A mobile terminal 3 judges whether or not the mobile terminal is able to make a transition to a DTX period during Active, and, when judging that the mobile terminal is able to make a transition to a DTX period during Active, notifies a base station 2 to that effect. If the base station 2 judges that the mobile terminal is able to make a transition to a DRX period during Active when triggered by the notification from the mobile terminal 3, the base station temporarily stops supply of electric power to the data transmission processing units and the data reception processing units of the mobile terminal 3.