GSM Roaming control | Telit Cinterion IoT Developer Community
June 6, 2016 - 12:01pm, 7145 views
I have some questions regarding roaming in TC65(i) ****ms (and eventually EH6x) as we currently experience issues with ****ms deployed (static) closed to country borders. The SIM cards involved there are generally enabled on roaming-data for commissioning and debugging but should ideally never use it during normal operation.
(1) What we "simply" want to do is tell the ****m+SIM to stick to its local preferred operator (for data and SMS mainly, we do not use voice)..
- either always (so even if cell quality is bad or inexistent)
- or as much as possible / as long as a data connection is possible (switch to roaming - international only as last resort and not at the first association error encountered for example)
What is the simplest way (if any) to do that?
(2) I don't know what are the thresholds (bearer quality, BER, RSSI, .. ) that trigger a switch to another operator (roaming or not) ? are they (easily) configurable?
(3) On EHS6x ****ms AT command set we can see the following command: AT^SCFG="MEopMode/SoR" (with SoR **** enabling or disable steering of roaming). What is the exact purpose of this command? When to use it?
(4) In contrary I don't have seen any AT command relating to roaming (except those reading the roaming status) in TC65(i) ****ms. Am I missing something? Are we meant to use the CPOL and CPLS commands to inhibit other operators? Is it safe to do that on the long term (eg. in case of on-site topology change or new operator, or even some kind of renaming) ?
Could you please share experience and preferred solutions for the mentioned use case and the related questions?
The roaming is implemented according to the standards and the thresholds are controlled by the operator. There is no way of modifying the algorithm or parameters by the user. Generally the module should keep logged to the home provider until it's possible. If it's in roaming it could also keep logged to the foreign networks even if the home network is accessible again.
The simplest way would be to manually chose the operator with AT+COPS command. But then the module would never register to any other network.
Steering of roaming is probably not for you because you don't want any roaming. It's about choosing the preferred roaming operator. If active the module should register to the foreign operator (preferred by your network provider) faster. It will try another network after the first failed registration.
CPOL and CPLS are related to the preferred operators lists so it is also useful for choosing the roaming operators.
If you need some custom scenario you would need to implement it on your own. It depends on your use case.
many thanks for your answer. Then I think it is better for us to not use CPOL and CPLS as it complexifies significantly the commissioning of sensors and even more when jungling with multiple countries. But it is not definitive. We will first try to handle further the roaming issues with the help of network operators.
Last question though: considering we force the APN to a specific one, will it still be valid in all cases if the modem switches to roaming? (at least for public networks)
I mean: can the APN be somehow responsible of restricting roaming data? (assuming roaming data is enabled on the provided SIM and the APN is valid for this SIM's operator) . Is there some automatic advertising or other factors that we should take care of when switching between operators for data?
You can only connect to the APN form the network that you are currently registered to. So if you choose the common APN name that exists in many networks like "internet" it is highly probable that you will be able to connect to data service in roaming. I'm not sure what you mean by "restricting roaming data" but this would depend on the operator.
If you don't specify the APN name you could still be able to connect to data service but this also depends on the network configuration.
even if my question was not very clear, I appreciate your reply.
I will try to play with different APN settings for fallback solutions in roaming ("internet" or empty/unspecified) and see how it behaves.