Assured and expedited forwarding extensions for IEEE 802.11 wireless LAN

We propose DIME (DiffServ MAC extension), an extension of the IEEE 802.11 MAC protocol to support differentiated services. The proposed extension consists of two optional modules: expedited forwarding (EF) and assured forwarding (AF). The expedited forwarding extension (DIME-EF) reuses the interframe space of the point coordination function (PCF) of the IEEE 802.11 standard in a distributed manner, while the assured forwarding extension (DIME-AF) relies on the distributed coordination function (DCF) with a modified algorithm for the computation of the contention window (CW). Best effort is supported by the functionality of the current 802.11 standard in such a way that legacy IEEE 802.11 terminals behave as best effort terminals in the DIME architecture. While the performance of the assured forwarding extension has been thoroughly evaluated by the authors elsewhere (see Banchs, A. and Perez, X., Proc. IEEE Wireless Commun. and Networking Conf., 2002), this paper concentrates on the overall architecture and the performance of the expedited forwarding extension.