Wi-Fi could protect you from getting lost in virtual reality
Their solution, which they call WiCapture, requires two parts: a standard Wi-Fi chip, such as the one you might find in your phone, and at least two Wi-Fi “access points,” which are transmitters such as the ones found in home routers. Communication between the chip and a transmitter comes in high-frequency radio waves. In order to track a Wi-Fi signal source with millimeter-level accuracy, one needs to measure the time it takes a signal to travel from the chip to the transmitter with picosecond-level accuracy. However, the chip and transmitter have different clocks, and no two clocks in Wi-Fi devices are perfectly synchronized.
To get around this problem the researchers took advantage of the fact that signals reach the transmitter through many paths. Some radio waves travel directly to the receiver to create the main signal, whereas others bounce off walls to create echoes. Kotaru wrote an algorithm that looks at signals from two different paths, identified by triangulating among the transmitter’s multiple antennas. Those signals will be equally affected by clock asynchrony, so the algorithm can just compare their relative change as the chip moves and ignore the drift of the clocks’ timing. Still, this method measures distance to only one transmitter; using two or more transmitters in combination allows the algorithm to use triangulation to track motion in two dimensions. (The researchers will eventually expand WiCapture to track motion in three dimensions.)
He notes that 1 centimeter is not a high enough accuracy for head tracking, but would work for hand tracking. In a fighting game, “I’m not sure I’m going to do any small delicate movements with a sword.”
The authors acknowledge that WiCapture still has a slower reaction time and lower accuracy than infrared cameras, but they think they can improve both by combining it with an accelerometer to add another source of data and fill in the gaps. In any case, Kotaru says, the technology is basically ready to use.
See the full story here: http://www.sciencemag.org/news/2017/07/wi-fi-could-protect-you-getting-lost-virtual-reality