A Practical QoS Solution to Voice over IP in IEEE 802.11 WLANs

In this article we study the behavior of voice over IP traffic in IEEE 802.11 wireless networks. Specifically, we design a QoS provisioning mechanism for VoIP traffic, and propose a practical solution of configuring the 802.11e enhanced distributed control access parameter sets for different types of traffic. We show that media access control layer only methods may be insufficient, but the demonstrated cross-layer (layers 2, 3, and 4) method works simply and efficiently. We find that the EDCA parameter sets of the access point are not always necessarily set more aggressively than those of wireless stations even though the traffic load of AP is much heavier than the stations. With our mechanism, the EDCA parameter sets can be easily configured via software interface for off-the-shelf WiFi phone products, and there is no need to modify the operations of APs or 802.11 MAC 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 in IEEE 802.11 WLANs. Since the configuration may be readily configured in the field and the performance is robust across a wide range of environments, we believe that organizations deploying and operating WiFi networks for VoIP may benefit from our work and reduce or eliminate post-deployment tuning and debugging.