Research Of Handoff Algorithm In High-speed Railway System

GSM-R is a communication system for railway. It carries all communication business between train and base station. As high-speed railway develops, its communication system requires higher and higher quality. As a result, GSM-R will be replaced by LTE in further.Handoff algorithm relates to the QoS (Quality of Servers) of GSM-R very much. A properly designed handoff algorithm should not only promise connection of network, lower switching load of the system, but also maintain higher QoS. After analyzing the drive test data of GSM-R by data mining, we found three key factors:received signal strength, co-channel interference, and train speed. This test synthesizes these three factors and proposes a probability of satisfied communication model (PoSC), which reflects the QoS of the base station. Then puts forward a handoff algorithm based on PoSC. Numerical results are presented to demonstrate the feasibility of the proposed algorithm. The number of handoffs can be as small as 1, the handoff delay is low, and the handoff location is near the center of the two base stations, these are all obviously better than a compared traditional algorithm.In this paper, an optimization scheme for LTE-R is also proposed. Adjacent cell list optimization is considered, in order to reduce handover time and ping-pong effect. Handover judgment with adaptive threshold is proposed, which considers both RSRP and RSRQ.