Wireless Node Synchronization via Propagation Delay Compensation

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Solution Overview

Problem

Wireless network systems face challenges in synchronization due to varying clock values and inter-node distances, especially when using orthogonal frequency division multiplexing (OFDM), as existing methods do not effectively account for propagation delays and interference caused by different distances and clock differences.

Innovation Solution

A synchronization method and apparatus that estimate propagation delays between nodes and adjust signal transmission or reception times of neighbor nodes with minimum and maximum propagation delays to ensure alignment within a cycle prefix (CP) period, using a delay estimation unit and synchronization units to manage interference and set optimal FFT start points.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If nodes use beacon-based synchronization without considering propagation delay, then synchronization is simple to implement, but synchronization accuracy deteriorates when inter-node distances vary

Engineering Contradiction:

Improvesynchronization implementation simplicityVSAvoidsynchronization accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent changes the synchronization parameter from simple beacon time reception to propagation-delay-compensated time calculation. Each node calculates its synchronization time by adding the measured propagation delay to the beacon reception time, transforming the synchronization parameter from raw beacon time to compensated time that accounts for distance variations.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements a feedback mechanism where nodes measure propagation delay by comparing transmitted and received beacon times, then use this measured delay to adjust their synchronization. The delay measurement feeds back into the synchronization calculation, creating a closed-loop system that compensates for distance variations.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If nodes at different distances synchronize using the same beacon time, then the synchronization method is universally applicable, but interference increases due to signal arrival time differences

Engineering Contradiction:

Improvesynchronization method applicabilityVSAvoidsignal interference

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent adjusts the transmission time parameter for different nodes based on their propagation delay. Nodes with larger propagation delays advance their transmission time, while nodes with smaller delays delay their transmission, ensuring all signals arrive within the CP period and avoiding interference.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary propagation delay measurement using beacon exchanges before the main data transmission phase. This preliminary action allows nodes to pre-calculate their optimal transmission times, ensuring that subsequent data transmissions from all nodes arrive synchronized at the receiver without interference.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If propagation delay compensation is implemented for all nodes, then synchronization accuracy improves, but system complexity increases due to additional measurement and calculation requirements

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidsynchronization system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements self-service synchronization where each node independently measures its own propagation delay and calculates its synchronization time without requiring complex centralized control. The ranging procedure is performed autonomously by participating nodes, reducing overall system complexity while maintaining high accuracy.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent uses the beacon signal as an intermediary to facilitate propagation delay measurement. The beacon serves as a reference signal that enables nodes to measure time of flight and calculate delays without requiring direct complex interaction protocols, simplifying the measurement process.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Manufacturing precision

If signal transmission times are adjusted to compensate for propagation delays, then signal arrival synchronization improves, but transmission timing flexibility decreases

Engineering Contradiction:

Improvesignal arrival alignment precisionVSAvoidtransmission timing flexibility

Core Design Contradiction:

Manufacturing precisionVSDuration of action of moving object

Solution Approach 1:

The patent implements dynamic transmission timing adjustment where each node's transmission time is adaptively set based on its measured propagation delay. The transmission time parameter becomes dynamic rather than fixed, allowing the system to optimize arrival synchronization while maintaining flexibility through individualized timing calculations for each node.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8755369B2Synchronization apparatus and method in wireless network systems

Publication Date: 2014.06.17 ELECTRONICS & TELECOMM RES INST

AI summary

A node synchronization apparatus in a wireless network system sets a fast Fourier transform (FFT) start point and requests a one-hop neighbor node to change its transmission time. The synchronization apparatus sets a signal receiving time and requests a one-hop neighbor node to change a receiving time. In this way, a node synchronizes signal transmission and signal reception.