Look around your house, and tell us one thing you find common in almost all your electronic and electrical equipment? The Internet Connection. Right! What if we say just like your mobile networks and Wi-Fi routers, we can also use those LED lights for communication! Don’t believe me? Well, it is an amazing technique!
We could just say that there is one more category of communication added to the list of types of communication. To be precise a division in the Optical Wireless Communication Category. This includes all types of optical communication where optical cables are not used.
Data transfer or communication using LED lights is called Visible Light Communication. When we talk about VLC, it is referred to as the illumination source which is used to send data by switching on off the light at a great speed which could not be detected by normal eyes but photo detectors could detect that.
VLC = Illumination + Communication
The other similar terms to VLC are
- Free Space Optical Communication – This method of communication is also similar to VLC but is not restricted to visible light. So, ultraviolet and infrared also fall into the FSO category. Additionally there is no illumination requirement for FSO and so this tends to be used in narrow beams of focused light for applications such as communication links between buildings.
- Li-Fi – It is a term used describe high speed VLC in application scenarios where Wi-Fi night also be used. Li-Fi communication is similar to Wi-Fi communication with a difference that Li-Fi uses visible light for transmission whereas Wi-Fi uses radio waves for transmission.
LiFi is short form of Light Fidelity. It is a Visible Light Communications (VLC) system that is a wireless optical networking technology which uses light-emitting diodes for data transmission.
LiFi is designed to use LED light bulbs similar to those energy efficient lights we use in our homes and offices. These LED light bulbs not just help in the data transfer but also boost the speed up to 224 gigabits per second.
Imagine a flash light which you might use to send a Morse code signal. When operated manually this is sending data using the light signal, but because it is flashing off and on it cannot be considered to be a useful illumination source. Now imagine that the flash light is switched on and off extremely quickly via a computer, then we cannot see the data and the flash light appears to emitting a constant light, so now we have illumination and communication and this does fits our definition of VLC.
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The working of this system is very simple. The transmission is done just by switching on and off the LED lights in a pattern to define the data. This quick switching is imperceptible to the human eyes.
A simple Li-FI or VLC system has two qualifying components:
- At least one device with a photodiode able to receive light signals
- A light source equipped with a signal processing unit.
Consider a normal light bulb, when a constant current is applied to it, a constant stream of photons are emitted from the bulb which is observed as visible light. If the current is varied slowly the output intensity of the light dims up and down. LED bulbs are semi-conductor devices, the current, and hence the optical output, can be modulated at extremely high speeds which can be detected by a photo-detector device and converted back to electrical current.
In all the communication technologies, the information is converted into the binary data string of 1’s and 0’s. This string can be coded in the form of on and off signals. 1 will be represented as ON signal of light and 0 will be represented as OFF signal of light. At the receiver’s end the flickering of the light is interpreted as 1’s and 0’s.
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WiFi versus LiFi
We can compare Li-Fi to Wi-Fi, as both transmit data electromagnetically with a difference that Wi-Fi uses radio waves giving it a slower data rate while Li-Fi runs on visible light which offers much faster data transfer rate. Interference of the signal from nearby access points has been a major challenge in the Wi-Fi Transmission, whereas Li-Fi systems do not have any such shortcomings.
Radio frequency communication requires radio circuits, antenna and complex receivers, whereas Li-Fi is much simpler and uses direct modulation methods similar to those in low-cost infra-red communication devices such as remote control units.
Li-Fi being compatible with IrDa devices and having no problem of interference could be used in a variety of environments such as airlines and sea exploration. On the other hand Wi-Fi is compatible with only 802.11 devices is mainly used for internet browsing and to create hotspots.
Some of the major advantages of the Li-Fi technology which is not presented by Wi-Fi are
- It could transmit in dense regions and in the salt water.
- The signals in this system cannot pass through walls, so data is more secure and protected.
- Visible light is far denser than radio waves, which makes it capable of transferring large amount of data.
- The highest recorded speed of Li-Fi system is 10Gbit/second.
- Efficiency – The technology works in the visible light spectrum. Since offices and homes already have the LED bulbs so, they could be used for dual purposes. Hence making it efficient in terms of cost and energy.
- Availability – The best advantage of the technology is that it could be present in all places that has light and LED bulbs. That means homes, planes, offices, shops, and malls, every place can have high-speed data transmission.
- Security – Security the biggest advantage of the Li-Fi technology as the visible signals cannot penetrate the opaque objects. As a result, accessibility of Li-Fi is limited to a single room.
No technology is perfect by itself. Each has its own set of limitations or shortcomings. Li-Fi technology is no exception. Despite of all the benefits in terms of security and speed, Li-Fi technology do have some challenges to face as below:
- Line Of Sight – This is a definite advantage as the signal will be longer. But at the same it poses a limitation in terms of coverage distance as signals are reflected from the objects in our daily life.
- Multipath Distortion – This distortion is caused due to the delay in receiving the signal at the destination from the transceivers as each path has different length from source to destination. This creates a problem of Inter Symbol Interference.
- Simplex Communication – VLC gives best result when used for one-way transmission. Though there are many ways to isolate the uplink and downlink by dividing the wavelengths, time, and having different codes, but due to high cost VLC is seemed to be thought best for downlink implementation.
- Lights On – for the VLC systems to work, the lights need to be on for all of the time. In case of commercial and industrial area the lights are on whenever they are occupied. In case of domestic areas the lights are used only for illumination and are off for maximum of the day.
- Transmitter Sources – LED lights are being manufactured only for illumination purpose only. Communication application is not even in the secondary list of plans. In a practical sense excellent results can be achieved with cost LED devices.
Li-Fi is an amazing technology. It’s also in its early days. It is a hard to predict the future growth of technology at this early stage, but it is safe to say that a combination of Li-Fi and Wi-Fi will bring the best of both worlds to the internet.