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Designing robust active queue management subjected to network imperfections is a challenging problem. Motivated by this topic, we addressed the problem of controller design for linear systems with variable delay and unsymmetrical constraints by the scaled small gain theorem. We designed two mechanisms: robust enhanced proportional derivative; and robust enhanced proportional derivative subjected to input saturation. Discussion of their practical implementations along with extensive comparisons by MATLAB and NS3 illustrate the improved performance and the enlargement of the domain of attraction regarding some literature results.

In this paper, new local stabilization analysis for TCP/AQM process based on segmented delay is proposed. The new approach consists in describing the time delay as a sum of homogeneous loads delays plus the variation of the queuing delay resulting from the made actions inside the router buffer. By employing an appropriate new Lyapunov–Krasovskii functional that depends on the upper bounds of the loads, new segmented delays dependent local stabilization conditions are proposed. Furthermore, new results concerning the unsymmetrical saturation input are obtained. Finally, the theory is experimented on NS 3, which proves that the proposed Segment Controller (SegCont) mechanism is strong and robust.

This paper presents a simple Linear Matrix Inequality (LMI) condition for the design of stabilizing control for a class of systems whose dynamics is similar to the TCP/AQM process based on the guaranteed cost approach. Furthermore, by analyzing the cost function, an optimization procedure is derived. Then, by solving the problem, according to the optimization procedure, the controller gain guarantees a less bound of the cost function and the asymptotic stability of the system subjected to the uncertainties. Moreover, the simplest implementation procedure to overcome the implementation constraint is proposed. Finally, the engineering relevance of the theory has been evaluated with different realistic scenarios in NS3 and shows that the Guaranteed Cost Controller (GCC) scheme provides the best performance.

This paper deals with the problem of feedback control for Active Queue Management (AQM) system with successive delays. Mathematical models for both single and multi-bottleneck topology of TCP/AQM process are studied. The multiple delays are introduced in Transmission Control Protocol (TCP) models for the first time. An implementation is proposed to improve the buffer management. Sufficient conditions for existence of an admissible controller are established to ensure the asymptotic stabilization of the resulting closed-loop system. Finally, a numerical example is given to illustrate the advantages of the proposed Laxus Feedback Controller (LFC) with respect to some literature results.