A source terminal, for communications with a destination terminal via satellite links to two clusters of satellites, comprises a transmitter and a multibeam antenna system. The transmitter includes a preprocessor and a bank of modulators. The preprocessor performs a K-muxing transform, which has an inverse transform, on M concurrent input data streams to generate concurrently M output data streams, M>1. Each output data stream is a linear combination of the M concurrent input data streams. The bank of modulators transforms N of the M output data streams into N signal streams, N≤M. The multibeam antenna system transforms the N signal streams into N shaped beams and radiating N1 of the N shaped beams towards the first cluster of satellites and N2 of the N shaped beams towards the second cluster of satellites, where N1 and N2 are positive integers and N1+N2=N.