In fact, it now pretty easy use scripting "functions" to issue the AT commands with at-chat and the Sierra etc modems. If you put it into a scheduler script, with an interval, it can poll the modem and store the detailed LTE info. See below:
[skyfi@hap94] > /system/scheduler/export
# sep/01/2021 18:33:32 by RouterOS 7.1rc2
# software id = QDR7-4Y0A
#
# model = RBD52G-5HacD2HnD
# serial number = xxx
/system scheduler
add interval=15s name=doPollingScripts on-event=":global AT;\r\
\n:global atLTEINFO;\r\
\n:global lteinfo;\r\
\n\r\
\n:global AT do={/interface/lte/at-chat lte1 input=\$1;};\r\
\n:global atLTEINFO [/interface/lte/at-chat lte1 input=\"AT!LTEINFO\?\" as-va\
lue];\r\
\n:global lteinfo do={ :put \$atLTEINFO };" policy=\
ftp,reboot,read,write,policy,test,password,sniff,sensitive,romon start-time=\
startup
[skyfi@hap94] > $AT ATI
output: Manufacturer: Sierra Wireless, Incorporated Model: MC7455 Revision:
SWI9X30C_02.32.11.00 r8042 CARMD-EV-FRMWR2 2019/05/15 21:52:20 MEID:
xxx IMEI: xxx IMEI SV: 19 FSN: xxx
+GCAP: +CGSM OK
[skyfi@hap94] > $lteinfo
output=!LTEINFO:
Serving: EARFCN MCC MNC TAC CID Bd D U SNR PCI RSRQ RSRP RSSI RXLV
2000 310 410 35614 0A1FC518 4 3 3 -3 269 -12.6 -100.7 -68.6 --
IntraFreq: PCI RSRQ RSRP RSSI RXLV
269 -12.6 -100.7 -68.6 --
40 -14.1 -101.4 -78.4 --
223 -17.6 -106.0 -78.4 --
InterFreq: EARFCN ThresholdLow ThresholdHi Priority PCI RSRQ RSRP RSSI RXLV
5110 0 0 0 290 -15.8 -99.2 -71.9 0
5110 0 0 0 33 -19.0 -97.1 -68.9 0
5110 0 0 0 8 -11.7 -91.3 -70.1 0
WCDMA: UARFCN ThreshL ThreshH Prio PSC RSCP ECN0 RXLV
OK
In theory, one could use :toarray and the new MQTT function (in IOT v7.1 extra package) to store persist these values in something like AWS. That gets more complex, but seemingly possible.
So there may be bug in the at-chat hanging... I've only seen that with the PPP at-chat. But have to say this is night and day with the Sierra modems from v6 where PPP mode only has 1 AT channel, so you can't even get RSSI with the MC7354/MC7455 modems while there running.