Differentially-Encoded Turbo-Coded Modulation with APP Phase and Timing Estimation

An easily-implemented serially-concatenated coding system is presented that can operate without channel state information (CSI) via a low-complexity phase estimation technique integrated into the iterative decoding loop. The serially-concatenated code (SCC) is comprised of an outer binary code, separated by a bit interleaver from an inner differential modulation code. When iteratively decoded according to turbo decoding principles, this coding system provides excellent near-capacity performance. The phase estimation technique utilizes the inner decoder’s a posteriori probabilities (APP) on the transmitted symbols to form an iteratively-improving phase estimate in each symbol interval, and is termed APP phase estimation. Use of the differential in-ner code provides rotational invariance to symbol constellation phase slips, as well as interleaver gain due to being a recursive code. Coherent decoding, with perfect CSI, provides bit error rate (BER) performance 0.6 dB from 8-PSK capacity for large interleaver sizes. Incorporation of APP phase estimation in the iterative decoding process provides near-coherent results for a constan