A ST-PI-PP controller for AQM router

This paper revisits the simple pole placement technique in the classical control theory, and exploits this technique to propose a controller for the active queue management (AQM) in IP routers. Our self-tuning proportional-plus-integral controller based on pole placement (ST-PI-PP controller) can assign proper intervals of the damping ratio ξ and the undamped natural frequency ω_n to guarantee the system stability, to achieve good AQM performance and thereby to make the system adapt to significant load changes very well. We verify the effectiveness of the controller via OPNET simulation. Our simulation results show that: a) choosing appropriate ξ and ω_n can successfully satisfy the transient response of the system; and b) when the network load changes, the ST-PI-PP controller can still stabilize the queue size at the reference value.