Method and apparatus transmitting sidelink CSI

1. A method of transmitting sidelink (SL) channel state information (CSI) by a first apparatus, the method comprising:

generating the SL CSI related to a channel state between the first apparatus and a second apparatus in a medium access control (MAC) control element (CE) format; and

transmitting the SL CSI in the MAC CE format to the second apparatus through MAC layer signaling,

wherein the generating of the SL CSI in the MAC CE format and the transmitting of the SL CSI in the MAC CE format to the second apparatus are triggered by sidelink physical (PHY) layer signaling from the second apparatus related to triggering of the transmitting of the SL CSI in the MAC CE format.

2. The method of claim 1 , wherein a priority for the SL CSI of the MAC CE format is predetermined.

3. The method of claim 1 , further comprising transmitting a first scheduling request (SR) to a base station, wherein the first SR is triggered by the SL CSI in the MAC CE format, generated by the PHY layer signaling from the second apparatus related to the triggering of the transmitting of the SL CSI.

4. The method of claim 3 , further comprising receiving an SL grant from the base station, wherein the SL CSI is transmitted to the second apparatus through the MAC CE on an SL resource related to the SL grant.

5. The method of claim 4 , wherein the SL grant is related to the first SR transmitted to the base station.

6. The method of claim 4 , further comprising:

transmitting a second SR to the base station;

receiving a UL grant from the base station; and

transmitting the SL CSI to the base station on a UL resource related to the UL grant.

7. The method of claim 6 , wherein the SL CSI is transmitted to the base station through the MAC CE on the UL resource.

8. The method of claim 7 , wherein the SL CSI is transmitted to the base station, further based on at least one of cases (i) where the SL resource is reselected, (ii) where an SL channel busy ratio (CBR) value is increased compared to a predetermined threshold, (iii) where a reference signal received power (RSRP) value is increased compared to a predetermined threshold, (iv) where the RSRP value is increased compared to a predetermined threshold, (v) where a received signal strength indicator (RSSI) value is increased compared to a predetermined threshold, (vi) where an SL CQI value is increased compared to a predetermined threshold, (vii) where an SL PMI value is increased compared to a predetermined threshold, (viii) where an SL RI value is increased compared to a predetermined threshold, or (ix) where a PC5 RRC connection is established between user equipments (UEs).

9. The method of claim 6 , wherein the UL grant is related to the second SR.

10. The method of claim 1 , wherein the SL CSI includes at least one of a channel quality indicator (CQI), a precoding matrix indicator (PMI), or a rank indicator (RI).

11. The method of claim 1 , wherein the transmitting of the SL CSI to the second apparatus comprises:

determining an SL resource for transmitting the SL CSI to the second apparatus, based on resource selection; and

transmitting the SL CSI to the second apparatus through the MAC CE, based on the SL resource.

12. A first apparatus configured to transmit sidelink (SL) channel state information (CSI), the first apparatus comprising:

at least one memory storing instructions;

at least one transceiver; and

at least one processor connected to the at least one memory and the at least one transceiver,

wherein the at least one processor is configured to:

generate the SL CSI related to a channel state between the first apparatus and a second apparatus in a medium access control (MAC) control element (CE) format; and

control the at least one transceiver to transmit the SL CSI in the MAC CE format to the second apparatus through MAC layer signaling,

wherein the generating of the SL CSI in the MAC CE format and the transmitting of the SL CSI in the MAC CE format to the second apparatus are triggered by sidelink physical (PHY) layer signaling from the second apparatus related to triggering of the transmitting of the SL CSI in the MAC CE format.

13. A processing device configured to control a first terminal to transmit sidelink (SL) channel state information (CSI), the processing device comprising:

at least one processor; and

at least one computer memory operably connectable to the at least one processor, and storing instructions that, based on being executed by the at least one processor, perform operations comprising:

generating the SL CSI related to a channel state between the first terminal and a second terminal in a medium access control (MAC) control element (CE) format; and

transmitting the SL CSI in the MAC CE format to the second terminal through MAC layer signaling,

wherein the generating of the SL CSI in the MAC CE format and the transmitting of the SL CSI in the MAC CE format to the second terminal are triggered by sidelink physical (PHY) layer signaling from the second terminal related to triggering of the transmitting of the SL CSI in the MAC CE format.