Optik kablosuz iletişim sistemlerinin enerji kısıtları altında tasarım ve analizi

Optical Wireless Communication (OWC) is a field in communication that employs light waves (i.e.,Light Emitting Diodes (LEDs), or Laser Diodes (LDs)) for wireless data trans- mission, and provides a Line of Sight (LOS) link with a capacity comparable to fiber optics and much higher than those that can be supported by Radio Frequency (RF) counterparts. In addition, since they operate in optical spectrum, they are immune to interference. Further- more, unlike RF links which require either area or link license for operation, no licensing fee is required in OWC communication systems. OWC encompassing sub-branches like Free Space Optical (FSO) and Underwater Op- tical Wireless Communication (UOWC). FSO uses laser transmitters operating at infrared wavelengths through free space. It specifically offers faster data rates, improved security, and cost-effective connectivity suitable for high-data-throughput applications and scenar- ios where physical cables or RF networks are impractical. UOWC addresses the limitations of RF and acoustic signals in water, facilitating reliable and high-speed communication for marine applications. In OWC systems, particularly in underwater and outdoor environments, energy effi- ciency becomes a critical design criterion due to reliance on batteries with limited capacity, requiring regular and costly recharging or replacement. This dissertation focuses on the significance of energy efficiency in OWC, specifically targeting airborne and underwater networks facing energy resource limitations. In underwater environments, Underwater Sensor Networks (USNs) are deployed for collaborative tasks such as pollution monitoring, ocean currents analysis, equipment con- trol, and mineral exploration. Sensor nodes are scattered throughout the marine environ- ment, and data is collected at a gateway node, typically a buoy or support vessel. Data transmission can occur through single-hop or multi-hop routes, with multi-hop transmis- sions posing the risk of disruptions from individual node failures. In the case of multi-hop data transmission, sensor nodes consume power for data relaying and routing. To address this, the dissertation proposes the utilization of Autonomous Underwater Vehicles (AUVs) for data collection, eliminating the need for data relaying and reducing energy consump- tion. The proximity of AUV to each sensor node also decreases the power required for their own data transmission. However, AUVs face challenges like latency in data delivery and high-power consumption. The dissertation explores the implementation of efficient trajectories in AUV-assisted data collection within USNs. Furthermore, the dissertation introduces solar-powered AUVs to further enhance en- ergy efficiency in underwater environments. By incorporating solar panels, AUVs achieve longer endurance, cost-effective operations, and environmentally friendly solutions. We model the energy harvesting from the Sun considering different geographical locations, different days of a year, different times in a day at different depths and types of water in- cluding pure see, clear water, coastal water, harbor water to asses the energy harvesting made possible from the Sun in underwater environments. The research addresses the chal- lenge of charging batteries during the day and conducting surveys at night, presenting an optimal Three-Dimensional (3D) trajectory that maximizes energy harvesting and survey efficiency. In outdoor environments, Unmanned Aerial Vehicles (UAVs) present versatile and cost- effective solutions for communication networks. This study explores both fixed-wing UAVs and rotary-wing UAVs for backhaul connectivity, with a particular emphasis on energy- efficient approaches utilizing solar-powered UAVs. Specifically, solar-powered rotary-wing UAVs are investigated for their potential to enable efficient backhauling in cellular net- works, leveraging FSO technology. The dissertation introduces an altitude optimization problem aimed at striking a balance between energy harvesting and consumption. Addi- tionally, the research includes an assessment of High Altitude Platforms (HAPs) which is a specific type of fixed-wing UAVs operating at high altitudes in the stratosphere layer (17km-20km). The evaluation focuses on analyzing the energy harvesting and consumption aspects of these platforms. Additionally, to enhance the energy efficiency of airborne networks, laser power beam- ing is proposed to charge the UAVs/HAPs wirelessly. This technology is gaining attention due to its high efficiency and ability to transfer power over long distances. It involves using powerful laser beams to transfer energy to a receiver equipped with a photovoltaic cell that converts the laser energy into electricity. In addition to that, to further enhance the efficiency of OWC systems, Simultaneous Lightwave Information and Power Transfer (SLIPT) is investigated. SLIPT utilizes light intensity to transfer both power and data at the same time. By combining power and data transfer in the same OWC link, SLIPT has the potential to enhance the performance and lifespan of the backhaul link.