On the BCJR-like trellis for space-time group codes

ML-decoding significant savings can be achieved by taking advantage of the common parts of the different codewords. This idea underlying the construction of the so called BCJR-trellis of a block code. By design, whenever the paths corresponding to two different elements, share an edge between splitting points and have identical components at positions for any channel vector. Thus this trellis can be used for efficient ML-decoding.