一种提升高速铁路无线通信网络HARQ性能的方法

Method for Improving HARQ Performance of Mobile Communication System of High-speed Railway

在长期演进LTE无线通信系统应用到高速铁路环境时,较高的移动速度、复杂的沿线环境将给系统混合自动重传请求HARQ性能带来较大的不利影响。本文对LTE HARQ在高速铁路场景下的性能进行分析,结果表明,相对于不采用HARQ技术,带有HARQ机制的系统具有较低的误块率、较高的吞吐量;然而,相比于公网静止用户场景,高速铁路移动用户的性能有所下降;本文提出一种增强小区重叠区HARQ传输性能的机制。性能分析表明,保存错误包待接入目标小区后合并解码,可使这些数据包在目标小区重发时的错误率降低55%,并提升了吞吐量。相比于不降低最大传输次数的情况,此方案在切换触发前给新数据包提供了更多的传输机会,使接入目标eNodeB重传前转数据包时,吞吐量提升了12%左右。

In the case that the LTE（Long Term Evolution） wireless communication system is applied to high-speed railways , high moving speeds and complicated railway line environments impose great influence un-favourable for HARQ （Hybrid Automatic Retransmission Request ） performance . In this paper , the HARQ performance in high-speed railway environments was analyzed .It shows that the system with HARQ technolo-gy has lower block error rate and higher throughput as compared to the case without it . However , the HARQ performance in high-speed environments is not as good as that in the scenario of public networks where most of the users are with low-speeds . And then , a novel HARQ scheme was proposed , which could enhance the HARQ performance in the overlapping region . In this scheme , the number of maximum retransmission is re-duced w hen the train arrives at a predefined location , and the packets , w hich suffer transmission error or can not be acknowledged before handover triggering ,will be saved by the system ,and retransmitted by the target eNodeB（after the train accesses it） ,and then combined and decoded by the onboard UE（User Equipment） . Performance analysis show s as follow s ：T he error rate decreases by 55% w hen these packets are retransmitted in the target cell ;compared to the situation with the fixed number of maximum retransmission , the proposed scheme provides more opportunities for new packets to be transmitted before handover , thus the throughput increases by about 12% when target eNodeB retransmits those forward packets .