Impact of Elevation Angle on Multi-Beam LEO Satellite Communication Systems

Abstract

Compared to well-established geosynchronous equatorial orbit (GEO) satellite networks, low Earth orbit (LEO) satellites bring new challenges to overcome, such as the distortion of the satellite footprint with varying elevation angle. The impact of the elevation angle on system behavior is not sufficiently studied in literature, and guidelines to parameterize LEO systems are lacking. This paper addresses these gaps by providing a framework to analyze the satellite footprint behavior of arbitrary multi-beam satellite systems with large antenna arrays and analyzing the system behavior of a LEO satellite operating in the Ka-band (30GHz) for varying elevation angle and serving area size. The analysis considers the directivity and antenna array steering of the antenna array and the curvature of the Earth. The provided framework allows repeatable analysis and offers a means to parameterize systems in terms of serving area size, beam design, and operating elevation angles. Analysis over elevation angles confirms the strong influence of the satellite elevation angle on the system performance and indicates that elevation angle dependence of LEO systems needs to be considered in the evaluation of future technologies. It is shown that the system drifts from a noise-limited regime at high elevation angles to an interference-limited regime with decreasing elevation angle. The findings suggest a minimum elevation angle of 30° for practical systems, as lower elevation angles show excessive propagation loss and severe interference due to beam distortion. Link budget analysis further indicates that systems require highly directional antennas with large gain to serve handheld user devices.