Overview and comparison of on-ground and on-board beamforming techniques in mobile satellite service applications

The objective of this paper is to review state-of-the-art techniques of beamforming in mobile satellite systems and evaluate the potential benefits/drawbacks of on-ground beamforming compared with on-board beamforming approach. The paper also provides a short analysis of beamforming error sources in on-ground beamforming such as propagation effects at feeder link level, on-board degradations at payload level, differential atmospheric perturbations, and Doppler shift effect. An investigation of signal processing techniques is also performed to provide a preliminary assessment of the interest for employing adaptive beamforming and precoding techniques in multi-spots mobile satellite systems.