Congestion control for NR V2X

1. A method of wireless communication at a user equipment (UE), the method comprising:

determining a channel busy ratio (CBR) window for a CBR measurement for one or more resources;

determining a CBR measurement value for the CBR window and for the one or more resources;

determining a channel occupancy ratio (CR) window based on a first number of subframes used for a history of past transmissions and based on a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window does not exceed a subframe of a last planned retransmission of the future planned transmissions and corresponding retransmissions;

determining a CR value for the CR window based on subchannels used for the one or more resources for the first number of subframes and based on subchannels estimated for the one or more resources for the second number of subframes; and

performing a congestion control operation based on the CR value.

2. The method of claim 1 , wherein a last transmission of the future planned transmissions and corresponding retransmissions is a last retransmission of a currently scheduled transmission.

3. The method of claim 1 , wherein determining the CR window includes refraining from including future periodic transmissions scheduled by a previously received periodic grant in the second number of subframes.

4. The method of claim 1 , wherein the CR value corresponds to a particular subframe of the CR window, and wherein determining the CR value includes:

evaluating the particular subframe of the CR window based on a first number of subchannels used for the first number of subframes used for the history of the past transmissions of the CR window, based on a second number of subchannels used for the second number of subframes used for the future planned transmissions and corresponding retransmissions of the CR window to determine the CR value, and based on a total number of configured subchannels available for the one or more resources in the CR window.

5. The method of claim 1 , wherein the future planned transmissions and corresponding retransmissions include retransmissions of a currently scheduled transmission, wherein the retransmissions occur within a packet delay budget for each packet from generation of the currently scheduled transmission.

6. The method of claim 1 , wherein a maximum number of the retransmissions is based on HARQ feedback parameters.

7. The method of claim 1 , wherein the CR window is determined based further on a duration of the CBR window.

8. The method of claim 7 , wherein h duration of the CR window is ten times the duration of the CBR window.

9. The method of claim 1 , wherein the CBR measurement value is for a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), and a physical sidelink feedback channel (PSFCH).

10. The method of claim 1 , wherein determining the CR value for the CR window based on the CBR measurement value includes:

selecting the CR value from a table based on the CBR measurement value; or

calculating the CR value based on the CBR measurement value and a CR calculation formula.

11. The method of claim 1 , wherein the UE is operating in a physical sidelink control channel (PSCCH)/physical sidelink shared channel (PSSCH) multiplexing mode, and wherein a single CBR measurement is made for both the PSCCH and the PSSCH.

12. The method of claim 1 , wherein performing the congestion control operation based on the CR value includes performing one or more operations including adjusting an amount of subchannels to use for the one or more resources, adjusting an amount of retransmissions, adjusting a modulation coding scheme (MCS), adjusting a communication channel frequency, refraining from transmitting a communication during the CBR window, or a combination thereof.

13. The method of claim 1 , wherein the future planned transmissions and corresponding retransmissions comprise a currently planned transmission and corresponding retransmissions of the currently planned transmission, and further comprising:

receiving a scheduling message for the future planned transmissions and corresponding retransmissions prior to determining the CR window and the CR value,

determining the future planned transmissions and corresponding retransmissions based on the scheduling message prior to determining the CR window and the CR value.

14. The method of claim 1 , wherein the first number of subframes for the history of past transmissions is greater than half of the duration of the CR window, and wherein a sum of a subframe number for a current subframe and the second number of subframes is less than or equal to a subframe number corresponding to the last planned retransmission.

15. An apparatus configured for wireless communication at a user equipment (UE), the apparatus comprising:

one or more processors; and

a memory coupled to the one or more processors, with instructions stored in the memory and executable by the one or more processors to cause the apparatus to:

determine a channel busy ratio (CBR) window for a CBR measurement for one or more resources;

determine a CBR measurement value for the CBR window and for the one or more resources;

determine a channel occupancy ratio (CR) window based on a first number of subframes used for a history of past transmissions and based on a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window does not exceed a subframe of a last planned retransmission of the future planned transmissions and corresponding retransmissions;

determine a CR value for the CR window based on subchannels used for the one or more resources for the first number of subframes and based on subchannels estimated for the one or more resources for the second number of subframes; and

perform a congestion control operation based on the CR value.

16. The apparatus of claim 15 , wherein the duration of the CR window is 1000 milliseconds, and wherein the future planned transmissions and corresponding retransmissions comprise aperiodic transmissions, periodic transmissions, or both.

17. The apparatus of claim 15 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:

set a duration of the CBR window, the duration of the CR window, or both, based on a radio resource control (RRC) message.

18. The apparatus of claim 15 , wherein the first number of subframes for the history of past transmissions is greater than or equal to half of the duration of the CR window, and wherein the future planned transmissions and corresponding retransmissions represent actually scheduled transmissions or retransmission which take place after determining the CR window and the CR value.

19. The apparatus of claim 15 , wherein the instructions to determine the CR window further include instructions executable by the one or more processors to cause the apparatus to determine the CR window based on the following formula: a sum of a total number of used subchannels for subframes [n−a, n−1] and a total number of granted subchannels for subframes [n, n+b] is divided by total number of configured subchannels for subframes [n−a, n+b], where a+b+1=C, wherein ‘a’ corresponds to the first number subframes for the history of past transmissions to consider for the CR window, wherein ‘b’ corresponds to the second number of subframes for the future planned transmissions and corresponding retransmissions to consider for the CR window, and wherein ‘C’ is h duration of the CR window.

20. The apparatus of claim 19 , wherein the first number of subframes for the history of past transmissions to consider for the CR window is greater than or equal to half of the duration of the CR window, and wherein a sum of a current frame and the second number of subframes is less than or equal to a subframe number corresponding to a last retransmission of a current transmission.

21. The apparatus of claim 15 , wherein the instructions to determine the CBR measurement value further include instructions executable by the one or more processors to cause the apparatus to:

determine a Received Signal Strength Indicator (RSSI) value;

compare the RSSI value to a threshold;

determine that a resource is busy based on the RSSI value exceeding the threshold; and

determine the CBR measurement value based on a number of resources being busy divided by a total number of resources in the CBR window.

22. The apparatus of claim 15 , further comprising wherein the instructions are further executable by the one or more processors to cause the apparatus to:

determine the CBR measurement value independent of physical sidelink feedback channel (PSFCH) resources.

23. The apparatus of claim 15 , further comprising wherein the instructions are further executable by the one or more processors to cause the apparatus to:

determine a second CBR measurement value for physical sidelink feedback channel (PSFCH) resources based on a second CBR window for the PSFCH resources.

24. The apparatus of claim 23 , further comprising wherein the instructions are further executable by the one or more processors to cause the apparatus to:

determine the second CBR window for the PSFCH resources based on an RRC configurable parameter or a preconfigured second CBR window duration.

25. The apparatus of claim 23 , wherein the instructions to determine the second CBR measurement value for the PSFCH resources further include instructions executable by the one or more processors to cause the apparatus to:

determine a Received Signal Strength Indicator (RSSI) value for the PSFCH resources;

compare the RSSI value to a threshold;

determine that a resource of the PSFCH resources is busy based on the RSSI value exceeding the threshold; and

determine the second CBR measurement value based on a number of resources being busy divided by a total number of resources in the CBR window.

26. The apparatus of claim 15 , wherein the instructions are further executable by the one or more processors to cause the apparatus to:

determine the CBR measurement value based further on physical sidelink feedback channel (PSFCH) resources.

27. The apparatus of claim 15 , wherein the CBR measurement value is for a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), or both.

28. The apparatus of claim 15 , wherein the instructions to perform the congestion control operation based on the CR value further include instructions executable by the one or more processors to cause the apparatus to perform one or more operations including adjusting an amount of subchannels to use for the one or more resources, adjusting an amount of retransmissions, adjusting a modulation coding scheme (MCS), adjusting a communication channel frequency, refraining from transmitting a communication during the CBR window, or a combination thereof.

29. An apparatus configured for wireless communication at a user equipment (UE), the apparatus comprising:

means for determining a channel busy ratio (CBR) window for a CBR measurement for one or more resources;

means for determining a CBR measurement value for the CBR window and for the one or more resources;

means for determining a channel occupancy ratio (CR) window based on a first number of subframes used for a history of past transmissions and based on a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window does not exceed a subframe of a last planned retransmission of the future planned transmissions and corresponding retransmissions;

means for determining a CR value for the CR window based on subchannels used for the one or more resources for the first number of subframes and based on subchannels estimated for the one or more resources for the second number of subframes; and

means for performing a congestion control operation based on the CR value.

30. An apparatus configured for wireless communication at a user equipment (UE), the apparatus comprising:

one or more processors; and

a memory coupled to the one or more processors, with instructions stored in the memory and executable by the one or more processors to cause the apparatus to:

determine a channel busy ratio (CBR) window for a CBR measurement for one or more resources;

determine a CBR measurement value for the CBR window and for the one or more resources;

determine a channel occupancy ratio (CR) window based on a first number of subframes used for a history of past transmissions and based on a second number of subframes used for future planned transmissions and corresponding retransmissions, wherein a duration of the CR window does not exceed a subframe of a last planned retransmission of the future planned transmissions and corresponding retransmissions;

determine a CR value for the CR window based on subchannels used for the one or more resources for the first number of subframes and based on subchannels estimated for the one or more resources for the second number of subframes; and

refrain, based on the CR value, from transmitting a communication during the CBR window.