11-02-2015, 12:08 AM
seminar report on visible light communications
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seminar report on visible light communication doc file
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seminar report on visible light communications
15-03-2017, 02:44 PM
Visible light communication (VLC) is a variant of data communications that uses visible light between 400 and 800 THz (780-375 nm). VLC is a subset of optical wireless communications technologies. The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit / s, or LEDs up to 500 Mbit / s. Low-speed [vague] data transmissions were demonstrated at 1 and 2 kilometers (0.6 and 1.2 mi). RONJA achieves full Ethernet speed (10 Mbit / s) at the same distance thanks to a larger optic and more powerful LEDs.
Especially designed electronic devices generally containing a photodiode receive signals from light sources, although in some cases a cell phone camera or digital camera will suffice. The image sensor used in these devices is in fact a set of photodiodes (pixels) and in some their use may be preferred over a single photodiode. Such a sensor can provide multichannel communication (up to 1 pixel = 1 channel) or spatial awareness of multiple light sources.
VLC can be used as a means of communication for ubiquitous computing, since light production devices (such as indoor / outdoor lamps, televisions, traffic signs, commercial displays and rear lights / headlamps) are used everywhere. The use of visible light is also less dangerous for high power applications because humans can perceive it and act to protect their eyes from damage.
Light-emitting diodes are set to penetrate into many areas of everyday life. An interesting property of these devices, in addition to their lighting capabilities, is that they can also be used for data transmissions as well. LEDs require low power for operation and have very high switching speeds. This dual-purpose application can reduce our dependence on the densely-utilized media of radiofrequency communication. The project aims to construct a system that realizes the communication using the visible light that are used for the illuminations of interior. The increased bandwidth of visible light is exploited for high-speed data transmissions. For communication to be full-duplex, downlink and uplink are required. The downlink is implemented using visible light. While the uplink is provided by infrared LEDs, since the visible light will not serve to illuminate. In addition, the IR link also eliminates the possibility of interference. When communication is done through visible light there are problems associated with it. The data transmission speeds must be high enough so that the LED blinking is not detected. Sometimes complete fading of the signals is possible. To protect the integrity of the data, the data must be framed to detect lost signals and ensure correct transmission and reception of the data. Computer network protocols such as stop and wait algorithms are employed to solve this problem. The data can be of any form, like text, audio, image or video. This project shows how visible light can be used to transfer text data from one computer to another. The equipments are used as the final device.
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