve good interpolation accuracy using general low-complexity interpolators. Simulation results show that up to 85% complexity saving can be achieved with small performance degradation. © 2002-2012 IEEE.
  • Yifei Huang, Xiaojing Huang
    IEEE Transactions on Wireless Communications 12 3 1290 - 1299 2013年 
    An optimal detection method along with two reduced-complexity methods, modified energy detection (MED) and equal gain detection (EGD), under low signal-to-noise ratio (SNR) condition are proposed in this paper for detection of temporally correlated signals over multipath fading channels. By incorporating resolvable multipaths and multiple antennas into system model, these detection methods are derived based on maximum log-likelihood ratio (LLR) test principal and using the same low SNR LLR approximation. Analytical performance expressions for MED and EGD are also given. Simulation results show that, when signal exhibits temporal correlation, the proposed optimal detection and EGD achieve better performance than conventional generalized likelihood ratio test through utilizing multipath propagation. Further, the proposed MED is superior to conventional energy detection if it a priori signal temporal correlation information is exploited. It is also revealed that multipath tap correlation can have either constructive or destructive effect to spectrum sensing. The proposed EGD is proven to be a practical technique for reliable spectrum sensing over multipath fading channels as it approaches optimal performance with low complexity. © 2002-2012 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck
    IEEE Transactions on Wireless Communications 12 4 1783 - 1793 2013年 
    This paper presents a novel downlink resource allocation scheme for OFDMA-based next generation wireless networks subject to inter-cell interference (ICI). The scheme consists of radio resource and power allocations, which are implemented separately. Low-complexity heuristic algorithms are first proposed to achieve the radio resource allocation, where graph-based framework and fine physical resource block (PRB) assignment are performed to mitigate major ICI and hence improve the network performance. Given the solution of radio resource allocation, a novel distributed power allocation is then performed to optimize the performance of cell-edge users under the condition that desirable performance for cell-center users must be maintained. The power optimization is formulated as an iterative barrier-constrained water-filling problem and solved by using the Lagrange method. Simulation results indicate that our proposed scheme can achieve significantly balanced performance improvement between cell-edge and cell-center users in multi-cell networks compared with other schemes, and therefore realize the goal of future wireless networks in terms of providing high performance to anyone from anywhere. © 2002-2012 IEEE.
  • Jian A. Zhang, Lin Luo, Xiaojing Huang
    IEEE Signal Processing Letters 20 7 665 - 668 2013年 
    This letter extends our previous work on layered inverse Fast Fourier Transform (IFFT) structure to a multistage layered IFFT structure where data symbols can input at different stages of the IFFT. We first show that part of the IFFT in the transmitter of an OFDM system can be shifted to the receiver, while a conventional one-tap frequency-domain equalizer is still applicable. We then propose two IFFT split schemes based on decimation-in-time and decimation-in-frequency IFFT algorithms to enable interference-free symbol recovery with simple linear equalizers. Applications of the proposed schemes in multiple access communications are investigated. Simulation results demonstrate the effectiveness of the proposed schemes in improving bit-error-rate performance. © 1994-2012 IEEE.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang
    International Symposium on Medical Information and Communication Technology, ISMICT 28 - 32 2013年 
    For impulse radio ultra wideband (IR-UWB) based wireless body area network (WBAN) systems, one of the significant challenges is to guarantee a reliable link for data transmission. For this purpose, in this paper, we develop a simple but effective virtual MIMO (VMIMO) based cooperative diversity scheme for a single antenna transmitter being aided by an amplify-and-forward (AF) relay. To the best of our knowledge, this is the first paper where performance of VMIMO is evaluated in IR-UWB based WBAN systems. The theoretical analysis reveals that VMIMO not only offers a full spatial diversity, but also can collect the multipath diversity contained in the dense WBAN channels. Preliminary simulation results show that VMIMO can provide a considerable improvement on bit error rate (BER) performance compared with the single-input single-output (SISO) WBAN systems. © 2013 IEEE.
  • Xiaojing Huang, Jayasri Joseph, Jian A. Zhang, Y. Jay Guo
    IEEE Wireless Communications and Networking Conference, WCNC 2754 - 2759 2013年 
    Based on the sequential sample rate conversion (SRC) structure using B-spline interpolation for orthogonal frequency division multiplexing (OFDM) based software defined radios, a parallel processing SRC structure is proposed in this paper to achieve high speed data transmission for multiband OFDM systems. By deriving an impulse response matrix from the sequential SRC structure, the state vectors of the SRC structure can be calculated from a block of input samples with less complexity than conventional Farrow structure. Real-time SRC implementation combined with local feedback and stuffing is also presented. Performance in terms of state buffer pointer offset caused by clock variation and finite precision in digital hardware is analyzed to provide guidance for practical system design such as determining clock stability and word-length requirements. © 2013 IEEE.
  • Antonio Cantoni, Jian Zhang, Xiaojing Huang, Yingjie Jay Guo
    IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC 629 - 633 2013年 
    We recently proposed an efficient 'sidelobe suppression with orthogonal projection' (SSOP) scheme for reduction of out-of-band emission of OFDM signals. The SSOP scheme uses a preceding matrix to generate zeros at prescribed frequencies in the sidelobe region and it is numerically observed that its suppression effect is affected by the sampling rate. In this paper, we analytically characterize this effect by considering analog and digital implementations of the SSOP scheme, which correspond to a zero sampling rate and an IFFT implementation with non-zero sampling rates, respectively. Both implementations are modeled and analytical expressions for the corresponding spectra are developed. It is shown that the analytical results match the simulation results very well and the suppression performance is generally proportional to the sampling rate. The analog SSOP-OFDM has true zeros at prescribed frequencies and thus results in significant reduction of out-of-band emissions. The digital implementation does not result in true zeros in the spectrum but nevertheless results in significant sidelobe reduction if the frequency resolution associated with the IFFT is sufficiently high. © 2013 IEEE.
  • Jie Ding, Eryk Dutkiewicz, Xiaojing Huang, Gengfa Fang
    2013 IEEE International Conference on Ultra-Wideband, ICUWB 2013 97 - 102 2013年 
    In this paper, an energy-efficient cooperative relay selection scheme is investigated for ultra-wideband (UWB) based wireless body area networks (WBANs). With a realistic nonlinear energy consumption model, the energy consumption for single-relay cooperation is established and the optimal power allocation for cooperation is derived accordingly to minimize the total energy consumption at a given relay location. Afterwards, an energy efficient relay selection criterion is described in detail. Simulation results verify the suitability of the criterion and show that, with the same desired spectral efficiency (SE), direct transmission is preferable for energy saving when the transmitter and receiver are located on the same side of the human body. However, at a suitable relay location and with large transmission distance, cooperative transmission can achieve a significant improvement on energy efficiency compared with direct transmission when the transmitter and receiver are located on the different sides of the human body. © 2013 IEEE.
  • X. Yang, X. Tao, Y. J. Guo, X. Huang, Q. Cui
    Electronics Letters 48 13 767 - 768 2012年06月21日 
    The modulated wideband converter (MWC) is an attractive analogue compressed sensing technique proposed recently. Unfortunately, the MWC has high hardware complexity owing to its parallel structure. To reduce the complexity, proposed is a novel subsampled circulant matrix based analogue compressed sensing (SCM-ACS) scheme. Using the cyclic shifts of the Zadoff-Chu sequence, the SCM-ACS scheme reduces the number of physical parallel channels from m to 1 with larger processing time, where m ranges from several dozen to several hundred. It is proved that when m=O(r log 2 M log 3 r) the measurement matrix of the SCM-ACS scheme satisfies the restricted isometry property condition with probability 1-M -O(1), where M is the length of the Zadoff-Chu sequence, and r is the sparsity of the input signal. Simulation results show that the SCM-ACS scheme outperforms the MWC on recovery performance. © 2012 The Institution of Engineering and Technology.
  • Peng Cheng, Lin Gui, Yun Rui, Y. Jay Guo, Xiaojing Huang, Wenjun Zhang
    IEEE Wireless Communications Letters 1 3 201 - 204 2012年06月 
    In this letter, a novel channel estimation scheme based on compressed sensing (CS) theory is proposed for two-way relay networks (TWRN) in sparse frequency-selective fading channels. Unlike point-to-point systems, applying CS theory to sparse channel estimation in TWRN is much more challenging since the equivalent channels (terminal-relay-terminal) may be no longer sparse due to the linear convolutional operation. To solve this problem, instead of directly estimating the equivalent channels, a linear precoding based method is designed to firstly separate the individual channels between the terminals and the relay from the equivalent channels. CS theory is then applied to the time-domain channel estimation with much smaller number of pilot symbols. This scheme enables accurate channel estimation for TWRN with significant overhead reduction. Extensive numerical results are provided to substantiate the effectiveness of the proposed method. © 2012 IEEE.
  • Xiaojing Huang, Y. Jay Guo, Andrew Zhang, Val Dyadyuk
    IEEE Communications Magazine 50 3 122 - 129 2012年03月 
    The rapid growth of multimedia broadband wireless services has placed huge pressure on the backhaul infrastructure. As cost-effective alternatives to fibre backhauls, high speed microwave backhauls provide a number of significant benefits, especially for bringing broadband services to rural and regional areas. This article addresses the challenges to wireless backhauls and presents a multi-gigabit microwave backhaul system, called Ngara backhaul, which is being developed at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia. The various innovative aspects of the Ngara backhaul system including spectrum aggregation, peak-toaverage power ratio reduction, out-of-band emission cancellation, and sample rate conversion, are reported. © 2012 IEEE.
  • Jian Zhang, Xiaojing Huang
    IEEE Transactions on Wireless Communications 11 2 526 - 530 2012年02月 
    Two novel differential normalization factors, depending on the severity of carrier frequency offset, are proposed for autocorrelation based coarse timing scheme. Compared with the conventional normalization factor based on signal energy, they improve the robustness of the timing metric to signal-to-noise ratio (SNR), improve the mainlobe sharpness of the timing metric and reduce both missed detection and false alarm probabilities. © 2012 IEEE.
  • Jian Zhang, Xiaojing Huang, Antonio Cantoni, Y. Jay Guo
    IEEE Transactions on Communications 60 2 589 - 599 2012年02月 
    Sidelobe suppression, or out-of-band emission reduction, in multicarrier systems is conventionally achieved via time-domain windowing which is spectrum inefficient. Although some sidelobe cancellation and signal predistortion techniques have been proposed for spectrum shaping, they are generally not well balanced between complexity and suppression performance. In this paper, an efficient and low-complexity sidelobe suppression with orthogonal projection (SSOP) scheme is proposed. The SSOP scheme uses an orthogonal projection matrix for sidelobe suppression, and adopts as few as one reserved subcarrier for recovering the distorted signal in the receiver. Unlike most known approaches, the SSOP scheme requires multiplications as few as the number of subcarriers in the band, and enables straightforward selection of parameters. Analytical and simulation results show that more than 50dB sidelobe suppression can be readily achieved with only a slight degradation in receiver performance. © 2012 IEEE.
  • Xiaojing Huang, Y. Jay Guo, Val Dyadyuk
    Telecommunications Journal of Australia 62 1 2012年 
    With the emergence of next generation broadband wireless access and mobile systems, huge demands are being placed on the backhaul infrastructure. As cost-effective alternatives to traditional copper and fibre backhauls, high speed and long range wireless backhauls become more and more attractive. However, current existing wireless backhaul systems neither provide sufficiently high speed nor meet the requirements to achieve both high speed and long range at the same time. Multi-gigabit data rates can be obtained using millimetre-wave (mmwave) point-to-point systems, but the practical transmission range is still the major weakness. Traditional microwave systems can achieve longer transmission range, but the data rates are limited to a few hundred Mega bits per second only. In this article, a review on the demand for multi-gigabit wireless backhauls is given and the benefits of wireless backhauls are described. The radio propagation characteristics in both mm-wave and microwave frequency bands are provided to show the difference in transmission range for wireless backhauls in the two different bands. The state-of-the-art mm-wave and microwave technologies currently being developed at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) are introduced to illustrate CSIRO's technology leadership in high speed and long range broadband wireless backhaul systems. It is hoped that the article will stimulate further research interest and industry development.
