Distributed Antenna-Based Optimized Handover Algorithm For High-speed Railway Broadband Communication System

ABSTRACT:With the quick development of high-speed railway over the world, the research of next generation mobile communication technology used in high-speed railway mobile communication already turns into a current hotspot. But the wireless broadband communication in high-speed railway also faces many challenges:the severe Doppler shift, the penetration loss, frequent handover, high outage rate etc. Among the above, the handover is the key to achieving seamless access and enhancing the communication performance for high-speed railway. Therefore, it becomes meaningful to study the handover optimization strategy for the high-speed railway wireless broadband communication system.Firstly, this paper introduces several representative vehicle-to-ground high-speed railway mobile communication solutions, and then analyzes the merits and drawbacks of the solutions, especially LTE-A and DAS communication systems. Overall, there has not been a complete solution to solve existing problems in the high-speed railway mobile communication system, and not yet a solution which combines the key technologies of DAS and LTE-A to achieve seamless access and high data transmission for high-speed railway mobile broadband communication.Based on LTE-A and DAS, this paper proposes an optimized handover scheme in high-speed railway wireless broadband communication. First, this paper analyses the disadvantages of the existed handover schemes, then gives a detailed description about the proposed network architecture for the high-speed broadband wireless communication system of based on the LTE-A and DAS. In the proposed scheme, when the train is into the same logic cell, the corresponding wireless carrier frequencies of the trackside RAUs are the same. Thus, in the coverage of the same logic cell, the train’s radio transmitting and receiving frequencies are not changed. Therefore, if CCS controls a large number of RAU, then the cell coverage is broadened, and the handover can be avoided in a long distance, which can avoid frequent handover. However, when the train is across the overlap area, the handover will inevitably happen. In this paper, we introduce a dual-link dual-antenna seamless handover scheme. When handover begins, the front antenna first triggers handover. And the rear antenna still remains the data transmission link with the network. If the handover triggered by the front antenna fails, the rear antenna will initiate handover for the second time, which can increase handover success rate and guarantee a seamless data transmission. Finally, by means of theoretical analysis and simulation, the performance of the proposed handover scheme is analyzed and verified. Compared to the standard LTE single-antenna handover scheme with MRS, the proposed handover scheme can reduce handover outage probability and communication interruption probability with low implementation overhead, which guarantees the reliability of the high-speed railway wireless broadband communication.