EPSRC Grant Awarded
Congratulations to Professor Izzat Darwazeh, Head of UCL Communications and Information Systems Group, who has been awarded a £1.3m EPSRC grant (EP/P006299/1) with Northumbria University to develop reliable state-of-the-art, low-cost, high-capacity wireless technologies to ensure seamless indoor wireless connectivity at all times using Visible Light Communications (VLC), also known as 'LiFi'. Senior Lecturer, Dr Ioannis Papakonstantinou from the department is also a Co-I on the grant, alongside Professor Franco Cacialli from UCL Physics.
With the dramatic increase in traffic carried by telecommunication networks, the demand for wireless resources (spectrum) is quickly outstripping its limited supply. Serious deterioration of service quality due to spectral congestion is becoming evident in high-density user scenarios, where users demand leads to a limited access. This problem is even worse in indoor applications where a lack of spectrum and a large number of users causes significant network slowdown. It is estimated that more than 70% of wireless traffic takes place in an indoor environment (home/office etc.). Thus, there is the need for reliable low-cost, high-capacity wireless technologies to ensure seamless indoor wireless connectivity at all times.
Visible light communications (VLC) offers wireless connectivity using the visible band (~400 THz), which is a license free spectrum with high security and where its sources are used to provide lighting. VLC utilises semiconductor light emitting diodes (LED), which can be modulated at high speeds while providing a constant level of illumination. Traditionally, VLCs use inorganic LEDs as their transmitters' light sources. Such devices introduce significant drawbacks that have yet to be addressed, such as the inability to produce large panels due to the brittle and complex epitaxial processing methods that are expensive. Furthermore, to provide proper illumination, matrices of devices are required, thus introducing a significant circuit complexity. Other drawbacks include the inability to use flexible substrates that are attractive for mobile devices and the difficulties in producing devices with inherent different wavelengths. All of these disadvantages can be dealt with by replacing the commonly used inorganic metals by organic polymers as the semiconductor material of the LEDs. Polymer LEDs (PLEDs) can be manufactured using inexpensive wet processing methods at room temperature (such as inkjet printing) to produce single panel devices with large photoactive areas, at extremely low cost. Further, PLEDs can be deposited on a wide variety of substrate materials and with different shapes, allowing the development of a new generation of devices. Using a simple manufacturing process (one step deposition of different organic polymers) PLEDs may be designed to produce red, green and blue (RGB) light and then combined to allow the dual function of lighting and signal transmission
Over the past decade, the teams applying for this grant have collectively demonstrated major successes in using organic (polymer) LEDs in VLC systems, with manufacturing, cost and operational advantages. Their previous work has led to several "world firsts" in terms of transmitted signal quality and bit rates, and our results were published at leading international journals and conferences.
The research Professor Darwazeh will lead will build on the existing strengths and varied expertise of the UCL team and collaborators at Northumbria. Professor Darwazeh said:
"Specifically our research in inorganic semiconductors, optical component design and fabrication, electronic circuit design and communication systems integration, will be used to construct and demonstrate a new PLED based VLC proof of concept system, which includes novel device, circuit and system designs. We expect to achieve unprecedented VLC transmission speeds in realistic indoor environments. The project will study new methods of designing PLEDs and new optical techniques to maximise their light efficiency. New circuits and communication engineering techniques will be investigated to allow optimised coupling of electronic circuitry to PLEDs, overcoming some of PLEDs inherent data carrying limitations. We aim to assemble a complete system and test in in a specially designed test chambers of VLC. In summary, we believe this work to be highly timely as it addresses the two key challenges; the design of systems operating in license free spectral bands and the provision of easy to manufacture and low cost organic optoelectronic devices."