Data transmission in store and forward based Non-Terrestrial Networks for IoT use cases
- Paper ID
83007
- DOI
- author
- company
i2CAT; Universitat Politecnica de Catalunya (UPC)
- country
Spain
- year
2024
- abstract
Non-Terrestrial Networks (NTNs) are considered key enablers of beyond 5th Generation (5G) and 6th Generation (6G) networks. Cellular Internet of Things (IoT) is experiencing a strong market growth, particularly NarrowBand-IoT (NB-IoT) is predominant, being the leading protocol for current and future massive Machine Type Communications (mMTC) use cases. The 3rd Generation Partnership Project (3GPP) standardization has recognized the relevance of integrating the non-terrestrial (i.e., satellite-based) segment with terrestrial 5G/6G infrastructures. NB-IoT, among other 3GPP protocols, gained basic NTN extensions in release 17. While 3GPP considers both transparent and regenerative payload architectures for NTN deployments, the present release focuses on a transparent payload approach. Transparent payloads acting as a repeater, as well as basic regenerative payloads only containing a Next Generation Node B (gNB), entail continuous end-to-end connectivity. Consequently, service can only be provided in areas where ground stations can be positioned for concurrent feeder link and service link availability. Providing service in areas where no feeder link availability is feasible can be achieved with regenerative payloads that support store-and-forward operation, which is expected to be incorporated in future releases (Rel-19 and beyond). Low Earth orbit (LEO) satellites offer a low-cost scenario to achieve global coverage with sparse constellations with as few as a single satellite, assuming an appropriate orbit. However, to provide service worldwide with a sparse constellation, store-and-forward operation, particular for user data transmission along the nodes is adamant with a lack of feasible continuous end-to-end connectivity. Enabling data transmission in store-and-forward based NTNs requires addressing challenges besides data buffering. Delays and discontinuity in the links between core network components require enhancements in the elements, their mechanisms, and data routing. This includes the triggering of data forwarding and potentially needed User Equipment (UE) paging procedure to re-establish signaling connections. In this work, we provide a 3GPP compliant architecture design capable of transmitting data in discontinuous store-and-forward based NTNs according to contact plans and the reduction of overheads in bandwidth constrained feeder link transmissions. Finally, we justify the validity of this architecture with an analysis and discussion. We find that choosing the shortest delay based on predicted contact periods has a significant advantage over less complex forwarding strategies. However, this requires computing overhead with several inputs, such as the satellite orbits and approximate UE locations at future moments in time.