MAC-Layer QoS Evaluation Metrics for IEEE 802.11e-EDCF Protocol over Nodes' Mobility Constraints


Although wireless networks suffer from limit bandwidth, higher bit-error rates (BER’s), significant amount of delay, and lower security than wired networks, still they have been emerged as an existing technology for the broadband wireless access, like IEEE 802.11 WLAN. Being fair for sharing medium resources considers the main reason for these weaknesses. Furthermore, Quality of Service (QoS) mechanism, in the recent version of the standard, should improve service differentiation among various types of traffic. It challenged to manage collisions and to support channel variation. Beside, wireless networks are more likely to have higher-ranking on flexibility by allowing easy setting up. If the IEEE 802.11 standard family provides the guarantee for connectivity, sufficient local coverage, required security and enough compatibility with the existing technologies, it is highly expected to carry on real-time applications requirements (Andreadis, 2006). Particularly, the EDCF MAC protocol, which improved a set of parameters, defines the classes of priority for the channel access mechanism during the contention-based period (CP). This can subsequently be declined to a variation of network dynamicity. In fact, when a mobile node crosses the overlay area with other connected nodes, the data transfer can be affected during the handoff intervals. The MAC process fails synchronization and it will be considerably corrupted by generating an amount of packets loss. This effect can be highly intensive depending on the increase of node’s mobility rate. Consequently, EDCF protocol loses capacity for QoS delivery and can be reverts to a DCF behaviour reached the threshold limit of stability. Reliability analysis of different traffic classes (video, voice and data), without considering both network topology and node’s mobility constraint, is not well appropriated. Dealing with this recent constraint, we propose a study which allows to know how EDCF react facing nodes mobility referring to the MAC protocol stability region. The functional analysis allowed us to follow the mobility of the node and identify the high-rated packets loss areas. To reduce this impact, we specify an algorithm, which operates in different network topology, called multi-coverage algorithm for approving the medium access mechanism. This approach can support overlapping adjacent coverage wireless ranges. For performance evaluation, we studied the most common measured metrics: effective

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@inproceedings{Dridi2012MACLayerQE, title={MAC-Layer QoS Evaluation Metrics for IEEE 802.11e-EDCF Protocol over Nodes' Mobility Constraints}, author={Khaled Dridi and Boubaker Daachi and Karim Djouani}, year={2012} }