Reduced-state BCJR-type algorithms

In this paper, we propose a technique to reduce the number of trellis states in BCJR-type algorithms, i.e., algorithms with a structure similar to that of the well-known algorithm by Bahl, Cocke, Jelinek and Raviv (BCJR) (1974). This work is inspired by reduced-state sequence detection (RSSD). The key idea is the construction, during one of the recursions, of a “survivor map,” relative to the reduced-state trellis, to be used in the other recursion. We consider iterative detection, based on linear prediction, over a Rayleigh flat-fading channel, referring to the concatenated scheme (outer convolutional code and inner differential code) proposed in Hoeher and Lodge (1999)