Design and Implementation of Adaptive Wavelet Network PID Controller for AQM in the TCP Network


Abstract – Internet represents a shared resource wherein users contend for the finitenetwork bandwidth. Contention among independent user demands can result incongestion, which, in turn, leads to long queuing delays, packet losses or both.Congestion control regulates the rate at which traffic sources inject packets into anetwork to ensure high bandwidth utilization while avoiding network congestion. In thecurrent Internet, there are two mechanisms which deal with congestion; the end-to-endmechanism which is achieved by the Transmission Control Protocol (TCP) and theintermediate nodes algorithms such as Active Queue Management (AQM) in routers.In this paper, a combined model of TCP and AQM (TCP/AQM) is formulated andfirst simulated without a controller. The results show that it is unable to track the desiredqueue size. So, to get better tracking performance, an adaptive PID controller based onwavelet network (AWNPID) is used as AQM in the router queue. The non-adaptive PIDcontroller is also demonstrated, and its weakness to the network dynamic changes iscompared to the robustness of adaptive controller (AWNPID). The analytical results forlinearized TCP/AQM model are presented in MATLAB version 7.0.