VoIP Over MANETS: A Performance Analysis of OLSR

Using Voice over Internet Protocol (VoIP) in Mobile Ad hoc Networks (MANETs) takes advantage of the mobility and versatility of a MANET environment and the flexibility and interoperability a digital voice format affords. Current issues with this combination of technologies include routing traffic in the MANET. Previous research has shown that VoIP-like traffic is capable of being routed through an ad hoc network using the Ad hoc On-demand Distance Vector (AODV) routing protocol (a reactive routing protocol). However, the Optimized Link State Routing (OLSR) protocol is a proactive routing protocol also used in MANETs that may also be suitable. This research determines the suitability of OLSR as a routing protocol for MANETs running VoIP applications. Representative VoIP traffic is submitted to a MANET and the metrics of end-to-end delay and packet loss are observed. The factors of node density, number of data streams and mobility are varied creating a full-factorial experimental design of 18 distinct scenarios. OPNET modeler simulates the MANET, and VoIP traffic is introduced using one source node that sends traffic to random destinations throughout the network. Results show that node density, number of data streams and mobility most affect delay and packet loss. As the number of data streams increase, both delay and packet loss also increases. Increase in the number of nodes in the simulation area (1,000 m by 1,000 m) decrease delay, showing that packet loss is affected by the number of nodes in the MANET. Delay is between 0.069 ms to 0.717 ms which is significantly lower than the recommended 150 ms threshold for VoIP applications. Packet loss is between 0.32% and 9.97%, which is less than the 10% allowable packet loss for acceptable VoIP quality. These results show that OLSR is a suitable routing protocol for MANETs running VoIP applications.