  • Xianjun Yang, Y. Jay Guo, Qimei Cui, Xiaofeng Tao, Xiaojing Huang
    Proceedings - IEEE Global Communications Conference, GLOBECOM 3605 - 3609 2012年 
    Analog Compressed Sensing (CS) has attracted considerable research interest in sampling area. One of the promising analog CS technique is the recently proposed Modulated Wideband Converter (MWC). However, MWC has a very high hardware complexity due to its parallel structure. To reduce the hardware complexity of MWC, this paper proposes a novel Random Circulant Orthogonal Matrix based Analog Compressed Sensing (RCOM-ACS) scheme. By circularly shifting the periodic mixing function, the RCOM-ACS scheme reduces the number of physical parallel channels from m to 1 at the cost of longer processing time, where m is in the order of several dozen to several hundred in MWC. It is proved that the m×M measurement matrix of RCOM-ACS scheme satisfies the Restricted Isometry Property (RIP) condition with probability 1-M -O(1) when m = O(rlog2Mlog3r), where M is the length of the periodic mixing function, r denotes the sparsity of the input signal. Furthermore, to make a good tradeoff between processing time and hardware complexity, a short processing time RCOM-ACS scheme is proposed in this paper. Simulation results show that, the proposed schemes outperform MWC in terms of recovery performance. © 2012 IEEE.
  • Antonio Cantoni, Jian Zhang, Xiaojing Huang, Y. Jay Guo
    2012 Australian Communications Theory Workshop, AusCTW'12 37 - 42 2012年 
    Sidelobe suppression, or out-of-band emission reduction, in OFDM systems can be achieved via time-domain windowing but this may result in significantly reduced spectrum efficiency. Alternatively, sidelobe cancellation and signal predistortion techniques have been proposed for spectrum shaping, but schemes achieving a good balance between complexity and performance are yet to be developed. In this paper, an efficient and low-complexity technique referred to as "sidelobe suppression with orthogonal projection" (SSOP) scheme is proposed. An analysis of the SNR performance and robustness characteristics of the proposed technique are also presented. Numerical results show that significant sidelobe suppression can be readily achieved with slight receiver performance degradation. © 2012 IEEE.
  • Xiaojing Huang, Y. Jay Guo, Jian Zhang
    IEEE Transactions on Communications 60 8 2113 - 2122 2012年 
    This paper proposes arbitrary ratio sample rate conversion (SRC) architectures and a simpler B-spline interpolation algorithm for orthogonal frequency division multiplexing (OFDM) based software defined radios (SDRs) with multiband and multi-channel capabilities. Different from conventional standalone digital front-end designs for SDRs, the proposed SRC architectures combine the B-spline interpolation with OFDM modulation and equalization for OFDM transmitter and receiver respectively. With this combined design, the passband droop introduced by the B-spline interpolation can be more efficiently compensated using frequency-domain pre-distortion, instead of conventional time-domain pre-filtering, and hence an overall system complexity reduction is achieved. A novel multi-period B-spline interpolation and re-sampling structure is then constructed, and an interpolation algorithm with lower implementation complexity than that of the conventional Farrow structure is further developed. The SRC performance is also analysed by deriving the signal-to-peak distortion ratio formulas which can be used as design tools for determining the required orders of B-splines in the OFDM transmitter and receiver respectively. Finally, SRC examples used in a high-speed multiband multi-channel microwave backhaul system are given and compared with conventional polyphase filterbank interpolation to demonstrate the practicality and performance of the proposed SRC architectures and interpolation algorithm. © 1972-2012 IEEE.
  • Y. Jay Guo, Xiaojing Huang, Val Dyadyuk
    IEEE Antennas and Propagation Magazine 54 2 271 - 282 2012年 
    Owing to the availability of wide (GHz) bandwidth at mm-wave frequencies, there is growing interest in high-speed mm-wave communications systems. However, the limited physical size and volume of the antenna and RF system do pose several major challenges. This article presents CSIRO's research on hybrid adaptive antenna arrays and associated digital-beamforming algorithms for achieving high-speed long-range communications in the millimeter-wave frequency bands. The hybrid antenna array consists of a number of analog subarrays, followed by a digital beamformer. Two subarray configurations - the interleaved subarray and the side-by-side subarray - are described. The adaptive angle-of-arrival (AoA) estimation and beamforming algorithms in both the time and frequency domains are discussed. The performance of the system was evaluated by simulations. An early stage proof-of-concept adaptive antenna array prototype in the 71 to 76 GHz E band is presented. © 2011 IEEE.
  • Jian Zhang, Xiaojing Huang, Hajime Suzuki
    IEEE Communications Letters 16 9 1466 - 1469 2012年 
    This letter proposes simple algorithms for computing a phase shift term, which is introduced to greatly improve the accuracy of complex signal interpolation, applicable to any interpolator. Based on a cost function targeting at minimizing the phase transition between adjacent samples, the phase shift term can be easily computed using either signal statistics obtained in advance or known base samples in real time. Simulation results, exemplified for channel interpolation in OFDM systems, show that the proposed phase estimators can significantly improve the interpolation performance for various interpolators such as spline, low-pass filter, and linear and cubic polynomial interpolators, compared to the case without phase shifting. © 2012 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck
    IEEE Wireless Communications and Networking Conference, WCNC 1630 - 1635 2012年 
    In this paper we propose a novel resource allocation scheme to achieve a balanced performance improvement for all users in a LTE network subject to inter-cell interference. In the proposed scheme the resource allocation process is implemented in two steps. In the first step interference coordination and scheduling are first conducted in a global manner to prevent cell-edge users from mutual interference. In the second step, optimal power allocation is conducted to maximize performance of cell-edge users while maintaining high performance of cell-center users. The optimal power allocation problem is solved using the Lagrange decomposition method. Simulation results show that our proposed scheme can significantly improve performance for all users in a multi-cell network and achieve a better performance balance between cell-edge and cell-center users. © 2012 IEEE.
  • Jian Zhang, Antonio Cantoni, Xiaojing Huang, Y. Jay Guo
    IEEE International Conference on Communications 3959 - 3963 2012年 
    A low-complexity and efficient sidelobe suppression with orthogonal projection (SSOP) scheme is proposed in [1] for OFDM systems. This paper provides comprehensive performance analysis for the zero-forcing receiver for the SSOP scheme. Via rigorous proof, we show the independence of the orthogonal projection matrix on the ordering of the suppression distances, and the monotonicity of the SNR with the suppression distance and the number of reserved subcarriers. We also characterized the SNR degradation of the single-side and double-side suppression schemes analytically. These analytical results match with the numerical results well. © 2012 IEEE.
  • Yifei Huang, Xiaojing Huang
    IEEE International Conference on Communications 1522 - 1527 2012年 
    Wireless propagation phenomena including multipath pose significant challenges to reliable spectrum sensing which is a fundamental requirement for dynamic spectrum access and system coexistence. In this paper, an optimal detection technique along with two reduced-complexity alternatives, modified energy detection (MED) and equal gain detection (EGD), are proposed to improve the detection probability for spectrum sensing over severe multipath channels. By incorporating the resolvable multipaths and multiple receiving antennas into the system model and assuming the availability of a priori temporal correlation about the source signal, these detection methods are derived based on maximum log-likelihood ratio test under low signal-to-noise ratio condition. Simulation results show that the proposed optimal detection outperforms the conventional generalized likelihood ratio test in a multipath environment either with or without a priori information. The proposed MED significantly improves the performance of conventional energy detection after a priori information is exploited. Finally, the proposed EGD performs better than MED and approaches the optimal detection as the number of multipaths increases. © 2012 IEEE.
  • Yifei Huang, Xiaojing Huang
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2143 - 2148 2012年 
    Reliable spectrum sensing should be able to operate under realistic wireless environments such as multipath and fading. Based on the optimal spectrum sensing with multiple receiver antennas over multipath channels, this paper presents further studies into two more practical detection methods, the modified energy detection (MED) and the equal gain detection (EGD), over frequency-selective fading channels, with focus on the impact of multipath tap correlation on the sensing performance. Both simulation and analytical results are provided. It is verified that utilizing multipath propagation enhances the detection probability of the EGD, which approaches that of the optimal detection. The EGD also demonstrates better performance than the MED and the conventional generalized likelihood ratio test. The tap correlation can have either constructive or destructive effect to the spectrum sensing system depending on how well the tap correlation matches the source signal's temporal correlation, whereas the spatial correlation always degrades the detection performance. © 2012 IEEE.
  • Jian Zhang, Xiaojing Huang, Hajime Suzuki, Zhuo Chen
    IEEE International Conference on Communications 3831 - 3835 2012年 
    Channel matrix inversion, which requires significant hardware resource and computational power, is a very challenging problem in MIMO-OFDM systems. Casting the frequency-domain channel matrix into a polynomial matrix, interpolation-based matrix inversion provides a promising solution to this problem. In this paper, by showing that the polynomial coefficients can be well approximated by a Gaussian function, we propose an efficient algorithm, which relaxes the requirement for knowing the maximum multipath delay spread and enables the use of simple low-complexity interpolators by introducing a phase shift term to the signal to be interpolated. Simulation results show that significant complexity saving can be achieved with little equalization performance degradation. © 2012 IEEE.
  • Peng Cheng, Lin Gui, Meixia Tao, Y. Jay Guo, Xiaojing Huang, Yun Rui
    IEEE International Conference on Communications 3948 - 3953 2012年 
    Compressed sensing (CS) has recently emerged as a powerful signal acquisition paradigm. CS enables the recovery of high-dimensional sparse signals from much fewer samples than usually required. Further, quite a few recent channel measurement experiments show that many wireless channels also tend to exhibit sparsity. In this case, CS theory can be applicable to sparse channel estimation and its effectiveness has been validated in point-to-point (P2P) communication. In this work, we study sparse channel estimation for two-way relay networks (TWRN). Unlike P2P systems, applying CS theory to sparse channel estimation in TWRN is much more challenging. One issue is that the equivalent channels (terminal-relay-terminal) may be no longer sparse due to the linear convolutional operation. On this basis, novel schemes are proposed to solve this problem and effectively improve the accuracy of TWRN channel estimation when using CS theory. Extensive numerical results are provided to corroborate the proposed studies. © 2012 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck
    2012 International Symposium on Communications and Information Technologies, ISCIT 2012 991 - 996 2012年 
    This paper presents a novel power allocation approach for soft frequency reuse (SFR) adopted in a multi-cell LTE network. Based on the fact that major inter-cell interference (ICI) is coordinated by SFR, the proposed power allocation focuses on dealing with mutual interference between cell-edge and cell-center users in the network. It is formulated as an optimization problem, where the performance of cell-edge users is optimized under the condition that desirable performance must be maintained for cell-center users. The optimal solution can be obtained by using the Lagrange decomposition method. Simulation results show that our approach can significantly improve performance of cell-edge users by achieving 20% gain over conventional SFR with average power allocation when higher performance for cell-center users is maintained. © 2012 IEEE.
  • Ying He, Yongtao Su, Eryk Dutkiewicz, Xiaojing Huang, Jinglin Shi
    2012 International Symposium on Communications and Information Technologies, ISCIT 2012 444 - 448 2012年 
    An efficient hardware-optimized uplink baseband signal generation algorithm and its ASIC implementation in the LTE user equipment (UE) transmitter are presented in this paper. Optimization covers top level as well as module level. A paralleled Turbo encoder and a Cooley-Tukey based DFT are proposed. The optimized algorithm achieves significantly lower computational complexity compared with the original algorithm in the LTE specification and better performance compared to the existing results. The ASIC architecture is designed to reduce the logic complexity and implemented in 55nm CMOS, which achieves short time latency and low hardware cost in terms of the cell area. © 2012 IEEE.
  • Xianjun Yang, Eryk Dutkiewicz, Qimei Cui, Xiaofeng Tao, Y. Jay Guo, Xiaojing Huang
    2012 International Symposium on Communications and Information Technologies, ISCIT 2012 816 - 821 2012年 
    Distributed storage plays a very important role in Wireless Sensor Networks (WSNs), especially in catastrophic scenarios. To improve the energy efficiency of distributed storage, this paper proposes a Compressed Network Coding based Distributed Storage (CNCDS) scheme. Exploiting the correlation of sensor readings and utilizing the Compressed Sensing (CS) theory and network coding technology, the proposed CNCDS scheme achieves good energy efficiency by reducing the number of transmissions and receptions. Theoretical analysis proves that, the measurement matrix of CNCDS scheme guarantees good CS recovery performance. Simulation results show that, compared with the conventional ICStorage scheme, the proposed CNCDS scheme reduces the number of transmissions, the number of receptions and the CS recovery mean squared error (MSE) by up to 55%, 74% and 76% respectively. In contrast to the conventional NICStorage scheme, the proposed CNCDS scheme can simultaneously reduce the number of transmissions, receptions and recovery MSE. © 2012 IEEE.
