  The sustainable Internet of Things (IoT) is becoming a promising solution for
the green living and smart industries. In this article, we investigate the
practical issues in the radio energy harvesting and data communication systems
through extensive field experiments. A number of important characteristics of
energy harvesting circuits and communication modules have been studied,
including the non-linear energy consumption of the communication system
relative to the transmission power, the wake-up time associated with the
payload, and the varying system power during consecutive packet transmissions.
In order to improve the efficiency of energy harvest and energy utilization, we
propose a new model to accurately describe the energy harvesting process and
the power consumption for sustainable IoT devices. Experiments are performed
using commercial IoT devices and RF energy harvesters to verify the accuracy of
the proposed model. The experiment results show that the new model matches the
performance of sustainable IoT devices very well in the real scenario.
