Quality of VoIP Traffic Over Multi-Hop Wireless LAN Networks

N. Afifi and C.C.Y. Jie (Malaysia)


Wireless, Multimedia, Voip, WLAN networks


In this paper, we investigate the capability of the pervasive IEEE802.11 network to support VoIP applications to form a wireless multihop backhaul voice network for rural areas. This is to follow the recommendation of the International Telecommunication Union (ITU) to deploy a low cost wireless voice network infrastructure for rural areas based on WLAN and VoIP. To implement such a system, the quality of VoIP traffic over WLAN needs to be evaluated and the capacity determined. Our aim is to investigate parameters that will increase the capacity and improve the quality of the VoIP traffic and to determine the number of users who can be sustained over such networks. The performance of IEEE802.11 wireless network in terms of capacity is evaluated, where the capacity for voice traffic is defined as the maximum number of simultaneous, bidirectional calls that can be supported, subject to a minimum voice quality requirement. Our measurements show that the capacity of such networks can be increased in different ways. First, the capacity over multi-hop can be increased significantly without any drawbacks by increasing the number of radios per node. Increasing the number of radios reduces the channel contention because each hop is served by a dedicated radio link. Not only contention is reduced but also interference is also reduced due to the non-overlapping frequencies used. Greater capacity can also be achieved by increasing VoIP packet length. Increasing the packet length was found to offer higher values of sustained phone calls under ideal channel conditions. The results are then used to calculate the number of users that can be sustained over multi-hop WLAN networks for rural applications.

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