Optimizations for route discovery in asynchronous duty-cycling wireless networks

The use of asynchronous duty cycling at the MAC layer affords substantial energy savings in wireless networks. This technique is widely used in sensor networks and other types of wireless networks such as ad hoc networks. With asynchronous duty cycling, each node switches alternately between sleeping and active states; each node waking up asynchronously reduces network contention and wireless collisions caused by nodes waking up simultaneously, but also can have undesirable effects on higher layer protocols. In this paper, we study the problem of on-demand route discovery in asynchronous duty-cycling wireless networks and present four optimizations for such route discovery: Delayed Selection, Duty-Cycled Selection, Reply Updating, and Adaptive Backoff. Through detailed ns-2 simulations, we show that, without these optimizations, the routes discovered in asynchronous duty-cycling networks can be over 50% longer than the theoretical shortest routes and can have an ETX 90% larger than the ETX of the optimal routes. With only simple changes made at the MAC or network layers, our optimizations enabled nodes to substantially improve discovered routes, finding routes that were only 0.2% longer than the theoretical shortest routes or routes with an ETX only 9% larger than the ETX of the theoretical optimal-ETX routes, while also reducing route discovery latency and node energy consumption.