Turbo space-time equalization of TCM with receiver diversity - II: Maximum-likelihood detection

This paper presents a turbo equalization method for complex TCM signals over frequency selective, multipath fading channels based on receiver antenna array measurements. The channel observed at each array element is described as an equivalent convolutional encoder acting on the interleaved TCM symbols. The received vector signal can be viewed as produced by a serial concatenated encoder and is decoded by an iterative equalizer that employs M-ary soft output Viterbi algorithm (SOVA) algorithm as decoding rule. Since the computational complexity of the equalizer increases with the number of ISI symbols and antennas used in the receiver, apt alternative receiver is also considered where array outputs are first combined through a beamformer and then sent to the equalizer. Both receiver structures are 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.