Li-Fi (Light-Fidelity) is high speed wireless communications through light emitting diodes (LEDs). Li-Fi has first been coined in this TED talk: http://bit.ly/tedvlc. We investigate Li-Fi in the context of novel 5G technologies to solve the looming spectrum crisis in wireless communications. Transmission speeds of up to 9 Gbps have been demonstrated in our lab and it has also been shown that Li-Fi does not required line-of-sight. Therefore, we are now studying wireless system concepts based on Li-Fi technology. We refer to a cellular Li-Fi network as an attocell network as the cell sizes are smaller than in a typical radio frequency (RF) femtocell network potentially unlocking very high area spectral efficiencies. There are a number of PhD projects in this area (If you are interested please send me your CV and transcripts):
Optical Multiuser MIMO
In this project we study optical multiuser MIMO techniques in an optical attocell network. In particular, we exploit the properties that intensity modulation (IM) does not suffer from multipath fading, and that LEDs offer very directional beams. This work will contribute novel algorithms for networked, multiuser Li-Fi systems.
Interference Management in Optical Attocell Networks
This project addresses the issue of co-channel interference in an optical attocell network. The project will develop novel interference cancellation techniques which are tailored to Li-Fi signals. Moreover, the project will study cell cooperation techniques as well as potential interference avoidance techniques taking into account the particular signal propagation characteristics in the visible light and infrared spectrum.
The Internet-of-Things enabled by Li-Fi
Li-Fi uses direct modulation without the need for intermediate frequencies (super-heterodyning) in RF systems. Moreover, it uses inexpensive optical components such as off-the-shelf LEDs and photodetectors. It is, thus, possible to create small, low-complex transceiver units that enable any LED light to act as a high speed data transmitter. Similarly, various low-complexity photodector solutions will be studied. Finally, this work will investigate novel Li-Fi transceiver concepts and study Internet-of-Things and sensor network scenarios based on the proposed transceiver technology.
Li-Fi Spatial Modulation
Spatial modulation is a new digital modulation and MIMO technique which enables highly energy-efficient transmitters as it only requires a single transmitter chain. We explore spatial modulation for Li-Fi transmitters and investigate how SM can be used to support dimming. In addition, we study the impact of various optical components such as polarisers and lenses on the performance of optical spatial modulation.
Novel Digital Modulation Techniques for Li-Fi
Li-Fi uses intensity modulation and direct detection. Therefore, the signals must be strictly real valued and positive. These constraints pose limitation on digital modulation techniques. These limitations result in spectrum-efficiency or power-efficiency losses. This project investigates novel digital modulation techniques for Li-Fi that overcome these limitations. The project will initially compare state-of-the-art techniques such as multicarrier transmission techniques such as orthogonal frequency division multiplexing (OFDM), pulse-amplitude modulation (PAM) and carrier-less amplitude modulation (CAP).
In this project we investigate energy harvesting concepts for Li-Fi systems in combination with energy-efficient transceiver technologies. This requires energy-efficient digital modulation techniques and low computational complexity algorithms. Therefore, investigations of new MAC and synchronisation techniques as well as novel circuit designs are all within the scope of this project. The project primarily targets sensor network applications.