高铁DTN网络无码率编码路由与中继协作传输的关键技术研究

A novel network protocol architecture called Delay and Disruption Tolerate Network (DTN), combined with relay cooperative transmission technology, is presented in this proposal, so as to solve the problem of providing fast and reliable Internet access for high-speed rail (at the rate of over 300 km/h) environment. .The high-speed rail network may become unexpectedly partitioned due to the node's high-rate mobility, and hence lacking continuous connectivity. As an "overlay" architecture, DTN is intended to operate above the existing protocol stacks in various network architectures and provide a store-and-forward gateway function between them when a node physically touches two or more dissimilar networks. Furthermore, deployment of relay network must be taken into consideration in order to increase the coverage of the base-station and to meet higher throughput requirements..Firstly, several DTN network topology models and their optimization schemes suitable for high-speed rail surroundings are presented. Secondly, network code routing algorithms are introduced into relay cooperative communication, where the rateless erasure codes with lower complexity and better decoding performance are suggested to be established in advance. .On this basis, a cross-layer optimization problem is formulated to assign the relays to the destinations. With the proposed optimization model, the number of access points, the locations of deployment, and the selection of relay work modes are derived based on the system performance requirements. Thus, the requirement of the fast handover can be partially relieved. Finally, a test platform based on several high-performance PCs will be designed using the real channel information for the high-speed railway environment. With the test bed, simulation results can be validated and the algorithms can be optimized further.

为高速列车（速度超过300km/h）提供快速可靠的网络接入是目前迫切需要解决的问题。本项目将容迟与容断网络(DTN)协议架构和中继协作传输技术相结合，针对高铁列车快速移动的特点，首先对高铁DTN网络拓扑结构进行建模和优化；其次将基站直接数据传送与轨旁中继节点协作通过网络编码路由算法融合一体，尝试研究多中继节点的喷泉码构造形式，通过降低级联码译码的线性时间复杂度，构建适用于高铁DTN网络架构下的编码路由方案，达到降低网络负载的同时提升传输性能及吞吐量的目的；然后通过中继节点部署的跨层联合优化，结合铁路通信自身优势，如车体长、车路信道状态相对稳定等，减少快速切换对车地通信的影响；最后利用高速DTN网络环境中的信道信息，建立接近实际环境的仿真测试平台，验证和优化理论算法分析和仿真的结果。该成果将可为目前高速物联网背景下的宽带无线接入提供理论支撑和解决方案。

本项目首先分析高铁环境下的通信特点，利用认知无线电技术，基于认知移动中继的频谱感知算法和频偏估计算法，感知和预测空闲频谱，来增加高铁无线通信网络的可用带宽，进一步增加系统容量，实现更多用户的宽带无线接入。通过移动网络连通性分析结果发现，该网络连通性能随着终端节点移动的速度提高而急剧衰减。此时提出在高铁网络中采用DTN网络路由方案，以期改善高速网络接入性能。项目对网络拓扑结构进行建模和优化，通过仿真比较得出较优的方案；其次将基站直接数据传送与轨旁中继节点协作通过网络编码路由算法融合一体，尝试研究多中继节点的喷泉码构造形式，通过降低级联码译码的线性时间复杂度，构建适用于高铁DTN网络架构下的编码路由方案，达到降低网络负载的同时提升传输性能及吞吐量的目的。该成果将可为目前高速物联网背景下的宽带无线接入提供理论支撑和解决方案。后续的研究中将进一步通过中继节点部署的跨层联合优化，结合铁路通信自身优势，如车体长、车路信道状态相对稳定等，减少快速切换对车地通信的影响；在此基础上利用高速DTN网络环境中的信道信息，建立接近实际环境的仿真测试平台，验证和优化理论算法分析和仿真的结果。