Characterization and Development of Algorithms for Array Processing Architectures of Adaptive Antennas in Wireless Communication

Abstract

To set up an efficient wireless and mobile communication system, it requires a characterization of its environments and its components, in particular, its array processing architecture. This research work has been prompted by the current thrust in wireless and mobile communication technology to look for new approaches and technologies to improve performance of array processing architectures, thereby improving spectrum efficiency and to be able to support the projected capacity demands with the introduction of new personal communication services. The results presented in this thesis constituted four targets. First, new side lobe control beamforming algorithms for array processing architectures of CDMA based wireless communication systems are developed for interference reduction. It is shown that conventional arrays based on nulling procedure are unlikely to be applicable in practical CDMA based wireless communication systems for large number of interferers. The role of FrFT in providing taper of varying side-lobe level and beamwidth is investigated. A procedure for tapering in FrFT domain is proposed, which can be used with optimal array processing also. The weights obtained by FrFT taper are found to be practically realizable weights. The one to one relationship between capacity and beampattern is established. A relationship between the side-lobe level and number of interferers is derived. A new algorithm capable of synthesizing Chebyshev-like low side-lobe beam patterns with adjustable beamwidth and steering invariance is developed. The proposed algorithm is shown to handle large angular spreads of interference effectively. The increase in information capacity and the performance improvement in various performance metrics viz; Signal-to-interference-plus-noise ratio (SINR), Normalized SINR (NSNIR), Array gain (AG) and Mean square error (MSE), of array processing architectures, by implementation of new beamforming algorithm, are investigated. It is shown through Monte Carlo simulations that for large number