![]() Several variants of optical OFDM were proposed to comply with the requirement that the LED driving signal should be non-negative and real valued. To mitigate the effects of intersymbol interference (ISI) over frequency-selective VLC channels, more recent works adopted multicarrier transmission with a particular focus on orthogonal frequency division multiplexing (OFDM), e.g. The multipath characteristics of VLC channel combined with the low-pass natures of LED and front-end limit the available electrical bandwidth. In order to satisfy these conditions, simple modulation techniques such as on–off keying (OOK), pulse place modulation (PPM) and pulse width modulations (PWM) have been studied in earlier works. In IM/DD, the information waveform that modulates the light intensity must be non-negative and real valued. VLC relies on intensity modulation and direct detection (IM/DD) where the information is encoded in the intensity of LED light and then retrieved through a photodetector (PD) at the receiver. Initial works mostly focused on point-to-point links and physical layer development. ![]() In recent years, there has been a surge of research activities in VLC in both academic and industrial circles which has led to a well-established literature on VLC, e.g. VLC can be potentially used as an alternative in safety-critical and hostile environments such as hospitals, airplanes, petrochemical plants, mines, where the use of RF is prohibited or partially restricted. Operating at optical bands with large bandwidth capacity, VLC can be used as a complementary technology where excess capacity demands of cellular or Wi-Fi networks can be offloaded. This allows the use of LED luminaires for wireless communication in addition to their primary function of illumination. VLC is based on the principle of modulating light-emitting diodes (LEDs) at very high speeds that are not noticed by human eye. To release the pressure on the highly congested radiofrequency (RF) spectrum, visible light communication (VLC) has emerged as a complementary and/or alternative wireless access technology. This requires the development of low-cost, energy-efficient and high-speed indoor wireless access solutions. It is estimated that around 70–80% of mobile data traffic takes place in an indoor environment. This article is part of the theme issue ‘Optical wireless communication’. Finally, we consider mobile VLC scenarios and investigate the effect of receiver location and rotation for a mobile indoor user. ![]() ![]() We further present channel models for representative deployment scenarios developed through this approach that were adopted by the Institute of Electrical and Electronics Engineering (IEEE) as reference channel models. Then, we provide a detailed description of a site-specific channel modelling approach based on non-sequential ray tracing that precisely captures the optical propagation characteristics of a given indoor environment. In the light of these, we present a comparative discussion of existing VLC channel modelling studies and point out the relevant advantages and disadvantages. In order to set the background, we start with an overview of infrared (IR) channel modelling, which has received much attention in the past, and highlight the differences between visible and IR optical bands. In this paper, we present a comprehensive survey of indoor VLC channel models. As in any other communication system, realistic channel modelling is a key for VLC system design, analysis and testing. Visible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for wireless communication purposes in addition to their primary purpose of illumination.
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