The multi-beam broadband satellite systems have been deployed to provide broadband services to their under-served geo-graphical area. In one hand, with assuming full frequency reuse among beams the resulting interference requires either a pre-or post-cancellation process. On other hand, by increasing the number of beams, the ground and space units must employ an extensive communication effort on the feeder link (i.e. the link between gateway and satellite) to exchange all of the feed signals, yet maintaining a low processing responsibility to the payload. Since the feeder link spectral resources are scarce, it is desirable to use an on-board beam generation process which leads to a significant feeder link bandwidth reduction. In this context, a hybrid space/ground processing (i.e. both the gateway and the satellite digitally process the transmitted/received data) shall be employed. This work presents a design of the corresponding on-board beam generation process and precoding in the forward link (i.e. from gateway to users in coverage area) of satellite system. In order to effective limit inter-beam interference, this work also predicts a zero forcing precoding technique taking into account the per feed power constraint for practical issues. To this end, we formulate the precoding problem with considering individual on-board feed in order to efficient and more realistic use of payload power resources. This is done by considering the zero forcing and its relation to the theory of generalized inverse in the linear algebra.

Peer Reviewed