Interworking Functions for 4G-to-5G PDU Session Bridging
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Solution Overview
Problem
The transition from 4G to 5G networks requires significant upgrades to existing 4G EPC nodes, which is time-consuming, costly, and risks disrupting legacy 4G services, especially when implementing 5G user plane capacity.
Innovation Solution
An architecture that utilizes interworking functions (IWFs) to facilitate communication between 4G and 5G networks, allowing legacy MMEs to establish PDU sessions in 5G Core networks, enabling network slicing and policy management without extensive upgrades to existing 4G components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If 4G EPC nodes are upgraded to support 5G networks, then 5G capabilities and network slicing can be implemented, but the upgrade process is time-consuming, costly, and risks disrupting legacy 4G services
Solution Approach 1:
An interworking function (IWF) node is introduced as an intermediary between the 4G EPC network and the 5G core network. The IWF translates and adapts signaling messages between different protocols (GTPv2 for 4G and 5G-specific protocols), enabling legacy 4G nodes to communicate with 5G network functions without modification. This mediator approach allows 5G capabilities to be introduced while preserving existing 4G infrastructure and services.
Solution Approach 2:
The network architecture is segmented into distinct functional domains: the legacy 4G EPC network, the new 5G core network, and the interworking function layer that bridges them. This segmentation allows independent evolution of 5G components without affecting 4G operations, enabling gradual migration and reducing upgrade complexity and risk.
2Adaptability or versatility
If extensive upgrades are performed on existing 4G components, then 5G user plane capacity can be implemented, but disruption to legacy 4G services increases and cost increases
Solution Approach 1:
The IWF acts as a protocol translator and adaptation layer that enables 5G user plane functionality without modifying existing 4G components. It converts 5G user plane packets into formats compatible with the 4G EPC network, allowing dual-stack operation where 4G and 5G services coexist independently. This ensures legacy 4G services continue uninterrupted while 5G capabilities are added.
Solution Approach 2:
The interworking function is designed to handle multiple protocols and message types simultaneously, supporting both 4G GTPv2 and 5G protocols through a single unified node. This multi-functionality allows the same infrastructure to serve both legacy and next-generation services, maintaining reliability while enabling versatility.
Data Source
AI summary
In one aspect, a control plane Interworking Function (IWF-C) is used to establish a Packet Data Unit (PDU) session in a data communications network. A create session request is received, for example from a Mobile Management Entity (MME). A create session management context request is generated by the IWF-C and transmitted to a Session Management Function (SMF). A create session management context request response is received from the SMF. A create session request response is generated by the IWF-C and sent, for example to the MME. In other aspects, control plane policy interworking and user plane interworking is provided between components of 4G and 5G networks.