Signal Quality value with LTE modems

[Sven Schwermer]

Hi Dan,

> ETSI 27.007 says for the "signal" CIND indicator:
> 
> "signal" signal quality (0-5)
> 
> so if the modem isn't presenting something useful here, I'm not sure
> why it's implementing this indicator in the first place :)

For ublox, the “signal” indicator translates directly to power levels. The manual is not very clear which power level though.

> Random question, what does +CSQ report? MM uses +CIND because it gives
> async notifications, which +CSQ does not. CSQ is usually tied to RSSI
> though, which still isn't as useful for LTE.

Interestingly, the ublox AT manual says, that +CSQ reports the RSRP in LTE, but it doesn’t seem to match the value returned by +CESQ. Perhaps I’m mixing something up.

> You can use the Signal interface of ModemManager to pull out all lower-
> level values from the modem. "mmcli -m X --signal-setup=<rate in
> seconds>" starts and refreshes the signal values and "mmcli -m X --
> signal-get" gets the current signal values.

> Give the --signal-* stuff a try and see if that works for you. It's
> also available via the D-Bus interface which gives you event
> notifications on changes, if you're writing a custom app. If it doesn't
> work for the R211 let us know and we can possibly debug further.

Yep, that’s what I did, it seems to work well.

> Dan

Thanks for your help!

Best regards,
Sven