Adaptive Beamforming and Power Allocation for mmWave Communication in High-Speed Railway

Millimeter wave (mmWave)-based massive multiple-input multiple-output (MIMO) beamforming technology is one of the key technologies in the fifth-generation (5G) network. In this paper, we apply mmWave to high-speed railway (HSR) communication scenario to meet its increasingly growing demands for tremendous data rate and reliable mobile services. The HSR mmWave communication system uses a control/user (C/U) plane separation structure; that is, control information and user information are transmitted through the high-frequency micro base station (BS) and the low-frequency macro BS, respectively. Then, an optimized beam width and power allocation scheme is proposed, which is combined with the mobile relay (MR) technology to utilize the architecture of the large-scale antenna beamforming. In the proposed scheme, we introduce a power factor related to the change of train speed. According to the power factor, the service beam width is adjusted dynamically and the transmit power of the beams from two simultaneously served mmWave access points (APs) is jointly calculated. Simulation results show that, compared with the traditional uniform beam width scheme, the proposed adaptive beam width and power allocation scheme can maximize the total service volume within the maximum transmit power range.