Time Offset Estimation for V2X Communication Systems
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Solution Overview
Problem
Accurate time offset (TO) and frequency offset (FO) estimation in high-speed propagation environments of vehicle-to-everything (V2X) wireless communication systems is challenging due to the mobility of transceivers, leading to inter-symbol interference (ISI) and inter-carrier interference (ICI), which existing methods poorly address.
Innovation Solution
A method and apparatus that estimate TO in the frequency domain through subcarrier accumulation before cross-correlation, provide TO-compensated signals, transform them into the time domain, and estimate FO using an iterative approach, integrating TO and FO compensation to improve estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TO and FO estimation methods are used in high-speed V2X environments, then the system can operate with standard processing, but estimation accuracy deteriorates due to mobility-induced ISI and ICI
Solution Approach 1:
The patent applies preliminary action by performing time offset estimation and compensation before frequency offset estimation. The received signal first undergoes TO estimation using correlation techniques, then TO compensation is applied to align the signal in time domain, and only then is FO estimation performed. This preliminary sequencing of operations ensures that TO-induced ISI is corrected before FO estimation, preventing contamination of FO measurements by timing misalignment.
Solution Approach 2:
The patent segments the offset estimation process into distinct sequential stages: TO estimation, TO compensation, and FO estimation. Each stage processes specific aspects of the signal independently, with TO handling temporal alignment and FO handling frequency alignment. This segmentation allows each estimator to focus on its specific parameter without interference from the other offset type, improving overall accuracy in high-mobility conditions.
2Measurement precision
If iterative TO and FO compensation is implemented, then estimation accuracy improves, but computational complexity increases
Solution Approach 1:
The patent reduces computational complexity by performing preliminary TO estimation and compensation before FO estimation, rather than implementing full iterative joint estimation. The TO is estimated first using correlation of known reference signals with received signals, compensated using the estimated value, and then FO is estimated from the TO-compensated signal. This preliminary sequencing avoids the need for complex iterative optimization algorithms while maintaining good accuracy.
Solution Approach 2:
The patent segments the estimation process into non-iterative sequential steps: TO estimation using correlation, TO compensation using the estimated offset, and FO estimation using the compensated signal. Each segment uses straightforward mathematical operations (correlation, complex multiplication, FFT) rather than iterative optimization, significantly reducing computational burden while maintaining practical accuracy for V2X applications.
3Reliability
If frequency domain TO estimation with subcarrier accumulation is used, then TO estimation robustness improves, but processing complexity increases
Solution Approach 1:
The patent merges multiple subcarrier components in the frequency domain to improve TO estimation robustness. By accumulating or combining information from multiple subcarriers before performing correlation-based TO estimation, the system benefits from diversity gain and noise averaging, making the estimation more robust against fading and interference on individual subcarriers. This merging approach uses efficient frequency-domain operations that leverage the structure of OFDM/SC-FDMA signals.
Solution Approach 2:
The patent replaces time-domain correlation methods with frequency-domain correlation methods for TO estimation. Instead of correlating time-domain signals directly, the signal is transformed to frequency domain using FFT, where correlation is performed on subcarrier components. This substitution leverages the computational efficiency of frequency-domain operations and the structure of multicarrier signals, providing robust TO estimation with reduced sensitivity to time-domain distortions.
Data Source
AI summary
A method and apparatus are provided. The method includes receiving a reference signal from a transceiver, estimating a time offset (TO) of the reference signal in the frequency domain based on a spectral phase ramp introduced by the TO, compensating the TO of the reference signal based on the estimated TO in the frequency domain by applying the spectral phase ramp to the received reference signal, and providing a TO compensated signal of the reference signal.