Algorithm 3. P-CH and S-CH Selection Algorithm (Large Cluster of Stable Period)

Inputs: (1) nodes of cluster C

(2) size of cluster C: NO

(3) location of BS: (BS·x, BS·y)

Result: P-CH and S-CH of cluster C

1: calculate cluster center position Cen (XC,YC);

2: for i = 1 → NO

3:   calculate the objective function of node I, GiCH;

4: end for

5: select two nodes with GCHmax and GCHsecond-max as the P-CH and S-CH of cluster C, respectively;