PI-PD-controller for robust and adaptive queue management for supporting TCP congestion control

We propose the proportional-integral (PI)-proportional-derivative (PD) controller mechanism, which can provide robust and predictive congestion avoidance and control using an adaptive congestion indicator and a control function. PI-PD controller is designed by approximating the PID feedback control to take advantages of excellent capabilities of a PID feedback control mechanism in predicting and controlling future error as well as eliminating the steady-state error. With PI-PD controller, fast response and proactive control to the changing traffic load can be achieved by PD control and satisfactory steady-state control performance can be achieved by PI control. The PI-PD controller stabilizes the queue length around a desired level while giving smooth and low packet loss rates independent of the traffic load level under a wide range of traffic environments. The PAQM outperforms other AQM algorithms such as Random Early Detection (RED) (1993) and PI-controller (2001).