How to tackle LTE triggered drops due to random access issues in 5G NSA

Hi Experts.

How to tackle this drops in 5G NSA → N.Nsadc.SgNB.Rel.MeNBTrigger.AbnormRel.ScgFail.RAProblem (LTE triggered drops due to random access issues).

Admin note: this post was updated with image below.

Increase your B1 threshold, avoid triggering NSA addition for short spikes of NR coverage, so play also with time to trigger.

But this will reduce your NR traffic.

B1 is standard, can’t change that.

As you know low NR traffic in initial phase so we need to do something else.

Increase dominance in NR.

What vendor do you have for NR?

Are you sure your RACH parameter template is correct and adapted to your cell radius?

If it is Huawei your NR vendor, can you please display those counters distribution?

Also can you please let us know what is the value of coverage scenario parameter in your network?

MO NRDUCellTrpBeam - Parameter CoverageScenario


For whole network is default?

There are 15 options for this parameter should be different by planner.

Anyway let’s come back to rach issue

Can you list here RACH parameters you use?

From an RRC reconfig to setup the SCG.

Should be something like this:

I don’t have the traces, but let me capture it.

Is it n78 or another band or DSS?




According to cell radius 5 km you zerocorrelationzoneconfig should be less than 8.
As you check in Book 5G New Radio in Bullets, page 297 - Table 169- Root Sequence Re-Use Pattern and Cell Range forr Subcarrier Spacing of 1.25 kHz (Unrestricted Cyclic Shift)

It is also important how you reuse the rootsequences for different cells.

This mobility control info… I think is for LTE not for NR.

You are not looking at correct RRC reconfig…

Oh yes, my mistake. It’s LTE :grin:

Is the one right before MIB in 5G, it is easy to find.

Just look for MIB in your trace.

I don’t have UE traces.

I am checking from U2020 directly.

Hey, I am unable to find the softcopy of this book. Do you have by any chance ? or can you please paste the table you are referring for this ?