Random access channel (RACH) procedure power control

1. A method for wireless communication by a user equipment (UE), comprising:

determining a transmit power for transmitting a first message to a base station (BS) as part of a two-step random access channel (RACH) procedure, the first message comprising a first part comprising a RACH preamble and a second part comprising a radio resource control (RRC) connection request, wherein determining the transmit power comprises:

determining a first transmit power for transmitting the first part based on a first function having parameters including a power ramping counter and a power ramping step; and

determining a second transmit power for transmitting the second part based on a second function having parameters including the power ramping counter and the power ramping step, wherein one or more of the parameters of one or more of the first function or the second function are a function of a payload type for which the user equipment is performing RACH, and wherein the one or more of the parameters of the one or more of the first function or the second function change from a first transmission of the first message to a second transmission of the first message based on a change in payload of the first message from the first transmission to the second transmission;

transmitting the first message to the BS using the determined transmit power; and

incrementing the power ramping counter based on transmitting the first message.

2. The method of claim 1 , further comprising:

determining a third transmit power for transmitting the first part as part of a four-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure; and

determining a fourth transmit power for transmitting the second part as part of the four-step RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure.

3. The method of claim 2 , further comprising:

determining a fifth transmit power for transmitting the first part as part of a four-step fall back RACH procedure after falling back from the two-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure; and

determining a sixth transmit power for transmitting the second part as part of the four-step fall back RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure.

4. The method of claim 1 , wherein the payload type is based on one or more of a quality of service, priority flow, or reason for connection request.

5. The method of claim 1 , further comprising falling back to a four-step RACH procedure based on one or more of the first transmit power reaching a first maximum power or the second transmit power reaching a second maximum power.

6. The method of claim 1 , further comprising falling back to a four-step RACH procedure, wherein the power ramping counter is maintained after the falling back.

7. The method of claim 6 , wherein the power ramping step has a first value for the two-step RACH procedure and a second value for the four-step RACH procedure.

8. The method of claim 1 , further comprising:

incrementing a single transmit counter for each retransmission of the first message;

determining if the single transmit counter has reached a first threshold;

falling back to a four-step RACH procedure when the single transmit counter reaches the first threshold; and

declaring a RACH failure when the single transmit counter reaches a second threshold.

9. A user equipment comprising:

a memory; and

a processor coupled to the memory, the processor configured to:

determine a transmit power for transmitting a first message to a base station (BS) as part of a two-step random access channel (RACH) procedure, the first message comprising a first part comprising a RACH preamble and a second part comprising a radio resource control (RRC) connection request, wherein to determine the transmit power comprises to:

determine a first transmit power for transmitting the first part based on a first function having parameters including a power ramping counter and a power ramping step; and

determine a second transmit power for transmitting the second part based on a second function having parameters including the power ramping counter and the power ramping step, wherein one or more of the parameters of one or more of the first function or the second function are a function of a payload type for which the user equipment is performing RACH, and wherein the one or more of the parameters of the one or more of the first function or the second function change from a first transmission of the first message to a second transmission of the first message based on a change in payload of the first message from the first transmission to the second transmission;

transmit the first message to the BS using the determined transmit power; and

increment the power ramping counter based on transmitting the first message.

10. The user equipment of claim 9 , wherein the processor is further configured to:

determine a third transmit power for transmitting the first part as part of a four-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure; and

determine a fourth transmit power for transmitting the second part as part of the four-step RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure.

11. The user equipment of claim 10 , wherein the processor is further configured to:

determine a fifth transmit power for transmitting the first part as part of a four-step fall back RACH procedure after falling back from the two-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure; and

determine a sixth transmit power for transmitting the second part as part of the four-step fall back RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure.

12. The user equipment of claim 9 , wherein the payload type is based on one or more of a quality of service, priority flow, or reason for connection request.

13. The user equipment of claim 9 , wherein the processor is further configured to fall back to a four-step RACH procedure based on one or more of the first transmit power reaching a first maximum power or the second transmit power reaching a second maximum power.

14. The user equipment of claim 9 , wherein the processor is further configured to fall back to a four-step RACH procedure, wherein the power ramping counter is maintained after the falling back.

15. The user equipment of claim 14 , wherein the power ramping step has a first value for the two-step RACH procedure and a second value for the four-step RACH procedure.

