Efficient Hybrid Beamforming for Multi-Group Multicasting in mmWave Systems

This paper investigates multi-group multicast hybrid beamforming with a large-scale antenna array in millimeter wave (mmWave) communication systems. We consider the max-min fair (MMF) problem and aim to design analog/digital hybrid beamformer to maximize the minimum signal-to-interference-plus-noise ratio (SINR) of all users under the transmit power constraint. This non-convex coupling problem is decomposed into optimizing analog beamformer and digital beamformer separately. The analog beamformer is first designed to fairly maximize the smallest SINR as well as mitigate the inter-group interference. To achieve this goal, a codebook-based analog beamformer design is proposed for high phase resolution cases and a codebook-free analog beamformer design is presented for low phase resolution cases. After determining the analog beamformer and obtaining effective baseband channel, the digital beamformer is calculated via semi-definite relaxation (SDR) approaches. Simulation results validate the effectiveness of the proposed hybrid beamforming algorithms for multi-group multicasting in mmWave systems.