The More Relay Nodes, the More Energy Efficient?

Existing work has been focused on minimizing the number of relay nodes to maintain the connectivity of a sensor network. However, we believe replacing batteries for nodes or redeploying the network is either labor-intensive or impossible, so it is more desirable to reduce energy consumption even if we need to use slightly more nodes. The question we are trying to answer is: is it possible to greatly reduce energy consumption by increasing the number of relay nodes? To properly answer this question, we first designed an algorithm that finds the most energy efficient relay nodes placement for a given number of relay nodes. By observing the energy saving with different numbers of available relay nodes, we found that slightly increasing the number of relay nodes can significantly reduce energy consumption. On the contrary, blindly adding relay nodes does not necessarily improve energy efficiency when the number of relay nodes exceeds a certain threshold.