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Symbol-timing estimation in space-time coding systems based on orthogonal training sequences

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2005年第2期4卷 603-613页

作者： Wu, YC Chan, SC Serpedin, E Univ Hong Kong Dept Elect & Elect Engn Hong Kong Hong Kong Peoples R China

space-time coding has received considerable interest recently as a simple transmit diversity technique for improving the capacity and data rate of a channel without bandwidth expansion. Most research in space-time coding, however, assumes that the symbol timing at the receiver is perfectly known. In practice, this has to be estimated with high accuracy. In this paper, a new symbol-timing estimator for space-time coding systems is proposed. It improves the conventional algorithm of Naguib et al. such that accurate timing estimates can be obtained even if the over-sampling ratio is small. Analytical mean-square error (MSE) expressions are derived for the proposed estimator. Simulation and analytical results show that for a modest oversampling ratio (such as Q equal to four), the MSE of the proposed estimator is significantly smaller than that of the conventional algorithm. The effects of the number of transmit and receive antennas, the oversampling ratio, and the length of training sequence on the MSE are also examined.

关键词： approximated log-likelihood function space-time coding symbol-timing recovery training sequences

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Capon multiuser receiver for CDMA systems with space-time coding

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2002年第5期50卷 1193-1204页

作者： Li, HB Lu, XG Giannakis, GB Stevens Inst Technol Dept Elect & Comp Engn Hoboken NJ 07030 USA Univ Minnesota Dept Elect & Comp Engn Minneapolis MN 55455 USA

We present in this paper a linear blind multiuser receiver, referred to as the Capon receiver, for code-division multiple-access (CDMA) systems utilizing multiple transmit antennas and space-time (ST) block coding. The Capon receiver is designed by exploiting signal structures imposed by both spreading and ST coding. We highlight the unique ST coding induced structure, which is shown to be critical in establishing several analytical results, including self-interference (i.e., spatially mixed signals of the same user) cancellation, receiver output signal-to-interference-and-noise ratio (SINR), and blind channel estimation of the Caopn receiver. To resolve the scalar ambiguity intrinsic to all blind schemes, we propose a semi-blind implementation of the Capon receiver, which capitalizes on periodically inserted pilots and the interference suppression ability of the Capon filters, for (slowly) time-varying channels. Numerical examples are presented to compare the Capon receiver with several other training-assisted and (semi-)blind receivers and to illustrate the performance gain of ST-coded CDMA systems over those without ST coding.

关键词： channel estimation code division multiple access interference suppression multiuser receiver space-time coding transmit diversity

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Trace-orthogonal space-time coding

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2008年第5期56卷 2017-2034页

作者： Fasano, Antonio Barbarossa, Sergio Univ Roma La Sapienza INFOCOM Dept I-00184 Rome Italy Univ Campus Biomed I-00128 Rome Italy

In this paper, we prove that, in MIMO system affected by flat fading, when the channel is unknown at the trans mitter and known at the receiver side, a space-time code does no induce any information loss, regardless of the channel realization if and only if it is a Trace-Orthogonal Design (TOD). Then, in the effort to find a good tradeoff between performance and receiver complexity, we show that, when symbols are carved from a QPSK constellation, the suboptimal detector composed of a linear MMSE estimator followed by hard decision, achieves the minimum bit error rate (BER), if and only if the encoding matrices are, UP to a multiplicative constant, full rank partial isometrics. Such matrices constitute what we term a Unitary Trace-Orthogonal Design (UTOD). Finally, we propose a procedure for the synthesis of TODs which, moreover, can guarantee full diversity when information symbols are carved from constellations composed of algebraic numbers, i.e., for (practically) any conceivable complex constellation.

关键词： algebraic number theory full diversity full rate information lossless linear dispersion codes MIMO systems space-time coding

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Performance of Variable-Power Adaptive Modulation With space-time coding and Imperfect CSI in MIMO Systems

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2009年第4期58卷 2115-2120页

作者： Yu, Xiangbin Leung, Shu-Hung Mow, Wai Ho Wong, Wai-Ki City Univ Hong Kong Kowloon Hong Kong Peoples R China Hong Kong Univ Sci & Technol Kowloon Hong Kong Peoples R China

The performance analysis of multi-input-multi-output (MIMO) systems with M-ary quadrature amplitude modulation (MQAM) and a space-time block code (STBC) over flat Rayleigh fading channels for imperfect channel state information (CSI) is presented. In this paper, the optimum fading gain switching thresholds for attaining maximum spectrum efficiency (SE) subject to a target bit-error rate (BER) and an average power constraint are derived. It is shown that the Lagrange multiplier in the constrained SE optimization does exist and is unique for imperfect CSI and for single-input-single-output (SISO) systems under perfect CSI. On the other hand, the Lagrange multiplier will be unique if the existence condition for MIMO under perfect CSI is satisfied. Numerical evaluation shows that the variable-power (VP) adaptive modulation (AM) with STBC provides better SE than its constant-power (CP) counterpart.

