Stabilizing first-order controllers For TCP/AQM networks

In this paper, we investigate the overload problem of a congested router in TCP networks, with a design of an AQM (Active Queue Management) controller based on control theory. The model of TCP/AQM is converted into a second-order system with time delay, the stability of the closed-loop AQM system is described in terms of a characteristic quasi-polynomial. We focus on the synthesis of first-order AQM controller. Our approach consists of determining the stabilizing regions in the parameter space of the first-order controller, then choosing controller´s parameters within these regions. Finally, we illustrate the proposed methodology with an example and simulations using NS-2 simulator.