Joint Beamforming and Power Allocation in Millimeter-Wave High-Speed Railway Systems

Achieving high data transmission rate in the highspeed railway (HSR) communications has always been the significant yet challenging goal. Unfortunately, through an enormous number of measurements, current spectrum efficiency in HSR scenarios is still far from satisfactory to meet the data rate requirements for HSR passengers. To tackle this problem, we investigate the power allocation in the extremely time-varying millimeter-wave (mmWave) HSR systems with hybrid beamforming in the paper. With the purpose of maximizing the achievable sum rate, we first formulate a joint hybrid beamforming and power allocation problem in the mmWave HSR channel model. Then we obtain the solution of beamforming design. Finally, for the sake of achieving dynamic power control, a low-complexity iterative optimization approach is proposed. The numerical results indicate that the proposed iterative algorithm is capable of achieving a significantly higher spectral efficiency compared with the existing schemes.