EPS Security Capability Provision in 5GS Interworking
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Solution Overview
Problem
In the 5G new radio (NR) network, user equipment (UE) cannot receive NAS security algorithm information in the Security Mode Command message, leading to potential failures during handover or fallback to 4G LTE due to lack of necessary security information.
Innovation Solution
The UE provides EPS capability information in cleartext within the Registration initial message before the security mode procedure, allowing the network to include NAS security algorithm information in the Security Mode Command message, and the network provides selected NAS security algorithm information in the Registration Accept or handover messages to ensure interworking compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE reports EPS capability information in the Security Mode Complete message after receiving the Security Mode Command message, then the security mode procedure can be completed according to current 5GS implementation, but the 5GS network cannot provide the NAS security algorithm information in the Security Mode Command message for the UE to perform the interworking procedure
Solution Approach 1:
The patent applies preliminary action by having the UE report EPS capability information in the Registration Request message before the security mode procedure begins. This allows the network to have the necessary information available when sending the Security Mode Command message, enabling the network to include NAS security algorithm information in that command message, thus resolving the timing issue where capability information was previously reported too late.
2Reliability
If the UE handover/fallback to 4G LTE is triggered without having NAS security algorithm information, then the interworking procedure may fail, but changing the message sequence to report capability earlier may increase protocol complexity
Solution Approach 1:
The patent resolves this contradiction by performing the capability reporting action preliminarily in the Registration Request message, which is already part of the established protocol flow. This approach does not significantly increase protocol complexity as it utilizes an existing message type, while ensuring that the network receives the EPS capability information before the security mode procedure, thereby enabling reliable handover operations.
3Ease of operation
If the 5GS network waits for the Security Mode Complete message to obtain UE EPS capability, then the current security procedure can be maintained, but the network cannot select and provide appropriate NAS security algorithm information in advance
Solution Approach 1:
The patent maintains the simplicity of the security mode procedure by having the UE include EPS capability information in the Registration Request message, which is sent before the security mode procedure. This preliminary inclusion of capability information allows the network to have all necessary information when formulating the Security Mode Command message, eliminating the need for additional information exchange steps while ensuring NAS security algorithm information can be provided appropriately.
Data Source
AI summary
Methods and apparatus are provided for providing UE EPS capability information and receiving non-access stratum (NAS) security algorithm information for an interworking procedure in the 5GS network. In one novel aspect, the UE provides the UE EPS capability information in cleartext before the security mode procedure, and the NAS security algorithm information is included in a security mode command message during the security mode procedure. In one embodiment, the UE EPS capability information is an S1 mode indicator or the 5GMM capability information including the Si mode indicator. In another novel aspect, the network provides the NAS security algorithm information before interworking procedure from 5GS to LTE. In one embodiment, the network provides the NAS security algorithm information in the Registration Accept message. In another embodiment, the network provides the NAS security algorithm information in handover procedure from the 5GS to LTE.