Why device don't stay in SA?

One of my device under 5G coverage does not stay in SA and falls back to NSA while the other device stays in SA, what can be the reason ? or can I consider the first device has some issues.

Note : Both the devices are at same location, same coverage and same PCI.

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Did you try to swap the SIM from working device to not working device?

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Yes, I tried. :+1:

SIM card issue is ruled out.

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What do you mean by does not stay?

Does UE attach SA cell and then move to LTE?

Can you check UE logs how it is going to LTE?

I mean, by handover or LTE or redirection?

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Did you see any difference in call flow between working and not working?

I have set the preferred network type to 5G Auto on both the device and toggled airplane mode.

There is no data running in background (Mobile Data is kept ON) ----- after few seconds the device1 is still on 5G SA network.

Where as the device2 is leaving 5G SA and attaching to 5G NSA network (LTE + NR).

As per device 2 Logs… I can see RRC Reconfiguration which contains master cell group info, uplink config.

Then I can see LTE MIB SIB and Tracking area update.

Whereas Device1 is in SA and idle state.

Did you observe any MobilityFromNr command just before TAU request?

No I didn’t observe.

Are device 1 and 2 both iPhone models?

I suggest set both to 5G On mode and try.

5G auto is iPhone algoritthm which decides either 5G is to used or not, only only 4G.

I have similar issue but not about 5G auto mode, some devices search and camp SA only when its rat mode set to NR only.

Whiles others do not require such thing.

NR/LTE and 5G preferred is enough for device to look for SA first.

From log, how you concluded that device-2 is in NSA?

Device2 logs show tracking area update …after that you have RRC messages showing NR leg added.

To be more specific, like you have spcell config.

Seems iPhone specific algorithm.

By “Others” do you mean Android phone?

Hi Swanand,

It means either Ue did not complete registration in SA or may be one of the PDU session is rejected so gNB would have released the Ue from SA NW. Once it reads the MIB/SIB of LTE and if can complete TAU then it will go to NSA. But wondering if it’s in NSA and Ue is in SA mode then eNB should trigger back the Ue to SA/NSA nw, based on the timer you have set in the node. either blind RWR or measurement based HO should trigger, check eNB settings as well . Please lock Ue to SA mode only and check whether all the registration process is complete or not .