Phase Domain MLSD for Wireless Sensor Networks
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Solution Overview
Problem
Low-power wireless sensor and actor networks face performance compromises due to high packet error rates and complex modulation index estimation in continuous phase modulation, making optimal detection schemes like Maximum Likelihood Sequence Detection (MLSD) infeasible.
Innovation Solution
A wireless device translates in-phase and quadrature components into a phase domain signal, estimates and corrects coherence parameters, and enables Maximum Likelihood Sequence Detection by equalizing the modulation index to a predetermined value, simplifying the detection process and improving signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Maximum Likelihood Sequence Detection (MLSD) is implemented for CPM signals, then detection performance (BER/PER) is maximized, but device complexity increases exponentially due to modulation index-dependent trellis structure
Solution Approach 1:
The patent transforms the detection problem by changing the domain parameter from time-domain I/Q components to phase-domain representation. This parameter transformation simplifies the noise characteristics to white and Gaussian, enabling MLSD implementation with reduced complexity while maintaining optimal detection performance.
Solution Approach 2:
The patent introduces a phase-domain transformation as an intermediary step between signal reception and detection. This intermediary representation simplifies the relationship between modulation index and trellis structure, making the detection scheme less sensitive to modulation index variations and reducing overall system complexity.
2Adaptability or versatility
If modulation index estimation and equalization is performed for variable modulation index, then adaptability improves, but implementation becomes infeasible due to nonlinear estimation complexity
Solution Approach 1:
The patent enables the detection system to automatically adapt to variable modulation indices through the phase-domain transformation, which inherently simplifies the estimation process. The system serves itself by making the nonlinear estimation problem tractable through domain transformation, eliminating the need for complex external estimation algorithms.
Solution Approach 2:
By changing to phase-domain representation, the patent transforms the nonlinear modulation index estimation problem into a simpler form that can be handled more easily, enabling variable modulation index capability without prohibitive complexity increases.
3Use of energy by moving object
If low-power wireless communication is implemented with simplified protocols, then power consumption is reduced, but packet error rate increases leading to more retransmissions
Solution Approach 1:
The patent implements a feedback mechanism where the phase-domain detection continuously estimates and tracks the modulation index, allowing the system to maintain optimal detection performance despite variations in communication conditions. This feedback loop reduces packet errors without requiring increased power consumption for retransmissions.
Data Source
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AI summary
A wireless device, and corresponding method, having a receiver configured to receive a signal having in-phase and quadrature components; a non-linear filter demodulator configured to translate noncoherently the in-phase and quadrature components into a phase domain signal; a coherence acquisition unit configured to estimate and correct at least one coherence parameter based on the in-phase and quadrature components and the phase domain signal; and a detector configured to detect information in the phase domain signal.