To my (limited) knowledge, when determining which survivor path to choose to produce an error-corrected output of a binary Viterbi decoder, the path with the smallest Hamming distance is the most likely estimation of the transmitted signal.

I have come across an example where I am presented with two survivor paths, both with the same smallest Hamming distance. Is there a method of determining which path to then pick? Or is there no method of doing so?

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    $\begingroup$ They are chosen randomly with an equal probability. $\endgroup$ – AlexTP May 9 '18 at 20:06
  • $\begingroup$ I am doing relatively short examples of this decoding method (10 received bits), with longer bit streams is it less common to have this similarity between survivor paths? $\endgroup$ – C. Faldon May 9 '18 at 20:10

Viterbi decoders are usually designed to take one of the two paths consistently versus the other in the case of a tie. This makes it a lot easier to do bit-exact non-regression testing of the implementation.

If the numeric precision of the input has enough resolution, the probability of a tie should be sufficiently small that it doesn't substantially impact performance to have this (presumably minuscule) bias. If there is not enough precision, then you will have non-trivial bias (and quantization noise), and such insufficient precision will result in performance degradation, regardless of whether the bias is randomized or consistent.

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