The objective of the activity is to develop and demonstrate in orbit an experimental 5G g-NodeB (gNB) distributed between a regenerative payload and a satellite gateway. The demonstration will focus on showing the main functionalities of a gNB for Enhanced MobileBroadband services (eMBB) from LEO. Targeted Improvements: Enabling 5G regenerative satellites.Description: The 5th Generation (5G)wireless access technology, known as New Radio (NR), features spectrum flexibility, ultra-lean design, forward compatibility, low latency support, and advanced antenna technologies. Meanwhile, we are witnessing a resurgent interest in providing connectivity from space. In the past few years, there has been a surge of proposals to use large constellations of Low Earth Orbit (LEO) satellitesto provide broadband access in addition to the existing satellite communication systems. Although many of these initiatives focus on transparent satellites, some propose regenerative payloads that trade off higher on-board complexity with additional key features.For example, on-board channel routing along with inter-satellite links minimise the number of on-ground gateways and potentially the end-to-end link latency. Other advantage of the regenerative approach is an improved link budget. This activity will develop anddemonstrate in orbit an experimental 5G g-NodeB (gNB) distributed between a regenerative payload and a satellite gateway for eMBB services.The experimental gNB will be based on the 5G New Radio Non-Terrestrial Network (NR-NTN) 3GPP standard. First, the activity will identify and trade off different distributed gNB architectures including the implementation in the payload of the Distributed Unit (DU)and the Radio Control Link (RCL) layer, and the virtualisation at the gateway of the remaining upper layer functionalities of the Central Unit (CU). The activity will then down select the most promising solution and will apportion the corresponding functionalities between space and ground. The payload and the gateway will be developed accordingly with the payload being designed to fitin a LEOsmallsat. The demonstration mission will provide broadband connectivity to a number of on-ground satellite-enabled 5G userterminalsto be developed as part of the activity. The user terminals will also support the New Radio Non-Terrestrial Network version of the 3GPP 5G standard. The user link coverage will consist of at least 2 beams to allow the demonstration of beam hand-over functionalities. Their frequencies will be selected as part of the activity. To minimise the payload complexity, the overall user bandwidth will be minimised while maintaining compatibility with the 5G channelisation. The mission lifetime will be defined to maximise the use ofCOTS components. The main gNB functionalities that will be validated and demonstrated include radio resource management, dynamic allocation of resources to UEs in both uplink and downlink, beam hand-over, connection setup and release, session management, and radio access network sharing. Several tests will be performed to ensure the repeatability and reliability of the results.