Research On Multipath Routing Technology For Urban Rail Ad Hoc Network

With the significant acceleration of urban scale expansion,the numbers and densities of urban population are increasing,and the contradiction between residents’ travel demand and urban transportation supply is becoming more and more prominent.The status of urban rail transit is steadily increasing in the field of public transportation because of its large capacity,fast speed,environmental protection and safety.As new information technology develops,urban rail transit is moving toward the direction of intelligence,which also leads to a significant increase in the demand for urban rail transit communication.At present,domestic and foreign urban rail transit mainly adopts Communication Based Train Control(CBTC)system to realize vehicle-vehicle and vehicle-ground communication under a centralized network architecture.However,if the central node is damaged or the link is interfered in this central network communication mode,the information transmission between the train and the ground cannot be carried out normally,which makes it impossible to meet the demand of next-generation urban rail transit vehicle-ground communication.The wireless ad hoc network can realize distributed control,increasing the network’s resistance to damage,and enhance the communication performance of the system.Therefore,the paper studies the technical solution and feasibility of applying the improved multipath routing technology of ad hoc network to urban rail transit ad hoc network,so as to improve the communication performance of urban rail transit vehicle-ground communication system and provide theoretical and technical support to meet the next-generation urban rail transit communication requirements.Firstly,based on the traditional multipath routing protocol of ad hoc network,the paper analyzes the problems of long routing discovery latency and single consideration of routing selecting process in the traditional AOMDV routing protocol.Then,combines the characteristics of urban rail transit ad hoc network to configure the a priori path using node location information to reduce the routing discovery latency.And,a multipath routing algorithm is proposed for carrying integrated vehicle-ground communication services,adaptively adjusting the number of transmission paths according to the demand of sending different service data,and then selecting the optimal path based on the link cost function to improve the transmission quality.The research results show that the algorithm can effectively improve the average end-to-end latency of different services vehicle-ground communication and improve the packet loss rate of data transmission to a certain extent.Secondly,the problem of link failure or node failure encountered during data transmission is considered,and the advantages and shortcomings of common routing maintenance strategies are comprehensively compared and analyzed.Then,combining with the characteristics of urban rail ad hoc networks,the disadvantages of the AOMDV routing algorithm using backup paths were analyzed.And,a local repair strategy based on the maintenance nodes of urban rail ad hoc networks for route maintenance.The scheme achieves fast route repair by dividing the whole path into several virtual cells and selecting appropriate maintenance nodes from them for establishing temporary links,and reduces the route repair time while maintaining route reliability as much as possible.The simulation results show that the local repair strategy based on maintenance nodes can shorten the route repair delay and improve the average end-to-end latency.