NR V2X CSI Feedback Without Dedicated Reference Signals

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Solution Overview

Problem

In device-to-device (D2D) communication, especially for vehicle-to-everything (V2X) systems, the existing closed-loop MIMO approach faces challenges with outdated channel state information (CSI) due to high mobility, increased overhead from reference signals, and restricted antenna configuration options, leading to reduced spectral efficiency and reliability.

Innovation Solution

The solution involves estimating channel quality indicators (CQI) and rank indicators (RI) based on long-term channel statistics and precoder cycling, without relying on dedicated reference signals, to adapt transmission parameters and improve spectral efficiency and reliability in D2D communication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If dedicated reference signals are used for CSI feedback in closed-loop MIMO, then channel state information accuracy is improved, but overhead and spectral efficiency are reduced

Engineering Contradiction:

Improvechannel state information accuracyVSAvoidreference signal overhead

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts the essential function of reference signals (channel estimation) and implements it through alternative means - using demodulation reference signals (DMRS) and uplink channel measurements instead of dedicated CSI reference signals. This removes the overhead burden while maintaining the core measurement capability.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent makes existing reference signals (DMRS) serve multiple functions - both demodulation and channel quality measurement. By utilizing the uplink channel measurements for CSI feedback purposes, the system achieves multi-functionality without adding dedicated reference signals, thereby reducing overall overhead.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If closed-loop MIMO with frequent CSI feedback is used, then transmission reliability is improved, but channel state information becomes outdated due to high mobility

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidchannel state information freshness

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements dynamic adaptation of transmission parameters based on measured channel conditions. The system continuously monitors channel quality using uplink measurements and adjusts downlink MIMO parameters accordingly, creating a dynamic feedback loop that adapts to changing channel conditions without requiring frequent dedicated reference signals.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes transmission parameters (precoding matrices, modulation schemes, resource allocation) based on channel quality indicators derived from uplink measurements. By adjusting these parameters dynamically, the system maintains transmission reliability even when channel conditions change rapidly due to mobility.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If dedicated reference signals are deployed for V2X CSI measurement, then channel quality measurement is improved, but spectral efficiency is reduced

Engineering Contradiction:

Improvechannel quality measurement accuracyVSAvoidspectral efficiency

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent enables the system to measure channel quality using its own existing uplink transmissions and DMRS. The UE performs channel measurements on signals it already receives for demodulation purposes, making the system self-sufficient without requiring external dedicated reference signals. This self-service approach maintains measurement accuracy while preserving spectral efficiency.

Inventive Principle:

Principle #25Self-service

4Device complexity

If antenna configuration options are restricted in D2D communication, then system complexity is reduced, but adaptability and spectral efficiency are reduced

Engineering Contradiction:

Improveantenna configuration complexityVSAvoidantenna configuration flexibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements periodic precoder cycling through a predefined codebook at the transmitter. This periodic action allows the system to explore different antenna configurations and precoding options systematically, maintaining adaptability while using simple, predetermined patterns that reduce configuration complexity.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system changes precoding parameters cyclically through a codebook, allowing the receiver to measure and report channel quality for different antenna configurations. This parameter cycling approach enables adaptive selection of optimal antenna configurations without requiring complex real-time configuration management, thus balancing adaptability with reduced complexity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11711176B2Systems and methods for NR V2X CSI feedback without dedicated reference signals

Publication Date: 2023.07.25 APPLE INC

AI summary

A user equipment (UE) configured for multi-antenna communication estimates at least one of a rank indicator and a channel quality indicator for device to device (D2D) based on communication data associated with a plurality of packets communicated using D2D communication and without using a dedicated reference signal for D2D communication. The UE may be configured as at least one of a transmitter (Tx) and a receiver (Rx) for vehicle-to-everything (V2X) communication through a sidelink channel.