5G Unlicensed Carrier Sensing Contention Window Adjustment

The patent applies preliminary action by having the gNB perform carrier sensing and determine the contention window size (CWS) before UE transmission. The gNB sends downlink data bursts and HARQ-ACK feedback to establish timing reference, enabling the UE to perform uplink carrier sensing at the correct timing. This preliminary gNB action prevents timing misalignment collisions between gNB and UE transmissions.

The patent uses feedback mechanisms where the gNB receives HARQ-ACK feedback from UE and uses this information to adjust the CWS for subsequent carrier sensing. The gNB counts ACKs and NACKs from multiple downlink data bursts and dynamically adjusts CWS based on the feedback ratio, improving channel access fairness and reducing collisions through adaptive control.

The patent segments the HARQ-ACK feedback management by introducing a reference Downlink HARQ process that serves as the basis for CWS adjustment. Instead of managing all HARQ-ACK processes equally, the system identifies a reference process (typically the first one) and uses its HARQ-ACK feedback as the primary basis for CWS determination, simplifying the management complexity while maintaining efficiency.

The patent applies local quality by allowing different HARQ processes to have different CWS values based on their specific feedback conditions. Each downlink data burst can have its own CWS adjustment based on its HARQ-ACK feedback, enabling fine-grained control of channel access for different data bursts while using the reference process as the primary control point.