OFDM Receiving Apparatus Signal Quality via Pre-FFT Weighting
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Solution Overview
Problem
Existing OFDM receiving apparatuses face challenges in improving the quality of combined signals while maintaining small computation amounts and circuit sizes, particularly due to increased computation requirements for estimating C/N ratios and MER for each symbol, which degrades signal quality and increases apparatus size.
Innovation Solution
The receiving apparatus employs a correction coefficient calculation unit to adjust weighting coefficients based on the intensity of reception signals before Fourier transform, applying these coefficients to all sub-carrier signals within a symbol or frame to weaken the influence of transmission path responses from branches with lower signal intensities, thereby improving the quality of the combined signal without the need for symbol-specific C/N ratio calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If C/N ratio and MER are calculated for each symbol to improve combined signal quality, then signal quality improves, but computation amount increases
Solution Approach 1:
The patent applies preliminary action by calculating correction coefficients based on signal intensity before FFT processing, rather than calculating C/N ratios and MER after FFT. The correction coefficients are determined in advance from the intensities of reception signals before Fourier transform, and then applied to all sub-carrier signals within a symbol or frame. This preliminary determination of weighting coefficients based on pre-FFT signal intensities avoids the need for complex per-symbol C/N ratio calculations while still achieving signal quality improvement.
2Reliability
If C/N ratio and MER are calculated for each symbol to improve combined signal quality, then signal quality improves, but circuit size increases
Solution Approach 1:
The patent applies preliminary action by calculating correction coefficients based on signal intensity before FFT processing, rather than calculating C/N ratios and MER after FFT. The correction coefficients are determined in advance from the intensities of reception signals before Fourier transform, and then applied to all sub-carrier signals within a symbol or frame. This preliminary determination of weighting coefficients based on pre-FFT signal intensities avoids the need for complex per-symbol C/N ratio calculations while still achieving signal quality improvement.
3Reliability
If transmission path response weighting is applied in MRC combining, then combined signal quality improves, but the influence of branches with poor C/N ratio increases
Solution Approach 1:
The patent applies local quality by introducing correction coefficients that selectively adjust the weighting of each branch based on its signal intensity. The correction coefficient for each branch is determined by the ratio of that branch's signal intensity to the maximum signal intensity among all branches. This creates a localized adjustment mechanism where branches with lower signal intensity (and potentially poorer C/N ratio) receive reduced weighting through the correction coefficient, preventing them from degrading the combined signal quality while still allowing MRC to function effectively.
Data Source
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AI summary
To improve a quality of a combined signal obtained by maximum ratio combining performed when a transmission signal of OFDM system is diversity-received with a small computation amount or a small circuit size. In a receiving apparatus, a combining unit corrects, when combining a sub-carrier signal of each branch obtained by performing Fourier transform on a reception signal of each branch at a maximum ratio for each sub-carrier, a weighting coefficient of each branch according to a magnitude relation of an intensity of the reception signal of each branch before Fourier transform. Specifically, the combining unit corrects the weighting coefficient of each branch so as to weaken an influence of a transmission path response estimated for a sub-carrier signal of the branch in branches with smaller reception signal intensities.