Multicast Session Join via Intermediate SMF for Roaming UEs

The patent introduces an intermediate SMF entity that acts as a mediator between the roaming UE and the original multicast service. When a UE roams out of the service area, the intermediate SMF receives the multicast session join request, identifies that the UE is roaming, and forwards the request to the original SMF. This intermediary mechanism maintains multicast service continuity while allowing UE mobility across network boundaries.

The patent segments the SMF functionality into local SMF entities and original SMF entities. The local SMF in the roaming area handles initial request reception and UE context management, while the original SMF maintains the multicast session. This segmentation allows service continuity without requiring a single large-scale SMF covering all areas, thus managing network complexity through functional distribution.

The patent implements a nested structure where the original SMF (outer layer) maintains the multicast session while the intermediate SMF (inner layer) handles local UE management. The intermediate SMF is nested within the service area of the original SMF, allowing the UE to access multicast services in roaming areas without the original SMF directly managing all local operations. This nested arrangement expands service area coverage while maintaining simplified centralized session management.