  • K. Clare Xu, Eryk Dutkiewicz, Xiaojing Huang, Y. Jay Guo
    2012 International Symposium on Communications and Information Technologies, ISCIT 2012 1055 - 1059 2012年 
    A novel wireless positioning method employing an array of sensors which are capable of doing range estimates is proposed. Collectively, all the sensors in the sensor array can produce the direction of arrival (DoA) and the range information of mobile targets. To improve the positioning accuracy, it is proposed to introduce co-operations between the sensor arrays. Theoretical analysis and simulation results show that the use of the co-operation can increase the positioning accuracy significantly. Compared with other known methods, the proposed method does not require any phase measurement in the sensor arrays, so the system is relatively easy to operate and maintain. © 2012 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    IEEE Transactions on Wireless Communications 10 8 2543 - 2553 2011年08月 
    High speed long range millimetre-wave (mm-wave) links can be achieved by using wideband hybrid antenna arrays of sub-arrays. Due to the array architecture difference, conventional wideband angle-of-arrival (AoA) estimation and beamforming techniques are not applicable to such wideband hybrid arrays. Targeted at point-to-point line-of-sight wireless transmission in the 70/80 GHz E bands, a unified frequency-domain AoA estimation and beamforming algorithm suitable for large scale wideband hybrid arrays of both interleaved and side-by-side sub-arrays is proposed in this paper. The AoA estimation performance is analyzed by deriving a recursive modified Cramr-Rao bound (MCRB). The effect of mutual coupling among antenna elements on the estimation performance is also considered for the hybrid array of side-by-side sub-arrays. The analytical results can be used to determine system parameters according to required system specifications. Simulation results show that the proposed AoA estimation algorithm is robust against practical impairments, and the frequency dependency of the array pattern is significantly reduced after digital beamforming. Simulated mean square errors of AoA estimation are also compared with the analytical bounds, showing that the derived recursive MCRB provides a meaningful indication to the AoA estimation performance. © 2006 IEEE.
  • Val Dyadyuk, Xiaojing Huang, Leigh Stokes, Joseph Pathikulangara
    International Journal of Microwave and Wireless Technologies 3 3 259 - 266 2011年06月 
    This paper reports the test results of a small-scale prototype that implements a digitally beam-formed phased antenna array in the E-band. A four-channel dual-conversion receive RF module for 71â€"76 GHz frequency band has been developed and integrated with a linear end-fire antenna array. Wideband frequency-domain angle-of-arrival estimation and beam-forming algorithms were developed and implemented using Orthogonal Frequency Division Multiplexing (OFDM) with Quadrature Phase-Shift Keying (QPSK) at 1 Gbps. Measured performance is very close to the simulated results and experimental data for an analogue-beam-formed array. This work is a stepping stone toward practical realization of larger hybrid arrays in the E-band. © 2011 Cambridge University Press and the European Microwave Association.
  • Meng Ma, Xiaojing Huang, Bingli Jiao, Y. Jay Guo
    IEEE Transactions on Communications 59 3 844 - 853 2011年03月 
    A solution to the power leakage minimization problem in discrete Fourier transform (DFT) based communication systems is presented. In a conventional DFT based system, modulated subcarriers exhibit high sidelobe levels, which leads to significant out-of-band power leakage. Existing techniques found in the literature either do not achieve sufficient sidelobe suppression or suffer from significant spectral efficiency loss. Precoding can be seen as a general linear processing method for power leakage reduction, however, how to design the optimal linear precoder is still an open problem. In this paper, the power leakage suppression is first treated as a matrix Frobenius norm minimization problem, and then the optimal orthogonal precoding matrix design for the power leakage suppression is proposed based on singular value decomposition (SVD). By further exploiting the extra degrees of freedom in the precoding matrix, two kinds of optimized precoding matrices, one with multi-carrier property and the other with single-carrier property, are developed to take the advantages of orthogonal frequency division multiplexing (OFDM) and single carrier frequency division multiple access (SC-FDMA), respectively. Simulation results show that both the multi-carrier and the single-carrier precoding schemes achieve significant power leakage suppression, and have similar peak-to-average power ratio (PAPR) and bit-error-rate (BER) to those of OFDM and SC-FDMA systems, respectively. © 2011 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck
    IEEE International Conference on Communications 2011年 
    This paper proposes a novel load distribution aware soft frequency reuse (LDA-SFR) scheme for inter-cell interference mitigation and performance optimization in next generation wireless networks. Our proposed scheme aims to provide a solution to effectively achieve inter-cell interference mitigation while maintaining high spectrum efficiency to all users in the cell. The proposed scheme consists of two novel algorithms: edge bandwidth reuse and centre bandwidth compensation. Using the edge bandwidth reuse algorithm, cell-edge users can take advantage of uneven traffic load and user distributions within each cell to expand their resource allocations. The center bandwidth compensation algorithm, on the other hand, provides a protection mechanism for cell-center users to avoid exhaustive edge bandwidth extension. Applying LDA-SFR to an LTE network and comparing its performance against that of existing soft frequency reuse (SFR) and adaptive soft frequency reuse (ASFR) schemes indicates that LDA-SFR is superior as it achieves fairness between cell-edge users and cell-center users in terms of average throughput improvement. © 2011 IEEE.
  • Ying He, Jian Wang, Yongtao Su, Eryk Dutkiewicz, Xiaojing Huang, Jinglin Shi
    IWCMC 2011 - 7th International Wireless Communications and Mobile Computing Conference 2226 - 2230 2011年 
    An efficient hardware-optimized Physical Random Access Channel (PRACH) baseband signal generation algorithm and its ASIC implementation in the LTE user equipment (UE) transmitter are presented in this paper. A simplified DFT of the Zadoff-Chu (ZC) sequence as well as a phase computation are applied to the prime size DFT of the PRACH preamble and the large size IDFT is accomplished by groups of smaller size IFFTs. The optimized algorithm achieves significantly lower computational complexity compared with the original algorithm in the LTE specification and better performance compared to another publication. The ASIC architecture is also designed to reduce the memory size and logic complexity, which achieves a low hardware cost in terms of the cell area. The proposed design was implemented in 65nm CMOS and it was demonstrated that this design can satisfy the timing requirements of the LTE specification. © 2011 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck
    GLOBECOM - IEEE Global Telecommunications Conference 2011年 
    The decode-and-forward relay technique has been introduced in next generation wireless networks (such as LTE) to extend coverage and improve performance, although it may generate additional inter-cell interference. Soft frequency reuse (SFR) has been proposed as the most promising frequency planning strategy to mitigate inter-cell interference in LTE systems. In this paper we propose an effective combination of relay networks and SFR, with a dedicated relay topology and the SFR-based resource allocation scheme. In the proposed relay network, each relay station (RS) can jointly serve cell-edge users from adjacent cells to increase efficiency. The proposed resource allocation scheme, on the other hand, is able to achieve throughput improvement for both cell-edge users and cell-center users by minimizing the interference impact in the system. The benefit of relay networks with SFR-based resource allocation in terms of 30% overall performance improvement over conventional non-relay networks can be realized as demonstrated by the simulation results. © 2011 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    GLOBECOM - IEEE Global Telecommunications Conference 2011年 
    High speed long range millimetre-wave (mm-wave) links can be achieved by using wideband hybrid antenna arrays of sub-arrays. However, conventional wideband angle-of-arrival (AoA) estimation and beamforming algorithms are not applicable to the wideband hybrid arrays due to the array architecture difference. In this paper, an adaptive frequency-domain AoA estimation and beamforming algorithm suitable for practical wideband hybrid array of side-by-side sub-arrays is proposed. Mean square error bounds under simplified array configuration and extreme array imperfection condition are also given. Simulation results show that the proposed algorithm is robust with low complexity and fast convergence. © 2011 IEEE.
  • Jian Zhang, Leif W. Hanlen, Andrew Y. Wang, Xiaojing Huang
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2178 - 2182 2011年 
    Coexistence of multiple wireless body area networks (WBAN) is a very challenging problem because piconets move frequently and each piconet can have hundreds of sensors. The IEEE 802.15.6 task group is developing a standard based on superframe-level frequency-hopping scheme, which is a good solution to the piconet coexistence problem without requiring coordination between piconets. However, its spectrum efficiency is very low when only a single piconet is operating. In this paper we propose a superframe-level time-hopping scheme with variable contention access period. Compared to the frequency-hopping scheme, the proposed scheme has similar interference mitigation capability, but can achieve significant improvement in energy consumption, latency and spectrum efficiency. © 2011 IEEE.
  • K. Clare Xu, Y. Jay Guo, Xiaojing Huang, Eryk Dutkiewicz
    11th International Symposium on Communications and Information Technologies, ISCIT 2011 328 - 332 2011年 
    In this paper, a methodology of employing a set of uniform circular arrays to localize the 3D position of a target in sensor networks is presented and the theoretical framework is given. Simulation results demonstrate the validity of the method and illustrate the effect of the element pattern on the accuracy of direction of arrival (DoA) estimation and positioning. A weighted least squares method (WLSM) is proposed as a means to increase the robustness of the method. © 2011 IEEE.
  • Xiaoliang Xue, Xiaojing Huang
    11th International Symposium on Communications and Information Technologies, ISCIT 2011 205 - 210 2011年 
    Block transform orthogonal frequency division multiplexing (BT-OFDM) - a system sitting in-between two extreme data transmission schemes, i.e., the conventional OFDM system and the single-carrier system, with a balanced system performance is proposed in this paper. Through data symbol grouping and block transformation, the BT-OFDM uses reduced size inverse fast Fourier transform to take the advantages of the single-carrier system to overcome the disadvantages of the conventional OFDM system. Frequency domain representation of the BT-OFDM signal reveals that the block transformation implicitly realizes a precoding or block spreading of the transmitted data symbols. When suitable IFFT size is selected, the BT-OFDM also offers the lowest overall system complexity. © 2011 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    11th International Symposium on Communications and Information Technologies, ISCIT 2011 154 - 158 2011年 
    In many communications and signal processing applications, phase information carried on Gaussian distributed reference signals is often required for various purposes, such as the carrier frequency offset estimation in orthogonal frequency division multiplexing (OFDM) systems. The performance of phase estimation is usually measured by the mean square error (MSE) which is often infeasible to obtain. Instead, the Cramér-Rao Bound (CRB) and modified Cramér-Rao Bound (MCRB) are used to give lower MSE bounds for the phase estimation. This paper presents closed-form MSE approximations for estimating phase information from Gaussian reference signals, which provide better indications of the MSE performance than the MCRB. It is also shown that the MCRB is only attainable at high signal-to-noise ratios and with large number of observed signal samples. Simulated and analytical results are compared to demonstrate the accuracy and efficiency of the derived MSE formulas. © 2011 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck
    11th International Symposium on Communications and Information Technologies, ISCIT 2011 384 - 389 2011年 
    In this paper, we proposed a comprehensive resource allocation scheme to achieve inter-cell interference coordination and performance enhancement for the shared relay network in LTE-Advanced systems. In the scheme, the allocation process is implemented by two steps. The global frequency planning strategies are first employed to realize the interference coordination in the multi-cell environment. Then dedicated local scheduling algorithms are applied to provide further performance enhancement for cell-edge users. As shown in the simulation results, our proposed scheme can achieve the significant performance improvement for cell-edge users while maintaining the high performance for cell-center users, and thus obtain the better performance balance in the system. © 2011 IEEE.
  • Meng Ma, Xiaojing Huang, Y. Jay Guo
    IEEE Communications Letters 14 6 512 - 514 2010年06月 
    A new interference self-cancellation (ISC) method for Single Carrier-FDMA (SC-FDMA) systems is proposed to mitigate the inter-user interference caused by frequency offset or Doppler effect. By transmitting a compensation symbol at the first symbol location in each resource block, the energy leakage can be significantly suppressed. With little bandwidth and power sacrifice, the proposed method can greatly improve the system robustness against frequency offset. Simulation results show that the signal-to-interference ratio (SIR) can be improved by 7 dB on average for the entire system band, and up to 11.7 dB for an individual user. © 2010 IEEE.
