CJT Phase Tracking With UE Feedback for Multi-TRP Coherency

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Solution Overview

Problem

Existing wireless communication systems face challenges in maintaining phase coherency during coherent joint transmission (CJT) with multiple transmission-reception points (TRPs), particularly due to changes in UE position, time offsets, and TRP mode switches, leading to inefficiencies and reliability issues.

Innovation Solution

User equipment (UE) reports time-domain and Doppler-domain time-varying phase information to the network entity, enabling the selection of a precoding matrix for CJT, which reduces signaling overhead and power consumption, and enhances communication efficiency and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If coherent joint transmission (CJT) is implemented with multiple TRPs, then communication reliability is improved, but phase coherency is lost due to UE position changes, time offsets, and TRP mode switches

Engineering Contradiction:

Improvecommunication reliabilityVSAvoidphase coherency

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The UE measures phase information from multiple TRPs and feeds back time-varying co-phasing information to the network entity. This feedback mechanism enables the network to track and compensate for phase changes caused by UE movement, time offsets, and TRP mode switches, thereby maintaining phase coherency while implementing CJT

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the parameter representation from static phase information to dynamic time-varying co-phasing information. By reporting first-order variations in co-phasing angles over time, the system adapts to changing conditions and maintains phase coherence despite UE position changes and TRP mode switches

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If detailed phase information is reported by the UE, then phase tracking accuracy is improved, but signaling overhead increases

Engineering Contradiction:

Improvephase tracking accuracyVSAvoidsignaling overhead

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

Instead of reporting complete phase information for each TRP, the UE extracts and reports only the essential time-varying co-phasing information representing first-order variations. This extraction approach maintains phase tracking accuracy while significantly reducing the amount of data that needs to be signaled between UE and network entity

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS12501303B2Time domain phase tracking for coherent joint communications with multiple transmission-reception points

Publication Date: 2025.12.16 QUALCOMM INC

AI summary

Methods, systems, and devices for wireless communications are described that provide for a user equipment (UE) to report higher order phase variation information to a network entity for the purpose of coherent joint transmission (CJT) with two or more transmission reception points (TRPs). The UE may provide an indication to the network entity that the UE is able to report higher order phase variation information, and a measurement report may be provided that includes such higher order phase variation information. The network entity may select a precoding matrix for CJT with the UE via the two or more TRPs based on the measurement report. The network entity may then communicate with the UE via the TRPs in accordance with the selected precoding matrix.