Differentially-encoded turbo coded modulation with APP channel estimation

A simple serially concatenated turbo code using differential 8PSK encoding as the inner code and a [3,2,2] parity code as the outer code is studied. This system is decoded according to turbo principles with iterative exchange of extrinsic probabilities, without differential demodulation. Results 0.6 dB from 8-PSK capacity are demonstrated for large interleaver size. Decoding over channels without prior synchronization is demonstrated to be feasible even with significant phase offset and phase noise, using a simple channel estimator that utilizes the extrinsic output symbol probabilities from the differential APP decoder.