Visible Light Communications
New trends in illumination systems are based on the use of LED technology. The development in this area has allowed the existence of lighting devices with better performance in terms of both energy efficiency (luminosity per unit of consumed electric energy unit) and life expectancy, making them a very appealing alternative to be used in new lighting systems or to renovate former lighting deployments based on bulbs, fluorescent tubes/lamps.Capitalizing on these properties, researchers all over the world have started to use LED systems to transmit data, which complements the lighting functionalities of the LED lamps, creating the new paradigm in wireless communications called Visible Light Communications (VLC), which is also usually referred to as Li-Fi (Light Fidelity).
The use of VLC technology presents several advantages. Among them, the following ones can be highlighted: no health regulation to restrict the maximum transmit power (harmless radiation), higher security than radio frequency (RF) systems in terms of eavesdropping, high available bandwidth, unlicensed spectrum usage, power efficiency, no need of high deployment costs, and most importantly the lighting functionality, which eliminates the need for new infrastructure deployment. The potential applications this technology offers are very diverse and most likely VLC will become one of the players of the forthcoming digital ecosystem in the smart cities.
IEEE 802.15.7 VLC standard
The first release of IEEE 802.15.7 standard has been published in September of 2011 and presents rules for the implementation of VLC systems having two main functionalities: illumination and data communications. The standard defines physical (PHY) and media access control (MAC) layer for shortrange optical wireless communications using visible light for indoor and outdoor applications. Special attention is given to problems specific to illumination systems, like flicker mitigation (related with eyesafety regulations) and dimming support (related to power savings and energy efficiency).