Constrained adaptation for time delay estimation with multipath propagation

The problem of estimating the time difference between two sensor outputs in the presence of a multipath propagation is addressed. Two adaptive configurations are proposed. One configuration assumes that the multipath delay is an integral multiple of the sampling interval. The other configuration allows a nonintegral delay. In either case, filter coefficients are restricted to take on samples of a sinc function only. The role of the adaptive filter is to provide appropriate time shifts to the input signals. Incorporating this constraint on the coefficients, which are adapted by the LMS algorithm, reduces the computations and considerably speeds up the convergence rate. Theoretical derivations and computer simulations are presented to demonstrate the effectiveness of the scheme for time delay measurement and to show its ability to accurately track time-varying parameters