Through-Wall 3D Motion Tracking Using Specialized Radio Waves
Earlier this year, MIT professor Dina Katabi and graduate student Fadel Adib unveiled WiVi, a system that detects people through walls and can track the direction of their movement using WiFi signals. Based on this work, Katabi and Adib have collaborated with other researchers on a new technology they call WiTrack. In comparison to WiVi, WiTrack has higher accuracy and can track both two-dimensional and three-dimensional movement using specialized radio waves, as opposed to WiFi signals. WiTrack uses multiple antennas - one for transmitting signals and three for receiving. The system then builds a geometric model of the user's location by transmitting signals between the antennas and using the reflections off a person's body to estimate the distance between the antennas and the user. WiTrack can pinpoint a person's 3D location to within 10 to 20 centimeters - about the width of an adult hand. The technology has applications in gaming, as well as fall detection among the elderly.
Transcript
00:00:00 WiTrack is a new technology that performs 3D motion tracking of a person purely using radio reflections of her body, even if the person is moving behind a wall or furniture. WiTrack is placed behind the wall of this room, as indicated by the red arrow. As the person walks around in the room, it tracks his motion through the wall. In the adjacent room, WiTrack outputs the location of the person as a red dot on the screen.
00:00:28 As the person moves around behind the wall, the red dot moves on the screen, indicating his exact location at any point in time. So let us see how WiTrack works. WiTrack performs 3D motion tracking using body radio reflections. It transmits wireless signals whose power is 100 times less than Wi-Fi and 1,000 times smaller than cell phone transmissions. These signals will reflect off the person
00:00:52 and come back to its receive antennas after some delay. WiTrack measures the delays and maps them to the distance traveled by the signals. Based on a geometric model of the antennas, WiTrack can now accurately determine the location of the person. The model incorporates new algorithms that remove reflections due to walls and furniture and focus only on the reflections of a human body, even if the person is behind a wall
00:01:15 or in a completely different room. In this demo the person walks on a spiral on the ground as the red dot tracks him in the bottom left corner of the screen. Note that the spiral on the ground is only there to show the accuracy of the system and is not used to aid localization in any way. This system has a large number of applications. For example, it performs highly accurate localization simply using reflections off a person's body
00:01:40 without requiring the person to hold any device. It can also be used in gaming, where it can start players as they run down hallways or hide behind furniture and walls for video game enemies. The system not only tracks the location of a person, but it can also track his body parts. In this example, the person is controlling different household appliances, turning them on and off by simply pointing his hand in their direction. Because WiTrack works through walls,
00:02:07 it can allow you to control appliances even from another room. So you leave a room and forget to turn off the lights. All you have to do is point your hand in the direction of that room to turn the lights off. WiTrack therefore can perform 3D motion tracking of humans and body parts simply using radio reflections off a person's body. And it works even through walls and obstructions.