TA Transfer Across DU-CU Interfaces for Faster 5G Mobility

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Solution Overview

Problem

In 5G Release 18, there is no mechanism for sending timing advance (TA) values between distributed units (DUs) and centralized units (CUs) during layer 1 and layer 2 mobility, leading to delays in obtaining TA values and requiring random access synchronization.

Innovation Solution

A method for TA transfer involves sending a message from a candidate DU to a target CU, containing TA values of candidate cells, using improved F1 interface messages, to enable direct TA value exchange between DUs and CUs, reducing the need for random access procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If TA values are not transmitted between DUs and CUs during mobility procedures, then the existing protocol structure is maintained, but mobility delay increases due to required random access synchronization

Engineering Contradiction:

Improvemobility delayVSAvoidprotocol complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by having candidate DUs calculate and prepare TA values in advance during the handover preparation phase. These pre-calculated TA values are then transmitted to the target CU through F1 interface messages before the actual handover execution, eliminating the need for random access procedures and reducing mobility delay

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces the F1 interface as an intermediary communication channel between DUs and CUs. Through this interface, TA values are transmitted using modified F1AP messages (such as UE CONTEXT SETUP RESPONSE, UE CONTEXT MODIFICATION REQUIRED, or UE CONTEXT MODIFICATION RESPONSE), enabling direct TA value exchange without requiring terminal participation in the transmission process

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If random access procedures are used to obtain TA values, then TA synchronization is achieved, but signaling overhead and procedure complexity increase

Engineering Contradiction:

ImproveTA synchronizationVSAvoidprocedure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the TA value calculation and transmission function from the traditional random access procedure. By having the candidate DU calculate the TA value independently and transmit it directly to the target CU through the F1 interface, the patent removes the need for terminal-initiated random access procedures while maintaining TA synchronization reliability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The candidate DU performs self-service by autonomously calculating the TA value based on uplink signal measurements without requiring terminal participation. The DU then transmits this self-calculated TA value to the target CU, eliminating the need for the terminal to perform random access procedures for TA acquisition

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS20260082345A1Ta transmission method and device

Publication Date: 2026.03.19 DATANG MOBILE COMM EQUIP CO LTD

AI summary

Embodiments of the present disclosure provide a TA transmission method and device. The method is applied to a candidate distribution unit (DU), and comprises: sending a first message to a target centralized unit (CU), wherein the first message contains a time advance (TA) value corresponding to a target terminal in a first candidate cell, or contains a TA value corresponding to the target terminal in a specified candidate cell.