A communication method including transmitting, from a radio terminal connected to a cell to a base station managing the cell operated in a first frequency, a first message that a discovery signal is transmitted for public safety in a second frequency; receiving, by the base station, the first message; and transmitting, from the base station to the radio terminal, a second message including information on radio resources to be used in transmission of the discovery signal in the second frequency, based on the first message. The method further includes transmitting, from the base station to the radio terminal, first information and second information. The first information indicates a threshold value for determining whether or not the radio terminal transmits the first message. The radio terminal uses the second information to determine whether or not the radio terminal is allowed to transmit the first message.