| Abstract:With the large-scale construction of railways and the rapid spread of mobile Internet applications, the urgent need is to provide better Internet services for on-board users in the fast moving environment. Therefore, the current studies face the following challenges:the ground wireless network coverage, train-ground Internetworking mechanism, management for traffic of train-ground and intelligent management for on-board mobile Internet. The main works are as follows:Based on the research actuality, the four-layer centralized-access-mode-based on-board mobile Internet network architecture was designed. Then the six key technical problems which would research was determined.In order to realize the reasonable broadband wireless coverage along the railway trunk line, the private wireless network solution based on WMN and3G/LTE/4G was proposed. It would augment WiFi using3G/LTE/4G to obtain a higher bandwidth and lower investment. For the actual network deployment, the P-layer banyan-tree network topology was proposed to improve the feasibility of the implementing.For the problem of WMN which the multi-hop transmission bandwidth dropped while the transmission delay dramatically increased, the key main factors that influence transmission performance of the backbone link was researched based on the transmission model for backbone link, then the multi-radio mesh node structure and orthogonal channel allocation scheme was designed. On this basis, the wireless mesh router prototype system based on the IEEE802.11n standard and B.A.T.M.A.N. adv routing protocol was developed. Experimental results showed that its single-hop transmission bandwidth is greater than140Mbps, after eight hops the bandwidth is still greater than60Mbps, simultaneously has a smaller transmission delay. To achieve vertical handover in heterogeneous networks for on-board communication gateway, the heterogeneous wireless networks handoff strategy HWNHS based on utility function was designed. The system delay tolerance factor could be used to select the transmission link, in order to realize the optimal transmission performance and the largest transport income.For the fast-moving feature of on-board mobile Internet, the fast WMN switching algorithm FWMNSA was designed. By researched its handover performance through simulation, the thesis found that the moving speed, scan interval and the number of access channels would affect the handoff success rate of the terminal. Focus on the environment of train-ground Internetworking, the fast switching strategy for area FSSFA and the prototype system of on-board communication gateway was proposed. Experimental results showed that FWMNSA can realize fast switching and FSSFA will reduce the transmission delay of path update to600-700milliseconds, achieved the goal of fast and seamless switching.In order to optimize the traffic flows of train-ground Internetworking and improve the user experience, an Internet traffic model which is based on the ON/OFF model and overlay model was proposed to research the feature of Internetworking flows, then the prefetching access algorithm PAA was designed. Simulation and experimental results showed that the PAA can obviously improve the load capacity of the train-ground transmission link.To realize the intelligent management for the wireless coverage WMN, the node failure prediction processing strategy NFPPS based on B.A.T.M.A.N. adv was established, realized the automatic perception of the link quality and load capacity for mesh nodes, shorten the re-convergence time when the mesh node brake down, and enhanced the robustness of the network. Then the local management platform and cloud management platform for WMN were developed, realized the real-time, on-line intelligent monitoring and management for the WMN and Mesh nodes. There are62pictures,30tables and190references. |
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