A communication system capable of realizing a three-dimensional network of the fifth generation mobile communication with low propagation delay in a radio communication is provided. The communication system comprises a radio relay station that relays a radio communication with the terminal apparatus. The radio relay station is provided in a floating object that is controlled so as to be located in a floating airspace with an altitude of 100 [km] or less by an autonomous control or an external control. When the floating object is located in the floating airspace, the radio relay station forms a three-dimensional cell in a predetermined cell-formation target airspace between the floating object and a ground level or a sea level.