CU-DU TBS Threshold Coordination for Early Uplink Data

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Solution Overview

Problem

In a CU-DU separation scenario, the RRC layer in the centralized unit (CU) cannot accurately determine the transport block size (TBS) threshold, affecting the implementation of early data transmission functions.

Innovation Solution

The distributed unit (DU) determines the TBS threshold for early uplink data transmission and sends it to the CU, which then forwards it to the user equipment (UE), enabling the UE to perform early data transmission based on the received threshold.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the base station adopts a centralized architecture with all protocol layers in one unit, then the RRC layer can accurately determine the TBS threshold for early data transmission, but the base station cannot achieve baseband resource sharing and cloudification

Engineering Contradiction:

ImproveTBS threshold determination accuracyVSAvoidbaseband resource sharing capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The base station is segmented into a centralized unit (CU) and a distributed unit (DU). The CU contains the RRC layer and determines the TBS threshold, while the DU contains the MAC layer and performs early data transmission. This segmentation allows the TBS threshold determination function to remain in the CU while enabling resource sharing through multiple DUs.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An interface is introduced between the CU and DU to enable communication and coordination. The interface allows the CU to provide the TBS threshold to the DU and the DU to report channel conditions and transmission status back to the CU, facilitating early data transmission despite the architectural separation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the base station adopts a distributed architecture with CU and DU separation, then baseband resource sharing and cloudification can be achieved, but the RRC layer in the CU cannot accurately determine the TBS threshold

Engineering Contradiction:

Improvebaseband resource sharing capabilityVSAvoidTBS threshold determination accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

A feedback mechanism is established where the DU reports channel conditions, buffer status, and transmission capabilities to the CU. The CU uses this feedback information to accurately determine the TBS threshold despite being separated from the radio frequency resources, and the DU uses the threshold to perform early data transmission.

Inventive Principle:

Principle #23Feedback

3Loss of energy

If early data transmission is implemented without accurate TBS threshold information, then signaling overheads can be reduced, but the early data transmission function cannot be properly implemented

Engineering Contradiction:

Improvesignaling overhead reductionVSAvoidearly data transmission functionality

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The TBS threshold is determined and configured in advance by the RRC layer in the CU before early data transmission occurs. This preliminary action allows the MAC layer in the DU to perform early data transmission without needing to establish a full RRC connection, thereby reducing signaling overhead while maintaining transmission reliability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12250703B2Data transmission method, centralized unit, and distributed unit

Publication Date: 2025.03.11 HUAWEI TECH CO LTD

AI summary

A data transmission method includes receiving, by a centralized unit (CU), a first message from a distributed unit (DU). The first message includes a first transport block size (TBS) threshold. The first TBS threshold is useable for early transmission of uplink data. The method further includes sending, by the CU, the first TBS threshold to a UE, and receiving, by the CU, uplink data from the UE based on the first TBS threshold.