Constellation Mapping for Secure Demodulation in Communication Links
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Solution Overview
Problem
Current constellation mapping methods using Gray code mapping rules in communication systems are vulnerable to eavesdropping, leading to low communication security due to the ease of demodulation by unauthorized entities.
Innovation Solution
Implement a constellation diagram design where modulation symbols are symmetrical along the horizontal or vertical axis, with specific bit sequence variations, and enhance security through encryption using shared keys and multiple encryption algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Gray code mapping rule is used for constellation diagram, then bit error rate is reduced, but communication security deteriorates
Solution Approach 1:
The patent applies asymmetry by breaking the symmetric Gray code mapping pattern. Specifically, it inverts the mapping relationship for certain constellation points (e.g., when the most significant bit is 1, invert the mapping; when it's 0, use normal mapping). This creates an asymmetric mapping that maintains the Hamming distance property for error resilience while preventing eavesdroppers from predicting bit patterns, thus resolving the contradiction between reliability and security.
2Measurement precision
If modulation symbols are arranged with Hamming distance of 1, then demodulation accuracy is improved, but susceptibility to eavesdropping increases
Solution Approach 1:
The patent introduces dynamics by making the mapping relationship variable rather than static. The mapping rule changes based on the value of the most significant bit, creating two different mapping patterns. This dynamic adaptation maintains consistent Hamming distance properties for accurate demodulation while varying the bit patterns to prevent eavesdroppers from establishing fixed prediction rules, thus resolving the contradiction between demodulation accuracy and eavesdropping vulnerability.
Data Source
AI summary
An apparatus modulates M bits by a constellation diagram, to obtain a first modulation symbol, and modulates N bits by the diagram, to obtain a second modulation symbol, where a first bit sequence and a second bit sequence have different values at a first location, and a third bit sequence and a fourth bit sequence are the same; or vice versa; and the first bit sequence corresponds to a real part of the first modulation symbol, the second bit sequence corresponds to a real part of the second modulation symbol, the third bit sequence corresponds to an imaginary part of the first modulation symbol, the fourth bit sequence corresponds to an imaginary part of the second modulation symbol, and the first modulation symbol and the second modulation symbol are symmetrical along a horizontal axis or a vertical axis of the diagram.