Non-Orthogonal Broadcast and Unicast Joint Transmission for multi-satellite joint communication

With the development of communication technology, users desire information services anytime and anywhere. These information services are often a mixture of broadcast and unicast communication data. Compared with terrestrial networks, satellite communication systems have a larger coverage area and can provide seamless global information services, which can better realize joint broadcast and unicast services than terrestrial networks. On the other hand, rate-splitting multiple access (RSMA) technology divides user data into two parts, common data and private data, and then transmits these two parts overlapping in the power domain, which fits well with the joint broadcast and unicast transmission mode and has the higher spectrum efficiency than orthogonal multiple access. Motivated by this fact, we introduce RSMA technology into the satellite communication system and design a joint non-orthogonal broadcast and unicast (NOBU) transmission scheme for a multi-satellite joint service system. We establish the optimization problem of a system weighted sum rate (WSR), and an alternating optimization algorithm based on weighted minimum mean square error is proposed to solve the non-convex WSR problem. Simulation results show the proposed NOBU scheme has better performance than the conventional orthogonal transmission mode.