Messaging for random access procedures

1. A method of wireless communication, comprising:

repeatedly transmitting, from a mobile device to a communication node, a first message using increasing power levels for initiating a two-step random-access procedure until a termination condition is met, wherein the first message includes a payload part and a preamble sequence,

wherein transmitting the first message includes:

incrementing a first counter tracking a number of repeated transmissions of the payload part;

incrementing a second counter tracking a power ramping level corresponding to the repeated transmissions of the payload part;

and wherein the termination condition includes: the first counter tracking the number of repeated transmission of the payload part reaches a first threshold;

reselecting, by the mobile device, the preamble sequence upon determining that the first counter reaches the first threshold, wherein a number of times the preamble sequence is reselected is less than a second threshold;

transmitting, from the mobile device, a second message to the communication node, wherein the second message includes the reselected preamble sequence and the payload part;

incrementing a third counter tracking the number of times the preamble sequence is reselected; and

incrementing a fourth counter tracking a preamble power ramping level corresponding to the reselected preamble sequence.

2. The method of claim 1 , comprising:

detecting, by the mobile device, a transmission failure of the payload part, wherein the transmission failure is detected by receiving, at the mobile device, an indication from the communication node, wherein the indication includes a non-acknowledgement (NACK) or a dynamic grant indicating retransmission opportunities in a time-frequency domain.

3. The method of claim 1 , comprising:

detecting, by the mobile device, a transmission failure of the payload part, wherein the transmission failure is detected upon a determination that the mobile device fails to receive an indication from the communication node within a time-domain response window.

4. The method of claim 1 , comprising:

receiving, prior to initiating the random-access procedure, a configuration message from the communication node, wherein the configuration message includes a field to indicate whether a two-step random-access procedure or a four-step random-access procedure is to be used.

5. The method of claim 1 , wherein the termination condition is met when receiving an indication indicting a successful reception of the payload part from the communication node.

6. The method of claim 1 , wherein the first counter and the second counter are initialized after the reselecting of the preamble sequence.

7. The method of claim 2 , wherein the indication indicates the NACK or the dynamic grant within a same channel occupancy time (COT).

8. The method of claim 2 , further comprising, after receiving the indication, performing, by the mobile device, multiple listen before talk (LBT) attempts according to the dynamic grant.

9. The method of claim 3 , wherein the time-domain response window is configured by the communication node for the mobile device.

10. An apparatus of wireless communication apparatus, comprising

a memory;

a processor configured to: repeatedly transmit, to a communication node, a first message using increasing power levels for initiating a two-step random-access procedure until a termination condition is met, wherein the first message includes a payload part and a preamble sequence,

wherein the first message is transmitted by the processor further configured to:

increment a first counter tracking a number of repeated transmissions of the payload part;

increment a second counter tracking a power ramping level corresponding to the repeated transmissions of the payload part;

and wherein the termination condition includes: the first counter tracking the number repeated transmission of the payload part reaches a first threshold;

reselect the preamble sequence upon determining that the first counter reaches the first threshold, wherein a number of times the preamble sequence is reselected is less than a second threshold;

transmit a second message to the communication node, wherein the second message includes the reselected preamble sequence and the payload part;

increment a third counter tracking the number of times the preamble sequence is reselected; and

increment a fourth counter tracking a preamble power ramping level corresponding to the reselected preamble sequence.

11. The apparatus of claim 10 , wherein the processor is configured to:

detect a transmission failure of the payload part, wherein the transmission failure is detected by receiving an indication from the communication node, wherein the indication includes a non-acknowledgement (NACK) or a dynamic grant indicating retransmission opportunities in a time-frequency domain.

12. The apparatus of claim 10 , wherein the processor is configured to:

detect a transmission failure of the payload part, wherein the transmission failure is detected upon a failure to receive an indication from the communication node within a time-domain response window.

13. The apparatus of claim 10 , wherein the processor is configured to:

receive, prior to initiating the random-access procedure, a configuration message from the communication node, wherein the configuration message includes a field to indicate whether a two-step random-access procedure or a four-step random-access procedure is to be used.

14. The apparatus of claim 10 , wherein the termination condition is met when receiving an indication indicting a successful reception of the payload part from the communication node.

15. The apparatus of claim 10 , wherein the first counter and the second counter are initialized after the reselecting of the preamble sequence.

16. The apparatus of claim 11 , wherein the indication indicates the NACK or the dynamic grant within a same channel occupancy time (COT).

17. The apparatus of claim 11 , further comprising, after receiving the indication, performing multiple listen before talk (LBT) attempts according to the dynamic grant.

18. The apparatus of claim 12 , wherein the time-domain response window is configured by the communication node.