Base station and method for determining unlicensed frequency candidate

1. A base station, comprising:

a storage device configured to store results of carrier sensing performed respectively by a transmission terminal and a reception terminal to perform device-to-device communications with a plurality of sub-bands in unlicensed frequencies being frequencies of which a use is not licensed for data transmission; and

a controller configured to extract at least one or more sub-bands of the unlicensed frequencies being determined that are in an idle status or have a high possibility to be in the idle status by both of the transmission terminal and the reception terminal in the carrier sensing results as candidates for sub-bands of the unlicensed frequencies that the transmission terminal uses in data transmission with the device-to-device communications,

wherein the controller is configured to transmit an allocation result of radio resources using licensed frequencies of which a use for the data transmission is licensed and candidates for the unlicensed frequencies to the transmission terminal and the reception terminal when device-to-device communications using the licensed frequencies is performed in addition to the device-to-device communications using the sub-bands in the unlicensed frequencies.

2. The base station according to claim 1 , wherein the controller is configured to transmit a signal configured to integrate the allocation result of the radio resources using the licensed frequencies and the candidates for the unlicensed frequencies to the transmission terminal and the reception terminal.

3. A transmission terminal to transmit data to a reception terminal with device-to-device communications, the transmission terminal comprising:

a controller configured to execute, when transmitting data with device-to-device communications using licensed frequencies as frequencies of which a use is licensed for data transmission and at least one or more sub-bands in unlicensed frequencies of which a use is not licensed for the data transmission to a reception terminal, a process of:

receiving an allocation result of radio resources using the licensed frequencies and candidates for sub-bands of the unlicensed frequencies determined that are in an idle status or have high possibility to be in an idle status by both of the transmission terminal and the reception terminal from a base station;

determining the sub-bands of the unlicensed frequencies used for the data transmission by carrier sensing for the candidates for the sub-bands of the unlicensed frequencies; and

transmitting the allocation result of the radio resources using the licensed frequencies and an allocation result of the radio resources using the determined sub-bands of the unlicensed frequencies to the reception terminal.

4. The transmission terminal according to claim 3 , wherein the controller is configured to transmit a signal configured to integrate an allocation result of the radio resources using the licensed frequencies and an allocation result of the radio sources using the determined sub-bands of the unlicensed frequencies to the reception terminal.

5. The transmission terminal according to claim 3 , wherein the controller is configured to execute a process of reserving the sub-bands of the unlicensed frequencies when determining the sub-bands of the unlicensed frequencies used for the data transmission.

6. A method for controlling device-to-device communication, the method comprising:

storing, using the base station, results of carrier sensing performed respectively by a transmission terminal and a reception terminal to perform device-to-device communications with respect to at least one or more sub-bands in unlicensed frequencies being the frequencies of which a use is not licensed for data transmission; and

extracting, using the base station, at least one or more sub-bands of the unlicensed frequencies being determined that are in an idle status or have high possibility to be the idle status by both of the transmission terminal and the reception terminal in the carrier sensing results as candidates for sub-bands of the unlicensed frequencies to be used for the transmission terminal to transmit data with the device-to-device communications,

transmitting, using the base station, an allocation result of radio resources using licensed frequencies of which a use for the data transmission is licensed and candidates for the unlicensed frequencies to the transmission terminal and the reception terminal when device-to-device communications using the licensed frequencies is performed in addition to the device-to-device communications using the sub-bands in the unlicensed frequencies.

7. A method for controlling device-to-device communication, the method comprising:

when transmitting data with device-to-device communications using licensed frequencies being frequencies of which a use is licensed for data transmission and sub-bands in unlicensed frequencies of which a use is not licensed for the data transmission to a reception terminal, receiving, using the transmission terminal, an allocation result of radio resources using the licensed frequencies and candidates for sub-bands of the unlicensed frequencies being determined that are in an idle status or have high possibility to be in the idle status by both of the transmission terminal and the reception terminal from a base station;

determining, using the transmission terminal, sub-bands of the unlicensed frequencies used for the data transmission by carrier sensing for the candidates for the sub-bands of the unlicensed frequencies; and

transmitting, using the transmission terminal, the allocation result of the radio resources using the licensed frequencies and an allocation result of the radio resources using the determined sub-bands of the unlicensed frequencies to the reception terminal.

8. A method for controlling transmission, the method comprising:

storing, using a base station, results of carrier sensing performed respectively by the base station and by a terminal with respect to at least one or more sub-bands in unlicensed frequencies being the frequencies of which a use is not licensed for transmitting data to the terminal;

extracting, using the base station, at least one or more sub-bands in the unlicensed frequencies determined that are in an idle status or have high possibility to be in the idle status by both of the base station and the terminal in the carrier sensing results as candidates for sub-bands of the unlicensed frequencies used for the base station to transmit the data to the terminal;

determining, using the base station, the sub-bands of the unlicensed frequencies used for the data transmission by the carrier sensing for the candidates for the sub-bands of the unlicensed frequencies; and

transmitting, using the base station, the allocation result of the radio sources using the determined sub-bands of the unlicensed frequencies to the terminal,

transmitting, using the base station, an allocation result of radio resources using licensed frequencies of which a use for the data transmission is licensed and candidates for the unlicensed frequencies to the transmission terminal and the reception terminal when device-to-device communications using the licensed frequencies is performed in addition to the device-to-device communications using the sub-bands in the unlicensed frequencies.