M66 Roaming Network registraion


We are facing a issue with network registration when we are outside our home network. We have the SIM card (Telekom) from Germany. We went to austria for our test. There network establishment should be roaming means AT+CREG? should retrurn +CREG:5.

But it is still getting registered to home network.

We also have sent AT+COPS=0 to make the connection automatic.

Could you please let me know why this behavior.

Best Regards,

Description of roaming 3GPP is as follows:
A UE with a valid IMSI may roam and access service in the area authorized by the entitlement of the subscription.
If a communication has been established, the UE will in principle not suffer an interruption within the PLMN area (provided the entitlement of the subscription allows it). Exceptions are possible if no network resources or radio coverage are available locally.
However, if the UE leaves the PLMN area, an established communication may terminate. If the user then wants to continue, another network providing service has to be selected and a new communication has to be established (see clause 3).
Subject to roaming agreements, a visited network shall be able to prevent incoming roamers from using a particular radio access technology (e.g. when the home network has not implemented this radio access technology).
International roaming:
International roaming is a service whereby a UE of a given PLMN is able to obtain service from a PLMN of another country.
The availability of International Roaming is subject to inter-PLMN agreements.
Roaming in shared networks:
The following requirements are applicable to GERAN, UTRAN, E-UTRAN and NG-RAN sharing scenarios:

  • Mechanisms shall be specified to enable flexible allocation of visiting roamers among core network operators that have roaming agreements with the same roaming partners. The core network operators shall be able to pre-define their relative share of visiting roamers and distribute the visiting roamers that apply automatic network selection to different core networks connected to the radio access network accordingly.
  • When network sharing exists between different operators and a user roams into the shared network it shall be possible for that user to register with a core network operator (among the network sharing partners) that the user’s home operator has a roaming agreement with, even if the operator is not operating a radio access network in that area.
  • The selection of a core network operator among those connected to the shared radio access network can either be manual (i.e. performed by the user after obtaining a list of available core network operators) or automatic (i.e. performed by the UE according to user and operator preferred settings).

So,you need to confirm the PLMN information obtained by both registered network for your terminals;Or ask your local operator whether to sign a special service agreement.

You may use AT+CRSM command to check any PLMN lists on your USIM. The lists on the USIM will override the module’s searching priority. You need to check quite a number of 3GPP documents to understand the contents of the USIM.

You can also use AT+COPS=? to see if the module can really detect any networks other than the home network.