Mobile station, base station, and method for managing synchronization state

A mobile station that communicates with a base station by aggregating a plurality of cells having different frequency bands,

• wherein the plurality of cells having different frequency bands are grouped into any one of cell groups, each of which includes cells having an identical transmission timing, and
• wherein the mobile station
• adjusts the transmission timing of each of the cell groups which are set from the base station, and
• sets whether or not the transmission timing adjusted for each of the cell groups is to be applied after a handover, on the basis of information which describes for each of the cell groups whether or not the transmission timing before the handover is to be applied after the handover and which is transmitted from the base station.

A method for managing a synchronization state of a mobile station that communicates with a base station by aggregating a plurality of cells having different frequency bands,

• wherein the plurality of cells having different frequency bands are grouped into any one of cell groups, each of which includes cells having an identical transmission timing,
• the method comprising:
• adjusting, by using the mobile station, the transmission timing of each of the cell groups which are set from the base station;
• receiving, by using the mobile station, information describing whether or not a transmission timing before a handover for each of the cell groups is to be applied after the handover, from the base station, and storing the information;
• and
• applying, by using the mobile station, the transmission timing before the handover to the transmission timing after the handover, for the cell groups to which the transmission timing before the handover is to be applied after the handover.