Dynamic multipath allocation in Ad Hoc networks

Ad Hoc networks are characterized by fast dynamic changes in the topology of the network. A known technique to improve QoS is to use Multipath routing where packets (voice/video/...) from a source to a destination travel in two or more maximal disjoint paths. We observe that the need to find a set of maximal disjoint paths can be relaxed by finding a set of paths S wherein only bottlenecked links are bypassed. In the proposed model we assume that there is only one edge along a path in S is a bottleneck and show that by selecting random paths in S the probability that bottlenecked edges get bypassed is high. We implemented this idea in the MRA system which is a highly accurate visual ad hoc simulator currently supporting two routing protocols AODV and MRA. We have extended the MRA protocol to use multipath routing by maintaining a set of random routing trees from which random paths can be easily selected. Random paths are allocated/released by threshold rules monitoring the session quality. The experiments show that: 1) session QoS is significantly improve, 2) the fact that many sessions use multiple paths in parallel does not depredate overall performances, 3) the overhead in maintaining multipath in the MRA algorithm is negligible.