(a) Nodes’ Residual Energy
(b) CKN Active Neighbors
Figure 1: Nonuniform energy consumption problem. In (a), the black nodes represent the nodes which have more residual energy than those of node , the grey and white nodes have less energy than ’s, and the white node has the least energy. In (b), the green nodes represent the active nodes according to the CKN algorithm in a WSN, and the sensor nodes with less residual energy are selected.