Robust active queue management design: A loop-shaping approach

In this paper, a novel systematic design procedure is presented for robust active queue management (AQM). The congestion control law is obtained through an interactive loop-shaping process that manipulates the system frequency response to meet robust stability and performance requirements in the presence of uncertain network conditions. A sufficient condition leading to a satisfactory level of robust performance against high-frequency parasitics that naturally affect the desired requirements is then derived. A feature of the technique is that the uncertain phase information and round-trip time-delay that are inherent to the system dynamics are fully addressed in the design equations, resulting in minimal conservatism and/or over-design. Simulation results using the ns2 simulator are provided to illustrate the effectiveness of the proposed method.