Stability Analysis of PI TCP/AQM Networks: A Parameter Space Approach

This work focuses on deriving the necessary and sufficient stability condition of transmission control protocol (TCP) network with a proportional-integral (PI) active queue management (AQM) scheme via a parameter space approach. First, a fluid-flow TCP s nonlinear model is converted into a linear time-delay system of neutral type. Second, the stability of the closed-loop system is characterized in terms of the network's and the controller s parameters. By simulation studies we investigate the boundary s relations of these two kinds of parameters in the parameter space and illustrate how PI controller s parameters affect the stability. Finally, different stability conditions are compared to show the less conservatism of our necessary- and sufficient-condition-based method, and simulation experiments by both Matlab and NS-2 are conducted to prove our claim.