A Comprehensive Comparison of Routing Protocols for Large-Scale Wireless MANETs

Efficient routing protocols can provide significant benefits to mobile ad hoc networks, in terms of both performance and reliability. Many routing protocols for such networks have been proposed so far. Amongst the most popular ones are dynamic source routing (DSR), ad hoc on-demand distance vector (AODV), temporally-ordered routing algorithm (TORA) and location-aided routing (LAR). Despite the popularity of those protocols, research efforts have not focused in evaluating their performance when applied to large-scale wireless networks. Such networks are comprised of hundreds of nodes, connected via long routes. This greatly affects the network efficiency, since it necessitates frequent exchange of routing information. In this paper we present our observations regarding the behavior of the above protocols, in large-scale mobile ad hoc networks (MANETs). We consider wireless mobile terminals spread over a large geographical area, and we perform extensive simulations, using the QualNet and NS-2 simulators. The results of the simulations yield some interesting conclusions: AODV suffers in terms of packet delivery fraction (PDF) but scales very well in terms of end-to-end delay. DSR on the other hand scales well in terms of packet delivery fraction but suffers an important increase of end-to-end delay, as compared to its performance achieved in small-scale topologies. Also, the effect of maximum connections is severe on TORA, which seems unable to route large amounts of traffic. LAR, seems to scale very well, in terms of all metrics employed