Research On Wireless Sensor Network For High Speed Train Operation Environment Monitoring

Operation safety is the precondition of high speed railway transportation. With the increasing of high speed railway mileage in China, operation environment monitoring of high speed train has been put forward higher requirements. At present,for the high speed train operation environment monitoring, there're various objectives and demand. But the data transmission of the most existing system is still based on the wired network, and the lack of coordination between various monitoring systems raise the cost of construction and maintenance. Characteristics of wireless sensor network(WSN) such as low power consumption, self-organization, wireless and invulnerability is quite suitable for data monitoring application of industrial grade. It can achieve a wide range deployment along railway lines, ensure the breadth and accuracy of data collection, reduce environment monitoring cost, construction cost and maintenance cost. WSN technology can effectively meet the needs of large-scale deployment and long-term on-line monitoring in key areas and remote areas along the high speed railway lines.In this thesis, WSN technology is fully applied to high speed train operation environment monitoring from the whole perspective. Starting from the actual demand of high speed train operation environment monitoring system, in this thesis, system architecture and logical architecture of the WSN-based high speed train operation environment monitoring system are proposed, the key technology such as topology method, node deployment method, routing protocol of the ground WSN and the communication scheme of the vehicle-ground WSN are studied. Using natural disasters and foreign invasion monitoring as an application example, the WSN-based natural disasters and foreign invasion monitoring system is designed.The main achievements of this thesis are as follows,(1) This thesis analyzes the current situation and business requirements of high speed train operation environment monitoring, summarizes the basic network structure of WSN system and the typical WSN architecture model. In the thesis, the system architecture based on SOA and WSN of the high speed train operation environment monitoring system is developed. Combined with the business scope, the logical structure of this WSN-based environment monitoring system is set up.Furthermore, the architecture and networking method of each type of WSN are studied.(2) Based on the deep research of WSN topology, a hybrid hierarchical topological structure for ground WSN is proposed. This topology fully combines the characteristics of the monitoring equipment and infrastructure along the railway. It consists of two parts, the local network and the backbone network. In the backbone network design, all systems are under unified management and unified information transmission, in order to avoid duplication of investment, lack of coordination and mutual interference. Aiming at the linear-distributed characteristics of the backbone network, the optimal deployment strategy of energy-balanced uneven nodes deployment is proposed, which can effectively avoid the "energy hole" problem in linear WSN.(3) Based on the optimal node deployment strategy of linear WSN, a routing protocol for linear WSN along railway lines is proposed. In this protocol, the network lifetime and priority of monitoring information are considered. According to the degree of importance, the data packets are divided into different priorities. Under the premise of balanced network energy consumption, the data packet forwarding model and data propagation delay model are established to maximize the number of packets transmitted within the network life cycle. Furthermore,the fault types that may occur in the link are analyzed, the node failure handling strategy is proposed.(4) The existing wireless communication technology and train-ground communication technology are discussed in detail. In this thesis, the train-ground WSN technology is applied to the real-time wireless communication between the train and ground facilities. Through P2P field tests on a variety of wireless communication technologies in a real high speed operating environment, the most suitable communication technologies for this scenario are selected. Furthermore, the vehicle-ground WSN based on relay transmission is designed. By optimizing the communication module and relay transmission method, the data transmission capacity of this vehicle-ground WSN is greatly improved, the feasibility of this method is verified by indoor test, outdoor test and high speed railway field test.(5) According to all the above research, the architecture and networking scheme for WSN-based natural disaster and foreign intrusion monitoring system are proposed.based on this architecture and networking scheme, the WSN-based natural disaster and foreign intrusion monitoring system is designed, hardware and software of this system are selected and developed. This system can solve the problem of high wiring cost and non-flexible monitoring in existing system. This thesis provides great technical support for the industrial application of this WSN-based system.