Wireless Sensor Synchronization Using Timestamp Offset Calculation
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Solution Overview
Problem
Wireless communication systems in avionics face synchronization challenges due to unpredictable packet losses and delays, leading to incorrect mechanical health assessments in aircraft monitoring systems, as sensors may not acquire data simultaneously, and centralized synchronization can be processing-intensive and difficult to manage.
Innovation Solution
A method where wireless sensors receive commands with timestamp values to calculate an offset, allowing them to synchronize with an access point's clock without the need for centralized processing, eliminating direct sensor-to-sensor communication and reducing message collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If centralized synchronization is used to synchronize wireless sensors, then synchronization accuracy is improved, but processing capacity requirements and system complexity increase
Solution Approach 1:
The patent divides the synchronization task into two parts: the access point provides reference timestamps, and each sensor independently calculates its offset using the formula Offset = ((T2 - T1) - (T4 - T3))/2. This segmentation eliminates the need for centralized processing of all sensor data while maintaining synchronization accuracy.
Solution Approach 2:
Each wireless sensor autonomously calculates its own synchronization offset using the received timestamps from the access point and its local clock. The sensor performs self-synchronization without requiring the access point to process or distribute individual offset values to each sensor.
2Ease of operation
If wireless communication is used to replace wired connections in sensor networks, then system reconfiguration ease and installation simplicity are improved, but synchronization reliability deteriorates due to packet losses and delays
Solution Approach 1:
The access point pre-calculates the synchronization offset using timestamps from the wireless communication protocol before data acquisition begins. This preliminary synchronization ensures that all sensors are aligned in time before actual measurement, compensating for potential wireless transmission issues during data collection.
Solution Approach 2:
The access point acts as an intermediary that provides reference timestamps to all sensors. This intermediary role allows sensors to synchronize their local clocks to the access point's time base without requiring direct sensor-to-sensor communication, reducing the impact of wireless packet losses on synchronization.
3Productivity
If multiple sensors acquire data simultaneously using simple command broadcasting, then data acquisition speed is improved, but synchronization accuracy worsens due to unpredictable transmission delays
Solution Approach 1:
The system uses timestamp feedback from the wireless communication protocol to calculate and compensate for transmission delays. Each sensor receives timestamps (T1, T2) from the access point and uses them to determine its offset, enabling accurate phase measurements despite varying transmission times.
Solution Approach 2:
The patent changes the time reference parameter by having each sensor adjust its local clock time based on the calculated offset. This parameter adjustment aligns all sensors to a common time base, ensuring simultaneous data acquisition across the network while maintaining phase measurement accuracy.
Data Source
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AI summary
Synchronizing a wireless sensor includes receiving a first command at the wireless sensor, noting a first timestamp value indicating when the first reply is sent, responding to the first command with a first reply, receiving a second command at the wireless sensor that contains a second timestamp value indicating when the first reply was received and a third timestamp value indicating when the second command was sent to the wireless sensor, noting a fourth timestamp value indicating when the second command was received by the wireless sensor, and determining an offset at the wireless sensor using the first, second, third, and fourth timestamp values. The presence of the first timestamp value may be interpreted as a request to provide timestamp information for synchronization. An access point may communicate with the wireless sensor.