EM12 loses band in CA after a while if signal is weak

I have ab EM12 modem in a Mikrotik Chateau LTE12 router.
I have modem using B1, B3 and B7 but B7 signal is weak/fluctuating.
When LTE link is brought up, it created 3CA with B3 as primary and B1+B7 as aggregate bands.
After a little bit (few minutes) B7 is removed from the CA and the modem never adds it again,
in fact remains a 2CA until next disconnection and reconnection.

I suspect that the B7 band is selected even if weak at link initialization, but then is dropped
and never evaluated again. I think this is incorrect and B7 should be re-evaluated for CA
as soon as the signal improves.

Is there a modem option to tweak sensitivity for this?


     primary-band: B1@10Mhz earfcn: 150 phy-cellid: 81
        ca-band: B7@20Mhz earfcn: 3350 phy-cellid: 280,B3@20Mhz earfcn: 1650 phy-cellid: 81

   81  B1   150  -95dBm   -9dB   -69dBm  2s
   81  B3  1650  -94dBm   -12dB  -72dBm  2s
  273  B7  3350  -117dBm  -15dB  -93dBm  2s
  280  B7  3350  -111dBm  -11dB  -91dBm  2s      <---- weak/fluctuating B7
  399  B1   150  -106dBm  -20dB  -72dBm  2s
  399  B3  1650  -104dBm  -19dB  -75dBm  2s
  400  B1   150  -104dBm  -12dB  -83dBm  5s
  400  B3  1650  -100dBm  -15dB  -75dBm  2s

Dear Rick
Thank you for your inquiry in Quectel forums.
Generally, the CA is determined by the network eNB. For your request, I think you can check with Mikrotik and get end product level support base on hardware design, thanks.
In module level, please refer related instruction from https://www.quectel.com/product/EM12G.htm, thanks

Sorry, maybe my question was not clear, I’ll try again.

The EM-12 , when LTE connection is set up, negotiates a 3CA using B1, B3 and B7.
B7 has a fluctuating signal, but when part of the CA it really adds up to the speed sensibly.

On LTE connection establishment B7 is ALWAYS selected in CA.

The issue is, after a little bit B7 disappears from CA and we go from 3CA to 2CA and it is
never readded back unless I close the LTE connecton and reopen it. So it remains 2CA forever.

This is not a Mikrotik issue. I feel like your module should periodically re-check for B7 and readd it to CA.

As an alternative if there is an AT command to set the minimum threshold for a band to
be re-included in CA ,I would like to know it as it may help in this case.

Thanks again

Dear Rick
The state of CA is controlled by the network side. there no AT command to adjust minimum threshold or CA status in module level. I think 3CA would be keep if the signal of B7 is always good.
May I know the following information
Company name and location / project application/ project timeline / Module FW version

Sorry, just an end user here.
Thank you for your reply.
However, I do not understand why B7 is always picked up at connection time and then never again until a reconnection happens. It doesn’t make sense to me.

Firmware EG12EAPAR01A06M4G

Dear Rick
Is firmware EG12EAPAR01A06M4G? I think you can feedback to Mikrotik to get suitable FW. Due to
technical service rules, Product supplier will support you firstly in this case, thanks

Yes that’s the firmware I’m running.

Dear Rick
So this is EG12, not EM12. OK, next Mikrotik will feedback to Quectel if needed, thanks

On my side, I have the same issue but my signal are strong on B28/B3 and B7
After a connection, it always finds 3CA and after a while (on my side very quickly = few minutes), it goes to 2CA and only first band and never come back until :

  • Disable/enable the LTE connection (3CA is back directly)
  • Remove the LAN from Mikrotik and let running 5 to 10 minutes alone (most of the time when I’m putting back the LAN, 3CA is up until few minutes.

Compared to other product, the CA stay stable for hours but not on EG12 from Chateau LTE12.

Also, I did test (same operator “FREE”) on other site, and it’s the same.

I didn’t test another operator “BOUYGUES” and need to do more test with it because, it seems that CA stay in line for few hours.

The difference I have notified between both operator, it seems that BOUYGUES supply all CA even if no data download is running while for “FREE” to maintain CA, we must use internet DATA, as soon as we stop transfer CA are removed but never revive when it needs to be.

On other product, when using DATA download, CA (2 or 3) are revived like it should.

I’m pretty sure something has to be done on firmware side to react to operator like “FREE” !

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Dear Sebastiii
Thanks for your so clear descriptions. it seems the issue is related to special operator. I suggest you could
contact product supplier, the supplier can do more tests in product level, for example, More test on different operator then compare the test log; More test on the product feature(sensitivity, power etc). In fact, we haven’t get any feedback like this issue from others costumers or others location.

Dear Jeffrey,

There is other post in other forum that confirm this issue and not only with “FREE” operator.
We really need info to supply you correct log :slight_smile:
Also, I can’t test anymore with EP06 but with it, there no issue !
So must be something in firmware on Quectel modem ?

Is there a beta firmware for EG12 to test ?

As Quectel support said, CA is primarily controlled by the carrier via the eNB function. At least in the US, most carriers drop all CA’s when there’s no data transfer and use a single channel for standby, and re-establish 2-4xCA when there’s heavy data transfer. When browsing websites, CA rarely kicks in, however when watching a video it usually jumps to 2-4xCA which again is controlled by the carrier. There’s no special/magical command to “force” CA.

Now, there could be some firmware issue which doesn’t allow re-establishing 3xCA for some reason, but I doubt. While you may get a higher CA in the beginning of boot up, carriers can also control CA based on the signal level/quality/congestion/etc, and even based on the equipment’s imei/deviceID, dropping it lower after the initial connection. There’s no need to obsess about it, as they say “It is what it is!”. :wink:

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salut j ai le même problème mon CA tombe toute en moyenne toutes les 90 minutes je dispose routeur Mikrotik Chateau LTE12. reseau freemobile j ai bande primaire qui bien selectionner est les bandes agrégées ne s active pas obliger de déconnecter et de rétablir la connexion avez vous trouvez une solution merci

Hi Mik,

I have always the same issue.
Le PB n’est toujours pas résolu de mon coté non plus :frowning:

merci pour votre réponse il y a t il pas un script qui pourrai réveiller les bandes?

EM12 works good with CA.
EG12 have problem with loses CA after 5m from low/no transfer at link. <- Quectel tell many times to ask MikroTik vendor about this. EG12 and CA failed after 5 minutes or more on dynamic aggregation

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