SXTR R11l-LTE7 random LTE drops

Hardware
1

Device and software:

  • Device: MikroTik SXTR
  • LTE modem: R11l-LTE7
  • LTE modem firmware: R11l-LTE7_V005
  • RouterOS versions tested:
    • 7.23.1 stable
    • 7.24rc1 testing
  • Operator: T-Mobile CZ
  • LTE mode only
  • APN: internet.t-mobile.cz
  • Roaming disabled

When CA is used, the LTE link randomly stops working. In RouterOS logs it appears as

lte1 link down

and then

lte1 forced reconfiguration due to difficulty setting link up

After adding a diagnostic script, I found that during the failure the modem reports:

  • AT+CFUN? → +CFUN: 4
  • Sometimes also *RADIOPOWER: 0
  • AT+CPIN? → +CPIN: READY
  • AT+COPS? → +CME ERROR: no network service
  • AT+CEREG? → usually +CEREG: ...,0
  • AT+CGATT? → +CGATT: 0
  • AT+CEER → +CEER: "0 Unknown"

The issue happens even with strong signal and stable cell information.

When using automatic bands or B3+B7 or B20+B1, the issue continued.

After locking to B3 or B1 only, the router had approximately 14 days+ uptime without the issue.

Any ideas? Thank you.

2

I have a similar issue as well, but my connection drops every 16-23 hours, I don't have logs saved yet but my ping spikes to 6k+ and the speed drops to basically nothing for 3 minutes, then it fixes itself.

My device and software:

Device: MikroTik wap ax lte7

  • LTE modem: R11l-LTE7
  • LTE modem firmware: R11l-LTE7_V005
  • RouterOS versions tested:
    • 7.23.2 stable
  • Operator: MT:S Serbia
  • LTE mode only
  • APN: gprswap
  • Roaming disabled

I'm on B3@20mhz+B1@10mhz, same thing happens on automatic band selection.