Thinned impulse responses for adaptive FIR filters

Some applications of adaptive FIR filtering, such as multipath correction and interference rejection, can require very long impulse responses, and hence are often computationally expensive. This paper examines the concept of sparse filtering, that is, constraining a substantial number of the coefficients in an FIR filter to zero. This concept is particularly appropriate where a long impulse response duration is required but only a few degrees of freedom (e.g., notches) are needed. This paper examines two aspects, the effects of forcing coefficients to zero and the problem of how to select the taps to be "thinned."