Researchers at MIT’s Computer Science and Artificial Intelligence Lab (CSAIL) have developed a motion tracking system that allows for highly accurate, 3-D motion tracking.
The new system, named "WiTrack", uses radio signals to track a person through walls and obstructions, pinpointing 3-D location to within 10 to 20 centimeters.
"Today, if you are playing a game with the Xbox Kinect or Nintendo Wii, you have to stand right in front of your gaming console, which limits the types of games you can play," said Dina Katabi, a professor of computer science and engineering and co-director of the MIT Center for Wireless Networks and Mobile Computing.
"Imagine playing an interactive video game that transforms your entire home into a virtual world. The game console tracks you as you run down real hallways away from video game enemies, or as you hide from other players behind couches and walls. This is what WiTrack can bring to video gaming."
WiTrack works by tracking radio signals reflected off a person’s body to pinpoint location and movement. The system 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, said MIT.
"Because of the limited bandwidth, you cannot get very high location accuracy using WiFi signals," Katabi’s graduate student Fadel Adib said.
"WiTrack transmits a very low-power radio signal, 100 times smaller than WiFi and 1,000 times smaller than what your cell phone can transmit. But the signal is structured in a particular way to measure the time from when the signal was transmitted until the reflections come back. WiTrack has a geometric model that maps reflection delays to the exact location of the person. The model can also eliminate reflections off walls and furniture to allow us to focus on tracking human motion."
The ability of the WiTrack system to perform high-accuracy localisation without expending enormous amounts of computational power is a promising new development in motion-tracking technology, according to Victor Bahl, a principal researcher and director of mobility and networking research at Microsoft Research.
"Motion tracking has generally been accomplished by analysing images captured from strategically placed cameras inside the room. A limitation of such systems is that they only work when the moving object is directly in the camera’s line of sight," Bahl said.
The researchers will present their findings during the Usenix Symposium on Networked Systems Design and Implementation in April 2014.
