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The near-field processing and narrowband imaging algorithm for MIMO array

COMPEL-THE INTERNATIONAL JOURNAL FOR COMPUTATION AND MATHEMATICS IN ELECTRICAL AND ELECTRONIC ENGINEERING 2013年第2期32卷 698-710页

作者： Gong, Pengcheng Shao, Zhenhai Zhou, Jingquan Zhu, Xueyong Univ Elect Sci & Technol China Greating UESTC Joint Expt Engn Ctr Chengdu 610054 Peoples R China

Purpose - Imaging is a really difficult problem when systems are implemented in the near-field region and real-time needs. The purpose of this paper is to consider a novel system model and present a nanowband 2-D imaging algorithm in the near-field region and under the real time constraint. Design/methodology/approach - The first part of this paper proposes a novel approximation for the round-trip distance of the near-field echoed data based on a 2-D synthetic aperture planar array. The second part of this work proposes a near-field narrow imaging algorithm based on the above system model. Narrowband waveforms are employed in the array system, so that the range alignment and decoupling in range-azimuth are not necessary. Findings - The errors of the proposed approximation are much smaller as compared with those of the Fresnel approximation. For example, the errors of the proposed approximation are negligible when the antenna is fixed at (0, 0). In other cases, the errors are decreased by almost 50 percent. Compared with 2-D plane array, the synthetic aperture plane of the paper reduces the number of antennas. Finally, numerical simulation results verify the validity of the imaging algorithm. Originality/value - The near-field difficulty is solved by the adoption of the proposed approximation. The theoretical analysis and simulation results verify the validity of the imaging algorithm in the near-field region and under the real time constraint.

关键词： Radar Image processing Radar imaging Near-field multiple-input multiple-output

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Optimum beamforming for MIMO multicasting

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EURASIP JOURNAL ON ADVANCES IN SIGNAL PROCESSING 2013年第1期2013卷 1页

作者： Du, Baisheng Jiang, Yi Xu, Xiaodong Dai, Xuchu Univ Sci & Technol China Dept Elect Engn & Informat Sci Hefei 230027 Anhui Peoples R China Silvus Technol Inc San Diego CA 92127 USA

This paper investigates the transmit (Tx) beamforming design to maximize the throughput of a multiple-input multiple-output multicast channel, where common information is sent from the base station to K users simultaneously. This so-called max-min fair beamforming problem is known to be NP-hard. When the base station is equipped with two Tx antennas, we prove that the original complex-valued beamforming problem can be transformed into a real-valued problem and the globally optimal solution can be found by exhausting at most C-K(1) + C-K(2) + C-K(3) hypothesis tests. Moreover, a prune and search algorithm (PASA) is proposed for searching the optimal beamformer with computational complexity O(K-3) in the worst case. When the base station has more than two Tx antennas, we develop an efficient algorithm named iterative two-dimensional optimization which converts the original beamforming problem into a series of two-antenna subproblems by iterations and hence, the beamformer is improved using PASA iteratively. Simulations results are presented to demonstrate the superior performance of the proposed algorithms.

关键词： Physical layer multicasting multiple-input multiple-output Transmit beamforming Semidefinite relaxation (SDR)

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A Low Complexity Modulation Classification Algorithm for MIMO Systems

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IEEE COMMUNICATIONS LETTERS 2013年第10期17卷 1881-1884页

作者： Muehlhaus, Michael S. Oner, Menguc Dobre, Octavia A. Jondral, Friedrich K. Karlsruhe Inst Technol D-76021 Karlsruhe Germany Mem Univ St Johns St John NF Canada Isik Univ Sile Turkey

A novel algorithm is proposed for automatic modulation classification in multiple-input multiple-output spatial multiplexing systems, which employs fourth-order cumulants of the estimated transmit signal streams as discriminating features and a likelihood ratio test (LRT) for decision making. The asymptotic likelihood function of the estimated feature vector is analytically derived and used with the LRT. Hence, the algorithm can be considered as asymptotically optimal for the employed feature vector when the channel matrix and noise variance are known. Both the case with perfect channel knowledge and the practically more relevant case with blind channel estimation are considered. The results show that the proposed algorithm provides a good classification performance while exhibiting a significantly lower computational complexity when compared with conventional algorithms.

