ChaPLeT: Channel-dependent Packet Level Tuning for Service Differentiation in IEEE 802.11e

With the increased use of IEEE 802.11b wireless networks, there is a strong need to support diverse Quality of Service (QoS) requirements. Recent standardization efforts are being pursued in IEEE 802.11e to introduce a framework for QoS enhancements to the IEEE 802.11b standard. Although IEEE 802.11e provides a level of service differentiation by statically associating different QoS parameters for pre-defined traffic classes, this upcoming standard does not consider the problems introduced by varying channel conditions present in wireless networks. In this paper, we present a Channel-dependent Packet Level Tuning (ChaPLeT) mechanism to maintain service differentiation in the presence of channel variation. We propose the use of three parameters, namely fragmentation threshold, persistence factor, and defer countdown in enabling packet-level prioritization. Using a runtime adaptation policy, ChaPLeT dynamically configures the above parameters appropriately based on traffic class, as well as current channel conditions. We show the effectiveness of our approach by comparing our adaptation policy with the current IEEE 802.11e scheme.