A Clustering Approach to optimizing Beam Steering Directions in Wireless Systems

Abstract

Directional beamforming with large antenna arrays is key to mitigating the substantial signal loss experienced at the millimeter wave frequency band, important to fifth generation (5G) cellular systems and next generation wireless local area networks, where it entails a significant increase in the number of beams. This paper is motivated by the realization that the underlying problem of finding the optimal set of beam steering directions will benefit from fundamental signal processing methodologies, and specifically from basic principles and algorithms for cluster analysis. Earlier work by authors established the equivalence between the problem of optimizing a set of beam steering directions and the classical problems of clustering and quantizer design, albeit with an unusual distortion measure. Subsequently in [1], a k-means-like approach was derived to optimize beam steering directions and guarantee convergence to at least locally optimal solution. The main contribution of this work is the derivation of a global optimization approach within the deterministic annealing framework, to circumvent poor local optima that riddle the cost surface. Simulation results show that the approach delivers considerable gains over the baseline uniform beam steering technique, specifically, up to 6 dB and 13 dB gains, in terms of average and 10th percentile of the power array factor, respectively, as well as up to 6.5 dB gain in the average Signal-to-Noise Ratio (SNR).