Adaptive antenna array algorithms and their impact on code division multiple access systems (CDMA)

Abstract

In mobile communications there is a need to increase the channel capacity. The increasing demand for mobile communication services without a corresponding increase in RF spectrum allocation (channel capacity) motivates the need for new techniques to improve spectrum utilization. The CDMA and adaptive antenna array are two approaches that shows real promise for increasing spectrum efficiency. This paper focuses on the application of adaptive arrays to the Code Division Multiple Access (CDMA) cellular systems. The adaptive antenna has an intelligent control unit, so the antenna canfollow the user, direct the radiation pattern towards the desired user, adapt to varying channel conditions and minimize the interference. Therefore there can be several users in the same channel in the same cell. The driving force of this intelligent control unit are special kinds of algorithms and we are going to investigate the performance of these different adaptive array algorithms in the CDMA systems. In this paper four each blind adaptive array algorithms are developed, and their performance under different test situations (e.g. A WGN (Additive White Gaussian Noise) channel, and multipath environment) is studied A MATLAB test bed is created to show their performance on these two test situations and an optimum one can be selected We shall also try to show the adaptive nature of the beam former in response to the change in the direction of arrival of the signal on the antenna array. The matlab program will plot a rectangular and polar plot for the signals of different users.

Keywords: Code I DivisionMultiple Access (CDMA), Adaptive(Smart Antenna), and Adaptive Array Algorithms.