Intermittent Fails when UE try to attach to the 5G NSA network

5G NR
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1

Hello experts, anyone has some ideas about it?

Context: it is a problem in a 5G NSA Network.

The measurement is static, and when the UE try to attach to the 5G NSA network, send some preambles and the preambules fails (aborted).
The UE does not receive msg2. Then fail the attach to the Network.

But some time later (some sec), try to acces, send the preamble, receive msg2, and so on… and do the acces to the 5G NSA Network satisafctory.

The measurement is on same cell 4G/ 5G.

Some idea, what could happen?

2

If this would be a case in LTE, then I could say due to high PRB utilization there is prach collision.
Or low power head room UE side.
Or low SS attached attempt.

But as this is 5G-NSA, I don’t think your site would be suffering from high PRB utilization, hence omitting this possibility.

Mostly there is variations of signal strength at testing end.
Have to check this way.

Even if there should be any prach parameter issue as well, otherwise it will keep repeating the failure event.

3
  1. Set b1threshold align with rsrpssbthreshold for rach preamble.
  2. Check number of preambles per ssb parameter in your vendor.
  3. Raresponsewindow supervises the reception of msg2 when it is expired ue waits for next prach occasion and retries msg1.
  4. Check preambletransmax determines how many times UE tries msg1.
  5. Also your prach conf index determines your periodicity of msg 2 slot.