Lighting communications

Light-emitting diode (LED)-based white-lighting is an emerging and booming industry. Over the past few decades, versatile LEDs with visible wavelength ranged from 350 to 750 nm have been widely used as the back lighting source in displays, the lighting component for traffic lights and signs, and the basic element for ubiquitous indoor lighting systems, and so on, because of its high brightness and low power consumption. More than that, the LED-based visible light communication (VLC) system has also been considered as a promising candidate to combine with the white-lighting module for next-generation wireless communication [14], which exhibits distinct benefits of electromagnetic interference (EMI) free and free-space data transmission [5,6] when comparing with the traditional radio frequency (RF) wireless and optical fiber wired communication systems. These excellent features also give rise to the flexibility in lighting and communication applications under different environments, such as in flying aircraft, hospitals, [7] and indoor, and so on, which enables to provide higher data rate than the Bluetooth or Wi-Fi-based wireless network. Note that the flash lamp lighting element in mobile phones can also be employed to transmit data in free space [8]. Pang et al. have already proposed an audio communication system that used LEDs to transmit information to televisions, computers, and phones as early as 1999 [9]. As a future prospect, the schematic diagram of the lighting VLC system with LED-based white-light modules for not only visible lighting but also data transmission is illustrated in Figure 21.1. In such systems, the electrical equipment and components involve the functionalities of transmitting and receiving data within the general illumination area. Furthermore, the optical multiple-input multiple-output (MIMO) technology can be employed further to achieve high data rates [10]. As expected, the indoor lighting VLC (also called Light-fidelity, Li-Fi) system for simultaneous white 646 lighting and data transmission would undoubtedly be the future star for designing and configuring the smart home because of its advantages of license-free, high secrecy, EMI immunity, and luminaire integration compatibility[11-18].