Research On Train-ground Communication Of Streetcar Signal System

Modern tram has many advantages, such as safe, comfortable, green, large capacity, fast and so on. So in the case of traffic jam and environment deterioration, tram is more and more popular in urban rail transit.Train-ground communication of streetcar includes not only communication between train and Automatic Train Supervision, but also communication between rain and Wayside Control Unit. Train can provide information of running status and location to ATS and get commands from ATS such as running plan, driving control and so on. When communicating with WCU, train can get the state of the switch in front of the route.In the signal system of the tram, efficient and reliable train-ground communication can ensure train running safely, fast and orderly. At present, the main technologies which realize information transmission between the car equipment and the ground equipment are loop wire technology, GSM-R technology, and WLAN technology and so on. These techniques can realize the information transmission between the equipment, but all of them have flaws, such as high costs, many difficulties about wiring etc. So other communication mode will be chosen to realize train-ground communication of streetcar in this paper.Wireless sensor network used widely in recent years is a new network technology. The network consists of the coordination node, the terminal node and the route node, which can complete the remote data acquisition independently,processing and transmission and it has been applied successfully in various fields such as monitoring of railway, intelligent home, monitoring of coal mine, etc. ZigBee is a highly reliable wireless communication protocol, which can meet the requirements from Wireless sensor network, such as low power consumption, low speed, low cost, etc. It has been successfully used in the communications field.In the topology of the communication network designed in the paper, stop board on both sides of the road is taken as route node. Automatic Train Supervision is taken as coordinate node. Tram and WCU woke as terminal node. These nodes communicate with each other under the Zigbee protocol. Information of state and command is transmitted between each other. The network can avoid cable and large-scale infrastructural engineering in other rail transit communication systems, which can not only reduce occupation of city road to accord with characteristics of rail transit in city, but also consistent with environmental philosophy.The overall design of the vehicle communication module, automatic train control system communication module and trackside controller communication module is carried out. This paper generally describes the current development situation tram technology, analyses the shortcomings in the communications technology of the tram, proposes a communication module between tram and land-based facilities based on the ZigBee protocol combining the characteristics of wireless sensor networks and vehicles to communicate the advantages of the system.The module using ZigBee protocol can make the communications betwween tram and ATS, tram and WCU communications become true. In order to achieve long-distance communications, this paper designs a routing node which can be placed next to the road or in the station to forwarding information. In addition to the hardware circuit of each sub module of the communication node, the design of the hardware circuit is carried out, and the design of its software is realized.In order to reduce the duplicate frames, error frame, frame sequential disorder, and transmission timeout during transmission, layer of security is added between Zigbee transport layer and application layer.The RSSP-I is used to ensure the reliability of communication between nodes. To ensure data transmission efficiency, the inter-module communication data frame format is designed in detailly.This design of the tram based on Zigbee technology to wireless communication module, can achieve an efficient and reliable transmission of information between the train and ground equipment.