Update your firmware first then if you are connected to NSA network (5G) then run these commands. Try at your own risk.
AT+QCAINFO
AT+QENG="servingcell"
QCAINFO will show the parameters of all the bands you are currently using where as QENG="servingcell" only shows the PCC or primary carrier and also NSA SCC if applicable. You then need to get the PCI and E/ARFCN of the PCC LTE band, SCC LTE band (if applicable), and NSA SCC band.
i.e.
Band 1
E/ARFCN: 150
PCI: 25
Band 3
E/ARFCN: 1350
PCI: 30
N41 NSA 5G
E/ARFCN: 528030
PCI: 645
After you collected these data. Do these steps:
Lock band which is band masking on GL inet (?):
On LTE lock to:
B1, B3
On 5G NSA lock to:
N41
Then lock the PCC frequency of the LTE band.
AT+QNWLOCK="common/4g",1,150,25
To unlock:
AT+QNWLOCK="common/4g",0
# do a reboot
This command doesn't persist upon reboots.
Here is the format of the command:
AT+QNWLOCK="common/4g",<number of cells to lock (1-10),<EARFCN>,<PCI>...<EARFCN>,<PCI>
Yes, you can lock different PCC or primary cells but it is recommendable to lock to only one band unless needed.
!!! EXPERIMENTAL !!!
You can further limit the LTE where the modem can connect by locking specific EARFCN like:
AT+QNWCFG="lte_earfcn_lock",2,150:1350
Here is the format of the command:
AT+QNWCFG="lte_earfcn_lock",<total number of frequencies to lock>,<EARFCN>:<EARFCN>
To unlock:
AT+QNWCFG="lte_earfcn_lock",0
This is only recommended to do in order to force a certain combination of LTE bands where NSA anchors to achieve a stable connection. However, this is not ideal when you are on the move or where bands constantly change. I hope that this can help!