关键词： Adaptive modulation (AM) multi-input-multi-output (MIMO) system space-time coding spectrum efficiency (SE) variable power (VP)

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Cooperative space-time coding with Amplify-and- Forward Relaying

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JOURNAL OF SIGNAL PROCESSING SYSTEMS FOR SIGNAL IMAGE AND VIDEO TECHNOLOGY 2012年第2期67卷 129-138页

作者： Al-nahari, Azzam Y. Dessouky, Moawad I. Abd El-Samie, Fathi E. Menoufia Univ Dept Elect & Elect Commun Fac Elect Engn Menoufia 32952 Egypt

Cooperative diversity using distributed space-time codes has been recently proposed to form virtual antennas in order to achieve diversity gain. In this paper, we consider a multi-relay network operating in amplify-and-forward (AAF) mode. Motivated by protocol III presented in (Nabar et al. 2004), we propose a cooperative diversity protocol implementing space-time coding for an arbitrary number of relay nodes when the source-destination link contributes in the second phase. We consider the use of real-orthogonal and quasi-orthogonal designs of space-time codes as they give better performance than random linear-dispersion codes. The pairwise error probability (PEP) has been derived and the theoretical analysis demonstrates that the proposed protocol achieves a diversity of order N + 1, where N is the number of relay nodes. No instantaneous channel state information is required at the relay nodes. The optimum power allocation that minimizes the PEP is obtained with numerical and theoretical analysis. The aggregate system power constraint is considered in the optimization. Simulation results demonstrate an improvement over the existing orthogonal protocols for different source-destination channel conditions. The results also show that the proposed scheme is robust to the channel estimation errors.

关键词： AAF relaying Cooperative communications space-time coding Spatial diversity

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A new approach to layered space-time coding and signal processing

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IEEE TRANSACTIONS ON INFORMATION THEORY 2001年第6期47卷 2321-2334页

作者： El Gamal, I Hammons, AR Hughes Network Syst Adv Dev Grp Germantown MD 20876 USA

The information-theoretic capacity of multiple antenna systems was shown to be significantly higher than that of single antenna systems In Rayleigh-fading channels. In an attempt to realize this capacity, Foschini proposed the layered space-time architecture. This scheme was argued to asymptotically achieve a lower bound on the capacity. Another line of work has focused on the design of channel codes that exploit the spatial diversity provided by multiple transmit antennas [2], [3]. In this paper, we take a fresh look at the problem of designing multiple-input-multiple-output (MIMO) wireless systems. First, we develop a generalized framework for the design of layered space-time systems. Then, we present a novel layered architecture that combines efficient algebraic code design with iterative signal processing techniques. This novel layered system is referred to as the threaded space-time (TST) architecture. The TST architecture provides more flexibility in the tradeoff between power efficiency, bandwidth efficiency, and receiver complexity. It also allows for exploiting the temporal diversity provided by time-varying fading channels. Simulation results are provided for the various techniques that demonstrate the superiority of the proposed TST architecture over both the diagonal layered space-time architecture in [1] and the recently proposed multilayering approach [4].

关键词： array processing fading channels multiple transmit and receive antennas multiuser detection space-time coding

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On low-complexity space-time coding for quasi-static channels

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IEEE TRANSACTIONS ON INFORMATION THEORY 2003年第6期49卷 1400-1416页

作者： Caire, G Colavolpe, G Inst EURECOM Mobile Commun Grp F-06560 Valbonne France Univ Parma Dipartimento Ingn Informaz I-43100 Parma Italy

We propose a new space-time coding scheme for the quasi-static multiple-antenna. channel with perfect channel state information at the receiver and no channel state information at the transmitter. In our scheme, codewords produced by a trellis encoder are formatted into space-time codeword arrays such that decoding can be implemented efficiently by minimum mean-square error (MMSE) decision-feedback interference mitigation coupled with Viterbi decoding, through the use of per-survivor processing. We discuss the code design for the new scheme, and show that finding codes with optimal diversity is much easier than for conventional trellis space-time, codes (STCs). We provide an upper bound on the word-error rate (WER) of our scheme which is both accurate and easy to evaluate. Then, we find upper and lower bounds on the information outage probability with discrete independent and identically distributed (i.i.d). inputs (as opposed to Gaussian inputs, as in most previous works) and we show that the MMSE front-end yields a large advantage over the whitened matched filter (i.e., zero-forcing) front-end. Finally, we provide a comprehensive performance/complexity comparison of our scheme with coded vertical Bell Labs layered. space-time (V-BLAST) architecture and with the recently proposed threaded space-time codes. We also discuss the concatenation of our scheme with block space-time precoders, such as the linear dispersion codes.

