At stage 4 there are two survivor paths with the same

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Unformatted text preview: thm for this problem. Figures 3 (a,b) show Viterbi pruning for stages 3 & 4. Figure 3 (c) shows the survivor paths after stage-4 pruning. Looking back, these paths do not merge all the way back to stage 1. So at stage 4, unless there is no more data (i.e. no more stages), nothing can be yet be said about any of the eventual MLSE. At stage 4 there are two survivor paths with the same minimum cost: the one highlighted with bold bashed branches corresponding to information symbol sequence 1,1,-1,1; and the other highlighted with bold dot-dashed lines corresponding to information symbols 1,-1,1,1. If the final stage is stage 4, then either of these are MLSE solutions. (a) n=0 n=1 r 1=2 2 n=2 r 2 =0 2 n=3 r 3 =−3 2 (5) (3) (0) 34 111111111111111111111111111111 000000000000000000000000000000 −1, −1 0 1 1 0 1 0 1 0 11111111111111111111 00000000000000000000 1 0 1 0 1 0 1 0 (3) 2 25 34 −1, 1 1 0 1 0 1, −1 1 0 1 0 1, 1 (b) 1 0 1 0 11111111111111111111 00000000000000000000 11111111111111111111 00000000000000000000 14 11111111111111111111 00000000000000000000 11111111111111111111 00000000000000000000 (−2) 2 11111111111111111111 00000000000000000000 11111111111111111111 00000000000000000000 11111111111111111111 00000000000000000000 10 11111111111111111111 00000000000000000000 11111111111111111111 00000000000000000000 (1) 2 (−2) 2 30 0 1 0 1 0 1 11111111111111111111 00000000000000000000 1 0 1 0 1 0 11111111111111111111 00000000000000000000 (−4) 2 11111111111111111111...
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