Zhendong Zhou

University of Sydney, Sydney, New South Wales, Australia

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Publications (35)24.84 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this letter, we propose a combined scheme of interference alignment and signal detection to optimize the performance of a multiple-input multiple-output (MIMO) Y channel, which consists of three users and a middle relay equipped with n_U and n_R antennas, respectively. First, an iterative interference alignment algorithm is introduced to optimize both beamforming and combining vectors by minimizing the spillage of the interference signals, and ensuring that the desired signals fall into the orthogonal complement of the interference subspace. Then, a signal detection scheme, which employs feed-forward and feedback filters, is applied at the relay to further deal with system interferences. Simulation results show that the proposed combined scheme for MIMO Y channels produces a significant improvement over the existing schemes.
    IEEE Communications Letters 01/2014; 18(1):66-69. · 1.46 Impact Factor
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    ABSTRACT: A multiple-input multiple-output (MIMO) multi-way relay channel, where a single base station exchanges independent messages with K users via a relay station, is considered. We propose an iterative beamforming optimization algorithm based on orthogonal projection with signal subspace alignment. Moreover, an optimal power allocation is also designed to maximize the system sum rate. Performance evaluation shows that the proposed scheme produces significant improvement and offers higher sum rate than the existing scheme.
    IEEE Communications Letters 06/2012; 16(6):820-823. · 1.46 Impact Factor
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    ABSTRACT: A theoretical analysis of bit error rate (BER) expression of adaptive M-ary quadrature amplitude modulation (M-QAM) for multiple-input multiple-output (MIMO) Y channels, where three users exchange independent messages with each other via a relay within two time slots, is proposed. Performance evaluation shows that the analytical BER closely matches the simulated one, particularly at high signal-to-noise ratios (SNRs).
    IEEE Communications Letters 05/2012; 16(5):577-580. · 1.46 Impact Factor
  • Zhendong Zhou, B. Vucetic
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    ABSTRACT: We consider a K-user multiple-input multiple-output (MIMO) relay channel, where each user sends independent messages to the other K-1 users via a common relay in two time slots. All users and the relay are equipped with multiple antennas. In contrast to existing work, we consider systems with both multiplexing and diversity, where each user message contains multiple data streams and there are extra degrees of freedom to optimize the transmit beamforming matrices. We propose a novel iterative beamforming optimization algorithm based on orthogonal projection optimization with the signal subspace alignment. An optimal power allocation is also considered to maximize the system sum rate. The sum rate performance of the proposed scheme in various channel configurations is verified by simulations, which shows that the proposed scheme produces significant improvement over existing one.
    Vehicular Technology Conference (VTC Spring), 2012 IEEE 75th; 01/2012
  • Zhendong Zhou, B. Vucetic
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    ABSTRACT: We consider a K-user multiple-input multiple-output (MIMO) relay channel, where each user sends K - 1 independent messages to the other K - 1 users via a common relay. All users and the relay are assumed to have multiple antennas. The communication happens in two time slots, the multiple access (MA) stage and the broadcast (BC) stage. A linear transmit beamforming and receive combining scheme is proposed based on signal subspace alignment and physical layer network coding. The optimization of the beamforming and combining vectors is addressed with an iterative suboptimal algorithm based on orthogonal projection optimization in the signal subspaces. Suboptimal power allocation is also considered to maximize the effective signal-to-noise ratios (SNRs). The bit error rate (BER) performance of the proposed scheme in various channel configurations is verified by simulation, which shows that the proposed scheme produces significant improvement over existing one.
    Communications (ICC), 2012 IEEE International Conference on; 01/2012
  • K.K. Teav, Zhendong Zhou, B. Vucetic
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    ABSTRACT: The multiple-input multiple-output (MIMO) Y channel, where three users simultaneously exchange independent messages with each other via a single relay within two time slots, is considered in this paper. We first propose a cooperative network coding protocol, which is called denoise-demodulate-and-forward (DDF), with the design of transmit beamforming and combining schemes to increase network throughput. More importantly, we formulate an optimization problem by using the newly derived bit error rate (BER) expression of adaptive M-ary quadrature amplitude modulation (M-QAM). As the result, the modulation types for both time slots can be chosen to maximize the total throughput of the proposed system under the BER constraint. Performance evaluations show that the proposed scheme can significantly improve the total throughput by comparing to the existing MIMO Y channel and the solution of the optimization problem is validated.
