Coarse Beamforming Techniques for Multi-Beam Satellite Networks

Coarse beamforming is a space processing scheme which allows for efficient use of the available spectral resources on the feeder link of a multi-beam broadband satellite system. In this framework, spectral occupancy of the multiplexed antenna signals that must be exchanged between the satellite and the gateway is a critical issue, up to the point that a costly multiple gateway infrastructure could be required to restrain bandwidth usage. Alternatively, a hybrid on board/on ground processing ar- chitecture is desirable, where the effect of space processing allows to project feed signals on a subspace, thus reducing the required feeder link bandwidth. This foresees a fixed processing scheme on board the satellite, which we refer to as Coarse Beamforming, yielding an overall system which relies on reasonable payload complexity, together with on ground processing flexibility. We explore two Coarse Beamforming techniques for the return link of a multi beam satellite system, and we evaluate the effect of compression in terms of reconstructed signal degradation. We show how, without significant distortion, bandwidth occupancy can be considerably reduced.