Communication method, radio terminal, processor and base station

A radio terminal, comprising:

• a transmitter;
• and
• a receiver, wherein
• the receiver is configured to receive, from a base station managing a cell operated in a first frequency, a first message including first information indicating a threshold value,
• the transmitter is configured to transmit, to the base station, a request message in response to Reference Signal Receiver Power (RSRP) of a radio signal received from the cell being below the threshold value, the request message requesting transmission of a discovery signal for public safety in a second frequency band different from the first frequency, and
• the receiver is further configured to receive, from the base station, a second message based on the request message, wherein the second message includes second information on radio resources to be used in transmission of the discovery signal in the second frequency.

A processor for controlling a radio terminal connected to a cell operated in a first frequency, the processor configured to execute processes of:

• receiving from a base station managing the cell, a first message including first information indicating a threshold value;
• transmitting a request message to the base station in response to Reference Signal Received Power (RSRP) of a radio signal received from the cell being below the threshold value, the request message requesting transmission of a discovery signal for public safety in a second frequency band different from the first frequency;
• and
• receiving, from the base station, a second message based on the request message, wherein the second message includes second information on radio resources to be used in transmission of the discovery signal in the second frequency.

A base station configured to manage a cell operated in a first frequency, comprising:

• a receiver;
• and
• a transmitter, wherein
• the transmitter is configured to transmit a first message including first information indicating a threshold value to a radio terminal connecting to the cell,
• the receiver is configured to receive, from the radio terminal connecting to the cell, a request message requesting transmission of a discovery signal for public safety in a second frequency band different from the first frequency, the request message being transmitted from the radio terminal in response to Reference Signal Received Power (RSRP) of a radio signal received by the radio terminal from the cell being below the threshold value, and
• the transmitter is further configured to transmit, to the radio terminal, a second message including second information on radio resources to be used in transmission of the discovery signal in the second frequency, on a basis of the request message.