Turbo-greedy coding for multiple antenna systems

Previous results have demonstrated excellent performance of turbo coded modulation with iterative demodulation-decoding for systems with antenna diversity. However, the computational complexity at the receiver is exponential in the number of transmit antennas; hence it is too high for the case of large number of transmit and receive antennas. We present a new iterative-greedy demodulation-decoding algorithm for turbo codes for multiple antenna systems. The decoding algorithm is based on a novel greedy detection method for multiuser communications. The iterative-greedy demodulation-decoding algorithm is characterized by the exchange of soft information between the demodulator and the decoder, and the significant decrease in computational complexity, as compared to the standard method of iterative demodulation-decoding, with a slight degradation in performance. This is due to the novel, greedy method of calculating the log-likelihoods to be used in the iterative decoding process, where only a small subset of the possible received vectors is considered, resulting in a receiver with only polynomial complexity in the number of transmit antennas.