Along with development of railway modernization, the train speed increases gradually, which causes the train to handover frequently when it passes through the cells of the GSM for Railway (GSM-R) network. Communication can be interrupted during the hard handover process (break-before-make), which will lead to some safety problems in train operation. Traditional handover optimization schemes only focus on improvement in handover processes in the single-layered network and ignore the existing redundant configuration characteristics of the GSM-R network. This paper proposed an optimized scheme, in which we combined different BSs in the GSM-R two layer redundant network into a virtual cell serving for the train and adopted cooperative communication between the on-board dual-antenna and virtual cell. The scheme takes full advantage of the redundant network configuration and achieves seamless handover when the train traverses through the cells. Simulation results show that the proposed scheme can decrease the outage probability remarkably during handover and guarantee safe train operation.%随着铁路现代化的发展,列车运行速度逐渐增加,由此导致列车在穿越GSM-R网络小区的过程中需要频繁地执行越区切换操作.由于GSM-R网络先断后连的硬切换方式必然造成切换过程中存在通信中断等问题,对行车造成一定的安全隐患.传统的切换优化方法仅针对单层网络中移动台越区切换过程进行改进,忽视了GSM-R系统现有的冗余网络配置特点.本文提出一种将GSM-R双层冗余网络中的不同基站组成一个为列车服务的虚拟小区,并采用车载双天线与虚拟小区进行协作通信的方案,以充分利用冗余网络配置特点,从而实现列车穿越小区过程中完成无缝切换操作.仿真结果表明:所提出的方案使切换中断率明显降低,为列车的安全运行提供了可靠保证.
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