Multiary turbo code fitting for unitary space-time modulation and its MAP decoding algorithm

Unitary space-time modulation (USTM) fits for rapid Rayleigh flat fading channels as it can realize wireless communication when neither the transmitter nor the receiver knows the channel state information (CSI). However, an intrinsic problem is that only when the signal-to-noise ratio (SNR) is high can it give an ideal bit error rate (BER) performance. The existing bit-wise processing scheme of the combination of turbo code and USTM improves the BER performance and results in an unacceptable calculation complexity, storage and time delay problem. In this paper, we propose a multiary processing scheme and its corresponding multiary MAP decoding algorithm. Simulation results verify that our scheme can reduce the system complexity while keep a good BER performance. Furthermore, we present the first analysis of the reason for the BER performance deterioration of the combination scheme at low SNR with the help of the definition of USTM.