In this work, performance evaluation of LEACH

and LEACH-C protocols based on NS2 is depicted, which

helps to reveal the regularity how performances of these

two routing protocols change with the sink locations. For a

more accurate descr iption of this regularity, two novel

concepts are proposed, i.e., Sensor Node Distribution

Gravity and Distance Metric between sink and Gravity.

Simulation results show that a distance threshold area,

which is a key factor for choosing between LEACH and

LEACH-C protocols, can be achieved.