How many times a 5G SA phone tries the RA procedure with failure results by default?

5G NR
1

Hi all,
I just want to know how many times a 5G SA phone try to RACH with connection failure result knowing that the SIB1 does not have the connEstFailureControl set?.

I wonder if this default applies to all 5G SA phones with different modem makers.

Just to give more details about this RA question.

  1. During the initial acquisition procedure.
  2. The phone never receives the MSG2.
  3. I am asking about how many RA procedures are performed by UE before trying other cell, frequency, technology, etc., NOT about the number of times a preamble is sent (preambleTransMax) before declaring a single RA procedure failure.

Thanks a lot,

2

Hello, I also have query about 5G SA RACH procedure.

Assume UE send msg1 to gNB.

And somehow UE have failure on decoding msg2 (UE couldn’t decode msg2 on ra-window size).

Now… what will happen?

Will gNB re-send again rar?

And what will UE do on that case?

Will do RACH from beginning?

Another question: Shall initial RACH configuration be signaled to UE by sib1 configuration?

3

Yes.

Sample from L3:

5G SA RACH procedure
5G SA RACH procedure686×669 55.4 KB

4

Assume RAR failed.

What will UE do?

Will start RACH from msg1 again immediately?

5

Power ramping and Re-Rach if RAR not received within time window :window:

6

Check this → Why 2-Step RACH in 5G-NR (3GPP-R16)?

7

I’m not a 5G expert, yet I think it’s similar to what 4G device will do.

If the UE didn’t send the next MSG during RA window, the gNodeB will think the packet is lost and will just increase the power step in the next phase.

And do the same till all the power steps are finished, the procedure will begin from scratch.

Msg1 - preamble
Msg2 - RAR
Msg3 - RRC request

So if the UE didn’t reply with RRC request after the RAR, the gNodeB will asume the packet is lost as mentioned, and it will in crease the power and try again.