Date Added: May 2012
Due to the inefficiency of a flat topology, most Wireless Sensor Networks (WSNs) have a cluster or tree structure; but this causes an imbalance of residual energy between nodes, which gets worse over time as nodes become defunct and replacements are inserted. Multiple layers are better then the typical two-layer cluster-based topology, because it can better accommodate nodes with different levels of residual energy. The authors propose that each node should periodically determine its own layer, as its situation and the network topology changes. They introduce a topology control scheme for long-term WSNs with these features. Simulations show that this scheme can balance node energy levels, and thus extend network lifetime.