Differentially Demodulated Signal Correlation for Wireless Channel Occupancy

Solution Overview

Problem

Existing methods for determining channel occupancy in IEEE 802.15.4 wireless communication systems struggle when the receiver is not yet synchronized, particularly after device startup or wake-up from sleep mode, as they rely on coherent detection methods that are costly and power-intensive.

Innovation Solution

A method using differentially demodulated signals, generated with PN sequences, to correlate with derived subsequences of an initial code sequence, allowing for channel occupancy detection without synchronization, employing a device with sequence providing, correlation, and evaluation units to generate an output signal indicating channel occupancy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If coherent detection methods are used for channel occupancy detection, then detection accuracy is improved, but power consumption increases and device complexity increases

Engineering Contradiction:

Improvedetection accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces expensive, complex coherent detection circuitry with inexpensive, simple correlation-based detection logic that operates on differentially demodulated signals. This allows low-power microcontrollers to perform channel occupancy detection without requiring dedicated hardware correlators or coherent detection units, dramatically reducing power consumption while maintaining adequate detection accuracy for MAC layer operations.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the mechanical/electrical coherent detection system with a signal processing approach using differential demodulation followed by correlation. This replaces complex hardware-based phase and frequency synchronization mechanisms with software-based correlation algorithms that operate on simplified differentially demodulated signals, reducing both hardware complexity and power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If coherent detection methods are used for channel occupancy detection, then detection accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvedetection accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces expensive, complex coherent detection circuitry with inexpensive, simple correlation-based detection logic that operates on differentially demodulated signals. This allows low-power microcontrollers to perform channel occupancy detection without requiring dedicated hardware correlators or coherent detection units, dramatically reducing power consumption while maintaining adequate detection accuracy for MAC layer operations.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the mechanical/electrical coherent detection system with a signal processing approach using differential demodulation followed by correlation. This replaces complex hardware-based phase and frequency synchronization mechanisms with software-based correlation algorithms that operate on simplified differentially demodulated signals, reducing both hardware complexity and power consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If synchronization is required before channel occupancy detection, then detection reliability is improved, but detection time increases and productivity decreases

Engineering Contradiction:

Improvedetection reliabilityVSAvoiddetection speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent performs differential demodulation of the received signal in advance, before channel occupancy detection is needed. This preliminary processing transforms the signal into a form that contains sufficient information for reliable occupancy detection without requiring full synchronization. The differentially demodulated signal can then be correlated with known sequences to determine channel status immediately, eliminating the synchronization waiting period.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the signal representation from the original modulated waveform to differentially demodulated values. This parameter transformation extracts the essential information needed for occupancy detection while discarding the phase and frequency components that would require synchronization. The differential demodulation converts the signal into amplitude-based values that can be directly correlated with known sequences.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS7633996B2Method and device for determining the occupancy of a transmission channel

Publication Date: 2009.12.15 ATMEL CORP

AI summary

A method for determining the occupancy of a transmission channel using a differentially demodulated signal generated at a transmitter-side with the use of PN sequences from a PN sequence set having a first group of first PN sequences and a second group of second PN sequences. The method provides a) at least two subsequences of an initial code sequence, which is assigned to one of the first PN sequences and can be derived from the sequence by logical operations, but is not identical to it, b) the calculation of at least two correlation results by correlating the differentially demodulated signal with each of the at least two subsequences, and c) the evaluation of the correlation results and generation of an output signal to indicate the occupancy of the transmission channel. Also a device for determining the occupancy of a transmission channel.