University of Utah

Welcome to the Sensing and Processing Across Networks (SPAN) lab! The SPAN lab is part of the Department of Electrical and Computer Engineering at the University of Utah.

The SPAN lab develops inventions for wireless networks which improve their security, reliability, self-awareness, and sensing capabilities. Research applies statistical signal processing, networking, and radio propagation techniques. The innovations have application in localization and tracking, secret key generation for wireless networks, network design and deployment, modeling and analysis. The lab, directed by Neal Patwari, is a combination of the efforts of several graduate and undergraduate researchers.

SPAN Announcements and News

An idea that will blow your mind

big ideas This article on, "5 Ideas That Will Blow Your Mind" mentions Xandem's motion detection product as one of those five ideas. Having RF sensing mentioned along with "A Laser Printer for DNA" and "Software That Thinks Like a Human Brain"? Kinda blows our minds.

Ossi Kaltiokallio wins best paper award at SenseApp 2012!

SenseApp logo

Ossi Kaltiokallio, Ph.D. student at Aalto University in Finland, and Maurizio Bocca and Neal Patwari, of the SPAN lab at the University of Utah, were awarded the "Best Paper Award" at the IEEE SenseApp workshop for their paper, "Follow @grandma: Long-Term Device-Free Localization for Residential Monitoring". Ossi Kaltiokallio presented the work today, 22 October 2012, in Clearwater, Florida. The work for the paper was conducted while Ossi was a visiting student in the SPAN lab. The best paper award was judged on quality of both the written paper and the oral presentation. IEEE SenseApp, an annual conference in its seventh year, is the short name of the IEEE International Workshop on Practical Issues in Building Sensor Network Applications. Only 20% of submissions were accepted as regular papers, and three were finalists for the best paper award.

Dr. Maurizio Bocca presenting at IEEE MASS 2012

MASS logo

Dr. Maurizio Bocca presented a talk Tuesday, October 9, at IEEE MASS 2012 in Las Vegas, on the paper:

For location and time, see the MASS 2012 program. A video from Dr. Bocca's presentation, posted on Youtube, shows the dramatic improvements possible when using multi-channel RSS measurements for the purpose of radio tomographic imaging.

CPS Group wins awards at EvAAL, an international tracking technology competition

EvAAL Competition at Living LabA University of Utah team of researchers has won two awards at “EvAAL”, a prestigious international competition on tracking technologies. The competition, organized by the Ambient Assisted Living Open Association, involved ten research teams from around the world, including Canada, Spain, Germany, Switzerland, France, and the US. The University of Utah’s team is called the cyber-physical systems (CPS) Group, a team led by Dr. Maurizio Bocca, with participation from faculty from the School of Computing (Dr. Suresh Venkatasubramanian and Dr. Sneha K. Kasera) and Department of Electrical and Computer Engineering (Dr. Neal Patwari). The CPS Group won the 1st place award for tracking accuracy, and the 2nd place award overall. The accuracy of the team’s localization system was superior to all other teams, but took 2nd place in the overall score, which also includes scores given by a team of judges for “installation complexity” and “user acceptance”.

The first place award for tracking accuracy awarded to the CPS Group showed that their localization system had the best tracking performance of any of the systems of the participating teams. Each team developed and tested systems that locate and track a person while they are in their own home. The teams’ systems were tested, live, at the competition, held at the Smart House Living Lab in Universidad Politecnica de Madrid (UPM) in Madrid, Spain. During the test, a person walked around in a path that was unknown to any of the teams. Each team’s system continuously reported its best guess of where it believed the person was. Then the evaluators compared the estimates to the actual path; the difference was the team’s localization error. The team with the lowest localization error was the University of Utah’s team.

Localization and tracking of people in their home may sound like a big-brother surveillance technology, however, it is meant to be used only with the person’s permission, and only when a person requires it. One major application where people need such location sensing technologies is in ambient assisted living. The idea of “ambient” assisted living is ensure the health and well-being of a person who might not be otherwise able to live in their own home. For the very elderly or those who need long-term home-based care, the use of some technology may enable to them to stay in their home longer, rather than to needing move to assisted living facilities. Localization sensing is part of this -- a caretaker could be alerted if, for example, a person has fallen and hasn’t gotten up, or if a person has been laying in bed all day.

