LI-FI : PROBLEMS OF WIRELESS COMMUNICATION SYSTEMS

 PROBLEMS OF WIRELESS COMMUNICATION SYSTEMS

 What is the Problem?

Despite continuous improvements in wireless communication systems, e.g. 3G, 4G, etc.., a coming crisis is expected due to the lack of sufficient Radio Frequency (RF) resources, this limitation in bandwidth cannot support the growth in demand for high data rates and the large numbers of communication systems ,within the bandwidths between 300 kHz and 4 GHz. That is known as “Spectrum Crunch”.

Although , spectrum congestion decreases when we use high frequencies to transfer data, but this not a practice solution, because this part of spectrum requires complex equipment and causes high cost systems.

So how can we solve this problem?

Actually, there are numbers of technologies that provide realistic and applicable solutions to this issue. One of them is the “Cognitive Radio”. It is a new sort of wireless communication with a transceiver architecture that can intelligently detect which communication channels are in use and which are not, and instantly move into empty channels to use them to transmit data. Another solution is the transmission of data using visible light illumination which use very high frequency. In general , this technology known as Visible Light Communication (VLC).

There are also many brilliant and efficient solutions, in this seminar we will focus on Light Fidelity (Li-Fi) technology, which is based on VLC .

 Visible Light Communication

Definition

VLC is an optical communication technology that use visible light rays, these rays locate between  [400-800] THz, as optical carrier for data transmission by illumination. It uses fast pulses of light, which cannot be detected by the human eye, to transmit data. It includes any use of the visible light portion of the electromagnetic spectrum to transmit information. The VLC standardization process is conducted within IEEE wireless personal area networks working group (802.15).

One of VLC’s features is providing wide bandwidth as illustrated. We can obviously see that usage the optical portion of spectrum guarantees about 10,000 times greater bandwidth compares to the usage of the RF frequencies.

Components

As we see in the previous paragraph, VLC is a communication system which consists of a transmitter, a receiver and a communication channel. The main components of VLC systems are:

 High brightness Light-Emitting Diodes (LEDs) or any light sources, which acts as transmitter.

 A silicon photodiode has the roll of a detector and it shows a good response to visible wavelength.

 Communication channel is air or fiber optics.

Usually, we add to these components some necessary circuits like a driving circuit and a receiving circuit. The driving circuit consists of a control circuit and output stage to modify the data and make it ready to be sent and the receiving circuit consists of a filter to select the required band, amplification stage to provide the required Signal to Noise ratio in order to demodulate the signal.

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