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This paper examines two specific aspects of resource management in Wireless Local Area Networks (WLANs)-Call Admission Control (CAC) and handling of Link Adaptation (LA) events. A self-consistent system to manage these for Voice over Internet Protocol (VoIP) over an IEEE 802.11 WLAN is presented. The proposed CAC scheme is based on the Endpoint Admission Control (EAC) paradigm, where the endpoints probe the network to determine if the call can be supported with acceptable Quality of Service (QoS). The proposed scheme was evaluated on an experimental testbed and test results show that correct admission decisions were made under various network configurations. The scheme also determines if LA has resulted in the system becoming congested and, if so, the voice codec of the handset which has undergone LA is adapted so as to restore the system to its earlier state, thereby alleviating the congestion. The proposed scheme was evaluated on the experimental testbed and test results show that the codec adaptation scheme was very effective at overcoming the effects of LA for VoIP over WLAN.
Date of Publication: May 2011