Improved signal performance in visible light communications

Professor Harald Haas demonstrating the VLC technology

Visible Light Communication (Li-Fi) offers a new transmission medium for high speed communications. This Edinburgh technology significantly increases the data rate capacity of optical wireless communication, while re-using LED lighting infrastructure as the transmission channel.

Features   Benefits
A method for converting a signal from a bipolar signal into a unipolar signal Increased data exchange rates and lower power usage
Better signal performance and less interference Ability to operate over a broad range of unregulated bandwidth
Applies to any system using intensity modulation with direct detection Future-proofing when protocols are changed and optimised
Low cost front-end devices and existing infrastructure Easy adoption of the technology

Innovation in Wireless Communications

The Challenge

Despite continuous improvements in wireless communication technology, e.g. 3G, LTE, 4G, etc. a looming crisis is anticipated due to a lack of sufficient radio frequency bandwidth to support the growth in demand for data transmission, in the so called “Spectrum Crunch”. Visible Light Communication (Li-Fi) offers an economical solution. LED lighting is now widely deployed, and can in parallel with its primary function, be re-used for wireless communication. Li-Fi demonstrates significant improvements in security, safety and capacity over radio frequency communication, and ease of deployment as compared with fibre-optic cable. The LED link is untethered, enables links with many mobile devices, and is independent of any one host. Improvements to the data rate achievable using LEDs as the transmitter allows services based on LiFi concepts to outperform other communication modes.


This Edinburgh technology has the ability to convert a signal transmitted over an LED based communication link from a bipolar signal into a unipolar signal. By applying a pulse shaping filter to the bipolar signal, and then transforming the negative values of the pulse shaped bipolar signal into a unipolar signal, the net effect is a significant enhancement in data rate transmission. The method can be readily integrated into LED lighting infrastructure, using low cost front end devices to implement a range of Li-Fi applications.

Exemplification Data

Modelling work using the pulse shaping filter technique followed by the transformation of the filter data has shown benefits in Signal to Distortion ratio (SDR) of 12dB.


  • Communications, and in particular those applications where the connectivity between mobile devices and data providers causes bottleneck issues, such as: indoor communications; hospitals; sports arenas; aviation; security/military; underwater.

IP Status

UK priority patent application filed

Development Status

Laboratory prototype


3rd IEEE Workshop on Optical Wireless Communications (OWC'12) pages 1208-12

Commercial Offering

The University of Edinburgh is seeking potential industry licensees for this technology.

Register your interest

If you or your company would like to find out more about this technology opportunity under Confidentiality Agreement with a view to a licence or collaborative research agreement, please complete and submit our technology enquiry form.

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