MAP decoding using the EM algorithm

The expectation-maximization (EM) algorithm is popular in estimating parameters of various statistical models. We consider applications of the EM algorithm to the maximum a posteriori (MAP) sequence decoding in channels described by hidden Markov models (HMMs). It is well known that HMMs can accurately approximate large variety of communication channels with memory and in particular, wireless fading channels with noise. The direct maximization of the a posteriori probability is too complex. The EM algorithm allows us to obtain the MAP sequence estimation iteratively