Visible Light Communications towards 5G (original) (raw)

5G networks have to offer extremely high capacity for novel streaming applications. One of the most promising approaches is to embed large numbers of co-operating small cells into the macro-cell coverage area. Alternatively, optical wireless based technologies can be adopted as an alternative physical layer offering higher data rates. Visible light communications (VLC) is an emerging technology for future high capacity communication links (it has been accepted to 5GPP) in the visible range of the electromagnetic spectrum (~370–780 nm) utilizing light-emitting diodes (LEDs) simultaneously provide data transmission and room illumination. A major challenge in VLC is the LED modulation bandwidths, which are limited to a few MHz. However, myriad gigabit speed transmission links have already been demonstrated. Non line-of-sight (NLOS) optical wireless is resistant to blocking by people and obstacles and is capable of adapting its’ throughput according to the current channel state information. Concurrently, organic polymer LEDs (PLEDs) have become the focus of enormous attention for solid-state lighting applications due to their advantages over conventional white LEDs such as ultra-low costs, low heating temperature, mechanical flexibility and large photoactive areas when produced with wet processing methods. This paper discusses development of such VLC links with a view to implementing ubiquitous broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM) or carrier-less amplitude and phase modulation (CAP) in conjunction with equalization techniques. Finally, this paper will also summarize the results of the European project ICT COST IC1101 OPTICWISE (Optical Wireless Communications - An Emerging Technology) dealing VLC and OLEDs towards 5G networks.

LED Based Indoor Visible Light Communications: State of the Art

Visible Light Communication (VLC) is an emerging field in Optical Wireless Communication (OWC) which utilizes the superior modulation bandwidth of Light Emitting Diodes (LEDs) to transmit data. In modern day communication systems, the most popular frequency band is Radio Frequency (RF) mainly due to little interference and good coverage. However, the rapidly dwindling RF spectrum along with increasing wireless network traffic has substantiated the need for greater bandwidth and spectral relief. By combining illumination and communication, VLC provides ubiquitous communication while addressing the shortfalls and limitations of RF communication. This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979-2014. VLC is compared with infrared (IR) and RF systems and the necessity for using this beneficial technology in communication systems is justified. The advantages of LEDs compared to traditional lighting technologies are discussed and comparison is done between different types of LEDs currently available. Modulation schemes and dimming techniques for indoor VLC are discussed in detail. Methods needed to improve VLC system performance such as filtering, equalization, compensation, and beamforming are also presented. The recent progress made by various research groups in this field is discussed along with the possible applications of this technology. Finally, the limitations of VLC as well as the probable future directions are presented.

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Multi-band carrier-less amplitude and phase modulation for bandlimited visible light communications systems

Visible light communications is a technology with enormous potential for a wide range of applications within next generation transmission and broadcasting technologies. VLC offers simultaneous illumination and data communica- tions by intensity modulating the optical power emitted by LEDs operating in the visible range of the electromagnetic spectrum (~370–780 nm). The major challenge in VLC systems to date has been in improving transmission speeds, considering the low bandwidths available with commercial LED devices. Thus, to improve the spectral usage, the research community has increasingly turned to advanced modulation for- mats such as orthogonal frequency-division mul- tiplexing. In this article we introduce a new modulation scheme into the VLC domain; multi- band carrier-less amplitude and phase modula- tion (m-CAP) and describe in detail its performance within the context of bandlimited systems.

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2.7 Mb/s with a 93 kHz White Organic Light Emitting Diode and Real Time ANN Equalizer

2013

This paper presents new experimental results on a 2.7 Mb/s organic light emitting diode (OLED) based visible light communications (VLC) system. We also demonstrate for the first time an online artificial neural network for any VLC system (including inorganics). The major mitigating factors for OLED-VLC systems are the baseline wander phenomenon causing threshold detection to fail and bandwidth limitation caused by low transport mobility, introducing inter-symbol interference into the link and thus the requirement for an equalizer. The online filtering is implemented using the TI TMS320C6713 DSP board and compared with offline results.

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SVM-based detection in visible light communications

A support vector machine (SVM)-based data detection for 8-superposed pulse amplitude modulation and direct-current-biased optical orthogonal frequency division multiplexing in visible light communication is proposed and experimentally demonstrated. In this work, the SVM detector contains multiple binary classifiers with different classification strategies. The separating hyperplane of each SVM is constructed by means of the training data. The experiment results presented that the SVM detection offers improved bit error rate performance compared with the traditional direct decision method.

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SVM Detection for Superposed Pulse Amplitude Modulation in Visible Light Communications

A support vector machine (SVM)-based data detection for 8-superposed pulse amplitude modulation in visible light communication is proposed and experimentally demonstrated. In this work, the SVM detector contains three binary classifiers with different classification strategies. And the separating hyperplane of each SVM is constructed by training data. The experiment results show that the SVM detection offers 35% higher data rates when compared with the traditional direct decision method. Keywords—support vector machine; superposed pulse amplitude modulation; visible light communiction; direct decision.

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Visible Light Communications with Organic Light Emitting Diodes

IEEE Communications Magazine

Organic visible light communications (OVLC) is an emerging subset of visible light communications (VLC) that uses organic photonic components as the link transmitter, receiver or both. Recent developments in organic light emitting diodes (OLEDs) have enabled high efficiency and brightness devices that can be used for data transmission as in conventional VLC systems. VLC utilises the visible wavelength range of the electromagnetic spectrum (370 – 780 nm). Here we demonstrate an OVLC link using an OLED with 93 kHz bandwidth as the source and a silicon photodetector with 5 MHz BW and a 10 dB gain as the receiver. A wide range of modulation schemes are examined and as is commonplace in communications systems; equalization techniques are implemented to maximize data rates into the Mb/s region and 2.7 Mb/s was achieved.

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