I have the same problem the aggregation falls quickly
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Hi,
Do you find a way to fix this issue ? I have exactly the same issue using the same provider “Free” with a em160R-GL
Regards,
Yohann
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Hi Yohann,
Nope, still always the same issue, the only way is to disable/enable LTE interface.
Regards.
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Too bad… anyway thank you for your quick answer.
Cheers,
Yohann
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There needs to be a way to reinitialize the LTE session with the cell to reset the session timer without dropping any packets. I’ve seen the modems do this automatically, but I’m not sure if there’s a way to force it with an AT command.
The carriers are putting timers on the LTE sessions, and if you are on a cell for more than X amount of time, they turn Carrier Aggregation off. If you could reset the session via a script, you could constantly reset the counter and CA would stay enabled with the tower.
I am of the opinion that carriers do this to discriminate against fixed location usage, like in hotspots or routers, effectively turning CAT 20 modems into CAT 4 modems, to save bandwidth. As a phone is mobile, and constantly jumping between cells and eNBs, the timer is always reset, and CA is never turned off.
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Yes, I think you are right 
I have seen sometimes if no data are on the line for a few minutes, CA is enabled back from carriers.
I have tested it when to remove LAN cable from a router, this way, no more data exchange.
This is not a solution because all LAN device doesn’t have internet until LAN is connected back.
Was this ever resolved? I’m having the same issue with Mikrotik LTE18 (based on Quectel EG18-EA). After LTE initialization I get 4CA with RSSI in range of -55 to -80. Sometimes it takes a few minutes, sometimes an hour or two, but eventually all CA bands are dropped and I’m left on the last band which was uses as primary. If I’m lucky then it’s B3 which gives me decent speed, but sometimes it’s B7 and since I’m about 2km from the tower, the speed drops to almost zero and never recovers unless I restart the interface. Tested same setup (same external antennas) with Huawei B618 modem and it does not lose CA this way. Can we have a option that allows modem to renegotiates CA after a certain amount of time without resetting the LTE interface?
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Hi,
I didn’t use it recently, but it wasn’t resolved on my side last time I have checked it !
So it looks like the issue is in fact on the modem side. After a lot of investigation I figured out that the CA bands are being dropped when:
- the operator enabled/disables CA when you download/not download
- you have external antennas and modem is inside the house with weak signal for internal antennas
Whenever you have CA bands available, modem for some reason at one point tries to enable 4x4 MIMO which uses all 4 available antennas - 2 external and 2 internal. Internal antennas have very weak signal (below a certain threshold operator has configured) and tower sees that and blacklists the band. After a few minutes/hours you will cycle through every available CA band and eventually operator will blacklist all the bands except the primary.
There is no way to disable the 4x4 MIMO for EG12/EG18, as far as I found this feature is available only for EM160 by calling AT+QCFG=“lte4x4mimo/disable”. This needs to be added to the firmware for EG12/EG18 as well. In fact the whole situation with external antennas and 4x4 MIMO should be handled better by NOT using internal antennas at all.
@Jeffrey can you confirm the issue?
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There has been some development… apparently you can solve the CA band issue by calling:
AT+QCFG=“rrc”,4
My EG18 had a default value of 5. When I set rrc to 4 and rebooted modem, the CA bands keep hovering even with little or no traffic at all. I haven’t done exhaustive testing, but this seems very promissing.
I do not take credit for this, you can check out more info here: LTE18 and CA - MikroTik