Discovering long lifetime routes in mobile ad hoc networks

In mobile ad hoc networks, node mobility causes frequent link failures, thus invalidating the routes containing those links. Once a link is detected broken, an alternate route has to be discovered, incurring extra route discovery overhead and packet latency. The traffic is also interrupted at the transport layer, and proper traffic recovery schemes have to be applied. To reduce the frequency of costly route re-discovery procedures and to maintain continuous traffic flow for reliable transport layer protocols, we suggest discovering long lifetime routes (LLR). In this paper, we first propose g-LLR, a global LLR discovery algorithm, that discovers LLRs of different route lengths for any given pair of nodes. We then propose a distributed LLR discovery scheme (d-LLR) that discovers two of the most desirable LLRs through one best-effort route discovery procedure. Simulations show that the lifetimes of the routes discovered by d-LLR are very close to those discovered by g-LLR. Simulations also show that the performance of different transport layer protocols is greatly improved by using LLRs. More importantly, traffic can remain continuous using the provided LLRs. D-LLR can be implemented as an extension to existing ad hoc routing protocols, and it improves the performance of transport layer protocols without modifications on them.