Direct and EM-based MAP Sequence Estimation
with Unknown Time-varying Channels¹

H. Chen, R. Perry, and K. Buckley
ECE Department, Villanova University, Villanova, PA 19085
buckley(hchen,perry)@ece.villanova.edu
(610)-519-5658, FAX: (610)-519-4436

Abstract:

In this paper we address sequence estimation when the InterSymbol Interference (ISI) communication channel is unknown and time varying. We employ a Maximum A Posterior (MAP) approach, in which the unknown channel parameters are assigned a distribution and integrated out. For several channel models of interest we describe both the exact MAP estimator and Viterbi algorithm based implementations. We also present EM algorithms for solving these MAP sequence estimation problems, and we contrast these EM solutions with direct MAP algorithms.