Blind multiuser adaptive combining for asynchronous cdma systems

Abstract

This paper presents a novel technique to globally estimate and track the direction of arrival (DOA) of different users in an asynchronous CDMA system. The estimates are obtained exploiting the temporal structure of CDMA signals. No training signal nor a priori spatial information is required. The necessary information is extracted directly from the received signals. The proper combining of the overall information present at the receiver after the despreading, jointly with an Eigenvalue Decomposition (EVD), let as estimate the generalized steering vector for each user. Furthermore, a direct iteration method is introduced in our scheme in order to make the array robust to channel variations and to reduce the computational load of the EVD required for each user.