A low-complexity approach to space-time coding for multipath fading channels

We consider a single-carrier multi-input single-output (MISO) wireless system where the transmitter is equipped with multiple antennas and the receiver has a single antenna. For this setting, we propose a space-time coding scheme based on the concatenation of trellis coded modulation (TCM) with time-reversal orthogonal space-time block coding (TR-STBC). The decoder is based on reduced-state joint equalization and decoding, where a minimum mean-square-error decision-feedback equalizer is combined with a Viterbi decoder operating on the TCM trellis without trellis state expansion. In this way, the decoder complexity is independent of the channel memory and of the constellation size. We show that, in the limit of large block length, the TCM-TR-STBC scheme with reduced-state joint equalization and decoding can achieve the full diversity offered by the MISO multipath channel. Remarkably, simulations show that the proposed scheme achieves full diversity for short (practical) block length and simple TCM codes. The proposed TCM-TR-STBC scheme offers similar/superior performance with respect to the best previously proposed schemes at significantly lower complexity and represents an attractive solution to implement transmit diversity in high speed TDM-based downlink of 3rd generation systems, such as EDGE and UMTS.