Rate Splitting for MIMO Multibeam Satellite Systems

This paper deals with the problem of precoding in multibeam satellite system with rate splitting (RS). In contrast to the single-stream (SS) case where a unique private frame is transmitted towards each beam, in RS we consider the simultaneous transmission of a public frame to all intended users superimposed with each private frames. In this context, every user terminal (UT) firstly decodes the public frame which contains data from all UTs at all beams and; posteriorly, its intended private frame which is only decodable by a set of users. With this, each UT receives information from both the public and the private frame, leading to a system sum-rate increase in some cases. This performance increase is evaluated by computing an upper bound of the attainable rates. Moreover, a low-complexity precoding alternative is proposed considering a decoupled design of the precoding of the private frames and public frames. This technique is evaluated considering a real multibeam satellite system. A substantial gain with respect to the current benchmark technique is identified.