Visible Light Communication

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Visible light is only a small portion of the electromagnetic spectrum.Visible light communication (VLC) is a data communications medium using visible light between 400 THz (780 nm) and 800 THz (375 nm). Visible light is not injurious to vision.

 

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VLC systems are presently being developed by scientists seeking to create ultra high-speed, high security, biologically friendly communications networks that allow the creation and expansion of seamless computing applications using very large bandwidth high-frequency pulsed light instead of radiowaves and microwaves.

Their use may help provide both partial and full solutions to a number of technological problems: increasingly limited availability of conventional bandwidths for electronic equipment;

VLC appears to be an important potential component in expanding usable bandwidth, protecting sensitive electrical equipment and data, creating more biologically friendly communications technology, and helping develop seamless computing applications.

The Visible Light Communications Consortium (VLCC) which is mainly comprised of Japanese technology companies was founded in November 2003. It promotes usage of visible light for data transmission through public relations and tries to establish consistent standards. The work done by the VLCC is split up among 4 different committees:

1.Research Advancement and Planning Committee

This committee is concerned with all organizational and administrative tasks such as budget management and supervising different working groups. It also researches questions such as intellectual rights in relation to VLC.

2. Technical Committee

The Technical Committee is concerned with technological matters such as data transmission via LEDs and fluorescent lights.

3. Standardization Committee

The standardization committee is concerned with standardization efforts and proposing new suggestions and additions to existing standards.

4. Popularization Committee

The Popularization Committee aims to raise public awareness for VLC as a promising technology with widespread applications. It also conducts market research for that purpose

LED (Light Emitting Diode) VLC technology

LED (Light Emitting Diode) Visible Light Communications (VLC) systems are recognized as creating a possible valuable addition to future generations of technology, which have the potential to utilise light for the purposes of advanced technological communication at ultra high speed surpassing that of current wireless systems. One of the goals of researchers is to allow 100 megabits of data transference per second (Mbps) in offices and homes by modulation of light from upgraded lighting systems.

If it is developed correctly, the possibility exists that many of the problems associated with present day infrared, radiowave and microwave communications systems (and lighting technology) could be at least partially resolved, and a more biologically friendly system made available to industries and the general public.

A further advantage is that VLC systems can transmit data more securely over short distances than radiofrequency/microwave communications devices whose signals can be easily detected outside the rooms and buildings they originate in.

Lighting Types and VLC

At present incandescent and fluorescent lamps are the predominant sources of artificial-lighting, with incandescent units being phased out under a strong drive by many governments worldwide to reduce energy wastage. They are generally being replaced with energy-efficient alternatives, such as fluorescent lights, compact fluorescents and LEDs.

In Visible Light Communication project, the characteristic of short transient time in turning the light on/off processes was further investigated. A high-speed wireless communication system, which is embedded in our LED lighting system, was built. The duplex communication system consists of both downlink and uplink media through different frequencies of lights.Several experiments were conducted in the visible light communication system. In this communication system, off-the-self components were taken part in building the driver circuit and the performance of the system was evaluated, such as, data transmission rate, data transmission distance and the field of view of the transmitter.

With preparations well under way for a societal shift to solid-state lighting based on high-output LEDs, a proverbial light bulb has appeared above the heads of some forward-looking engineers. Their proposal: With enough advance work, every new LED light fixture could also be wired into the network backbone, accomplishing ubiquitous wireless communications to any device in a room without burdening the already crowded radio-frequency bands. Visible light communications (VLC) is being refined by industry, standards groups and well-funded government initiatives. And the stakes are enormous, since the traditional lighting market is measured in trillions of dollars and the transition to solid-state has already begun.

Visible Light Communication uses light emitting diodes (LEDs), for the dual role of illumination and data transmission. Using the visible light spectrum, which is free and less crowded than other frequencies, wireless services can be piggy-backed over existing lighting installations. With this leading edge technology, data including video and audio, internet traffic, etc, can be transmitted at high speeds using LED light.

