Important differences between BCJR and SOVA algorithms? BCJR algorithm needs noise variance for Gamma (branch metrices) calculation. So I am wondering does SOVA (soft output Viterbi algorithm) needs noise variance?
For an AWGN channel, the exact computation of the log-likelihood ratio requires knowledge of the SNR. However, in Hagenauer's original paper on the SOVA there is an approximation which allows the implementation of the algorithm without estimation of the SNR.