Li-Fi: how you could soon be accessing the internet through your lightbulbs

 

Chinese scientists have reportedly been able to use LED lightbulbs to transmit information to four PCs at speeds of up to 150Mbps. The system uses encoded beams of light to convey data - but it requires a straight line-of-sight to work.

Li-fi, short for "light-fidelity", was developed by Professor Harald Haas at Edinburgh University back in 2011, as an alternative to radio transmissions. It has several advantages over wi-fi - light is much more energy-efficient than radio, and has potentially 10,000 times the bandwidth to transmit information.

Until now, Haas' work had showcased HD video transmission at speeds of up to 10Mbps. Scientists elsewhere - at the Fraunhofer Heinrich Hertz Institute, and a British team led by scientists at the University of Strathclyde - have been able to demonstrate that single-colour LED lights could be capable of speeds as high as 1Gbps. But no-one has come close to technology that's nearly ready for mainstream production, which is what the Chinese researchers at the Shanghai Institute of Technical Physics are now claiming.

The system uses a 1-watt LED bulb equipped with a signal modulation chip that encodes information as a series of light pulses that take place faster than we are capable of perceiving. With a specially-designed receiving station, the PCs were able to connect to the LED bulb. According to Chi Nan, a professor at Shanghai's Fudan University, ten Li-Fi kits will be on display next month at the China International Industry Fair, which begins on November 5.

The technology has a number of pros and cons. As Chi Nan explains, it is more efficient than our existing mobile phone networks: "As for cell phones, millions of base stations have been established around the world to strengthen the signal but most of the energy is consumed on their cooling systems," she explained. "The energy utilization rate is only 5 percent."

Secondly, the number of devices that already use LEDs - including the flashbulbs on mobile phone and tablet cameras - means that in theory, the infrastructure already partly exists for Li-Fi communication. And the speeds could dwarf 4G or current broadband rates, with a 3-colour LED capable of transmitting data at 3Gbps - fast enough to move all the information on a 4.7GB DVD in 12.5 seconds.

The major con is that Li-Fi networks need clear lines of sight between devices to work. "Wherever there is an LED lightbulb, there is an Internet signal," said Chi. "Turn off the light and there is no signal. If the light is blocked, then the signal will be cut off," she added.

One glimmer of good news is that Li-Fi works even if the lights are dimmed to near-darkness. And the inability to pick up signals through buildings or walls could be a bonus for privacy-conscious web users.