Reflection of Modulated Radio: Design, Analysis and Characterization of Long-Range Ambient Scatter Communication Systems
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Varner, Michael Austin
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Abstract
A multi-faceted exploration of the field of Ambient Scatter Communications using a first-of-its-kind prototype was proposed. A generalized theoretical basis for the emerging technology is presented. Current solutions implemented by previously published state-of-the-art devices are discussed and compared using figures of merits proposed in the work. The perfect pulse waveform, an original mathematical concept, is described and generalized for communications applications and beyond. Focus is placed on perfect pulse frequency shift keying and a methodology is shared for channel code selection. Multiple demodulation methods ranging from the canonical (e.g. matched filter) to the exotic (e.g. inaugural uses of machine learning on a functional system) are shared. A custom hardware system is constructed and designed to enhance dynamic range in the presence of strong in-band interference. The prototype system, characterized in depth, features the unique use of deep-null antennas and analog filtering stages to remove interference prior to digitization. An application specific signal strength prediction tool is created, suggesting real-world propagation effects on radio links of this type. The prototype is utilized in measurement campaigns at varied receiver and tag/node distances in the immediate vicinity of a strong ambient source broadcaster. Communications metrics are calculated via data post-processing and the demodulation methods are compared. The overall system performance is compared to previously published devices. Data indicate that the system, which achieves some of the highest ever recorded data rates in the field, is uniquely suited to extend ranges for next-generation systems if interference remains the primary range limiting factor. Future work ranging from next-generation hardware, measurement aided simulation tools, machine learning techniques, and possible applications are discussed.
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2024-04-04
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Dissertation