The Utah team developed a system that doesn’t require the person to wear what is called an active badge. An active badge has a radio transmitter that periodically sends the system a message, and the system locates where that message originates. However, the user must remember to wear the active badge -- and for elderly or infirm people, it is a disadvantage that the system only works when they remember to wear the active badge. The Utah team’s technology is based on transceivers deployed in the home that use radio tomography to determine where people are moving. Radio tomography (RT) is like computed tomography (CT) scans in medical environments, except that RT uses 2.4 GHz radio waves, just like WiFi devices, rather than x-rays, like medical CT scanners. This technology has been in development at the U. of U. for four years, and its accuracy has been improving with each new technological development at the lab. The team’s tests in an apartment here in Salt Lake City, prior to the competition, showed that a person could be located within 30 cm (1 foot). No other team used radio tomography (RT) as the basis for their sensing systems. Photo of Apartment used in SLC tests

The Utah team’s localization system was highly accurate, significantly better than the other competitors. During the test, the evaluators were so surprised with the system’s accuracy that they stopped the test to make sure that there wasn’t something wrong. The evaluators re-ran the test when they realized that the system was just that accurate.

The “evaluating ambient assisted living technologies”, or EvAAL, competition, is an annual competition that draws competitors world-wide. The competition web site ( describes in detail the localization and tracking competition rules and the teams participating in this year’s competition. The announcement was made Tuesday, Sept 25, 2012, at the AAL Forum, a conference and exposition of AAL technologies in Eindhoven, The Netherlands.

The CPS Group is funded by the U.S. National Science Foundation from Grant #1035565, “Enabling and Advancing Human and Probabilistic Context Awareness for Smart Facilities and Elder Care”.

Technology Description and Video

This video shows the experimental results from a radio tomography (RT)-based two-person tracking experiment in an apartment. The people are not wearing any radio tags, instead, a wireless network of 33 (IEEE 802.15.4) transceivers deployed in the apartment measure changes in received signal strength (RSS), known as "the number of bars", caused by the people. Based on which links experience changes, the RT algorithm comes up with an image (shown at left) that has highest values (red) where it guesses that a person is located, and lowest values (blue) where it guesses that no person is located. A multi-target tracking algorithm developed by Dr. Maurizio Bocca at the University of Utah identifies from the image where the "blobs" are and what path they are taking through the apartment, using computer vision methods adapted to the RT problem. On the left, the video shows the apartment with black indicating walls, grey indicating furniture, white circle indicating the actual person location, and white X indicating the current estimate of the person. Dr. Bocca's algorithm track the two people to within an average error of about 30 cm (1 foot). Dr. Bocca and his University of Utah team used this system to compete in the EvAAL 2012 tracking competition and win 1st place for localization accuracy and 2nd place overall (overall score is an average of accuracy and other qualititative metrics from a panel of judges). (Video credit: Dr. Maurizio Bocca)

SPAN breathing detection research in Popular Science

Breathing Detection Popular Science

SPAN lab research in RSS-based breathing monitoring networks has received a mention in Popular Science, in a story titled "Seeing Through Walls With a Wireless Router". The article mentions the research results in our technical report, Monitoring Breathing via Signal Strength in Wireless Networks. In particular Popular Science included a modified version of our Figure 4 as shown at left.

UofU CPS Group to compete in EVAAL localization and activity recognition competition

University of Utah CPS group logo

The University of Utah CPS Project group will compete in the 2nd annual EVAAAL competition in Spain in July, 2012. Our team, led by postdoctoral associate Dr. Maurizio Bocca, will use radio tomography technologies in order to locate people in residential environments. EVAAL is short for "Evaluating Ambient Assisted Living Systems through Competitive Benchmarking" and is a competition designed to test the performance of technologies for "ambient" assisted living (AAL) in two tracks:

  • Track 1 on Indoor Localization and Tracking for AAL, to be held on the 2-6 July, 2012 at the Living Lab of the Polytechnic University of Madrid, Spain.
  • Track 2 on Activity Recognition for AAL, to be held on the 9-13 July, 2012 at the CIAmI Living Lab in Valencia, Spain.

