The objective of the activity is to develop and test physical layer techniques that mitigate the impact of the communication channel impairments on the performance of NGSO interactive broadband systems that use 3GPP 5G New Radio and DVB-based air interfaces. The end-to-end performance improvement achieved with the developed techniques will be evaluated in a software-based testbed to be developed as part of the activity. Targeted Improvements:Enabling physical layer techniques for NGSO systems not available today. Description: Current physical layer solutions for broadband satcom systems were originally designed for GEO satellites making them unsuitable for the emerging NGSO interactive broadband systems that demand new solutions given the different characteristics and impairmentsof the GSO and NGSO broadband mobile channels. In order to bridge this gap, the activity will develop and test physical layer techniques that mitigate the impact of the communication channel impairments on the performance of NGSO interactive broadband systems. The activity will first identify, model and implement in a physical layer simulator the impairments of the non-geostationary broadbandmobile channel in selected system scenarios. Such impairments will include linear and non-linear distortions (e.g., within active arrays and on-board DAC/ADCs), phase noise, intra- and inter-system interference, fast-varying fading, shadowing, and Doppler effects. Different user frequency bands (from Ku to Q/V and W bands), directivity of the user terminals, and constellation design (including Very Low Orbit LEO satellites) will be considered. To mitigate the identified impairments, advanced physical layer techniques willbe developed starting from existing air interfaces such as 3GPP 5G New Radio and DVB. The developed techniques will be implemented in the physical layer simulator and their performance assessed on both, forward and return links. Finally, recommendations for key technique/technology developments, as well as possible standardisation contributions, will be put forward. The outputs will be available to technical working groups in support of standardisation bodies.