Performance analysis and soft demapping for coded MIMO-OFDM systems

Abstract

Abstract-Multiple input multiple output-Orthogonal frequency division multiplexing (MIMO-OFDM) is a viable solution for providing high data rate services in harsh channel environments. The optimum receivers for them are those based on the maximum likelihood criterion. However, they have a prohibitive complexity especially when channel dimensions are high and coding is employed. Zero Forcing (ZF) and Linear Minimum Mean Square Error (MMSE) receivers on the other hand provide practicable and low complexity solutions for detection, but require soft demappers to deduce the soft bits information contained in each of the received symbols. In this work, we present the ZF and MMSE receiver analysis of a bit interleaved and coded MIMO-OFDM system and propose a soft output demapper based on MMSE equalizer output to demap the information needed for viterbi decoding. A comparison of the proposed soft demapper with conventional soft demappers in literature show a significant performance improvement. We also noticed that it is more advantageous to apply the proposed demapper on a MIMO-OFDM system employing higher modulation schemes.

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“…This is in order to satisfy the increasing demand for high data rate communications in frequency selective fading channels. The advantages of OFDM include its ability to mitigate Inter-Symbol Interference (ISI) caused by channel frequency selectivity [1], and its use of simple frequency domain equalizers at the receiver for efficient detection [2], [3]. However, OFDM suffers high Peak to Average Power Ratio (PAPR) which may severely impair system performance due to induced spectral regrowth and detection performance degradation.…”

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