Investigation of air to air channel models for UAV communications

Unmanned Aerial Vehicles (UAVs), due to their continuously advancing technologies and features such as low cost, small size, light weight, high maneuverability and quick deployment, have begun to find extensive use in military, civilian, and commercial fields such as transportation, logistics, agriculture, telecommunications, healthcare, media, and entertainment, both in single and multiple (swarm) applications. In order to establish reliable communication links between ground control stations and UAVs or between UAVs themselves, the characteristic properties of the communication channel need to be identified, and the necessary parameters for communication should be selected based on these characteristics. In this thesis, the analysis of the air-to-air channel for different scenarios of UAVs in the field of communication is conducted using the "Two-Ray Model" based on ray tracing method. The communication channel characterization is carried out for the specified scenarios by analizing the line-of-sight signal received by the receiver and signals that are propagated from different paths and reach the receiver through ground reflections. Various scenarios with different UAV altitudes, inter-UAV distances, antenna types, environmental factors, etc. are considered to analyze the communication channel. In addition to the theoretical results of channel characterizations obtained by using the model for different flight scenarios, this study discusses the preliminary stages of field measurement studies conducted in various scenarios for communication between two identical UAVs, by introducing the platforms used in the research. The obtained field measurement results are interpreted and compared with the theoretical results.