Power Allocation with Buffer Constraint for Distributed Antenna System in High-Speed Railway Scenarios

To meet the increasing demands of high data-rate service in high-speed railway (HSR) scenarios, the two-hop architecture with distributed antenna system (DAS) is a good choice. In this architecture, the transmit and receive sides of HSR system are both equipped with distributed antennas, then base stations (BSs) communicate with users via mobile relays (MRs) on the top of train. Thus, the data will be buffered when the wireless transmission rate can not satisfy the requirement of data arrival rate. In this paper, we focus on the efficient power allocation method with buffer and delay constraint on the basis of predicted path loss characteristic in downlink HSR communications. Firstly, the relationship between the data arrival rate and instantaneous wireless transmission rate is analyzed where BSs transmit with constant power. Secondly, the transmit power optimization problem with the requirement of buffer size and delay is formulated. The optimal power allocation scheme can be obtained through Lagrangian dual method. Simulation results demonstrate that the proposed power allocation scheme can achieve a lower consumed power and avoid data overflow and infinite delay as well.