UE Network Attachment Switching After NR SA Rejection

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Solution Overview

Problem

In scenarios where a user equipment (UE) supports 5G New Radio Standalone (NR SA) and interworking with LTE, but the communication network does not support NR SA or interworking, the UE is unable to register in the LTE network due to unclear rejection reasons, leading to communication failures.

Innovation Solution

The UE disables the NR SA mode upon receiving specific rejection reasons, initiates a timer, and re-enables NR SA after a certain condition is met or a time period expires, allowing it to establish a communication connection with an LTE network using the same Public Land Mobile Network (PLMN) and Access Point Network (APN).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE supports NR SA and interworking with LTE but the network does not support NR SA, then the UE should be able to register on LTE network, but the registration fails due to unclear rejection reasons

Engineering Contradiction:

Improveregistration success rateVSAvoidrejection reason clarity

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The network provides feedback to the UE by including specific rejection cause values (e.g., cause value 55) in rejection messages, enabling the UE to understand why NR SA attachment was rejected and to appropriately switch to LTE network registration

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the parameter of rejection cause indication by introducing new specific cause values that clearly indicate NR SA non-support, allowing the UE to distinguish between different rejection scenarios and take appropriate actions

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the UE continuously attempts to attach to NR SA network, then the UE maintains 5G capability, but power consumption increases and network load increases

Engineering Contradiction:

Improve5G capability maintenanceVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The UE dynamically adjusts its network attachment strategy based on network responses. When NR SA attachment is rejected with specific cause values, the UE switches to LTE attachment, creating a dynamic adaptation mechanism that reduces power consumption while maintaining connectivity

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The UE autonomously determines the appropriate network attachment strategy by interpreting rejection cause values and independently switching between NR SA and LTE attachment modes without requiring continuous network control

Inventive Principle:

Principle #25Self-service

3Reliability

If the UE disables N1 mode after NR SA rejection, then the UE can register on LTE network, but the UE cannot re-enable NR SA without specific conditions

Engineering Contradiction:

ImproveLTE network registrationVSAvoidNR SA re-enablement flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system establishes preliminary conditions for N1 mode re-enablement, such as timer expiration or specific event triggers, allowing the UE to automatically revert to NR SA capability when appropriate conditions are met

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Timers and trigger events act as intermediaries between NR SA rejection and potential re-enablement, providing a controlled mechanism for the UE to transition between network modes based on predefined criteria

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12495380B2Method and device for establishing communication connection in wireless network

Publication Date: 2025.12.09 SAMSUNG ELECTRONICS CO LTD

AI summary

A method of establishing a communication connection by a user equipment (UE) includes transmitting a first attachment request to a communication network using a PLMN and an APN; receiving a reason for rejecting the first attachment request from the communication network; and disabling an N1 mode of the UE according to the reason for rejecting, to disable a new radio (NR) standalone (SA) mode of the UE. Thereafter, a second attachment request is transmitted for establishing a communication connection with an LTE network using the same PLMN and APN. The N1 mode is re-enabled and a corresponding process is initiated when a specific condition is satisfied or a specific time period has expired. The UE reports updated ability to the communication network when the N1 mode is re-enabled. The UE supports NR SA and interworking between NR SA and LTE. The communication network does not support NR SA or interworking between the NR SA and LTE at least in a coverage area where the UE is located.