Turbo space-time equalization of TCM for broadband wireless channels

This paper presents a turbo (iterative) equalization method for complex TCM (trellis-coded modulation) signals over broadband wireless channels based on receiver antenna array measurements. The channel is highly dispersive at high data rates causing a severe intersymbol interference (ISI) effect and making the direct application of any trellis based equalization algorithm infeasible. The problem of reducing this excess interference is solved by receiver diversity combining, i.e. using a linear antenna array and a broadband beamformer in the receiver. The beamformer output that contains less ISI is viewed as the output of a serial concatenated coding system and optimum symbol detection is achieved by a turbo equalization and decoding scheme. The proposed receiver structure is simulated for two dimensional TCM signals such as 8-16 PSK and 16-QAM and the results indicate an improved performance of the diversity receiver.