Hybrid polling and contention access scheduling in IEEE 802.11e WLANs

Supporting real time applications over local area wireless access networks requires features and mechanisms that are not present in the original IEEE 802.11 standard for WLANs. Therefore, several quality of service (QoS) enabling mechanisms have been added to the MAC layer in the new IEEE 802.11e standard. However, the standard does not mandate a specific QoS solution and intentionally leaves it to developers and equipment vendors to devise such schemes. We present a solution that employs the controlled access mechanisms of the 802.11e to provide per-session guaranteed QoS to multimedia sessions. We introduce a framework that centralizes the task of scheduling uplink and downlink flows in the access point through the new concept of virtual packets. We propose a fair generalized processor sharing based scheduler, integrated with a traffic shaper, for scheduling controlled (polling) and contention access durations. Through analysis and experiments we demonstrate that our solution provides guaranteed fair access for multimedia sessions over WLANs.