Abstract

With the emerging demands of new communication services, the contradiction between capacity demand and spectrum shortage of railway communication systems becomes more severe. How to provide broadband communication services has become the key goal of future smart high-speed railway (HSR) systems. Millimeter wave (mm-wave) frequency band has abundant spectrum resources and can provide communication services with large bandwidth. However, due to the high-speed of the train as well as the complexity and dynamics of environments, the communication link may be blocked randomly for a short time and will also lead to frequent handovers. In this paper, we adopt the promising intelligent reflecting surface (IRS) technology for a mm-wave HSR communication system. In order to improve system capacity, IRS is deployed to improve reflection transmission links, and optimization algorithms are designed for transceiver beamforming and IRS phase shift. In addition, given the specificity of the HSR scenario, we also formulate the average system ergodic capacity maximization problem and obtain upper bound on the average system ergodic capacity with statistical channel state information (CSI). Through extensive simulations, we verify that the proposed scheme performs significantly better than the other two baseline schemes in terms of average system throughput and average system ergodic capacity.