Improving error performance of equalized receivers for broadband radio

The paper deals with the design of suboptimal receivers for data transmission over mobile frequency-selective channels. The complexity of maximum likelihood sequence estimation turns out be exponential in the channel memory. Hence, when dealing with channels with long memory, suboptimal reception must be considered. Among suboptimal receivers, the prefiltered Viterbi detector plays an important role. This receiver consists of a prefilter followed by a Viterbi processor with a number of states lower than that needed for maximum likelihood sequence estimation. Often the parameters of the receiver are optimized according to the minimum mean square error criterion. Our contribution is a stochastic approximation algorithm that optimizes the parameters of the receiver according to a measure of error probability. Simulation results show that our proposed design gives substantial benefits at moderate to high signal-to-noise ratio