关键词： Automatic modulation classification multiple-input multiple-output fourth-order cumulant

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Near optimal performance joint semi-blind channel estimation and data detection techniques for Alamouti coded single-carrier (SC) MIMO communication systems

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PHYSICAL COMMUNICATION 2013年 8卷 31-37页

作者： Bhalani, J. K. Chauhan, D. Kosta, Y. P. Trivedi, A. I. Charotar Univ Sci & Technol Dept Elect & Commun Engn Changa 388421 Gujarat India Marwari Grp Inst Rajkot Gujarat India MS Univ Fac Technol Dept Elect Engn Baroda Gujarat India

In this paper, two novel joint semi-blind channel estimation and data detection techniques are proposed and investigated for Alamouti coded single-carrier (SC) multiple-input multiple-output (MIMO) communication system using Rayleigh flat fading channel model. In the first novel semi-blind technique, blind channel estimation can be performed by using singular value decomposition (SVD) of received output autocorrelation matrix and training based channel estimation for orthogonal training symbols can be performed by using orthogonal pilot maximum likelihood (OPML) algorithm. Further using, that semi-blind channel estimate and received output, data detection is performed by using Maximum likelihood (ML) detection. Finally we derived new training symbols from error covariance matrix of estimated data and known orthogonal training symbols, which further applied to OPML algorithm for final channel estimate. In the second novel semi-blind technique, blind channel estimation can be performed by using matrix triangularization based on householder QR decomposition (H-QRD) of received output autocorrelation matrix instead of SVD decomposition. Other steps are same as the first novel technique to calculate data detection and final channel estimation. Simulation results are presented under 2-PSK, 4-PSK, 8-PSK and 16-QAM data modulation schemes using 2 transmitters and different combinations of receiver antennas to investigate the performances of novel techniques compare to conventional whitening rotation (WR) and rotation optimization maximum likelihood (ROML) based semi-blind channel estimation techniques. Result demonstrates that novel techniques outperform others by achieving near optimal performance. (C) 2013 Elsevier B.V. All rights reserved.

关键词： multiple-input multiple-output Orthogonal pilot maximum likelihood Rotation optimization maximum likelihood Householder QR decomposition Singular value decomposition Channel estimation

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A Reduced-Complexity Heterodyne Multiband MIMO Receiver with Estimation of Analog Devices Imperfection in a Baseband Feedback Loop

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IEICE TRANSACTIONS ON COMMUNICATIONS 2013年第6期E96B卷 1540-1550页

作者： Ohta, Tomoya Denno, Satoshi Morikura, Masahiro Kyoto Univ Grad Sch Informat Kyoto 6068501 Japan Okayama Univ Grad Sch Nat Sci & Technol Okayama 7008530 Japan

This paper proposes a reduced-complexity multiband multiple-input multiple-output (MIMO) receiver that can be used in cognitive radios. The proposed receiver uses heterodyne reception implemented with a wide-passband band-pass filter in the radio frequency (RF) stage. When an RF Hilbert transformer is utilized in the receiver, image-band interference occurs because of the transformer's imperfections. Thus, the imperfection of the Hilbert transformer is corrected in the intermediate frequency (IF) stage to reduce the hardware complexity. First, the proposed receiver estimates the channel impulse response in the presence of the strong image-band interference signals. Next, the coefficients are calculated for the correction of the imperfection at the IF stage, and are fed back to the IF stage through a feedback loop. However, the imperfection caused by the digital-to-analog (D/A) converter and the baseband amplifier in the feedback loop corrupts the coefficients on the way back to the IF stage. Therefore, the proposed receiver corrects the imperfection of the analog devices in the feedback loop. The performance of the proposed receiver is verified by using computer simulations. The proposed receiver can maintain its performance even in the presence of strong image-band interference signals and imperfection of the analog devices in the feedback loop. In addition, this paper also reveals the condition for rapid convergence.

