Radio terminal and base station communicate simultaneously through a plurality of cells

A base station comprising:

• a processor and a memory coupled to the processor, wherein
• the processor is configured to perform a process of transmitting to a user equipment a message including information indicating a first logical channel associated with one or more first cells, information indicating a second logical channel associated with one or more second cells, and information associating the first logical channel and the second logical channel with a specific bearer of the user equipment, and
• the processor is configured to perform a process of configuring a threshold value to the user equipment so that, when transmitting data of the specific bearer, the user equipment transmits the data by using the first logical channel in response to a volume of the data not exceeding the threshold value, and transmits the data by using both of the first logical channel and the second logical channel in response to the volume of the data exceeding the threshold value.