Differential turbo-coded modulation with APP channel estimation

A serially concatenated coding system which can operate without channel state information (CSI) with use of a simple channel-estimation technique is presented. This channel-estimation technique uses the inner decoder's a posteriori probability (APP) information about the transmitted symbols to form a channel estimate for each symbol interval, and is termed "APP channel estimation." The serially concatenated code is comprised of an outer rate-2/3 binary error-control code, separated by a bit interleaver from an inner code consisting of an 8-phase-shift keying (PSK) bit mapping and differential 8-PSK modulation. Coherent decoding provides bit-error rate performance 0.6 dB from 8-PSK capacity for large interleaver sizes. APP channel-estimation decoding without initial CSI over constant and random walk phase models shows near-coherent results, with fractions of a decibel performance loss for random walk and linear phase models.