PLS8-E: LTE connection only after 12 minutes, AT^SIND: ltebot, AT+CEMODE | Thales IoT Developer Community
March 29, 2022 - 5:48pm, 551 views
Hi, one of our customers uses a private APN and complained that with our PLS8-E based solution he can only use 2G, despite using LTE with other devices.
I found that SMONI will initially tell "4G... LIMSRV", but after a few seconds degrade to "2G... --" and then "2G... NOCONN". In this state, we can open a PPP connection with AT+CGDATA="PPP"...
Exactly 12 minutes after that has been established, we receive a +CIEV: psinfo,17 and the connection "upgrades" to 4G.
Now I noticed that 12 minutes is the same as the LTE Backoff Timer, and sure enough,
> ^SIND: ltebot,0,1,26,"apn.ourValuedCustomer.com","Insufficient resources"
How can I avoid this?
I was looking into AT+CEMODE, because I thought that it might be related to our default CEMODE of 1, which in the manual says
> "If it is unable to obtain voice service in the LTE network ... it shall disable the LTE capability, which results in re-selecting 2G or 3G".
I tried to set AT+CEMODE=2 for data-centric service that does not do this, but I invariably get a "CME ERROR 4: Operation not supported" from that command.
thank you
Hello,
With this command it is only possible to read the ****. For changing it there may be a special procedure needed. You would have to contact your local Thales m2m technical sales.
Does the module also switch to 4G if you do not start the PPP? How about if you select 4G RAT only with COPS command?
Best regards,
Bartłomiej
Thank you, I think I've made some progress by setting ^SCFG: MEopMode/GPRSAutoAttach to "disabled". I think this is because the customer uses a private, no-standard APN, and with AutoAttach the engine will first attach with the provider's default APN, apparently triggering the LTE Backoff Timer. Does this make any sense?
I hope disabling the AutoAttach does not affect the operation with other providers, though. If I do a manual AT+CGATT, this should be covered, although the AT reference recommends not to do so with LTE, right?
AT spec advises to enable auto attach as without that the module will not automatically register to LTE. So You have to use AT+CGATT=1. If it helps in your situation, it's not disallowed.
According to SIND URC the back off timer was activated due to insufficient resources. This might be employed to prevent congestion. The timer described in the spec - T3402 - is not a back off timer.
And what is your CGDCONT configuration? Do you set this private APN as CID1 or some other? Does the module register to LTE if nothing is set? Maybe you could use this private APN on CID2 for example for data connection.