The Simulation Of QoS And Performance Of Communication Network For Traction Power SCADA System

With the rapid development of network communication technology, the communication network for Traction Power SCADA system has developed from the traditional low speed and analog communication system to the digital system, especially phases in the high speed and broad band. The Network based on TCP/IP protocol has got extensive applied in Traction Power SCADA system. Studying and analyzing the capability and the quality of service(QoS) in this communication network has been a hotspot in this domain.Firstly, the paper introduces the definition of QoS and the control mechanisms. Secondly, it analyses the end to end control model and control protocols of QoS, including the InterServ model and DiffServ model.The paper studies the congestion control algorithm based on TCP/IP protocol, and discusses how to combine the two congestion control mechanisms.Subsequently, the paper adopts the simulation tool (NS2), which is widely used in nowaday network simulation. The paper also lucubrates the influence factor of the communication network based on TCP/IP protocol for SCADA, such as network scale, transmission bandwidth, data sending period, queue buffer and so on, which affect the SCADA network capability parameters such as delay, the percentage of lost packages and so on, using NS2 to simulate and test the relevant capability parameters.How to guarantee the network's QoS in the condition of increasing network load is discussed in the paper. It can't be limited by increasing the size of buffer, which will increase the network delay. After studying the RED(Random Early Detection) algorithm , the RED algorithm is applied in the SCADA communication network. Compared with the Droptail algorithm in the low-grade network congestion, the capability parameters are evidently straighten up by using the RED algorithm. After studying the DiffServ model, this technology is applied in the SCADA network. By constructing the differentiated service link, the network capability parameters get better than before, the network's QoS is guaranteed.The method of combining the TCP congestion control and IP congestion control is applied in this paper. Using the DiffServ technology, the QoS system can be constructed in the communication network for Traction Power SCADA system. By the simulation testing, it can be found that in the congestion condition, the network capability gets mended obviously, the end to end delay decreases and the percentage of lost packages decreases.