The performance study of contention-based differentiation mechanisms in IEEE 802.11e MAC layer

IN the 802.11e MAC, the new contention-based access scheme called enhanced distributed coordination function (EDCF) is an enhancement of the 802.11 DCF for service differentiation. The backoff process of the EDCF access scheme is governed by a set of contention parameters defined in the 802.11e. The EDCF contention parameters may have different values for different ACs (access categories), thus making service differentiation in the backoff mechanism. An arbitration inter-frame space (AIFS) is used for the minimum specified idle duration for the EDCF access during the CP (contention period). For the computation of the contention window (CW), each AC has its own set of CWmin, CWmax, and the CWPFactor (contention window persistence factor). The differentiation effectiveness of the EDCF access scheme becomes a multidimensional parameter-setting problem. This paper aims at investigating rite performance of the EDCF contention-based differentiation mechanisms via simulations. All the parameters mentioned above are considered in the simulation model. The performance indexes of our simulation study are overall channel utilization during the CP and the total EDCF TXOPs (transmission opportunities) gained by individual ACs.