5.3.4.1.2 Management of Service Area Restrictions

This clause describes Service Area Restrictions for 3GPP access. For Service Area Restrictions when using wireline access, see TS 23.316 [84].

A Service Area Restriction may contain one or more (e.g. up to 16) entire Tracking Areas each or the Service Area Restriction may be set as unlimited (i.e. contain all Tracking Areas of the PLMN). The UE's subscription data in the UDM includes a Service Area Restriction which may contain either Allowed or Non-Allowed Areas–specified by using explicit Tracking Area identities and/or other geographical information (e.g. longitude/latitude, zip code, etc). The geographical information used to specify Allowed or Non-Allowed Area is only managed in the network and the network will map it to a list of TAs before sending Service Area Restriction information to the PCF, NG-RAN and UE.

When the AMF assigns a limited allowed area to the UE, the AMF shall provide the UE with Service Area Restrictions which consist of either Allowed Areas or Non-Allowed Areas. The Allowed Areas included in the Service Area Restrictions can be pre-configured and/or dynamically assigned by the AMF.

The Allowed Area may alternatively be configured as unlimited i.e. it may contain all Tracking Areas of the PLMN. The Registration Area of a UE in the Non-Allowed Area should consist of a set of TAs which belongs to a Non-Allowed Area of the UE. The Registration Area of a UE in the Allowed Area should consist of a set of TAs which belongs to an Allowed Area of the UE. The AMF provides the Service Area Restriction in the form of TA(s), which may be a subset of full list stored in UE's subscription data or provided by the PCF, to the UE during the Registration procedure.

NOTE: As the finest granularity for Service Area Restrictions are at TA level, subscriptions with limited geographical extent, like subscriptions for Fixed Wireless Access, will be allocated one or a few TAs and will consequently be allowed to access services in a larger area than in e.g. a FWA system.

The limited allowed area may also be limited by the AMF by a maximum allowed number of Tracking Areas, even though this limitation is not sent to the UE. If maximum allowed number of Tracking Areas is used in combination with Allowed Area, the maximum allowed number of Tracking Areas indicates (to the AMF) the maximum number of TAs allowed in limited allowed area inside the Allowed Area. If maximum allowed number of Tracking Areas is used in combination with Non-Allowed Area, the maximum allowed number of Tracking Areas indicates (to the AMF) the maximum number of TAs allowed in limited allowed area outside of the Non-Allowed Area.

The UDM stores the Service Area Restrictions of a UE as part of the UE's subscription data. The PCF in the serving network may (e.g. due to varying conditions such as UE's location, application in use, time and date) further adjust Service Area Restrictions of a UE, either by expanding an Allowed Area or by reducing a Non-Allowed Area or by increasing the maximum allowed number of Tracking Areas. If NWDAF is deployed, the PCF may use analytics (i.e. statistics or predictions) on UE mobility from NWDAF (see TS 23.288 [86]) to adjust Service Area Restrictions. The UDM and the PCF may update the Service Area Restrictions of a UE at any time. For the UE in CM-CONNECTED state the AMF updates the UE and RAN immediately. For UE in CM-IDLE state the AMF may page the UE immediately or store the updated service area restriction and update the UE upon next signalling interaction with the UE, as defined in TS 24.501 [47].

During registration, if the Service Area Restrictions of the UE is not present in the AMF, the AMF fetches from the UDM the Service Area Restrictions of the UE that may be further adjusted by the PCF. The serving AMF shall enforce the Service Area Restrictions of a UE. A limited allowed area given by a maximum allowed number of Tracking Areas, may be dynamically assigned by the AMF adding any not yet visited (by the UE) Tracking Areas to the limited allowed area until the maximum allowed number of Tracking Areas is reached (i.e. the AMF adds new TAs to the limited allowed area until the number of TAs is equal to the maximum allowed number of Tracking Areas). The AMF deletes the list of TAs that have been used up under the maximum allowed number of Tracking Areas quota at every Initial Registration.

For a UE in CM-CONNECTED state the AMF shall indicate the Service Area Restrictions of this UE to the RAN, using a Mobility Restriction List.

The UE shall store the received Service Area Restrictions and, if there is previously stored Service Area Restrictions, replace them with the newly received information. If the Service Area Restrictions include a limited allowed area, the Service Area Restrictions are applicable for the Tracking areas indicated in Service Area Restrictions. If the Service Area Restrictions included an unlimited allowed area, the received Service Area Restrictions are either applicable for the registered PLMN and its equivalent PLMN(s) that are available in the Registration Area, or the registered SNPN that is available in the Registration Area. The RAN uses the Service Area Restrictions for target cell selection in Xn and N2 based handover.

Upon change of serving AMF due to mobility, the old AMF may provide the new AMF with the Service Area Restrictions of the UE that may be further adjusted by the PCF.

The network may perform paging for a UE to update Service Area Restrictions with Generic UE Configuration Update procedure (see clause 4.2.4 of TS 23.502 [3]).

In the case of roaming, the Service Area Restrictions are transferred from the UDM via the serving AMF to the serving PCF in the visited network. The serving PCF in the visited network may further adjust the Service Area Restrictions.

Support for Service Area Restrictions with NR satellite access is described in clause 5.4.11.8.