Random Adaptive MAC Parameters For Achieving Intra-Access Category Differentiation In IEEE802.11E WLAN

The increase in popularity for multimedia applications technologies has sparked an increase in demand for data networks to support these applications. Multimedia applications have specific Quality of Service (QoS) requirements that should be met. The widely accepted IEEE802.11 MAC protocol does not have sufficient provision to support the QoS requirements of multimedia traffic. For this reason, the IEEE Standard committee has proposed a new supplementary standard; IEEE802.11E that includes QoS provisioning. The IEEE802.11E standard aims to meet the QoS requirements by providing prioritized differentiation of traffic. Prioritization is achieved by assigning different traffic to different priority access categories (AC), where by each AC is assigned its own set of static Medium Access parameters, mainly Contention window, Arbitrary inter-frame spacing and transmission opportunity. The same priority AC always has the same set of parameters in all stations. For this reason, as the number of stations increases, so does the probability of two ACs on different stations choosing the same values thus resulting in collisions. This thesis proposes a scheme which uses random adaptive MAC differentiation parameters instead of the static ones used in the 802.11e standard. In particular the scheme uses random offset values based on the Contention window size as well as on Arbitrary Inter Frame Spacing. The proposed scheme also provides intra-AC differentiation which leads to reduced collisions and higher throughput. The performance of the proposed scheme was evaluated through simulations. The results obtained indicated that the proposed scheme outperforms the IEEE802.11E's Enhanced Distributed Coordination Access (EDCA) to which it was compared to when throughput and delay measured.