Integration of Non-terrestrial ‌networks ‌into the 5G New Radio setup stand out as a strong solution to broad connectivity: they stretch mobile broadband further than what earthbound setups can handle by themselves. Low Earth Orbit satellite arrangements bring clear benefits in this area, shorter signal travel times, stronger reuse of space, and easy fit with existing cellular designs. This thesis investigates the downlink performance of 5G NR operating over LEO based non terrestrial networks through detailed system level simulations. The study focuses on a single LEO satellite equipped with a multibeam architecture composed of nineteen beams arranged in a hexagonal layout.