Three scheduling-levels algorithm for IEEE 802.11 QoS efficiency improvement.
ABSTRACT This paper focuses on an analysis of the packets scheduling schemes to improve the QoS in IEEE 802.11 WLANs. Based on the Hybrid Coordination Function (HCF) at the MAC layer, a new algorithm structure called HCF-T is proposed. It is centralized in three process units for both packets scheduling and Transmission Opportunities (TXOPs) allocating main tasks. Taking into account the queue length as relevant information, the scheduling strategy tracks the queue's contents and manages the packets enabling TXOPs duration to be well assessed. We investigate the effectiveness of the new mechanism by developing a simulation model. In this regard, the evaluation of performances is carried out in terms of traffic control frames, collisions, and network load. Finally, we discussed some remarks related to cooperative diversity networks and planning the upcoming work.
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ABSTRACT: This paper presents how enhanced Quality of Service (QoS) in IEEE802.11e is achieved by providing traffics with different priorities performing the access to the wireless medium. Particularly, the EDCF set of parameters defines the priorities of the admission control mechanism during the Contention-based Period (CP). This can subsequently be declined to a variation of network dynamicity. Reliability analysis of different traffic classes (video, voice and data), without considering both network topology and node's mobility constraints, is not well appropriate. Being based upon scenarios, our proposed approach reveals how the behaviour of the service differentiation scheme is greatly affected according to the nodes' mobility (position and velocity). Thus, three levels (Low, Medium, and High) of node's speed are discerned. Depending on the Access Aategories (AC's) in QoS Stations (QSAT's), the Wireless LAN has been implemented on various static and dynamic scenarios using NS-2. Performance of EDCF based on the main MAC-layer metrics, such as throughput, End-2-End delay and jitter, is deeply investigated.MoMM'2009 - The 7th International Conference on Advances in Mobile Computing and Multimedia, 14-16 December 2009, Kuala Lumpur, Malaysia; 01/2009
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ABSTRACT: In this paper, we carry-out a study of the Quality of Service (QoS) mechanism in IEEE802.11e Enhanced Distribution Coordination Function (EDCF) and how it is achieved by providing traffics with different priorities. It can perform the access to the radio channel or just simply it can considerably be declined subsequently to a variation of network dynamicity. The results of the proposed analysis show that the EDCF scheduler looses the ability of the traffic differentiation and becomes insensitive to the QoS priority requirements. Consequently, it goes away from the region of stability and EDCF doesn't offer better performance than the conventional DCF scheme. Therefore, traffic specifications are weakly applied only for the channel occupation time distribution. During the handoff between the Base Stations (BS's), the response time of the data rate application within the roaming process grows to the initial throughput level. Performance metrics at the MAC layer, like throughput, End-2-End delay, and packet loss have been evaluated. Comment: 4 Pages
Karim D. Djouani