Signal Quality value with LTE modems

[Sven Schwermer]

Hi,

I’m wondering what factors into the Signal Quality value for LTE modems. My suspicion is that only the “Signal” field of the +CIND message is used, but if I understood the manual for the ublox LARA-R211 correctly, that’s a poor quantity to use for this purpose as it only represents the RSSI. A better quantity would be the RSRP (and/or SNR). On my modem I’m getting a Signal Quality value between 0 and 20%, but the RSRP is better than -100dBm. On Android (https://android.googlesource.com/platform/frameworks/base/+/master/telephony/java/android/telephony/CellSignalStrengthLte.java#160) this would have resulted in 2 out of 4 bars, i.e. ~60%.

I’m using ModemManager 1.8.2. What’s the best way of dealing with this? Should I use the signal API and do the conversion to a percentage/bar count myself?

Best regards,
Sven