| TCP congestion control mechanisms, while necessary and powerful, are not sufficient to provide good services in all circumstances, especially with rapid growth in size and the strong requirement for QoS guarantee. It is needed to complement the end system congestion avoidance mechanisms. Active Queue Management, as one class of packet dropping/marking mechanism in the router queue, has been recently proposed to support the end-to-end congestion control in the Internet. The goals of AQM are to reduce the average length of queue in routers and thereby decrease the end-to-end delay experienced by packets, and ensure efficient use of network resources by reducing the packet loss caused by queue overflow. AQM highlights the trade-off between the delay and throughput.The main research works and conclusions are as follows:Based on the theory of controlling network congestion, the control mechanism of active queue management algorithm has become the main stream in the current network congestion control strategy research. AQM controller design goals are summarized on the basis of TCP/IP network dynamic model and comparatived the existing AQM algorithms, the advantages AQM algorithm is designed from the Angle of robust performance enhancement system.so the AQM algorithm based on sliding mode control is presented. Through simulation analysis and comparison,it is confirmed the design of control system robust performance. Based on sliding mode controller with chattering problem,with the system delay, parameter variations and unknown parameters, The paper is put forward the two improved methods, the adaptive fuzzy sliding mode control and continuous sliding mode control, from the two aspects of the performance to response of the system speed and improve the system of tracking. Through the model building, stability analysis and simulation experiment and analysis methods, the two improved methods are proved to have feasibility and efficiency. |
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