  • Xiaojing Huang, Y. Jay Guo, John D. Bunton
    IEEE Transactions on Wireless Communications 9 5 1770 - 1779 2010年05月 
    Owing to the excessive demand on signal processing and space constraint, a full digital implementation of a large adaptive antenna array at millimeter wave frequencies is very challenging. Targeted at long range high data rate point-topoint link in the 70/80 GHz bands, a novel hybrid adaptive antenna array which consists of analogue subarrays followed by a digital beamformer is presented in this paper to overcome the digital implementation difficulty. Two subarray configurations, the interleaved subarray and the side-by-side subarray, are proposed, and two Doppler resilient adaptive angle-of-arrival estimation and beamforming algorithms, the differential beam tracking (DBT) and the differential beam search (DBS), are developed. Simulation results on the DBT and DBS performance are provided using a 64 element hybrid planar array of four 4 by 4 element subarrays with the two subarray configurations, respectively. Recursive mean square error (MSE) bounds of the developed algorithms are also analyzed and compared with simulated MSEs. © 2006 IEEE.
  • Tetsushi Ikegami, Xiaojing Huang, Supavadee Aramvith, Zhifeng Zhao
    ISCIT 2010 - 2010 10th International Symposium on Communications and Information Technologies 4  2010年
  • Xiaojing Huang, Val Dyadyuk, Y. Jay Guo, Leigh Stokes, Joseph Pathikulangara
    GLOBECOM - IEEE Global Telecommunications Conference 2010年 
    This paper presents a joint channel and mutual coupling estimation technique for wideband antenna array to achieve high speed wireless communications in the millimetrewave frequency bands. The estimated channel frequency responses and mutual coupling matrix can be used to digitally calibrate a wideband antenna array in the frequency-domain, followed by digital beamforming. Experiments are carried out using a four-element receive array prototype in the E-band (71-76 GHz) to demonstrate the frequency-domain digital calibration and beamforming performance. The results show that both the mutual coupling and wideband effects are effectively mitigated by the proposed technique and a 11.5 dBi array gain is achieved which is very close to that of an ideal four-element antenna array. ©2010 IEEE.
  • En Zhou, Jinglin Shi, Yonghui Li, Branka Vucetic, Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications and Networking Conference, WCNC 2010年 
    The power allocation problem is addressed for time division duplex (TDD) LTE-A uplink systems in this paper. Due to the IDFT de-spreading in LTE-A uplink, the channel frequency responses in an IDFT de-spreading block will be tangled together. After analyzing the equivalent signal to interference plus noise ratio (SINR) in the time domain, a Truncated Squared norm of channel equalization Coefficients based Power Allocation (TSCPA) method is proposed to improve the final SINR performance after the IDFT de-spreading block. The proposed TSC-PA algorithm is verified for the clustered DFT-s-OFDM system in eigen-model block diagonalization multi-user MIMO uplink environment by simulations. The results demonstrate that the proposed TSC-PA algorithm can further improve the system block error rate (BLER) performance by selecting a proper truncation threshold. ©2010 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications and Networking Conference, WCNC 2010年 
    A novel combination of block spread orthogonal frequency division multiple access (BS-OFDMA) with space-time coded multiple input multiple output (STC MIMO) scheme is proposed for broadband wireless access uplink transmission. Using complex exponential spreading sequences, the block spreading technique can efficiently generate precoded OFDMA signal to exploit frequency diversity. An Alamouti STC MIMO encoding technique is incorporated with the block spreading to achieve further spatial diversity. The performance of the proposed STC-BS-OFDMA system using minimum mean squared error equalization is analyzed, and a closed-form asymptotical bit error rate expression is derived. Simulation results are also given to demonstrate the improved diversity performance as compared with other OFDMA schemes. The proposed techniques are well suited for future broadband wireless access systems such as 3G LTE and 4G. ©2010 IEEE.
  • Yongtao Su, Shan Tang, Jinglin Shi, Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications and Networking Conference, WCNC 2010年 
    We consider the robust linear precoding (LP) and Tomlinson-Harashima precoding (THP) schemes for multiuser MIMO-OFDM downlink channels with limited feedback. Benefiting from the correlation of spatial channels, the mobile terminal compresses and feeds back the time-domain channel vectors instead of the corresponding frequency-domain vectors to substantially reduce the feedback signalling overhead. A compression and restoration method and a codebook design for channel state information at the transmitter (CSIT) feedback are proposed in the time domain. By treating the partial CSIT as a random quantity, we develop the robust precoders to combat the truncation and quantization errors introduced in the feedback procedure. In comparison with the non-robust designs, both the robust LP and THP have better bit-error rate performance especially in high signal-to-noise ratio region. ©2010 IEEE.
  • Yi Huang, Manli Qian, Yao Yuan, Jinglin Shi, Lin Tian, Xiaojing Huang
    IEEE Vehicular Technology Conference 2010年 
    In this paper, a novel call admission control (CAC) scheme for multicast and unicast integrated services is proposed, which optimizes service provision capacity for both services. A resource sharing model is presented in which multiple classes services are dynamically admitted into the system. Several basic CAC rules for the above resource model are proposed first and improved mechanisms are investigated to further increase system performance. Subsequently, the call level QoS and system performance of the resulting CAC scheme are evaluated. Numeric results show that the proposed scheme can achieve optimal multiclass service performance while satisfying QoS constraints. ©2010 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    ISCIT 2010 - 2010 10th International Symposium on Communications and Information Technologies 655 - 660 2010年 
    The Cramér-Rao bound (CRB) has been widely used as a mean square error (MSE) lower bound for unbiased parameter estimations. For phase estimation, however, the CRB is not valid at low signal-to-noise ratio (SNR) due to the effect of phase wrapping. In this paper, closed-form approximations of the MSE lower bounds for the phase estimation are derived under both Gaussian and Rayleigh fading channels, which are particularly useful at low SNR. The derivation is based on an overlapped Gaussian distribution which is used to approximate the true posterior phase distribution. Analytical and simulation results show that the derived closed-form MSE lower bounds provide more meaningful indications to the phase estimation performance than the CRB. ©2010 IEEE.
  • Ke Chen, Xiaojing Huang, Jiangtao Xi
    ISCIT 2010 - 2010 10th International Symposium on Communications and Information Technologies 667 - 671 2010年 
    This paper proposes a novel approach of suppressing narrowband interference from a multi - subband convolutional coded orthogonal frequency division multiplexing (OFDM) system. In this system, the convolutional coded data symbols using different coding generators are transmitted in different subbands. By identifying and discarding the interfered subband(s), the interference level can be greatly reduced and the system performance of the OFDM system can be improved. The interference thresholds for discarding the interfered subband(s) are determined through simulations over additive white Gaussian noise (AWGN) channel for demonstration purpose. The principle can also be applied to multipath fading channel. ©2010 IEEE.
  • Yiwei Yu, Eryk Dutkiewicz, Xiaojing Huang, Markus Mueck, Gengfa Fang
    ISCIT 2010 - 2010 10th International Symposium on Communications and Information Technologies 504 - 509 2010年 
    Due to the requirement of high spectrum efficiency, the frequency reuse of one is targeted for next generation OFDMA-based cellular networks. Such a frequency planning strategy can lead to unacceptable inter-cell interference levels experienced especially by users located at the cell edge area. Soft frequency reuse (SFR) is considered as an effective frequency reuse scheme for inter-cell interference coordination as well as maintaining spectrum efficiency. In this paper, we investigate the performance of SFR for LTE downlink transmission by considering issues of various traffic loads and different power ratio configurations. In addition to the cell-edge user performance, the overall cell performance and the cell-center user performance are both evaluated in terms of throughput estimation. Using simulation studies, the advantages and limitations of SFR are comprehensively examined and compared against the classical frequency reuse of one scheme. ©2010 IEEE.
  • Andrew Zhang, Leif W. Hanlen, Xiaojing Huang
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 84 - 88 2010年 
    The IEEE has proposed a narrowband PHY for the IEEE standard of wireless body area network. To maintain small phase transition of the π/2-DBPSK modulated signal and ensure simple receiver design, repetition code is used where lower data rate is needed. In this paper, we suggest to replace the repetition code by Walsh code to improve the interference cancelation capability of the system. Spreading-before-modulation approach is suggested to retain the merit of small phase transition. Three receivers, including frequency discriminator, differential demodulator and coherent receiver, are developed for the proposed scheme. We show that the proposed scheme, with slightly increased complexity, can improve the signal to interference ratio by about 2 dB, which increases with increasing packet length. ©2010 IEEE.
  • Val Dyadyuk, Xiaojing Huang, Leigh Stokes, Joseph Pathikulangara
    European Microwave Week 2010, EuMW2010: Connecting the World, Conference Proceedings - European Microwave Conference, EuMC 2010 914 - 917 2010年 
    This paper reports the test results of a small-scale prototype that implements a digitally beam-formed phased antenna array in the E-band. A four-channel dual-conversion receive RF module for 71-76 GHz frequency band has been developed and integrated with a linear end-fire antenna array. Wideband frequency-domain angle-of-arrival estimation and beam forming algorithms were developed and implemented using 1 Gbps OFDM QPSK symbols. Measured performance is very close to the simulated results and experimental data for an analogue-beam-formed array. This work is a stepping stone towards practical realization of larger hybrid arrays in the E-band. © 2010 EuMA.
  • Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications and Networking Conference, WCNC 2009年 
    This paper proposes a parallel packet transmission (PPT) scheme based on orthogonal frequency division multiplexing (OFDM). The principle of the PPT scheme is to divide a packet into a number of smaller parallel packets, and transmit each smaller packet over an individual subcarrier of the OFDM symbols instead of spreading the data bits in a packet across a number of different subcarriers. It is proved theoretically that the proposed PPT scheme has higher average throughput than the conventional serial packet transmission without precoding. Furthermore, simulation results show that the OFDM system with PPT outperforms the precoded OFDM system with minimum mean squared error equalization in both uncoded and coded cases in terms of average throughput. The PPT scheme provides an alternative and simpler means to combat frequency-selective fading. © 2009 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    IEEE Wireless Communications and Networking Conference, WCNC 2009年 
    A new frequency and space precoding scheme for multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) systems is presented. For frequency precoding, the data symbols to be transmitted are divided into multiple substreams, and a predefined unitary matrix is applied to each substream to obtain different linear combinations of data symbols in the substream to gain frequency diversity. For space precoding, different precoding matrices selected from a predefined orthogonal matrix are used to allocate each frequency precoded data symbol to all transmit antennas to gain spatial diversity. The number of substreams and the corresponding data symbol mapping scheme are also adaptively determined at the receiver under varying received signal strength and MIMO channel conditions, and are made available to the transmitter through a low-rate feedback channel. Simulation results show that the proposed MIMO OFDM system with adaptive substream selection can effectively exploit both frequency and spatial diversity, and deliver the maximum system throughput. © 2009 IEEE.
  • L. C. Tran, A. Mertins, E. Dutkiewicz, X. Huang
    2009 9th International Symposium on Communications and Information Technology, ISCIT 2009 1161 - 1166 2009年 
    In a multiple-input multiple-output (MIMO) multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system, coherent detection where the channel state information (CSI) is assumed to be exactly known at the receiver requires the transmission of a large number of symbols for channel estimation, thus reducing the bandwidth efficiency. This paper examines the use of unitary differential space-time frequency codes (DSTFCs) in MB-OFDM UWB, which increases the system bandwidth efficiency due to the fact that no CSI is required for differential detection. The proposed DSTFC MB-OFDM system would be useful when the transmission of multiple channel estimation symbols is impractical or uneconomical. Simulation results show that the application of DSTFCs can significantly improve the bit error performance of conventional differential MB-OFDM system (without MIMO). ©2009 IEEE.
  • Xiaojing Huang, Y. Jay Guo, John Bunton
    IEEE Vehicular Technology Conference 2009年 
    A new type of hybrid antenna array consisting of analogue subarrays followed by a digital beamformer is proposed for practical implementation of long range high data rate millimetre wave communications systems. An adaptive algorithm, referred to as the differential beam search (DBS), is proposed for the angle of arrival (AoA) estimation to control the phase shifters in the analogue subarrays and to perform digital beamforming. This algorithm does not need the knowledge of a reference signal and effectively solves the phase ambiguity problem in AoA estimation inherent to the practical subarray configuration. The performance of the proposed DBS algorithms is demonstrated by simulations. © 2009 IEEE.
  • Xiaojing Huang, Y. Jay Guo
    GLOBECOM - IEEE Global Telecommunications Conference 2009年 
    The mean squared error (MSE) is commonly used to measure and compare the performance of various phase estimation techniques in communications and signal processing systems. When the received signal contains recursive nuisance parameters, the MSE is extremely difficult to obtain and even the conventional modified Cramér-Rao bound (MCRB) can not be readily applied. In this paper, a recursive MSE bound and its simplified calculation method are proposed to solve the problem. As an application example, an adaptive hybrid antenna array and its associated angle-of-arrival (AoA) estimation technique are presented. The MSE of the AoA estimation is simulated and compared with the recursive MSE bound and MCRB. The results show that the proposed recursive MSE bound provides a tighter lower MSE bound than the recursive MCRB.
