Joint Feeder Link Bandwidth Compaction and Interference Mitigation Based on a Hybrid Space/Ground Processing Architecture for a Broadband Multi-Beam Satellite System

In a broadband multi-beam satellite system, a hybrid space/ground processing has the potential to allow for a more efficient use of the feeder-link spectral resources when the payload is equipped with a multi-fed reflector antenna and the number of feeds exceeds the number of users to be served on-ground. In conventional systems, where the processing burden is kept on-ground to minimize payload complexity, the on-ground and the space segments have to engage in extensive communication efforts on the feeder-link to exchange the whole set of multiplexed feed signals. When spectral resources are scarce, an expensive multiple-gateway (GW) infrastructure is required to cope with these communication efforts. As an alternative, this work suggests a hybrid architecture where the satellite and the GW are able to exchange a set of intermediate signals called feedlets, whose cardinality is smaller than the number of feeds. When this occurs, the satellite implements a fixed non-adaptive processing called Coarse Beamforming (CB) to reconstruct feed signals from the subset of feedlets. Non-adaptive processing keeps the payload complexity acceptable, while a gain is obtained in terms of feeder-link bandwidth reduction. The objective of this paper is to study the implications of introducing a fixed processing scheme on-board, the satellite for the Forward Link (FL) of a broadband multi-beam satellite network. The first part of this work studies the effect of bandwidth compression on the quality of on-board reconstructed feed signals.The second part focuses on the effect of coarse beamforming on the system’s spectral efficiency and availability when adaptive precoding is implemented at the GW to allow for a full-frequency-reuse scheme.