Unable to get Carrier Aggregation working - Cradlepoint CBA850 on Verizon

[IanHorse]

All,

I've got a Cradlepoint CBA850 with the MC400LP6 modem.
I'm currently located in Dallas, Tx with good reception on bands 4 and 13.

For some reason, I cannot get CA turned on and stable.

I've tried resetting the modem completely back to factory defaults.
I've upgraded to the latest firmware

I've even locked the band to band 4 (by far the strongest. I get 4.8 SINR vs .2-.8 SINR on 13) and manually set AT!LTECA=1

When the modem boots up, (sometimes) CA will kick in for 1 or 2 seconds, and then it reverts to 'Not Registered' status.


I've seen several posts that state CA will not enable unless sufficient load is put on the connection, but I've been running speedtests like a madman, and it still does not kick on.

To be honest, I only get a round 6-13 Mbps max at any time of day even with 2 Wilson 50Ohm omni antennas on my roof.

Am I doing something wrong?

[IanHorse]

Just FYI, here's the output of a few commands on the modem:



[admin@CBA850-14b: /]$ atterm

Attempting to connect to AT Passthrough Server for modem at pmip8.

Connected to AT passthrough server (ctrl-d to exit):

Code: Select all

at!entercnd="A710"

OK
ATI

Manufacturer: Sierra Wireless, Incorporated
Model: MC7455
Revision: SWI9X30C_02.30.01.01 r7792 CARMD-EV-FRMWR2 2018/07/13 02:24:52
MEID: XXXXXXXXX
ESN: 1XXXXXXXX
IMEI: XXXXXXXXXX
IMEI SV: 16
FSN: LQ634700930210
+GCAP: +CGSM


OK
AT!GSTATUS?

!GSTATUS: 
Current Time:  11912		Temperature: 51
Reset Counter: 1		Mode:        ONLINE         
System mode:   LTE        	PS state:    Attached     
LTE band:      B4     		LTE bw:      20 MHz  
LTE Rx chan:   2100		LTE Tx chan: 20100
LTE CA state:  NOT ASSIGNED
EMM state:     Registered     	Normal Service 
RRC state:     RRC Connected  
IMS reg state: Full Srv		IMS mode:    Normal       

PCC RxM RSSI:  -71		RSRP (dBm):  -105
PCC RxD RSSI:  -75		RSRP (dBm):  -107
Tx Power:      --		TAC:         8508 (34056)
RSRQ (dB):     -13.9		Cell ID:     0208170C (34084620)
SINR (dB):      2.4


OK
AT!LTECA=?

!LTECA=<flag>
<flag>: 0 - disable CA
	1 - enable CA


OK
AT!LTECA? 

Hardware:
LTEB1: B8, 
LTEB2: B2, B5, B12, B13, B29, 
LTEB3: B7, B20, 
LTEB4: B4, B5, B12, B13, B29, 
LTEB5: B2, B4, B30, 
LTEB7: B3, B7, B20, 
LTEB8: B1, 
LTEB12: B2, B4, B30, 
LTEB13: B2, B4, 
LTEB20: B3, B7, 
LTEB25: 
LTEB26: 
LTEB29: 
LTEB30: B5, B12, 
LTEB41: B41, 

Permitted Bands:
LTEB2: B2, B5, B13, 
LTEB4: B4, B5, B13, 
LTEB5: B2, B4, 
LTEB13: B2, B4, 

Prune_ca_combos:
2A-13A-0           2A-13A-1           13A-2A-0           13A-2A-1           
4A-13A-0           13A-4A-0           

OK

[IanHorse]

Also,
I've tried many times to manually enable the CA:

Code: Select all

AT!LTECA=1

OK
AT!GSTATUS

ERROR
AT!GSTATUS?

!GSTATUS: 
Current Time:  12069		Temperature: 51
Reset Counter: 1		Mode:        ONLINE         
System mode:   LTE        	PS state:    Attached     
LTE band:      B4     		LTE bw:      20 MHz  
LTE Rx chan:   2100		LTE Tx chan: 20100
LTE CA state:  NOT ASSIGNED
EMM state:     Registered     	Normal Service 
RRC state:     RRC Connected  
IMS reg state: Full Srv		IMS mode:    Normal       

PCC RxM RSSI:  -74		RSRP (dBm):  -105
PCC RxD RSSI:  -76		RSRP (dBm):  -108
Tx Power:      --		TAC:         8508 (34056)
RSRQ (dB):     -14.3		Cell ID:     0208170C (34084620)
SINR (dB):      3.4


OK

It only seems to work if I can catch the modem right at boot. Once I got CA to stay on for a long time until I closed the Terminal window. Otherwise, it will (about 50% of the time) come up at boot and then die after a few seconds.

[JimHelms]

The AT!LTECA=1 is the default state allow the MC7455 to use carrier aggregation where AT!LTECA=0 disables it.

When you lock to a specific band, you may be disabling its ability to do carrier aggregation.

Have you tried creating a custom group of bands with band 4 and 13, and locking to that group of bands?

Also, on the CBA850 that group of bands must be manually set in the connection manager for that modem profile.

[JimHelms]

Your signal stats show no secondary carrier which may be influenced by your RSRQ reading of -14.3 which is below the acceptable threshold, or if the modem is locked to band 4.

[xdavidx]

Your transmit power is empty too, which means you aren't communicating at the time you run the at!gstatus? command. Run a speed test and run the command while the speed test is going on. The modems don't maintain connections to non-primary bands, to save on resources.

[IanHorse]

I have tried creating several groups using the CSV sheet for the sierra wireless 7544 from this site.
Once the groups were created, I locked into the groups by putting the AT!Band=GROUPNAME in my wireless profile. It does work to lock the group in, but it does not enable CA.

Additionally, for some reason, when I set it to all (00), all LTE (09), or one of those groups that I created, it seems to choose band 13 which I have pretty gnarly signal for. I get negative SINR values.

[scuba_steve999]

Would you mind sharing how you were able to band lock?

[JimHelms]

The Cradlepoint CBA850 has a device console than may be used to communicate with the modem via atterm See THIS post.

The problem with the built in terminal is it does not allow one to copy and past AT Commands necessary to program bands. Therefore, an easier solution (than typing commands) is to use PuTTY. THIS post will explain how this is done.

Next, you will need to decide what bands or group of bands you want to program into the modem. The easiest way is by using THIS tutorial and spread sheet.

Once the bands are programmed, refer back to the first link on this page about entering the band in the WAN Interface Profile's AT Config Script.