高速列车车载系统下智能切换机制的设计及性能分析

高速列车车载方案因成本低，支持多种通信制式，越区切换管理简单等优点而成为高铁通信研究的热点领域。但作为世界性的难题，切换技术的研发目前很难取得突破。因此，为了满足飞速发展的高铁技术的需求，探讨现有的越区切换管理的机理，改进切换模式，也能同样有效降低通信时延，达到提高通信质量的目的。本课题为此首先从理论上探讨高速车载通信环境中，通信质量受列车时速变化影响的统计分布规律；基于光切换技术，设计新的智能切换机制；研究依据列车速度动态地优化和控制智能切换机制的算法，以期获得高效、可靠、经济的无线通信协议；另外，现有的数据排队模型没有充分考虑高速环境下，越区切换的频繁性及列车的高速移动性，因此又拟以列车速度为关键参数，对智能切换的数据业务流建立休假Markov排队模型，以获得系统的性能指标体系；最后通过NS2平台验证智能切换方案的有效性，为高速车载环境下，新型无线通信系统的设计和开发提供理论依据。

Vehicle system of express train becomes one of the hot fields in high-speed train communication, because of several advantages, such as low cast, supporting multiple communication formats and easy to hand-off switching management. Most studies focus on the switch technology, but as a worldwide problem, it’s hard to make a breakthrough at present. Therefore, in order to satisfy the rapid development of high-speed train technology, we will explore the mechanism of existing handover management and modify the switch mode. What we will do can also reduce the communication delay effectively and achieve the purpose of improving the quality of communication. According to the theoretical study in high-speed vehicle communication environment, this project first discusses the statistical distribution law of the communication quality which is affected by the change of train speed. Basing on the optical switching technology, a new intelligent switching mechanism is designed; We will optimize the algorithm of dynamic optimization and control of intelligent switching mechanism based on train speed, for finding a efficient, convenient, economic method to improve the communication quality; Besides, the existing data queue models do not fully consider the frequent hand-off switching and the high speed mobility of the train in the high speed environment. So it is proposed to establish a vacation Markov queue model for the intelligent switching data service flow with the train speed as the key parameter in order to obtain the performance index system of the vehicle system. Finally, this project will use NS2 platform to verify the validity of the intelligent switching scheme, hoped to provide a theoretical basis for the design and development of new wireless communication system in high-speed vehicle environment.