LTE-U在城市轨道交通中的应用研究

Research on Application of LTE-U in Urban Rail Transit

随着LTE在城市轨道交通中的推广应用,授权频谱资源不足与城市轨道交通车地间数据传输需求的矛盾制约着车地无线通信系统建设方案的选择,利用非授权频谱实现LTE的LTE-U新兴无线技术有望缓解甚至解决该问题。通过对LTE-U的技术研究,分析其在城市轨道交通应用中的技术优势:移动和切换性能优异、传输时延小、抗干扰能力强、覆盖半径大、Qo S保障好、安全性高、可靠性高等特点。通过搭建LTE-U测试网络,在实验室进行120 km/h、140 km/h、160 km/h典型速度下加载CCTV和PIS业务测试;在80 km/h城市轨道交通线路上,采用A、B冗余组网测试,A网承载CBTC业务,B网综合承载CBTC、CCTV和PIS业务;选择在80～170 km/h的速度下搭建LTE-U网络,并进行CCTV和PIS业务测试。测试结果显示,LTE-U具有对城市轨道交通CBTC、CCTV、PIS业务的承载能力。同时,LTE-U在城市轨道交通的应用仍面临诸多挑战,如LAA技术的TAU有待开发、Standalone技术的多载波聚合产品不成熟以及其他非授权频谱产品的竞争等,最终提出在城市轨道交通中部署LTE-U的建议。

With the application and promotion of Long-term Evolution（LTE） in urban rail transit, the contradiction between the shortage of licensed spectrum resources and the data transmission requirements of urban rail transit has restricted the selection of the construction scheme for train-ground radio communication systems. However, LTE-U, an emerging radio technology which uses an unlicensed spectrum to achieve LTE, is expected to mitigate or even solve this problem. In this paper, the technical advantages of LTE-U（LTE in unlicensed spectrum） in urban rail transit are analyzed through the research of LTE-U technology, such as excellent mobility and handoff performance, low transmission delay, high anti-disturbance ability, large coverage radius, flexible deployment, better QoS support, and high safety and reliability. By setting up a LTE-U test network, CCTV and PIS service tests were performed in a laboratory at typical speeds of 120 km/h, 140 km/h, and 160 km/h; On the urban rail transit line with a speed of 80 km/h, the redundant networks A and B were used to test the ability of the A network to carry CBTC service, and the ability of the B network to carry CBTC service, CCTV service, and PIS service, comprehensively; On the 200 km/h high-speed passenger line, a LTE-U network was built with a speed range of 80 to 170 km/h to test the ability of loading CCTV and PIS services. The results show that LTE-U has the bearing capacity for PIS, CCTV, and CBTC services in urban rail transit. The paper indicates the application of LTE-U in urban rail transit faces challenges such as the development of LAA technology＇s TAU, the immaturity of Standalone technology＇s multi-carrier aggregation products, and the incremental competition from other unlicensed spectrum products. Finally, some suggestions are presented.