5 High-level requirements
22.2613GPPRelease 18Service requirements for the 5G systemTS
5.1 Migration to 5G
5.1.1 Description
The 5G system supports most of the existing EPS services, in addition to many new services. The existing EPS services can be accessed using the new 5G access technologies even where the EPS specifications might indicate E-UTRA(N) only. Only new or changed service requirements for new or changed services are specified in this TS. The few EPS capabilities that are not supported by the 5G system are identified in clause 5.1.2.2 below.
5.1.2 Requirements
5.1.2.1 Interworking between 5G systems
The 5G system shall support a UE with a 5G subscription roaming into a 5G Visited Mobile Network which has a roaming agreement with the UE’s 5G Home Mobile Network.
The 5G system shall enable a Visited Mobile Network to provide support for establishing home network provided data connectivity as well as visited network provided data connectivity.
The 5G system shall enable a Visited Mobile Network to provide support for services provided in the home network as well as provide services in the visited network. Whether a service is provided in the visited network or in the home network is determined on a service by service basis.
The 5G system shall provide a mechanism for a network operator to limit access to its services for a roaming UE, (e.g. based on roaming agreement).
The 5G system shall provide a mechanism for a network operator to direct a UE onto a partnership network for routing all or some of the UE user plane and associated control plane traffic over the partnership network, subject to an agreement between the operators.
5.1.2.2 Legacy service support
In principle, the 5G system shall support all EPS capabilities (e.g. from TSs 22.011, 22.101, 22.278, 22.185, 22.071, 22.115, 22.153, 22.173, 22.468). However,
– voice service continuity from NG-RAN to GERAN shall not be supported,
– voice service continuity from NG-RAN to UTRAN CS should be supported (see Note),
– voice service continuity from GERAN to NG-RAN shall not be supported,
– voice service continuity from UTRAN to NG-RAN shall not be supported,
– CS fallback from NG-RAN to GERAN shall not be supported,
– CS fallback from NG-RAN to UTRAN shall not be supported,
– seamless handover between NG-RAN and GERAN shall not be supported,
– seamless handover between NG-RAN and UTRAN shall not be supported,
– access to a 5G core network via GERAN or UTRAN shall not be supported,
– video service continuity between 5GS and UMTS shall not be supported,
– IP address preservation for PS service when UE moves between 5GS and GSM/UMTS shall not be supported, and
– Service continuity between 5GS and CDMA2000 shall not be supported.
NOTE: Architectural or protocol changes needed to support voice service continuity from NG-RAN to UTRAN CS are expected to have minimum impact on architecture, specifications, or the development of the 5G New Core and New Radio.
5.1.2.3 Interoperability with legacy 3GPP systems
The 5G system shall support mobility procedures between a 5G core network and an EPC with minimum impact to the user experience (e.g. QoS, QoE).