16. The user equipment of claim 9 , wherein the processor is further configured to:

increment a single transmit counter for each retransmission of the first message;

determine if the single transmit counter has reached a first threshold;

fall back to a four-step RACH procedure when the single transmit counter reaches the first threshold; and

declare a RACH failure when the single transmit counter reaches a second threshold.

17. A user equipment comprising:

means for determining a transmit power for transmitting a first message to a base station (BS) as part of a two-step random access channel (RACH) procedure, the first message comprising a first part comprising a RACH preamble and a second part comprising a radio resource control (RRC) connection request, wherein determining the transmit power comprises:

determining a first transmit power for transmitting the first part based on a first function having parameters including a power ramping counter and a power ramping step; and

determining a second transmit power for transmitting the second part based on a second function having parameters including the power ramping counter and the power ramping step, wherein one or more of the parameters of one or more of the first function or the second function are a function of a payload type for which the user equipment is performing RACH, and wherein the one or more of the parameters of the one or more of the first function or the second function change from a first transmission of the first message to a second transmission of the first message based on a change in payload of the first message from the first transmission to the second transmission;

means for transmitting the first message to the BS using the determined transmit power; and

means for incrementing the power ramping counter based on transmitting the first message.

18. The user equipment of claim 17 , further comprising:

means for determining a third transmit power for transmitting the first part as part of a four-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure; and

means for determining a fourth transmit power for transmitting the second part as part of the four-step RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure.

19. The user equipment of claim 18 , further comprising:

means for determining a fifth transmit power for transmitting the first part as part of a four-step fall back RACH procedure after falling back from the two-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure; and

means for determining a sixth transmit power for transmitting the second part as part of the four-step fall back RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure.

20. The user equipment of claim 17 , wherein the payload type is based on one or more of a quality of service, priority flow, or reason for connection request.

21. The user equipment of claim 17 , further comprising means for falling back to a four-step RACH procedure based on one or more of the first transmit power reaching a first maximum power or the second transmit power reaching a second maximum power.

22. The user equipment of claim 17 , further comprising means for falling back to a four-step RACH procedure, wherein the power ramping counter is maintained after the falling back.

23. The user equipment of claim 22 , wherein the power ramping step has a first value for the two-step RACH procedure and a second value for the four-step RACH procedure.

24. The user equipment of claim 17 , further comprising:

means for incrementing a single transmit counter for each retransmission of the first message;

means for determining if the single transmit counter has reached a first threshold;

means for falling back to a four-step RACH procedure when the single transmit counter reaches the first threshold; and

means for declaring a RACH failure when the single transmit counter reaches a second threshold.

25. A non-transitory computer-readable medium that comprises instructions that when executed by a user equipment (UE), cause the UE to perform a method for wireless communication, the method comprising:

determining a transmit power for transmitting a first message to a base station (BS) as part of a two-step random access channel (RACH) procedure, the first message comprising a first part comprising a RACH preamble and a second part comprising a radio resource control (RRC) connection request, wherein determining the transmit power comprises:

determining a first transmit power for transmitting the first part based on a first function having parameters including a power ramping counter and a power ramping step; and

determining a second transmit power for transmitting the second part based on a second function having parameters including the power ramping counter and the power ramping step, wherein one or more of the parameters of one or more of the first function or the second function are a function of a payload type for which the user equipment is performing RACH, and wherein the one or more of the parameters of the one or more of the first function or the second function change from a first transmission of the first message to a second transmission of the first message based on a change in payload of the first message from the first transmission to the second transmission;

transmitting the first message to the BS using the determined transmit power; and

incrementing the power ramping counter based on transmitting the first message.

26. The non-transitory computer-readable medium of claim 25 , the method further comprising:

determining a third transmit power for transmitting the first part as part of a four-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure; and

determining a fourth transmit power for transmitting the second part as part of the four-step RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure.

27. The non-transitory computer-readable medium of claim 26 , the method further comprising:

determining a fifth transmit power for transmitting the first part as part of a four-step fall back RACH procedure after falling back from the two-step RACH procedure based on the first function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure; and

determining a sixth transmit power for transmitting the second part as part of the four-step fall back RACH procedure based on the second function having possible different values for one or more of the parameters than for the two-step RACH procedure and the four-step RACH procedure.