QoS-Aware Scheduling of Airship-Assisted Millimeter Wave Communications for High-Speed Railway

With the rapid growth of mobile data demand, millimeter-wave (mmWave) communication has become one of the candidate technologies to improve data rates for high-speed railway (HSR). However, the cost of covering HSR lines through terrestrial base stations (BSs) alone is unaffordable, especially in remote areas. In this paper, we consider a scheme of the airship-assisted mmWave communication for HSR in the space-air-ground integrated network (SAGIN). Furthermore, we introduce an optimal scheduling problem of maximizing the number of flows that satisfy the quality of service (QoS) requirements between the airship and the train's mobile relays (MRs). To solve the above problem, we propose a MR selection algorithm to determine the number of MRs within the airship's coverage at every frame. Then we propose a max-flow scheduling algorithm based on the MR selection algorithm, which can increase the number of successfully scheduled flows by optimizing the scheduling order of the flows. Finally, simulation results show that our proposed algorithm can effectively improve the number of successfully scheduled flows and bits. We also verify that the proposed algorithm can further improve the system performance with increasing the number of MRs.