Wireless Sensor Network Node Synchronization via Timestamped Response

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Solution Overview

Problem

Current wireless sensor network (WSN) synchronization methods require extensive message exchanges, lead to significant energy consumption, and do not account for propagation times between nodes, making them inefficient for indoor deployments and mobile node scenarios.

Innovation Solution

A method where a reference node broadcasts a synchronization message with a timestamp, and second nodes respond with their own timestamps, allowing for the estimation of propagation times and synchronization without prior measurement, reducing energy consumption and message exchanges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If RBS synchronization protocol is used, then nodes can synchronize with each other using broadcast beacons, but the number of message exchanges increases significantly (O(N^2)) leading to high energy consumption and slow convergence

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent extracts only the essential synchronization information (timestamps and propagation time estimates) from complex broadcast protocols. Instead of requiring O(N^2) message exchanges, each node only needs to exchange messages with its parent node in the spanning tree, reducing the message complexity to O(N) while maintaining synchronization accuracy through selective information extraction.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The synchronization process is segmented into two distinct phases: (1) propagation time estimation phase where nodes calculate their distance from the root based on timestamp differences, and (2) clock offset compensation phase where nodes adjust their local clocks. This segmentation allows each phase to be optimized independently, reducing overall energy consumption.

Inventive Principle:

Principle #1Segmentation

2Productivity

If TPSN protocol is used, then synchronization convergence is faster with fewer messages, but the protocol requires tree organization and frequent updates for mobile nodes leading to high energy consumption

Engineering Contradiction:

Improvesynchronization speedVSAvoidenergy consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic parent selection where mobile nodes can change their parent node in the spanning tree based on current network conditions and topology. This dynamic adaptation allows the system to maintain fast synchronization convergence without requiring frequent complete tree reorganizations, thereby reducing energy consumption while accommodating mobile nodes.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If FTSP protocol is used, then all nodes can be synchronized to root without tree structure, but periodic root changes and repeated synchronization processes consume significant energy and bandwidth

Engineering Contradiction:

Improvetopology flexibilityVSAvoidenergy consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent performs preliminary propagation time estimation during the initial spanning tree construction phase. Once the tree is established, nodes have pre-calculated their propagation times to the root, eliminating the need for periodic re-estimation when root nodes change. This preliminary action significantly reduces energy consumption in subsequent synchronization operations.

Inventive Principle:

Principle #10Preliminary action

4Device complexity

If synchronization methods assume negligible propagation delays, then clock offsets can be determined from broadcast messages, but this assumption is generally not valid in WSN networks leading to synchronization errors

Engineering Contradiction:

Improveprotocol simplicityVSAvoidsynchronization precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent implements feedback mechanisms where nodes measure the actual propagation time by comparing timestamps of broadcast and response messages. These measured propagation times are fed back into the synchronization calculation to compensate for transmission delays. This feedback loop maintains synchronization precision without significantly increasing protocol complexity.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP3253139B1Method for synchronising nodes in a wireless sensor network

Publication Date: 2019.02.27 MAPLE HIGH TECH

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AI summary

The invention relates to a method for synchronizing nodes in a wireless sensor network (WSN) comprising a reference node (Ar). This method allows for the post-facto synchronization of a set of secondary nodes Ai, i = 1, ..., N, upon the occurrence of a given event observed by both the reference node Ar and the secondary nodes Ai. Synchronization is achieved by the broadcast of a synchronization message by the reference node and by the response of each of the secondary nodes to the reference node. The synchronization message and the received messages are timestamped both upon transmission and reception by the local clocks of the nodes. The reference node estimates, from the timestamp values, the respective times at which the event was observed by the secondary nodes, these times being measured relative to a reference clock.The synchronization method can be applied, in particular, to the location of a tag in a wireless sensor network.