Abstract
In this work, we propose interference cancellation techniques and a multi-relay selection algorithm based on greedy methods for the uplink of cooperative direct-sequence code-division multiple access (DS-CDMA) systems. We first devise low-cost list-based successive interference cancellation (GL-SIC) and parallel interference cancellation (GL-PIC) algorithms with RAKE receivers as the front-end that can approach the maximum likelihood detector performance and be used at both the relays and the destination of cooperative systems. Unlike prior art, the proposed GL-SIC and GL-PIC algorithms exploit the Euclidean distance between users of interest and the potential nearest constellation point with a chosen threshold in order to build an effective list of detection candidates. A low complexity multi-relay selection algorithm based on greedy techniques that can approach the performance of an exhaustive search is also proposed. A cross-layer design strategy that brings together the proposed multi-user detection algorithms, and the greedy relay selection is then developed along with an analysis of the proposed techniques. Simulations show an excellent bit error rate performance of the proposed detection and relay selection algorithms as compared to existing techniques.
Highlights
Multi-path fading is a major constraint that seriously limits the performance of wireless communications
In [3, 24], an minimum mean-square error (MMSE)-multi-user detection (MUD) technique has been applied to cooperative systems, where the results indicate that the transmissions are more resistant to multiple access interference (MAI) and obtain a significant performance gain when compared with a single direct transmission
We present a low-complexity multi-relay selection algorithm based on greedy techniques that can approach the performance of an exhaustive search
Summary
Multi-path fading is a major constraint that seriously limits the performance of wireless communications. 1.2 Contributions This work presents cost-effective interference cancellation algorithms and multi-relay selection algorithms for cooperative DS-CDMA systems. We propose a low-cost greedy list-based successive interference cancellation (GL-SIC) multi-user detection method that can be applied at both the relays and the destination of wireless systems. We develop a low-cost greedy list-based parallel interference cancellation (GL-PIC) strategy which employs RAKE receivers as the front-end and can approach the ML detector performance. We present a low-complexity multi-relay selection algorithm based on greedy techniques that can approach the performance of an exhaustive search. A cross-layer design that incorporates the optimization of the proposed GL-SIC and GL-PIC techniques, and the improved greedy multi-relay selection algorithm for the uplink of a cooperative DS-CDMA system is developed and evaluated. The matrix Ak(i) is an (L + 1) × (L + 1) diagonal matrix of amplitudes for user k, bk(i) =[ bk, br1d,k, br2d,k, . . . brLd,k]T is an (L + 1) × 1 vector for user k that contains the transmitted symbol at the source and the detected symbols at the output of each relay, and n(i) is a 2M × 1 noise vector
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