An Improved Max-Log-MAP Decoding Algorithm for UST Symbol-Based Turbo Code

When signal-to-noise ratio (SNR) is low, the performance of unitary space-time modulation (USTM) is unsatisfactory. A novel scheme employing unitary space-time symbol-based turbo code (UST-SB-TC) can greatly reduce the time delay but its MAP decoding algorithm may cause the system instability. As we know, Log-MAP algorithm needs exponential processing and Max-Log-MAP would inevitably result in performance loss. In this paper, we propose an improved MaxLog-MAP decoding algorithm for UST-SB-TC, whose performance is almost the same as Log-MAP algorithm, but the calculation complexity increasing is very limited.