Satellite-Terrestrial Integration: 5G Architectures for the Seamless Support of Mission Critical Services

This paper studies integration issues for the achievement of TN-NTN systems providing mission-critical (MCX) services in the EU 5G-GOVSATCOM project. The standardization of NTN as an integral part of 5G terrestrial systems is progressing, with important progress made in the last Releases 17 and 18. This important evolution, however, is not complete because the integration of the two networks is also needed at the protocol level. In the first part of this paper, we investigate MCX requirements. Then, two alternative architectures are considered with distinct core networks or with unified core networks, according to Release 20. The second part of this paper presents the issue of the seamless Vertical Handover between TN and NTN, proposing the adoption of a smart gateway server, a new block of the 5G system to manage a seamless switch from the two networks when some critical conditions are met. Using VPNs from UE to TN and TNT can facilitate the VHO procedure at the network layer, just avoiding a change of the IP address of the UE during the VHO that would cause a drop for the MCX end-to-end service. We believe this paper can provide useful insights into GOVSATCOM system design and the experimental phase of this project.