ESM Error Code 50: type ipv4 only allowed (NRF91 Asset Tracker)

[Dominic]

Hi 

I am a bit stuck on this one. 

Hardware: NRF91 Thingy, NRF91 DK

Firmware: Asset Tracker with latest MFW v1.3.5

I have been connecting with 1oT SIM using NRF91Thingy and DK perfectly for the last 4 months - and it is usually the O2 cell tower (LTE-M Roaming) as there is no other tower nearby. I left it attached and logging on October 22nd 2023 and a few hours later disconnected, I have not been able to connect since. Every time I connect, or use AT+COPS it attaches then immediately detached with ESM 50 code - (PDN type IPv4 only allowed). I have contacted 1oT and they haven't reported anything with O2 network.

Modem trace as follows:

%CESQ: 32,1,16,2
+CEREG: 2,"02D0","07F87C78",7
+CSCON: 1
%CESQ: 33,1,9,1
%CESQ: 33,1,14,2
[00:00:01.534,149] <inf> app_event_manager: DATA_EVT_CONFIG_INIT
[00:00:01.935,821] <inf> app_event_manager: MODEM_EVT_LTE_CELL_UPDATE
+CGEV: ME PDN ACT 0,0
+CNEC_ESM: 50,0              <------- Error Code
%MDMEV: SEARCH STATUS 2
+CEREG: 5,"02D0","07F87C78",7,,,"11100000","11100000"
+CGEV: NW DETACH             <------- Detach
+CGEV: ME PDN DEACT 0
+CEREG: 2
%CESQ: 35,1,19,2

I have never seen this issue before and nothing has changed in the firmware since I started logging started. 1oT assume its hardware/firmware related - and suggested I changed the PDN context to use IPv4 only, same result. I also switched to IPv6, it gives a EMM 15 error in that case. We can connect to Vodafone just fine, but it is quite low signal, either way O2 has always been the closest and the best to connect to. 

Has anyone had similar issues? 

[Harald]

Dominic, you are welcome. I have been commissioned by more than one company to prepare a global roll-out with NB-IoT / LTE-M. The text for them will be a bit more extensive. I will be paid for my work. I have made part of the text available here for free.

As mentioned above, I have been aware of the problem since 2020. My customers do not have this problem. The Youtube video shows the blue parking spaces. It says that parking is only allowed for customers. Your parking ticket (SIM card) is not valid in the blue areas.

Besides the parking ticket, there are a few other things to consider with NB-IoT and LTE-M. All these things need to be clarified with your MVNO and/or the distributor of the radio module. They should know about the ticket, the fuel and the right tyres for your wireless car.

Email from 2020 MVNO to me: "We know that once Release 14 is rolled out, MNOs will prevent access to players connecting to LTE-M via their 4G roaming agreement.... and will insist on special LTE-M roaming agreements at a price favourable to the underlying MNO. .... This will spell the end for XYZ and all those customers who buy from XYZ today on the premise that they will be able to connect to LTE-M in the long term".

Others from 2020: "The 4G roaming agreements that inbound roamers may be using to access the LTE-M network today do not cover LTE-M and are therefore subject to change, both in terms of the availability of the LTE-M service and the associated commercial offers".

Otherwise, I recommend the 3GPP and GSMA documentation. It was clear that the UK was going to happen.

In Germany, we have seen that "those who always buy cheap often buy twice". You need different tickets now. I investigated four ticket sellers and then stopped. Either you were unlucky or you bought too cheap. I can't tell because I don't know how much you paid.

But be careful with fuel and tyres. The parking ticket is just one pitfall in a long chain of possible mistakes.

May roaming be with us.