Traditional LTE-R cross-zone''s handover algorithm usually uses an algorithm with a fixed handover hysteretic threshold and a fixed time to trigger.But when the train runs at a high speed,the success rate of the handover decreased significantly,which can not meet the requirements of the wireless communication system of high-speed railway for greater than 99.5% of the QoS.Through the analysis of handover process,measuring parameters and the control parameters,proposed a cross-zone handover optimization algorithm based on dynamic function of velocity.Three representative functions,inverse function,linear function,elliptic function were selected as dynamic functions to simulate respectively cross-zone handover success rate and the rate of radio link failure under three train running conditions at low speed,medium speed and high speed.The simulation results showed that the LTE-R cross-zone handover optimization algorithm based on elliptic function ensured significant improvement of the cross-zone handover success rate during the high speed running of the train,as well as relatively low rate of radio link failure,which is more suitable for the selection of switching time under the high-speed railway scenario.%传统的LTE-R越区切换算法,通常采用固定切换迟滞门限和延迟触发时间的切换算法.但是当列车高速行驶时,切换成功率明显下降,无法满足高速铁路无线通信系统对QoS大于99.5%的要求.通过对切换流程、测量参数、控制参数的分析,提出一种基于速度动态函数的越区切换优化算法.动态函数选取3种具有代表性的函数:反函数、一次函数、椭圆函数,分别对低速、中速、高速3种列车运行情景下,进行越区切换成功率和无线链路失效率仿真比较.仿真结果表明,基于椭圆函数的LTE-R越区切换优化算法,既保证了列车在高速运行时,越区切换成功率的明显提升,又保证了无线链路失效率相对较低,更适宜高速铁路情景下切换时机的选择.
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