Spread-spectrum signaling techniques with antenna arrays and blind adaptation

Abstract

We consider spread-spectrum signals with very long signature sequences by using the random sequence model. We show how this signaling structure can be used effectively by a novel linear receiver that can be utilized by each node in a multiple-access system. The receiver consists of the conventional matched filter followed by a tapped delay line with the provision of incorporating the use of antenna arrays. It has the ability of suppressing multiple-access interference (MAI) and narrowband interference in some weighted proportions, as well as combining multipaths simultaneously. Under some specific simplified channel models, the receiver reduces to the minimum variance distortionless response (MVDR) beamformer, the RAKE receiver, and a notch filter. The interference rejection capability is made possible through a suitable choice of weights in the tapped delay line. We also develop a simple blind adaptive algorithm to obtain the optimal choice of weights efficiently.