Federation of Satellite Systems for Integrated Satellite-Terrestrial Networks: the 5G-HUB Project. - Giovanni Giambene; Riccardo Zambon; Minh Hoang Nguyen; Miguel Ángel Vázquez; Jorge Baranda; Erislandy Mozo; Eddi González; Nuria Trujillo Quijada; Lorenzo Santilli; Luis Cordeiro; José Guimarães; Laura Campos; et al. (SoftCOM, 2025)