Synthesis of robust active queue management controllers

This paper is concerned with the derivation of improved AQM control schemes to cope with unwanted variations of characteristic parameters such as the the average round-trip time, the load and the link capacity. To achieve this aim, we use novel robust control strategies for time-delay systems, which are based on the use of robust reduction methods and H$^{\infty}$ strategies resulting in \emph{memory} and \emph{memoryless} control laws respectively. To avoid the need for full state availability, difficult to satisfy in realistic network applications, the control strategy is complemented by a robust observer for time delay system. The control laws presented in the paper are validated and tested on different network scenarios through numerical simulations in both Matlab/Simulink and Network Simulator-2.