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

Student Paper Competition Finalist

Radio Wireless Week imageMerrick McCracken, a graduate student researcher in the SPAN lab, has had his paper selected to be a Student Paper Competition Finalist at Radio Wireless Week. His paper, Hidden Markov Estimation of Bistatic Range From Cluttered Ultra-wideband Impulse Responses, will be presented on Wednesday, January 18, 2012 during the IEEE Topical Meeting on Wireless Sensors and Sensor Networks, one of the workshops associated with Radio Wireless Week. Merrick will also present a poster during the student paper competition session on Monday, January 16. Congratulations to Merrick on his paper's selection as a finalist in the competition.

Two upcoming presentations at COMSNETS 2012

Comsnets 2012 image
University of Utah graduate student researchers Dustin Maas and Sriram Nandha Premnath will each present papers at COMSNETS 2012 this January, in Bangalore, India. Dustin Maas will present his paper, "Experimental Performance Evaluation of Location Distinction for MIMO Links" on January 5th. The following day, January 6th, Sriram Nandha Premnath will present his paper, "Beyond OFDM: Best Effort Dynamic Spectrum Access Using Filterbank Multicarrier".

Postdoc opening

We are now advertising the SPAN Lab's postdoctoral researcher position that is currently open. Information about the position is up and those interested are welcome to submit their application.

"Catching a Breath – Wirelessly" is Catching On

Breathing signal strength
Research news from the SPAN lab, featured in a news release titled Catching a Breath – Wirelessly, has been written up on tech news sites such as Engadget, Popular Science, CNET, InformationWeek, PC World, New Scientist, LifeHacker, and Gizmodo. The news story has also been picked up by international press, by the Russian Compulenta, the German Pressetext, and the Hungarian HWSW. SPAN researchers have shown that standard wireless devices deployed around a person can be used to reliably detect breathing and accurately estimate the rate at which the person is breathing, and have submitted the research results for publication. While specialized RF devices have been proposed which can also detect and monitor breathing, the new research shows that a standard wireless network can be used for this purpose. A technical report, titled Monitoring Breathing via Signal Strength in Wireless Networks is under submission to the IEEE Transactions on Mobile Computing and is posted on

To address some of the questions and misleading statements made in some press articles, here are some frequently asked questions and answers:

Q: Is it true that someone could spy on me using my WiFi router?

A: It is possible, but with current technology, not very likely. We showed that a single link, even with the wireless devices right next to a person's body, has only a small (<5%) chance of being able to detect the person's breathing. For someone to reliably detect your breathing, they would need many wireless devices, more than just your wireless router. We used 20 wireless devices.

Q: How accurate were the breathing rate estimates?

A: In tests using thirty seconds of data, we were able to estimate the true breathing rate within 0.3 breaths per minute. This is the root-mean-squared (RMS) error. The breathing rates we tested were 12.0, 15.0, and 19.0 breaths per minute.

Q: Is it true that you can measure lung capacity or volume of air exhaled?

A: Not with our technology. We can't estimate the change in size of the person's chest when they inhale or exhale. In fact, we can't measure that they've exhaled any air -- in obstructive apnea, some people move their chest up and down while no air is exhaled or inhaled.

Q: Is it true that you can measure heart rate?

A: Absolutely not. Some articles on the web have inexplicably replaced "breathing rate" with "heart rate". Your pulse does not cause enough change to be noticed by our system. However, some radar devices have been shown to be able to measure heart rate -- see the paper: N. Rivera, S. Venkatesh, C. Anderson, and R. Buehrer, Multi-target estimation of heart and respiration rates using ultra wide-band sensors, in Proc. of the 14th European Signal Processing Conference, 2006.

Q: Would these radio waves interfere with medical equipment in a hospital?

A: Other wireless devices that send signals at 2.4 GHz are already used in hospitals. In fact, devices that transmit Zigbee signals (the devices we used) are already used in hospitals to help keep track of critical medical equipment. Because our devices transmit very little information, and relatively infrequently, they can interoperate with other wireless devices that operate on the same band.

Q: Does the patient risk getting cancer from the radio waves?

A: We refer to the National Cancer Institute website for information summarizing the many, many studies of human exposure to radio waves. Further, these devices, in use in a future product, would probably be set to transmit 10,000 times less power than your laptop or cell phone transmits. Thus any exposure to the patient from these devices would be insignificant to the exposure already incurred from other wireless devices.

KSL shows Joey Wilson and tomographic motion detection on the evening news!

John Hollenhorst Reporting on Xandem's Product
KSL in Salt Lake City ran a story on the evening news (Thursday July 21) on SPAN graduate Joey Wilson's "tomographic motion detection" system, which he has commercialized at startup company Xandem. The story, by KSL technology anchor John Hollenhorst, discusses the technology as a spin off of his PhD thesis research, and shows it in action as part of a home security system.

Croft Dissertation Defense

Congratulations to Jessica Croft, who passed her dissertation defense! Her oral presentation and dissertation, titled "Shared Secret Key Extraction from Wireless Channel Measurements", were defended during a public presentation on Wednesday, July 27. Dr. Jessica Croft will be joining Schweitzer Engineering Laboratories starting in August. We congratulate her on her excellent Ph.D. work and wish her the best in her upcoming position.

First Ever Tomographic Motion Detection System Launched by Xandem

The first ever radio tomographic motion detection product was recently launched by Xandem Technology. The roots of the new product come from the SPAN lab's research on radio tomographic imaging and device-free localization. From the press release:

“Xandem’s tomographic motion detection (TMD) techology is a new way to detect movement within a defined area. The system can be completely hidden by embedding the devices in walls or behind objects, and is much more robust to false alarms than infrared sensors.” claims Xandem founder Joey Wilson. “We are currently selling our systems to integrators and product developers in industries that see a need for unbeatable motion detection with many new features.”

Xandem motion detector
Click here to read the full press release

Xandem was founded by Joey Wilson, an alum of the SPAN lab, and Neal Patwari is Xandem's director of research.

Paper and demo presentation at SECON

SPAN researcher Yang Zhao will present his research in "Noise Reduction for Variance-Based Device-Free Localization and Tracking" on Wednesday June 29 at IEEE SECON 2011, which is here in Salt Lake City the week of June 27-30. The talk on his paper is during the 10:30-noon "Detection and Tracking" session. He will also present a live demonstration of his SubVRT algorithm at the SECON demo session, which is being held Tuesday from 5-6:30pm. See the SECON program for more details.

"See through walls" selected by IEEE TMC as Spotlight Paper

Joey Wilson and Neal Patwari's paper, "See-Through Walls: Motion Tracking Using Variance-Based Radio Tomography Networks" has been selected as the Spotlight Paper for the May 2011 issue of the IEEE Transactions on Mobile Computing! Their paper is currently highlighted on the IEEE Transactions on Mobile Computing home page and will be available to the public for free for 30 days. To see the "spotlighting" of their paper, go to

Dr. Neal Patwari Wins University of Utah Early Career Teaching Award

Congratulations to SPAN director Dr. Neal Patwari for winning the University of Utah Early Career Teaching Award! This award given only to a few professors at the University who have demonstrated exceptional teaching qualities. Here's the description:

"A nominee for the Early Career Teaching Award shall have demonstrated distinction in teaching, demonstrated by activities that result in increased learning by students, such as the development of new methods or other curricular innovation. Nominations may be made by any member of the University Community, i.e., students, faculty, administrators, alumni, etc. The University Teaching Committee evaluates nominees based on a Teaching Portfolio, a curriculum vitae, three letters of support, and student evaluations."

Congratulations Neal for this outstanding accomplishment!

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