Method and apparatus for receiving UE to perform power saving operation based on PSFCH in NR V2X

1. A method for performing, by a first apparatus, wireless communication, the method comprising:

obtaining a sidelink (SL) discontinuous reception (DRX) configuration including information related to an SL DRX hybrid automatic repeat request (HARQ) round trip time (RTT) timer value;

receiving sidelink control information (SCI) for scheduling of a physical sidelink shared channel (PSSCH) through a physical sidelink control channel (PSCCH) from a second apparatus, based on an active time of the SL DRX configuration;

receiving a medium access control (MAC) protocol data unit (PDU) of the PSSCH from the second apparatus, based on the active time; and

starting an SL DRX HARQ RTT timer, based on that a physical sidelink feedback channel (PSFCH) resource is configured to an SL grant related to the SCI and a HARQ feedback related to the MAC PDU is disabled,

wherein the SL DRX HARQ RTT timer is started in a slot following an end of the transmission through the PSSCH, based on that the SCI includes information related to a retransmission resource of the MAC PDU, and

wherein the SL DRX HARQ RTT timer is started in a slot following an end of the PSFCH resource and runs as long as the SL DRX HARQ RTT timer value, based on that the SCI does not include information related to a retransmission resource of the MAC PDU.

2. The method of claim 1 , further comprising:

receiving a retransmission of the MAC PDU, based on that the SL HARQ RTT timer is expired and the retransmission resource.

3. The method of claim 2 , wherein the step of receiving the retransmission of the MAC PDU includes:

starting an SL HARQ retransmission timer, based on that the SL HARQ RTT timer is expired; and

receiving the retransmission of the MAC PDU, based on that the SL HARQ retransmission timer is running and the retransmission resource.

4. The method of claim 1 , further comprising:

transmitting HARQ NACK information related to the MAC PDU to the second apparatus, based on the active time.

5. The method of claim 1 , wherein the first apparatus doesn't perform a monitoring for a PSCCH of a PSSCH, based on that the SL HARQ RTT timer is running.

6. The method of claim 5 , wherein the PSCCH or the PSSCH, for which the monitoring is not performed based on that the SL HARQ RTT timer is running, is related to an SL HARQ process related to the MAC PDU.

7. The method of claim 1 , wherein the SL DRX HARQ RTT timer runs from the next slot of the end of the transmission through the PSSCH until before the retransmission resource time point, based on that the SCI includes the information related to the retransmission resource of the MAC PDU.

8. The method of claim 1 , further comprising:

determining that the retransmission resource of the MAC PDU exists after 32 slots from the SCI, based on that the SCI doesn't include the information related to the retransmission resource of the MAC PDU.

9. The method of claim 7 , wherein the first apparatus operates in a sleep mode from a time of transmission of the SCI to a time of the PSFCH resource, based on that the MAC PDU is a HARQ enabled MAC PDU.

10. The method of claim 1 , wherein the active timer includes an SL DRX on-duration timer and an SL DRX inactivity timer.

11. The method of claim 1 , wherein the active time is a time during which the active timer is running.

12. The method of claim 1 , wherein the SL DRX configuration is obtained through a PC5RRC message.

13. A first apparatus for performing wireless communication, the first apparatus comprising:

one or more memories storing instructions;

one or more transceivers; and

one or more processors connected to the one or more memories and the one or more transceivers, wherein the one or more processors execute the instructions to:

obtain a sidelink (SL) discontinuous reception (DRX) configuration including information related to an SL DRX hybrid automatic repeat request (HARQ) round trip time (RTT) timer value;

receive sidelink control information (SCI) for scheduling of a physical sidelink shared channel (PSSCH) through a physical sidelink control channel (PSCCH) from a second apparatus, based on an active time of the SL DRX configuration;

receive a medium access control (MAC) protocol data unit (PDU) of the PSSCH from the second apparatus, based on the active time; and

start an SL DRX HARQ RTT timer, based on that a physical sidelink feedback channel (PSFCH) resource is configured to an SL grant related to the SCI and a HARQ feedback related to the MAC PDU is disabled,

wherein the SL DRX HARQ RTT timer is started in a slot following an end of the transmission through the PSSCH, based on that the SCI includes information related to a retransmission resource of the MAC PDU, and

wherein the SL DRX HARQ RTT timer is started in a slot following an end of the PSFCH resource and runs as long as the SL DRX HARQ RTT timer value, based on that the SCI does not include information related to a retransmission resource of the MAC PDU.

14. An apparatus configured to control a first user equipment (UE), the apparatus comprising:

one or more processors; and

one or more memories operably connectable to the one or more processors and storing instructions, wherein the one or more processors execute the instructions to:

obtain a sidelink (SL) discontinuous reception (DRX) configuration including information related to an SL DRX hybrid automatic repeat request (HARQ) round trip time (RTT) timer value;

receive sidelink control information (SCI) for scheduling of a physical sidelink shared channel (PSSCH) through a physical sidelink control channel (PSCCH) from a second UE, based on an active time of the SL DRX configuration;

receive a medium access control (MAC) protocol data unit (PDU) of the PSSCH from the second UE, based on the active time; and

start an SL DRX HARQ RTT timer, based on that a physical sidelink feedback channel (PSFCH) resource is configured to an SL grant related to the SCI and a HARQ feedback related to the MAC PDU is disabled,

wherein the SL DRX HARQ RTT timer is started in a slot following an end of the transmission through the PSSCH, based on that the SCI includes information related to a retransmission resource of the MAC PDU, and

wherein the SL DRX HARQ RTT timer is started in a slot following an end of the PSFCH resource and runs as long as the SL DRX HARQ RTT timer value, based on that the SCI does not include information related to a retransmission resource of the MAC PDU.