ility of using standard 5G technology (with some adaptations) promises lower cost of communications. Key components of the NTN architecture candidates are illustrated in Figure 9.12. Satellite or other high-altitude platforms may consist of only a relay function (radio fre- quency conversion) from the access side to the feeder link to the Ground Station GS, or it may include part or all of 5G radio baseband processing (gNB-DU or full gNB). The remaining part of the 5G radio and core network is then located on the ground with the GS, or anyway reachable via the GS. Performance depends on the selected functional split and whether retransmissions to the terminal are supported by the satellite or via the GS. Terminals are specific satellite terminals requiring larger antenna, or alternatively, regular 5G UEs connect to the satellite service via a satellite gateway, which then com- municates with the satellite. With high-altitude platforms, regular UEs may be feasible. Satellites may also have a link to another satellite (Inter-Satellite Link, ISL) which may be needed if the satellite cannot reach any GS directly. The architecture reuses existing 5G logical interfaces, protocols, and concepts as much as possible, with adaptations to cope with longer latencies and other NTN specifics. 9.5.5 Time-Sensitive Networks Originally called the IEEE Audio and Video Bridging (AVB) task group, the group was renamed to TSN TG (Time-Sensitive Network Task Group) [22], as other application areas emerged. Many of the targeted use cases are today served by vendor- or application-specific protocols and solutions, in factory automation, automotive, and other areas. With the enhancements under definition, these use cases are targeted to be served by Ethernet 9 Transport Altitude On-board Satellite (or other High Geostationary Altitude Platform) Earth Orbit GEO Relay function (gNB on ground) 35 768 kms gNB-DU (gNB-CU on ground) Full gNB (core on ground) Medium Earth Orbit 2000 kms Inter-satellite Link (ISL) Low Earth Orbit 500-2000 kms Ba