Phase Rotation Demodulation for Overlay Symbol Detection
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Solution Overview
Problem
Existing communication and navigation systems face challenges in increasing the amount and types of information transmitted without degrading the frequency spectrum, particularly in maintaining minimal impact on the host waveform during watermarking or data overlay, especially in environments like urban multipath and jamming.
Innovation Solution
The implementation of phase rotation watermarking, which rotates the continuous, antipodal phase transitions of host symbols in a consistent direction based on overlay symbol states, allowing for the efficient superimposition of additional data onto phase modulated signals without significant degradation, applicable to BPSK, QPSK, and M-ary PSK waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If conventional watermarking methods are used to overlay additional data on host waveform, then authentication information can be transmitted, but significant degradation occurs to the underlying host waveform performance
Solution Approach 1:
The patent embeds watermark information in the phase rotation dimension of the host signal. By rotating the phase of the host waveform in specific directions (clockwise or counter-clockwise) based on watermark bits, additional data is transmitted along the phase trajectory without significantly altering the amplitude or frequency characteristics of the host signal, thus minimizing degradation to host waveform performance while enabling authentication information transmission
2Reliability
If watermark energy is increased to improve robustness in weak signal environments, then detection reliability improves, but frequency spectrum degradation increases
Solution Approach 1:
The patent modulates the phase rotation angle parameter to encode watermark information. By varying the phase rotation direction (positive or negative angles) rather than increasing amplitude energy, the system achieves robust detection in weak signal environments while avoiding frequency spectrum degradation that would result from energy-intensive amplitude-based watermarking methods
3Loss of information
If phase transitions are rotated in different directions for different host symbols, then overlay data capacity increases, but demodulation complexity increases
Solution Approach 1:
The patent segments the host signal into groups of consecutive symbols, where each group is rotated in the same direction according to a single overlay symbol. This segmentation approach maintains high overlay data capacity while simplifying demodulation, as the receiver only needs to determine the rotation direction for each segment rather than analyzing each individual symbol independently
Data Source
AI summary
A method of demodulating a signal that is phase modulated to convey R chips having phase transitions between adjacent ones of the R chips to represent chip states, and an overlay symbol spanning the R chips, wherein R>1, and wherein the phase transitions are rotated in a same direction according to an overlay symbol state, comprises: first processing the signal including: accumulating a respective phase of each chip into a respective first chip magnitude, to produce R first chip magnitudes; and accumulating the R first chip magnitudes to produce a first magnitude; second processing the signal including: accumulating a respective phase of each chip into a respective second chip magnitude, to produce R second chip magnitudes; and accumulating the R second chip magnitudes to produce a second magnitude; and determining the overlay symbol state based on the first magnitude and the second magnitude.