Unstable connection + TCP duplicate ACK (disconnection)

Technical Subjects
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1

I am encountering instability issues with a Quectel RM502Q-AE module, mounted on a SIXFAB board, within a private 5G Standalone (SA) network environment powered by the srsRAN project. The setup utilizes sysmocom SIM cards for network access.

While the UDP connectivity appears stable, allowing for successful iperf tests and UDP streaming, TCP connections, including website access and TCP iperf tests, trigger module reboots and frequent disconnections. This issue persists despite successful connectivity to the srsRAN 5G network, and is not present with other User Equipment (UE) devices under the same network conditions, post-APN configuration.

Setup details:
PC running on Ubunutu 22.04 with srsRAN GNB installed

RM502q-AE on top of SIXFAB connected to th ePC through USB C

Debug commands:

**AT+GMR**
`RM502QAEAAR11A04M4G`

**AT+QCFG="data_interface"**
`+QCFG: "data_interface",0,0`

**AT+COPS?**
`+COPS: 0,0,"Mobisense Open5GS",11`

**at+c5greg?**
`+C5GREG: 0,1`

**at+CEREG?**
`+CEREG: 2,0`

**AT+CGDCONT?**
`+CGDCONT: 1,"IP","internet","0.0.0.0",0,0,0,0,,,,,,,,,"",,,,0`

**AT+QNWINFO**
`+QNWINFO: "TDD NR5G","99970","NR5G BAND 78",627264`

**AT+QENG="servingcell"**
`+QENG: "servingcell","NOCONN","NR5G-SA","TDD",999,70,0000019B0,1,7,627264,78,3,-99,-11,21,1,-`

**AT+QNWPREFCFG="nr5g_band"**
`+QNWINFO: "TDD NR5G","99970","NR5G BAND 78",627264`

**AT+QNWPREFCFG= "mode_pref"**
`+QNWPREFCFG: "mode_pref",NR5G`

**AT+QNWPREFCFG="nr5g_disable_mode"**
`+QNWPREFCFG: "nr5g_disable_mode",2`

**AT+QETH="routing"**
`[15:12:26:169] +QETH: route IPv4:␍␊
[15:12:26:169] Kernel IP routing table␍␊
[15:12:26:169] Destination     Gateway         Genmask         Flags Metric Ref    Use Iface␍␊
[15:12:26:169] 0.0.0.0         10.45.0.1       0.0.0.0         UG    0      0        0 rmnet_data0␍␊
[15:12:26:169] 8.8.4.4         0.0.0.0         255.255.255.255 UH    10     0        0 rmnet_data0␍␊
[15:12:26:169] 8.8.8.8         0.0.0.0         255.255.255.255 UH    10     0        0 rmnet_data0␍␊
[15:12:26:169] 10.45.0.0       0.0.0.0         255.255.255.252 U     0      0        0 rmnet_data0␍␊
[15:12:26:169] 192.168.225.0   0.0.0.0         255.255.255.0   U     0      0        0 bridge0␍␊
[15:12:26:169] ␍␊
[15:12:26:169] +QETH: route IPv6:␍␊
[15:12:26:169] Kernel IPv6 routing table␍␊
[15:12:26:169] Destination                                 Next Hop                                Flags Metric Ref    Use Iface␍␊
[15:12:26:169] ::1/128                                     ::                                      U     256    1        0 lo      ␍␊
[15:12:26:169] fe80::/64                                   ::                                      U     256    1        0 bridge0 ␍␊
[15:12:26:169] ::/0                                        ::                                      !n    -1     1        1 lo      ␍␊
[15:12:26:169] ::1/128                                     ::                                      Un    0      2        0 lo      ␍␊
[15:12:26:169] fe80::/128                                  ::                                      Un    0      2        0 bridge0 ␍␊
[15:12:26:169] fe80::24ca:e1ff:fe87:603e/128               ::                                      Un    0      2        0 ecm0    ␍␊
[15:12:26:169] fe80::2884:77ff:fecf:4d88/128               ::                                      Un    0      2        0 bri␍␊`
2

Hi there,

I can see from your info, you’ve disabled NSA 5G, what will you get if you don’t disable any technology?

BR,
Louis

3

I’m don’t need the nsa i need SA only.
Plus even if i did not disable nsa, still same issue.

Another thing, sometimes i see the APN is incorrectly ser but i see connection !!!