Performance comparisons of fixed and adaptive beamforming techniques for 4G smart antennas

Much attention has been paid to the design and implementation of adaptive antenna arrays (also called smart antennas), intended for use in current and future wireless communication systems. The motivation is that employment of such array antennas can significantly increase the range and capacity of wireless systems by orienting the main beam towards the desired direction while simultaneously placing nulls toward the interferers (thereby increasing the signal to interference SIR ratio). In this paper, various adaptive beamforming algorithms have been compared based on nulls location, gain and half-power beamwidth (HPBW). Performance comparisons of matrix inversion beamforming algorithm (used for fixed beamforming) and LMS, RLS (used for adaptive beamforming) are investigated in terms of their effects on main beam scanning, resolution and convergence. In particular, the effects of nulls location on the gain and half power beamwidth (HPBW) of main beam have been investigated for the fixed vs adaptive beamforming algorithms.