Interference Center Frequency Estimation Using Null Symbol Spectrum
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Solution Overview
Problem
Existing interference cancellation methods using intermittent symbol transmission struggle to accurately distinguish between actual interference and its image in the frequency band, leading to suboptimal cancellation performance due to down-sampling effects.
Innovation Solution
An interference cancellation device that includes a data symbol extraction unit, null symbol extraction unit, power calculation units, and an interference center frequency estimation unit, which calculates the interference center frequency by comparing the null symbol spectrum with a threshold to determine the interference bandwidth and eliminates the effect of images, thereby improving estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the technique in Japanese Patent Application Laid-open No. 2017-227655 is applied to estimate interference frequency band from null symbol spectrum, then interference cancellation can be performed, but the down-sampling effect generates images that cannot be distinguished from actual interference
Solution Approach 1:
The patent segments the frequency band analysis by comparing the null symbol spectrum with the data symbol spectrum. By dividing the frequency domain into distinct regions and analyzing characteristics in each region, the method can identify and eliminate image components while preserving actual interference information.
Solution Approach 2:
The patent uses the data symbol spectrum as an intermediary reference to identify and remove image components from the null symbol spectrum. The data symbol spectrum serves as a mediator that helps distinguish between real interference and imaging artifacts, enabling accurate interference frequency band estimation without confusion from images.
2Device complexity
If null symbol spectrum is used directly for interference estimation, then processing is simplified, but image components contaminate the interference frequency band estimation
Solution Approach 1:
The patent extracts and removes image components from the null symbol spectrum by comparing it with the data symbol spectrum. This extraction process isolates the actual interference from the imaging artifacts, maintaining processing simplicity while improving estimation accuracy by eliminating contaminating image components.
Solution Approach 2:
The patent changes the analysis parameter from using only the null symbol spectrum to using both null symbol and data symbol spectra in comparison. This parameter change enables the system to distinguish between actual interference and images by analyzing spectral characteristics across different symbol types, thereby improving estimation precision without excessive complexity increase.
Data Source
AI summary
An interference cancellation device includes a data symbol extraction unit that extracts a data symbol portion from a received signal, a null symbol extraction unit that extracts a null symbol portion from the received signal, a data symbol power calculation unit that calculates a data symbol power estimated value, a null symbol power calculation unit that calculates a null symbol power estimated value, a null symbol spectrum calculation unit that calculates a null symbol spectrum from a null symbol signal, and an interference center frequency estimation unit that eliminates the effect of an image for an interference in calculation of an interference bandwidth when is calculating an interference center frequency estimated value, using a data symbol signal, the data symbol power estimated value, the null symbol power estimated value, and the null symbol spectrum.