  • L. C. Tran, A. Mertins, X. Huang, E. Dutkiewicz
    3rd International Conference on Signal Processing and Communication Systems, ICSPCS'2009 - Proceedings 2009年 
    Cooperative communication has been intensively considered for general wireless and sensor networks. However, it has been almost untouched in Space-Time-Frequency Coded Multi-band OFDM Ultra-Wideband (STFC MB-OFDM UWB) systems. This paper thus proposes two cross-layer designs for cooperative communication, namely Simple Cooperative Communication Scheme (SCCS) and Advanced Cooperative Communication Scheme (ACCS), in slow fading scenarios. In the former, nodes always cooperate with one another despite the possibly erroneous reception at the partner nodes, while in the latter, nodes cooperate only in the case of successful reception. Simulations show that these schemes may considerably improve the performance of STFC MB-OFDM UWB without any increase of transmission power. © 2009 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang
    2008 3rd International Conference on Information and Communication Technologies: From Theory to Applications, ICTTA 2008年 
    This paper presents an analytical study on the new spreading matrix for Block Spread OFDM known as the Rotation Spreading Matrix and simulates the BER performance in the MMSE equation. In [1] a new spreading matrix was presented for Block Spread OFDM (BSOFDM) known as the Rotation Spreading Matrix. It was shown to greatly improve on the existing spreading matrices such as the Hadamard and the Rotated Hadamard matrices in frequency selective channels such as the ultra wide band and slow fading channels. This paper studies the effect of increasing the block size in BSOFDM using this new matrix.
  • Ibrahim S. Raad, Xiaojing Huang
    2008 3rd International Conference on Information and Communication Technologies: From Theory to Applications, ICTTA 2008年 
    This paper studies higher order Parallel Concatenated Spreading Matrix OFDM (PCSM-OFDM). PCSM-OFDM was showr to greatly improve on the classic Block Spread OFDM, this paper continues the work on PCSM-OFDM and studies higher order in terms of an increased number of streams. This shows that with the increase in the streams the overall BER performance improves.
  • Xiaojing Huang
    IEEE International Conference on Communications 1307 - 1311 2008年 
    This paper settles a controversy over the multipath diversity performance of the precoded orthogonal frequency division multiplexing system with the linear equalization. Through the asymptotical analysis of the bit error rates with extreme system parameters, a comprehensive understanding of the linear equalization's behavior in the frequency-selective multipath fading channels is gained. Compared with the optimum maximum-likelihood detection, the diversity performance of the linear equalization can be well described by an asymptotical signal-to-noise ratio (SNR) degradation, which reveals that the linear equalization can achieve the maximum multipath diversity within an operational SNR range but will lose diversity advantage as SNR increases. ©2008 IEEE.
  • Pingzhou Tu, Xiaojing Huang, Eryk Dutkiewicz
    Proceedings of the 3rd International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CrownCom 2008 2008年 
    In an environment of shared radio spectrum, multiple systems may interfere with each other and cause significant impacts on system coexistence. In this paper we propose an adaptive subband selection technique based on orthogonal frequency division multiplexing (OFDM) to avoid interference for better system coexistence when multiple systems are operating in the same unlicensed industrial, scientific and medical (ISM) bands. Under the assumption that the interference power level and the interfered frequency bands are identified at the receiver, interference thresholds, determined over both Gaussian and multipath fading channels, are applied to adaptively select the transmission subbands so that interference is avoided and the system coexistence issues are relaxed. To verify the effectiveness of the proposed adaptive subband selection method, the system bit error rates (BERs) under different interference levels are simulated and compared.
  • Pingzhou Tu, Xiaojing Huang, Eryk Dutkiewicz
    Proceedings of the 3rd International Conference on Cognitive Radio Oriented Wireless Networks and Communications, CrownCom 2008 2008年 
    Efficient spectrum utilization can be achieved in several ways, one of which is a better spectrum access. In this paper we propose a subband adaptive filtering method for effective spectrum access and dynamic spectrum sharing in cognitive radios (CR). Based on an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) multiple subband transmission signal and subband adaptive filtering technique, some interfered subbands of the transmission signal are filtered and dropped off. The other subbands without interference or with interference less than a predetermined threshold are used for information transmission. The flexibility of the adaptively selecting transmission subbands provides users with the ability to fill in spectrum holes with appropriate number of subbands. Consequently, the spectrum utilization efficiency is improved. We simulate the system bit error rate (BER) performances and demonstrate the improvement on spectrum utilization efficiency by using this subband adaptive filtering method, when different numbers of subbands are used for information transmission.
  • Xiaojing Huang
    3rd International Conference on Communications and Networking in China, ChinaCom 2008 854 - 858 2008年 
    Contrary to the common belief that the carrier frequency offset (CFO) in an orthogonal frequency division multiplexing (OFDM) system would adversely impact on system performance, this paper shows that the CFO actually has the effect of linear precoding among transmitted data symbols and hence can be exploited to improve the diversity performance over frequency-selective fading channels. With both analysis and Monte Carlo simulation, it is proved that an OFDM system with CFO equal to half of the subcarrier spacing can potentially achieve the performance of diversity order four by the maximum-likelihood detection and demonstrate a 5 dB improvement using the minimum mean squared error equalization.
  • Yiwei Yu, Xiaojing Huang, Eryk Dutkiewicz
    3rd International Conference on Communications and Networking in China, ChinaCom 2008 464 - 468 2008年 
    This paper proposes a block spread orthogonal frequency division multiple access (BS-OFDMA) system with a combined space-time coded multiple-input multiple-out (STC-MIMO) scheme called STC-MIMO BS-OFDMA for transmission over frequency selective fading channels. In this system, a novel block spreading approach is firstly applied to effectively achieve precoding in the OFDMA system with lower complexity for improving the multipath diversity performance. The STC-MIMO is then incorporated to take advantage of the spatial diversity. The signal model and architecture of the proposed system are presented, and simulations are carried out to confirm the expected performance improvement.
  • Mohd Riduan Ahmad, Eryk Dutkiewicz, Xiaojing Huang
    PE-WASUN'08: Proceedings of the 5th ACM International Symposium on Performance Evaluation of Wireless Ad-Hoc, Sensor, and Ubiquitous Networks 54 - 62 2008年 
    Cooperative Multiple-Input Multiple-Output (MIMO) schemes can reduce both transmission energy and latency in distributed wireless sensor networks (WSNs). In this paper we develop a new cooperative low power listening (LPL) Medium Access Control (MAC) protocol for two cooperative MIMO schemes: optimal Beamforming (BF) and Spatial Multiplexing (SM). We develop analytical models for the total energy consumption and retransmission rates for both schemes and analyse the proposed MAC protocol in term of total energy consumption. The impact of the check interval and the number of cooperative transmitting nodes, M and cooperative receiving nodes N on the total energy consumption are investigated. We show that the new cooperative MAC with the optimal Beam forming scheme outperforms the other cooperative and SISO schemes in term of total energy consumption with the number of cooperating nodes set to M = 2. © 2008 ACM.
  • Mohd Riduan Ahmad, Eryk Dutkiewicz, Xiaojing Huang
    2008 International Symposium on Communications and Information Technologies, ISCIT 2008 580 - 585 2008年 
    Cooperative MIMO schemes can reduce both transmission energy and latency in distributed wireless sensor networks (WSNs). In this paper we develop a new Cooperative low power listening (LPL) Medium Access Control (MAC) protocol for two cooperative MIMO schemes: Optimal Beamforming (BF) and Spatial Multiplexing (SM). We develop analytical models for the total energy consumption and packet latency for both schemes and analyse the proposed MAC protocol in term of the total energy consumption and packet latency with imperfect synchronisation due to clock jitter. The impact of the clock jitter, the check interval and the number of cooperative nodes on the total energy consumption and latency are investigated. We observe that the Cooperative LPL MAC with Optimal BF is the most promising configuration and it is optimal when then number of co-operating nodes M=2 and jitter difference is below 0.6Tb. © 2008 IEEE.
  • Mohd Riduan Ahmad, Eryk Dutkiewicz, Xiaojing Huang
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2008年 
    Cooperative Multi-In Multi-Out (MIMO) schemes can reduce both transmission energy and latency in distributed wireless sensor networks (WSNs). When circuit energy is considered in such networks, the total energy consumed as the number of cooperating nodes increases becomes of particular interest. In addition, most of the previous works focused only on Space-Time-Block-Code (STBC) schemes and ignore other MIMO schemes. In this paper we present a comparison study of three cooperative MIMO schemes: Beamforming (BF), STBC and Spatial Multiplexing (SM) where both the transmission and circuit energies are considered. We consider a wireless sensor network operating in quasi-static Rayleigh fading channels with M cooperating transmit nodes and N cooperating receive nodes. We show that the Single-In-Single-Out (SISO) scheme is more energy-efficient and has lower packet latency at higher regions of transmission power while the three cooperative MIMO schemes are more energy-efficient and outperform the SISO scheme at the lower regions. From our analysis, we can conclude that, Beamforming outperforms both the SM and STBC schemes in term of energy-efficiency and lower packet latency. Also we suggest that the Beamforming scheme utilising two transmit nodes results in an efficient cooperative system. © 2008 IEEE.
  • Pingzhou Tu, Xiaojing Huang, Eryk Dutkiewicz
    Proceedings of the International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc) 95 - 100 2008年 
    In a shared radio spectrum environment, multiple systems may interfere with each other. In this paper we propose an adaptive filtering method to suppress interference and select the most suitable subbands according to predetermined interference thresholds. Two methods to determine these interference thresholds in Gaussian and multipath fading channels are introduced. The adaptive filtering method enables a system to dynamically use frequency subbands with-out employing frequency hopping techniques. The flexible received signal bandwidth with difierent number of subbands provides great potential for systems to coexist with each other, resulting in higher spectrum utilization effciency. To verify the efiectiveness of the proposed adaptive filtering method, the system bit error rates (BERs) under difierent interference conditions are simulated and compared. © 2008 ACM.
  • Ibrahim S. Raad, Huang Xiaojing, Darryn Löwe
    Third International Conference on Wireless and Mobile Communications 2007, ICWMC '07 67 - 72 2007年 
    This paper presents a study into different angles for the New spread matrix developed for BSOFDM. It varies the angles for the matrix to develop different constellation schemes which are useful in overcoming the frequency selective channels which are encountered in mobile communication systems. Previously it has been discussed that this new matrix (the rotation matrix) has some advantages over Hadamard and the rotated Hadamard matrix in certain channels. This paper presents a study of varies angles with this new matrix over the UWB channels CM1 to CM4.1 © 2007 IEEE.
  • Darryn Lowe, Xiaojing Huang
    Third International Conference on Wireless and Mobile Communications 2007, ICWMC '07 38 - 44 2007年 
    This paper investigates inter-piconet interference (IPI) in the multi-band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) standard. IPI is caused when the time-frequency codes (TFCs) that delineate MB-OFDM piconets collide. An upper-bound on the severity of the IPI problem is obtained through a theoretical analysis of data-rate-specific punctured convolutional codes. Using these results, several methods for adaptive TFCs are proposed and analyzed. Comprehensive simulation results show how packet error rates (PERs) for simultaneous operating piconets (SOPs) can be improved by up to 2 dB by enabling adaptive TFCs at the transmitter. Several combinations of data rate, TFC, channel model and interferer power are studied. © 2007 IEEE.
  • Darryn Lowe, Xiaojing Huang
    The 2nd International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2007 23 - 28 2007年 
    In this paper, we present a new type of packet preamble for orthogonal frequency division multiplexing (OFDM) systems that is based on a complementary sequence pair. It is shown how this approach permits a receiver to dynamically choose between frequency-domain equalization (FDE) and time-domain equalization (TDE). With FDE offering a low-complexity zero-forcing (ZF) equalization and TDE facilitating easy minimum mean square error (MMSE) estimation, it is concluded that a spectrally-flattened complementary sequence pair offers an outstanding combination of flexibility and performance. © 2007 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang, Raad Raad
    The 2nd International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2007 18 - 23 2007年 
    This paper presents a study into different angles for higher order Rotation spreading matrix developed for BSOFDM. It was shown previously that for block size M = 2 that the angle α = π/3 achieved the best result in terms of BER in UWB channels. It was discovered that this was no longer the case when the higher order Rotation spreading matrix was used for larger M sized blocks and that other angles produced better results which proves that the Rotation spreading matrix advantage over existing spreading matrices such as the Hadamard is its flexibility to be adapted to different communication systems. © 2007 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang, Raad Raad
    The 2nd International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2007 17 - 22 2007年 
    Previously a new matrix called the Rotation spreading matrix was proposed for Block Spread OFDM which had advantages over other well known spreading matrices such as the Hadamard in frequency selective channels such the UWB channels. Then a new paper discussed a method to expand this Rotation spreading matrix into higher order allowing the system BSOFDM to achieve higher order matrices which still showed excellent orthogonal properties which can be used in these frequency selective channels. This work is continued on the Rotation spreading matrix and this paper presents another method to expand the Rotation spreading matrix based on Complete Complementary Sets of Sequences which the authors have shown to have excellent properties in higher order matrices. This paper discusses the new method and presents a comparison between the two mentioned methods. © 2007 IEEE.
