UE Idle-State Paging Across 3GPP and Non-3GPP Access

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The challenge in 5G networks is that UEs in CM-IDLE state over non-3GPP access become unreachable when out of coverage, preventing the activation of user planes for down-link data delivery, even if they remain within non-3GPP coverage.

Innovation Solution

Implementing mechanisms for the 5G Core Network (5G CN) to page UEs over 3GPP access with an indication to perform a Service Request over non-3GPP access, or initiate handovers to 3GPP or non-3GPP access by setting up new radio bearers or IPsec child sessions, ensuring data delivery through available access types.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the UE enters CM-IDLE state over non-3GPP access, then power consumption is reduced and mobility is simplified, but the UE becomes unreachable when out of coverage, preventing down-link data delivery

Engineering Contradiction:

Improvepower consumptionVSAvoidnetwork reachability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The UE maintains the ability to be paged over multiple access types (both 3GPP and non-3GPP access). When in CM-IDLE state over non-3GPP access, the UE can still receive paging messages via 3GPP access, ensuring network reachability is maintained across different access technologies while preserving the power-saving benefits of idle state.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The 5G Core Network acts as an intermediary that manages the UE's reachability by sending paging messages through 3GPP access when the UE is in CM-IDLE state over non-3GPP access. This intermediary mechanism bridges the gap between the UE's power-saving idle state and the network's need to deliver down-link data.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the UE remains in CM-IDLE state over non-3GPP access, then device complexity is reduced, but the user plane cannot be activated for down-link data delivery

Engineering Contradiction:

Improvedevice complexityVSAvoiddata delivery capability

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The system dynamically transitions the UE from CM-IDLE state to CM-CONNECTED state over non-3GPP access when down-link data needs to be delivered. This dynamic state transition allows the system to maintain low device complexity during idle periods while enabling full data delivery capability when needed, optimizing both productivity and complexity at different times.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If paging over non-3GPP access is used, then access-specific optimization is achieved, but paging fails when UE is in CM-IDLE state for non-3GPP access

Engineering Contradiction:

Improveaccess-specific optimizationVSAvoidpaging reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Instead of paging the UE over the same access type where it is idle (non-3GPP access), the system inverts the approach by paging the UE over a different access type (3GPP access). This inverted approach ensures paging reliability while maintaining access-specific optimizations for data delivery once the UE is paged and transitions to connected state.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS12490176B2Handling a UE that is in the idle state

Publication Date: 2025.12.02 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method performed by an AMF. The method includes receiving a first request to establish UP for a UE's PDU session and, in response to receiving the request to establish UP for the UE's PDU session, determining whether a condition is satisfied. Determining whether the condition is satisfied comprises determining if the UE is in the idle state with respect to a non-3GPP access, wherein the condition is not satisfied if the UE is not in the idle state with respect to the non-3GPP access. The method also includes initiating paging of the UE by a 3GPP access as a result of determining that the condition is satisfied.