Energy Efficient Analog Beamformer Design for mmWave Multicast Transmission

Abstract

Millimeter wave (mmWave) communication is considered as a key enabling technology for 5G cellular networks because abundant spectrum in mmWave bands can provide multi-gigabit communication service. Analog beamforming architecture, which employs energy-efficient phase shifters (PSs) instead of energy-hungry radio frequency (RF) components, has emerged as a promising solution to overcome severe propagation loss of mmWave channels. On the other hand, multicast communication is another efficient approach to address the dramatic traffic demand by utilizing the broadcast nature of the wireless medium. This paper investigates energy efficient analog beamforming in mmWave single-group multicast communication systems. We focus on max–min fair (MMF) problem and aim to design the analog beamformer to maximize the minimum signal-to-noise ratio (SNR) over all users subject to a transmit power constraint. The analog beamformer design with infinite and finite resolution PSs are both studied. While the constraints of PSs make the problem intractable, we propose an alternative low-complexity algorithm, which iteratively determines each element of analog beamformer. Furthermore, we also investigate the asymptotically optimal beamformer designs and provide asymptotic performance analysis for large-scale mmWave multicasting systems. Extensive simulation results illustrate the effectiveness of the proposed analog beamforming designs in mmWave multicast systems. Besides, numerical results also demonstrate that the asymptotic performance of the proposed scheme is close to the optimal case.