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EXPLOITING LUMINESCENCE EMISSIONS OF SOLAR CELLS FOR INTERNET-OF-THINGS (IOT) APPLICATIONS
thesisposted on 30.04.2021, 01:07 authored by Xiaozhe FanXiaozhe Fan
The Internet-of-Things (IoT) devices have experienced an explosive growth during the last decades. The number of IoT devices is predicted to reach 36.4 billion by 2025, resulting in an urgent demand for high-density and high-capacity network connectivity. Recently, self-powered optical wireless devices have attracted more attention from both academia and industry. Although radio frequency (RF) technologies are readily available for various wireless applications, the RF
communication bands are becoming saturated due to the scarcity of the RF spectrum. Optical wireless communication (OWC) provides an attractive solution to overcome the shortage of RF bands. OWC is also attractive for low-power or even self-powered applications since optical energy is the most abundant in both indoor and outdoor scenarios.
This dissertation explores a new optical communication technique called optical frequency identification (OFID). This technique employs solar cells as an optical antenna, capable of harvesting energy and transmitting/receiving optical information. Transmission of information with a solar cell is achieved by modulating the cell's luminescent emissions. Two OFID system prototypes were designed,
fabricated, evaluated, and discussed.
A series of experiments have been carried out to exploit the feasibility of using a solar cell's luminescence emissions for optical communication and evaluate proposed two OFID system prototypes. This dissertation validated that luminescent emissions from a GaAs solar cell can be modulated for optical communications. Then, two photoluminescence (PL) modulators were proposed and compared in terms of their energy harvesting and communication performances. The first OFID system prototype, based on a dual-aperture reader and a microcontroller-based tag was validated and experimented for a remote temperature sensing application. The second prototype, based on a single-aperture OFID reader and an FPGA-based OFID module, was analyzed with an emphasis on the communication date rate, communication range, tag's cold-startup period and power consumption.