| 主权项 |
1. A base station, comprising:
a transmitter which transmits data to a radio terminal using a plurality of frequency bands in a carrier aggregation; a transfer circuit which transfers a part of data to be transmitted in the transmitter to another base station so that data transmission to the radio terminal is performed in said another base station, a storage which stores a plurality of frequency bands with which the radio terminal, the base station and said another base station are able to perform communication; a selector which selects, out of the plurality of frequency bands stored, frequency bands with which the radio terminal is able to perform radio communication with the base station and said another base station; and a monitor which makes the radio terminal monitor whether radio communication is able to be performed with the base station and said another base station with the frequency bands selected by the selector; wherein: the transmitter starts data transmission with a first frequency band to the radio terminal, when both or one of a retention amount and a retention time of data to be transmitted to the radio terminal exceeds a threshold value, the monitor instructs the radio terminal to start monitoring of different-frequency bands which are different from a current frequency band by which the radio terminal is communicating, when the base station receives a first monitoring result with a first detection notification of a second frequency band from the radio terminal which is different from the first frequency band and is used by the base station, the transmitter transmits the data using both the first frequency band and the second frequency band to the radio terminal, so that the base station adds the second frequency band of the base station to the first frequency band of the base station and performs the data transmission to the radio terminal, when both or one of the retention amount and the retention time exceeds the threshold value and the base station receives a second monitoring result with a second detection notification of a third frequency band used by the another base station from the radio terminal, the monitor instructs the radio terminal to stop monitoring of the different-frequency bands and the transfer circuit starts to transfer the part of data to the another base station, and the part of data transferred by the transfer circuit is transmitted to the radio terminal with the third frequency band different from the first frequency band and the second frequency band by the another base station, so that the base station adds the third frequency band of the another base station to the first frequency band of the base station and performs the data transmission to the radio terminal. |
