Decoding the golden space-time trellis coded modulation

This letter presents new techniques enabling low complexity implementation of a decoder for 2 times 2 MIMO using an inner space-time block code (STBC) concatenated with an outer trellis coded modulation (TCM). The receiver includes a Viterbi decoder and sphere decoders to compute branch metrics. We present a technique to reduce the number of sphere decoding processes at each step of the trellis still retaining maximum- likelihood (ML) frame-error rate (FER) performance as well as a sub-optimal technique to speed up the decoding, with a negligible FER performance loss.