OFDM CINR Estimation via Sub-carrier Correlation and Difference
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Solution Overview
Problem
Conventional SNR estimation methods in OFDM systems suffer from performance degradation when the number of unused sub-carriers is small and are unable to estimate interference signals, as interference from other users cannot be detected in unused sub-carriers.
Innovation Solution
An apparatus and method that estimates noise power by correlating sub-carriers with a reference sequence, calculating differences between adjacent sub-carriers to isolate interference and noise components, and using these differences to calculate noise and interference power, thereby estimating the carrier-to-interference and noise ratio (CINR) in OFDM/OFDMA/DMT systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conventional SNR estimation method using unused sub-carriers is applied, then the noise level can be measured from unused sub-carriers, but the estimation performance degrades extremely when the number of unused sub-carriers is very small compared with the number of used sub-carriers
Solution Approach 1:
The patent extracts and processes used sub-carriers (which carry signal and noise) by correlating them with a reference sequence and calculating differences between adjacent sub-carriers. This extraction approach allows noise estimation without relying on unused sub-carriers, resolving the contradiction when unused sub-carriers are scarce.
Solution Approach 2:
The patent performs preliminary correlation of received sub-carriers with a reference sequence before noise estimation. This preliminary action prepares the signal components for subsequent difference calculation, enabling accurate noise extraction even when unused sub-carriers are limited.
2Measurement precision
If the conventional SNR estimation method is used, then the noise level can be estimated from unused sub-carriers, but the interference signal from other users cannot be estimated because interference does not enter unused sub-carriers
Solution Approach 1:
The patent extracts both signal and interference components by correlating used sub-carriers with a reference sequence. The difference calculation between adjacent sub-carriers then isolates the interference and noise components, enabling interference estimation that was impossible with unused sub-carriers alone.
Solution Approach 2:
The patent segments the received signal into signal components and interference/noise components through correlation and difference operations. This segmentation allows separate estimation of interference and noise, providing comprehensive signal quality measurement.
3Reliability
If sub-carriers are correlated with a reference sequence and differences between adjacent sub-carriers are calculated, then signal components are canceled out and only interference and noise components remain, but this requires additional processing operations
Solution Approach 1:
The patent converts the presence of signal components in used sub-carriers (which was a problem in conventional methods) into a benefit. By correlating with a reference sequence and calculating differences, the signal components cancel out, leaving only interference and noise for accurate estimation.
Data Source
AI summary
A method and apparatus for estimating interference and noise power in an orthogonal frequency division multiplexing/orthogonal frequency division multiple access/discrete multi-tone (OFDM/OFDMA/DMT) system is disclosed. A correlator correlates a plurality of sub-carriers with a preset reference sequence on an element-by-element basis and outputs a result of the correlation. A signal noise producer calculates a difference between a correlation value associated with each of the plurality of sub-carriers output from the correlator and a correlation value produced from at least one adjacent sub-carrier and outputs a result of the calculation. An interference and noise power producer produce interference and noise power from the difference between the correlation values calculated by the signal noise producer.