Spatially superposed pulse amplitude modulation using a chip-scale CMOS-integrated GaN LED array

We present a highly compact system capable of generating discrete optical wireless data signals from logic inputs, suitable for pulse amplitude modulation (PAM) transmission, in visible light communication (VLC)

Optical Power Domain NOMA for Visible Light Communications

We propose an optical power domain non-orthogonal multiple access (OPD-NOMA) scheme for visible light communications. OPD-NOMA superposes user messages in the optical power domain based on a light-emitting diode (LED) array. The maximum driven current for respective circuits is reduced compared to that of conventional NOMA, in which the LED-array-module is driven by a single circuit. OPD-NOMA reduces the gain and bandwidth requirements for the driver circuit of light source. The nonlinear power-current response of LED largely restricts its usable dynamic range and thus the transmit power. In OPD-NOMA, signals with lower powers suffer from reduced nonlinear distortion. The experimental results show that, OPD-NOMA offers improved transmission performance compared to conventional NOMA using the same driver circuit, since it can make a better use of the linear dynamic range of the LED’s power-current response

Spatial and wavelength division multiplexing for high-speed VLC systems: An overview

White light emitting diodes (LEDs) are becoming the primary source of illumination for the home and office environment. These LEDs can be intensity modulated to transmit high-speed data via an optical carrier. As a result, there is a paradigm shift in indoor wireless communication as the illumination infrastructure can be reused for data communications. It is widely expected that visible light communication (VLC) system will play a significant role in realizing the high-speed data communication envisaged for 5G connectivity. The goal of VLC systems is to provide a reliable and ubiquitous communication link that is an order of magnitude faster than current radio frequency (RF) links. In order to support the high data rates required for the current and future generations of communication systems, a number of techniques were explored for VLC by a number of research groups worldwide. This paper provides an overview of spatial and wavelength division multiplexing that has enabled multi-Gb/s transmission speeds in VLC using low bandwidth LEDs

A review of gallium nitride LEDs for multi-gigabit-per-second visible light data communications

The field of visible light communications (VLC) has gained significant interest over the last decade, in both fibre and free-space embodiments. In fibre systems, the availability of low cost plastic optical fibre (POF) that is compatible with visible data communications has been a key enabler. In free-space applications, the availability of hundreds of THz of the unregulated spectrum makes VLC attractive for wireless communications. This paper provides an overview of the recent developments in VLC systems based on gallium nitride (GaN) light-emitting diodes (LEDs), covering aspects from sources to systems. The state-of-the-art technology enabling bandwidth of GaN LEDs in the range of >400 MHz is explored. Furthermore, advances in key technologies, including advanced modulation, equalisation, and multiplexing that have enabled free-space VLC data rates beyond 10 Gb/s are also outlined