Variable step size affine projection adaptive algorithm for asynchronous W-CDMA-multiuser MMSE receiver in fading multipath channels

In this paper variable step size affine projection algorithm (VSS-APA) filtering. is proposed for multiuser adaptive minimum mean square error (MMSE) receiver for asynchronous wideband code division multiple access systems (W-CDMA) in multipath fading channels. We have modified fixed step size APA (FSS-APA) algorithm to VSS-APA for obtaining faster rate of convergence. Performance of VSS-APA algorithm is compared with normalized least mean square (NLMS), partial rank algorithm (PRA) or block algorithm and recursive least square (RLS) algorithms. It is found that VSS-APA algorithm outperforms NLMS algorithm and PRA in convergence characteristics with significantly less computational complexity as compared to the RLS algorithm. Further, it is shown that VSS-APA offers good near-far resistance.