Low Complexity Receiver Structures for Space-Time Coded Multiple-Access Systems
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Low Complexity Receiver Structures for Space-Time Coded Multiple-Access Systems Sudharman K. Jayaweera Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA Email: [email protected]
H. Vincent Poor Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA Email: [email protected] Received 31 May 2001 and in revised form 11 January 2002 Multiuser detection for space-time coded synchronous multiple-access systems in the presence of independent Rayleigh fading is considered. Under the assumption of quasi-static fading, it is shown that optimal (full diversity-achieving) space-time codes designed for single-user channels, can still provide full diversity in the multiuser channel. The joint optimal maximum likelihood multiuser detector, which can be implemented with a Viterbi-type algorithm, is derived for such space-time coded systems. Low complexity, partitioned detector structures that separate the multiuser detection and space-time decoding into two stages are also developed. Both linear and nonlinear multiuser detection schemes are considered for the first stage of these partitioned spacetime multiuser receivers. Simulation results show that these latter methods achieve performance competitive with the single-user bound for space-time coded systems. Keywords and phrases: multiuser detection, space-time coding, iterative detection.
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INTRODUCTION
Most previous work in space-time coded systems has been concerned with single-user channels [1, 2, 3]. For example, a performance criterion for single-user space-time code construction was given in [3]. In this paper, multiuser detection for space-time coded multiple-access systems is considered. We first investigate the design of space-time codes for multiple-access channels subject to quasi-static, independent Rayleigh fading. We show that the code design criterion derived for the single-user channel in [3] can still be used in this multiuser case. In particular, we show that diversity-achieving codes in single-user channels are capable of providing the full diversity in such multiuser channels. We also consider detection and decoding of space-time coded multiuser systems. As we will see, the joint Maximum Likelihood (ML) decoder for such systems has prohibitively large computational complexity, motivating us to consider low-complexity, sub-optimal detector structures. In particular, we propose partitioned space-time multiuser detectors that separate the multiuser detection and space-time decoding into two stages. We consider both linear and nonlinear schemes for the first stage of the partitioned receiver and examine the performance of these detectors.
Low complexity multiuser receiver structures for spacetime coded systems have previously been described in [4, 5]. For example, a multi-stage receiver suitable for a codedivision multiple-access (CDMA) system employing both turbo and space-time coding was proposed in [5]. However, this paper considers only space-time block coding whereas we are concerned h
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