The invention relates to a user equipment (UE) scheduled with uplink radio resources. At least one unlicensed cell is configured for communication between the UE and a base station (BS). The UE receives from the BS a first-stage uplink scheduling message. The UE determines whether the first-stage uplink scheduling message is valid, which comprises determining that it is valid in case one or more bits of one or more data fields in the first-stage uplink scheduling message are set to respectively predetermined values. The UE receives from the BS a second-stage uplink scheduling message related to the first-stage uplink scheduling message. The UE determines, when receiving the second-stage uplink scheduling message, that an uplink transmission is scheduled in case it determined that the first-stage uplink scheduling message is valid. The UE then performs, in case it determined that an uplink transmission is scheduled, an uplink transmission via the unlicensed cell.