Hybrid beamforming with two bit RF phase shifters in single group multicasting

Abstract

In this paper, an efficient hybrid beamforming architecture combining analog and digital beamforming is proposed to reduce the number of radio frequency (RF) chains. It provides a good compromise between the higher degree of freedom of digital beamforming and hardware cost and complexity. In this hybrid system, two bit RF phase shifters are used as analog beamformers due to the fact that this enables the conversion of the combinatorial optimization problem to a continuous programming formulation. The overall optimization problem for the joint design of digital and analog beam-forming weights is formulated as a quadratic-cost problem which can be solved iteratively by exact penalty and semidefinite programming. Simulation results show that the proposed method designs hybrid beamformer effectively and it performs better than antenna selection for the given multicasting problem.