A mobile communication system in which a plurality of cells configured to perform radio communication with a movable user equipment device are operated, wherein - the plurality of cells include a cell configured to perform coordinated communication and to perform radio communication with the user equipment device in a coordinated manner with another cell, - among the plurality of cells, a serving cell that is adapted to control the user equipment device is adapted to configure a radio resource management, RRM, measurement set and to notify the user equipment device of the RRM measurement set that has been configured, the RRM measurement set being a collection of cells to be subjected to a process of detecting, by the user equipment device, whether or not radio communication is allowed, - the mobile communication system comprises an adjustment unit that is adapted to adjust the coordinated communication, - the adjustment unit is adapted to configure a Coordinated MultiPoint, CoMP, cooperating set and a CoMP measurement set and to notify the user equipment device of the CoMP cooperating set and the CoMP measurement set that have been configured, the CoMP cooperating set being a collection of cells to become candidates on which the user equipment device is adapted to perform a process of detecting whether or not the coordinated communication is allowed among the cells in the RRM measurement set, the CoMP measurement set being a collection of cells to be subjected to a process of detecting whether or not the coordinated communication is allowed among the cells in the CoMP cooperating set, - the serving cell is adapted to request a cell other than the serving cell of the cells included in the CoMP measurement set to join the CoMP measurement, and - wherein the user equipment device (a) is adapted to perform, when being notified of the CoMP measurement set from the adjustment unit, the process of detecting whether or not the coordinated communication is allowed on each of the cells in the CoMP measurement set, and (b) is adapted to perform, when being notified of the CoMP cooperating set and not being notified of the CoMP measurement set from the adjustment unit, the process of detecting whether or not the coordinated communication is allowed on each of the cells in the CoMP cooperating set. - the plurality of cells include a cell configured to perform coordinated communication and to perform radio communication with the user equipment device in a coordinated manner with another cell, - among the plurality of cells, a serving cell that is adapted to control the user equipment device is adapted to configure a radio resource management, RRM, measurement set and to notify the user equipment device of the RRM measurement set that has been configured, the RRM measurement set being a collection of cells to be subjected to a process of detecting, by the user equipment device, whether or not radio communication is allowed, - the mobile communication system comprises an adjustment unit that is adapted to adjust the coordinated communication, - the adjustment unit is adapted to configure a Coordinated MultiPoint, CoMP, cooperating set and a CoMP measurement set and to notify the user equipment device of the CoMP cooperating set and the CoMP measurement set that have been configured, the CoMP cooperating set being a collection of cells to become candidates on which the user equipment device is adapted to perform a process of detecting whether or not the coordinated communication is allowed among the cells in the RRM measurement set, the CoMP measurement set being a collection of cells to be subjected to a process of detecting whether or not the coordinated communication is allowed among the cells in the CoMP cooperating set, - the serving cell is adapted to request a cell other than the serving cell of the cells included in the CoMP measurement set to join the CoMP measurement, and - wherein the user equipment device (a) is adapted to perform, when being notified of the CoMP measurement set from the adjustment unit, the process of detecting whether or not the coordinated communication is allowed on each of the cells in the CoMP measurement set, and (b) is adapted to perform, when being notified of the CoMP cooperating set and not being notified of the CoMP measurement set from the adjustment unit, the process of detecting whether or not the coordinated communication is allowed on each of the cells in the CoMP cooperating set. (a) is adapted to perform, when being notified of the CoMP measurement set from the adjustment unit, the process of detecting whether or not the coordinated communication is allowed on each of the cells in the CoMP measurement set, and (b) is adapted to perform, when being notified of the CoMP cooperating set and not being notified of the CoMP measurement set from the adjustment unit, the process of detecting whether or not the coordinated communication is allowed on each of the cells in the CoMP cooperating set.