V2X Physical Channel Design for High Speed CFO Management

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Solution Overview

Problem

Current LTE systems are inadequate in handling high carrier frequency offsets (CFOs) in high-speed vehicular environments, which affect the reliability of V2X communication, particularly at 6 GHz, due to Doppler shifts and synchronization errors.

Innovation Solution

The proposed solution involves enhancing the physical channel design with a new subframe structure and DMRS patterns to improve CFO estimation and compensation, including increased subcarrier spacing, reduced OFDM/SC-FDMA symbol duration, and optimized DMRS mapping/puncturing patterns to handle larger frequency variations and enhance channel estimation accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional LTE physical channel design is used, then system compatibility is maintained, but CFO estimation accuracy deteriorates in high-speed vehicular environments

Engineering Contradiction:

ImproveCFO estimation accuracyVSAvoidV2X communication reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent segments the DMRS into multiple patterns (first DMRS pattern and second DMRS pattern) with different mapping configurations across multiple OFDM/SC-FDMA symbols. This segmentation allows the system to estimate CFO more accurately by utilizing multiple reference signal instances distributed in time and frequency, directly addressing the CFO estimation accuracy requirement in high-speed vehicular environments.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces additional time-domain dimensions by mapping DMRS to multiple OFDM/SC-FDMA symbols rather than a single symbol. This dimensional expansion provides more measurement opportunities for CFO estimation, improving both measurement precision and communication reliability in high-speed scenarios.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If increased subcarrier spacing is implemented, then CFO handling capability is improved, but system compatibility with conventional LTE deteriorates

Engineering Contradiction:

ImproveCFO handling capabilityVSAvoidSystem compatibility

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent dynamically configures the subcarrier spacing for V2X physical channels based on the operational requirements. By allowing flexible subcarrier spacing configuration rather than fixing it to conventional LTE values, the system can adapt to high-speed vehicular environments while maintaining backward compatibility through configurable design.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the subcarrier spacing parameter from the conventional fixed value to a configurable parameter that can be adjusted according to the specific V2X deployment scenario. This parameter change enables the system to handle larger CFO values in high-speed environments while maintaining compatibility through flexible configuration rather than rigid fixed parameters.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If reduced OFDM/SC-FDMA symbol duration is used, then frequency variation handling is improved, but processing time requirements increase

Engineering Contradiction:

ImproveFrequency variation handlingVSAvoidProcessing time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent segments the transmission time into multiple OFDM/SC-FDMA symbols, each carrying a portion of the DMRS. By distributing the reference signal across multiple shorter symbols rather than one long symbol, the system can handle larger frequency variations while reducing the processing time requirement for each individual symbol processing operation.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach significantly improves the robustness and reliability of V2X communication by effectively managing high CFOs, enabling reliable operation in high-speed scenarios up to 280 km/h and enhancing system performance.

Implementation Method 1

Methodology Applied

Scientific EffectDoppler shift: Doppler Effect

Data Source

PatentUS12068853B2V2X performance enhancements in high speed environments

Publication Date: 2024.08.20 APPLE INC

AI summary

Implementations of this disclosure generally may relate to the field of wireless communications. More specifically, implementations described in this disclosure relate to different 3GPP LTE and LTE-A system enhancements to address the issue and support reliable V2X operation in the high mobility environments. Several solutions to improve the V2X system performance in the high mobility vehicular channel propagation conditions are described. Some aspects relate to the suggestion of a new DMRS patterns within individual subframes that promote more accurate CFO estimation. Moreover, another aspect provides DMRS mapping or puncturing patterns to transmit individual DMRS in a periodic pattern on respective OFDM/SC-FDMA symbols so that they do not occupy all REs of the OFDM/SC-FDMA symbols, respectively.