Rate Splitting for MIMO Multibeam Satellite Systems

Abstract

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 frame is transmitted towards each beam, in RS we consider the simultaneous transmission of a single common frame to all beams jointly with each beam intended frame transmission. 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 frame (private frame) which contains information from the UTs located at the same beam. 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 message. This technique is evaluated considering a real multibeam satellite system. A substantial gain with respect to the current benchmark technique is identified.