Outage Analysis of RSMA Space-Terrestrial Downlink in the Presence of Ground Interference

As channel resources in wireless communications become increasingly constrained, there is a growing demand for novel multiple-access technologies, among which the rate-splitting multiple access (RSMA) provides an efficient way of allocating channel resources. RSMA proves to be a flexible interference management strategy that is characterized by splitting the information to be transmitted into two or more parts. It also provides a unified framework that can balance space-division multiple access (SDMA) and power domain non-orthogonal multiple access (NOMA). Specifically, the SDMA scheme treats interference as noise, and the NOMA scheme fully decodes interference, while RSMA partly decodes interference and partly treats interference as noise based on interference severity. In this paper, we analyze the outage performance of a downlink space-terrestrial communication system adopting RSMA that is deteriorated by interfering nodes uniformly distributed on the ground. Approximate expressions for the outage probability at a target satellite user are derived, and some enlightening conclusions are reached, which can benefit the understanding and deployment of RSMA in relevant scenarios.