A modified Viterbi algorithm based equaliser for wireless metropolitan area networks

The optimum method of equalisation for channels with multi-path propagation is maximum likelihood sequence estimation (MLSE) using Viterbi algorithm. This algorithm, however, has exponential complexity that makes it unsuitable for use in channels with large delay spreads as is typical in wireless MAN scenarios. Here, we propose an alternative to the basic Viterbi decoding algorithm that takes into account the nature of the channel. The type of channel used in simulations is based on the Stanford University Interim (SUI) model. The modified Viterbi algorithm constitutes estimating the channel response using a Wiener filter and using the tap delays to fix the trellis states to be used, the actual modified Viterbi decoder and a decision feedback element. The entire scheme matches various design criteria and produces reasonably good results.