With the increasing development of technology and the diverse applications of cameras, particularly in Internet of Things (IoT) systems, their use as receivers in underwater optical wireless communication (UOWC) systems has received increasing attention. The unique capabilities of cameras, such as simultaneous imaging and visual information processing, open up new possibilities in underwater communication. However, the lack of a comprehensive and accurate model for these systems, coupled with the absence of investigation into key performance parameters, poses significant obstacles to their development and implementation. In this thesis, conducting comprehensive and accurate research on modeling and analyzing underwater optical camera communication (UOCC) systems is of great importance. This research aims to address these gaps and provide a complete model for eva‎luating the performance of these systems. In this study, the impact of the channel on the performance of the UOCC system is investigated. Challenges arising from absorption and scattering, and their effects on system performance, are eva‎luated. First, a comprehensive model for the system is presented, and then, using data from experimental tests, the accuracy of the model is validated. The system's performance is examined by considering various parameters, including channel length, distance between light-emitting diodes (LEDs), angle between transmitter and receiver, LED diameter (D), and transmitter wavelength. Given the wavelength dependence of channel absorption and scattering coefficients, selecting the appropriate wavelength is crucial. This importance is increased in color modulation and wavelength division multiplexing (WDM) systems that employ color filters and digital image processing. The results indicate that in clear and coastal waters, green, blue, and red colors perform better, respectively, whereas in harbor waters, red color, due to its longer wavelength and consequent lower scattering coefficient, outperforms green and blue. Furthermore, inappropriate selection of transmitted power and camera exposure time can lead to pixel saturation or increased noise impact on system performance. The LED half-power angle is also critical in systems requiring transmitter or receiver mobility. The model presented in this study enables the analysis and investigation of the impact of each system parameter individually. To examine the effect of scattering on system performance, inter-pixel interference (IPI) is studied. Analysis of the impact of interference and noise on system performance reveals that in harbor waters, interference is the dominant factor in performance degradation, while in clear and coastal waters, system noise has a greater influence. Mobility in UOCC systems is a key advantage. The LED half-power angle is a highly effective parameter on this capability of UOCC systems. Increasing the LED half-power angle from 10 degrees to 60 degrees in harbor water with a channel length of 0.8 meters results in a 20 dB reduction in singnal to interference and noise ratio (SINR). Additionally, transmitter and receiver mobility can lead to angular misalignment. The results of this research show that changing the angle between the transmitter and receiver in harbor water with a channel length of 0.6 meters up to 45 degrees leads to a 15 dB reduction in SINR.

اصغر غلامي

ذبيح قاسملويي

محمد صدقي , فروغ السادات طباطباء