Performance of an LMS type receiver for interference suppression in long code DS-CDMA on Rayleigh fading channels

Abstract

We consider interference suppression for direct sequence code division multiple access systems when long codes are used for spreading. In particular, we evaluate the performance of a least mean square (LMS) type adaptive receiver on AWGN and correlated Rayleigh fading channels. The receiver uses a chip matched filter followed by an adaptive equalizer structure which performs despreading and interference suppression. The receiver requires only the knowledge of the long code and timing of the desired user. The probability of the error performance of the long code LMS (LC-LMS) receiver is estimated for varying degrees of near-far ratio (NFR), mobile user speed (equivalently, the Doppler bandwidth), and long code period (expressed in number of information bits). Performance results indicate that the given adaptive receiver outperforms the conventional linear correlation receiver by a considerable margin in high NFR and low mobility (i.e., small Doppler bandwidth) scenarios.