A communication system (1000) according to the present invention includes a terminal (104); a first base station (100) to which the terminal (104) is connected before movement; a second base station (103) to which the terminal is connected after movement; and a gateway device (105) that connects the first base station (100) and the second base station (103) to an upper network so that they are able to communicate with each other. The first base station (100) transmits, to the second base station, a first signal to request the second base station to start the handover, the first signal including transport information which has been used for downlink data transmission by the gateway device (105) and the first base station (100) communicating with the gateway device (105) during a handover of the terminal (104). The second base station (103) receives the first signal and transmits, to the gateway device (105), a second signal to request the gateway device to update the transport information, the second signal in
