"Looking" at WiFi

New technology created at Oregon State University can use LED lighting to boost the bandwidth of Wi-Fi systems by about 10 times. Credit: Thinh Nguyen/Oregon State University

Modulating a signal on a light beam is nothing new. Basically most of our communications go through optical modulation over optical fiber. Researchers have also studied ways to use free air to transport a light beam and it is now at least two decades that a few optical connections exist between buildings roofs. The advantage is that air has no installation nor maintenance cost. On the other hand you need a good “line of sight” and weather can also limit the effectiveness of transmission (fog and rain can degrade the signal significantly). So far most of optical modulation has been using a laser beam.

Researchers have also tried the use of LEDs but the intensity of the light generated by a LED is limited and a receiver can get confused by other lights coming from different sources, thus leading to a low bandwidth (the bandwidth is tied to the noise, the more noise the less bandwidth).

Now a team at the Oregon State University have thought of using LEDs transmitting in a part of the light spectrum that is invisible to our eye, and that is not used  by common light sources (that are obviously designed to operate in the visible light spectrum). 

This has allowed them to modulate a signal providing up to 100Mbps capacity. The intensity of the LED remains low but they have managed to focus the beam to create a usable space around a square meter. This keeps the beam at a reasonable strength for a good reception and although it won’t cover a sizable surface if rightly positioned can provide connectivity for your television or for you sitting on the couch. This has the added advantage that it will serve just one or two users at most, hence the bandwidth provided will not need to be shared by severl users keeping the usable capacity high.

The LED itself costs about a dollar and so does the receiver, for the time being a dongle connecting your device via a USB port or in the future embedded in your device.

This WiFiFO (WiFi over Free space Optics) does not interfere with the usual WiFi so the two can well coexist, the first serving very specific spots, the second covering the whole ambient. Of course one can place several LEDs in convenient places to “illuminate” a few desired spots in the living room or in a hospital room. By using optical signals it does not interfere with electronics so it is safer in places where sensitive apparatus are used (like in a hospital room monitoring a patient).

Just one more way to keep us connected.

Author - Roberto Saracco

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