Hard decision viterbi decoding through trellis update

[johnchau123]

hi all,
I have some problems in the traceback action of trellis diagram in viterbi decoding

Suppose path metrics be the sum of number of same bits between codeword and received bit

At trellis update stage,
Suppose in path 1, path metrics sum is 14. Set t = t+1, it becomes 17 (3 bits are the same)
Suppose in path 2, path metrics sum is 15. Set t = t+1, it shall be 15. However, at t=t+1, it joins with path 1 in trellis diagram, hence, metrics becomes 17 too.

Then my problem is, in the traceback of Viterbi algorithm, the traceback of 17 (right to back) shall be to 14 or 15?
I am not sure whether the traceback is according to which path contributes to the largest path metrics (i.e. if path 1 chosen) or just based on maximum likelihood (i.e. path 2 chosen).

Thanks!!

 

[lomaxe]

If metrics of the two entering paths be of equal value one path is chosen for elimination by using an arbitrary rule.