, service reliability/availability, energy consumption, and con- nection density. A role for NTNs in the 5G system is expected for the following verticals: transport, public safety, media and entertainment, e-health, energy, agriculture, finance, and automotive. For the satellite ecosystem, one of the key drivers in adopting 3GPP standardized 5G technology (as opposed to the proprietary technologies used today) is the desire to reduce both the network equipment and especially the terminal cost, by reusing a mass market technology. 5.3.3 NTN Based NG-RAN Architecture The outcome of the study conducted by 3GPP in Release-16, devoted to the analysis of the key aspects and potential issues involving the integration of NTNs in 3GPP cellular systems, is reported in 3GPP TR 38.821. Hereafter, some possible reference architectures considered in the study for such satellite exploitation in terrestrial networks have been depicted. These configurations are instrumental for the next sections to highlight and review the impacts of the specific peculiarities of satellite communication links. It shall be noted that the fol- lowing architectures are applicable to all possible constellations (e.g. GEO or LEO) and all available radio frequencies (e.g. S-band or Ka-band). Multiple NG-RAN architecture options to support NTN are being considered in the study and are described in detail below. However, it is expected that only a limited subset of these options will be standardized in Release-17. 5.3.3.1 Access Network with Transparent NTN Payload The first and easiest configuration for connecting user terminals to the NG-RAN is shown in Figure 5.3.1, where a transparent satellite payload is assumed. The satellite payload imple- ments only frequency conversion and power amplification functions in both uplink and downlink directions. In practice, the NR-Uu interface is terminated in the gNB, which is on the ground, and it is transparent for the satellite. As far as the user terminal is concerned, both handhelds and dedicated satellite e