Genetically enhanced TTCM assisted MMSE multi-user detection for SDMA-OFDM

Space division multiple access (SDMA) aided orthogonal frequency division multiplexing (OFDM) systems assisted by efficient multi-user detection (MUD) techniques have recently attracted intensive research interests. The maximum likelihood detection (MLD) arrangement was found to attain the best performance, although this was achieved at the cost of computational complexity, which increases exponentially both with the number of users and with the number of bits per symbol transmitted by higher-order modulation schemes. By contrast, minimum mean-square error (MMSE) SDMA-MUD exhibits a lower complexity at the cost of performance loss. Forward error correction (FEC) schemes, such as turbo trellis coded modulation (TTCM) may be efficiently amalgamated with SDMA-OFDM systems for the sake of improving the achievable performance. Genetic algorithm (GA) based multi-user detection techniques have been shown to provide a good performance in MUD-aided code division multiple access (CDMA) systems. A GA-aided MMSE MUD is proposed for use in a TTCM-assisted SDMA-OFDM system, which is capable of achieving a similar performance to that attained by its MLD-aided counterpart at a significantly lower complexity, especially at high user loads.