  • G. M. Yang, R. Jin, J. Geng, X. Huang, G. Xiao
    IET Microwaves, Antennas and Propagation 1 3 733 - 736 2007年 
    A compact planar microstrip ultra-wideband (UWB) bandpass filter (BPF) is presented in this paper. The proposed UWB filter is realised by cascading a high pass filter (HPF) and a low pass filter (LPF). The designed five-pole HPF consists of inter-digital capacitors and short-circuited stubs and has a sharp falling edge at the cutoff frequency. Additional slots are adopted to improve the return loss performance in the pass band. The LPF is realised mainly based on a non-uniform defected ground structure array in the ground. Combining these two structures, a new UWB bandpass filter is fabricated and measured. The measured results show that the proposed BPF has a wide bandwidth from 3.0-10.8GHz, associated the 40dB shape factor as low as 1.2. A group delay variation of less than 0.15ns in the pass band from 3.0-10.8GHz is obtained. It also achieves a wide stopband with 20dB attenuation up to 20.0GHz. © The Institution of Engineering and Technology 2007.
  • Darryn Lowe, Xiaojing Huang
    Third International Conference on Wireless and Mobile Communications 2007, ICWMC '07 2007年 
    This paper analyzes the design and performance of hybrid automatic repeat request (HARQ) extensions to the multi- n band orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) standard. It is shown how both Type-I and Type-III HARQ can significantly reduce the packet error rate (PER) in realistic frequency-selective channels. An exhaustive search is used to find an optimal low-complexity Type-III HARQ scheme by deriving the distance spectra and bit error upper-bound for all sets of complementary puncturing matrices. The consequences of selecting sub-optimal puncturing matrices are also quantified. © 2007 IEEE.
  • Xiaojing Huang
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 802 - 807 2007年 
    Two sets of bit error rate (BER) lower bounds for precoded orthogonal frequency division multiplexing (OFDM) systems using minimum mean square error (MMSE) equalization over frequency-selective multipath fading channels are evaluated by Monte Carlo method in this paper. The first set represents the best performance under different data group sizes used for precoding, whereas the second set represents the best performance under different channel multipath diversity orders. These performance bounds can serve as the guidelines for system designers to decide proper data group sizes for precoded OFDM systems in order to achieve better trade-off between system performance and complexity. Numerical results also confirm the usefulness of these lower bounds for practical OFDM systems. © 2007 IEEE.
  • Jie Zhao, Xiaojing Huangt, Eryk Dutkiewicz
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 1502 - 1506 2007年 
    Dynamic bandwidth multicode interleaved direct sequence (MCIDS), an enhanced MCIDS based Ultra-wideband (UWB) application is proposed in this paper, featuring a cognitive transmission bandwidth adaptation without any adverse effect on the data rate. By introducing a specific lowpass filtering and down-sampling into the traditional MCIDS algorithm, this system can decrease the transmission bandwidth into part of its original bandwidth but still be able to recover all the transmitted data from the reduced bandwidth. This solution can efficiently improve the coexistence ability of UWB devices in a cognitive manner without increasing hardware complexity. © 2007 IEEE.
  • Tu Pingzhou, Huang Xiaojing, Eryk Dutkiewicz
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 184 - 189 2007年 
    In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) system for achieving both frequency diversity and time diversity and investigate the system performance over frequency selective fading channels. The purpose is to exploit the diversity capability of OFDM systems, develop efficienct spectrum spreading technique and improve the system performance against frequency selective channel fading. At the transmitter, the ISS-OFDM signal is generated by employing spread spectrum modulation and interleaving techniques. At the receiver, the received signals are combined by using maximum ratio combining (MRC) technique. The simulation indicates that the ISS-OFDM system has improved performance in multipath fading channels. Another unique characteristic is that the spectrum spreading factor and diversity order provided by the system are reconfigurable to achieve cognitive communications. © 2007 IEEE.
  • Rui Xianyi, Ronghong, Geng Junping, Huang Xiaojing
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 375 - 379 2007年 
    In this paper, we analyze statistical properties of the largest eigenvalue of correlated complex Wishart matrices. The results provide an analytical tool for the study of multipleinput multiple-output (MIMO) maximal ratio combining (MRC) systems in the presence of spatial fading correlation at the transmitter or receiver. Based on them, the exact closed-form expressions for the cumulative distribution function and the probability density function of the output signal-to-noise ratio are presented. The analytical results are validated by Monte Carlo simulations. © 2007 IEEE.
  • Ricardo Gandía Sánchez, Xiaojing Huang, Kwan Wu Chin
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 1241 - 1246 2007年 
    Multihop transmissions over wireless mesh networks present limited end-to-end (E2E) data rates, as every hop waits for an entire packet to arrive before starting retransmission. That is, the E2E data rate drops when every hop stores and then forwards packets, thus making such transmissions unsuitable for multimedia applications. In this work, in order to increase data rates, we present an ultra-wideband (UWB) radio transceiver capable of concurrently transmit and receive (cTxRx) packets. However, concurrently receiving and transmitting comes at the cost of a channel model with increased interference level. Herein, we explain a new interference model and propose a transceiver that compensates for it. We describe the transceiver mathematically and analyze its performance via simulations. Also, we demonstrate that the E2E data rate exceeds that of current multihop transmissions, thus allowing multimedia traffic to be transmitted over a multi-hop wireless mesh network. © 2007 IEEE.
  • Pingzhou Tu, Xiaojing Huang, Eryk Dutkiewicz
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 82 - 86 2007年 
    In this paper we propose an interleaved spread spectrum orthogonal frequency division multiplexing (ISS-OFDM) transmission scheme and demonstrate its reduced peak-to-average power ratio (PAR). The proposed ISS-OFDM signal is realized by two steps. The first step is to modulate the data symbol by complex exponential spreading and the second is to use an interleaving technique to spread the signal spectrum as well as reduce the signal peak-to-average power ratio. The distinctive features of the proposed method are that in the frequency domain the same data information is carried by a number of subbands to effectively spread the signal spectrum and in the time domain the spread signal components are not constructively added together so that signal peaks in the transmitted waveform are avoided. This principle of PAR reduction is unique compared with other techniques such as selected mapping (SLM), partial transmit sequences (PTS), and clipping. With the increase of the number of signal subbands, the PAR performance is improved significantly. © 2007 IEEE.
  • Ibrahim S. Raad, Huang Xiaojing
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 77 - 81 2007年 
    This paper proposes a new approach to Block Spread OFDM called Parallel Concatenated Spreading Matrices OFDM (PCSM-OFDM). While BSOFDM improved the overall BER performance on OFDM in frequency selective channels, this new approach further improves the BER of BSOFDM by a 3dB gain. This is achieved through increasing the diversity of the transmitted samples by concatenating two spreading matrices in parallel to BSOFDM. © 2007 IEEE.
  • L. C. Tran, A. Mertins, E. Dutkiewicz, X. Huang
    ISCIT 2007 - 2007 International Symposium on Communications and Information Technologies Proceedings 380 - 385 2007年 
    The paper examines the potential of the implementation of high-order Space-Time-Frequency Codes (STFCs) in recently proposed STFC Multi-Band OFDM Ultra Wideband (MB-OFDM UWB) communications systems, and compares the performance of two different code structures of order-8 to that of the Alamouti code and of the conventional MB-OFDM UWB system (without STFCs). It is shown that an order-8 STFC provides significantly better error performance, compared to the Alamouti STFC, and much better error performance, compared to the conventional MB-OFDM, without increasing the total transmission power. It Is also shown that, for the same total transmission power, the order-8, fully structured code that we proposed previously for conventional wireless Multiple-Input Multiple-Output (MIMO) Space-Time Block Codes (STBCs) communications is an advanced code, providing the best error performance. © 2007 IEEE.
  • Darryn Lowe, Xiaojing Huang
    The 2nd International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2007 2007年 
    In this paper, we derive and analyze a companding algorithm based on the hyperbolic tangent and inverse hyperbolic tangent functions for use in orthogonal frequency division multiplexing (OFDM) transceivers. Probability density functions (PDFs) that approximate the transmitted and received OFDM signals in the presence of additive white Gaussian noise (AWGN) are derived and used to analyze the degree of companding relative to the signal-to-noise ratio (SNR) and clipping level. A set of optimal companding linearity coefficients for the multiband OFDM (MB-OFDM) ultra-wideband (UWB) standard are presented. © 2007 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang, Darryn Lowe
    Proceeding - 2007 IEEE International Conference on Telecommunications and Malaysia International Conference on Communications, ICT-MICC 2007 377 - 381 2007年 
    This paper continues the work on the new Rotation matrix developed for BSOFDM which showed improvement in frequency selective channels such as the UWB IEEE defined CM1 to CM4 and overall system performance. This paper presents a method by which higher order Rotation matrix can be derived and simulation results are used to show that the higher order Rotation matrix outperforms the Hadamard matrix in frequency selective channels. ©2007 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang, Darryn Lowe
    Proceeding - 2007 IEEE International Conference on Telecommunications and Malaysia International Conference on Communications, ICT-MICC 2007 372 - 376 2007年 
    This paper presents a study into different decoders for the new Rotation Spreading Matrix proposed for Block Spread OFDM (BSOFDM). It presents simulation results for the Maximum Likelihood (ML), Minimum Mean Square Error (MMSE), Zero Forcing (ZF), Maximal Ratio Combining (MRC) and Equal Gain Combining (EGC) decoders across the four IEEE defined Ultra-Wideband (UWB) channels CM1 to CM4. While it is well known that the ML decoder should theoretically outperform all the other decoders, practically due to its complexity it is not a viable option. It can be shown that MMSE, for BSOFDM with the proposed new Rotation Spreading Matrix, has a good performance at low SNR and has been proven to be a practical solution in wireless communications systems due to its simplicity and performance. ©2007 IEEE.
  • Mohd Riduan Ahmad, Eryk Dutkiewicz, Huang Xiaojing
    2007 Asia-Pacific Conference on Applied Electromagnetics Proceedings, APACE2007 2007年 
    This paper presents a study of the impact of transmission delay differences between co-operating nodes on bit error rate performance and energy consumption of wireless sensor networks. We consider a wireless sensor network using an Alamouti virtual MIMO (multiple-input multiple-output) configuration between collaborating nodes operating in quasi-static Rayleigh flat-fading channels. Our results show that above certain delay difference (in the range above 0.75Tb), the traditional non-cooperative approach is more energy-efficient than the cooperative strategy and that the transmission delay difference has the most significant on the transmission energy consumption in the delay range of below 0.75Tb. © 2007 IEEE.
  • Xiaojing Huang, Yunxin Li
    IEEE Transactions on Communications 54 11 1933 - 1936 2006年11月 
    The performance of impulse-train-modulated ultra-wideband (UWB) systems for the ideal additive white Gaussian noise channel is analyzed in this letter. The derived formulae are also used to optimize the modulation parameter of a Gaussian monocycle UWB impulse radio. © 2006 IEEE.
  • Xiaojing Huang, Eryk Dutkiewicz, Ricardo Gandia, Darryn Lowe
    2006 IEEE International Conference on Industrial Informatics, INDIN'06 1012 - 1017 2006年 
    Wireless sensor networks have received a lot of attention in recent years both in the research community and in standards organizations. The emphasis of most sensor network research activities has been on the development of low cost and low power technologies for low bit rate applications. In this paper, we describe our work on ultra-wideband (UWB) sensor network technology targeted for video surveillance applications that require high immunity to noise, interference and jamming, high bit rate, and quality of service support. Such sensor networks are expected to find primary applications in the public safety and military fields. Our emphasis in this paper is on the design of the physical layer that can support such requirements and provide high end-to-end throughput when multi-hopping is used. ©2006 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang, Darryn Lowe
    Proceedings of the 1st IEEE International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2006 346 - 350 2006年 
    This paper presents the study undertaken with block spread OFDM and compares three spreading matrices. The matrices include the Hadamard, Rotated Hadamard and Mutually Orthogonal Complementary Sets of Sequences (MOCSS). The study is carried out for block lengths of M = 2, M = 4 and M = 8 and it shows that all the spreading matrices show improvement and a better performance over the conventional OFDM over frequency selective channel as expected. As the size ofM increased the spreading matrices which have better orthogonal qualities show greater improvement.
