Integral sliding-mode robust observer-based congestion control for wireless access networks

Abstract

Designing a robust active queue management (RAQM) is mandatory to avoid congestion in networks with wireless access links, because transmission control protocol (TCP) can detect congestion after its occurrence in a communication network and wireless links suffer from bottleneck capacity variations caused by fading and packet error rate (PER) in the acknowledgement packets. Furthermore, the average window size cannot be measured explicitly from the output signal and input and state delay are imposed to a network, which complicate the RAQM design problem in nonlinear models. So, the main contribution of this study is to design a robust observer based control procedure based on integral sliding mode protocol to estimate the average window size, to control congestion in a TCP/RAQM network and to compensate input and state delay. Simulation results via professional simulator NS-2 and SIMULINK confirm that the procedure can effectively estimate the window size and can robustly avoid congestion.