Experimental Demonstration of a Flexible Payload-Enabled Store & Forward NTN Architecture for Sparse LEO IoT

Abstract

Non-Terrestrial Networks (NTNs) based on Low Earth Orbit (LEO) satellites are key enablers for extending 5G and future 6G connectivity beyond terrestrial coverage. However, supporting massive Cellular IoT (CIoT) services over sparse LEO constellations remains challenging due to intermittent and non-concurrent service and feeder links, limited onboard resources, and strict User Equipment (UE) energy constraints. This paper presents an end-to-end experimental demonstration, developed within the ETHER project, of a regenerative Store and Forward (SnF) architecture for delay-tolerant CIoT services in sparse LEO NTN deployments. The proposed system combines software-defined flexible payload orchestration for dynamic onboard service execution, ground-assisted UE context mobility for service continuity across satellite passes, and Semantic-Aware Information Handling (SAIH) for reducing redundant transmissions. A hardware-in-the-loop testbed emulates multisatellite operation under discontinuous connectivity and validates the joint operation of these enablers. The results confirm successful service resumption without repeated full registration, correct feeder-link-based data forwarding, and a reduction of more than 75% in transmitted application-layer messages when SAIH is applied to a real environmental sensor trace. The demonstrated architecture provides practical evidence for scalable and energy-efficient CIoT service delivery in future integrated terrestrial/non-terrestrial networks.