Modem disconnects with multiple video calls

[jcmtyler]

I've got a Verizon 4G LTE hotspot with unlimited data (my ISP says it's an HD video plan), using a MIMO external antenna and 4 CPU / 256M RAM router (see image below, not sure of the model) with built-in modem (Quectel EM12) and Verizon sim running OpenWRT with Luci and ROOTer. Speedtest.net consistently shows something like 50-60mpbs down and 15 mbps up. Fast.com only shows about 9 down / 8 up because I don't yet have a VPN setup. I use a Google Wifi mesh system so we can access this from all over the house.

The modem will disconnect whenever I'm on a Zoom call and my two kids are each on video calls using Google Meet. For referernce, I'm connected directly to the router via ethernet, my kids are connected via wifi. This happens 3 or 4 times a day, the calls will all drop and internet access will stop until I physically reboot the router / modem by pulling the plug. Wifi is still active when this happens, and I can log into the router via its web admin page and see that the modem has disconnected. In the system logs I typically see errors that show timeouts waiting for a modem response and pointing to the USB driver throwing an exception. This also happened with an earlier router running almost the same software but with less RAM.

I've tried setting a connection monitor that will either restart the modem or reboot the router when the connection drops, but that has never worked successfully for me, I still have to unplug the router power supply, wait 20 seconds and then plug it back in to get back online.

Does anybody have suggestions for how to further troubleshoot what's going on with the modem? Seems like either the modem is getting overwhelmed with all of the upload streams (simultaneous downloads have not caused the same issue) or perhaps Verizon is somehow kicking me off. Anybody faced this before or know how I might be able to isolate the cause?

I've been doing a lot of reading on OpenWRT to see if there is additional logging I can enable, but so far no luck.

Router with built-in modem:

[gscheb]

Hello,

This was happening to me on at&t. These two things seem to have helped it.

1. "Services / Scheduled Reboot". Make sure your time is correctly set, enable and choose a time for reboot. I set the family up to reboot every day at 4:30am.
This seems to keep the session fresh I think.

2. Downloaded newest version from here as well. http://www.aturnofthenut.com/upload/
Don't know if one is there for you though.

Also put in custom rules for this as well. Even though technically didn't need them.

[jcmtyler]

Thanks for the reply! There is already a scheduled reboot at 4am every day. I suppose I could look for an opportunity to do a hard reboot in the morning, after I've been working for a bit but before my kids start their video calls, maybe that would help.

I'll check with my ISP, I thought they had updated the firmware to the latest as of a month or so ago. I've been speaking to them about this issue since December with no luck. In fact we've tried a few different routers and all seem to have the same issue, which makes me wonder if Verizon is kicking us off at some point. I was really hoping that either modem connection logs or router system logs would help me figure out what's going on, but so far nothing is jumping out at me. If Verizon were forcing a disconnect, is there any way I could tell from my own OpenWRT logs?

I've seen other discussions around band locking, that's something else I haven't tried. I'll have to do some more exploration with the LTE Discovery app on my phone to see which bands are the strongest, maybe locking those would help.

[toddw]

Those cables look kinda thin, do you have specs on them. Wondering if your getting DB loss on those.

[jcmtyler]

Those cables look kinda thin, do you have specs on them. Wondering if your getting DB loss on those.

Here you go: https://www.data-alliance.net/n-female- ... h-36-inch/

[Rich Hathaway]

Would be helpful to know which mifi/hotspot you are using.

"is there any way I could tell from my own OpenWRT logs?"

dmesg the linux side so you can see exactly what its doing
If you dont know how simply run

adb shell su -c dmesg > dmesg.log

[Didneywhorl]

Would be helpful to know which mifi/hotspot you are using.

"is there any way I could tell from my own OpenWRT logs?"

dmesg the linux side so you can see exactly what its doing
If you dont know how simply run

adb shell su -c dmesg > dmesg.log

Would it place the log in the /tmp folder? Or literally in the root? Would it be better to drop it in /etc ? I'm super not a Linux person.

[Rich Hathaway]

Here, as long as you have the adb port enabled on your device and drivers loaded on your pc just run the script in my tool it is marked "run this script" and it will dump the file in the same folder for you.

dmesg tool.rar

[jcmtyler]

So yesterday tossed my theory out of the window. I had thought that the modem would crash under load from multiple simultaneous video calls. Yesterday however I was the only one online and so there was only one video call going on, and yet my modem crashed 3 times over a span of a few hours. I haven't tried to use adb yet like the posts above suggest, I guess that's my next step.

[gscheb]

Hello,
Question for you.
Do you have another router hooked to this thing that is actually supplying WiFi?

[Rich Hathaway]

Tell me what model mifi you are using, and crash usually means kernel panic and device ends up in download or 9008 (QDL) mode, is that what happened?