关键词： cognitive radio heterodyne multiband receiver multiple-input multiple-output analog devices imperfection in a feedback loop raising frequency utilization efficiency

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Interference Alignment in a Poisson Field of MIMO Femtocells

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第6期12卷 2633-2645页

作者： Tri Minh Nguyen Jeong, Youngmin Quek, Tony Q. S. Tay, Wee Peng Shin, Hyundong Kyung Hee Univ Dept Elect & Radio Engn Yongin 446701 Gyeonggi Do South Korea Singapore Univ Technol & Design Singapore Singapore Inst Infocomm Res Singapore Singapore Nanyang Technol Univ Singapore 639798 Singapore

The need for bandwidth and the incitation to reduce power consumption lead to the reduction of cell size in wireless networks. This allows reducing the distance between a user and the base station, thus increasing the capacity. A relatively inexpensive way of deploying small-cell networks is to use femtocells. However, the reduction in cell size causes problems for coordination and network deployment, especially due to the intra-and cross-tier interference. In this paper, we consider a two-tier multiple-input multiple-output (MIMO) network in the downlink, where a single macrocell base station with multiple transmit antennas coexists with multiple closed-access MIMO femtocells. With multiple receive antennas at both the macrocell and femtocell users, we propose an opportunistic interference alignment scheme to design the transmit and receive beamformers in order to mitigate intra- (or inter-) and cross-tier interference. Moreover, to reduce the number of macrocell and femtocell users coexisting in the same spectrum, we apply a random spectrum allocation on top of the opportunistic interference alignment. Using stochastic geometry, we analyze the proposed scheme in terms of the distribution of a received signal-to-interference-plus-noise ratio, spatial average capacity, network throughput, and energy efficiency. In the presence of imperfect channel state information, we further quantify the performance loss in spatial average capacity. Numerical results show the effectiveness of our proposed scheme in improving the performance of random MIMO femtocell networks.

关键词： Beamforming femtocell network interference alignment interference channel multiple-input multiple-output random spectrum allocation stochastic geometry

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On the performance of asynchronous ad-hoc networks using interference alignment with renewal process

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IET COMMUNICATIONS 2013年第15期7卷 1628-1637页

作者： Luo, Yi Du, Huiqin Xue, J. Ratnarajah, Tharm Wilcox, Dave Univ Edinburgh Sch Engn & Elect Inst Digital Commun Edinburgh EH9 3JL Midlothian Scotland Camlin Technol Lisburn BT28 2EX North Ireland

The performance of ad-hoc networks is greatly affected by interference, particularly interference from nearby nodes. Based on stochastic geometry, this work studies a form of multiple-input-multiple-output (interference alignment (IA) that eliminates interference from transmitters within a range and treats the remaining interference as a shot noise process. Adapting to the bursty nature of ad-hoc network traffic, the authors introduce a novel distributed ad-hoc network with renewal process, whereby cooperation between interferer and receiver is implemented in one-way process, which results from the difficulties for the node to change the beamforming or receiving matrix whereas communicating with a proposed transmitter. In addition, this scheme takes advantage of IA, leaving the desired signal with higher degree of freedom (DoF) compared with the partially zero-forcing method. Outage probability and transmission capacity are derived with and without Rayleigh fading. Simulation results show the effect of IA in ad-hoc network, including the incremental in the DoF of the desired signal as time goes by. Monte Carlo simulations are implemented and show that IA outperforms successive interference cancellation by at least 10 dB in terms of the signal-to-interference ratio with large path-loss exponent.

