Optimal versus PSP-based sequence detection for Rayleigh fading channels

We investigate maximum likelihood sequence estimation (MLSE) of data sequences transmitted over time-varying frequency-selective Rayleigh fading channels. We present the optimal receiver designed to exploit perfect channel state information (CSI) at the beginning of the data sequence and the optimal receiver which does not use this information. For any given data sequence length a performance range for optimal detection can be identified: this range is lower bounded by the optimal receiver with perfect CSI and upper bounded by that without CSI. For increasing data sequence lengths, this range becomes narrower, since the performance of the two optimal receivers tends to converge to a common level. As a consequence, the performance of the optimal detector can be inferred and compared to that of practical receivers based on per-survivor processing (PSP).