Research On LTE-R Handover Optimization Algorithm For High-speed Railway

With the rapid development of Chinese high-speed railway,how to satisfy the requirement of the high-speed railway and voices along with data services for railway passengers,became an urgent problem to promote the development of railway.Through LTE system has several advantages such as high speed of transmission rate,lower time delay of control and user,flattening and the IP network structure.UIC had assigned the LTE system as the development direction of railway communication system.The rapid development of railway communication system will provide technical support for online operation monitoring,online maintenance detection and online video back as the rapid development of railway communication system.Cross-zone handover is an important part of the high-speed mobility management.Meanwhile,the high-speed railway has the characteristics of high speed,switching frequently and linear distribution of zone.Fast and effective handover algorithm is an important foundation of guaranteeing the LTE communication system with good service quality under high-speed railway.An adaptive optimization cross-zone handover algorithm based on dynamic functions of speed is proposed in the thesis.It can solve the adjustment problems of the handover hysteresis threshold and time to trigger at different speeds effectively and meets National Railway Administration's requirement of the People Republic of China that the cross-zone handover success rate must be higher than 99.5%.This optimization handover algorithm plays an important role in the two cases of early handover and late handover in mobile robustness optimization.It can reduce unnecessary handover and avoid the waste of system resources.The main contents of the thesis are below.(1)The environment of high-speed railway is complex.Firstly,the wireless network planning for high-speed railway communication base stations in the mountain environment was planed and reference signal received power,reference signal received quality and signal to interference plus noise ratio were simulated.(2)An adaptive cross-zone handover optimization algorithm based on dynamic functions of speed was proposed.The proposed optimization algorithm can adjust handover hysteretic threshold and time to trigger in real-time.Then the handover optimization algorithm was designed and the control parameters were calculated.The system simulation parameters were set reasonably and the protection of the locomotive station was taken into consideration.(3)Through the indicators of pros and cons,the effectiveness of the proposed algorithm was verified.The positive indicators include handover trigger rate and handover success rate,while the reverse indicators include radio link failure rate,ping-pong handover rate,allowed handover times in theory.The simulations results show that the optimization algorithm can improve the quality of service effectively.