【摘要】 目前CBTC系统采用LTE-M通信系统承载多种业务,其中列车控制业务关乎列车的运行安全,对传输的可用性要求极高,系统可用性亟需理论验证。从LTE-M系统数据包传输过程入手,结合CBTC业务模型和LTE-M系统传输模型,采用DSPN对数据包的传输过程进行建模,从理论上分析了数据包的传输时延,并在实验室环境下搭建了LTE-M系统测试平台来测试系统不同场景下的时延与吞吐量,根据测试结果确定不同场景下的DSPN模型参数,最后使用软件Time Net对DSPN模型进行仿真,分析数据包长度以及业务接入量对传输可用性的影响。结果表明,当数据包长度由100 bits增加至400 bits时,端到端传输可用性平均下降0.03%;当业务接入量由系统最大吞吐量的0.9倍增加至0.9999倍时,端到端传输可用性平均下降5%。该模型与计算结果可为实际工程部署提供参考。更多还原

【Abstract】 Long Term Evolution-Metro(LTE-M) system is currently adopted in CBTC systems to carry a variety of services, where train control service is related to the operation safety of the train, and requires ultra-high availability of transmission. Hence, system availability needs theoretical verification urgently. Starting from the packet transmission process in LTE-M system, and combining the CBTC service model and the packet transmission model of LTE-M system, deterministic and stochastic petri net(DSPN) is adopted to model the packet transmission process and the packet transmission delay is theoretically analyzed. Furthermore, a testing platform of the LTE-M system is established in the laboratory test environment to test the delay and throughput of the system in various scenarios, and then the parameters of DSPN model in different scenarios are determined according to the test results. Finally, the Time Net software is used to simulate the DSPN model and analyze the impact of the packet length and service access volume on the transmission availability. The results show that when the packet length increases from 100 bits to 400 bits, the endto-end transmission availability decreases by 0.03% on average. When the ratio of the service access volume to the maximum link throughput increases from 0.9 to 0.9999, the end-to-end transmission availability decreases by 5% on average. The model and calculation results can provide reference for the practical engineering deployment.更多还原