Method and apparatus for contention window size adaptation of nr unlicensed

A base station (BS) in a wireless communication system, the BS comprising:

• a processor configured to:
• determine a reference time duration for a channel occupancy starting from a beginning of a previous downlink transmission burst until an end of a first slot in the channel occupancy, wherein at least one unicast physical downlink shared channel (PDSCH) included in the previous downlink transmission burst is transmitted to a user equipment (UE),
• identify a set of hybrid automatic repeat request-acknowledge/negative acknowledge (HARQ-ACK/NACK) feedbacks corresponding to the at least one unicast PDSCH transmission in the reference time duration,
• adjust, based on the identified set of HARQ-ACK/NACK feedbacks, a contention window size (CWS) associated with a channel access procedure, wherein:
• the channel access procedure includes a time duration spanned by a number of sensing slots,
• the number of sensing slots is random and based on a counter, and
• the counter is generated based on the CWS;
• and
• perform the channel access procedure before a next downlink transmission burst;
• and
• a transceiver operably coupled to the processor, the transceiver configured to transmit, via a downlink channel, the next downlink transmission burst, upon successfully performing the channel access procedure.