  This paper proposes a new variable step-size (VSS) scheme for the recently
introduced zero-point attracting projection (ZAP) algorithm. The proposed
variable step-size ZAPs are based on the gradient of the estimated filter
coefficients sparseness that is approximated by the difference between the
sparseness measure of current filter coefficients and an averaged sparseness
measure. Simulation results demonstrate that the proposed approach provides
both faster convergence rate and better tracking ability than previous ones.
