Research And Performance Analysis On Phase-Only Beamforming Algorithm In Mimo System

In recent years, the demand for data transfer rate increases with the growing market of wireless multimedia and high-definition television in short distance high rate wireless personal area network (WPAN). Up to multiple GHz of unlicensed band width around the60GHz band makes high rate wireless data transmission possible. However, the serious atmospheric absorption and path loss in free space in60GHz should be overcame to design60GHz system.It is possible to integrate large amount of antenna element in small volume to form large-scale antenna array because of the short wave length of60GHz signal. The antenna gain provided by large-scale antenna array guarantees the reliability of60GHz communication. In the conventional full digital beamforming system, each antenna branch is devised with its own analog front end. This system demands high power consumption and high hardware complexity. Only the phase shifters are used to form phase-only analog beamforming (ABF) weights to further reduce the complexity. Hybrid analog/digital beamforming (BF) system is attracting increasing attention in the study on millimeter wave systems. In these systems, a relatively large number of antennas are connected to a less number of analog front-end chains so as to reduce both of the hardware complexity and power consumption.This paper investigates on optimizing phase-only ABF and digital beamforming (DBF) weights, with the objective of minimizing the total transmit power subject to the constraint of signal-to-interference-plus- noise ratio (SINR) greater than given values. Two kinds of evolutionary algorithm, the genetic algorithm (GA) and particle swarm optimization (PSO) algorithm are proposed to solve the non-convex optimization problem in this paper. The fitness functions which are used to evaluate the performance of individual in both proposed algorithm are the scale of the total transmit power. Chaos crossover probability, chaos mutation probability and elitist strategy are introduced into the GA in purpose of improving the operating efficiency as well as increasing the convergent rate. Cognitive factor and social factor constructed by the arccosine function, the adaptive inertia weight factor are adopted in PSO algorithm for the purpose of increasing performance. Simulations results under Gaussian channel environment reveal the advantages of the proposed GA and PSO algorithm over the existed iterative algorithm. Besides, under60GHz channel model, it is shown that the correlation on different subcarriers has profound impact on the performance of hybrid phase-only analog/digital BF.