User Equipment PTRS Density Determination via Fallback DCI

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Solution Overview

Problem

In next-generation mobile communication systems, there is a discrepancy in recognizing PTRS density between base stations and user terminals during higher layer reconfiguration, leading to potential communication throughput issues.

Innovation Solution

A method for user terminals to determine PTRS density using fallback DCI, assuming specific PTRS densities or patterns, allowing for appropriate transmission and reception of shared channels during RRC reconfiguration without relying on RRC parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If legacy PTRS density determination method is used, then higher layer parameter configuration is maintained, but discrepancy in PTRS density recognition between base station and UE occurs during RRC reconfiguration

Engineering Contradiction:

ImproveRRC reconfiguration adaptabilityVSAvoidPTRS density recognition consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies preliminary action by having the UE assume a predetermined PTRS density pattern when receiving RRC reconfiguration, before the actual reconfiguration is fully processed. This ensures that during the transition period, both base station and UE use the same PTRS density assumption, preventing recognition discrepancy and maintaining communication reliability.

Inventive Principle:

Principle #10Preliminary action

2Adaptability or versatility

If PTRS density is determined based on higher layer parameter, then configuration flexibility is maintained, but communication throughput decreases due to PTRS density mismatch

Engineering Contradiction:

ImprovePTRS configuration flexibilityVSAvoidcommunication throughput

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent implements feedback mechanism where the base station transmits Downlink Control Information (DCI) that explicitly indicates the PTRS density pattern to be used. The UE uses this feedback information to correctly identify the PTRS density, ensuring both sides are synchronized and preventing throughput degradation while maintaining configuration flexibility.

Inventive Principle:

Principle #23Feedback

3Reliability

If fallback DCI is used during RRC reconfiguration, then PTRS density determination reliability is improved, but device complexity increases due to additional processing requirements

Engineering Contradiction:

ImprovePTRS density determination reliabilityVSAvoidUE processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by modifying the UE's PTRS density determination parameters based on the DCI type (fallback vs. non-fallback). When fallback DCI is detected, the UE switches to using predetermined PTRS density values instead of higher layer parameters. This parameter switching approach improves reliability while minimizing the increase in processing complexity through clear conditional logic.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3840315B1User equipment and radio communication method

Publication Date: 2025.06.04 NTT DOCOMO INC

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AI summary

A user terminal according to one aspect of the present disclosure includes: a transmitting/receiving section that receives or transmits a shared channel based on fallback Downlink Control Information (DCI); and a control section that makes a given assumption on a density of a Phase Tracking Reference Signal (PTRS) of the shared channel scheduled by the fallback DCI. According to one aspect of the present disclosure, it is possible to appropriately determine a PTRS density.