  5G and future cellular networks intend to incorporate low earth orbit (LEO)
satellite communication systems (SatCom) to solve the coverage and availability
problems that cannot be addressed by satellite-based or ground-based
infrastructure alone. This integration of terrestrial and non terrestrial
networks poses many technical challenges which need to be identified and
addressed. To this aim, we design and simulate the downlink of a LEO SatCom
compatible with 5G NR, with a special focus on the design of the beamforming
codebook at the satellite side. The performance of this approach is evaluated
for the link between a LEO satellite and a mobile terminal in the Ku band,
assuming a realistic channel model and commercial antenna array designs, both
at the satellite and the terminal. Simulation results provide insights on open
research challenges related to analog codebook design and hybrid beamforming
strategies, requirements of the antenna terminals to provide a given SNR, or
required beam reconfiguration capabilities among others.
