Improved Design of Trellis Space-time Code for High Spatial-and Multipath Diversity in MIMO-OFDM Fading Channels

摘要

Trellis Coded Modulation (TCM) technique offering good coding gain without sacrificing any bandwidth for transmitting digital sequences over bandlimited channels and Space-Time Block Codes (STBC) from Coordinate Interleaved Orthogonal Designs (CIOD) allowing single-complex symbol decoding and offering higher data rates than traditional orthogonal STBC (OSTBC) have attracted considerable attention. In this study, for the purpose of achieving more high spatial- and multipath diversity in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) fading channels with low decoder complexity, a trellis code CIOD system combining an inner STBC, a coordinate interleaver and an outer trellis code is proposed to enhance the transmission performance. Upper bound expression of a pairwise codeword error probability is derived for the proposed trellis code CIOD system and high spatial- and multipath diversities are achieved from this upper bound analysis. By means of the jointly optimization of the rotation angle of constellation and trellis codes using exhaustive search approaches, the proposed trellis code CIOD achieves higher diversity than the best benchmark system at the cost of reasonable increased complexities of encoding and decoding. Simulation results shows that the proposed optimized {4, 8, 16, 32}-state rate--2/3 8-PSK trellis codes CIOD provides additional 2, 3, 2 and 1.5 dB gains in SNR at the CER of 10^-3, when compared to their best counterparts, respectively.