Visible Light Communications towards 5G

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

Performance Evaluation of Various Training Algorithms for ANN Equalization in Visible Light Communications with an Organic LED

This paper evaluates the effect of training algorithms in an artificial neural network (ANN) equalizer for a feedforward multi-layer perceptron configuration in visible light communication systems using a low bandwidth organic light source. We test the scaled conjugate-gradient, conjugate-gradient backpropagation and Levenberg-Marquardt back propagation (LM) algorithms with 5, 10, 20, 30, and 40 neurons. We show that, LM offers superior bit error rate performance in comparison to other training algorithms based on the mean square error. The training methods can be selected based on the trade-off between complexity and performance

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 Demonstration of Staggered CAP Modulation for Low Bandwidth Red-Emitting Polymer-LED based Visible Light Communications

In this paper we experimentally demonstrate, for the first time, staggered carrier-less amplitude and phase (sCAP) modulation for visible light communication systems based on polymer light-emitting diodes emitting at ~639 nm. The key advantage offered by sCAP in comparison to conventional multiband CAP is its full use of the available spectrum. In this work, we compare sCAP, which utilises four orthogonal filters to generate the signal, with a conventional 4-band multi-CAP system and on-off keying (OOK). We transmit each modulation format with equal energy and present a record un-coded transmission speed of ~6 Mb/s. This represents gains of 25% and 65% over the achievable rate using 4-CAP and OOK, respectively.Comment: 6 pages, 9 figures, IEEE ICC 2019 conferenc

Optoelectronic Modelling, Circuit Design and Modulation for Polymer-Light Emitting Diodes for Visible Light Communication Systems

This paper investigates the use of organic polymer light emitting diodes (PLEDs) for the use in visible light communications (VLC). We prepared blue and green emitting PLEDs using commercial light-emitting polymers, and then characterised the device emission (spectrum and power), and extracted their circuit parameters for their electrical equivalent model for driving with small signals. In addition, we characterised the bandwidth ( Bmod ) of the devices over a period of continuous driving (∼ 4 h) and found that for the blue PLEDs the Bmod decreased from an initial 750 kHz to a steady state of ∼250 kHz. The green-emitting devices were found to benefit from an extended Bmod of ∼1.5 MHz at the beginning of the test, which then stabilised to ∼850 kHz. Furthermore, with the addition of a first order RC filter we show that, the steady state Bmod of the blue PLED cane be increased by a factor of ∼3, thus allowing > 1 Mbps non-return to zero on-off keying (NRZ OOK) data transmission in a complete VLC system

Multifunction LED Lighting System Combining Tunable Spectrum and Data Communication

A comparison of two different lighting systems combining tunable illumination, visible light communications (VLC) and sensing capabilities. The first method is based on light emitting diodes (LED) as light source and multifunction smart sensors and the second one with LEDs and micro-spectrometer to be included in the transceiver and/or receiver. Both systems are intended for future lighting sensor networks that combine standardized optical communications according the standard IEEE802.15.7 and sensing (illuminance, proximity, colour, and spectrum detection) for indoor envirIn this project a novel portable Visible Light Communication (VLC) system comprising an inexpensive and easy to fabricate multi-channel transmitter (Tx) and a receiver (Rx) have been developed. The light engine is designed to support up to three different LED channels while illuminating an indoor space changing the spectrum according to human circadian rhythms or any other desires. The Tx module architecture contains a programmable microcontroller and a constant current LED driver to manage the data to be transmitted. The Rx module allows the detection of optical signals, decoding and recovering the complete information with a circuit containing three stages: transimpedance amplifier, serializer and deserializer stages, controlled by a microcontroller unit. The VLC link has been tested in a laboratory environment with natural illumination to operate for distances up to 8 meters (at 700 kbps), data rates up to 4.50 Mbps (at 2 meters), and angles up to 75º (at 700 kbps and 2 meters). Under these conditions the flickering effect is completely removed

A Flexible OLED based VLC Link with m-CAP Modulation

In recent years there has been a growing interest in using organic light emitting diodes (OLEDs) for illumination in indoor environments. They offer attractive features such as flexibility and large active areas at a low cost; they are energy efficient and have higher illumination levels compared to silicone based LEDs. In addition, the utilization of OLEDs have increased in devices such as smart mobile phones and TVs because of their low thickness. This paper investigates the performance of an OLED based visible light communications (OVLC) system, using a curved and flat OLED with multiband carrierless amplitude and phase (m-CAP) modulation for m = 2 at different angles of incidence on the optical receiver. It is shown that the BER performance is improved (i.e., below the forward error correction (FEC) limit of 3.8×10 −3 ) with the curved OLED when the optical receiver moving along a circular path for the viewing angles greater 40° compared to the flat OLED, which is advantageous in device to device communications

A Flexible OLED based VLC Link with m-CAP Modulation

In recent years there has been a growing interest in using organic light emitting diodes (OLEDs) for illumination in indoor environments. They offer attractive features such as flexibility and large active areas at a low cost; they are energy efficient and have higher illumination levels compared to silicone based LEDs. In addition, the utilization of OLEDs have increased in devices such as smart mobile phones and TVs because of their low thickness. This paper investigates the performance of an OLED based visible light communications (OVLC) system, using a curved and flat OLED with multiband carrierless amplitude and phase (m-CAP) modulation for m = 2 at different angles of incidence on the optical receiver. It is shown that the BER performance is improved (i.e., below the forward error correction (FEC) limit of 3.8×10 −3 ) with the curved OLED when the optical receiver moving along a circular path for the viewing angles greater 40° compared to the flat OLED, which is advantageous in device to device communications

245 MHz bandwidth organic light-emitting diodes used in a gigabit optical wireless data link

Funding: UK EPSRC (EP/K00042X/I, EP/R005281/1, EP/R007101/1 and EP/R035164/1); Marie Skłodowska Curie Individual Fellowship (703387).Organic optoelectronic devices combine high-performance, simple fabrication and distinctive form factors. They are widely integrated in smart devices and wearables as flexible, high pixel density organic light emitting diode (OLED) displays, and may be scaled to large area by roll-to-roll printing for lightweight solar power systems. Exceptionally thin and flexible organic devices may enable future integrated bioelectronics and security features. However, as a result of their low charge mobility, these are generally thought to be slow devices with microsecond response times, thereby limiting their full scope of potential applications. By investigating the factors limiting their bandwidth and overcoming them, we demonstrate here exceptionally fast OLEDs with bandwidths in the hundreds of MHz range. This opens up a wide range of potential applications in spectroscopy, communications, sensing and optical ranging. As an illustration of this, we have demonstrated visible light communication using OLEDs with data rates exceeding 1 gigabit per second.Publisher PDFPeer reviewe