  • Xiaojing Huang
    Proceedings of the 1st IEEE International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2006 402 - 407 2006年 
    Arbitrary ratio sampling rate conversion (SRC) structure using B-spline interpolation is proposed for software defined radio (SDR) in this paper. By combining SRC with SDR's transmitter/receiver filter, the constraint on SRC reconstruction filter can be relaxed, and an overall computational reduction can be achieved. The mixed-width B-spline is introduced so that both antiimaging and anti-aliasing requirements for SRC are satisfied. The passband droop introduced by the B-spline interpolation is compensated by a linear phase digital filter incorporated in the SRC structure so that the overall frequency response approaches the desired frequency response of the SDR's transmitter/receiver filter. To make the proposed SRC structure applicable in practice, the mixed-width B-spline is further converted into uni-width B-spline, and the simplified implementation of the uniwidth B-spline interpolation is also derived. A design example of the linear phase digital filter for the proposed SRC structure is given for an IEEE 802.11g wireless local area network (WLAN) SDR receiver, and the overall SRC complexity is analyzed.
  • Ibrahim S. Raad, Xiaojing Huang
    Proceedings of the 1st IEEE International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2006 341 - 345 2006年 
    This paper presents a new method to improve on block spread OFDM by exploiting time diversity to ensure that the blocks are independent and uncorrelated. Simulation results have shown significant improvement over conventional OFDM and Block Spread OFDM.
  • Le Chung Tran, Xiaojing Huang, Eryk Dutkiewicz, Joe Chicharo
    Proceedings of the 1st IEEE International Conference on Wireless Broadband and Ultra Wideband Communications, AusWireless 2006 461 - 466 2006年 
    In this paper, we expand the idea of spreading the transmitted symbols in OFDM systems by unitary spreading matrices based on the rotated Hadamard or rotated Discrete Fourier Transform (DFT) matrices proposed in the literature to apply to Space-Time Coded Multiple-Input Multiple-Output OFDM (STC-MIMO-OFDM) systems. We refer the resulting systems to as STC-MIMO Block Spread OFDM (STC-MIMO-BOFDM) systems. In the proposed systems, a multi-dimensional diversity, including time, frequency, space and modulation diversities, can be used, resulting in better bit error performance in frequency selective Rayleigh fading channels compared to the conventional OFDM systems with or without STCs. Simulations carried out with the Alamouti code confirm the advantage of the proposed STC-MIMO-BOFDM systems.
  • Ibrahim S. Raad, Xiaojing Huang
    Proceedings - 2006 International Conference on Information and Communication Technologies: From Theory to Applications, ICTTA 2006 2 2444 - 2449 2006年 
    This paper presents a new method to improve on block spread OFDM by exploiting time diversity to ensure that the blocks are independent and uncorrelated in a multipath environment. While BSOFDM utilizes frequency diversity to significantly improve on OFDM in frequency selective channel, this did not improve during flat fading channel which does occur during transmission. Our work has also shown that this improvement is also true in multipath transmission. By exploiting time and frequency diversity, BSOFDM is improved significantly over conventional BSOFDM and conventional OFDM.
  • Xiaojing Huang
    2006 International Conference on Communications, Circuits and Systems, ICCCAS, Proceedings 1 588 - 592 2006年 
    This paper demonstrates and compares the complementary properties of two types of Hadamard matrices, i.e., the Walsh-Hadamard matrix and the Golay-paired Hadamard matrix. A simple process is also proposed to construct mutually orthogonal Walsh-Hadamard matrices and mutually orthogonal Golay-paired Hadamard matrices, which represent respectively a collection of mutually orthogonal complementary sets of sequences. Examples are given to verify the relationships between the two types of Hadamard matrices and illustrate the completeness and scalability of the constructed mutually orthogonal complementary sets of sequences. © 2006 IEEE.
  • Xiaojing Huang, Darryn Lowe, Ricardo Gandia, Eryk Dutkiewicz
    2006 International Conference on Communications, Circuits and Systems, ICCCAS, Proceedings 2 1256 - 1260 2006年 
    This second part of the paper presents the system design and performance simulation results of a novel ultrawideband (UWB) system developed for low power, long range, mid to high data rate mesh networking applications. Firstly, the transceiver architecture is described, and the system parameters are selected and justified. Then, the physical layer (PHY) protocol is introduced briefly. Finally, the simulation results regarding the system performance with different data rates in Gaussian and multipath channels are given. It is concluded that the designed transceiver architecture and PHY protocol are adequate and the developed receiver algorithms are feasible for practical implementation. © 2006 IEEE.
  • Xiaojing Huang, Darryn Lowe, Ricardo Gandia, Eryk Dutkiewicz
    2006 International Conference on Communications, Circuits and Systems, ICCCAS, Proceedings 2 1251 - 1255 2006年 
    This paper presents a novel ultra-wideband (UWB) system for low power, long range mid to high data rate mesh networking applications. Combined with the complementary code division multiplexing modulation and the multicode interleaved direct sequence spread spectrum techniques, the system aims to achieve interference resistance, coexistence with legacy systems, and robust performance in hostile multipath environments. The unique feature of the system is the support for concurrent transmission and reception, which will enable a medium access control mechanism with cut-through routing to be developed for high-throughput UWB mesh networks. It is concluded that this new UWB system represents a fundamental advance in UWB technology. © 2006 IEEE.
  • Pingzhou Tu, Xiaojing Huang, Eryk Dutkiewicz
    2006 International Symposium on Communications and Information Technologies, ISCIT 487 - 491 2006年 
    A method for spectrum spreading in an Orthogonal Frequency Division Multiplexing (OFDM) system is proposed in this paper, resulting in a Spread Spectrum OFDM (SS-OFDM) system suitable for ultra-wideband (UWB) applications. By modifying the IFFT module in a conventional OFDM transmitter and interleaving the modulated signal samples within an OFDM symbol, the transmitted signal spectrum is spread greatly to realize spread spectrum communications. This method of spectrum spreading is also compared with that of the Multiband OFDM (MB-OFDM) system. The SS-OFDM signal has the characteristics of a white noise, and its power spectrum density is constant within the desired bandwidth. One of the main advantages of the proposed system is that it can be used for UWB communication without the need for frequency hopping. In addition, the transmitted signal bandwidth can be selected flexibly to meet different system requirements. © 2006 IEEE.
  • Ibrahim S. Raad, Xiaojing Huang, Raad Raad
    2006 IEEE Singapore International Conference on Communication Systems, ICCS 2006 2006年 
    This paper presents a new spreading matrix for Block Spread OFDM (BSOFDM) to improve the performance of the system by increasing the correlation between the symbols. This is achieved by rotating the modulation scheme used at the transmission, say QPSK, into a higher order modulation scheme, for example 16QAM. By this the correlation between the transmitted symbols is increased. The advantage of this new spreading matrix overmore traditional spreading matrices is its flexibility in achieving different higher order modulation schemes during transmission depending on the angle a. This is compared to other spreading matrices in frequency selective channel environment. © 2006 IEEE.
  • Darryn Lowe, Xiaojing Huang
    2006 International Symposium on Communications and Information Technologies, ISCIT 638 - 643 2006年 
    In this paper we present extremely low-complexity adaptive infinite impulse response (IIR) filters that approximate minimum mean square error (MMSE) channel estimation in orthogonal frequency-division multiplexing (OFDM) systems. We show how the packet error rate (PER) can be significantly improved over conventional zero-forcing (ZF) estimation without incurring a significant increase in computational complexity. All quantitative results are provided in the context of multi-band OFDM (MB-OFDM) ultra-wideband (UWB) with standard IEEE channel models. © 2006 IEEE.
  • Xiaojing Huang
    2006 International Symposium on Communications and Information Technologies, ISCIT 503 - 506 2006年 
    The effect of direct current (DC) offset on orthogonal frequency division multiplexing (OFDM) system with zero-padded (ZP) suffix is analysed in this paper. It is found that the ZP appended OFDM system suffers more from DC offset than a cyclic prefix inserted OFDM system and even demonstrates bit error flooring if the DC power exceeds a maximum allowed threshold. Simple algorithms are also proposed for DC offset estimation and compensation. The analysis is confirmed by simulation using multiband OFDM specification for ultra-wideband application. © 2006 IEEE.
  • Darryn Lowe, Xiaojing Huang
    2006 International Symposium on Communications and Information Technologies, ISCIT 73 - 77 2006年 
    This paper presents extremely low-complexity boolean logic for the generation of coefficients suitable for filtering or correlation of scalable complete complementary sets of sequences (SCCSS). As the unique auto- and cross-correlation properties of SCCSS are of broad interest, the simplicity of the proposed coefficient generation technique allows arbitrarily long SCCSS to be used in resource constrained applications. © 2006 IEEE.
  • Darryn Lowe, Xiaojing Huang
    2006 International Symposium on Communications and Information Technologies, ISCIT 623 - 628 2006年 
    In this paper, we design complementary codesets that significantly improve the quality of channel estimation in orthogonal frequency division multiplexing (OFDM) communication systems, with a focus on the recent MB-OFDM ultrawideband (UWB) standard. The proposed time-domain OFDM channel estimation technique incurs only a nominal increase in computational complexity and is able to be readily retrofitted into the existing MB-OFDM standard. The underlying complementary codesets, found via an evolutionary algorithm, combine with the existing preamble synchronization sequences to yield asymptotically ideal auto-correlation functions (ACFs). We show how improvements exceeding 1 dB can be achieved in end-to-end packet error rate relative to conventional zero-forcing OFDM equalization. © 2006 IEEE.
  • Darryn Lowe, Xiaojing Huang
    2006 International Symposium on Communications and Information Technologies, ISCIT 644 - 648 2006年 
    A zero-pad can be used with orthogonal frequency division multiplexing (OFDM) for low-complexity robustness against multipath interference. In this paper, we use adaptive overlap-add (OLA) equalization for improvements of up to 1 dB when used with multi-band OFDM (MB-OFDM) ultra-wideband. A theoretical model that relates the size of OLA window to post-equalizer signal-to-noise ratio is derived. An approximating algorithm is then developed that is suitable for low-complexity implementation, with Monte Carlo simulations used to quantify the performance improvements. We conclude that adaptive OLA equalization is computationally simple and can be implemented while remaining fully compliant with the MB-OFDM standard. © 2006 IEEE.
  • Xiaojing Huang, Yunxin Li
    IEEE Transactions on Communications 53 7 1166 - 1177 2005年07月 
    The optimal linear modulation approximation of any M-ary continuous-phase modulated (CPM) signal under the minimum mean-square error (MMSE) criterion is presented in this paper. With the introduction of the MMSE signal component, an M-ary CPM signal is exactly represented as the superposition of a finite number of MMSE incremental pulses, resulting in the novel switched linear modulation CPM signal models. Then, the MMSE incremental pulse is further decomposed into a finite number of MMSE pulse-amplitude modulated (PAM) pulses, so that an M-ary CPM signal is alternatively expressed as the superposition of a finite number of MMSE PAM components, similar to the Laurent representation. Advantageously, these MMSE PAM components are mutually independent for any modulation index. The optimal CPM signal approximation using lower order MMSE incremental pulses, or alternatively, using a small number of MMSE PAM pulses, is also made possible, since the approximation error is minimized in the MMSE sense. Finally, examples of the MMSE-optimal CPM signal approximation and its comparison with the Laurent approximation approach are given using raised-cosine frequency-pulse CPM schemes. © 2005 IEEE.
  • Xiaojing Huang, Yunxin Li
    IEEE Transactions on Communications 53 7 1100 - 1103 2005年07月 
    Based on a switched linear modulation model recently developed for continuous-phase modulated (CPM) signal representation and approximation, and incorporated with new phase state symbol definitions, three simple CPM receivers are proposed in this letter. Their performance simulation results and complexity comparison are given using a quaternary 2RC (raised cosine frequency pulse) CPM scheme. © 2005 IEEE.
