Application Of Model Free Adaptive Control In Network Congestion

The network congestion cannot be avoided because of the network's nature and the increasing applications, neither increasing network resources nor decreasing applications is sufficient to guarantee the stability of the network behaviors and, after all, they are not active ways. So an effective congestion avoidance mechanism is the only way to prevent the congestion collapse from a relative light congestion.The mechanisms of congestion control can be classified into many groups based on different rules. The algorithm of active queue management (AQM) that is applied in the inter node of the network is an active close-loop link algorithm to control congestion. This algorithm generates indicating congestion information in the link node of the network and transmits it to the end system, which is used by the end system to adjust the input rate to alleviate the network congestion.In this thesis, the advantages and disadvantages of the current prevalent congestion control algorithms are discussed in detail. Based on some general AQM algorithms such as RED, ARED,SRED,REM et al, an improved congestion control scheme is proposed,The Model Free Adaptive Control (MFAC) ,MFAC strategy only needs input and output information of the system to work and a online-tuning parameter, and MFAC has a strong adaptability in time-varying environment.In this thesis, the MFAC method has been used in the congestion control of the active queue management, and the comparison study among PID and MFAC has shown that, compared to PID, MFAC can not only speed up the queue convergence, but also be able to make the queue stabilized more quickly almost without overshoot. Therefore model free adaptive control have a better adaptability in AQM。...