OFDM Symbol Time Error Estimation Using Intersymbol Correlation
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Solution Overview
Problem
Broadband transmission systems employing orthogonal frequency division multiplexing (OFDM) face challenges in accurately estimating symbol time errors due to intersymbol interference, especially in multipath environments and mobile reception, where existing methods are either computationally intensive or inefficient under heavy multipath conditions.
Innovation Solution
A method for estimating symbol time error based on intersymbol correlation using a predetermined period in the output signal of a discrete Fourier-transformation block, where samples from actual or preceding/succeeding symbols are selected, shifted, and complex-conjugate multiplied to derive a time error value, which is then used to adjust the timing window for minimizing intersymbol interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IFFT-based methods are used for symbol time error estimation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the necessary correlation information from the OFDM signal by using a predetermined period (e.g., guard interval or useful part) and computing autocorrelation only on this extracted portion. This avoids the need for full IFFT-based processing while obtaining sufficient statistics for time error estimation, thereby reducing computational complexity while maintaining accuracy.
Solution Approach 2:
Instead of performing complete IFFT-based channel impulse response estimation, the patent applies partial action by using only a predetermined period of the signal (such as the guard interval or a portion of the useful part) for autocorrelation computation. This partial processing is sufficient for time error estimation in most practical scenarios, reducing computational load while maintaining adequate measurement precision.
2Ease of operation
If conventional time synchronization algorithms are used, then ease of operation is improved, but productivity decreases in mobile reception
Solution Approach 1:
The patent performs preliminary action by pre-defining the correlation period and using predetermined periods (such as guard intervals or useful parts) for autocorrelation computation. This preparation allows the receiver to quickly estimate time errors without complex real-time processing, thereby maintaining ease of operation while improving tracking speed in mobile reception scenarios.
Solution Approach 2:
The patent replaces complex mechanical IFFT-based processing with simpler autocorrelation operations in the frequency domain. By substituting the heavy computational IFFT mechanism with lighter autocorrelation calculations on predetermined periods, the system achieves faster processing speeds while maintaining operational simplicity, thus improving productivity in mobile reception.
3Measurement precision
If data assisted tracking is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies self-service by using the signal's own autocorrelation properties to estimate time errors without requiring external data assistance. The predetermined period of the OFDM signal itself serves as the correlation basis, allowing the system to self-synchronize using inherent signal characteristics. This eliminates the need for complex data assisted tracking algorithms while maintaining measurement precision.
Solution Approach 2:
The patent achieves universality by designing a time error estimation method that works for various OFDM configurations (different guard interval lengths, subcarrier spacings) without requiring data assistance. The autocorrelation approach on predetermined periods is universally applicable across different OFDM variants, providing multi-functionality while reducing device complexity compared to data assisted methods.
Data Source
AI summary
The invention relates to a method and a system for estimating a symbol time error in a broadband transmission system, comprising:determination a time error signal of an output-signal of a discrete Fourier-transformation block (5) in a data symbol stream on the basis of intersymbol correlation using a predetermined period in each received symbol,selecting as a predetermined period last samples of a useful data part of an actual symbol and a preceding symbol after the discrete Fourier-transformation,determining the time error value (ε) based on the intersymbol interference of the selected samples of the actual symbol and the preceding symbol.