Unknown behaviour when signal quality is poor

[Aleksander Morgado]

Hey,

> I am finding a unexpected behaviour and I would like to know how does the ModemManager work in situations like this one, when the modem has no signal at all or the signal is quite poor:
>
> <debug> [1607682864.814360] Received notification (service 'basic-connect', command 'signal-state')
> <debug> [1607682864.814379] Signal state indication: 6 --> 19%
> <debug> [1607682864.814532] Modem /org/freedesktop/ModemManager1/Modem/0: signal quality updated (19)
> <debug> [1607682866.172436] (ttyACM1): --> 7e 00 78 f0 7e
> <debug> [1607682866.172535] (ttyACM0): --> 7e 00 78 f0 7e
> [/dev/cdc-wdm0] Received message...
> >>>>>> RAW:
> >>>>>>   length = 64
> >>>>>>   data   = 07:00:00:80:40:00:00:00:00:00:00:00:01:00:00:00:00:00:00:00:A2:89:CC:33:BC:BB:8B:4F:B6:B0:13:3E:C2:AA:E6:DF:0B:00:00:00:14:00:00:00:00:00:00:00:63:00:00:00:05:00:00:00:02:00:00:00:FF:FF:FF:FF
> [/dev/cdc-wdm0] Received message (translated)...
> >>>>>> Header:
> >>>>>>   length      = 64
> >>>>>>   type        = indicate-status (0x80000007)
> >>>>>>   transaction = 0
> >>>>>> Fragment header:
> >>>>>>   total   = 1
> >>>>>>   current = 0
> >>>>>> Contents:
> >>>>>>   service = 'basic-connect' (a289cc33-bcbb-8b4f-b6b0-133ec2aae6df)
> >>>>>>   cid     = 'signal-state' (0x0000000b)
> >>>>>> Fields:
> >>>>>>   Rssi = '0'
> >>>>>>   ErrorRate = '99'
> >>>>>>   SignalStrengthInterval = '5'
> >>>>>>   RssiThreshold = '2'
> >>>>>>   ErrorRateThreshold = '4294967295'
> <debug> [1607682867.822380] Received notification (service 'basic-connect', command 'signal-state')
> <debug> [1607682867.822400] Signal state indication: 0 --> 0%
> <debug> [1607682867.822557] Modem /org/freedesktop/ModemManager1/Modem/0: signal quality updated (0)
>
>
> - The modem does not seem to transition from the "connected" state to the "registered"  state , or at least I cannot see it in the logs (attached in a previous mail). It remains as  state: connected.
> What is the expected behaviour here?
> - What does the ModemManager do in these cases where the modem is connected to the ISP but has really really low signal (i.e.  signal state 0) ? When does the Modem Manager consider the modem disconnected ?
>

There's really not much magic done by MM in this case, we just wait
for the modem to tell us it's disconnected via QMI WDS indications...

-- 
Aleksander
https://aleksander.es