LEDs serve broadband communications - LED Luminaries

Edinburgh start-up Visible Light Communications (VLC) is focussing on using flickering LEDs instead of WiFi for broadband communications, writes David Manners.

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Speeds of up to 500Mbits/sec have been achieved for the technology, called Li-Fi, but the first product from VLC - a consumer transmitter - will deliver data at 100Mbits/sec using VLC's SIM-OFDM technology and optical spatial modulation.. It is due for launch next year.

The technology was invented by Edinburgh University's Harald Haas. "At the heart of this technology is a new generation of high-brightness light-emitting diodes," says Haas, "very simply, if the LED is on, you transmit a digital 1, if it's off you transmit a

High speeds are achieved by implementing parallel data transmission using arrays of LEDs, where each LED transmits a different data stream.

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Also mixtures of red, green and blue LEDs can be used to alter the light's frequency, with each frequency encoding a different data channel.

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Because it uses light rather than radio-frequency signals, VLC could be used in aircraft, integrated into medical devices and hospitals where Wi-Fi is banned, or even underwater, where Wi-Fi doesn't work.

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The snag with LiFi is, of course, that it relies on line of sight.

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VLC's SIM-OFDM technology and optical spatial modulation allows LED light to modulate at a rate so fast as to be imperceptible to the human eye, but which can be picked up by receivers such as suitably configured smart-phone cameras at speeds of hundreds of megabits per second, enabling the light source to transmit data.

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"At the rate we currently adopt wireless data, we will ultimately run out of radio spectrum as we cope with the long term demand of wireless data transmissions and the trillions of bytes of data communicated every month," says VLC CEO Dr Gordon Povey, "turning a light source - a simple household LED bulb for example - into a localised data communications centre is a potentially viable alternative. Where we have an LED light source configured with VLC's own IP, we have a powerful method of carrying data, not just in a single data stream, but thousands of data streams in parallel at high speed."

David Manners

Source: http://www.electronicsweekly.com/blogs/led-lights/2012/03/leds-serve-broadband-communications.html

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