Augmented APP (A2P2) module for a posteriori probability calculation and channel parameter tracking

The augmented a posteriori probability (APP) module, denoted by A/sup 2/P/sup 2/, comprises two mutually supporting algorithms: (1) a soft-input soft-output (SISO) APP module, adjusted to output edge metric information and (2) a recursive estimator for the channel parameters that benefits from this information at each step of the recursion. The thus-estimated parameters appropriately transform, in turn, the channel output signals that feed the SISO module. When applied to decoding a parallel concatenated convolutional code (PCCC) transmitted by binary phase-shift keying through a channel with frequency offset (0.08/T/sub s/ Hz) and phase jitter (0.23-rad RMS), concentrated at 0.01/T/sub s/ Hz, (T/sub s/-symbol duration), the degradation compared to fully coherent reception is a small fraction of 1 dB, without use of a preamble.