Design of a robust digital controller for congestion control in Internet

This paper is concerned with the design of a robust AQM control scheme for congestion control in Internet. The design of efficient control schemes is challenging since the TCP congestion window model presents both time-varying time delay, appearing in the state and the control signal, and model uncertainties, due to variations of network characteristic parameters. Hence, our paper begins firstly by giving sufficient conditions for stability and stabilizability for the class of systems whose dynamic is similar to the TCP congestion window one, in term of LMI. After, the general results obtained are applied to congestion control, resulting in a new AQM which is implemented in NS2 and compared to other ones in the literature, as PI and REM. The simulations emphasized the effectiveness of our AQM and its improvements with respect to the other control schemes.