Featured Research

from universities, journals, and other organizations

New system uses low-power Wi-Fi signal to track moving humans -- even behind walls

Date:
June 28, 2013
Source:
Massachusetts Institute of Technology
Summary:
A system being developed at MIT could give all of us the ability to spot people in different rooms using low-cost Wi-Fi technology.

The comic-book hero Superman uses his X-ray vision to spot bad guys lurking behind walls and other objects. Now we could all have X-ray vision, thanks to researchers at MIT's Computer Science and Artificial Intelligence Laboratory.

Related Articles


Researchers have long attempted to build a device capable of seeing people through walls. However, previous efforts to develop such a system have involved the use of expensive and bulky radar technology that uses a part of the electromagnetic spectrum only available to the military.

Now a system being developed by Dina Katabi, a professor in MIT's Department of Electrical Engineering and Computer Science, and her graduate student Fadel Adib, could give all of us the ability to spot people in different rooms using low-cost Wi-Fi technology. "We wanted to create a device that is low-power, portable and simple enough for anyone to use, to give people the ability to see through walls and closed doors," Katabi says.

The system, called "Wi-Vi," is based on a concept similar to radar and sonar imaging. But in contrast to radar and sonar, it transmits a low-power Wi-Fi signal and uses its reflections to track moving humans. It can do so even if the humans are in closed rooms or hiding behind a wall.

As a Wi-Fi signal is transmitted at a wall, a portion of the signal penetrates through it, reflecting off any humans on the other side. However, only a tiny fraction of the signal makes it through to the other room, with the rest being reflected by the wall, or by other objects. "So we had to come up with a technology that could cancel out all these other reflections, and keep only those from the moving human body," Katabi says.

Motion detector

To do this, the system uses two transmit antennas and a single receiver. The two antennas transmit almost identical signals, except that the signal from the second receiver is the inverse of the first. As a result, the two signals interfere with each other in such a way as to cancel each other out. Since any static objects that the signals hit -- including the wall -- create identical reflections, they too are cancelled out by this nulling effect.

In this way, only those reflections that change between the two signals, such as those from a moving object, arrive back at the receiver, Adib says. "So, if the person moves behind the wall, all reflections from static objects are cancelled out, and the only thing registered by the device is the moving human."

Once the system has cancelled out all of the reflections from static objects, it can then concentrate on tracking the person as he or she moves around the room. Most previous attempts to track moving targets through walls have done so using an array of spaced antennas, which each capture the signal reflected off a person moving through the environment. But this would be too expensive and bulky for use in a handheld device.

So instead Wi-Vi uses just one receiver. As the person moves through the room, his or her distance from the receiver changes, meaning the time it takes for the reflected signal to make its way back to the receiver changes too. The system then uses this information to calculate where the person is at any one time.

Possible uses in disaster recovery, personal safety, gaming

Wi-Vi, being presented at the Sigcomm conference in Hong Kong in August, could be used to help search-and-rescue teams to find survivors trapped in rubble after an earthquake, say, or to allow police officers to identify the number and movement of criminals within a building to avoid walking into an ambush.

It could also be used as a personal safety device, Katabi says: "If you are walking at night and you have the feeling that someone is following you, then you could use it to check if there is someone behind the fence or behind a corner."

The device can also detect gestures or movements by a person standing behind a wall, such as a wave of the arm, Katabi says. This would allow it to be used as a gesture-based interface for controlling lighting or appliances within the home, such as turning off the lights in another room with a wave of the arm.

Venkat Padmanabhan, a principal researcher at Microsoft Research, says the possibility of using Wi-Vi as a gesture-based interface that does not require a line of sight between the user and the device itself is perhaps its most interesting application of all. "Such an interface could alter the face of gaming," he says.

Unlike today's interactive gaming devices, where users must stay in front of the console and its camera at all times, users could still interact with the system while in another room, for example. This could open up the possibility of more complex and interesting games, Katabi says.


Story Source:

The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by Helen Knight. Note: Materials may be edited for content and length.


Cite This Page:

Massachusetts Institute of Technology. "New system uses low-power Wi-Fi signal to track moving humans -- even behind walls." ScienceDaily. ScienceDaily, 28 June 2013. <www.sciencedaily.com/releases/2013/06/130628092149.htm>.
Massachusetts Institute of Technology. (2013, June 28). New system uses low-power Wi-Fi signal to track moving humans -- even behind walls. ScienceDaily. Retrieved November 27, 2014 from www.sciencedaily.com/releases/2013/06/130628092149.htm
Massachusetts Institute of Technology. "New system uses low-power Wi-Fi signal to track moving humans -- even behind walls." ScienceDaily. www.sciencedaily.com/releases/2013/06/130628092149.htm (accessed November 27, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Thursday, November 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA's First 3-D Printer In Space Creates Its First Object

NASA's First 3-D Printer In Space Creates Its First Object

Newsy (Nov. 26, 2014) The International Space Station is now using a proof-of-concept 3D printer to test additive printing in a weightless, isolated environment. Video provided by Newsy
Powered by NewsLook.com
Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Blu-Ray Discs Getting Second Run As Solar Panels

Blu-Ray Discs Getting Second Run As Solar Panels

Newsy (Nov. 26, 2014) Researchers at Northwestern University are repurposing Blu-ray movies for better solar panel technology thanks to the discs' internal structures. Video provided by Newsy
Powered by NewsLook.com
Today's Prostheses Are More Capable Than Ever

Today's Prostheses Are More Capable Than Ever

Newsy (Nov. 26, 2014) Advances in prosthetics are making replacement body parts stronger and more lifelike than they’ve ever been. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins