Lighting IoT Test Environment (LITE) Platform: Evaluating Light-Powered, Energy Harvesting Embedded Systems

摘要

As interest in the Internet of Things (IoT) grows, so does the requirement for distributed sensing, computation, and communication. Some projections reach a scale of over a trillion wireless devices, which creates a battery replacement challenge that is unsustainable for both human resources (replacement effort) and the environment (disposal). One field of research that strives to meet this challenge is energy harvesting (EH) for self-powered systems. Photovoltaic (PV) cells enable EH capabilities and provide high energy density. They are also typically inexpensive, often making them the transducer of choice for self-powered systems. However, the performance of these EH nodes is rarely evaluated under realistic IoT environmental conditions, such as variable indoor lighting. Under low light, PV cells draw very little power and could place the self-powered system in a standby or even nonfunctional state. Most evaluations of EH systems in various lighting environments use software simulations to predict the behaviour of these nodes, but approximate models lack the exactness required to help with verification of hardware in real conditions. Another approach is user testing in the field, but this arduous solution would incur a variety of costs. This paper presents a third alternative: the Lighting IoT Test Environment (LITE) platform. The LITE platform is a tool that provides insight on how light-powered EH systems operate in low lighting environments. The LITE platform is able to physically emulate a variety of indoor and outdoor lighting sources with a novel mapping technique and provide time-series, environmental simulation of that source on a device under test (DUT). The light source emulation and time-series simulation capabilities are characterized with a worst case mean absolute percentage error (MAPE) of 3.2% and MAPE of 0.5%, respectively. By enabling engineers to accurately understand how these self-powered systems work under real world conditions, the LITE platform will better equip them to design, debug, and distribute fully functional and sustainable IoT nodes.