    Vehicular Technology Conference (VTC Spring), 2012 IEEE 75th; 01/2012
  • Source
    Zhendong Zhou, Branka Vucetic
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    ABSTRACT: We consider relay broadcast channels (RBCs) with multiple antennas at all nodes. A practical linear precoding, relaying and combining scheme is proposed. Under an overall power constraint, we derive the optimal power allocation solution in a closed form. A low complexity beamforming vector optimization algorithm is proposed to maximize the effective channel gains and improve the system performance. Simulation results are presented for various channel configurations, which show that the proposed cooperative beamforming algorithm achieves performance very close to that of the exhaustive search algorithm but with a much lower complexity, and the maximum diversity gain is always attained.
    IEEE Transactions on Wireless Communications 04/2011; · 2.76 Impact Factor
  • Zhendong Zhou, Branka Vucetic
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    ABSTRACT: Information theoretical study shows that multiple- input multiple-output (MIMO) systems have a much higher channel capacity than single-input single-output (SISO) systems, which can be characterized as a multiplexing gain. Adaptive modulation and coding (AMC) is proven to be an effective technique to approach the channel capacity by utilizing the channel state information (CSI) at the transmitter. In this paper, following an analysis of the multiplexing gain of a generic AMC MIMO system, we propose an adaptive coded MIMO system that achieves a near-full multiplexing gain as well as a robust BER performance in an outdated CSI environment. A comparison among various adaptive and non-adaptive MIMO systems reveals the proposed system as a good trade-off between the spectral efficiency, BER and system complexity. Index Terms—Adaptive modulation and coding (AMC), bit- interleaved coded modulation (BICM), channel state information (CSI), multiple-input multiple-output (MIMO) system, multiplex- ing gain, rate compatible punctured code (RCPC).
    IEEE Transactions on Wireless Communications 01/2011; 10:294-302. · 2.76 Impact Factor
  • Qiong Zhao, Zhendong Zhou, Branka Vucetic
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    ABSTRACT: In this work, we propose a low complexity semiblind channel estimation algorithm, referred to as the variance squared maximum likelihood (VSML) estimator, which employs only one training symbol in each channel estimation, to estimate general non-reciprocal flat-fading channels in amplify-and-forward (AF) two-way relay networks (TWRNs). We formulate a non-convex objective function and obtain closed-form channel estimates by minimizing its approximate expression. Theoretical analysis proves that the derived channel estimation is asymptotically optimal in large sample size scenarios. Monte-Carlo simulation results show that the VSML estimator outperforms the existing relaxed maximum likelihood (RML) estimator in terms of mean squared error (MSE) performance and remarkably reduces the computational complexity by completely avoiding the grid-search algorithm under M-ary phase-shift-keying (MPSK) modulation.
    IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2011, Toronto, ON, Canada, September 11-14, 2011; 01/2011
  • Zhendong Zhou, Branka Vucetic
    IEEE Transactions on Wireless Communications. 01/2011; 10:940-947.
  • Source
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    ABSTRACT: Interference among multiple base stations that co-exist in the same location limits the capacity of wireless networks. In this paper, we propose a method to design a spectrally efficient cooperative downlink transmission scheme employing precoding and beamforming for multi-user multiple-input-multiple-output (MIMO) systems. The algorithm eliminates the interference and achieves symbol error rate (SER) fairness among different users. To eliminate the interference, Tomlinson Harashima precoding (THP) is used to cancel part of the interference while the transmit-receive antenna weights are chosen to cancel the remaining interference. A new novel iterative method is applied to generate the transmit-receive antenna weights. To achieve SER fairness among different users and further improve the performance of multi-user MIMO systems, we develop algorithms that provide equal signal-to-interference-plus-noise-ratio (SINR) across all users. The users are also ordered so that the minimum SINR for each user is maximized. The simulation results show that the proposed scheme considerably outperforms existing cooperative transmission schemes in terms of the SER performance and complexity and approaches an interference free performance under the same configuration.
    Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010
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    Zhendong Zhou, B. Vucetic
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    ABSTRACT: We consider relay broadcast channels (RBCs) with multiple antennas at all nodes. A practical linear preceding, relaying and combining scheme is proposed. Under an overall power constraint, we derive the optimal power allocation solution in a closed form. A low complexity beamforming vector optimization algorithm is proposed to maximize the effective channel gains and improve the system performance. Simulation results are presented for various channel configurations, which show that the proposed optimized beamforming algorithm achieves performance very close to that of the exhaustive search algorithm but with a much lower complexity, and the maximum diversity gain is always attained.
    Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010
  • Zhendong Zhou, Branka Vucetic
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    ABSTRACT: We consider a multi-user (MU) multiple-input multiple-output (MIMO) channel where each node is equipped with multiple antennas. An orthogonal projection optimization (OPO) algorithm is proposed based on linear transmit beamforming and receive combining. The performance of the OPO algorithm is analyzed which discloses its convergence characteristics. The complexity of the OPO algorithm is also addressed and a computationally efficient algorithm is developed. The OPO algorithm is applied to both uplink and downlink MU MIMO systems, and simulation results show its excellent performance.
    Proceedings of the 71st IEEE Vehicular Technology Conference, VTC Spring 2010, 16-19 May 2010, Taipei, Taiwan; 01/2010
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    ABSTRACT: Interference among multiple base stations that coexist in the same location limits the capacity of wireless networks. In this paper, we propose a method to design a spectrally efficient cooperative downlink transmission scheme employing precoding and beamforming. The algorithm eliminates interference and achieves symbol error rate (SER) fairness among different users. To eliminate the interference, Tomlinson Harashima precoding (THP) is used to cancel part of the interference while the transmit-receive antenna weights are chosen to cancel the remaining interference. A novel iterative method is applied to generate the transmit-receive antenna weights. The convergence behaviour of the iterative process is investigated. To achieve SER fairness among different users and improve the performance of the system, we develop algorithms that provide equal signal to-interference-plus-noise-ratios (SINR) across all users under both per base station (BS) and total BSs power constraints. Per BS and total BSs power constraints are constraints where the power for each BS and all BSs is limited to a particular value. The simulation results show that the proposed scheme outperforms existing cooperative transmission schemes in terms of the SER performance and complexity and closely approaches an interference free performance under the same configuration.
    IEEE Transactions on Wireless Communications 01/2010; · 2.76 Impact Factor
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    ABSTRACT: In this paper, we propose and analyze three new transmit antenna selection schemes with reduced feedback rate requirement compared with the conventional scheme. In Scheme 1, Lt available transmit antennas are divided as equally as possible into two groups with consecutive antennas. The best single antenna within each group is selected. In Scheme 2, only the best one among Lt antennas is made known to the transmitter, and the other one is selected at random. In Scheme 3, Lt antennas are divided into multiple subsets each consisting of two adjacent antennas, and the best subset is selected. Bit error rate (BER) expressions for the proposed schemes with Alamouti code are derived for independent flat Rayleigh fading channels. It is found that all the three schemes achieve a full diversity order. The relative merit of each proposed scheme is delineated based on the trade-off between the asymptotic performance loss and feedback reduction, both relative to the conventional scheme. We conclude that Schemes 1 and 3 are more favorable for practical applications, and the appropriate application scenarios are also identified. The proposed schemes enrich the choices for antenna selection system design for various feedback channel bandwidths and different requirements for quality of service.
