Abstract
Visible light communication (VLC) is a promising research topic that aims at utilizing the visible light spectrum for data communication, which in turn off-loads the heavily utilized wireless radio spectrum. VLC can take advantage of the increased use of light emitting diodes (LED) for lighting purposes in different fields, such as automotive headlights, traffic signals, advertising, aviation, and general lighting. Utilizing solid-state LEDs for lighting purposes not only saves energy but also can be used for data communication since LEDs can be easily modulated by switching the light on and off in frequencies above the human eye perception. This data can be transmitted in addition to the main lighting functionality of these devices. VLC is relatively easy to implement and safe, as it does not have potential side effects like the radio signals. As such, this new technology has a great potential for adoption in several applications. This chapter will briefly introduce the technology and discuss some potential indoors and outdoors applications.
TopIntroduction
The initial theory of Visible Light Communication (VLC) was founded in the 1880s when Alexander Graham Bell invented the photo-phone which was used to transmit a voice signal using the modulated sunlight. Since the time of Graham Bell, optical communication research has attracted the interest of scholars around the world and has evolved into a new IEEE standard namely the P802.15.7 - Standard for Short-Range Wireless Optical Communication (standard, 802.15.7 (2015)). In 2003 at the Nakagawa Laboratory in Keio University, Japan, they have proposed using the Light Emitting Diodes (LEDs) for data transmission.
A major factor that contributes to the evolution of VLC technology is the existing infrastructure. Hence, previously installed facilities, such as LED traffic lights or LED sign boards are readily used. Since the transmitters for VLC are light sources, they function for lighting purposes and illuminate the surrounding environment, hence the radiation power and signal-to-noise ratio (SNR) is high; paving the way for a stable communication link (T. Yamazato, I. H. (2014)).
With respect to the emergence of green communication, VLC is highly energy efficient as it utilizes LEDs. The United States Department of Energy further corroborated the importance of LED technology, as shown in Table 1. There is superiority in terms of power consumption and operating lifetime in LED technology as compared to traditional lighting technology, such as incandescent and fluorescent lighting. This clearly shows the potential of the LED lighting technology to replace all the conventional illumination tools as well as serve as a reliable transmitter for a VLC link (Chung, Y.-Y. T.-Y. (2014)).
Table 1. Performance of the conventional and LED lighting technology
| Lamp Type | Watts | Lumens | Operating Lifetime |
| Incandescent | 60 | 900 | 1000 |
| Compact florescent lamp | 15 | 900 | 8500 |
| LED (2011) | 12.5 | 800 | 25000 |
| LED – future(2015) | 5.8 | 800 | 40000 |
Key Terms in this Chapter
Smart Grid: An electrical grid which includes a variety of operational and energy measures including smart meters, smart appliances, renewable energy resources, and energy efficiency resources.
Wireless Communication: Transfer of information between two or more points that are not connected by an electrical conductor.
Signal to Noise Ratio: A ratio of desired signal to undesired signal (noise) in the average power level of a transmission.
OFDM: A method of encoding digital data on multiple carrier frequencies.
Visible Light Communication (VLC): Data communications medium which uses visible light between 400 and 800 THz (780–375 nm).
Intelligent Transportation Systems (ITS): The potential of adding information and smart communications technologies to the transportation infrastructure and vehicles, in order to enhance transportation safety, mobility, and support productivity.
Light-Emitting Diode: A semiconductor device that emits visible light at a single wavelength when an electric current passes through it. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers).
CDMA: A channel access method, which allows several users to share a band of frequencies.