A mobile station device that receives downlink control information which is used to selectively provide downlink scheduling or a random access order, on a physical downlink control channel from a base station device. The mobile station device also transmits a random access preamble using a random access channel to the base station device based on receiving the downlink control information which provides a random access order, where the downlink control information provides a downlink resource allocation in a case that the downlink control information is used to provide the downlink scheduling and where a preset value is set for a field of the downlink resource allocation in a case that the downlink control information is used to provide the random access order.