Scientists Find Way to See Through Walls Using Ordinary Wi-Fi

Kathleen Villaluz

As Wi-Fi transmits signals through walls to connect users to the online realm, who knew that their emitted electromagnetic light waves could also generate holographic images? Scientists from the Technical University of Munich (TUM) found a way to capture images of the surrounding environment using simple Wi-Fi system signals.

Wi-Fi signals are used to create holographic images

[Image Source: Technical University of Munich]

Wi-Fi photography

23-year-old undergraduate physics student Philipp Holl and Dr. Friedenmann Reinhard conducted a study about generating holographic images using microwave radiation of a Wi-Fi transmitter. Wireless data transmission systems like Wi-Fi or Bluetooth emit electromagnetic waves with known information such as amplitude and phase. As these light waves occupy space, the radiation constructs a hologram having a two-dimensional wave, which front encodes a three-dimensional view of the objects where light passes through.

Ordinary optical holograms need a complex system of laser technology, whereas this Wi-Fi holographic image generator only requires two antennas: one fixed and one movable. This new technology means that an entire space can be scanned and imaged through this holographic processing of Wi-Fi or mobile phone signals.

"Using this technology, we can generate a three-dimensional image of the space around the Wi-Fi transmitter, as if our eyes could see microwave radiation", says Reinhard. "Of course, this raises privacy questions. After all, to a certain degree, even encrypted signals transmit an image of their surroundings to the outside world", added the project leader. "However, it is rather unlikely that this process will be used for the view into foreign bedrooms in the near future. For that, you would need to go around the building with a large antenna, which would hardly go unnoticed. There are simpler ways available".

Wi-fi signals used to generate holographic images

[Image Source: Technical University of Munich]

Standard domestic Wi-Fi signals were sufficient enough for the scientists to generate holograms. Philipp Holl, who conducted the experiments himself, explained how he went about setting up the process.

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"Instead of a using a movable antenna, which measures the image point by point, one can use a larger number of antennas to obtain a video-like image frequency. Future Wi-Fi frequencies, like the proposed 60 gigahertz IEEE 802.11 standard will allow resolutions down to the millimeter range".

Application of the technology

Although the study is only in its early stages, the scientists hope that advancements in the development of this technology can be used in worthwhile applications. For example, transmitting Wi-Fi through a collapsed building or under an avalanche could greatly help in rescuing trapped victims. Because this technology can generate accurate images of destroyed structures, it is considered to be more reliable than current conventional scanning methods.

This Wi-Fi photography technology could also be applied in industrial facilities to help operators track objects as they travel along the production line.

To incorporate customized paint or wallpaper for privacy, the scientists are looking to conduct further studies about the transparency of specific materials. This would help determine which materials can be used for specific applications.

The study's published paper can be found in Physical Review Letters.

Source: Technical University of Munich

SEE ALSO: Li-Fi : Light-Based Wireless Technology 100 Times Faster Than Wi-Fi

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