A reduced-complexity soft-input soft-output detection scheme for wideband MIMO channels

This work presents a reduced-complexity soft-input soft-output detection scheme for wideband space-time bit-interleaved coded modulation (ST-BICM) MIMO systems. This scheme, which is referred to as iterative trellis search detection, is based in part on a reduced-complexity variant of the BCJR algorithm. It also uses signal sets with block partitioning labeling, called multilevel mapping constellations, in order to achieve further complexity reduction for higher-order QAM modulation formats. Results from computer simulations of an iterative ("turbo") MlMO receiver employing the new scheme have shown that it successfully eliminates the error floor that occurs if inter-symbol interference is not mitigated. It is also shown that the optimum choice of the number of fingers employed by the detector is not only dependent on the channel characteristics, but also by the fraction of states considered in the trellis search.