Enhancements for improved CV2X scheduling and performance
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, techniques for improving semi-persistent scheduling performance, including in the context of cellular vehicle-to everything (CV2X) communications, are provided. For example, a method of wireless communication performed by a user equipment can include determining a first periodicity for transmitting safety messages, determining a second periodicity for transmitting the safety messages, wherein the second periodicity is different than the first periodicity, determining, based on a probabilistic determination process, whether to continue with the first periodicity or switch to the second periodicity, generating, based on the determination to continue with the first periodicity or switch to the second periodicity, the safety messages at the first periodicity or the second periodicity, and transmitting the safety messages at a same periodicity at which the safety messages were generated. Numerous other aspects are provided.
1. A method of wireless communication performed by a user equipment, the method comprising:
determining, based on at least a distributed congestion control algorithm, a first periodicity for transmitting safety messages;
determining, based on at least the distributed congestion control algorithm, a second periodicity for transmitting the safety messages, wherein the second periodicity is different than the first periodicity;
determining, based on a probabilistic determination process, whether to continue with the first periodicity or switch to the second periodicity;
generating, based on the determination to continue with the first periodicity or switch to the second periodicity, the safety messages at the first periodicity or the second periodicity; and
transmitting the safety messages at a same periodicity at which the safety messages were generated.
2. The method of claim 1 , further comprising:
requesting, in response to determining to switch to the second periodicity, a modem of the user equipment to change to the second periodicity prior to sending, to the modem, a last safety message packet generated at the first periodicity.
3. The method of claim 1 , wherein:
the first periodicity is a first supported semi-persistent scheduling (SPS) periodicity of a plurality of supported SPS periodicities; and
the second periodicity is a second supported SPS periodicity of the plurality of supported SPS periodicities.
4. The method of claim 3 , wherein the plurality of supported SPS periodicities include SPS periodicities associated with Sidelink PC5.
5. The method of claim 3 , wherein at least one of the determining the first periodicity or the determining the second periodicity includes rounding a safety message generation periodicity determined by the distributed congestion control algorithm to the first supported SPS periodicity or the second supported SPS periodicity.
6. The method of claim 5 , wherein the distributed congestion control algorithm is an SAE distributed congestion control algorithm and the safety message generation periodicity is a maximum inter-transmission time (MAX_ITT).
7. The method of claim 3 , further comprising:
detecting a tracking error; and
generating, based on the detected tracking error, a tracking error-based safety message separate from the plurality of supported SPS periodicities.
8. The method of claim 7 , further comprising:
refraining from generating a safety message during a scheduled generation time period associated with the first periodicity or the second periodicity when the tracking error-based safety message is generated within a threshold amount of time of the scheduled generation time period.
9. The method of claim 8 , wherein the threshold amount of time is based on a packet delay budget.
10. The method of claim 7 , further comprising:
generating a safety message during a scheduled generation time period when the tracking error-based safety message is generated within a threshold amount of time of the scheduled generation time period and the scheduled generation time period is associated with a change in the first periodicity or a change in the second periodicity.
11. The method of claim 1 , wherein the probabilistic determination process is weighted towards the first periodicity.
12. The method of claim 1 , wherein:
the determining whether to continue with the first periodicity or switch to the second periodicity comprises determining to continue with the first periodicity; and
the generating the safety messages at the first periodicity or the second periodicity comprises generating the safety messages at the first periodicity.
13. The method of claim 12 , further comprising:
determining a third periodicity for transmitting the safety messages, wherein the third periodicity is different than the first periodicity;
determining, based on the probabilistic determination process, whether to continue with the first periodicity or switch to the third periodicity; and
generating, based on the determination to continue with the first periodicity or switch to the third periodicity, the safety messages at the first periodicity or the third periodicity.
14. The method of claim 1 , wherein:
the determining whether to continue with the first periodicity or switch to the second periodicity comprises determining to switch to the second periodicity; and
the generating the safety messages using the first periodicity or the second periodicity comprises communicating the safety messages at the second periodicity.
15. The method of claim 1 , wherein the determining the first periodicity for transmitting the safety messages comprises:
rounding a first calculated periodicity to the first periodicity.
16. The method of claim 15 , wherein the rounding the first calculated periodicity to the first periodicity comprises rounding the first calculated periodicity to at least one of a supported SPS periodicity of a specification or a multiple of a 100-millisecond periodicity.
