Aperiodic TRS Trigger-Based Time Frequency Tracking

Solution Overview

Problem

In wireless communications, especially in 5G New Radio (NR) systems, the removal of always-on cell-specific reference signals (CRS) leads to challenges in fine time and frequency tracking, particularly during events like SCell activation, beam switching, and in high-speed train scenarios, where frequent and accurate tracking is crucial to maintain communication quality.

Innovation Solution

The introduction of aperiodic tracking reference signals (TRS) that are trigger-based, allowing for flexible transmission without increasing UE complexity. These aperiodic TRS are associated with periodic TRS and share the same bandwidth or have a quasi-co-located relationship, enabling efficient time and frequency tracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If periodic TRS is used for time and frequency tracking, then tracking functionality is provided, but latency is high during critical events like SCell activation

Engineering Contradiction:

ImprovelatencyVSAvoidsystem overhead

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The aperiodic TRS is transmitted before the actual data transmission during critical events such as SCell activation, beam switching, or high-speed train scenarios. This preliminary transmission of tracking reference signals allows the UE to perform time and frequency tracking in advance, reducing latency without requiring continuous periodic TRS transmissions that would increase system overhead.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If frequent periodic TRS transmissions are used to improve tracking accuracy during mobility, then tracking performance improves, but system overhead increases

Engineering Contradiction:

Improvetracking accuracyVSAvoidsystem overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The system dynamically switches between periodic and aperiodic TRS transmissions based on UE mobility state and channel conditions. During critical events or high mobility scenarios, aperiodic TRS is triggered to provide frequent tracking updates without maintaining continuous periodic transmissions. This dynamic approach maintains tracking accuracy when needed while reducing overall system overhead during normal conditions.

Inventive Principle:

Principle #15Dynamics

3Loss of time

If aperiodic TRS is introduced for flexible transmission, then latency is reduced, but UE complexity increases

Engineering Contradiction:

ImprovelatencyVSAvoidUE complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The aperiodic TRS is transmitted before the actual data transmission during critical events such as SCell activation, beam switching, or high-speed train scenarios. This preliminary transmission of tracking reference signals allows the UE to perform time and frequency tracking in advance, reducing latency without requiring continuous periodic TRS transmissions that would increase system overhead.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The aperiodic TRS shares the same bandwidth and has a quasi-co-located relationship with the periodic TRS, allowing the UE to reuse existing processing structures and parameters. This parameter alignment reduces the complexity increase at the UE side while still providing the latency benefits of on-demand TRS transmission.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3763074B1System and method for time and frequency tracking signals with trigger-based transmissions

Publication Date: 2025.04.30 HUAWEI TECH CO LTD

Figure 1A~1C
Figure 1B~2
Figure 3A~3B

AI summary

A method for operating an access node includes transmitting a trigger for an aperiodic tracking reference signal (TRS) associated with a aperiodic TRS, and transmitting the aperiodic TRS in accordance with the trigger.