Borovik M.A., Komarova L.V.

Oles Honchar Dnipropetrovsk National University, Ukraine

VISIBLE-LIGHT COMMUNICATION

Nowadays the intensity of the Internet development and its availability conduce to search for more advanced technologies that will help to get the network access regardless your location. Taking into consideration the increase of Internet services consumption, the mentioned possibility should also be affordable. From this perspective, the project which is considered by the mobile communications department at the Edinburgh University seems quite promising.

The Time magazine finds this invention as one of the most significant in the year 2011. A web-based publication of Huffington Post listed ten most interesting innovative ideas, which are worth watching out in 2012. And they note that Li-Fi can dramatically change the way of information transmission. "Our technology allows increasing the density of the transmitted data in thousand times – says Harald Haas, the professor of Edinburgh University. – With its help we cannot transfer data by one flow, just like using radio waves, but like thousands simultaneous ones transmitted in parallel at high speed”.

Among the many new gadgets unveiled at the recent Consumer Electronics Show in Las Vegas was a pair of smartphones able to exchange data using light. These phones, as yet only prototypes from Casio, a Japanese firm, transmit digital signals by varying the intensity of the light given off from their screens. In the age of Wi-Fi and Bluetooth, flashing lights might seem like going back to sending messages with an Aldis lamp. In fact, they are the beginning of the fast and cheap wireless-communication system that was named as Li-Fi.

Last October a number of companies and industry groups formed the Li-Fi Consortium, to promote high-speed optical wireless systems. The idea is that light can help with a looming capacity problem because the radio-based wireless has the limited amount of the available radio spectrum.

Using the light we can break out of this conundrum by exploiting a completely different part of the electromagnetic spectrum.      

Tomorrow’s light-emitting diode (LEDs) is rapidly replacing bulbs and tubes because it is more efficient. And it is a semiconductor device, tinkering with its electronics to produce the flickering signals required for the data transmission. Specially constructed LEDs would be extremely fast. The Li-Fi consortium reckons more than 10 Gbps is possible. In theory, that would allow a high-definition film to be downloaded in 30 seconds.

There are limitations to using light, of course. Unlike radio, light waves will not penetrate walls. Yet for secure applications that could be a bonus. And light bulbs – some 14 billion of them around the world – are almost everywhere and often on. As they are gradually replaced by LEDs, every home, office, public building and even streetlight could become a Li-Fi hotspot. Having a line-of-sight connection with the LED in question would undoubtedly improve the signal, but light reflected from walls or ceilings might often be enough. In any case, having a good line of sight helps Wi-Fi as well. And spotting a nearby light in order to sit next to it is certainly easier than finding the location of a Wi-Fi router.

Communication, though, is a two-way street. That means the LEDs involved in Li-Fi would need photo detectors to receive data. Some LED systems have such sensors already (to know when to turn on at night). But even if LEDs are not modified the hybrid systems are possible: data could be downloaded using light but uploaded (typically a less data-intensive process) using radio. In an office, for example, an LED-powered desk lamp could work as a Li-Fi router, able to link up with any networked device placed on the desk.

A big advantage of light is that it can be used in areas which contain sensitive equipment that radio signals might interfere with, such as aircraft and operating theatres. LEDs in the ceiling of an airliner would not only allow internet access but could also transmit films on demand to individual seats, removing the need for lots of expensive and heavy cabling, thus saving airlines fuel. That alone could be enough to, as it were, make this idea fly.

The scientists believe that that this invention won’t lead to a complete not using the radio waves, but it cam replace the usual range of places where cellular and Internet access can fail or cannot be used: in a crowded stadium, on board of the aircraft, in hospitals and under the water, where radio waves cannot penetrate. And, of course, this method of data transmission is the safest one because of the light zone differs from the radio-based wireless, which is limited by natural barriers and works only in a direct line of sight. This technology is applicable wherever the light is.

Nowadays it is the most environmentally friendly and economical way of data transmission. The team of scientists led by Haas is working on several pilot projects that will use the innovation in everyday life and make it as familiar as cellular and Wi-Fi. The first devices that support Li-Fi should be on the market this year.

Literature:

1. Tripping the light fantastic. A fast and cheap optical version of Wi-Fi is coming. Magazine “The Economist” [Web resource]. – Access mode: http://www.economist.com/ node/21543470

2. В лучшем свете. На смену Wi-Fi приходит новая технология обмена информацией. Журнал «Фокус.ua» [Электронный ресурс]. – Режим доступа: http://focus.ua/ tech/215930