Adaptive Error Control for Stratospheric Long-Distance Optical Links

Kurzfassung

This thesis explores the use of adaptive code-rate Hybrid Automatic Repeat Request (HARQ) methods and channel state information (CSI) to improve the transmission efficiency of Free-Space Optical (FSO) links between High Altitude Platforms (HAPs). The study looks at channel problems like atmospheric turbulence and static pointing errors, with a focus on the weak fluctuation regime of atmospheric turbulence. It explores the reciprocal behavior in bidirectional FSO channels to improve performance efficiency, providing evidence of channel reciprocity. The research proposes the use of HARQ, an adaptive Reed-Solomon (RS) code-rate technique, and different CSI types to address these impairments. Simulations of different situations are used to test how well these methods work. This helps us learn more about how efficient HARQ protocols are in inter-HAP FSO links, how important different CSI are in adaptive rate HARQ, and possible ways to make the system more efficient. This thesis looks at the channel model for inter-High Altitude Platform (HAP) Free-Space Optical (FSO) links in great detail, taking atmospheric conditions and static pointing errors into account. The channel is modeled as a lognormal fading channel under a weak fluctuation regime. The principle of channel reciprocity and the measures used to quantify it are discussed, providing a foundational understanding for the subsequent investigations.