基于功率-距离的LTE-R切换算法优化研究

传统的基于长期演进的铁路移动通信系统(long term evolution-railway，LTE-R)切换算法对切换参数的选择不能很好地适应列车的高速移动，由此导致的“切换滞后”现象容易造成更多的失败切换，影响列车运行控制和旅客无线通信体验。当列车高速穿越小区时，对越区切换的要求更加严格，简化信令流程以及实现快速切换是LTE-R急需解决的问题。以减少错误触发和实现快速切换为出发点，提出一种基于功率-距离的切换优化方案，充分考虑速度对切换参数的影响，并加入距离因素，只有当列车到达一定触发位置时才可以进行触发判断，如满足条件则直接进行切换。该算法在避免列车提前错误触发的同时舍弃触发时延(time to trigger， TTT)指标，在一个测量周期内即可实现快速切换。仿真结果表明，所提的方案能够更好地保证高速环境下列车的切换成功率。

Research on optimization of LTE R handover algorithm based on power distance

The traditional long term evolution-railway(LTE-R) handover algorithm for selection of handover can not adapt well to the high speed train movement, and the handover hysteresis is likely to result in more handover failures, impairing the train operation control and the wireless communication experience of passengers. On the other hand, when trains pass through a community at high speed, the requirements for handover are more stringent, and the problem of simplifying the signaling flow and achieving rapid handover needs to be solved urgently. Thus, a handover optimization scheme based on power and distance is proposed to reduce inaccurate handover and achieve fast handover. Not only the influence of speeds on handover parameters is taken into full consideration, but the distance and power are also taken into account in the optimizational algorithm. Only when the train reaches a certain trigger position can the trigger judgment be made, and the switch is carried out when the power condition is satisfied. The proposed algorithm avoids early error triggering of the train and discards the time to trigger(TTT), so the rapid handover can be achieved within one measurement cycle. The simulation results show that the suggested scheme can better ensure the handover success rate in high speed environment.