2 Roaming
22.0113GPPRelease 18Service accessibilityTS
2.1 General requirements
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).
2.2 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.
2.3 National roaming
National Roaming is a service whereby a UE of a given PLMN is able to obtain service from another PLMN of the same country, anywhere, or on a regional basis.
The availability of National Roaming depends on the home PLMN of the requesting UE and the visited PLMN; it does not depend on subscription arrangements.
2.4 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). For further information see clause 3.2.