Many systems are proposed and multiple research groups around the world are developing technologies. The EVAAL competition is designed to provide a single standard test environment and situation in order to benchmark different systems. Over time, providing a means to directly compare different technologies may aid in identifying the best technologies and systems for use in ambient assisted living applications. An NSF cyber-physical systems (CPS) grant titled "Enabling and Advancing Human and Probabilistic Context Awareness for Smart Facilities and Elder Care", with PIs Dr. Neal Patwari, Dr. Suresh Venkatasubramanian, Dr. Anind Dey (CMU), and Dr. Sneha K. Kasera, has helped to fund our research in this area.

Smart sensor system built to respond to laundry frustrations

Smart Facilities

Live in an apartment with a shared laundry room? Tired of towing your laundry to the laundry room only to find the washers and dryers busy? Brad Mager and Merrick McCracken have built and tested a wireless sensor system that allows you to know when the washer or dryer is free, from the comfort of your couch, or wherever you are. Their smart laundry facility system design and description was created as part of the CS/ECE 5780/6780 Embedded System Design Class. Check out the video describing the system.

IEEE Utah SP/COM Talk on Wed, April 18, 6:30pm

IEEE Prof. Neal Patwari is giving a IEEE Utah Signal Processing and Communications Chapter seminar, in WEB Room 2250, on Wednesday April 18, at 6:30pm. The talk is titled, "Radio tomography: Environmental inference from wireless network signal strength measurements".

Abstract: The received power on a link between two static wireless devices is changed when a person stands near the line those two devices. We describe multiple methods to infer a person's location in a room or building using received signal strength (RSS) changes measured in a static wireless network. We describe tomographic imaging approaches and statistical inversion methods to this problem, which we call device free localization (DFL) because the person does not participate in the system by carrying any device. We show that a person can be tracked with average errors less than 1 meter, even when using a network outside of a building to perform through-wall imaging and tracking. On some links, RSS changes even when a person is stationary, due to their inhalation and exhalation. We describe algorithms to use these changes to reliably and accurately estimate breathing rate. In summary, we describe how networks made of standard wireless devices might be used to learn characteristics of the changing environment in which they are deployed.

NOTE: The "Radio Tomography..." presentation slides are now posted.

2011-12 UofU / Argon ST Clinic Final Presentation

Argon ST UofU Clinic Team 2011-12 image

The 2011-12 UofU / Argon ST Clinic Team has their final presentation Tuesday, April 10 starting at 12:05pm, in the Officer's Club at the University of Utah. This team will present their talk titled "Low-cost high-precision absolute orientation sensor", describing their work on technologies that will enable future low cost inertial navigation systems to be highly accurate even when GPS is unavailable. The team developed a demonstration orientation sensor that combines information from accelerometers, gyroscopes, and magnetometers, in order to produce an accurate estimate of absolute orientation (what direction the device is facing compared to true North). The team is a cross-disciplinary team of senior ECE and ME students, Mino Morgese (ECE), John Greenhall (ME), Steven Kesler (ME), and Ted Thompson (ECE). Prof. Neal Patwari advises the team, which is funded with support from Argon ST, a unit of Boeing. The University of Utah Engineering "Clinic" Program allows senior engineering students to team up and use their engineering skills to work on projects of strong interest to an industry sponsor.

"Channel Sounding for the Masses" is Published

Channel Sounding for the Masses ImageA SPAN lab research effort to develop a open source, GNU Radio-based channel sounder has led to a publication that is now published. The paper, "Channel Sounding for the Masses: Low Complexity GNU 802.11b Channel Impulse Response Estimation" has been published in the IEEE Transactions on Wireless Communications. It appeared online on the 1st of December, 2011. The paper is authored by Dustin Maas, Mohammed H. Firooz, Junxing Zhang, Neal Patwari, and Sneha K. Kasera. The image to the right shows one of the central ideas of the work: Typically, channel sounders have used unmodulated pseudo-noise (PN) sequences as signals. In this paper, modulated PN signals from standard 802.11b sources are used. Because of the modulation, the cross correlation with the PN signal is not ideal, so one must take care in the channel sounder design.

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