SMS fails to be delivered on iPhones

Devices
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1

Hello Everyone.

I’d like to discuss a specific behavior that we’re seeing on our network with iPhones.

On our network we only have 4G/5G with VoWiFi, VoLTE and VoNR technologies.

However, iPhones are homologated to operate on 4G, 5GNSA, VoWiFi, VolTE on our network.

The failure is related to receiving SMSoIP over VoLTE/VoWiFi.

We did some traces, and we saw that the SMS is forwarded to the terminal, but the UE responds a “Not Found” to the network and the SMS fails to be delivered.

For us, this doesn’t make much sense, as the mobile it is registered with the IMS and receives/makes calls and also can send an SMS.

I would like to know if anyone has had this problem and how it was resolved.

SMS fails to be delivered on iPhones
SMS fails to be delivered on iPhones1024×1024 59.7 KB

2

Are you using sim cards holding more than one imsi and impu?

3

We’re using one imsi, but with 3 types of impu.

4

We are currently facing similar issue with iPhones.

For multiple impu subs.

Still troubleshooting…

5

Do you believe it is related to a specific PUI that the iPhone does not accept?

6

No, I think it is related with multiple impu config.

Since no issues with subscribers with single IMPU in our case.

I think UE somehow skips the IMPU list.

7

Hmmm, it makes sense.

I’ll try to understand these parameters better.

If you have any updates on your troubleshooting, please let us know.

8

Sure, please let us know if you also find something.

9

Another thing, were you able to find any pattern in these failures?

Terminal model, iOS version or something like that?

I’m asking this because we haven’t been able to find this pattern here yet, as it only happens in some specific terminals, and they have no relationship with each other.

10

Currently we have iphone only as problematic UE.

We don’t have live traffic yet catched this issue during testing phase.

So unfortunately not enough data to create a pattern.

11

Sorry but can I ask for which operator and RAN you observed the issue?

12

We’re a new operator here in Brazil.

For now, we only have a few cities commercially with Huawei’s RAN having this problem.

However, in the next months we will have other vendors running, and it will be possible to say if we will have the same problem.

Got it!

The same scenario here, our the traffic also is still small, and we haven’t found the pattern.