Objective: The objective of this activity is to develop, deploy and operate a flexible software-defined radio communication testbedwith a frequency flexible RF front end on the International Space Station, supporting a wide range of frequencies up to Q/V band addressing 5G, signal processing and advanced techniques. Targeted Improvements: Enabling innovative and fast developments of future satcom applications from UHF to Q/V band that are difficult to achieve with on-ground testing only. Description: Nowadays, there isno capability to develop and test in-orbit novel satellite communications payload functionalities in an agile manner that suits thedemands and pace of industry. The current in-orbit test opportunities available as hosted payloads on larger missions take often yearstoget in-orbit data, whilst the faster pace in-orbit demonstration CubeSat missions lack the power and continuous connectivity capabilities needed for the testing of sophisticated telecommunications functions and for which testing on ground only is not sufficient. In this activity, a flexible software-defined radio communication testbed with a frequency flexible RF front will be designed,deployed on the International Space Station and operated, supporting a wide range of frequencies. The testbed will provide unprecedented capabilities in terms of (line-of-sight) exposure, processing power, high-bandwidth ground connectivity, enabling RD into newwaveforms, processing methods, 5G and connectivity scenarios. The testbed will be used to: - develop and test communication links at low elevation angles to increase availability and system capacity; - develop and test novel low power M2M/IoT techniques in representative interference conditions; - interactively develop and test interference mitigation, monitoring and localisation techniques, taking into account low Earth orbit characteristics and low elevation angles; - develop and test air-interfaces related to 5G with the goal to enable the reuse of terrestrial hardware for space 5G nodes and - contribute to the evolution of the CCSDS payload data telemetry standard. The testbed will allow 24 months of operation for emulation of a wide range of payload functions in space, enabling rapid iterations in the development, deployment and testing. Footnote: On Delegation Requestactivities will only be initiated onthe explicit request of at least one National Delegation.