Constellation Symbol Mapping for Harder Eavesdropper Demodulation
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Solution Overview
Problem
Existing constellation mapping methods using Gray code result in low communication security due to the ease of demodulation by eavesdroppers, leading to potential bit errors and unauthorized access.
Innovation Solution
Implement a constellation diagram design where modulation symbols are symmetrical along the horizontal or vertical axis, with specific bit sequence variations, and employ encryption techniques using shared keys and multiple encryption algorithms to enhance security.
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 deliberately introducing asymmetric bit patterns in the constellation diagram design. Specifically, it sets different Hamming distances for different bit positions and directions, breaking the symmetric structure of traditional Gray code mapping. This makes the constellation diagram non-uniform in a controlled way that prevents eavesdroppers from predicting bit patterns while maintaining reliable demodulation for authorized receivers who know the specific asymmetric pattern.
Solution Approach 2:
The patent changes the parameter of Hamming distance from being uniform (as in Gray code where adjacent symbols always have Hamming distance 1) to being variable. Different bit positions have different Hamming distances, and adjacent constellation points may have different Hamming distances depending on their position and direction. This parameter variation creates security against eavesdropping while preserving error correction capabilities for legitimate receivers.
2Reliability
If Hamming distance between adjacent modulation symbols is 1, then demodulation reliability is improved, but security against eavesdropping deteriorates
Solution Approach 1:
The patent applies local quality by making different bit positions have different properties. Specifically, different bit positions (e.g., first bit vs. second bit) have different Hamming distances to their adjacent constellation points. This local differentiation means that error propagation affects different bits differently, and eavesdroppers cannot uniformly predict bit transitions. The local variation in Hamming distance creates security while maintaining overall demodulation reliability through the structured asymmetric design.
3Ease of operation
If bit sequences have uniform Hamming distance, then demodulation simplicity is improved, but security randomness deteriorates
Solution Approach 1:
The patent introduces dynamics by making the Hamming distance a dynamic property that varies based on the constellation point position, bit position, and direction of transition. Rather than a static uniform Hamming distance, the effective Hamming distance changes dynamically depending on which constellation point is being transmitted and which bit position is being considered. This dynamic variation provides security randomness while the underlying structured pattern maintains demodulation simplicity for authorized receivers who know the pattern.
Data Source
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AI summary
This application provides a communication method and apparatus. The method includes: A first communication apparatus may modulate M to-be-sent bits by using a constellation diagram, to obtain a first modulation symbol, and modulate N bits by using the constellation 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 a first bit sequence and a second bit sequence are the same, and a third bit sequence and a fourth bit sequence have different values at a second location; and the first bit sequence is a bit sequence corresponding to a real part of the first modulation symbol, the second bit sequence is a bit sequence corresponding to a real part of the second modulation symbol, the third bit sequence is a bit sequence corresponding to an imaginary part of the first modulation symbol, the fourth bit sequence is a bit sequence corresponding 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 constellation diagram. In this way, randomness of bit sequences corresponding to two adjacent modulation symbols in the constellation diagram is improved, and difficulty in illegally demodulating a transmitted modulation symbol is increased, thereby improving security of communication between the first communication apparatus and the second communication apparatus.