Hi, > On Jan 29, 2026, at 4:41 AM, Aurélien BOISSY <[email protected]> wrote: > > Hello, > > We are currently using ModemManager with various modems, specifically > SIMCOM7600E and QUECTEL EG915N. > > After reviewing the source code, it appears that the Signal Quality is built > from "+CSQ" or "+CESQ" URC messages : > • CSQ returns RSSI Indicator value (typically 0-31), then transformed by > ModemManager using a scaling factor like RSSI_INDICATOR*(100/31). > • Scaling factor depends on modem RSSI Indicator range.
It depends if ModemManager has more specific support for that modem’s signal quality commands. For the EG915N ModemManager does not yet have support for the +QIND “SQI” report which would likely be more accurate than CSQ. Looks like the simtech plugin for the SIMCOM device does not have more specific support either. > Could you please confirm if my understanding is correct? > > Furthermore, for 4G/LTE connectivity, RSSI is no longer considered a reliable > indicator for signal quality. Many sources on the internet prefer using RSRP, > RSRQ and SINR to check signal quality for 4G/LTE. Yes, though it depends on the firmware having support for these via commands we understand (eg, reverse-engineered binary protocols like QMI/MBIM, or AT command documents). For your modems those documents appear to exist, but we haven’t implemented the commands yet or haven’t received contributions that do. > > Is there any plan to update the signal quality logic to prioritize > RSRP/RSRQ/SINR over RSSI when the modem is operating in 4G/LTE mode? We’re always open to improvements if you’re able to contribute! I actually have an EG915N but not the time to implement this right now. I could provide testing and suggestions on how to do it though, if you’re able to? Thanks, Dan > > Thank you for your support, > > regards, > > > <lsi-attach-effects_bf6f512cd7957901098b63753623ff96ac096df9863e34ebd89d560f.png> > Aurélien BOISSYIngénieur Logiciel Embarqué > FDI encourage une utilisation numérique plus responsable : > limitez les impressions et conservez uniquement les mails essentiels.
