The new device developed by MIT professor Dina Katabi and graduate student Fadel Adib is called Wi-Vi, stands for WiFi Vision, as it employs wireless signals transmitted by a WiFi device – so it would allow us to see a person moving behind a wall
tracked by all the signals bouncing off that person to produce a kind of X-ray vision
WiFi doesn’t just bounce off humans but also other objects in a room such as floors and furniture, so the trick is eliminating all the interfering signals, which are 10,000 to 100,000 times more powerful than the reflections off a human body.
To remove the signals of all the interfering objects, the Wi-Vi device sends out two wireless signals that keep canceling each other unless they hit a moving target – humans. "To silence the noise, we change the structure of the WiFi signal
so all the undesired reflections are canceled," Dina Katabi said.
Their previous works has shown that subtle reflections of wireless inter signals bouncing off a human could be used to track that person's movements, but those experiments either required that a wireless router was already in the room of the person being tracked, or a whole truck just to carry the radio – contrary to this, the new device is meant to be portable, said Katabi.