To control the communication quality on the terminal basis without making the base station more complicated, it is provided a communication system, comprising at least one computer and a gateway that is connected to the at least one computer through a first network. The gateway is connected to at least one terminal through a second network. The at least one terminal performs communications with the at least one computer via the gateway. The gateway estimates quality of the communications between the gateway and the at least one computer in the first network; and determines a priority for the communications between the gateway and the at least one terminal in the second network according to the estimated quality of the communications in the first network.