Robust Active Queue Management using a Quantitative Feedback Theory Based Loop-Shaping Framework

In this paper an alternative robust control design based on Quantitative Feedback Theory (QFT) is presented for Active Queue Management (AQM) routers supporting Transmission Control Protocol (TCP) flows. At first, it is shown how the problem can be presented in the QFT loop-shaping framework and then the robustness requirements are formulated based on the nature of the system. A sufficient condition for obtaining a satisfactory level of robust performance against high-frequency parasitics is introduced. Experimental results using the ns simulator are provided to illustrate the effectiveness of the proposed method.