Method and apparatus for contention window size adjustment for psfch transmission

A second user equipment (UE) for wireless communication, comprising:

• at least one memory;
• and
• at least one processor coupled with the at least one memory and configured to cause the second UE to:
• transmit, to a first UE, a first physical sidelink shared channel (PSSCH);
• transmit, to the first UE, a second sidelink control information (SCI) format scheduling a second PSSCH, wherein the second SCI format includes an indicator indicating how to adjust a second contention window size (CWS) for the first UE to perform a second channel access procedure for transmitting a second physical sidelink feedback channel (PSFCH) carrying hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for the second PSSCH, and wherein the indicator is determined based on whether a first PSFCH carrying HARQ-ACK feedback for the first PSSCH is correctly received by the second UE or not;
• and
• transmit, to the first UE, the second PSSCH.

A first user equipment (UE) for wireless communication, comprising:

• at least one memory;
• and
• at least one processor coupled with the at least one memory and configured to cause the first UE to:
• receive, from a second UE, a physical sidelink shared channel (PSSCH);
• determine, based on a default setting or an occupancy state of a channel, a contention window size (CWS) for the first UE to perform a channel access procedure for transmitting a physical sidelink feedback channel (PSFCH) carrying hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for the PSSCH;
• perform the channel access procedure on the channel using the CWS;
• and
• transmit, to the second UE, the PSFCH in response to the channel access procedure being successful.

A method performed by a first user equipment (UE), the method comprising:

• receiving, from a second UE, a first physical sidelink shared channel (PSSCH);
• transmitting, to the second UE, a first physical sidelink feedback channel (PSFCH) carrying hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for the first PSSCH;
• receiving, from the second UE, a second PSSCH;
• determining, based on whether the first PSFCH is correctly received by the second UE or not, a second contention window size (CWS) for the first UE to perform a second channel access procedure for transmitting a second PSFCH carrying HARQ-ACK feedback for the second PSSCH;
• and
• performing the second channel access procedure using the second CWS.