Nonlinear PI active queue management based on hyperbolic secant functions

This paper proposed a novel nonlinear proportional integral (N-PI) active queue management (AQM) scheme to enhance the performance of the original PI algorithm. It uses nonlinear hyperbolic secant functions to tune the proportional and integral coefficients online. Based on previous research, the mathematic flow model with a nonlinear PI controller is proved to be absolutely stable under certain conditions using the Popov stability theorem. The effectiveness of the nonlinear PI controller is validated via comprehensive simulations. Our simulation results manifest that N-PI algorithm can not only stabilize the instantaneous queue size around the predefined value very quickly, but can also adapt to changes of the network environment and outperform the original PI gateway with hybrid UDP background traffic. High throughput is also achieved against the number of active connections, which shows satisfactory performance robustness of the N-PI algorithm.