User equipment and base station involved in improved discontinued reception for unlicensed cells

A base station, which in operation, communicates with a user equipment via an unlicensed radio cell of a mobile communication system, the base station comprising:

• a receiver and processing circuitry, which in operation, perform a clear channel assessment for a downlink channel of the unlicensed radio cell to determine whether the base station can occupy the downlink channel to perform downlink transmissions;
• a transmitter, which in operation and when the base station can occupy the downlink channel, transmits a channel occupancy signal on the downlink channel of the unlicensed radio cell to the user equipment, wherein the channel occupancy signal indicates that the base station occupies the downlink channel to perform downlink transmissions;
• the transmitter, which in operation, transmits to the user equipment downlink control information regarding a downlink transmission to be received by the user equipment;
• and
• the transmitter, which in operation, transmits a downlink transmission to the user equipment based on the received downlink control information,
• wherein the processing circuitry, when in operation, determines whether the user equipment monitors, during a first time period, the downlink channel of the unlicensed radio cell for the channel occupancy signal that is transmitted by the base station,
• wherein the processing circuitry, when in operation, determines whether the user equipment monitors, during a second time period, the downlink channel of the unlicensed radio cell for downlink control information, and
• wherein the transmitter transmits the downlink control information to the user equipment during the second time period when determining that the user equipment monitors during a second time period the downlink channel for the downlink control information.

A method comprising the following steps performed by a user equipment:

• monitoring, during a first time period, a downlink channel of an unlicensed radio cell for a channel occupancy signal that is transmitted by a base station communicating with the user equipment via the unlicensed radio cell of a mobile communication system, wherein the channel occupancy signal indicates that the base station occupies the downlink channel to perform downlink transmissions;
• receiving the channel occupancy signal during the first time period from the base station;
• determining that the base station occupies the downlink channel based on the received channel occupancy signal;
• after determining that the base station occupies the downlink channel, monitoring, during a second time period, the downlink channel for downlink control information regarding a downlink transmission to be received by the user equipment;
• and
• receiving the downlink control information during the second time period and receives subsequently the downlink transmission from the base station based on the received downlink control information.