SMF+PGW-C Local Offloading in 5GS to EPS Handover
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Solution Overview
Problem
The interworking between Fifth Generation (5G) and Evolved Packet System (EPS) networks faces challenges in maintaining local offloading of traffic during handovers of user equipment (UE) sessions, particularly when transitioning from 5GS to EPS, as existing solutions often result in loss or disruption of local uplink traffic offloading.
Innovation Solution
The implementation of a control plane functionality, specifically a Session Management Function (SMF) plus a Packet Data Network (PDN) Gateway Control Plane (PGW-C) (SMF+PGW-C), which manages UE sessions by identifying the use of an uplink classifier (UL-CL) UPF for local offloading and maintains tunnel information to establish bearers between the Serving Gateway (SGW) and the UPF anchor, ensuring continuous local offloading during handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If handover from 5GS to EPS is performed using existing solutions, then mobility between systems is enabled, but local uplink traffic offloading is lost or disrupted
Solution Approach 1:
The patent applies preliminary action by obtaining and preserving tunnel information related to the UL-CL UPF before the handover occurs. The SMF+PGW-C retrieves this information in advance and includes it in the session context response to the AMF, ensuring that the local offloading path is reestablished in the EPS without disruption. This proactive preservation of tunnel information prevents the loss of local uplink traffic offloading that would otherwise occur during system handover.
2Reliability
If tunnel information of UL-CL UPF is obtained and included in session context response, then local offloading is maintained during handover, but control plane functionality complexity increases
Solution Approach 1:
The patent applies universality by creating a multi-functional control plane entity (SMF+PGW-C) that combines the Session Management Function from 5GS with the PDN Gateway Control Plane from EPS. This unified entity can handle both 5GS session management and EPS bearer management, and universally manages tunnel information for both systems. The multi-functionality allows the same control plane to preserve and utilize tunnel information across different network systems, maintaining local offloading without requiring separate specialized functions for each system.
3Reliability
If bearer establishment uses UL-CL UPF tunnel information, then local traffic routing is preserved, but network configuration complexity increases
Solution Approach 1:
The patent applies the intermediary principle by using the SMF+PGW-C as a mediator between the AMF and the UL-CL UPF tunnel establishment process. The SMF+PGW-C receives the session context request from the AMF, retrieves the preserved tunnel information, and acts as an intermediary to establish the bearer with the appropriate tunnel configuration. This intermediary role simplifies the overall network configuration by centralizing the tunnel information management in a single control plane entity that understands both 5GS and EPS protocols, rather than requiring complex direct interactions between multiple network elements.
Data Source
AI summary
A network node includes control plane functionality for managing a session of a user equipment (UE) which is anchored at a User Plane Function (UPF) anchor for communicating traffic between the UE and a data network. The node operates to obtain, from an Access and Mobility Management Function (AMF), a session context request responsive to a handover indication indicating a handover of the session from a Fifth Generation System (5GS) to an Evolved Packet System (EPS). The node identifies whether an uplink classifier (UL-CL) UPF is in use for local offloading to a local UPF anchor for delivery to a local area data network. Based on the identifying, the node obtains uplink tunnel information of the UL-CL UPF instead of the UPF anchor for establishing at least one bearer for the session and sends to the AMF a session context response including the uplink tunnel information of the UL-CL UPF.