Rate-Splitting for Service-Aware Multi-Orbit Orchestration in 6G TN-NTN Networks

Integrated terrestrial–non-terrestrial networks (TN–NTNs) are a key enabler of sixth-generation (6G) connectivity across terrestrial, geostationary Earth orbit (GEO), medium Earth orbit (MEO), and low Earth orbit (LEO) domains. However, existing NTN frameworks do not jointly address service-aware serving-domain selection, multi-orbit coordination, and hierarchical multi-stream transmission. This paper proposes a service-aware multi-orbit rate-splitting multiple access (SA-MO-RSMA) framework that integrates global-common, orbit-common, and user-private streams with service-intent-aware serving-domain selection and resource orchestration. The framework operates as a system-level orchestration layer over existing 3GPP NTN architectures. A multi-criteria Orbit–Service Utility Function (OSUF) is introduced, together with metrics for service continuity, switching stability, power-normalized transmission efficiency, and synchronization robustness. Numerical results show that SA-MO-RSMA improves average per-user service utility, service continuity, switching stability, and transmission efficiency over the considered benchmark schemes, demonstrating its potential for coordinated service-aware multi-orbit TN–NTN operation.