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PLS8-E: LTE connection only after 12 minutes, AT^SIND: ltebot, AT+CEMODE | Telit Cinterion IoT Developer Community

March 29, 2022 - 5:48pm, 1042 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,"","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