In this paper, we study the behavior of Voice over IP (VoIP) traffic over IEEE 802.11 wireless networks. Specifically, we propose a QoS provisioning mechanism for VoIP traffic, and suggest a practical solution to configuring the 802.11 e Enhanced Distributed Control Access (EDCA) parameter sets for different types of traffic. With our mechanism, the EDCA parameter sets can be easily configured via software interface in off-theshelf WiFi phone products and it is not required to modify the operations of Access Points or 802.11 M\AC layer protocols. The performance of our mechanism is evaluated via ns-2 simulations and via laboratory experiments over Quanta's 02 dual-mode handsets. The results show our mechanism can provide effective and efficient QoS provisioning for VoIP traffic over IEEE 802.11 WLANs.

In this paper, we propose a new differentiated service model, referred to as Differentiated Service-EDCA (DS-EDCA), for the Enhanced Distributed Channel Access (EDCA) of IEEE 802.11e wireless local area networks (WLANs). With DS-EDCA, both strict priority and weighted fair service can be provided. The strict priority service is provided for high priority traffic through carefully setting the EDCA parameter sets of lower priority traffic; the proportional fairness service is enabled by determining the backoff intervals according to the distributed scheduling discipline (DFS). We also propose a hierarchical link sharing model for IEEE 802.11e WLANs, in which AP and mobile stations are allocated different amounts of link resource. The performance of DS-EDCA and EDCA is compared via ns-2 simulations. The results show that DS-EDCA outperforms the original EDCA in terms of its support for both strict priority and weighted fair service. More importantly, DS-EDCA can be easily implemented, and is compatible to the IEEE 802.11 Standard.

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