关键词： ad hoc networks interference (signal) Monte Carlo methods radio receivers radio transmitters Rayleigh channels telecommunication traffic asynchronous ad-hoc networks interference alignment renewal process stochastic geometry multiple-input multiple-output shot noise process ad-hoc network traffic distributed ad-hoc network renewal process interferer receiver receiving matrix beamforming transmitter degree of freedom partially zero-forcing method transmission capacity Rayleigh fading Monte Carlo simulations interference cancellation signal-to-interference ratio large path-loss exponent

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Exact Joint Distribution Analysis of Zero-Forcing V-BLAST Gains with Greedy Ordering

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第11期12卷 5377-5385页

作者： Ozyurt, Serdar Torlak, Murat Univ Texas Dallas Dept Elect Engn Richardson TX 75083 USA

We derive the joint probability distribution of zero-forcing (ZF) V-BLAST gains under a greedy selection of decoding order and no error propagation. Unlike the previous approximated analyses, a mathematical framework is built by applying order statistics rules and an exact closed-form joint probability density function expression for squared layer gains is obtained. Our analysis relies on the fact that all orderings are equiprobable under independent and identical Rayleigh fading. Based on this idea, we determine the joint distribution of the ordered gains from the joint distribution of the unordered gains. Our results are applicable for any number of transmit and receive antennas. Although we present our analysis in a ZF V-BLAST setting, our analytical results can be directly applied for the dual cases of ZF V-BLAST. Under the assumption of a low rate feedback of decoding order to the transmitter, a benefit of having exact expressions is illustrated by the calculation of the cutoff value under optimal power allocation that maximizes the sum of the substream outage capacities under a given sum power constraint. We provide numerical results and verify our analysis by means of simulations.

关键词： multiple-input multiple-output zero-forcing V-BLAST outage probability order statistics

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Diversity Analysis on Transmit Antenna Selection for Spatial multiplexing Systems With ML Detection

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2013年第9期62卷 4653-4658页

作者： Jin, Xianglan Cho, Durkbin Dongguk Univ Seoul Dept Informat & Commun Engn Seoul 100715 South Korea Dongguk Univ Seoul Dept Math Seoul 100715 South Korea

In this paper, we analyze the diversity order of the optimal transmit antenna selection (TAS) for spatial multiplexing (SM) systems with maximum-likelihood (ML) detection. By deriving the upper and lower bounds on the diversity order, we prove that the optimal TAS of selecting L antennas among M transmit antennas in the SM system with M transmit antennas and N receive antennas obtains a diversity order of N(M -L + 1), which coincides with the well-known results of the respective diversity orders MN and N for the special cases when L = 1 and L = M. Monte Carlo simulations confirm our theoretical result.

关键词： Diversity order maximum likelihood (ML) multiple-input multiple-output spatial multiplexing (SM) transmit antenna selection (TAS)

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Combined Time, Frequency and Space Diversity in DVB-NGH

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IEEE TRANSACTIONS ON BROADCASTING 2013年第4期59卷 674-684页

作者： Gozalvez, David Gomez-Barquero, David Vargas, David Cardona, Narcis BMW Forsch & Tech GmbH D-80992 Munich Germany Univ Politecn Valencia Valencia 46022 Spain

In this paper, we investigate the combined use of time, frequency, and space diversity in DVB-NGH, the next generation mobile broadcasting standard. Compared to current standards like DVB-H or DVB-SH, the largest improvement in next generation systems is expected to be achieved by means of better diversity in the time, frequency, and space domains. In this sense, DVB-NGH is the first broadcasting system to exploit the use of diversity in the three domains by incorporating at the physical layer long time interleaving (TI), time-frequency slicing (TFS), and multiple-input multiple-output (MIMO). This paper investigates the gains of using time, frequency, and space diversity in DVB-NGH, as well as the mutual influence between the different types of diversity. To this purpose, we employ an information-theoretic approach based on the outage capacity of the channel in addition to physical layer simulations.

关键词： Diversity DVB-H DVB-NGH DVB-SH time interleaving multiple-input multiple-output time-frequency slicing

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