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dRTI: Directional Radio Tomographic Imaging
University of New South Wales, Sydney, Australia and CSIRO, Brisbane, Australia and SICS, Stockholm, Sweden.
Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
University of Utah, Salt Lake City and Xandem Technology, Salt Lake City.
University of New South Wales, Sydney, Australia and CSIRO, Brisbane, Australia and SICS, Stockholm, Sweden.
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2015 (English)In: Proceedings of the 14th International Conference on Information Processing in Sensor Networks, 2015, p. 166-177Conference paper, Published paper (Refereed)
Abstract [en]

Radio tomographic imaging (RTI) enables device free localisation of people and objects in many challenging environments and situations. Its basic principle is to detect the changes in the statistics of radio signals due to the radio link obstruction by people or objects. However, the localisation accuracy of RTI suffers from complicated multipath propagation behaviours in radio links. We propose to use inexpensive and energy efficient electronically switched directional (ESD) antennas to improve the quality of radio link behaviour observations, and therefore, the localisation accuracy of RTI. We implement a directional RTI (dRTI) system to understand how directional antennas can be used to improve RTI localisation accuracy. We also study the impact of the choice of antenna directions on the localisation accuracy of dRTI and propose methods to effectively choose informative antenna directions to improve localisation accuracy while reducing overhead. Furthermore, we analyse radio link obstruction performance in both theory and simulation, as well as false positives and false negatives of the obstruction measurements to show the superiority of the directional communication for RTI. We evaluate the performance of dRTI in diverse indoor environments and show that dRTI significantly outperforms the existing RTI localisation methods based on omni-directional antennas.

Place, publisher, year, edition, pages
2015. p. 166-177
Series
IPSN ’15
National Category
Computer Systems
Identifiers
URN: urn:nbn:se:uu:diva-252426DOI: 10.1145/2737095.2737118OAI: oai:DiVA.org:uu-252426DiVA, id: diva2:810260
Conference
ACM/IEEE IPSN 2015
Available from: 2015-05-06 Created: 2015-05-06 Last updated: 2018-03-16
In thesis
1. Enabling Sustainable Networked Embedded Systems
Open this publication in new window or tab >>Enabling Sustainable Networked Embedded Systems
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Networked Embedded Systems (NES) are small energy-constrained devices typically with sensors, radio and some form of energy storage. The past several years have seen a rapid growth of applications of NES, with several predictions stating billions of devices deployed in the near future. As NES are deployed at large scale, a growing challenge is to support NES for long periods of time without negatively impacting their physical or the radio environment, i.e., in a sustainable manner. In this dissertation, we identify intertwined challenges that affect the sustainability of NES systems: co-existence on the shared wireless spectrum; energy consumption; and the cost of the deployment and maintenance. We identify research directions to overcome these challenges and address them through the six research papers.

Firstly, NES have to co-exist with other wireless devices that operate on the shared wireless spectrum. A growing number of devices contending for the spectrum is challenging and leads to increased interference among them. To enable NES to co-exist with other wireless devices, we investigate the use of electronically steerable directional antennas (ESD). ESD antennas allow software-based control of the direction of maximum antenna gain on a per-packet basis and can operate within the severe energy constraints of NES. In the dissertation, we demonstrate that ESD antennas allow solutions that outperform the state-of-the-art in sensing and communication in wireless sensor networks while supporting operations on a single wireless channel reducing the contention on the shared wireless spectrum.

Secondly, we explore the emerging area of visible light sensing and communication to avoid the crowded radio frequency spectrum. Visible light can be an alternative or a complement to radio frequency for sensing and communication. We make two contributions in the dissertation to make the visible light communication a viable option for NES. We design a novel visible light sensing architecture that supports sensing and communication at tens of microwatts of power. An ultra-low power consumption can make visible light sensing systems pervasive. Our second contribution brings high-speed visible light communication to energy-constrained NES. We design a novel visible light receiver that adapts to the dynamics of changing light conditions, and the energy constraints of the host device while supporting a throughput comparable to radio frequency standards for NES. Through our contribution, we take a significant step to enable visible light-based sustainable NES.

Finally, replacing batteries on sensor nodes significantly affects the sustainability of NES. Battery-free sensors that harvest small amounts of energy from the ambient environment have a great potential to enable pervasive deployment of NES. To support wide-area deployments of battery-free sensors, we develop an ultra-low power and long-range communication mechanism. We demonstrate the ability to communicate to distances as long as a few kilometres while consuming tens of microwatts at the sensor device. Our contributions pave the way for a wide-area deployment of battery-free sustainable NES.

Through the contributions made in the dissertation, we take a significant step towards the broader goal of sustainable NES. The work included in the dissertation significantly improves the state-of-the-art in NES, in some case by orders of magnitude.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 52
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1648
Keyword
Wireless Sensor Network; Energy harvesting; backscatter; RFID; Sensors
National Category
Computer Systems
Research subject
Computer Science with specialization in Computer Communication
Identifiers
urn:nbn:se:uu:diva-346267 (URN)978-91-513-0279-9 (ISBN)
Public defence
2018-05-07, 2446, ITC, Lägerhyddsvägen 2, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-04-18 Created: 2018-03-16 Last updated: 2018-04-18

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