Applications of per-survivor processing to mobile digital communications

Applications of Per-Survivor Processing (PSP) to adaptive Maximum Likelihood Sequence Estimation (MLSE) and Reduced State Sequence Estimation (RSSE) are investigated in time-varying frequency-selective Rayleigh fading channels, which are typical of digital mobile communication systems. It is shown that the PSP characteristic of providing the channel estimators to the individual survivors with zero-delay, high-quality data-aiding sequences proves essential in a rapidly time-varying environment. We consider a Time-Division Multiple Access (TDMA) data frame where each user transmits a block of information symbols preceded by a known preamble and followed by a known tail. PSP-based adaptive RSSE decoders are shown to outperform conventional adaptive RSSE decoders of equivalent state complexity based on tentative decisions, when a rapidly varying channel is assumed. In addition, previous results on the need for an adaptive receiver in mobile applications are confirmed and the effect of not using a few known tail symbols is assessed