G-RAN; Architecture description. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.401 (2019). NG-RAN; Architecture description. Available at: www.3gpp.org (accessed May 29, 2020). 5 NG-RAN Evolution 3GPP Technical Specification 38.425 (2019). NG-RAN; NR user plane protocol. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.470 (2019). NG-RAN; F1 general aspects and principles. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.471 (2019). NG-RAN; F1 layer 1. Available at: www.3gpp.org (accessed May 29, ,2020). 3GPP Technical Specification 38.472 (2019). NG-RAN; F1 signalling transport. Available at: www.3gpp.org (accessed May 29, 2020). 3GPP Technical Specification 38.473 (2019). NG-RAN; F1 Application Protocol (F1AP). Available at: www.3gpp.org (accessed May 29,2020). 3GPP Technical Specification 38.474 (2019). NG-RAN; F1 data transport. Available at: WWW .3gpp.org (accessed May 29, 2020). Request for Comments 4301 (2005). The Internet Engineering Task Force (IETF), Network Working Group, Security Architecture for the Internet Protocol. Available at: www.ietf.org (accessed May 29, 2020). Request for Comments 7296 (2014). The Internet Engineering Task Force (IETF), Network Working Group, Internet Key Exchange Protocol Version 2 (IKEv2). Available at: www.ietf .org (accessed May 29, 2020). 5.3 Non-terrestrial Networks 5.3 Non-terrestrial Networks Leszek Raschkowski1, Eiko Seidel ², Nicolas Chuberre³, Stefano Cioni4, Thibault Deleu5, and Thomas Heyn6 1 Fraunhofer HHI 2Nomor Research GmbH 3 Thales Alenia Space 4uer Space Agency 5 Thales Alenia Space 6 Fraunhofer IIS Prior to 5G, 3GPP networks were traditionally designed to support terrestrial mobile net- works. However, with the advent of 5G, there was on one hand a desire from mobile vendors to expand the ecosystem into new verticals and, on the other hand, a desire from the satel- lite ecosystem to adopt 3GPP technologies to benefit from their economies of scale, 