Blind adaptive code acquisition for multiuser DS-CDMA systems

Abstract

Code acquisition in direct-sequence code division multiple access (DS-CDMA) must occur before any multiuser detection is used. In this paper, a blind code acquisition algorithm is proposed using adaptive filtering based on the constant modulus algorithm (CMA). In the same manner as the subspace-based channel estimation, the task of delay estimation problem is to minimize the Euclidean norm of the projection of the linear filter onto the subspace spanned by interfering users in the noiseless case. We exploited the lock convergence property of CMA to give a higher acquisition-based capacity and near-far resistance compared to the conventional sliding correlator. We analyzed the mean acquisition time, detection and false alarm probabilities in terms of probability density function of the decision statistics.