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Key facts

  • VLC uses rapid flickering of advanced LEDs to encode and transmit data
  • The technique doesn’t interfere with radio-frequency electronics
  • VLC has great potential for vehicle-to-vehicle communication
  • It is harder to intercept than RF signals, so could suit military applications

A wireless system that uses flickering LEDs to encode and transmit data could open up new paths of communication for hospitals, vehicles and defence.

German engineers are working on the development of a wireless data transfer system that could enable video to be encoded and transmitted in the form of flickering light. Their work represents one of the latest developments in the emerging field of visible light communications (VLC), which uses the rapid flickering of advanced light-emitting diodes (LEDs) to encode and transmit data.

The group, from the Fraunhofer Heinrich Hertz Institute (HHI) for telecommunications in Berlin, used regular LEDs to form the basis of an optical WLAN system able to send high-definition quality videos to phones and laptops.

Presenting the results of the project earlier this year, the team was able to transfer data at a rate of 100 megabits per second (Mbit/sec) without any losses, using LEDs in the ceiling that light up more than 10m² (90ft²). A receiver can be placed anywhere within this radius, which is currently the maximum range.

More recently, the team, which has been working closely with Siemens and France Telecom Orange labs, has further improved the system’s data transfer rates.

’Using red-blue-green-white light LEDs, we were able to transmit 800Mbit/sec in the lab. That is a world record for the VLC method,’ said project leader Klaus-Dieter Langer.

’For VLC the sources of light in this case, white-light LEDs provide lighting for the room at the same time they transfer information,’ explained Langer.

’With the aid of a special component, the modulator, we turn the LEDs off and on in very rapid succession and transfer the information as ones and zeros. The modulation of the light is imperceptible to the human eye. A simple photo diode on the laptop acts as a receiver.’

While VLC is not currently considered a direct replacement for regular WLAN, PowerLAN or UMTS, the German team believes that it could be a useful additional option for data transfer where radio transmission networks are not desired or not possible.

Indeed, as previously reported in The Engineer, VLC is thought to have great potential across a range of applications. Because it doesn’t interfere with radio-frequency electronics, it is thought to be particularly suitable for use in hospitals, aircraft and vehicle-to-vehicle communications.

Researchers around the world are particularly excited about its potential in car-to-car communications, where VLC-enabled car headlights could communicate with the tail-lights of other vehicles and potentially form the basis of advanced collision-avoidance systems.

What’s more, because VLC is far harder to intercept than RF signals, it’s also thought to have potential in defence applications. It could, for instance, be used to help securely pass information between convoys of tanks and other military vehicles.

Elsewhere, engineers at Niigata University in Japan are looking at using the technology to develop a positioning system that gets data from light fixtures.

Liu Xiaohan, who is helping to develop the system, believes it could be used in applications such as guiding visually impaired people through hospital hallways. ’If we use LED and image sensors as the receiver, we can reach an accuracy of less than 5cm,’ he said. ’It is far more accurate than other location technologies, but the biggest problem is cost.’

While the Fraunhofer team is helping to take the technology a step closer to commercialisation, there are many other groups around the world working in this emerging field.

The work has been pioneered in Japan by the Visible Light Communications Consortium (VLCC), while the US has invested $18.5m (£11.5m) in the development of VLC and the Chinese government is also thought to have put aside large sums to integrate it into aircraft.

Wireless system uses flickering LEDs to encode and transmit data

Key facts

  • VLC uses rapid flickering of advanced LEDs to encode and transmit data
  • The technique doesn’t interfere with radio-frequency electronics
  • VLC has great potential for vehicle-to-vehicle communication
  • It is harder to intercept than RF signals, so could suit military applications

A wireless system that uses flickering LEDs to encode and transmit data could open up new paths of communication for hospitals, vehicles and defence.

German engineers are working on the development of a wireless data transfer system that could enable video to be encoded and transmitted in the form of flickering light. Their work represents one of the latest developments in the emerging field of visible light communications (VLC), which uses the rapid flickering of advanced light-emitting diodes (LEDs) to encode and transmit data.

The group, from the Fraunhofer Heinrich Hertz Institute (HHI) for telecommunications in Berlin, used regular LEDs to form the basis of an optical WLAN system able to send high-definition quality videos to phones and laptops.

Presenting the results of the project earlier this year, the team was able to transfer data at a rate of 100 megabits per second (Mbit/sec) without any losses, using LEDs in the ceiling that light up more than 10m² (90ft²). A receiver can be placed anywhere within this radius, which is currently the maximum range.

More recently, the team, which has been working closely with Siemens and France Telecom Orange labs, has further improved the system’s data transfer rates.

’Using red-blue-green-white light LEDs, we were able to transmit 800Mbit/sec in the lab. That is a world record for the VLC method,’ said project leader Klaus-Dieter Langer.

’For VLC the sources of light in this case, white-light LEDs provide lighting for the room at the same time they transfer information,’ explained Langer.

’With the aid of a special component, the modulator, we turn the LEDs off and on in very rapid succession and transfer the information as ones and zeros. The modulation of the light is imperceptible to the human eye. A simple photo diode on the laptop acts as a receiver.’

While VLC is not currently considered a direct replacement for regular WLAN, PowerLAN or UMTS, the German team believes that it could be a useful additional option for data transfer where radio transmission networks are not desired or not possible.

Indeed, as previously reported in The Engineer, VLC is thought to have great potential across a range of applications. Because it doesn’t interfere with radio-frequency electronics, it is thought to be particularly suitable for use in hospitals, aircraft and vehicle-to-vehicle communications.

Researchers around the world are particularly excited about its potential in car-to-car communications, where VLC-enabled car headlights could communicate with the tail-lights of other vehicles and potentially form the basis of advanced collision-avoidance systems.

What’s more, because VLC is far harder to intercept than RF signals, it’s also thought to have potential in defence applications. It could, for instance, be used to help securely pass information between convoys of tanks and other military vehicles.

Elsewhere, engineers at Niigata University in Japan are looking at using the technology to develop a positioning system that gets data from light fixtures.

Liu Xiaohan, who is helping to develop the system, believes it could be used in applications such as guiding visually impaired people through hospital hallways. ’If we use LED and image sensors as the receiver, we can reach an accuracy of less than 5cm,’ he said. ’It is far more accurate than other location technologies, but the biggest problem is cost.’

While the Fraunhofer team is helping to take the technology a step closer to commercialisation, there are many other groups around the world working in this emerging field.

The work has been pioneered in Japan by the Visible Light Communications Consortium (VLCC), while the US has invested $18.5m (£11.5m) in the development of VLC and the Chinese government is also thought to have put aside large sums to integrate it into aircraft.

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