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The proliferation of multimedia applications requiring strict QoS requirements have tested the performance of the widely used IEEE 802.11 MAC layer protocol for its ability to provide proper service differentiation and QoS. The IEEE 802.11e MAC layer protocol was put forward as an improvement to the IEEE 802.11 MAC layer protocol, focusing on service differentiation and QoS. The nature of IEEE 802.11e is such that in the presence of intensified high priority network traffic, the low priority traffic starves. In this thesis work possible causes for starvation of low priority traffic and the use of dynamic MAC layer parameters in removing starvation of low priority traffic and at the same time providing proper service differentiation and QoS for higher priority traffic in par with IEEE 802.11e EDCF are presented. Two novel schemes are presented which use dynamic MAC parameters. The proposed schemes change the inter frame spacing and contention window parameters based on the calculated collision probability and the fraction of transmission opportunities taken by each traffic class. The proposed schemes are evaluated under static (single hop and multi-hop) and mobile network (multi-hop) conditions. The issues that arise in a multi-hop network and the impact of mobility on the proposed schemes are discussed. |
