Hi all,
I am currently trying to use two SIMCOM SIM8300G-M2 5G modems to test cellular
performance (coverage, latency, throughput) from two different operators in a
rural area. I have been experiencing some stability issues with the modem
connections. It seems that it is related to the low signal level observed in
the area where I am measuring. Whenever the signal level is low, or there is no
coverage, the network interface is deleted, the modem disappears from mmcli
list, and it reattaches automatically after a bit, when the signal level
improves. This causes long (or at least longer than I would wish) interruptions
in my tests. I include some logs below as an example of what I see whenever
this occurs.
I have tried in different hosting devices (Lenovo laptop, NUC Pro 12) and a
newer version of the modems (SIMCOM SIM8380G-M2), and the problem persists. The
behavior is quite erratic, I do not always see the error described above
happening, but it is also appearing often enough so that it affects my
measurements.
Output from ip monitor:
Deleted 4: wwan1inet 100.77.182.96/26 brd 100.77.182.127 scope global
noprefixroute wwan1
valid_lft forever preferred_lft forever
Deleted broadcast 100.77.182.127 dev wwan1 table local proto kernel scope link
src 100.77.182.96
Deleted local 100.77.182.96 dev wwan1 table local proto kernel scope host src
100.77.182.96
Deleted 0.0.0.0 dev wwan1 lladdr 08 NOARP
4: wwan1: mtu 1500 qdisc fq_codel state DOWN
group default
link/none
Deleted 0.0.0.0 dev wwan1 lladdr 08 NOARP
Deleted inet wwan1
Deleted inet6 wwan1
Deleted 4: wwan1: mtu 1500 qdisc noop state DOWN
group default
link/none
inet wwan1 forwarding on rp_filter loose mc_forwarding off proxy_neigh off
ignore_routes_with_linkdown off
inet6 wwan1 forwarding off mc_forwarding off proxy_neigh off
ignore_routes_with_linkdown off
8: wwan1: mtu 1500 qdisc noop state DOWN group default
link/ether b2:8e:24:1d:25:20 brd ff:ff:ff:ff:ff:ff
Deleted inet wwan1
Deleted inet6 wwan1
Deleted 8: wwan1: mtu 1500 qdisc noop state DOWN group
default
link/ether b2:8e:24:1d:25:20 brd ff:ff:ff:ff:ff:ff
inet wwan1 forwarding on rp_filter loose mc_forwarding off proxy_neigh off
ignore_routes_with_linkdown off
inet6 wwan1 forwarding off mc_forwarding off proxy_neigh off
ignore_routes_with_linkdown off
Output from dmesg, where it seems that the modem is physically disconnected?:
[Mon Aug 14 10:21:34 2023] qmi_wwan 1-3.2:1.5 wwan1: register 'qmi_wwan' at
usb-:00:14.0-3.2, WWAN/QMI device, b2:8e:24:1d:25:20
[Mon Aug 14 10:21:36 2023] usb 1-3.2: USB disconnect, device number 7
[Mon Aug 14 10:21:36 2023] option1 ttyUSB6: GSM modem (1-port) converter now
disconnected from ttyUSB6
[Mon Aug 14 10:21:36 2023] option 1-3.2:1.0: device disconnected
[Mon Aug 14 10:21:36 2023] option1 ttyUSB7: GSM modem (1-port) converter now
disconnected from ttyUSB7
[Mon Aug 14 10:21:36 2023] option 1-3.2:1.1: device disconnected
[Mon Aug 14 10:21:36 2023] option1 ttyUSB8: GSM modem (1-port) converter now
disconnected from ttyUSB8
[Mon Aug 14 10:21:36 2023] option 1-3.2:1.2: device disconnected
[Mon Aug 14 10:21:36 2023] option1 ttyUSB9: GSM modem (1-port) converter now
disconnected from ttyUSB9
[Mon Aug 14 10:21:36 2023] option 1-3.2:1.3: device disconnected
[Mon Aug 14 10:21:36 2023] option1 ttyUSB10: GSM modem (1-port) converter now
disconnected from ttyUSB10
[Mon Aug 14 10:21:36 2023] option 1-3.2:1.4: device disconnected
[Mon Aug 14 10:21:36 2023] qmi_wwan 1-3.2:1.5 wwan1: unregister 'qmi_wwan'
usb-:00:14.0-3.2, WWAN/QMI device
[Mon Aug 14 10:21:45 2023] qmi_wwan 1-3.1:1.5: nonzero urb status received:
-EPIPE
[Mon Aug 14 10:21:58 2023] usb 1-3.2: new high-speed USB device number 8 using
xhci_hcd
[Mon Aug 14 10:21:58 2023] usb 1-3.2: New USB device found, idVendor=1e0e,
idProduct=9001, bcdDevice= 5.04
[Mon Aug 14 10:21:58 2023] usb 1-3.2: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[Mon Aug 14 10:21:58 2023] usb 1-3.2: Product: SDXLEMUR-SD-MTP _SN:AE2F01F4
[Mon Aug 14 10:21:58 2023] usb 1-3.2: Manufacturer: SIMCOM
[Mon Aug 14 10:21:58 2023] option 1-3.2:1.0: GSM modem (1-port) converter
detected
[Mon Aug 14 10:21:58 2023] usb 1-3.2: GSM modem (1-port) converter now attached
to ttyUSB6
[Mon Aug 14 10:21:58 2023] option 1-3.2:1.1: GSM modem (1-port) converter
detected
[Mon Aug 14 10:21:58 2023] usb 1-3.2: GSM modem (1-port) converter now attached
to ttyUSB7
[Mon Aug 14 10:21:58 2023] option 1-3.2:1.2: GSM modem (1-port) converter
detected
[Mon Aug 14 10:21:58 2023] usb 1-3.2: GSM modem (1-port) converter now attached
to ttyUSB8
[Mon Aug 14 10:21:58 2023] option 1-3.2:1.3: GSM modem (1-port) converter
detected
[Mon Aug 14 10:21:58 2023] usb 1-3.2: GSM modem (1-port) converter now attached
to ttyUSB9
[Mon Aug 14 10:21:58 2023] option 1-3.2:1.4: GSM modem (1-port) converter
detected
[Mon Aug 14 10:21:58 2023] usb 1-3.2: GSM modem (1-port) converter now attached