  • Xiaojing Huang
    Proceedings of 2005 International Symposium on Intelligent Signal Processing and Communication Systems, ISPACS 2005 2005 369 - 372 2005年 
    This paper presents simple software and hardware implementations for a class of mutually orthogonal complementary sets of sequences based on its closed-form construction formula. Following a brief review of the Golay-paired Hadamard matrix concept, the flow graph for constructing mutually orthogonal Golay-paired Hadamard matrices, which represent the scalable complete complementary sets of sequences, is proposed. Then, their superb scalability and completeness are summarized. Finally, the C and Matlab functions and a logic schematic diagram are given to easily generate these complementary sequences. © 2005 IEEE.
  • Xiaojing Huang, Yunxin Li, Son Nguyen
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 1 135 - 139 2003年 
    A novel arbitrary conversion ratio sample rate conversion (SRC) structure for software defined radio (SDR) is proposed in this paper. Simplified implementation is also presented. which uses only one multiplication per sample for the trapezoidal interpolation. The passband droop of the trapezoidal interpolation is compensated by the reconstruction filter, which is designed using frequency sampling method. A root raised cosine filter design example is given to show that both anti-imaging and anti-aliasing requirements for SRC can be satisfied by proper selection of design parameters. © 2003 IEEE.
  • Xiaojing Huang, Yunxin Li
    IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 1 707 - 711 2003年 
    Conventional differential detection and energy detection offer poor performances for demodulating continuous phase modulated (CPM) signal because of inherent inter-symbol interference (ISI). Based on the pulse amplitude modulation (PAM) decomposition of CPM signal, the binary CPM with any non-integer modulation index can be interpreted as a linear modulation with differentially encoded pseudo-symbols or equivalently as a modulation scheme with two overlapped waveforms to carry information bits. By combining the equalization of ISI with the design of the receiver filters under the minimum mean square error (MMSE) criterion, the equalized differential detection and equalized energy detection for binary CPM signal demonstrate significant performance improvements while maintaining the same simple receiver structures as the conventional ones. Through theoretical analysis, a closed-form formula is derived to efficiently evaluate the bit error probabilities of the proposed noncoherent receivers. Simulation results using minimum shift keying (MSK) and Gaussian frequency shift keying (GFSK) with BT = 0.5, h = 0.34 are also provided to conform the performance improvements. © 2003 IEEE.
  • Yunxin Li, Xiaojing Huang
    IEEE Transactions on Communications 50 9 1503 - 1514 2002年09月 
    Multiple independent Rayleigh fading waveforms are often required for the simulation of wireless communications channels. Jakes Rayleigh fading model and its derivatives based on sum-of-sinusoids provide simple simulators, but they have major shortcomings in their simulated correlation functions. In this paper, a novel sum-of-sinusoids fading model is proposed and verified, which generates Rayleigh fading processes satisfying the theoretical independence requirements and providing desired power spectral densities with ideal second-order moment. The effects of replacing sinusoids in the proposed model by their approximate waveforms are also analyzed and tested. Performance evaluation and comparison are provided, using the quality measures of the mean-square-error of autocorrelation function and the second-order moment of power spectral density.
  • Xiaojing Huang, Yunxin Li
    IEEE International Conference on Communications 2 758 - 762 2002年 
    This paper analyzes the performances of three impulse train modulated ultra-wideband (UWB) communications systems in additive white Gaussian noise (AWGN) channel. First, the mathematical models for describing biphase, pulse position and hybrid modulated ultra-wideband signals are developed and the decision rules for detecting them with only AWGN interference are proposed. Then, the exact formulae of bit error probabilities of these UWB systems and their closed-form approximations are derived. Finally, the derived formulae are applied to optimize the modulation parameter of a Gaussian monocycle UWB impulse radio.
  • Xiaojing Huang, Yunxin Li
    Conference Record / IEEE Global Telecommunications Conference 2 1056 - 1060 2002年 
    A family of complete complementary sets of sequences with closed-form expression is presented in this paper. Firstly, by introducing the notion of Golay-paired matrix and providing its synthesis algorithms, an orthogonal Golay-paired matrix called Golay-paired Hadamard matrix is derived. Then, general procedures for constructing mutually orthogonal Golay-paired matrices are proposed. Finally, the complete complementary sets of sequences represented by Golay-paired Hadamard matrices are generated and their scalability is illustrated. The unique properties of this new family of scalable complete complementary sets of sequences make it an ideal candidate for applications in future advanced signal processing and communications systems.
  • X. Huang, Y. Li
    IEEE International Conference on Communications 10 2990 - 2994 2001年 
    An intersymbol interference(ISI) free spread spectrum system, named multicode interleaved direct sequence spread spectrum (MCI-DSSS) system, is proposed in this paper. By combining the multicode direct sequence spreading and block interleaving together, this system is able to provide high-speed data transmission over severe mulatipath frequency-selective fading channel. While the ISI is resolved by the orthogonality of the code set used in the multicode spreading, high degree path diversity is exploited to overcome the significant dispersion of the channel which may have a delay spread much longer than one bit duration. Another advantage of this MCI-DSSS system over conventional multicode and multicarrier systems is its higher power efficiency as constant envelope modulations can be applied to the binary MCI-DSSS baseband signal. The principle of the multicode interleaved direct sequence spreading and the MCI-DSSS system models are described. The selection of practical code sets in relation to the system structures is summarized and numerical results are given.
  • X. Huang, Y. Li
    IEEE Vehicular Technology Conference 2 53ND 1184 - 1188 2001年 
    Ultra-wideband technology promises unique advantages over conventional narrowband communications systems. However, the potential interference of ultra-wideband devices to existing narrowband systems is an issue of serious concerns. In this paper, the mathematical models for describing two impulse modulation schemes, namely the biphase modulation and the hybrid modulation, are reviewed. A period extension method and two implementations for PN sequence in the impulse train used to generate ultra-wideband signal are proposed. Considerable reduction in the power spectral density level can be obtained by use of this period extension technique. An example using m-sequence is given, which demonstrates a near-white ultra-wideband spectrum.
  • Yunxin Li, Xiaojing Huang
    IEEE International Conference on Communications 1 41 - 45 2000年 
    The simulation of wireless communication channels often requires the generation of multiple complex waveforms satisfying the following conditions. 1) The real and imaginary parts are independent zero-mean random Gaussian processes with identical auto-correlation functions. 2) The complex waveforms are independent so that the cross-correlation function between any two waveforms is zero. In this paper, we first analyze previously proposed methods based on Jakes fading model to demonstrate that the above two conditions have not been satisfied. We then propose a novel method for the generation of multiple Rayleigh faders, which uses improved arrival angle patterns and incident wave phases. The auto-correlation and cross-correlation functions are derived to prove theoretically that the above two conditions are satisfied. Finally the statistical properties are verified by numerical results.
  • Xiao Jing Huang, Hong Bin Chen
    1988 SEG Annual Meeting 734 - 737 1998年 
    The conventional least-square deconvolution technique is valid only when the conditions of a minimum-phase wavelet and a white reflectivity series are salisfied. When the wavelet is a mixed-phase pulse, however, the least-squares approach requires that the wavelet is known. In this paper a new least-squares deconvolution method suitable for mixed-phase unknown pulse is proposed. It is shown that one only has to loughly estimate the duration of the mixed-phase unknown wavelet before applying this deconvolution method to the seismic trace which is the convolution of the subierrain reflectivity series and mixedphase pulse wavelet. Tests on some synthetic data show that this method works satisfactorily and is insensitive to the preeslimated wavelet duration. It is also proved that the least-squares deconvolution for mixed-phase unknown pulse is equivalent to a gapped smoothing error filtering which can be decomposed into a forward multi-step prediction error filtering plus a backward multi-step prediction error filtering. It is believed that the new deconvolution technique will find practical applications in the geophysical data processing commercial use.
  • Xiao Jing Huang, Hong Bin Chen
    1990 SEG Annual Meeting 1136 - 1139 1990年 
    A new method for wave equation migration is presented in this paper. This migration method, named Born Migration, is formulated by solving the boundary-value problem of the wave equation in an integral closed-form and applying the Born approximation for the Green's function in the inhomogeneous media. The major features of Born migration are: 1. it has no limitation in dip angle; 2. it can accommodate gentle vertical and lateral velocity variations; and 3. it can be implemented by using fast Fourier transformation. It is believed that this technique is especially suitable for migration in 3D seismic survey application.
  • Xiao Jing Huang, Hong Bin Chen
    1989 SEG Annual Meeting 520 - 522 1989年 
    Deconvolution is an essential tool to enhance seismic data resolution. When the seismic data do not conform to the phase and whiteness constraints, the conventional deconvolution techniques fail. There are many mordern deconvolution methods attempting to remove such constraints. One of them is the mixed-phase unknown pulse least-squares deconvolution. In this paper, an improved method is presented which is the combination of the mixed-phase unknown pulse least-squares deconvolution method with a HED-type pulse shaping technique. The principle and algorithm of this method are given. Synthetic data tests show its great improvemtnts in the deconvolution performance.
  • Xiao Jing Huang, Hong Bin Chen, Zhao xiong Wu
    383 - 386 1988年 
    The estimates of the autocorrelation function (ACF) for all lag values of a signal based on truncated measurement are random numbers determined by the particular measured data set of the signal sample. The authors show that model parameters of the signal can be effectively upgraded by a sophisticated modification of the formulas for estimating the entries of the ACF matrix. The upgrading principle is described, and examples are presented.

MISC

  • J. Andrew Zhang, Kai Wu, Xiaojing Huang, Y. Jay Guo, Daqing Zhang, Robert W. Heath IEEE Communications Magazine 60 (11) 106 -112 2022年11月01日 
    Clock asynchronism is a critical issue in integrating radar sensing into communication networks. It can cause ranging ambiguity and prevent coherent processing of discontinuous measurements in integration with asynchronous transceivers. Should it be resolved, sensing can be efficiently realized in communication networks, requiring few network infrastructure and hardware changes. This article provides a systematic overview of existing and potential new techniques for tackling this fundamental problem. We first review existing solutions, including using a finetuned global reference clock, and single-node-based and network-based techniques. We then examine open problems and research opportunities, offering insights into what may be better realized in each of the three solution areas.
  • Sanjeeb Shrestha, Gengfa Fang, Eryk Dutkiewicz, Xiaojing Huang Eurasip Journal on Wireless Communications and Networking 2016 (1) 2016年12月01日 
    We generally emphasize that the zeroforcing (ZF) technique backed by an appropriate medium access control (MAC) protocol can be used to address the inevitable hidden terminal (HT) problem in multi-user multiple input multiple output (MU-MIMO) wireless local area network (WLAN) settings. However, to address the implementation-specific requirements of MU-MIMO WLANs, such as fairness in client access and throughput of the network, we propose a fairness and a throughput-aware ZF precoding in our design at the physical layer (PHY). This precoding scheme not only solves the HT problem but also meets the fairness and the throughput requirements of MU-MIMO WLANs. Besides, we design a MAC layer protocol, supportive to PHY, which decides transmission opportunities (TXOPs) among access points (APs) based on the available degrees of freedom (DoF). We make a mandatory provision in our design that APs should have a sufficient DoF. This can ensure collision-free transmission whenever APs/transmitters transmit in the HT scenario. Additionally, we design an improved channel sounding process for MU-MIMO WLANs with a less signaling overhead than IEEE802.11ac. We demonstrate the feasibility of our PHY in a USRP2/GNU Radio testbed prototype in the lab settings. It is found that our PHY improves the SNR and effective SNR of the received signal from about 5 to 11 dB in the HT scenario. The performance of our MAC design is checked with simulation studies in a typical six-antenna AP and clients scenario. We observe that our MAC protocol has a slightly higher signaling overhead than traditional ready to send/clear to send (RTS/CTS) due to design constraints; however, the signaling time overheads are reduced by 98.67 μs compared to IEEE802.11ac. Another interesting aspect to highlight is the constant Throughput gain of four to five times that of the traditional RTS/CTS. Our MAC protocol obtains this gain as early as 98.67 μs compared to IEEE802.11ac.
  • Xiaojing Huang, Yunxin Li IEEE Transactions on Communications 51 (4) 543 -546 2003年04月 
    This letter presents the solution for decomposing continuous-phase modulated (CPM) signals with integer modulation index into pulse-amplitude modulated components. The notion of main complex pulse is also introduced. A simplified demodulator for CPM signals with integer modulation index is proposed as an application example and simulation results using a quaternary 2 raised cosine (RC) scheme are given.

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