Non-stationary time delay estimation with a multipath

A description is given of a constrained adaptive scheme for time-delay estimation in the presence of multipath propagation. Two configurations are proposed. In either case, the role of the adaptive filters is to provide appropriate time shifts to the input signals. For a filter to function as a pure time shifter, its coefficients must take on the values of the samples of a sinc function. Applying this constraint on the coefficients, which are adapted by the LMS algorithm, reduces the amount of computation and speeds up the convergence rate considerably. since the number of adaptive coefficients is typically of the order of 30 or more, convergence time would be excessive without constraints. The effectiveness of the scheme is demonstrated by simulation results, which show its ability to track time-varying parameters accurately