Dig ital transmission over wireless li nks will typ ically enc ounter two major impediments to reliable communications, namely additive noise and intersymbol interference (ISI). Additive noise is a phenomenon of all pr actical transmission systems and is usually miti gated through the use of channe l c oding tech niques, which ad d redundanc y to the information message and thereby provide the receiver with the ability to detect and/or correct erro rs. ISI results from some form of time dispersion over the transmission medium . It arises when successive trans mitted symbols are smeared in time and thus overlap at the receiver input up to the point that they may be no longer dis tinguishable as distinct pulse s. Over radio links, this time dispersion is the natural consequenc e of multi-path prop agation where the transmitted signal is received after it reflects off buildings or other obstacles. From a frequency domain perspective, the channel transfer function then exhibits frequency- dependent attenuations and delays over t he transmission bandwidthhence the alternative name frequency-selective channels (figure 1).