Radio base station, baseband processing apparatus, semiconductor integrated circuit, radio communication system and control method

1. A radio base station providing a service to a radio terminal by using plural component carriers, the radio base station comprising:

a scheduler configured to preferentially allocate, to the radio terminal, one of the component carriers that has a transmission power dynamic range that is defined by an upper limit value and a lower limit value and the lower limit value of which is lower than lower limit values of transmission power dynamic ranges of a rest of the component carriers; and

a transmitter configured to transmit a radio signal to the radio terminal by using the allocated component carrier.

2. The radio base station as claimed in claim 1 , further comprising:

a setting information transmitter configured to transmit setting information to the radio terminal before transmission of the radio signal using the allocated component carrier is started, wherein the setting information includes information indicating the allocated component carrier.

3. The radio base station as claimed in claim 1 , further comprising:

an operation state determinator configured to set the radio base station to one of a first operating state and a second operating state, wherein the first operating state indicates where lower limit values of the transmission power dynamic ranges of the plural component carriers are set to be substantially equal to each other, and wherein the second operating state indicates where lower limit values of the transmission power dynamic ranges of some of the plural component carriers are set to be lower than lower limit values of the transmission power dynamic ranges of a rest of the component carriers; and

a transmission power controller configured to reduce maximum transmission power values of some of the plural component carriers when the operation state determinator determines to change the first operating state to the second operating state,

wherein, in the second operating state, the scheduler is configured to preferentially allocate, to the radio terminal, one of the component carriers that has a transmission power dynamic range whose lower limit value is lower than lower limit values of the transmission power dynamic ranges of a rest of the component carriers.

4. The radio base station as claimed in claim 3 , further comprising:

a controller configured to permit radio communications using carrier aggregation that allocates plural component carriers to a radio terminal in the first operating state and to prevent the radio communications using the carrier aggregation in the second operating state.

5. The radio base station as claimed in claim 1 ,

wherein as the process of preferentially allocating, to the radio terminal, one of the component carriers that has the transmission power dynamic range whose lower limit value is lower than lower limit values of the transmission power dynamic ranges of the rest of the component carriers, the scheduler is configured to preferentially allocate, to the radio terminal, one of the component carriers that has a maximum transmission power value that is lower than maximum transmission power values of a rest of the component carriers.

6. The radio base station as claimed in claim 3 , further comprising:

an interface configured to receive a control signal from an upper node,

wherein the operation state determinator is configured to determine whether to set the radio base station to the second operating state by referring to at least one of the control signal from the upper node, a control signal from another radio base station, and information indicating traffic of another radio base station.

7. The radio base station as claimed in claim 3 ,

wherein the operation state determinator is configured to determine to set the radio base station to one of the first operating state and the second operating state based on at least one of traffic information, power resource information, power supply condition information, and external power supply information.

8. The radio base station as claimed in claim 3 , further comprising:

an interface configured to communicate with another radio base station,

wherein the operation state determinator is configured to determine whether to set the other radio base station to the first operating state or the second operating state, and

wherein, the interface is configured to report a result determined by the operation state determinator to the other radio base station.

9. The radio base station as claimed in claim 8 ,

wherein the operation state determinator is configured to cause a radio terminal, which is in a component carrier whose lower limit value of the transmission power dynamic range is to be reduce as a result of setting other radio base station to the second operating state, to be handed over to another component carrier.

10. A control method in a radio base station providing a service to a radio terminal by using plural component carriers, comprising:

preferentially allocating, to the radio terminal, one of the component carriers that has a transmission power dynamic range that is defined by an upper limit value and a lower limit value and the lower limit value of which is lower than lower limit values of transmission power dynamic ranges of a rest of the component carriers; and

transmitting a radio signal to the radio terminal by using the allocated component carrier.

11. A radio communication system comprising:

a radio terminal; and

a radio base station providing a service to the radio terminal by using plural component carriers,

wherein the radio terminal is configured to report reception quality of a downlink signal to the radio base station, and

wherein the radio base station includes:

a scheduler configured to preferentially allocate, to the radio terminal, one of the component carriers that has a transmission power dynamic range that is defined by an upper limit value and a lower limit value and the lower limit value of which is lower than lower limit values of transmission power dynamic ranges of a rest of the component carriers; and

a transmitter configured to transmit a radio signal to the radio terminal by using the allocated component carrier.