Thanks for the info on at!band ! I was unable to find anything useful regarding this command previously…
I did a band mask with everything except B7 ( which was the band used in my tests ), but the modem seems unable to connect. I think our provider only use this band in our zone.
Anyway, an endurance test ran during the week-end : we got 15 hours of continuous connection, with traffic generated. the sierra_net driver seems to be ok ; we just got that strange disconnection problem with Wi-Fi. We are located at the edge of the reception zone, that may explain why a little perturbation causes disconnections.
Since W-CDMA still works well, I think we are going to stay in 3G for the moment, and maybe give it another try when coverage is better.
I was unable to compile a recent kernel for the device, since we got to apply a lot of specific patches ; but we’ll keep QMI drivers in sight for the future !