Critical LTE signal regression after modem firmware upgrade to v021 — RBLtAP-2HnD / Marvell R11e-LTE

RouterOS General
1

Hello,

I am reporting a critical regression on my device (LtAP) following the modem firmware upgrade to MikroTik_CP_2.160.000_v021.

— Hardware: RBLtAP-2HnD
— Modem: MARVELL Mobile CMCC CD (rev: 1.25) / R11e-LTE
— RouterOS: 7.22.2
— Installed modem firmware: MikroTik_CP_2.160.000_v021
— Operator: tested with SFR, (and also Orange, Free (France))
— SIM slot: 3

SYMPTOMS:

Before the upgrade (firmware v020 or earlier):

  • RSRP: approximately -80 dBm
  • Download throughput: normal (~30-50 Mbit/s)
  • AT+CSQ: returning a valid value

After upgrading to v021:

  • RSRP: -113 to -115 dBm
  • RSRQ: -19.5 dB
  • SINR: -13 dB
  • CQI: 0
  • AT+CSQ: 99,99 (signal not measurable)
  • Download throughput: ~3.5 Mbit/s

The AT+CSQ command returning 99,99 clearly indicates that the modem is unable to measure its own signal level — this is a malfunction introduced by the v021 firmware update.

Since firmware downgrade is not possible (rejected by the modem), the device is currently unusable in production conditions.

Full output of /interface lte monitor lte1 once:

status: registered
pin-status: ok
registration-status: registered
manufacturer: MikroTik
model: R11e-LTE
revision: MikroTik_CP_2.160.000_v021
current-operator: REGLO Mobile
lac: 49506
current-cellid: 163456787
enb-id: 638503
sector-id: 19
phy-cellid: 318
access-technology: LTE
earfcn: 78 (band 1, bandwidth 15MHz)
cqi: 0
rsrp: -113 dBm
rsrq: -19.5 dB
sinr: -13 dB

Request: Please provide a corrected firmware release (v022) or a procedure to downgrade the modem firmware to a previous working version. This bug renders the device completely unusable.

Thanks in advance,
Cedric.

2

Hi,

  1. We, forum users, do not have the ability to help you
  2. if the problem depends on particular ROS version then you should post in proper announcment topic as these topics are monitored (more or less) by Mikrotik when the verion is released
  3. the best way is to write (create a ticket) directly at Mikrotik support.

It's not bad that you've reported it on the forum as some users could save their time, but the solutions is in others' hands.

3

I have several devices that have that modem,
and I have not encountered the same problem in any of them, using the same firmware.

4

But are you running 7.22.2 on them?

I.e. could the issue be not the modem firmware but the ROS version?

5

Good point, I only use 6.48.7 in the LTE models.

6

For most LTE problems, the best self-service thing to do is make sure all version are aligned. That includes /system/routerboard firmware, RouterOS, and the firmware is update to date. Not always, but often LTE problem "disappear" once the version are aligned since LTE fixes are not always just modem firmware. And/or a physical power cycle (so the modem itself shutdown, since a reboot may not cause the modem to fully reset).

Not saying this for sure will "fix" the issue... but waiting for support to tell you to do that or potential "try 7.23rc2" (or whatever testing build). Now... it does seem like firmware issue, perhaps tied to your carrier. If you do create a support ticket, you for sure want to include a supout.rif. And often they want the logging at boot, so it's best to collect a supout.rif after a reboot and the LTE come up (since the supout.rif contains the logs). Support can do nothing without support/logs, and often they want to you enable topics=lte,!packet log topic, so it have more data. Support ticket may be way to go here.... but if you want it fixed, you'll need to collect logs not just give the specs, since they actually do have good logging to identify these things. But no logs... well, you're hoping someone else reported it who did provide them.

The other thing to do is downgrade the firmware. You can look at docs or forum for steps as I dunno specifics on LtAP with the R11e-LTE.