Frequency-Domain Filtering for Radio Frequency Offset Correction
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Solution Overview
Problem
Frequency offset in radio signals causes inter-subcarrier-interference, degrading receiver performance and increasing erroneous decoding decisions, particularly in multi-carrier systems.
Innovation Solution
A method for estimating and correcting frequency offset using real-valued algebraic coefficients computed based on a specific relation between the frequency offset estimate and filter coefficient index, reducing computational complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency offset estimation and correction is performed using conventional complex-valued filter coefficients, then decoding accuracy is improved, but computational complexity and power consumption increase
Solution Approach 1:
The patent changes the parameter type of filter coefficients from complex-valued to real-valued algebraic numbers. This parameter transformation maintains the essential filtering function while dramatically reducing computational complexity. The real-valued coefficients are computed using a specific relation (Equation 6) that avoids complex arithmetic operations, thereby reducing power consumption and computational burden while preserving sufficient decoding accuracy.
Solution Approach 2:
The patent employs simplified real-valued filter coefficients that are computationally cheaper and can be rapidly computed and discarded after use. These coefficients replace expensive complex-valued coefficients, enabling faster processing with reduced computational resources. The coefficients are computed on-demand using a straightforward algebraic relation rather than requiring complex mathematical operations.
2Measurement precision
If frequency offset estimation and correction is performed using conventional complex-valued filter coefficients, then decoding accuracy is improved, but power consumption increases
Solution Approach 1:
The patent transforms the filter coefficient parameter from complex-valued to real-valued algebraic numbers, which significantly reduces the computational operations required. Real-valued arithmetic requires fewer CPU cycles and less energy consumption compared to complex-valued arithmetic. This parameter change maintains adequate filtering performance while dramatically reducing power consumption in mobile radio receivers.
Solution Approach 2:
The patent substitutes complex mathematical operations with simpler algebraic computations. By replacing complex-valued filter coefficient computations with real-valued algebraic relations, the system reduces the mechanical/computational burden on the processor, thereby reducing power consumption. The substitution maintains the essential function of frequency offset correction while using energetically cheaper computational operations.
3Measurement precision
If frequency offset estimation is performed without upper limit constraint, then estimation accuracy is improved, but computation stability deteriorates
Solution Approach 1:
The patent applies a preliminary upper limit constraint to the frequency offset estimate before using it to compute filter coefficients. This preliminary action prevents the estimate from taking on excessively large values that would cause numerical instability in subsequent computations. By pre-limiting the estimate range, the system ensures stable and reliable coefficient computation while maintaining sufficient estimation accuracy for practical applications.
Data Source
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AI summary
This document discloses a solution for reducing a frequency offset. According to an aspect, a method comprises: acquiring a signal distorted by the frequency offset; estimating a frequency offset estimate describing the frequency offset; computing coefficients for a frequency-domain filter on the basis of a relation between the frequency offset estimate and a combination of the frequency offset estimate and an index of the frequency-domain filter; and performing frequency-domain filtering of the signal by using the computed coefficients.