Impact of caching and MAC overheads on routing performance in ad hoc networks

We consider an on-demand routing protocol for mobile ad hoc networks that uses route caching aggressively. We show that stale routes in the caches and medium access control (MAC) overhead for replies from caches can degrade performance significantly, so much so that relative performance is much better without using replies from cache. We analyze these problems in a series of evaluation steps, usually looking at both routing and MAC layer performances together. We suggest several mechanisms to address the stale cache problem and also suggest a change in the MAC layer interface to reduce the MAC overhead. The combination of these techniques improves the relative performance of cached replies. Apart from improving performance of the routing protocol, this work serves as a case study where an analysis spanning multiple layers was necessary to identify the performance bottlenecks in a wireless network.