Apparatus and method for controlling congestion in wireless communication system

1. A method performed by a terminal in a wireless communication system, the method comprising:

determining a plurality of granted transmission resources for a sidelink communication;

performing a transmission or a retransmission using at least one transmission resource among the plurality of granted transmission resources;

receiving an acknowledgement (ACK) for the transmission or the retransmission;

in response to the ACK, releasing one or more transmission resources among the plurality of granted transmission resources;

measuring a channel occupancy ratio (CR) from transmission resources other than the released one or more transmission resources from the plurality of granted transmission resources; and

transmitting a physical sidelink shared channel (PSSCH) to satisfy a condition that the measured CR does not exceed a configured CR limit so that a congestion control is performed.

2. The method of claim 1 ,

wherein the CR is a value of a total number of subchannels used for transmission by the terminal in slots [n−a, n−1] and subchannels granted to be used in slots [n, n+b] divided by a total number of configured subchannels in a transmission pool in slots [n−a, n+b],

wherein a is a positive integer, b is 0 or a positive integer, a+b+1=M,

wherein M is included in resource pool configuration information, and

wherein n, a, and b indicate numbers associated with a physical slot index.

3. The method of claim 2 ,

wherein M is 1000 or 1000·2 μ slots, and

wherein μ is an index for numerology, and is related to subcarrier spacing (SPS).

4. The method of claim 1 , further comprising:

measuring a channel busy ratio (CBR) from orthogonal frequency division multiplexing (OFDM) symbols configured for a physical sidelink control channel (PSCCH) and a PSSCH of the sidelink communication,

wherein the CR limit is associated with the measured CBR.

5. The method of claim 4 ,

wherein the CBR is a ratio of subchannels in which a sidelink received signal strength indicator (SL RSSI) is measured by the terminal exceed a threshold value which is configured or preconfigured in slots [n−a, n−1],

wherein a is a time window size for the CBR,

wherein a is included in resource pool configuration information, and

wherein n and a indicate numbers associated with a physical slot index.

6. The method of claim 5 ,

wherein a is 1000 or 1000·2 μ slots, and

wherein μ is an index for numerology, and is related to subcarrier spacing (SPS).

7. The method of claim 4 ,

wherein, when at least one physical sidelink feedback channel (PSFCH) resource is configured, the at least one PSFCH resource is excluded from the measurement of the CBR.

8. A terminal in a wireless communication system, the terminal comprising:

a transceiver; and

at least one processor configured to:

determine a plurality of granted transmission resources for a sidelink communication,

perform a transmission or a retransmission using at least one transmission resource among the plurality of granted transmission resources,

receive an acknowledgement (ACK) for the transmission or the retransmission,

in response to the ACK, release one or more transmission resources among the plurality of granted transmission resources,

measure a channel occupancy ratio (CR) from transmission resources other than the released one or more transmission resources from the plurality of granted transmission resources, and

transmit a physical sidelink shared channel (PSSCH) to satisfy a condition that the measured CR does not exceed a configured CR limit so that a congestion control is performed.

9. The terminal of claim 8 ,

wherein the CR is a value of a total number of subchannels used for transmission by the terminal in slots [n−a, n−1] and subchannels granted to be used in slots [n, n+b] divided by a total number of configured subchannels in a transmission pool in slots [n−a, n+b],

wherein a is a positive integer, b is 0 or a positive integer, a+b+1=M,

wherein M is included in resource pool configuration information, and

wherein n, a, and b indicate numbers associated with a physical slot index.

10. The terminal of claim 9 ,

wherein M is 1000 or 1000·2 μ slots, and

wherein μ is an index for numerology, and is related to subcarrier spacing (SPS).

11. The terminal of claim 8 ,

wherein the at least one processor is further configured to:

measure a channel busy ratio (CBR) from orthogonal frequency division multiplexing (OFDM) symbols configured for a physical sidelink control channel (PSCCH) and a PSSCH of the sidelink communication, and

wherein the CR limit is associated with the measured CBR.

12. The terminal of claim 11 ,

wherein the CBR is a ratio of subchannels in which a sidelink received signal strength indicator (SL RSSI) is measured by the terminal exceed a threshold value which is configured or preconfigured in slots [n−a, n−1],

wherein a is a time window size for the CBR,

wherein a is included in resource pool configuration information, and

wherein n and a indicate numbers associated with a physical slot index.

13. The terminal of claim 12 ,

wherein a is 1000 or 1000·2 μ slots, and

wherein μ is an index for numerology, and is related to subcarrier spacing (SPS).

14. The terminal of claim 11 ,

wherein, when at least one physical sidelink feedback channel (PSFCH) resource is configured, the at least one PSFCH resource is excluded from the measurement of the CBR.