CU/DU Split Data Forwarding for RRC-Inactive Small Data

Solution Overview

Problem

Existing 5G NR systems face high signaling overhead and large data transmission delays due to the need for RRC state transitions when handling small data from UEs in RRC INACTIVE state, especially during handovers in CU/DU-split architectures.

Innovation Solution

Implementing a method for small data forwarding in RRC INACTIVE state using partial or dedicated context information, including TNL tunnel and RLC entity details, through F1AP messages between gNB-DU and gNB-CU, without involving RRC procedures, using partial UE context setup and data processing at the gNB-DU.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If RRC state transitions are performed to handle small data from UEs in RRC INACTIVE state, then data transmission reliability is improved, but signaling overhead increases and data transmission delay increases

Engineering Contradiction:

Improvedata transmission reliabilityVSAvoiddata transmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the handling of small data from large data by introducing a specific threshold. When data size is below the threshold, the system uses the optimized RRC INACTIVE state handling path; when above, it uses the traditional RRC state transition path. This segmentation allows the system to apply different processing strategies based on data characteristics, reducing unnecessary signaling overhead for small data while maintaining reliability for larger data transmissions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by performing only the necessary context setup and data forwarding procedures for small data in RRC INACTIVE state, rather than completing full RRC state transitions. The network device sends a context setup request to obtain necessary context information, then directly forwards the data without requiring the UE to transition to RRC CONNECTED state, thus performing just enough action to ensure reliable delivery while minimizing delay.

Inventive Principle:

Principle #16Partial or excessive action

2Reliability

If RRC state transitions are performed to handle small data from UEs in RRC INACTIVE state, then data transmission reliability is improved, but signaling overhead increases

Engineering Contradiction:

Improvedata transmission reliabilityVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent segments the handling of small data from large data by introducing a specific threshold. When data size is below the threshold, the system uses the optimized RRC INACTIVE state handling path; when above, it uses the traditional RRC state transition path. This segmentation allows the system to apply different processing strategies based on data characteristics, reducing unnecessary signaling overhead for small data while maintaining reliability for larger data transmissions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by performing only the necessary context setup and data forwarding procedures for small data in RRC INACTIVE state, rather than completing full RRC state transitions. The network device sends a context setup request to obtain necessary context information, then directly forwards the data without requiring the UE to transition to RRC CONNECTED state, thus performing just enough action to ensure reliable delivery while minimizing delay.

Inventive Principle:

Principle #16Partial or excessive action

3Loss of time

If small data forwarding is implemented in RRC INACTIVE state without RRC procedures, then signaling overhead is reduced and data transmission delay is minimized, but device complexity increases

Engineering Contradiction:

Improvedata transmission delayVSAvoidnetwork device complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent introduces a context setup request mechanism as an intermediary between the network device and the UE context management system. This intermediary allows the network device to obtain necessary context information (such as QoS parameters, security context, and data forwarding addresses) without requiring full RRC state transitions. The context setup request acts as a mediator that provides just enough information to enable direct data forwarding while maintaining network control and management capabilities.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12432618B2Data forwarding in centralized unit and distributed unit split architectures

Publication Date: 2025.09.30 ZTE CORP

AI summary

Presented are systems, methods, apparatuses, or computer-readable media for data forwarding in centralized unit (CU) and distributed unit (DU) split architectures. A DU may receive, from a CU, context information for forwarding of data from a wireless communication device that is in radio resource control (RRC) inactive state. The DU may receive, from the wireless communication device, the data from the wireless communication device that is in RRC inactive state. The DU may process the data according to the context information. The DU may send, to the CU, the processed data according to the context information.