SMART: Statistically Multiplexed Adaptive Routing Technique for Ad Hoc Networks

This paper develops a common solution to the problems of discovery, maintenance, and use of multiple routes in ad hoc networks. The performance criterion is the average time taken by a packet to reach its destination through multiple hops. A source node considers each of its neighbors (reachable by direct wireless transmission) as a next-hop for every possible destination. The effect of delay at a next-hop and beyond, until the packet reaches its destination, is approximately modeled as an equivalent M/M/1 queuing system. Available neighbors at every node provide multiple routes. Multiple routes are statistically multiplexed to distribute the load as well as to deal with changes in data rates and network configuration. The potential of each next-hop neighbor of a node in providing a viable route is estimated on-line and the proportions of traffic routed through these multiple neighbors are also updated adaptively. We study this approach and conduct extensive experiments over a network with two extreme cases of simulated traffic patterns, the Poisson, and the self-similar types. Even when the network topology is static, our algorithm responds to bursts in the traffic pattern and reduces buffer losses through the use of alternative, less congested routes. We also present simulation experiments and results to demonstrate the effectiveness of our algorithm in the presence of mobility, using self-similar traffic. Mobility is simulated by means of the random waypoint model in which nodes move with varying speeds. Results show that our simple unified approach handles the problems of mobility as well as network congestion very well.