MC7455 Sprint disconnects in r00ter

[deewhylan]

For the past several days my MC7455 has been having disconnects every 30 minutes to 2 hours with modem reconnect enabled in r00ter. My sim card is clean and inserted properly, the antenna cables are connected to the MC7455 properly in the metal enclosure, and I'm using a 1 foot Anker cable that's pretty beefy so I don't THINK the cable is the issue.

I have my MC7455 set to work on the ipv4v6 r.ispsn apn and is set to work with all Sprint LTE bands; 25, 26, and 41. Selrat is set to 06 to force LTE.

When connection monitoring is turned off the modem will stay connected to the router but after 30 minutes to 2 hours it will just stop delivering internet. I will upload some photos of my gstatus when online and offline.

Any and all help is appreciated.

[JimHelms]

I have seen this occasionally when running the reconnection monitor. You may want to try this modification

One other tweak you might want to try is to add Sprint's "otasn" APN to your second and your third profile APN profile slot (the second is for the ipv4 address):

Code: Select all

at+cgdcont=1,"ipv4v6","r.ispsn"
at+cgdcont=2,"ip","otasn"
at+cgdcont=3,"ipv4v6","otasn"
at!reset

Some claim that adding the otasn APN helped to resolve disconnection issues.

[deewhylan]

Thanks, Jim.

Another note, with the reconnection monitor disabled, the modem still disconnects from the internet after 30 minutes or so. Sometimes it will only be around 30 minutes, sometimes it will disconnect after 3 hours. The modem itself is still connected to the router, but it will not deliver internet.

I'm trying out the otasn APN right now.

[deewhylan]

Well, it may be too soon to say, but as of right now my MC7455 has been connected for about 4 hours with no disconnects.

I do have one question. How does having more than 1 apn work? Are all 3 apn profiles active at once and it chooses an apn depending on what device you're using?

I'm kind of new to this stuff, I thought one device could only have one apn assigned.

EDIT: I just checked my connection log, the modem disconnected after about 3 and a half hours.

[deewhylan]

I ordered a 10cm low loss micro usb cable, I'm thinking it's my Anker cable. Even though Anker generally makes good quality cables, 1 foot may be too long.

[deewhylan]

I put my AT&T Mobley sim in the MC7455 and haven't had any disconnects for several hours, which leads me to believe it is not a cable issue. I will do some additional testing to make sure. However, I've always had my Sprint sim connected to band 41, and I get 50-90mbps on band 41 in my area, while I usually see max speeds of 20-30mbps on AT&T. So it still might be the cable, since Sprint is much faster in my area, which I assume would require more power. I'm going to try locking to band 25 or 26 with my Sprint sim and see if I still get disconnects with the same cable.

Using my 1 foot Anker cable, I have had times where the MC7455 simply wouldn't even detect on my PC or my router, and I would have to unplug usb cable and plug it back in to get it to detect, so it could still potentially be the cable.

[deewhylan]

Using the same cable, I do not get any disconnects on band 26 on Sprint until after 10+ hours. Either Sprint has issues with band 41 in my area, which I think is unlikely, or it's my cable.

[drakax]

I have been having the same Sprint disconnection issues over the last few months that you are describing. I have since done a bit more troubleshooting to see if I can narrow down where the problem may lie. I have noticed the same behavior in the screenshots that have been posted in this thread, where the LTE connection remains on, and IP stops flowing.

I have found that i can bring the connection online by running a simple script that causes udhcpc to release and renew the ip address. Running this script from the command line or by creating a custom command in the UI brings the IP connection comes back up immediately. I am currently trying to figure out the best way to add this into the Connection Monitor script to bring a downed interface back up quickly without having to reset the modem.

#!/bin/sh

# get pid of udhcpc
PID=`pidof udhcpc`
#release dhcp lease
/bin/kill -SIGUSR2 $PID
# renew dhcp lease
/bin/kill -SIGUSR1 $PID

[swwifty]

I have been having the same Sprint disconnection issues over the last few months that you are describing. I have since done a bit more troubleshooting to see if I can narrow down where the problem may lie. I have noticed the same behavior in the screenshots that have been posted in this thread, where the LTE connection remains on, and IP stops flowing.

I have found that i can bring the connection online by running a simple script that causes udhcpc to release and renew the ip address. Running this script from the command line or by creating a custom command in the UI brings the IP connection comes back up immediately. I am currently trying to figure out the best way to add this into the Connection Monitor script to bring a downed interface back up quickly without having to reset the modem.

#!/bin/sh

# get pid of udhcpc
PID=`pidof udhcpc`
#release dhcp lease
/bin/kill -SIGUSR2 $PID
# renew dhcp lease
/bin/kill -SIGUSR1 $PID

that's really odd. I wonder if the DHCP lease is expiring, then not being renewed properly?

[drakax]

--edited to add the timing of the issue info--

I don't know yet, with DHCP there is typically a lease expire time set when an IP is assigned. Some days, it will run for up to 16 hours with no issue at all then it will drop off multiple times in a row, sometimes as short as 15 minutes in between. I have smokeping running to get some statistics on how often this happens, and maybe a better pattern as to when the issue arises that is less anecdotal. But, i do not have enough data yet from it to discern anything.



