On sequential delay estimation in wideband digital communication systems

The problem of estimating the symbol timing in wideband data communication signals is considered. Conventional approaches to this problem suffer from several drawbacks, including possible lack of consistency due to multiple extrema in the error surface, and very slow convergence due to exceedingly sharp waveform correlation functions. In this work, sequential estimation algorithms that alleviate these problems are constructed and analyzed. These algorithms are based on two techniques: the use of regularization (i.e., prefiltering) to produce a consistent initial estimate at the expense of higher mean-square error; and the coupling of recursive maximum-likelihood with this consistent estimator to produce the desired goal - a recursive consistent and efficient estimator.