Two Hops is One too Many in an Energy-Limited Wireless Sensor Network

A common technique in wireless sensor networks (WSN) is to use multihopping, that is, relaying messages via intermediate nodes. In this work we compare the energy efficiency of single-hop and multihop taking into account circuit energy consumption as well as transmission energy. We consider a simple two-hop case as well as a multihop case for a uniform two-dimensional network of arbitrary size. Contrary to common beliefs, we find that single-hop is superior for all realistic cases covered by our model. Even in comparison to the simple two-hop case single-hop is preferable. Only at very large path losses would multihop be a serious alternative. At present there are however very few WSN radios available that can operate under such conditions. In spite of the relatively simple networks considered we argue that our findings have quite general applicability with strong implications for the choice of routing protocols.