A base station holds information on uplink radio resources which has been allocated to at least one already connected communication terminal for performing radio communication using a high frequency with the base station, receives a notification of participation in a radio communication system from a new communication terminal, and allocates unallocated uplink radio resources using high frequencies to the new communication terminal based on the information on the uplink radio resources when received the notification of participation. The new communication terminal transmits data to the base station by using the allocated uplink radio resources.