Max-Log-MAP and Log-MAP Decoding Algorithms for UST Symbol Based Turbo Code

An intrinsic pitfall of unitary space-time modulation is that its performance is unsatisfactory at low signal-to-noise ratio. Concatenating it with turbo code is a possible solution, however, bit wise processing results in unacceptable calculation mount. A novel scheme employing unitary space-time symbol base turbo code can greatly reduce the time delay but its MAP decoding algorithm may lead to system instability. We propose two feasible simplified versions for MAP algorithm, using the idea of Max- Log-MAP and Log-MAP. These algorithms can significantly reduce the calculations while keep almost the same error rate performance compared with MAP algorithm.