What is the technical challenge in having low band 5G NR & LTE simultaneously?

Hello Experts,

What is the technical challenge in having low band 5G NR & LTE simultaneously?

And why mid band LTE is preferred as anchor for 5G NSA?
Why low band (600Mhz) LTE cannot be used as anchor for mmwave 5G?

We have done our first SA drive test last week, device was TMO S20+ and had 600MHz 5G NR SA and 600Mhz/2130Mhz LTE, the phone stayed in 5G-NR SA and after got released and redirected to LTE once data transfer was over > To my surprise the device didn’t went to NSA even when 2130 Mhz LTE (mid band anchor as mentioned in the Flash report)coverage was good .

No idea.
US phones have special bands combos so very different than europe phones.

So my question is, Knowing that a recent firmware upgrade happened in this device, even if the Chipset supports both SA & NSA, can this firmware upgrade suppress the device from using NSA? ANd secondly can I identify this in FGI or something?

The FW upgrade was OTA.

Ideally why would a UE manufacturer limit UE from using NSA?

Whether the UEe will use 5G SA or 5G NSA is entirely network decision.
FW upgrades do not remove NSA.

Yes it can be possible.
DCNR disable and remove LTE+NR capability.

FW upgrade is Operator customised.
If operator doesn’t need specific device to use features it can get restricted through FGI on /off right?
If this specific device got SA functionality once after a FW upgrade, then I think I have to believe this new FW upgrade did something to NSA capability as per my observation.

Another doubt in same subject here:

What can be the network setting which allows the phone to use SA only when NSA anchored LTE goes below an RSRP threshold and when LTE anchor goes above the thrshold the UE uses NSA?

Also: second observation is that my SA-NSA capable device goes to SA only when I do Airplane mode on off and reinitiate attach, else it stays in LTE only without even attempting NSA SCG addition. How to check what is the cell search priority?

Check sib 24 in lte: there you will find 5G NR priorities and subpriorities.
For SA, I mean.

I couldn’t get SIBs in LTE. After 30s in LTE airplane mode test started and went to SA.
Have asked for a longer test in LTE tmrw.

If no sib24 broadcasted, then no reselection from 4G to 5G SA.

But I know the fact that when LTE cov is below some RSRP threshold then SA is allowed.

Have you noticed any handover/reselection between SA and NSA in logs at low RSRP?

We are trying to get something like this:

There should be IRAT handover.
What option you have for SA?
Option2 or option7?

We have Option2.

Yeah, that’s the real 5G SA. :slight_smile:

Yes but 5Mhz BW in n71.
The thing is NSA along with LTE5CA is far far better than this 5Mhz SA.

We haven’t tested the latency yet to see the real SA benefit here.
Choosing the latency measurement points is another challenge.

5GC with SA is deployed for URLLC, mMTC, reduced ping and RTT.
Not for eMBB.

Yes, correct.