17. The method of claim 15 , wherein the determining the second periodicity for transmitting the safety messages comprises:
rounding a second calculated periodicity to the second periodicity.
18. The method of claim 17 , wherein the rounding the second calculated periodicity to the second periodicity comprises rounding the second calculated periodicity to the second periodicity based on a hysteresis parameter.
19. The method of claim 18 , further comprising:
randomly selecting a value for the hysteresis parameter from a set of available values for the hysteresis parameter.
20. The method of claim 18 , wherein the hysteresis parameter is a percentage of a gap between the first periodicity and an adjacent supported periodicity.
21. The method of claim 18 , wherein the rounding the second calculated periodicity to the second periodicity based on a hysteresis parameter comprises:
determining the second calculated periodicity is
less than (T n +T n−1 )/2−(T n −T n−1 )*H or
greater than (T n +T n+1 )/2+(T n+1 −T n )*H,
where T n is the first periodicity, T n−1 is a supported periodicity less than the first periodicity, T n+1 is a supported periodicity greater than the first periodicity, and H is the hysteresis parameter.
22. The method of claim 1 , wherein the determining whether to continue with the first periodicity or switch to the second periodicity occurs at a scheduled packet generation time period associated with the first periodicity and prior to transmission of a packet generated at the scheduled packet generation time period.
23. A method of wireless communication performed by a user equipment, the method comprising:
determining, based on at least a distributed congestion control algorithm, a first semi-persistent scheduling (SPS) periodicity for generating safety messages;
determining, based on at least the distributed congestion control algorithm, a second SPS periodicity for generating the safety messages, the second SPS periodicity being greater than the first SPS periodicity;
selecting a random time offset; and
generating a first safety message associated with the second SPS periodicity based on the random time offset.
24. The method of claim 23 , wherein the selecting the random time offset comprises:
randomly selecting a time between 0 and the second SPS periodicity.
25. The method of claim 24 , wherein the generating the first safety message associated with the second SPS periodicity comprises:
generating the first safety message after the random time offset from a current time based on the random time offset being greater than or equal to a threshold value.
26. The method of claim 25 , wherein the generating the first safety message associated with the second SPS periodicity comprises:
generating the first safety message after the second SPS periodicity from the current time based on the random time offset being less than the threshold value.
27. The method of claim 26 , further comprising:
generating, following the first safety message, subsequent safety messages associated with the second SPS periodicity based on the second SPS periodicity.
28. A user equipment, comprising:
a processor configured to:
determine, based on at least a distributed congestion control algorithm, a first periodicity for transmitting safety messages;
determine, based on at least the distributed congestion control algorithm, a second periodicity for transmitting the safety messages, wherein the second periodicity is different than the first periodicity;
determine, based on a probabilistic determination process, whether to continue with the first periodicity or switch to the second periodicity; and
generate, based on the determination to continue with the first periodicity or switch to the second periodicity, the safety messages at the first periodicity or the second periodicity; and
a modem in communication with the processor, the modem configured to:
transmit the safety messages at a same periodicity at which the safety messages were generated.
29. The user equipment of claim 28 , wherein:
the first periodicity is a first supported semi-persistent scheduling (SPS) periodicity of a plurality of supported SPS periodicities;
the plurality of supported SPS periodicities include SPS periodicities associated with Sidelink PC5;
the second periodicity is a second supported SPS periodicity of the plurality of supported SPS periodicities; and
the processor is further configured to:
detect a tracking error;
generate, based on the detected tracking error, a tracking error-based safety message separate from the plurality of supported SPS periodicities;
request, in response to determining to switch to the second periodicity, the modem to change to the second periodicity prior to sending a last safety message packet generated at the first periodicity to the modem; and
determine at least one of the first periodicity or the second periodicity by rounding a safety message generation periodicity determined by the distributed congestion control algorithm executed by the processor to the first supported SPS periodicity or the second supported SPS periodicity.
30. A user equipment, comprising:
a processor configured to:
determine, based on at least a distributed congestion control algorithm, a first semi-persistent scheduling (SPS) periodicity for generating safety messages;
determine, based on at least the distributed congestion control algorithm, a second SPS periodicity for generating the safety messages, the second SPS periodicity being greater than the first SPS periodicity;
select a random time offset; and
generate a first safety message associated with the second SPS periodicity based on the random time offset.