Now, I have tried this with both the we826, and the wg3526, on both connected to the antennas that come stock, and the 15dbi pole mount antennas https://thewirelesshaven.com/shop/antennas/700-27 ... l-antenna/ and my signal sits at 21 csq with stock antennas (speedtest DL 60-70) and 29-30 csq with the external (speedtest 85-90). Btw, the issue only rears its head on band 41, both with CA on or forced off. Band 25 is rock steady but I only get a speedtest of 10-12. The common denominator is the MC7455, and I just received an MC7354 an hour ago to see if it makes a difference.

[swwifty]

Interesting information. Keep up the trial and error, and let us know what happens!

[deewhylan]

I don't want to speak too soon, but I think the new cable fixed the issue. I bought this one: https://thewirelesshaven.com/shop/cables/usb-cabl ... ower-cord/

My 1 foot Anker cable apparently wasn't beefy/short enough for the speeds that were being delivered on band 41. The new cable arrived today, and it's thicker and shorter than my Anker cable. With the new cable listed above, I have been connected for 10 hours straight with not a single disconnect. I will keep you guys updated.

[deewhylan]

I forgot an important detail in my testing. Currently I am using my Sprint sim in an EM7455 in an enclosure. My EM7455 seems to be doing fine but my MC7455 is still having trouble connecting to my router, sometimes it will connect, but sometimes I have to reboot the router. I may have a faulty modem enclosure, because my MC7455 has trouble connecting to my computer aswell. Or maybe my MC7455 is faulty. I will do further testing by mounting the MC7455 inside of a WE826 router and see if I still get disconnects.

[deewhylan]

I am now getting disconnects on band 25, every 4 hours or so. I was also experiencing disconnect issues with my 341U usb modem, which is what I currently have activated with Sprint, before switching over to the MC/EM7455. My brother lives with me and uses a ZTE Warp Connect from Calyx with very, very few disconnects, so I don't think it's my Sprint tower. I ordered a ZTE Pocket Wifi on ebay today for less than $20 to replace my 341U just in case I need it.

[Johnsieve]

I have the same problem, no matter the band, I can still ping, but not surf after 6-48hrs requiring some intervention from me.

[jstever8]

Just a thought, but have you tried using a Y cable or a USB hub capable of providing more power than your typical USB2.0/3.0 port? If power is the issue, I would think this would help.

Sprint B41 is the only band in the US that I know of that uses TDD (Time Division Duplex) instead of the typical FDD (Frequency Division Duplex). This is how Sprint is able to deliver really fast download speed with mediocre uploads. They can change the division of the 20MHz channel to (15 DL, 5 UL) where as FDD has to keep it equal (10 DL, 10 UL).

[w.tenn]

I have observed the disconnects or periods where you can't pass IP traffic correlated with the RRC state IDLE.

I've got the same issue with WE826-t2 and MC7455. Using APN r.boost.ispsn I can easily connect to Sprint B41. The throughput varies but >20m down and 0.7-2.5m up is typical. Sometimes in less than a minute or as much as 30 minutes the RRC state will revert from CONNECTED to IDLE. When IDLE, you can't pass any IP traffic.

Sometimes the modem will transition itself from Idle to Connected and I can again pass upstream traffic. But in these cases it seems like it is for short periods. When I reboot or power cycle the device, it seems to remain 'RRC Connected' for longer periods. Sending a reset to the modem does the same thing.

When you see this in the gstatus, it's working with no packet loss on the ping to 8.8.8.8. IP traffic will pass.
RRC state: RRC Connected

When it transitions to RCC Idle, I have 100% packet loss. No IP traffic will pass.
RRC state: RRC Idle

In Status>overview it will indicate you have both IPV4 and 6 connections. But I have noticed there are no gateway IP addresses for either. Likewise Modem>Network Status will indicate it is connected but of course there is no internet access.

LTE RRC state appears to be used by the user's equipment (the modem).
https://www.rfwireless-world.com/Tutori ... tates.html

RRC Idle State

• RRC IDLE state, UE is known in EPC and has IP address but not known in E-UTRAN/eNB
• In this LTE UE can receive broadcast or multi-cast data, it will monitor a paging channel to detect incoming calls, it will perform neighbor cell measurements and does cell selection as well as reselection and acquires system information.
• In the LTE RRC IDLE state, a UE specific DRX (discontinuous reception) cycle may be configured by upper layers to enable UE power savings

I have wondered if this is something that may be resolved by an AT command. I looked through the AT command reference and did not find what looked like a setting to affect when the UE transitions from CONNECTED to IDLE. It could be something in the SIM that instructs the modem to transition the RRC state from connected to idle in order to save power.

I'm just starting to work on this problem myself. Maybe a more more knowledgeable person can determine if the RRC state transitioning back and forth from Idle to connected is related to the Sprint disconnect issue.

Ken

[JimHelms]

I have seen this on several occasions.

Have you tried powering it down, removing the SIM Card, power it back up and reset the Modem to OEM status?

Then, power it down, reinstall the SIM Card and power it back up.

I would try operating the modem in QMI when it comes back online.

I have seen this correct a few of these type of issues.

See this TOPIC.

[teksupsm]

did you ever find this solution? I seem to have a similar issue.

[w.tenn]

Sorry, I never found the solution.