Abstract: A mobile station device that receives control information having a downlink control information format and addressed by a Cell-Radio Network Temporary Identifier 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 control information which provides a random access order. The downlink control information format includes a first field for downlink resource assignment. In a first case that the downlink control information form at is used for the random access order, a fixed value is set to the first field, while in a second case in which the downlink control information format is used for downlink scheduling, a first value different from the fixed value is set to the first field.