The star trellis decoding of Reed-Solomon codes

For the Golay code GGolay with codelength n = 24 the star trellis was proposed in [1]. The time axis consists of a number of parts I = ∪jIj , which are joint in one common point. In Figure 1 an example factor graph representation is depicted. This example has three equal length parts. The time axis of the parts are given by Ij = {0, (j − 1)n/3 + 1, . . . , jn/3,∞}, where ∞ denotes the junction. This junction in Figure 1 is represented by a square and the state space is denoted Si. Each part of the time axis is associated with the conventional trellis shortening with a single starting state and some end states. The star trellis consists of a union of all conventional trellis shortening in the junction ∞. The star trellis of the Golay code is given in Figure 2.