A user equipment and method used in a user equipment include receiving from a base station, a message including information indicating a first logical channel associated with one or more first cells, information indicating a second logical channel 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. When transmitting data of the specific bearer, the data it transmitted by using the first logical channel in response to a volume of the data not exceeding a threshold value configured by the base station, and the data is transmitted by using the first logical channel and the second logical channel in response to the volume of the data exceeding the threshold value. A base station transmits the message and configures the threshold.