Research And Implementation Of The Cluster Structure Of The Wireless Train Dispatching Servers Based On P2P

WiMAX (World Interoperability for Microwave Access) is a kind of emerging wireless access technologies, could support a wide range of high-quality and high-capacity IP-based services and applications. So, different with the wireless train dispatching system (referred to as WTDS below) based on GSM-R, WTDS based on WiMAX is a kind of VoIP (Voice over Internet Protocol) system in essence. The call signaling control protocols which are widely used by VoIP are SIP and H.323. With the development of WiMAX technology, VoIP applied to railway becomes possible. The developed WTDS which is based on the project "The Application Research of WiMAX Technology on Railway" uses SIP as the call signaling control protocol, and the entire system have one SIP server which is used for managing the SIP signaling from clients. With the development of the system, the number of clients will bigger and bigger, only one server will cause single point of failure, performance bottlenecks and other problems. P2P could solve the problems above with its natural advantages.P2P (Peer-to-Peer) is also known as peer technology, is a kind of new network model. This network model is different from C/S model, nodes in P2P have high Autonomy and randomness, and each node in P2P cooperates with each other to complete tasks, relying on the participators’computing power and bandwidth, not only relying on a few servers in the network. So it could solve the problems mentioned above that single point failure and performance bottlenecks caused by single server.Through the research on the three network models of P2P, and combining the real requirements of WTDS, this paper introduces P2P technology into the developed WTDS, and proposes a system structure modification method on the developed WTDS. Through analyzing two kinds of combination methods of P2P and SIP (SIP over P2P, P2P over SIP), and combining the condition of the current WTDS, this paper also proposes that using SIP over P2P to realizing the combination of P2P and SIP; and further proposes the operation mechanism of WTDS under the new system architecture. At last, this paper introduces the design and implementation of each module of WTDS based on P2P in detail, including the design of JXTA (JXTA contains a series of common protocols used for realizing P2P computing, and proposes a base P2P structure) adapter, resource locating, resource release, registration, calling and other functions. The proposed design was experimented under the environment of P2P, and the experiment result proves that the proposed modification method on the current WTDS could solve the single point of failure, performance bottlenecks which probably exist in the current WTDS.