Branch canceling technique for turbo TCM decoding

A new complexity reducing technique for turbo trellis-coded modulation (TTCM) is presented. The novel technique is investigated in conjunction with Max-Log-MAP decoding algorithm and is evaluated in terms of complexity and bit error rate (BER) performance in an additive white Gaussian noise (AWGN) channel and uncorrelated, i.e. fully interleaved Rayleigh fading channel. This novel method is based on the assumption that not all of the branches in the trellis have to be taken into consideration in calculating the state metric in turbo TCM decoding. Computer simulated BER performance evaluation results and complexity comparison are reported, showing Max-Log-MAP algorithm equivalent performance as well as noticeably lower computational complexity in comparison to Max-Log-MAP.