Eliminating Battery Replacement Throughout the Useful Life of IoT Devices with Limited-Capacity Batteries: Analysis and Design of a Zero Energy Air Interface

In cellular systems, IoT devices usually encounter a compromise between device’s reachability and its battery life. Reducing the communication latency entails reducing the battery life. To mitigate this compromise, the lifetime of a battery powered wireless device can be significantly extended by deploying ultra-low power (ULP) receivers with energy harvesting capabilities operating over a zero-energy (ZE) downlink air-interface that does not draw power from the device’s battery. In this paper, we investigate the feasibility of the ZE downlink air interface, as a supplement to a Uu air-interface, in supporting IoT devices with limited-capacity batteries. We formulate an online energy management policy to handle energy consumption and harvesting requirements. We then develop an analysis for the probability distributions of the battery’s charge levels across time instances, followed by a simulation framework aimed at evaluating the correct decoding probability of the information messages. Simulation results show that better than 90% probability of both successful ZE operation and correct message decoding can be achieved for receiver power consumption of less than 120nW while maintaining network resource utilization to less than 5%.