Subsequently, a processor of the UE determines whether the first-stage uplink resource scheduling message (Trigger A) is valid or not in a first-stage uplink resource scheduling message validation. Thereby, the determination of the validity of this first-stage uplink resource scheduling message (Trigger A) is based on a determination as to whether an uplink transmission has been triggered by another second-stage uplink resource scheduling message (Trigger B) within a predetermined time period prior to reception of the second-stage uplink resource scheduling message (Trigger B).

Subsequently, it is determined by the processor, when receiving the second-stage uplink resource scheduling message (Trigger B), that an uplink transmission is scheduled in case the processor has determined that the first-stage uplink resource scheduling message (Trigger A) is valid.

Finally, in case the processor has determined that an uplink transmission is scheduled, a transmitter of the UE performs an uplink transmission via the unlicensed cell.

This main principle of the disclosure as described above advantageously allows preventing of multiple uplink transmission triggering in a multi-UE environment. Since there is no risk for unintentionally triggering, by a Trigger B that was intended for a different UE, a second uplink transmission by that particular UE that has already previously triggered an uplink transmission within the valid time window, the eNodeB can directly transmit a new Trigger A to different UEs right after having sent a Trigger B, even within the predetermined time period/valid time window.