Bodies and objects essentially absorb WiFi as they move around in rooms
Whether you’re trying to figure out how many students are attending your lectures or how many evil aliens have taken your Space Force brethren hostage, Wi-Fi can now be used to count them all.
The system, created by researchers at UC Santa Barbara, uses a single Wi-Fi router outside of the room to measure attenuation and signal drops. From the release:
The transmitter sends a wireless signal whose received signal strength (RSSI) is measured by the receiver. Using only such received signal power measurements, the receiver estimates how many people are inside the room — an estimate that closely matches the actual number. It is noteworthy that the researchers do not do any prior measurements or calibration in the area of interest; their approach has only a very short calibration phase that need not be done in the same area.
This means that you could simply walk up to a wall and press a button to count, with a high degree of accuracy, how many people are walking around. The system can measure up to 20 people in its current form.
The system uses a mathematical model to “see” people in the room based on signal strength and attenuation. The system uses off-the-shelf components and they’ve tested it in multiple locations and found that their total accuracy is two people or less with only one Wi-Fi device nearby.
Bodies and objects essentially absorb Wi-Fi as they move around in rooms, allowing the system to find discrete things in the space. Sadly it can’t yet map their position in the room, a feature that could be even more helpful in the future.