CCK Signal Demodulation Using Unreliable Phase Identification
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Solution Overview
Problem
CCK modulation in IEEE 802.11b protocols faces poor demodulation performance due to high resource consumption and processing time, despite existing methods like majority logic decoding, which are resource-efficient but ineffective in reducing noise impact.
Innovation Solution
A multi-stage demodulation method that identifies and determines the most unreliable phase among non-differential phases, calculates determination values, and looks up tables to obtain incoming bits, reducing noise effects and improving demodulation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correlation matching method with FWT algorithm is used for CCK demodulation, then demodulation performance is improved, but calculation complexity and processing time increase significantly
Solution Approach 1:
The patent segments the 8-bit incoming stream into multiple groups (first two bits for DQPSK, remaining six bits for QPSK), and processes each group separately through different modulation schemes. This segmentation allows the use of simpler majority logic decoding for each segment rather than requiring complex full-sequence correlation matching, thereby reducing calculation complexity while maintaining demodulation performance.
Solution Approach 2:
The patent extracts and processes the differential phase component (first two bits through DQPSK) separately from the non-differential phase components (remaining six bits through QPSK). By taking out the differential encoding part and handling it independently, the system avoids the need for complex differential decoding in the correlation matching process, reducing overall calculation complexity.
2Productivity
If majority logic decoding is used for CCK demodulation, then algorithm simplicity and processing speed are improved, but demodulation performance deteriorates due to poor noise immunity
Solution Approach 1:
The patent merges two different decoding approaches: majority logic decoding for the DQPSK-differentiated non-differential phases and correlation matching for the differential phase component. By combining these methods, the system achieves both the processing speed of majority logic and the noise immunity of correlation matching, thereby improving demodulation performance without sacrificing productivity.
Solution Approach 2:
The patent applies different decoding strategies to different parts of the signal: majority logic decoding is applied locally to the non-differential phases (d2-d7) where it provides sufficient performance with high speed, while correlation matching is applied locally to the differential phase (d0-d1) where it provides the necessary noise immunity. This localized application of different methods optimizes both speed and performance.
3Measurement precision
If resource-intensive correlation matching is used, then demodulation accuracy is improved, but resource consumption and processing time increase
Solution Approach 1:
The patent segments the demodulation process into two parts: majority logic decoding for non-differential phases and correlation matching for differential phases. This segmentation allows the system to achieve high demodulation accuracy only where needed (differential phases) while using less resource-intensive majority logic for the remaining phases, thereby reducing overall resource consumption while maintaining accuracy.
Data Source
AI summary
A signal demodulation method is disclosed, which includes: obtaining a complete transmission code word; calculating estimated values of three non-differential phases of the transmission code based on a majority logic; identifying a most unreliable phase among three non-differential phases and determining the other two reliable phases to obtain their determination values; calculating determination values of the rest two phases based on the two determined phases; and looking up in tables based on determination values of the four phases to obtain incoming bits. The demodulation method of the present invention is capable of sufficiently reducing the effect of noise on signal and effectively improving the signal demodulation performance.