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

Experimental proof-of-concept of optical spatial modulation OFDM using micro LEDs

This paper investigates experimentally the performance of optical spatial modulation (OSM) with orthogonal frequency division multiplexing (OFDM) in a multiple-input and multiple-output (MIMO) based visible light communication (VLC) system. Gallium nitride based micro light emitting diodes (μLEDs) are considered as a transmitter unit. A two transmitter and two optical receiver based MIMO setup is used. The performance of OSM-OFDM system is experimentally analysed by varying the semi-angle at half power, θ1/2 of the μLEDs. The optical cross-talk in the MIMO channel is quantified and its effect on the achievable data rate and bit error rate (BER) performance is analysed. The experimental results show that OSM-OFDM achieves higher data rates than single-input and single-output (SISO)-OFDM for all the ranges of θ1/2 of the μLEDs under study. However, the BER performance of OSM-OFDM is worse than in the case of SISO-OFDM. The maximum achievable data rate in OSM-OFDM is 1.34 Gb/s and 1.17 Gb/s in SISO-OFDM for θ1/2 of 2.27° at a link distance of 1 m using adaptive data loading. The experimental results also show that due to the strongly correlated channels, the system performance is highly dependent on the θ1/2 of the μLEDs