In recent years, interest in optical wireless (OW) as a promising complementary technology for RF technology has gained new momentum fueled by significant deployments in solid state lighting technology. This article aims at reviewing and summarizing recent advancements in OW communication, with the main focus on indoor deployment scenarios. This includes a discussion of challenges, potential applications, state of the art, and prospects. Related issues covered in this article are duplex transmission, multiple access, MAC protocols, and link capacity improvements.

Recently, visible light communication (VLC) technology has been gaining attention in both academia and industry. This is driven by the progress of white light emitting diode (LED) technology for solid-state lighting (SSL) and the potential of simultaneously using such LEDs for illumination and indoor wireless data transmission. This paper provides an overview about the technology and describes the physical layer implementation of a VLC system based on a modified version of the classical orthogonal frequency division multiplexing (OFDM) modulation technique. Besides, the paper presents a hardware prototype for short-range broadcasting using a white LED lamp. The OFDM system runs on DSP development boards. Off-the-shelf 9 LEDs and a single photodiode (PD) are utilized to build the analog frontends. The prototype allows investigating the influence of the electrical signal-to-noise ratio (SNR), constellation order, and channel coding on the bit-error performance. Theoretical and experimental results on optical path loss show close match. In this context, the influence of the LED beam angle on the horizontal coverage is highlighted.

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In this paper wireless communication using white, high brightness LEDs (light emitting diodes) is considered. In particular, the use of OFDM (orthogonal frequency division multiplexing) for intensity modulation is investigated. The high peak-to-average ratio (PAR) in OFDM is usually considered a disadvantage in radio frequency transmission systems due to non-linearities of the power amplifier. It is demonstrated theoretically and by means of an experimental system that the high PAR in OFDM can be exploited constructively in visible light communication to intensity modulate LEDs. It is shown that the theoretical and the experimental results match very closely, and that it is possible to cover a distance of up to one meter using a single LED

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

Modulating the intensity of light-emitting diodes (LEDs) with analog signals, especially in the case of the bipolar optical orthogonal frequency-division-multiplexing (O-OFDM) signal, leads to significant signal degradation due to LED nonlinearity. The LED transfer function distorts the signal amplitude and forces the lower peaks to be clipped at the LED turn-on voltage. Additionally, the upper peaks are purposely clipped before modulating the LED to avoid chip overheating. The induced distortion can be controlled by optimizing the bias point or backing-off the average O-OFDM signal power. In this letter, a model that incorporates amplitude distortion and that provides a parameterized upper clipping is proposed. Through Monte Carlo simulations, the model can be used to determine the optimum bias point and to optimize the O-OFDM signal power. In this context, a novel concept of soft-clipping of the upper peaks is presented. It is shown that soft-clipping is an effective approach to reduce nonlinearity distortion and to enhance symbol error performance.