Research And Design Of Distributed System Communication Protocol

SCADA system has been widely applied to many fields, such as oil,pipe,natural gas,hydrological monitor and municipal infrastructure. Designing a simple, efficient and reliable communication protocol is necessary, which is aimed at the peculiarities of remote,medium or low speed,small batch and approximate real-time data transmission in these fields. The first part of the paper simply introduces the concept of SCADA system,the software and hardware configurations of RTU ,today prevalent communication protocols and the comparisons among them. The status and trend of development of SCADA system at home and abroad are also presented.In the second part , the design rules of the communication protocol and the reference models of network architecture are simply showed ;The design requests of the physical layer,data link layer,pseudo-transport layer and application layer are also studied in the thesis. The hardware development platform—BL2000 and the software development platform—dynamic C and μC/OS-Ⅱ(Real-Time multitask Operating System ) are introduced in this part too.The design idea and realization of the physical layer,data link layer,pseudo-transport layer and application layer in the protocol are discussed in detail in the third part of the paper, including frame format,data link manage,application message format,message transaction flow and the combination and decomposition of larger message. The design and realization of the difficulties in the protocol are researched deeply, such as message transmission collision in the data link layer and application layer,time synchronization,store and forward.The end of the paper discusses the test of the communication protocol, simply introduces the content and method of the test, analyzes the result of the test and achieves the conclusion of the test.Through researching into the architecture,design and developing trend of the SCADA system and the communication protocols, the paper designs a communication protocol of SCADA system, which is suitable for remote,medium or low speed,small batch and approximate real-time data transmission. The designed protocol is practically proved to be a reliable,flexible,widely used communication protocol.