A mechanism for cooperative routing and medium access to reduce energy consumption for multi-hop transmissions in sensor networks is presented. By having the network layer provide hints to the MAC layer on the regions in which to pick a next forwarding node and leaving it to the MAC to make the decision based on channel conditions, substantial energy savings and an increase in reliability can be obtained. Using both analytical modeling and simulation, we demonstrate the savings and also outline optimal operation points. We also consider the problem of reduced packet delivery in the presence of node location uncertainty and demonstrate that the presented techniques to mitigate its effect have an even broader application to the general geographic routing problem when node positions are erroneous.

This work was done as part of the PicoRadio project at the Berkeley Wireless Research Center and has contributions from the members of the protocols team of PicoRadio.