There is provided a wireless communication system including a radio-signal base station, and a mobile wireless terminal operating in a power-saving mode in which the mobile wireless terminal intermittently receives packet signals, and in a normal mode in which the mobile wireless terminal regularly receives packet signals. When the radio-signal base station receives packet signals addressed to a mobile wireless terminal being in the power-saving mode, the radio-signal base station temporarily stores the received packet signals. The mobile wireless terminal requests the radio-signal base station to transmit the packet signals thereto, receives a part of the packet signal from the radio-signal base station, and, if the mobile wireless terminal judges that it would be necessary to carry out real-time communication for receiving entirety of the packet signals, the mobile wireless terminal transfers to the normal mode from the power-saving mode for receiving entirety of the packet signals.