Non-linear precoding based hybrid space-ground beamforming for multi-beam satellite systems

Multi-beam mobile satellite systems have a great potential in providing broadband mobile services over a large area to achieve a high system throughput. On ground beamforming techniques are quite promising but require a large feeder link bandwidth to deliver all the feeds??? signals. There are two potential solutions to solve this problem. 1) Hybrid space-ground beamforming is able to reduce the feeder link bandwidth and save spectral resources, which exhibits a good trade-off between the performance and the space/ground complexity. 2) The groundbased beamforming using multiple distributed gateways divides the whole spectrum of the feeder link into several sub-sets, relaxing the bandwidth and processing requirements at each gateway. In this paper, we propose a distributed non-linear precoding based hybrid space-ground beamforming technique, where on-board beamforming aims at suppressing interference among gateways and on-ground beamforming is implemented distributively at each gateway. The proposed technique takes advantages of both the hybrid scheme and the distributed multiple gateway architecture, and does not require any cooperation or any exchange of channel state information among gateways. We show the benefits of the proposed technique over the fully onground beamforming schemes as well as its linear counterparts.