Residual-Energy-Activated Cooperative Transmission (REACT) to Avoid the Energy Hole

In a multi-hop wireless sensor network (WSN) with a constant node density, the nodes that are one hop away from the Sink die first and cause an “energy hole,” because they must forward the traffic from the rest of the network. When this hole forms, a large amount of “excess” energy is trapped in the other nodes. In this paper, we propose that some of those other nodes use some of the excess energy to do cooperative transmission (CT) to hop directly to the Sink, thereby relieving the nodes near the sink of some of their burden and balancing the energy consumption across the network. The REACT protocol triggers CT range extension when the next-hop node along a primary route has a lower residual energy than the current node. The paper considers several criteria for selecting the cooperators, and compares our proposed scheme to the AODV and CMAX multi-hop protocols through simulation.