A Complementary Ground Component (CGC) is terrestrial infrastructure used to enhance satellite coverage, especially in areas with obstacles like urban environments. It’s employed in broadcasting and communication satellite systems to improve coverage, acting as “gap fillers.” CGC operates in the same frequency range as the satellite. In broadcasting, it can retransmit the satellite signal. For mobile communications, a more advanced ground component is needed, including a return channel. In the USA, it’s referred to as Ancillary Terrestrial Component (ATC) and requires coordination with the satellite operator to avoid interference. Japanese MBSAT uses a variation in the Ku band.