Architectures for Non-Terrestrial RAN: Integrated Satellite Access and Backhaul

The 3GPP standardized a new architecture and procedures for the NG-RAN to extend the network coverage to those hidden or unreachable areas. It consists in a distributed topology of low-complexity and low-cost network nodes named Integrated Access and Backhaul (IAB). The IAB is defined in Rel-16 and enhanced in Rel-17 and allows to distribute the gNB element in multiple Distributed Units (nodes) controlled by a Central Unit (donor) directly connected with the core network. This architecture is designed to relay the radio signal of the UE leveraging a wireless backhaul. Furthermore, enhancements for the mobile-IAB are expected in the Rel-18, in particular assuming nodes mounted on top of moving vehicle which can be either Terrestrial or Non-Terrestrial. Similarly, the 3GPP published a study which identified some appealing use cases where Non-Terrestrial Networks (NTN), in particular the satellite, can be exploited to relay the radio signal of the UE in areas unserved or uncovered by Terrestrial networks. The integration of a satellite component in this scenario may be a further confirmation of its added value and the support that could be provided in mobile networks. First steps were already moved with the definition of two frequency bands for the Satellite Access Node (SAN) operations by 3GPP in Rel-17, while further enhancements are expected for 6G networks. This paper briefly reports the key aspect of the IAB technology and will investigate possible architectures including a satellite components. Two main integration approaches will be evaluated analysing possible adaptations required for SatCom in direct access.