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Researchers Create 3 Gb/s LiFi network with LEDs

By - Source: Extreme Tech | B 12 comments

Researchers at the Fraunhofer Henrich Hertz Institute have developed a LiFi prototype that is capable of 3 Gb/s in laboratory settings.

A team of researchers at the Fraunhofer Henrich Hertz Institute (HHI) in Germany has developed a Visible Light Communications (VLC) or LiFi system that while using conventional LEDs has successfully transmitted data at 3 Gb/s in a laboratory environment and 500 Mb/s under "less-than-optimal atmospheric conditions" during a trade fair.

For those who haven't come across it before, VLC functions in a similar manner to WiFi except that it oscillates an LED instead of a WiFi transmitter and transmits light instead of microwave radiation.

LiFi holds immense potential, because it can turn virtually any LED lamp into a network connection. Since it operates in the hundreds of terrahertz range, it avoids the "wireless spectrum crunch" and its associated licensing problems. The latter aspect will also allow it to be used in areas where there's extensive RF noise or in locations where RF noise is prohibited, such as hospitals.

As one would expect with any technology, LiFi is not yet commercially viable, as there are no known roadmaps or plans to bring LiFi equipped devices to market. Development seems thus far limited to a handful of research groups and startups. This being said, the technology's versatility and obvious application mean that we're inclined to agree with Extreme Tech's Sebastian Anthony that it is "just a matter of time until LiFi becomes a reality."

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  • -2 Hide
    Antimatter79 , April 12, 2013 4:10 PM
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    antilycus , April 12, 2013 4:43 PM
    great, until buildings (like my home) start using LED lights that will interfear with the signal
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    dalethepcman , April 12, 2013 4:46 PM
    I wonder what the range using consumer grade LED lights is, and how much this can be increased by using larger or brighter diodes. The best commercial application I can see for this currently is to apply fiber speed connections over line of sight distances for new or temporary offices for sharing domain connectivity. Installing fiber takes time with permitting and has a high infrastructure cost, where these could potentially be a single day setup.
  • Display all 12 comments.
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    smeezekitty , April 12, 2013 5:46 PM
    great, until buildings (like my home) start using LED lights that will interfear with the signal

    The type of building lighting shouldn't really affect performance. That said, infrared would most likely be much more practical.
  • 2 Hide
    InvalidError , April 12, 2013 6:41 PM
    The problem with light is you need direct line-of-sight for it to even have a CHANCE to work.

    If you replace your ceiling lamp with a LiFi hub, you may be able to flood the room with downstream signal embedded in the floodlight modulation but what about upstream? You probably do not want to have a modulated omnidirectional floodlight for the upstream and once you use directional light sources, your link becomes highly dependent on your transmitter's direction.

    Also, the brighter the ambient light, the lower the SNRM on the modulated signal since most of the dynamic range is consumed by lighting itself, not counting additional noise that may be introduced by pulse-driven LED, CCFL and other light sources.

    It sounds nice in theory but the practical application is not so... practical.
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    canoeguy1 , April 12, 2013 8:54 PM
    A direct link may not be needed for light. Example: If you shine a flashlight at a wall, and turn it on and off, you still see the effect. It's reflecting off the wall. To get more technical, an indirect path may be attenuated by 20 dB vs a direct path, but if the light is strong enough to provide a decent SNR, it's not an issue. The nice thing is, you can send a very strong pulse of light, compared to microwave/RF, without causing harm to people. ie you could easily overcome the 20 dB drop in power by sending a stronger signal.
  • 0 Hide
    smeezekitty , April 12, 2013 9:01 PM
    Of course, but other then to see if it works, what is the benefit over infrared?
  • 0 Hide
    InvalidError , April 12, 2013 11:28 PM
    To get more technical, an indirect path may be attenuated by 20 dB vs a direct path, but if the light is strong enough to provide a decent SNR, it's not an issue.

    20dB attenuation? I think the figure would be over 100dB: your LED's beam will expand to 1m if not more, which already makes it 60+dB weaker, the paint will reflect around 50% of it, only a tiny fraction of that diffused reflection will be going towards the sensor unless the sensor is conveniently located in the normal reflection angle and will likely cover only a tiny percentage of the sensor's field-of-view with the rest contributing to noise input.

    Indirect may work fine on the downstream if the flood light is the one getting modulated for that. For the upstream though, you would likely need to have a sensor network to cover blind spots and divide rooms into multiple sensor zones to reduce the amount of optical noise per zone.

    Can it work? Sure - this is not the first time free-air optical transmissions have been achieved, albeit in fixed point-to-point arrangements. Would it be a practical WiFi replacement? I don't think so. With LiFi, you would need to replace most of your lightbulbs with $?? LiFi lightbulbs, can only use your LiFi mobile devices where LiFi bulbs are installed and need to keep your device's LiFi transceiver location in mind to avoid blocking it. With WiFi, you install a WAP/router anywhere convenient and can use your WiFi devices anywhere within range in any orientation you want.

    Also, WiFi passes through clothes so you can receive your Facebook/Google/Skype/VoIP call/whatever notifications over WiFi while your device is in your pocket/purse/binder/whatever. Can't do that with LiFi no matter how good it may become.
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    ojas , April 13, 2013 3:05 AM
    There was a TED talk about this a very long time ago.
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    BulkZerker , April 13, 2013 1:41 PM
    WOnder how many freq channels this could have
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    kenyee , April 13, 2013 2:03 PM
    Media center! This would be awesome for pushing around 4k video!
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    bak0n , April 14, 2013 10:38 AM
    We had spectrum based fiber on the OC-192 backbone when I worked at Genuity. Not really new tech already the implementation is newer.