In order to carry out high-speed packet communications using a large-volume transmission channel like an E-DCH, uplink communication quality must be good. However, in a state in which a link imbalance occurs, a mobile station cannot estimate the uplink communication quality from downlink communication quality. Therefore, the mobile station calculates a path loss from the setting power of a common pilot channel which is notified from a base station, and the received power of the common pilot channel received thereby, and also estimates the received power in the base station on the basis of this path loss. The mobile station further judges the uplink communication quality by estimating the SIR in the base station by using the interference power notified from the base station and the estimated received power.