OFDM Sampling Frequency Offset Tracking via Segmented MLE Search
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Solution Overview
Problem
Conventional sampling frequency offset tracking methods using maximum likelihood estimation (MLE) in OFDM systems are complex and power-consuming due to large estimation search regions, making them inefficient for real-time tracking in wireless communication systems.
Innovation Solution
The method reduces the estimation search region by determining the search direction and size based on the estimated carrier frequency offset and maximum sampling frequency offset, allowing for efficient tracking of sampling frequency offset using a smaller search range within each OFDM symbol, thereby reducing the number of complex multiplications required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If maximum likelihood estimation (MLE) is used for sampling frequency offset tracking with a large estimation search region, then tracking accuracy is improved, but computational complexity and power consumption increase
Solution Approach 1:
The patent segments the estimation search region into multiple sub-regions and performs MLE tracking in stages. First, a coarse search is performed over the entire search region to identify a candidate region, then a fine search is performed within the candidate region to achieve precise tracking. This segmentation reduces the computational complexity from O(N) where N is the total search region size to O(N1 + N2) where N1 << N and N2 << N, while maintaining tracking accuracy.
Solution Approach 2:
The patent performs preliminary actions by conducting a coarse search before the fine MLE search. The coarse search preliminarily identifies the candidate region containing the true offset, which prepares the system for the subsequent fine search. This preliminary action eliminates the need to search the entire large search region in detail, reducing computational complexity while preserving tracking accuracy.
2Measurement precision
If maximum likelihood estimation (MLE) is used for sampling frequency offset tracking with a large estimation search region, then tracking accuracy is improved, but power consumption increases
Solution Approach 1:
The patent segments the estimation search region into multiple sub-regions and performs MLE tracking in stages. First, a coarse search is performed over the entire search region to identify a candidate region, then a fine search is performed within the candidate region to achieve precise tracking. This segmentation reduces the computational complexity from O(N) where N is the total search region size to O(N1 + N2) where N1 << N and N2 << N, while maintaining tracking accuracy.
Solution Approach 2:
The patent performs preliminary actions by conducting a coarse search before the fine MLE search. The coarse search preliminarily identifies the candidate region containing the true offset, which prepares the system for the subsequent fine search. This preliminary action eliminates the need to search the entire large search region in detail, reducing computational complexity while preserving tracking accuracy.
3Reliability
If conventional MLE method is used for sampling frequency offset tracking, then tracking is performed over the entire search region, but the number of complex multiplications increases
Solution Approach 1:
The patent segments the estimation search region into multiple sub-regions and performs MLE tracking in stages. First, a coarse search is performed over the entire search region to identify a candidate region, then a fine search is performed within the candidate region to achieve precise tracking. This segmentation reduces the computational complexity from O(N) where N is the total search region size to O(N1 + N2) where N1 << N and N2 << N, while maintaining tracking accuracy.
Solution Approach 2:
The patent performs preliminary actions by conducting a coarse search before the fine MLE search. The coarse search preliminarily identifies the candidate region containing the true offset, which prepares the system for the subsequent fine search. This preliminary action eliminates the need to search the entire large search region in detail, reducing computational complexity while preserving tracking accuracy.
Data Source
AI summary
A sampling frequency offset tracking method in an orthogonal frequency division multiplexing (OFDM) system includes determining a search direction of maximum likelihood estimation (MLE) using a carrier frequency offset estimated using pilot subcarriers of a received signal; calculating a size of a MLE search region using a maximum sampling frequency offset of the OFDM system and a resolution of the MLE; calculating a range of the MLE search region for each OFDM symbol based on the size of the MLE search region; and tracking the sampling frequency offset by calculating a maximum correlation between the pilot subcarriers and reference pilot subcarriers within the MLE search region each OFDM symbol. Accordingly, the search region of the MLE is reduced according to the sign of the estimated carrier frequency offset. Therefore, the sampling frequency offset can be easily tracked and the estimation error can be reduced.