| With the rapid development of network,ensuring quality of service has become a research hot spot.It can save the cost of building real-time networks and unify management and maintenance easily to combine the Internet and industrial control systems.But it is necessary to solve a lot of problems related to QoS for ensuring real-time response time in such a network.There are many mechanisms for real-time network,such as EPA proposed by our country scholars.It is a carefully designed program which implements strict clock synchronization for each micro-segment in the local field layer.But some of the performances of control networks based on bus architecture need to be studied.This paper conducts major research for real-time network scheduling strategy based on real-time switching architecture.Firstly,the article provides an overview of the situations in real-time network and analyses the special real-time requirements of such networks.Then this paper introduces two major classes of real-time network model and analyses the advantages and disadvantages.Then it uses a new type of real-time performance analysis tool - network calculus to analyse and research real-time characteristics.A formula is also studied in depth that can calculate the maximal data delay.Further,this paper extends a real-time network scheduling strategy,the priority matrix in order to reduce the real-time data transmission delay.It carefully analyses its implementation of the strategy in the switching equipment.Secondly,on this basis,the paper proposes a new network scheduling strategy - the new algorithm combined by real-time priorities and short job first scheduling,referred to as prio_short.The strategy can guarante a lower time delay for real-time data frames.And this is verified in the network model.Finally,this paper builds simulation models and configures parameters for the two kinds of network scheduling strategy in OPNET Modeler 10.0 platform.Then,the studies above are verified by the simulation. |
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