Experimental Investigation on VoIP Performance and the Resource Utilization in 802.11b WLANs

In a shared medium network like the 802.11b WLAN, predicting the quality of VoIP calls from the resource usage of the wireless medium is highly desirable. Analyzing the bandwidth usage at the L2/MAC layer may be especially useful for potential QoS provisioning and call admission schemes. This paper experimentally investigates the relationship between resource utilization in WLANS and the quality of VoIP calls transmitted over wireless medium. Specifically we evaluate how the amount of free bandwidth influences transmission impairments (i.e. delay, loss and jitter) and thus call quality. Resource utilization (under the MAC bandwidth components framework) is calculated by a WLAN resource monitoring application that passively “sniffs” packets at the L2/MAC layer and analyses their headers and temporal characteristics. The quality of VoIP calls is predicted using an extended version of the ITU-T E-model, which estimates user satisfaction from time varying transmission impairments