Research On Seamless Dual-Link Handover Scheme Based On Beamforming For High-speed Railway

High-speed railway has become one of the most efficient and convenient means of transportation for people.How to guarantee the safe operation of high-speed railway and the experience of passengers' communication better are problems that the high-speed railway wireless communication system needs to solve.Due to the extremely high mobility of the high-speed railway,it brings problems such as signal instability and frequent handover to the high-speed railway wireless communication system,resulting in a sharp drop in communication quality.In order to improve the handover performance of high-speed railway,this paper proposes a handover scheme based on beamforming technology for high-speed railway,the specific work content is as follows.Firstly,this paper combines the beamforming technology with traditional seamless dual-link handover scheme to propose a novel handover scheme.Which is the target base station uses the beamforming technique to assign a gain beam to cover the entire overlapping area when the train travels to the cell overlapping area to enhance the received signal strength of the target base station received by the handover antenna,this measure optimizes the handover opportunity and improves the handover performance.And the handover algorithm and handover procedure of the proposed handover scheme are also described in detail,so that a clearer statement is made on the proposed handover scheme.Secondly,this paper optimizes the handover condition in traditional handover scheme,considering the communication link connection of the communication antenna during performing handover.In this paper,the handover triggering is not only to satisfy the condition that the received signal strength of the train received from the target base station is greater than the received signal strength of the source base station a threshold,but also the received signal strength of the source base station received by the rear antenna should meet the minimum threshold for the train to maintain normal communication to ensure the "seamless" handover.This improvement completes the handover condition.Morever,this paper improves the handover mode of the traditional seamless handover scheme,that is,allows the handover antenna to perform multiple handovers.After the handover antenna fails for the first handover,the rear antenna does not need to disconnect its communication link to join the handover,but allows the handover antenna to continue performing handover until its maximum number of handovers is reached.Meanwhile,considering the influence of inter-cell co-channel interference on the received signal strength and handover performance,this paper analyzes the co-channel interference when the antenna is receiving the signal,and uses the signal-to-interference ratio for replacing the received power to indicate the received signal quality to further optimize handover opportunity and improve handover performance.Finally,this paper establishes a probability analysis model for the proposed handover scheme to analyze the handover probability,handover failure probability and communication outage probability,and the corresponding expressions are also given.The handover success probability is also added in performance analysis to describe the relationship between the handover position and the handover success probability.