Optimizing Sensing, Computing, and Communication for Energy Harvesting IoTs: A Survey
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With businesses deploying a growing number of Internet of Things (IoTs), battery maintenance has become a limiting factor for realizing a sustainable IoT infrastructure. To overcome battery limitations, industry is now considering energy harvesting as a viable alternative to autonomously power IoT devices as much as possible, which has resulted in a number of batteryless energy harvesting IoTs (EH-IoTs) appearing in the market in recent years. Standards activities are also underway, which involve wireless protocol design suitable for EH-IoTs as well as testing procedures for various energy harvesting methods. Despite the early commercial and standards activities, IoT sensing, computing and communication under unpredictable power supply still faces significant research challenges and has become a topic of intense research. This paper surveys recent advances in EH-IoTs from several perspectives. First, it surveys the recent commercial developments for EH-IoT in terms of both products and services, followed by a review of initial standards activities in this space. Then it surveys methods that enable use of energy harvesting hardware as a proxy for conventional sensors to detect contexts more power-efficiently. The advancements in efficient checkpointing and timekeeping for intermittently powered IoT devices are reviewed next. We also survey recent research in novel wireless communication techniques for EH-IoTs, including applications of reinforcement learning to optimize power allocations on-the-fly under unpredictable energy productions as well as packet-less IoT communication and backscatter communication techniques for energy impoverished environments. We conclude the paper with a discussion of future research directions.
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