Wi-Fi imaging or “X-ray” using regular drones
Researchers at the University of California Santa Barbara achieve Wi-Fi imaging by operating two ordinary drones in tandem. By flying two drones in coordination, they were able to detect and “see” contents behind a solid brick wall. They were able to replicate a 3 dimensional structure hidden behind a wall, using nothing more than raw Wi-Fi RSSI signals. Apart from being a clever research achievement, the tech has promising implications in industry. This technique has potential applications in various fields. Some examples are forensics, archeology, emergency response, warfare, architectural planning, and construction engineering. With the growth of such drone technology, the utility of drones is becoming more apparent to previously technologically unmotivated arenas.
The imaging experiment
The objective of the experiment was to identify the contents behind a brick enclosure. The technique requires two drones – one transmitting, one listening. Mounted with large antennas, each of the two drones has its purpose.
The first step is to set the drones on an apt flight path around the target. The path of the drones is important. This is because the drones need to capture “spatial diversity”. In other words, the drones have to have a full picture. While in flight, one drone would transmit strong RF signals. The second drone would then receive the signal through the enclosure, and then calculate the effects of the environment. Therefore, the two drones would be observing slices of the target.
Why this is significant
There are a few reasons why this is a significant progress. The first reason is that this is completely non-intrusive. In order to see through obstacles, it is not necessary to know the structure of the obstacles beforehand. The system is intellgient enough to figure out environments on its own.
The second reason is that the signals used for imaging are non-harmful. Despite the ominous association with X-rays, they are simply typical Wi-Fi signals and are not harmful to humans.
Another reason is the use of RSSI. This is a slightly technical reason. RSSI implies signal strength. This metric is used to asses the quality of a Wi-Fi network. Therefore, it is the most used metric in typical products. This could mean that new products could utilize RSSI with minimal hardware costs.
This was published to ACM by UCSB researchers Chitra Karanam, and Yasamin Mostofi.