VLC technology has the potential to deliver data transfer rates in excess of hundreds of megabits per second. Light radiation neither constitutes nor suffers from electromagnetic interference (EMI) making VLC a very attractive technology in places/environments where electromagnetic interference (EMI) is an issue, such as in hospitals and in aircraft. In addition, where security of local communication is important eg defence and finance applications, D-Light technology offer a secure medium for communication in an office/building environment.

 

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VLC Applications:

A wide range of applications would benefit from using novel visible light communications:

Wi-Fi Spectrum Relief – Providing additional bandwidth in environments where licensed and/or unlicensed communication bands are congested

Smart Home Network – Enabling smart domestic/industrial lighting; home wireless communication including media streaming and internet access

Commercial Aviation – Enabling wireless data communications such as in-flight entertainment and personal communications

Hazardous Environments- Enabling data communications in environments where RF is potentially dangerous, such as oil & gas, petrochemicals and mining

Hospital and Healthcare – Enabling mobility and data communications in hospitals

Defence and Military Applications – Enabling high data rate wireless communications within military vehicles and aircraft

Corporate and Organisational Security – Enabling the use of wireless networks in applications where (WiFi) presents a security risk

Underwater Communications – Enabling communications between divers and/or remote operated vehicles

Location-Based Services – Enabling navigation and tracking inside buildings.

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Biologically friendly Visible Light Communication technology

Most wireless communications today are based on various radio frequency waves generated, transmitted and received by electronic devices. WI-FI, 3G and Bluetooth are examples of this most wide technology. Radio frequency based  systems are suffering from increasingly limited availability of conventional bandwidths for electronic equipment. Even the fastest of these radio frequency data transmission networks cannot compete with the potential of superior communication attributes provided by visible light transmission at higher speeds. The fastest networks today are equipped with lasers, fiber optic cabling network appliances and adaptive equipment. The next generation of wireless networks 4G will be using light as its transmission medium with the potential to deliver data transfer rates in excess of hundreds of megabits per second.

Light radiation neither constitutes nor suffers from electromagnetic interference making visible light modulation a very attractive technology in environments where electromagnetic interference is an issue, such as in hospitals and ambulance vehicles. It ensures increased safety avoiding interference with GPS navigation systems on board of marine vessels and aircraft..

Future of the wireless communications require biologically friendly communications networks capable to provide less harmful electromagnetic environment. Currently used communication signals in the microwave spectrum in many cases may lead to negative health consequences, when humans are  exposed to raised radio frequency and microwave levels.Visible Light Communication systems are presently being developed by all major tele communication companies, government agencies and scientific research institutions. The Institute of Electrical and Electronics Engineers IEEE Wireless Personal Area Networks working group worked out the unified standard proposal for Visible Light Communication technologies. The integration of the new systems promises to be seamless as they use modulated light wavelengths in the visible spectrum emitted and received by a variety of suitably adapted and widely used sources of light.

Commonly used devices such as indoor and outdoor lighting, car lights, displays, illuminated signs, televisions, computer screens, digital cameras and mobile phones which have light emitting diodes used for new type of communications. Biologically friendly light modulation system provide basic networking capabilities in offices and homes, by upgrading lighting systems incorporated into home and outdoor networks.use of light modulation provide solutions to a number of biological and technological problems avoiding negative health consequences, as well as communications interference with sensitive electrical equipment.

Car makers are working on incorporating the visible light modulation principles in the optoelectronic spectrum for car and driver increased safety. Car lights with light emitting diodes may be using infrared and visible light frequencies to transmit signals between cars. Just like the brake lights send a message to the driver to stop, the modulated signals of emitting and receiving light diodes establish the photonic communication channel to send information to the VLC aware vehicle onboard control system which interacts with the driver and braking system to help avoid collision.

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