An Improved Soft-Output Trellis/Tree Iterative Decoder for High-Order BICM on MIMO Frequency Selective Rayleigh Fading Channels

This paper presents an improved soft-output trellis/tree M-algorithm (SOTTMA) (Wong and McClane, 2006) for reduced-complexity equalization of a high-order modulated MIMO system undergoing equal-power, Rayleigh frequency-selective fading. This improved version reduces the amount of computation by approximately half through the utilization of a mapping scheme with multi-level bit-mapping properties (de Jong and Willink, 2002). The complexity of the improved SOTTMA no longer increases with the constellation size and therefore can be applied to equalize systems with high- order modulation (such as 64-QAM).