Phase-Shift Keying Demodulation via Peak Bins in GNSS Wearables

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Solution Overview

Problem

GNSS receivers, particularly those embedded in wearable devices, face challenges in demodulating navigation messages due to rapidly varying Doppler shifts caused by arm movements, leading to bit-errors and unsuccessful decoding.

Innovation Solution

A method that converts sequences of samples to a frequency-domain representation and identifies symbols or symbol-transitions based on the frequency bin with the maximum magnitude, using a decision variable and a reference variable from a preceding symbol period, to enhance robustness against frequency shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional demodulation methods are used in wearable devices, then device simplicity is maintained, but demodulation reliability deteriorates due to rapidly varying Doppler shifts

Engineering Contradiction:

Improvedemodulation reliabilityVSAvoidDoppler shift effects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the domain parameter from time-domain to frequency-domain representation. By converting the time-domain signal to frequency-domain samples and identifying the frequency bin with maximum magnitude, the method makes the demodulation process robust against frequency shifts caused by Doppler effects, thereby improving demodulation reliability in wearable devices.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If frequency-domain conversion is applied to mitigate Doppler shifts, then demodulation robustness improves, but computational complexity increases

Engineering Contradiction:

Improvedecoding success rateVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts only the essential information needed for demodulation by identifying the frequency bin with maximum magnitude in the frequency-domain representation. This extraction approach obtains the necessary phase and frequency information without requiring complex tracking loops or extensive processing, thus achieving high decoding success rate with manageable computational complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

3Measurement precision

If tracking loops are used to compensate for frequency changes, then bit detection accuracy is maintained, but system complexity and processing overhead increase

Engineering Contradiction:

Improvebit detection accuracyVSAvoidtracking loop complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical tracking loop system with a frequency-domain analysis approach. Instead of using complex tracking loops to continuously adjust and compensate for frequency changes, the method converts the signal to frequency-domain samples and directly identifies the maximum magnitude bin, thereby maintaining bit detection accuracy while eliminating the complexity of tracking loops.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentEP4012455B1Demodulating a wireless signal modulated by phase-shift keying

Publication Date: 2025.07.09 U-BLOX

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AI summary

A method and apparatus are provided for demodulating a wireless signal modulated by phase-shift keying. The signal comprises a plurality of symbols. The method comprises: obtaining (310) a first sequence of samples based on the signal; converting (320) the first sequence of samples to a first sequence of frequency domain samples; selecting (330), as a decision variable, the sample that has the maximum magnitude among the first sequence of frequency domain samples; and identifying (340) a symbol or a symbol-transition based on the decision variable.