Control and optimisation of HCCA 802.11e access scheduling

This paper presents an optimal controller for the scheduling of real time traffic in 802.11e Wireless LANs. The problem is defined as a standard control problem, starting from a discrete event model of the systems composed by the Access Point and and the connected stations and is by Model Predictive Control scheme, for which we provide formal proofs of stability. The results are compared with an existing alternative proposal with lower complexity, which in certain conditions may exhibit limit cycles. The paper is closed with some realistic simulation results obtained with ns-2, which show that the proposed controller performs better than other proposals also in presence of real systems packet quantisation, which is not directly considered in the model.