Li-Fi: How many light bulbs does it take to change the internet?

So what else might we use to get our day-to-day communication fix? Prof Harald Haas,  Chair of Mobile Communications at the University of Edinburgh, offers an alternative - the 14 billion light bulbs shooting visible light waves all around us every day.

In an IEEE Webinar broadcast in June, Haas reviewed point-to-point communication links using off-the-shelf white light emitting diodes (LEDs). The data density (bits per second per square meter) can be improved by up to a factor of 1300 compared to radio frequency (RF) networks, because of the more favourable interference conditions in optical networks.

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

Of course, we’re already using this visible portion of the electromagnetic spectrum to transmit data. A common example is when you press "Power” on your remote control and its LED sends a data stream that tells the TV to wake up. However, that data stream is far too slow for our modern Internet habits, so Haas proposes we use more LEDs - lots more LEDs.

Haas enables light bulbs to transmit thousands of data streams in parallel through technology dubbed SIM-OFDM (for the curious, it stands for Subcarrier-Index Modulation Orthogonal Frequency-Division Multiplexing) - a kind of multiplexing that 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.

High speeds are achieved by implementing parallel data transmission using arrays of LEDs, where each LED transmits a different data stream. Mixtures of red, green and blue LEDs can be used to alter the light’s frequency, with each frequency encoding a different data channel.

Since then, Haas has continued his research and recently demonstrated the first working prototype of spatial modulation techniques over a wireless RF channel using National Instruments’ PXI RF instruments. With colleagues, he has built a testbed using NI FlexRIO - a software-defined radio platform where they plan to combine LED and spatial modulation technologies to create even higher density optical wireless sensors. This will enable massive Multiple-Input-Multiple-Output (MIMO) technologies for next-generation 5G indoor wireless communications. Say goodbye to long loading times!