On fractionally spaced blind adaptive equalization under symbol timing offsets using Godard and related equalizers

The problem of fractionally spaced (FS) blind adaptive equalization under symbol-timing-phase offsets is considered. In the case of trained (nonblind) equalizers, the performance of FS equalizers is known to be independent of the timing-phase unlike that of baud-rate equalizers. Moreover, trained FS equalizers synthesize optimal filters in the minimum mean-square error sense, and hence are superior to baud-rate trained equalizers. It is an open question whether such properties hold true for FS Godard blind equalizers. We present a simulation example where such advantages do not materialize. We also present a solution based upon a parallel multimodel Godard baud-rate filter bank approach which yields a performance almost invariant w.r.t. symbol-timing-phase and superior to that of baud-rate equalizers.