Improved adaptive LMS algorithm for DS-CDMA Receiver over AWGN and fading channels

Abstract

Over the last decade, because of its distinct characteristics, the spread spectrum technique plays an important role in CDMA (Code Division Multiple Access) communication system and has been first used for military applications. This paper develops adaptive blind Least Mean Square (LMS) algorithm to DS/CDMA in the presence of Additive White Gaussian Noise (AWGN) and multipath Rayleigh fading channel. We evaluate adaptive blind least mean square algorithm and receiver structures and access their performance in combating noise and fading effects of the channel. Co-Channel Interference (CCI) and intersymbol interference (ISI) are the two major hindrances that degrade the better performance of wireless communication systems.   To compensate these channel distortion, Equalizers may be used. To obtain the interference suppression, Adaptive equalizer structure is used by the receiver followed by de-spreading and demodulation. Execution of DS/CDMA system in presence of auto adaptive Least Mean Square equalizer algorithm is analyzed using MATLAB. Simulation result shows that better performance is obtained using proposed algorithm than the conventional one in the presence of both AWGN and fading channel.

Keywords- DS/CDMA, Equalizer, Least Mean Square, Rayleigh fading, Spread Spectrum