This paper proposes a Duty-Cycle (DC) control method in order to improve the Packet Delivery Ratio (PDR) for IEEE 802. 15. 4-compliant heterogeneous Wireless Sensor Networks (WSNs). https://www.roneverhart.com/2-1-2-x-1-4-x-36-Smooth-Saddle-Threshold-NGP-410-36/