A mobile communication system that employs a frequency division duplex scheme, comprises: one or a plurality of UEs (200) that communicate with a serving cell; and a HeNB (100) that constitutes a first cell and a second cell, wherein the first cell uses a pair of first uplink carrier and downlink carrier for communication, the second cell uses a pair of a second uplink carrier and the downlink carrier for communication, and the HeNB (100) and the UE (200) switch a serving cell of the UE (200) between the first cell and the second cell by a handover procedure.