Hello,
We have an issue regarding PSM availability when roaming. Some operators do not grant PSM and once a device connects to such a network, it would drain the battery in no time (we have lost some devices in the field that way). Since our product uses non-replaceble non-rechargeable battery, being permanently connected with no PSM is even worse that having no connection at all. Currently, we are implementing a fallback mechanism that forces network down (with AT+CFUN=4) on timeout if the PLMN doesn't grant PSM. However, the modem would remember the network and will prefer it when trying to reconnect again, even if there other networks that might provide PSM are available.
What would be the right workaround for this? Manually applying hard operator lock (AT+COPS) to select a PLMN that is known to provide PSM would work but would require a lot of maintenance. Overriding operator selection completely in application firmware (e. g. using AT%COPS=? to get a list, filter it against a list over networks the device have tried before, then selecting manually with AT+COPS) sounds quite error-prone and perhaps not 3GPP-compliant. Is there any way to tell modem firmware "try considering other PLMNs, I don't like this one" without hijacking the whole network selection flow?
