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We have been using IMX6ULL processors along with a Quectel 4G module in our custom made boards. The 4G module can be initialised, brought up and the PPP0 interface can also be initialised which in-turn does provide us with internet connectivity too but, when we start downloading files (of about 10 MB - 200 MB), we have observed that the download begins to stall at irregular intervals. While the download does stall, the PPP0 interface is still up but we lose internet connectivity hence, we have to kill PPPD and re-initialise PPP0.

We have tried using different variations of PPP0 initialisation scripts that we could get our hands on but the issue still persisted however, recently when we wanted to dump the traffic on the PPP0 interface using TCPDUMP in-order to analyse the same, we observed that the download does not stall anymore and we also observed a much better 4G throughput too. We have still not been able to figure out why this is indeed the case. Any inputs or guidance on the same would be of great help.

P.S: The kernel version we have been using is 4.1.15 but, we have observed a similar behavior with the 5.4.70 kernel too.

Thanks in advance

Regards

Nitin

Nitin
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Check the 4G network first with AT+COPS? and AT+CSQ Does the Module disconnect from the base station? Do not try kill pppd and restart setting up ppp0, and try AT+CFUN=0 \ AT+CFUN=1 to restart the network registration first. And for 4G module, the Quectel provide a tool named quectel-CM to setup internet connection, it is of better performance than ppp. btw, have you check the the memory used and the CPU status?

MrVW
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    Please phrase this as an explained conditional answer, in order to avoid the impression of asking a clarification question instead of answering (for which a comment should be used instead of an answer, compare https://meta.stackexchange.com/questions/214173/why-do-i-need-50-reputation-to-comment-what-can-i-do-instead ). For example like "If your problem is ... then the solution is to .... because .... ." – Yunnosch May 16 '21 at 01:34