    IEEE Transactions on Wireless Communications 02/2009; 8:1006-1016. · 2.76 Impact Factor
  • Leilei Wu, Zhendong Zhou, Branka Vucetic
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    ABSTRACT: Multiple-input multiple-output (MIMO) technologies have the advantage of improving system throughput and error performance by exploiting the spatial diversity, owing to the multiple independent transmit-receive paths. A lot of efforts have been put into MIMO broadcast channels research and it is expected to be a core technology for 3G and 4G wireless systems. Generally, channel state information (CSI) is required at the transmitter, to fully exploit the diversity. In the case that channel reciprocity does not apply, limited feedback is one effective solution to get CSI at the transmitter but it increases system complexity and degrades the performance. In this paper, we propose a low complexity limited feedback scheme for MIMO broadcast channels. Non-cooperative receivers without full CSI and a feedback link with a limited rate are considered. The proposed scheme is based on a novel Grassmannian-based two-layer codebook, each layer having a small dimension, and a vector selection algorithm, to maximize the effective channel gain. A simulation is presented for the proposed scheme, showing that the performance is very close to the best known conventional high dimensional codebook, while the search complexity and memory requirement are reduced by several orders of magnitude.
    Proceedings of the IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2009, 13-16 September 2009, Tokyo, Japan; 01/2009
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    Zhendong Zhou, Branka Vucetic
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    ABSTRACT: We consider two-way relay channels (TWRCs) with multiple antennas at the relay node. Two stage communications are considered, where both sources transmit during the multiple access (MA) stage, and the relay transmits during the broadcast (BC) stage. An optimized network coding scheme is proposed. For the MA stage, a maximum likelihood algorithm is proposed to decode the XOR of the signals received from the two sources. For the BC stage, an optimized beamforming algorithm is proposed to maximize the product of the effective channel gains for the two sources. Both analytical and simulation results show that the proposed scheme achieves a full diversity gain and outperforms the amplify-and-forward (AF) scheme significantly, owing to its efficient use of the relay transmit power and matched excellent performance of the two stages.
    Proceedings of the IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2009, 13-16 September 2009, Tokyo, Japan; 01/2009
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    ABSTRACT: We consider multiuser Gaussian broadcast channels with multiple antennas at both transmitter and receivers. An iterative multiple beamforming algorithm is proposed, which is flexible in the antenna configuration and performs well in low to moderate data rates. Its capacity and bit error rate performance are compared with the ones achieved by the traditional zeroforcing method.
    IEEE Communications Letters 11/2008; · 1.46 Impact Factor
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    ABSTRACT: We consider relay broadcast channels (RBCs) with multiple antennas at all nodes. A practical precoding, relaying and combining scheme is proposed. Under an overall power constraint, we derive the optimal power allocation solution in a closed form. The conditions for an effective RBC scheme are identified with a qualitative analysis to the relationship between the relay gain and the relative strengths of the direct and relay links. Simulation results are shown for various channel configurations, which verify the analysis and conclude that the first hop in the relay chain is a determining factor to the overall performance of the RBC.
    Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008. IEEE 19th International Symposium on; 10/2008
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    ABSTRACT: In this paper, we propose three different transmit antenna selection schemes with reduced feedback requirement compared with the conventional scheme. In Scheme 1, all the Lt available transmit antennas are divided as equally as possible into two groups. The best single antenna within each group is selected. In Scheme 2, only the best one among Lt antennas is made known to the transmitter, and the other one is selected at random. Scheme 3 is for even Lt, and Lt antennas are divided into multiple subsets each consisting of two adjacent antennas, among which the best subset is selected. Analytical performances of these three schemes with the Alamouti space-time block code (STBC) are derived for flat Rayleigh fading channels. The asymptotic signal-to-noise ratio (SNR) loss of each proposed scheme relative to the conventional transmit antenna selection scheme is quantified. Together with the reduction in feedback requirement, the relative merit of each proposed scheme is delineated. In general, all of the three schemes provide a good trade-off between error performance and feedback requirement. And the application scenario for each scheme is also identified. The results in this paper provide guidance for the design of transmit antenna selection systems with various feedback channel bandwidths, different requirements for quality of service, and specific antenna configuration.
    Personal, Indoor and Mobile Radio Communications, 2007. PIMRC 2007. IEEE 18th International Symposium on; 10/2007