MLSE for CPM Signals in a Fading Multipath Channel

We perform sequence estimation for CPM signals transmitted in a time varying multipath channel. The EM (Expectation-Maximization) algorithm, an iterative procedure for producing maximum likelihood estimates, is applied to handle the unknown channel. In order to enable implementation of the EM algorithm in this system, a simplification of this algorithm is derived. Channel estimates derived from training data or estimates of previously transmitted information symbols are used initially. In subsequent iterations tentative estimates of current information symbols are used in addition to improve the channel estimates, which in turn improve sequence estimation. Simulation results of the simplified EM algorithm applied to GSM are presented.