高速铁路车地宽带通信软切换技术研究

Study on Soft Handover Technology in High-speed Train-wayside Broadband Communication System

LTE在高铁环境伴生了无法克服的高频次快衰落,LTE硬切换缝隙内的快衰落又伴生乒乓切换。针对LTE存在快衰落问题,提出了抗多普勒频移的空口技术;针对LTE硬切换缝隙问题提出了移动MPLS软切换技术。MPLS不是与LTE空口而是与抗频移空口技术结合形成移动MPLS系统。MPLS标签堆栈构建双层隧道,外层隧道利用FRR“先接通、后断开”实现软切换,消除切换缝隙;内层隧道封装IP包,与切换无关,实现业务无损切换。试验表明,移动MPLS软切换在高铁环境下可构建车地宽带大通道。

LTE comes with invincible frequent fast fading under the environment of high-speed railway,while the fast fading in the LTE hard handover gap comes with ping-pong handover.In response to the fast fading in LTE,an air interface technology against Doppler frequency shift was proposed.To address the LTE hard handover gap,a mobile MPLS soft handover technology was proposed.Mobile MPLS was formed from the combination of MPLS with anti-frequency shift air interface instead of LTE.The MPLS label stacking technology was used to create double-layer tunnels,with outer tunnel relying on FRR‘make-before-break’to achieve seamless soft handover and eliminate handover gap,and inner tunnel encapsulating IP packet unassociated with handover procedures to achieve service lossless handover.The test results prove that mobile MPLS and its soft handover could achieve vehicle-wayside broadband communication under the environment of high-speed railway.