We have some Ezurio MG100 devices (with HL7800 modems) using Truphone SIM cards to access an LTE CAT-M1 network.
Occasionally, we experience difficulties with the devices failing to register with the network. When the issue occurs, the device will either continue searching for the network without success or it will ultimately receive a registration status of “Registration denied”. Other times, the network can be registered successfully without issue.
I’ve seen forum posts reference similar situations (e.g. HL7800 Registration denied with Rogers SIM cards), and I know that the problem may simply be due to coverage issues. I have already been in touch with the mobile network operator to see if they have any further information on their side.
In the meantime, is there anything that can be done on my end? For example, are there any AT commands I can attempt to further diagnose the problem? Are there any optimizations I can make to the modem configuration to improve its chances of successfully registering with the network?
The devices are often used in the same location, so I’d find it surprising for the network coverage to change drastically from one day to the next.
We tested the HL7800 for one of our projects. I have some ideas for your problem. Can you share some information about the HL7800 configuration? carrier setting? LTE band configuration? the HL7800 can be customized. Maybe changing one of these settings will help.
Thanks for your reply. I welcome any suggestions you may have.
Regarding the HL7800 configuration, our firmware doesn’t communicate directly with the HL7800, but rather uses Zephyr’s hl7800 driver to setup the modem. During initialization (i.e. power on), these are the AT commands which are ultimately sent by the driver:
AT+CEREG=0
AT&V
AT+CMEE=1
AT+CGMR
AT+KSRAT?
AT+KSRAT=0,1 // or AT+KSRAT=1,1 for NB-IoT
AT+KBNDCFG?
// AT+KBNDCFG=... // Band configuration would happen here (Not used in current setup)
AT+CFUN=4,0
AT+KSLEEP=2
AT+CPSMS=0
AT+CEDRXS=0
AT+CGMI
AT+CGMM
AT+CGSN
AT+KGSN=3
AT+CCID?
AT+CIMI
AT+CGDCONT?
AT+WPPP?
AT+CGDCONT=1,"IPV4V6","iot.truphone.com"
AT+KCNXCFG=1,"GPRS","iot.truphone.com",,,"IPV4V6"
AT+CEREG?
AT+CEREG=4
AT+KTCPCFG?
AT+KUDPCFG?
AT+CFUN=1,0
Regarding the LTE band configuration, here is the result of AT+KBNDCFG?
Current band configuration: 0000 00000000 0808189f
// LTE bands 1, 2, 3, 4, 5, 8, 12, 13, 20, 28
I unfortunately don’t have much experience with carrier settings (or even determining ideal LTE band configurations for that matter). Therefore my questions are:
Which carrier settings should be set?
How do I know which LTE bands to configure for my application?