Blind Antenna Beamforming in DS-CDMA Systems using Nonlinear Networks

Abstract

The capacity of code division multiple access (CDMA) systems is limited by interference and can therefore be increased by techniques that suppress interference. Adaptive techniques using multiple antennas are generally used for interference suppression in the receiver. Blind adaptive schemes are attractive as they do not require any training sequence. Most of the commonly used blind algorithms optimize some cost functions that are generally non-convex and nonlinear functions of tap weights, when implemented using linear filters. Therefore the use of nonlinear structure that can form nonconvex decision regions is more suitable for this purpose. In this paper a blind antenna beamformer using constant modulus algorithm (CMA) has been implemented, where the beamforming network has complex nonlinear functions. Simulation results indicate better performance than the linear filters in terms of signal to interference and noise ratio (SINR).

Indexing terms:

• Blind beamforming
• Adaptive techniques
• CDMA systems
• Nonlinear functions