Optimized MIMO Feeder Link Architectures for 6G NGSO Mega-Constellations

Multiple antenna feeder links are a promising solution to address the forecasted data-rate bottlenecks in future 6G Non-Geostationary Orbit (NGSO) constellations. In this paper, a comparative analysis of feeder architectures is conducted between the Uniform Linear Array (ULA) and the Uniform Circular Array (UCA). The study starts with a NGSO trajectories examination, followed by the derivation of the instantaneous optimal capacity conditions. Furthermore, a novel key performance indicator based on the inverse condition number of the channel matrix is introduced. This indicator facilitates performance comparison across the Field-of-View (FoV). Numerical simulations evaluating array orientation dependence, orbit altitude influence, and frequency stability, indicate better performance for ULA geometries, thus positioning them as a suitable choice to scale the system throughput.