RM520N-GL rrc setup fails

IoT Modules 5G Module
1

Hi,
We have RM520N-GL modem with RM520NGLAAR01A07M4G firmware.

In some modes of operation our BS, modem can see the cell, but didn’t attach:
at+qeng=“servingcell”
+QENG: “servingcell”,“LIMSRV”,“NR5G-SA”,“TDD”,001,01,000000013,157,1,647232,78,3,-79,-11,25,1,51

After analyzing the QXDM logs, our protocol team said:
“RRC setup fails because of non codebook SRS configuration”.

All other Qualcomm modems (but with x55 chipset) works fine with this mode of operation.
Maybe you have newest firmware, we can check it.

Is it possible to fix this bug. If you need QXDM file from modem, i can provide it.

Thanks,
Dmitry

RM502Q-AE Stuck on LIMSRV
2

After looking to AT+QCFG=“rrc” command, i found that default RRC is R9.
Our protocol team said, in this specific mode we use RRC R15.

Is it possible to check this ussie?

Thanks,
Dmitry

3

Hi,

I also have LIMSRV on RM520N-GL but with LTE network.
Could you please share how to log collect to catch issue during RRC registration in the network?
If it is possible in router part…
May be you can provide recommendation how to try to solve the issue…

Thx!

4

Hi Anton,

If you have LTE network, it is different case. If you have commercial network, it may be better return to auto MBN selection.

I don’t think it router part, but try to check if APN set correctly on modem with command:
at+cgdcont?

In the past we have router, that transfer “IPV4V6” instead of “IP”, and this also was a problem.

We are developing our 5G SA BS, so we use many different modes of operations, that currently new at all, and may be not present in modem firmware.
The LIMSRV may have very many reasons, so my case isn’t yours at all.
For my case i need Quectel team to look on my QXDM logs, and help me with this.

To collect QXDM logs, you need Quectel QLog tool, or dedicated debug USB port from the modem.
If you don’t have dedicated USB port, you need QLog compiled and installed on router. Also, Quectel tool for windows, to collect the QXDM logs.
And for log analyze, you need QXDM tool.

5

Thanks, I will try to solve my issue…

6

Hi Dmitry,

Did you fix the LIMSRV issue?

Thanks,
Andrew

7

Hi Andrew,
“LIMSRV” isn’t issue, it modem state. Why modem stay in that state - it may be million reasons, and need investigate each one.
Do you try to connect to commercial network?
Is APN set correctly?
What is you FW version?
What is your location? (some modems and version have limitation to connect)
Try to manually setup module (with at-commands, and not with some applications) and try manually register to network.

BTW, in my case, we have private network, and this mode still not solved. But this is Qualcomm issue, and not Quectel. We try to solve it

Thanks!

8

Hi dgel27
I hope you are doing well.
I am currently deploying a private 5G SA laboratory network with the following setup:

  • 5G Core: Open5GS

  • RAN: OpenAirInterface (OAI) with USRP B210

  • PLMN: 00101

  • SIM cards: Sysmocom programmable SIMs

  • Network type: 5G SA

  • DNN/APN: private DNN configured in Open5GS

The same Sysmocom SIM works correctly on a smartphone and attaches successfully to the private network.
But when using the RM520N-GL, the module does not attach to the network and does not obtain an IP address.
AT+QENG=“servingcell”
+QENG: “servingcell”,“LIMSRV”,“NR5G-SA”,“TDD”,001,01,000BC614E,0,1,663360,77,6,-95,-10,16,1,34

OK

Since the module works well on public networks, we suspect that the issue may be related to firmware restrictions or configuration related to:

  • PLMN 00101
  • Private 5G SA networks
  • Open-source 5G cores (Open5GS)

Our project goal is to connect IoT sensors (temperature, gas, etc.) to an Arduino, then from the Arduino to the RM520 module, and transmit the sensor data over our private 5G network to a server for data visualization and analysis.

Could you please advise:

  1. Whether PLMN 00101 and private 5G SA networks are supported on this firmware?
  2. If any special firmware, NV configuration, or AT commands are required to enable private 5G SA operation?
  3. If there are known limitations with Open5GS/OAI interoperability?

Thank you very much for your support.

Best regards,

Lydia

9

Dear @maiz
Please share your current firmware and check the response of AT command below:
AT+QMBNCFG=“list”
AT+QNWPREFCFG=“nr5g_band”
AT+QNWPREFCFG=“ue_capability_band”

10

Dear silivia , sorry for the delay ,

please find below the requested information .

ATI

Quectel
RM520N-GL
Revision: RM520NGLAAR03A03M4G

OK
AT+QMBNCFG=“list”

+QMBNCFG: “List”,0,0,0,“ROW_Commercial”,0x0A010809,202401151
+QMBNCFG: “List”,1,0,0,“ROW_Generic_3GPP_PTCRB_GCF”,0x0A01FF09,: “List”,23,0,0,“Commercial-LGU”,0x0A012608,202111051
+QMBNCFG: “List”,24,0,0,“Commercial-KT”,0x0A01280B,202308031
+QMBNCFG:
AT+QNWPREFCFG=“nr5g_band”

+QNWPREFCFG: “nr5g_band”,78

OK
AT+QNWPREFCFG=“ue_capability_band”

+QNWPREFCFG: “gw_band”,1:2:4:5:8:19
+QNWPREFCFG: “lte_band”,0
+QNWPREFCFG: “nsa_nr5g_band”,1:2:3:5:7:8:12:13:14:18:20:25:26

Please let me know if you need any additional information or further tests.

11

Dear @maiz
It seems you had configured to n78, but the network is n77.
You can try these AT commands as below:
AT+QNWPREFCFG=“nr5g_band”,77
AT+QMBNCFG=“Deactivate”
AT+QMBNCFG=“Autosel”,0
AT+QMBNCFG=“Select”,“ROW_Commercial”
AT+CFUN=0
AT+CFUN=1

12

Dear Silvia,

As requested, I executed the AT command sequence to align the RM520N-GL configuration with band n77 and reset the MBN selection. Please find below the exact commands executed and the observed behavior.

AT commands executed

AT+QNWPREFCFG="nr5g_band",77
OK

AT+QMBNCFG="Deactivate"
OK

AT+QMBNCFG="Autosel",0
OK

AT+QMBNCFG="Select","ROW_Commercial"
OK

AT+CFUN=0
OK
AT+CFUN=1
OK

After this procedure, the module reboots correctly, but the UE still does not attach to the OAI 5G SA network .

The OAI 5G SA network is operational: the same Sysmocom SIMs successfully attach on commercial smartphones** using the same PLMN, gNB, and core.
With the Quectel RM520N-GL, the modem camps on the cell in NR5G-SA (band n77), but the attachment does not complete
gNB logs show a failure during the Random Access procedure at Msg3 (WAIT_Msg3, max HARQ rounds reached), before NAS registration
At this stage, it is unclear whether the issue is due to a Sysmocom SIM interoperability issue with this modem or a compatibility/UL configuration issue between the RM520N-GL and OAI 5G SA

13

Dear @maiz
Please capture log for analysis.