B1-NR Measurement Report Problem for SgNB Addition

Hello Experts,

In NSA mode, after configuring the UE with B1-NR for SgNB Addition procedure, sometimes I don’t get measurement report from UE. What must be the problem, thank you.

  • I’ve checked the 5G signal in the air, it’s more than okay and I’ve already lowered the RSRP threshold to -130dBm just in case.

  • When Blind Addition switch is ON, UE never fails to decode SSB signal.

  • I can see that the UE is configured with relevant object, reporting, … in the RRC Connection Reconfiguration message. UE sends RRC Connection Reconfiguration Complete message to this configuration.

Did you check the neighbor definition from 4G towards 5G?
Every 4G cell should have defined 5G neighbors and this definition can take place at site level using X2 interface and on cell level using neighbor relations.

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Great suggestion! But I can see that there is X2 connection between eNB and gNB all the time. I get this relation info (global gNB ID and PLMN info of gNB) from the menu.

I use the same menu for Blind Addition and as I said UE never fails to decode NR SSB signal for Blind Addition.

You should have neighbors defined in cell level for measurement in addition to the X2 interface.
For blind case, neighbors on cell level is not needed as usually UE will move from 4G to the 5G co-located sector only without neighbors definition.

X2 Conn Info is for per UE so either addition is blind or measurement based, it requires the neighbor relation info. For the blind part, I meant X2 connection info but I could be more clearer.

Thank you for your contribution, I have managed to overcome this problem by changing RRU’s antenna. Now, I get B1-NR measurement report all the time when blind addition switch is OFF.

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Great, you solved your problem. So, it was only HW problem, good to know that, but was there any evidence showing the problem of the RRU antenna such as low RACH attempts, alarms, etc.?

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Well, the thing is that UE is replaced into a RF shield in order to prevent the interference in the lab. The antenna was also new to this new software development, so I wasn’t looking at somewhere else.

I’m working in a company which develops things from the scratch, unfortunately, there is no alarm system implemented for this purpose yet.

I got it now, I thought you are working in a live network.
It is clear now.

Yeah, we have around 2000 operational LTE Advanced RAN on the site. 5G BBU is the current challenge :slight_smile: