There are some applications where only a fraction of all the deployed nodes are the data generating nodes, i.e., the members of E while the remaining nodes are the members of set B. While both the set E and B are disjoint and subset of set N. There are some other (regular data gathering) applications in which all nodes are equally responsible for data sensing and forwarding tasks. In such cases the set E is equal to set B and both sets are subset of set N.