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Sunday, December 23, 2018


Transferring data from one place to another is one of the most important day-to-day activities. The current wireless networks that connect us to the internet are very slow when multiple devices are connected. As the number of devices that access the internet increases, the fixed bandwidth available makes it more and more difficult to enjoy high data rates and connect to a secure network. Nowadays, everyone is interested in using his mobile phone, laptop to communicate with other people through Wireless-Fidelity (Wi-Fi) systems but the capacity is going down due to the limitation of Radio Frequency (RF) resources. In order to overcome this problem in the future, Professor Harald Haas, an expert in optical wireless communications, proposes in 2011 a brilliant and applicable solution by using light to transmit data, he demonstrated how a Light-Emitting Diode (LED) bulb equipped with signal processing technology could stream a high-definition video to a computer and he showed that one watt LED light bulb would be enough to provide network connectivity to four computers. This new technology is known as Light–Fidelity (Li-Fi).

What is LI-FI?
It is a short-range wireless communication system based on light illumination from the LED, and use the visible light as a signal carrier instead of traditional RF carrier as in Wi-Fi. Professor Harald Haas coined the term "Light-Fidelity" and set up a private company, called “Pure Visible Light Communication”, to exploit that technology. He envisions a future where data for laptops and smartphones are transmitted through the light in a room in a secure way.
Li-Fi technology is implemented using white LED light bulbs used for illumination by applying a constant current. However, by fast variations of the current, the light output can be made to vary at extremely high speeds. If the LED is on, it transmits a digital 1 otherwise it transmits a digital 0. The LEDs can be switched on and off quickly to transmit data that can’t be detected by a human eye. The LED bulb will hold a microchip that will do the job of processing the data. The light intensity can be manipulated to send data by tiny changes in amplitude.

Figure 1
Figure 1 shows the working principle of Li-Fi system, for data transmission, it can be done by a single LED or multi-LED. On the receiver side, there is a photodetector, which converts this light into electric signals and it will give the electric signals to the device connected to it. Voltage regulator and level shifter circuits are used on both sides to convert or maintain a voltage level between transmitter and receiver

The dramatic growth in the usage of LEDs for lighting provides the opportunity to incorporate Li-Fi technology into a plethora of LED environments, for instance, any lighting devices like car lights, ceiling lights, and street lamps are used as a hotspot which helps us to lower cost architecture for a hotspot.
This technology is particularly suitable for many popular internet applications; you can download movies, games, and music in just a few minutes with the help of Li-Fi.

Figure 2
Figure 2 shows the environment with the Li-Fi technology where light bulbs are used as a data communication medium to PC, Laptop and Tablet as it all have photodetector connected to it as a receiver.

Apart from many advantages over Li-Fi, this technology is facing some problems such as Li-Fi requires line of sight (LOS) and receiving device would not be a shift in indoors. A major challenge is how the receiving device will transmit data back to the transmitter. Another important issue is interference from external light sources like sunlight, normal bulbs, opaque materials in the path of transmission will cause an interruption in the communication. Another disadvantage is that Li-Fi doesn’t work in the dark or light can’t pass through objects, so if the receiver is inadvertently blocked in any way, then the signal will immediately cut out. And the signal is easily blocked by somebody simply walking in front of the LED source.

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