OFDM Receiver Frequency Error Estimation via Guard Interval Segmentation
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Solution Overview
Problem
In OFDM systems, especially in DVB-T2, incorrect estimation of the wide band carrier frequency error due to multi-path interference and noise leads to poor reception performance, as it affects the accurate detection of subcarrier positions and power distribution, causing incorrect demodulation and data loss.
Innovation Solution
An OFDM reception device that orthogonally transforms both the useful symbol duration and guard interval duration signals, allowing for accurate detection of wide band carrier frequency errors by comparing the transformed signals, thereby correcting frequency shifts and improving signal reception accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the guard interval signal is generated by frequency shifting the useful symbol signal by one subcarrier frequency, then the orthogonal transformation can be efficiently performed using the same transformation table, but the estimation of wide band carrier frequency error becomes incorrect due to multi-path interference and noise
Solution Approach 1:
The patent segments the frequency error estimation process into two distinct parts: wide band frequency error estimation (using the frequency-shifted guard interval signal) and subcarrier frequency error estimation (using the useful symbol signal). This segmentation allows each estimation to be performed optimally for its specific purpose, resolving the contradiction between computational efficiency and estimation accuracy.
Solution Approach 2:
The patent introduces an intermediary processing step where the frequency-shifted guard interval signal is used specifically for wide band frequency error estimation, while the useful symbol signal handles subcarrier frequency error estimation. This intermediary approach prevents the frequency shift from interfering with accurate subcarrier position detection, thereby resolving the measurement precision issue.
2Device complexity
If the frequency shifted guard interval signal is used for orthogonal transformation, then the transformation can be performed using the same transformation table as the useful symbol, but the power distribution and subcarrier positions cannot be accurately detected due to frequency shift
Solution Approach 1:
The patent divides the signal processing into separate functional paths: the frequency-shifted guard interval signal is used exclusively for wide band frequency error estimation, while the useful symbol signal is used for subcarrier frequency error estimation and data demodulation. This segmentation ensures that each signal component is used for its most appropriate function, maintaining both computational efficiency and detection accuracy.
Solution Approach 2:
The patent extracts the wide band frequency error information from the frequency-shifted guard interval signal and separates it from the subcarrier-level processing. By taking out only the necessary frequency error component and using it specifically for wide band correction, the system avoids the interference that would otherwise corrupt subcarrier position and power distribution detection.
3Device complexity
If conventional frequency error estimation is used without separating wide band and subcarrier frequency errors, then the processing is simpler, but the reception performance deteriorates due to incorrect frequency error detection in multi-path environments
Solution Approach 1:
The patent segments the frequency error into two components: wide band frequency error (affecting all subcarriers uniformly) and subcarrier frequency error (affecting individual subcarriers). By segmenting the estimation process accordingly, the system achieves reliable reception performance in multi-path environments while maintaining manageable processing complexity through the use of existing FFT-based transformation tables.
Solution Approach 2:
The patent implements a feedback mechanism where the estimated wide band and subcarrier frequency errors are used to correct the received signal before demodulation. This feedback loop ensures that frequency errors are continuously compensated, significantly improving reception reliability in challenging multi-path and noisy environments.
Data Source
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AI summary
An OFDM reception device A comprises: a first orthogonal transformation unit A1 that orthogonally transforms a signal for a useful symbol duration included in an OFDM signal and outputs a resulting orthogonally transformed signal; a second orthogonal transformation unit A2 that orthogonally transforms a signal for a guard interval duration included in the OFDM signal and outputs a resulting orthogonally transformed signal; a detection unit A3 that detects a wide band carrier frequency error amount according to the signal output from the first orthogonal transformation unit A1 and the signal output from the second orthogonal transformation unit A2; and a correction unit that corrects a wide band carrier frequency shift of the OFDM symbol according to the wide band carrier frequency error amount detected by the detection unit A3.