Multibeam joint precoding: Frame-based design

The key technology in the next generation high throughput broadband satellite communications has yet to be defined. In this quest, the ultimate goal is the efficient utilization of the available spectrum. The focus of the present chapter is set on the link between the satellite and the on ground user terminals requesting interactive services, commonly referred to as the user link. Currently, multibeam antennas offer the necessary spatial degrees of freedom to separate individual signals that are addressed to different users. However, antenna imperfections give rise to interference from adjacent beams. Up to date multibeam satellites typically cope with this increased level of interference by fractional frequency and polarization reuse among beams. However, such a spectrum reuse limits the system’s total throughput. For instance, cutting edge high throughput satellite (HTS) systems—like Viasat-1 [1] ---with a throughput of about 140 Gbit/s--- typically split the available bandwidth in two frequency bands and two orthogonal polarizations generating a four color frequency reuse pattern across the coverage area. Following the current trend, the deployment of a high number of beams is certainly anticipated. Nevertheless, hardware and cost limitations prevent multibeam satellites with an arbitrarily high number of beams.