UE-to-Network Relay Key Management for Secure PC5 Discovery

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Solution Overview

Problem

In 5G systems, there is a lack of clear procedures for UE-to-Network Relay security key retrieval for discovery and communication over the PC5 interface, which is necessary for both public safety and commercial use cases.

Innovation Solution

A method involving application functions (AFs) provides discovery and security keys to user equipment (UE) and UE-to-Network Relays for PC5 interface operations, using AF-1 for discovery keys and AF-2 for security keys, with the 5G DDNMF or a new AF managing these functions to facilitate secure UE-to-Network Relay establishment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If clear procedures for retrieving security keys are implemented, then security and reliability are improved, but device complexity and procedure complexity increase

Engineering Contradiction:

ImprovesecurityVSAvoidprocedure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The network function provides the FQDN of the BSF to the UE in advance during the initial connection setup, so that when the UE needs to retrieve security keys, the BSF address is already available. This eliminates the need for complex bootstrapping procedures and directly enables key retrieval, improving security while avoiding procedure complexity.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the UE performs bootstrapping with the indicated BSF, then key material retrieval is improved, but communication time and procedure steps increase

Engineering Contradiction:

ImproveauthenticationVSAvoidcommunication time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The FQDN of the BSF is provided to the UE in advance during initial connection setup. This preliminary provision of the BSF address allows the UE to directly retrieve security keys without performing time-consuming bootstrapping procedures, thus reducing communication time while maintaining authentication reliability.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If the UE holds multiple B-TID and Ks materials from different BSFs, then adaptability and service continuity are improved, but memory usage and key management complexity increase

Engineering Contradiction:

Improveservice continuityVSAvoidmemory usage

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The UE is designed to hold multiple B-TID and Ks materials from different BSFs, allowing it to adapt to different network functions and maintain service continuity. This multi-functionality approach enables the UE to work with any BSF in the network, improving adaptability while the network manages the quantity of stored credentials.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12610230B2Key management for UE-to-network relay access

Publication Date: 2026.04.21 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method of operating a user equipment, UE, (1000) in a wireless communication system is provided. The method includes obtaining (502) a discovery key for discovery of a UE-to-Network relay from a first application function. The method includes using (504) the discovery key for discovery of the UE-to-Network relay over a PC5 interface. A method of operating a user equipment-to-network, UE-to-NW, relay node in a wireless communication system is also provided. The method includes obtaining (702) a discovery key for discovery of a user equipment, UE, from a first application function. The method includes using (704) the discovery key for discovery of the UE over a PC5 interface.