Channel investigation of the underwater visible light communication

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Fekete Gábor
Department of Broadband Infocommunications and Electromagnetic Theory

The main aim of this thesis is to broaden the existing knowledge on the increasingly utilized visible light communication (VLC) method and its less explored use in underwater environments through conducting measurements in order to develop existing methods by improving on them and increasing its data rate.

By conducting open-air and underwater measurements, my research will map the differences of the attenuation, and the material's influences, depending both on distance and wavelength. At this point it becomes important to mention that these measurements will be carried out in an aquarium the size of which is as follows: width: 60 cm, height: 30 cm and depth: 30 cm. As my thesis will show, the effects of reflections in such an environment are not negligible, in fact they exert significant influence over the results of the calculations and the signal.

The open-air analysis will also include presenting the light radiation pattern of the VLC transmitter.

The text will discuss the problems arising from submergence in water, solutions to the waterproofing of the units with the help of underwater casings and the modifications necessary for the application of this method to both the transmitter and the receiver device. As it makes calculations easier, the text will also consider the effects of the aforementioned use of waterproof casings.

My bachelor thesis will place particular emphasis on underwater measurements and the calculations carried out under various types of pollutions, and compare them in order to show that by measuring the attenuation we can also identify and indicate the type of the pollution.

The thesis will also include the findings of my research into the reflections from the surface of the water and the side of the aquarium, e.g. the comparison of the direct route and the reflected level of the light.

Both the open-air and the underwater outputs have fitted curve -- of which my equations are written in the relevant section -- to show the differences of the output level in several material. Furthermore, the text will also introduce some numerical example of attenuations in tables or in diagrams.

These investigations of the VLC link were taken with On-Off Keying (OOK) modulation, the most frequently used modulation in the field of visible optics.

In its last section, the thesis will conclude by mentioning potential instances of future applications, and the possibilities and necessities of further improvement.


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