which is expected to drive down costs of satellite connectivity. To this end, 3GPP conducted a num- ber of studies in Release-15 and Release-16 for the support of non-terrestrial network (NTN) connectivity and committed to specify enhancements needed for NTN in Release-17. At the time of writing this book, the work on Release-17 has just started and therefore the present section describes various options that have been considered and provides a high-level outlook into what is going to be specified in Release-17 and beyond. An NTN refers to a wide range of systems operating in various frequency bands allocated by the International Telecommunication Union (ITU) to Broadcast Satellite Services (BSS), Fixed Satellite Services (FSS), or Mobile Satellite Services (MSS). It is possible to distinguish between two types of NTNs according to the type of terminals targeted: Terminals with omni-directional antennas: The targeted terminals are handheld or Inter- net of Things (IoT) devices. The service links typically operate in frequency bands below 6 GHz and provide narrow to wide band services directly to end-user devices. Terminals with directional antennas: The targeted terminals are mounted on a fixed building or on a moving platform (e.g. bus, train, ship, aircraft, etc.). The service links typically operate in frequency bands above 6 GHz. These systems typically provide direct-to-home/office or backhaul services. The first version of 5G specifications (i.e. Release-15) covers the most urgent use cases and scenarios and does not include satellite support. However, the flexibility of NR design and NG-RAN architecture allows it to be extended to new use cases, such as NTNs. Both geosta- tionary orbit (GEO) and low -earth orbit (LEO) based NTN access is considered in the 3GPP study item described in 3GPP RP-190710 as reference deployment scenarios for NTN. While GEO satellites are located at an altitude of about 35 786 km at a fixed position above the equator, LEO satellites are circling the earth at altitudes between 500