Internet Access Through LED bulb: Li-Fi

Imagine you are standing under a street light to get public internet access, or downloading a HD full movie from the lamp of your desk in  a few seconds, or posting your just clicked snap during a flight. No, I'm not talking about an upcoming Sci-Fi movie. There  is a newborn technology, which could meet the ever-increasing demand for high-speed wireless connectivity. Radio waves are replaced by light waves in a new method of data transmission which is being called Li-Fi.

Genesis

The technology Li-Fi was pioneered by German physicist Harald Haas, currently based at the University of Edinburgh in the UK. Haas coined the term Li-Fi in 2011 in the context of a talk presenting the new technology at the TED (Technology Entertainment and Design) Global conference. The word quickly entered common parlance as an instantly recognizable alternative to WiFi. Both terms are examples of abbreviations linguists sometimes describe as clipped forms, i.e. WiFi = wireless fidelity, Li-Fi = light fidelity. Haas's research project, originally known as D-Light (short for Data Light), is now set to launch a prototype Li-Fi application under the name of newly-formed company VLC (Visible Light Communication) Ltd, which was set up to commercialize the technology. 

Prof. Harald Haas, Edinburgh, Germany

According to researchers led by a team from the University of Strathclyde, it could be possible to combine domestic lighting to also illuminate homes with the technology, which claims to offer high-definition film downloads in under a minute. Professor Martin Dawson, of Strathclyde, who is leading the four-year initiative, said “Imagine an LED array beside a motorway helping to light the road, displaying the latest traffic updates and transmitting internet information wirelessly to passengers’ laptops, netbooks and smartphones. This is the kind of extraordinary, energy-saving parallelism that we believe our pioneering technology could deliver.”

How Li-Fi Works?

Li-Fi is typically implemented using white LED light bulbs at the downlink transmitter. These devices are normally used for illumination only by applying a constant current. However, by fast and subtle variations of the current, the optical output can be made to vary at extremely high speeds. This very property of optical current is used in Li-Fi setup. The operational procedure is very simple-, if the LED is on, you transmit a

digital 1, if it’s off you transmit a 0. The LEDs can be switched on and off very quickly, which gives nice opportunities for transmitting data. Hence all that is required is some LEDs and a controller that code data into those LEDs. All one has to do is to vary the rate at which the LED’s flicker depending upon the data we want to encode. Further enhancements can be made in this method, like using an array of LEDs for parallel data transmission, or using mixtures of red, green and blue LEDs to alter the light’s frequency with each frequency encoding a different data channel. Such advancements promise a theoretical speed of 10 Gbps – meaning one can download a full high-definition film in just 30 seconds.

 A novel modulation technique coined SIM-OFDM was recently proposed. SIM-OFDM uses different frequency carrier states to convey information and leads to increased performance in comparison to conventional OFDM. Additionally, its innovative structure can lead to a decrease of the peak system power, which is highly beneficial in the context of optical wireless communication.

Economic value

• A free band that does not need license.
• High installment cost but very low maintenance cost.
• Cheaper than Wi-Fi.
• Theoretical speed up to 1 GB per second : Less time & energy consumption.
• No more monthly broadband bills.
• Lower electricity costs.
• Longevity of LED bulb : saves money.
• Light doesn't penetrate through walls : secured access.

Limitations

The main problem is that light can't pass through objects, so if the receiver is inadvertently blocked in any way, then the signal will immediately cut out. "If the light signal is blocked, or when you need to use your device to send information -- you can seamlessly switch back over to radio waves", Harald says.

Reliability and network coverage are the major issues to be considered by the companies while providing VLC services. Interferences from external light sources like sun light, normal bulbs; and opaque materials in the path of transmission will cause interruption in the communication. High installation cost of the VLC systems can be complemented by large-scale implementation of VLC though Adopting VLC technology will reduce further operating costs like electricity charges, maintenance charges etc.

Future Prospects

This research report categorizes the global VLC technology market; based on component, applications, and geography. Li-Fi uses light-emitting diodes (LEDs) which are rapidly gaining in popularity for standard lightbulbs and other domestic and commercial purposes. They are expected to be ubiquitous in 20 years. VLC is not in competition with WiFi, Prof. Haas says, it is a complimentary technology that should eventually help free up much needed space within the radio wave spectrum.

"We still need Wi-Fi, we still need radio frequency cellular systems. You can't have a light bulb that provides data to a high-speed moving object or to provide data in a remote area where there are trees and walls and obstacles behind," he says.

some hotspots are:

• the remote control devices under the ocean : radio wave doesn't work there.

• petrochemical plants : radio wave data tranmission is not secured there.

• hospitals : for medical purpose.

• street lights, traffic signals : for traffic update.

• aircraft cabins : for emmegency conversations.

A power point slideshow on this topic provided here.Please give your valuable feedback.