Inter-RAT Re-establishment in Multi-RAT Dual Connectivity

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Solution Overview

Problem

Existing dual-connectivity configurations in LTE and NR networks face challenges in efficiently re-establishing radio resource control connections, particularly in multi-RAT scenarios like NE-DC and NGEN-DC, requiring the UE to transition to RRC_IDLE mode and re-establish connections from scratch, which is inefficient and resource-intensive.

Innovation Solution

The proposed method allows for flexible and efficient re-establishment of a target cell as a replacement for the UE's current primary cell in a dual-connectivity scenario, using a target node to establish a connection with the UE by receiving a re-establishment request message containing parameters and a message authentication code, enabling inter-RAT re-establishment without transitioning to RRC_IDLE mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE transitions to RRC_IDLE mode to re-establish connections in inter-RAT scenarios, then connection re-establishment can be performed, but interruption time increases and connection setup becomes more resource-intensive

Engineering Contradiction:

Improveconnection re-establishment capabilityVSAvoidinterruption time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The network pre-configures the UE with re-establishment parameters for both first RAT and second RAT cells before failure occurs. The UE maintains stored configuration information including cell identities, radio resource configurations, and other parameters needed for immediate re-establishment on the second RAT without transitioning to idle mode, thus reducing interruption time while ensuring reliable re-establishment capability

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If the UE uses stored configuration information for immediate re-establishment on second RAT, then interruption time is reduced, but configuration complexity and resource management become more challenging

Engineering Contradiction:

Improveinterruption timeVSAvoidconfiguration management

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The configuration information is segmented into distinct components: first RAT configuration, second RAT configuration, and associated metadata including cell identities and validity indicators. This segmentation allows the UE to selectively apply appropriate configurations based on the failure scenario, simplifying the management complexity while enabling fast re-establishment

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The network acts as an intermediary by providing pre-configured parameters and maintaining a mapping between first RAT and second RAT cell identities. This intermediary configuration reduces the UE's processing burden during re-establishment, as the UE can directly use the pre-provided parameters without performing complex configuration generation or validation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the network provides pre-configured re-establishment parameters for multiple RATs, then re-establishment efficiency is improved, but signaling overhead and network resource usage increase

Engineering Contradiction:

Improvere-establishment efficiencyVSAvoidsignaling overhead

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The pre-configured parameters are designed to be universally applicable across multiple second RAT cells and different failure scenarios. A single set of configuration information can be reused for re-establishment on any configured second RAT cell, eliminating the need for separate configurations for each cell and reducing overall signaling overhead while maintaining high re-establishment efficiency

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11785511B2Inter-RAT (radio access technology) re-establishment enhancements in multi-RAT dual connectivity (MR-DC)

Publication Date: 2023.10.10 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Methods for a target node to establish a connection with a user equipment (UE) operating in dual connectivity (DC) with a primary cell (PCell) served by a master node and with a primary secondary cell (PSCell) served by a secondary node. The methods include receiving, from the UE, a re-establishment request message comprising parameters associated with the PSCell, a message authentication code, and an indication of the UE's selection of a target cell served by the target node as a replacement for the PCell, which utilizes a first radio access technology (RAT). The PSCell and the target cell utilize a different second RAT. The methods include, based on the parameters associated with the PSCell, determining a full UE context for the UE, and establishing a connection with the UE based on the full UE context, whereby the target cell will serve as a PCell for DC.