| Summary |
Visible light communications (VLC) is the latest optical wireless communications technologies that uses low-power light emitting diodes, or LEDs, not only to provide light but also to broadcast data. LEDs are extremely energy-efficient and predicted to become widespread in general lighting application. It is expected that LED market will reach $29 billion in 2017 that is comparable to today's NAND and DRAM markets [1]. Because LED is a solid-state lighting device, it can be modulated at high-speed compared with other lighting sources. VLC uses LEDs, which send data by flashing light at speeds undetectable to the human eye.
The pioneer of VLC using LEDs is Professor Masao Nakagawa of Keio University. His first paper on this subject appeared in the early 2000, together with his successor Prof. Shinichiro Haruyama, the instructor of this tutorial. Later in 2003, he formed Visible Light Communication Consortium (VLCC). Now VLCC is lead by Prof. Haruyama. Please see the following video, an interview of Prof. Haruyama about VLC, which has been broadcast by NHK World in June 4, 2009. http://www.naka-lab.jp/movie/nhk_world.wmv
So far various experimental VLC systems and prototypes are demonstrated. Such includes 4.8kbps visible light ID as an infrastructure to mobile-terminal application, independent sound transmission through RGB visible lights and 100Mbps VLC wireless LAN system. Using LED array, the data rate of 1 Gbps achieved by Keio University (Prof. Haruyama) that is the fastest at the moment [1]. In terms of longer range, there has been a demonstration by VLCC that achieved 1kbps transmission of the distance 2km, that is the world's longest distance for VLC. Samsung and ETRI are also active in developing VLC applications. They have demonstrated 120Mbps full duplex mobile-to-mobile transmission and 100Mbps signboard transmission. Please see the following video of Nakagawa lab. http://www.youtube.com/watch?v=QEh5f49LsB4
Widespread use of LEDs in traffic applications and growing interest in Intelligent Transport System (ITS) presents an opportunity for VLC. Data transmission using LED traffic lights, LED road illumination, and LED brake lights are typical application. Dr. Yamazato, the instructor of this tutorial, is a leader in VLC application to ITS and he recently achieved 16kbps data transmission and distance up to 70m in a driving situation with a vehicle moving with 30km/h. Today VLC using LED is a hot topic and VLC projects have been initiated in Europe and US. In 2006 Siemens launched VLC project. Later in 2008, European Commission established OMEGA project with a consortium of 20 European partners from industry and the scientific community [3]. Meanwhile, in 2008, the US National Science Foundation has approved a grant of $18.5 million to help establish and the Engineering Research Center focuses on VLC. The members of the Center include the Rensselaer Polytechnic Institute in New York, Boston University and the University of New Mexico. The University of California also have launched five-year research project called the Ubiquitous Communication by Light (UC-Light) that is founded with $3.5 million from the University. The project is anticipated to begin in 2009 and run for five years.
VLC is in the process of standardization by the IEEE 802.15 TG7 and VLCC as well as other standard organizations. The first VLC specification standard was released from JEITA in conjunction with VLCC in 2007. Later in 2008, VLCC released their first specification standard adopting and expanding the IrDA physical layer. IrDA transceiver transmission wavelength (IrDA physical layer) is expanded to accommodate the visible light wavelength. By adapting this specification, the existing IrDA optical modules can be used for VLCC data transmission with slight modification. In January 2009, IEEE 802.15 (Wireless Personal Area Networks) Task Group 7 (Visible Light Communication) has been launched. At the 6th meeting held in November 2009 they adopted the baseline draft text for the development of the 802.15.7 standard.
The goal of this tutorial is to introduce current VLC technology and its trends. Starting with an overview of VLC, participants will learn basics of VLC, on-going standardization activities and VLC. We will provide some experimental results and furthermore detail to enhance VLC application.
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