[jcmtyler]

Yes, I've got the hotspot router with built-in modem from the picture above, but I have the wifi in that router switched off. That router is connected by ethernet to a Google Wifi mesh, which is what supplies wireless access to the rest of the house. My work computer connects directly to the hotspot router, and my kids connect to the wifi for their school laptops.

[jcmtyler]

Tell me what model mifi you are using, and crash usually means kernel panic and device ends up in download or 9008 (QDL) mode, is that what happened?

I don't see a model or brand name on the hotspot router, it was supplied by my ISP. When I log into its Luci interface, the system status page says the model is 'UniElec U7621-06 (256M RAM/16M flash)'. The modem is reported as 'Quectel EM12'.

Here's what's frustrating, when I look in the Luci system logs I see something like this:

Code: Select all

Thu Mar 11 04:04:32 2021 daemon.info dnsmasq[3059]: read /tmp/hosts/odhcpd - 0 addresses
Thu Mar 11 04:04:32 2021 daemon.info dnsmasq[3059]: read /tmp/hosts/dhcp.cfg01411c - 2 addresses
Thu Mar 11 04:04:32 2021 daemon.info dnsmasq-dhcp[3059]: read /etc/ethers - 0 addresses
Thu Mar 11 09:11:14 2021 user.notice wrtbwmon: Cleanup backup
Thu Mar 11 09:11:30 2021 user.notice Create Connection: Connected
Thu Mar 11 09:11:30 2021 user.notice Connection Monitor: Start Connection Monitor for Modem 1
Thu Mar 11 09:11:31 2021 user.notice mwan3[4441]: Using firewall mask 0x3F00
Thu Mar 11 09:11:31 2021 user.notice mwan3[4441]: Max interface count is 60
Thu Mar 11 09:11:40 2021 cron.err crond[1578]: time disparity of 307 minutes detected
Thu Mar 11 09:31:29 2021 user.notice wrtbwmon: Cleanup backup

For reference, 4am is when the router has an automatic daily reboot. Today around 9:08am is when it crashed for the first time, which is about 5 minutes after the third simultaneous video call started, for whatever that's worth. These system logs don't tell me anything about a crash and doesn't even show the startup log when I would expect at a minimum. The kernel log seems to start fresh every time I have to hard-reboot the router, so I can't even go back and view what happened leading up to the crash.

[Rich Hathaway]

Ok, I see that is a MTK device and not qualcomm, I wont be to much help with MediaTek, I mostly work with QC

[gscheb]

Yes, I've got the hotspot router with built-in modem from the picture above, but I have the wifi in that router switched off. That router is connected by ethernet to a Google Wifi mesh, which is what supplies wireless access to the rest of the house. My work computer connects directly to the hotspot router, and my kids connect to the wifi for their school laptops.

Are you sure that is it legitimately in access point mode? Not just plugged into it? If so if it is not actually in access point mode that could be causing your issue.
Recently had that issue with Visible. But for years just had it just plugged in not with Access point mode with T-Mobile no problems. Then switched services and bam it was an issue.

[jcmtyler]

No it's not in Access Point mode. The primary Google Wifi node is connected to one of the ethernet ports on my router and Google Wifi handles its own DHCP.

Any ideas why that might cause an issue? Wifi on the hotspot router has been switched off so there shouldn't be any contention or clients that switch back and forth between the router and Google Wifi (with different subnets).

[gscheb]

Recently had some issues with visible working from home with it not being in access point mode. Once I set it up for that it worked better. Give it i a shot. There are youtube videos out there to set it up into access point mode. Even with the WiFi turned off in the other one still the two routers can still fight each other.
Another option read was putting the first device into bridge mode if that is an option.

[jcmtyler]

UPDATE: new modem seems to have resolved my issues. My ISP (Viper Broadband) sent me a new hotspot router, a GL-X750 from GL-iNet, and it does a much better job at handling our connection load. Now we'll have periodic slowdowns where video performance in Zoom degrades and my remote desktop feels a bit sluggish, followed by maybe a brief disconnection for 2-3 seconds, but then everything comes back right away and it's all good. This seems to happen when all three of us are on at the same time, so I wonder if there was just something about the previous OpenWRT / Luci / Rooter setup that did not handle these slowdowns well and instead the modem would disconnect without being able to recover. I even tried the various Rooter auto-reconnect options (either restart the modem or reboot the router) based on ping test, but that never would recover and I always had to power cycle the router to get back online. Now with this GL-X750 it handles this much more gracefully.

I don't think it's a hardware issue, at least from what I can see the old router had more RAM and a beefier Class 12 modem vs the new router that has less RAM and only a Class 6 modem. They definitely have different software though, so I wonder if the GL-iNet software is just better able to deal with this compared to OpenWRT / Luci / Rooter? Or maybe the old router just wasn't configured optimally?

Anyway my problem has now been resolved and, even though our bandwidth isn't awesome (20 Mbps down for data, 8 Mbps down for video without VPN, 7 Mbps up) our connection is much more stable and we don't get kicked out of calls anymore.