Dynamic mmWave Beam Tracking for High Speed Railway Communications

With the worldwide deployment of the railway, high-speed railway (HSR) tends to evolve into an intelligent transportation system with efficient and green transportation characteristics. To meet the explosive growth of wireless data traffic in "smart rail", millimeter-wave (mmWave) communications are used to offer several Gbps data rate via beamforming structures by utilizing huge unlicensed bandwidth. In this paper, the beam tracking strategies for mmWave HSR communications are investigated, and a dynamic beam tracking strategy is proposed by adjusting the beam direction and beam width jointly, where the main idea is to maximize the sum-rate capacity while satisfying the critical quality of service (QoS) requirements. Then it boils down to a demanding non-convex problem, and a near-optimal solution is provided based on the problem decomposition and the genetic algorithm. Finally, along with the moving trains the proposed beam tracking scheme can provide near-optimal capacity performance with a low outage probability, and reduce the implementation complexity.