关键词： multiple-antenna systems per-survivor processing space-time coding

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Combining Beamforming and space-time coding Using Noisy Quantized Feedback

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IEEE TRANSACTIONS ON COMMUNICATIONS 2009年第5期57卷 1280-1286页

作者： Ekbatani, Siavash Jafarkhani, Hamid Univ Calif Irvine Dept Elect Engn & Comp Sci Irvine CA 92697 USA

The goal of combining beamforming and space-time coding is to obtain full-diversity order and to provide additional received power (array gain) compared to conventional space-time codes. In this work, a class of code constellations is proposed, called generalized partly orthogonal designs (PODs) and both high-rate and low-rate feedback information is incorporated with possible feedback errors. A binary symmetric channel (BSC) model characterizes feedback errors. Two cases are studied: first, when the BSC bit error probability is known a priori to the transmission ends, and second, when it is not known exactly. Based on a minimum pairwise error probability (PEP) design criterion, we design a channel optimized vector quantizer (COVQ) for feedback information and a precoder matrix codebook to adjust the transmission codewords. The attractive property of our combining scheme is that it converges to conventional space-time coding with low-rate and erroneous feedback and to directional beamforming with high-rate and error-free feedback. This scheme also shows desirable robustness against feedback channel modeling mismatch.

关键词： MIMO systems space-time coding quantization feedback communication beamforming

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Randomized space-time coding for distributed cooperative communication

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2007年第10期55卷 5003-5017页

作者： Sirkeci-Mergen, Birsen Scaglione, Anna Cornell Univ Ithaca NY 14853 USA San Jose State Univ Dept Elect Engn San Jose CA 95192 USA Cornell Univ Sch Elect & Comp Engn Ithaca NY 14853 USA

We study the design of distributed space-time codes for cooperative communication. We assume that each node is equipped with a single antenna;however, to obtain diversity and coding gains, the cooperating nodes act as elements of a multiantenna system. With few exceptions, most of the literature on the subject proposes coding rules in which each node emulates a predetermined antenna of a multiantenna system. Since the nodes need to know their specific antenna index, either internode communication or a central control unit is required. Our design objective is to obtain diversity and coding gains while eliminating the need for code or antenna allocation. We achieve our objective by introducing novel randomized strategies that decentralize the trans mission of a space time code from a set of distributed relays. Our simple idea is to let each node transmit an independent random linear combination of the codewords that would have been transmitted by all the elements of a multiantenna system. In addition to introducing this new class of designs, we fully characterize the diversity order of the corresponding symbol error probability and also analyze how the performance is linked to different choices of the statistics of the random coefficients. We show that the proposed scheme achieves full diversity (N) if N < L, where N is the number of transmitters and L is the number of antennas assumed in the underlying space-time code structure. The diversity order L is achieved if N > L. Interestingly, in certain cases (e.g., N = L = 2), we show that the achieved diversity order is fractional (d* = 1. 5)!.

关键词： cooperative transmission distributed networks diversity space-time coding

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MIMO Radar Range-Angular-Doppler Sidelobe Suppression Using Random space-time coding

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IEEE TRANSACTIONS ON AEROspace AND ELECTRONIC SYSTEMS 2014年第3期50卷 2047-2060页

作者： Zhou, Shenghua Liu, Hongwei Wang, Xu Cao, Yunhe Xidian Univ Natl Lab Radar Signal Proc Xian 710071 Shannxi Peoples R China

To further reduce the sidelobe level of waveforms for colocated multiple-input multiple-output (MIMO) radar, a random space-time coding (STC) method is proposed, which modulates prescribed waveforms at each transmission by a random permutation matrix multiplied by a random diagonal phase matrix. With the random modulation, sidelobes at different pulse repetition periods cannot be coherently accumulated, and then the overall sidelobe level drops significantly after coherent accumulation, as verified by numerical results.

关键词： sidelobe reduction time coding waveforms Random modulation side lobe level permutation matrix Random MIMO radar space-time coding

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