Experimental demonstration of performance-enhanced MIMO-OFDM visible light communications

We experimentally demonstrate individual OCT precoding and SVD-based adaptive loading to boost the capacity of MIMO-OFDM VLC systems. For 1.5-Gbit/s 1-m transmission, the average BER can be reduced from 1.7×10−2 to 4.1×10−3 and 4.7×10−4, respectively

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

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

Real‐Time Software‐Defined Adaptive MIMO Visible Light Communications

Visible light communications (VLC) based on light-emitting diodes (LEDs) merges lighting and data communications in applications of Internet-of-Things and 5G networks. However, phosphor-based white LED has a limited linear dynamic range and limited modulation bandwidth. In practical indoor mobile communications, complex channel conditions change dynamically in real-time, and line of sight (LOS) links may be blocked by obstructions. We propose a real-time software-defined adaptive multi-input multi-output (MIMO) VLC system, that both modulation formats (QPSK,16-QAM,64-QAM, 256QAM) and MIMO reconfigurations (Spatial Diversity and Spatial Multiplexing) are dynamically adapted to the changing channel conditions, for enhancing both link reliability and spectral efficiency. Real-time and software defined digital signal processing (DSP) are implemented by Field Programmable Gate Array (FPGA) based Universal Software Radio Peripheral (USRP) devices. We theoretically analysed and experimentally evaluated nonlinear electrical-optical properties and modulation characteristics of white LEDs. We demonstrated a real-time Single-Carrier 256-Quadrature Amplitude Modulation (QAM) 2×2 MIMO VLC, achieving 1.81% averaged error vector magnitude (EVM), 2×10-5 bit error rate (BER) after 2 m indoor transmission. As an obstacle moved across LOS links, real-time software-defined adaptive MIMO VLC system enhanced average error-free spectral efficiency of 12 b/s/Hz. This will provide high throughputs for robust links in mobile shadowing environments

Mode division multiplexing in radio-over-free-space-optical system incorporating orthogonal frequency division multiplexing and photonic crystal fiber equalization

Radio over free space optics (Ro-FSO) is a revolutionary technology for seamlessly integrating radio and optical networks without expensive optical fiber cabling. RoFSO technology plays a crucial role in supporting broadband connectivity in rural and remote areas where current broadband infrastructure is not feasible due to geographical and economic inconvenience. Although the capacity of Ro-FSO can be increased by mode division multiplexing (MDM), the transmission distance and capacity is still limited by multipath fading and mode coupling losses due to atmospheric turbulences such as light fog, thin fog and heavy fog. The main intention of this thesis is to design MDM system for Ro-FSO for long and short haul communication. Orthogonal frequency division multiplexing (OFDM) is proposed for long haul communication to mitigate multipath fading and Photonic Crystal Fiber (PCF) is proposed for short haul communication to reduce mode coupling losses. The reported results of the proposed scheme for long haul communication show a significant 47% power improvement in deep fades from multipath propagation with the use of OFDM in MDM-Ro-FSO systems as compared to without OFDM. The results of the proposed scheme for short haul communication show 90.6% improvement in power in the dominant mode with the use of PCF in MDM-Ro-FSO as compared to without PCF. The reported results in the thesis show significant improvement in Ro-FSO systems as compared to previous systems in terms of capacity and transmission distance under clear weather conditions as well as under varying levels of fog. The contributions of this thesis are expected to provide seamless broadband services in remote areas

Indoor Visible Light Communication:A Tutorial and Survey

Abstract With the advancement of solid-state devices for lighting, illumination is on the verge of being completely restructured. This revolution comes with numerous advantages and viable opportunities that can transform the world of wireless communications for the better. Solid-state LEDs are rapidly replacing the contemporary incandescent and fluorescent lamps. In addition to their high energy efficiency, LEDs are desirable for their low heat generation, long lifespan, and their capability to switch on and off at an extremely high rate. The ability of switching between different levels of luminous intensity at such a rate has enabled the inception of a new communication technology referred to as visible light communication (VLC). With this technology, the LED lamps are additionally being used for data transmission. This paper provides a tutorial and a survey of VLC in terms of the design, development, and evaluation techniques as well as current challenges and their envisioned solutions. The focus of this paper is mainly directed towards an indoor setup. An overview of VLC, theory of illumination, system receivers, system architecture, and ongoing developments are provided. We further provide some baseline simulation results to give a technical background on the performance of VLC systems. Moreover, we provide the potential of incorporating VLC techniques in the current and upcoming technologies such as fifth-generation (5G), beyond fifth-generation (B5G) wireless communication trends including sixth-generation (6G), and intelligent reflective surfaces (IRSs) among others