Investigating Manet Performance in a VOIP Context

In the last few years, we saw the emergence of voice-over-IP (VoIP) protocols to enable low-cost telephony services. While VoIP providers are rapidly growing market share against public switched telephone network (PSTN), these technologies are lacking mobile support. We believe that mobile ad hoc networks (MANETs) may offer a good platform for the fast deployment of VoIP mobile networks. However, efforts must be made to improve performance of MANETs before they can be used for this purpose. This paper presents at first the most important metrics needed to evaluate the relative performance of MANET routing protocols in a VoIP scenario. We show that the most important metrics influenced by the routing protocols are the frequency of route loss and their duration. With the help of those metrics, we detail the performance analysis of AODV, a common reactive ad hoc protocol. Our results show that node mobility and node density have a limited influence on the performance of the protocol. However, the route length and the network load seem to be the critical factors deteriorating the performance of the routing protocol. We conclude that MAC layer misbehavior (802.11) is responsible of a majority of false route loss detections. We finally suggest solutions in order to reduce MAC layer misbehavior and to improve future MANET routing protocols for mobility support of VoIP