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Title
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Enabling bidirectional communication on batteryless devices for sustainable IoT
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Author
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Abstract
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| The Internet of Things (IoT) envisions billions of smart sensors and actuators to be connected to the Internet. These devices impose three main requirements on wireless networks: wide transmission range, low cost, and low power consumption. The last requirement is crucial for the devices to have long autonomy, thus reducing the need for device maintenance. Low-power networks, such as Low Power Wide Area Network (LPWAN) for long-range transmission and Wireless Personal Area Networks (WPAN) for short-range transmission, promise to fulfil the stated IoT requirements. The LPWAN Narrowband Internet of Things (NB-IoT) and WPAN Bluetooth Low Energy (BLE) radio technologies are popular and enable low-cost and low-power devices. Such communication technologies optimize energy consumption by introducing a sleep or deep sleep state, allowing the device to spend most of its time in a low-power state. This potentially enables IoT devices to operate for several years, powered by small coin cell batteries. Nevertheless, while the device is in this sleep state, it is unreachable and cannot immediately receive any downlink (DL) data. Thus, saving the battery life comes at the cost of DL data latency. The uplink (UL) data communication is mostly controlled by the device and is therefore less impacted, as the device can wake-up when it needs to transmit data. Despite being energy-efficient technologies, most IoT devices still require frequent manual battery replacement. This increases operational costs and limits the feasibility to deploy in remote areas, and also affects the environment due to the harmful chemicals that the discarded batteries can leak into the soil. Therefore, the interest in energy harvesting (EH) from ambient sources and usage of a small capacitor to store the energy has been rising. A key challenge in ensuring sustainable energy harvesting is dealing with the time-varying energy supply and changing device power demand. The much smaller energy density of the capacitor and unpredictable availability of harvested energy result in intermittent on-off behaviour of the device. This means a batteryless device can turn on and off frequently, and that can further impact its data latency. This thesis studies the trade-off between energy consumption and communication latency for BLE Mesh and NB-IoT. Additionally, batteryless prototypes based on indoor light are also developed by leveraging the Bluetooth Mesh friendship and NB-IoT power saving features. The suitability of using Bluetooth Mesh and NB-IoT in the context of intermittently powered devices is also evaluated by analyzing their energy requirements in different radio states. |
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Language
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English
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Publication
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Antwerpen
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University of Antwerp, Faculty of Science
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2022
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Volume/pages
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xviii, 138 p.
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Note
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Famaey, Jeroen [Supervisor]
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Full text (open access)
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