A mobile station device includes an information acquisition unit that is configured to and/or programmed to acquire information, which specifies a system bandwidth and a carrier frequency of a second downlink carrier component different from a first downlink carrier component, transmitted using RRC signaling via a physical downlink shared channel within the first downlink carrier component and a communication unit that is configured to communicate with the base station device by aggregate use of both the first downlink carrier component and the second downlink carrier component, where the first downlink carrier component and the second downlink carrier component have different carrier frequencies and each of the first downlink carrier component and the second downlink carrier component has its own downlink system bandwidth.