Exploring low-power ubiquitous sensing using RF backscatter
Abstract/Contents
- Abstract
- This thesis explores how RF backscatter can serve as an indispensable tool for designing low-power sensor networks. Low-power techniques allow sensors to be deployed where there is insufficient power or communication infrastructure for traditional sensor nodes. RF backscatter communication consumes an order of magnitude less power than even Bluetooth Low Energy. This dissertation presents three projects that advanced the state-of-the-art in sensing systems that harness RF backscatter. The first two projects, FreeRider and BackCam, describe systems that can backscatter commodity WiFi signals. Instead of having to invest in special-purpose transceivers, we can harness WiFi radios that are already ubiquitous. FreeRider is a backscatter communication platform designed to operate on top of existing ISM-band networks, like 802.11 WiFi. BackCam~\cite{backcam} extends this work by adding a camera sensor to the tag and implementing an edge-based control system. Using RF backscatter makes communication cheap, which allows us to push image processing to the edge. The next project, RayTag, demonstrates how pairing backscatter tags with radars makes the target signal 100-10,000x stronger in amplitude compared to the strongest clutter signal. This allows for simultaneous detection and identification of multiple targets, which is useful for a variety of sensing applications. To demonstrate the potential of RayTag, I show that deploying backscatter tags underground can be used to accurately measure soil moisture. Though I focus on the evaluation of sensing soil moisture, RayTag is not a single-purpose sensing system. Rather, RayTag can be used to enhance a number of existing sensing tasks (e.g. localization) or enable entirely new applications. To that end, this thesis also presents detailed evaluations beyond underground contexts, as well as multiple examples of constructing link budgets. This dissertation further explores a renewable power source for underground backscatter tags. Many backscatter communication systems can harvest their operating power via RF, but this is not practical for underground systems because wet soil attenuates RF too much for harvesting circuits to operate. One potential source of energy are microbes in the soil. Microbial fuel cells (MFCs), sometimes also known as mud or soil batteries, accept electrons that are a byproduct of redox reactions catalyzed by electrogenic microbes naturally occurring in soil. This creates a potential difference across the cathode and anode, which provides a low-cost renewable source of power. In the future, this could allow underground backscatter tags to have an indefinite lifetime.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Josephson, Colleen |
|---|---|
| Degree supervisor | Katti, Sachin |
| Thesis advisor | Katti, Sachin |
| Thesis advisor | Arbabian, Amin |
| Thesis advisor | Winstein, Keith |
| Degree committee member | Arbabian, Amin |
| Degree committee member | Winstein, Keith |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Colleen A. Josephson. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2020. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Colleen Josephson
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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