Wireless Sensor Network Time Synchronization via Dynamic Polling
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Solution Overview
Problem
Wireless sensor networks in aerospace applications face challenges with precise time synchronization due to variable time drifts in nano-power timing circuits, leading to data loss and unreliable communication, especially in low data rate and low duty cycle operations.
Innovation Solution
A wireless sensor network architecture that includes a timing circuit with a duty cycle featuring a sleep and wake duration, where the network manager adapts polling request schedules based on receipt times, sleep duration, and timing circuit tolerance, ensuring synchronization and reducing radio frequency emissions and channel congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the wireless node uses a low-power timing circuit to extend battery life, then energy efficiency is improved, but time synchronization precision deteriorates due to variable time drifts
Solution Approach 1:
The patent introduces a coordinator node as an intermediary that maintains a reference clock and manages time synchronization for all wireless nodes. The coordinator receives timing information from nodes, processes it against the reference clock, and sends correction data back to nodes, thereby mediating between the low-precision node clocks and the high-precision network time requirement
Solution Approach 2:
The patent implements a feedback mechanism where wireless nodes transmit their timing information to the coordinator, which compares it with the reference clock and sends timing correction data back to the nodes. This closed-loop feedback system allows nodes with low-power, low-precision timing circuits to maintain accurate synchronization with the network
2Loss of energy
If the wireless node operates in low duty cycle mode to save energy, then power consumption is reduced, but time synchronization reliability deteriorates due to disconnection and reconnection issues
Solution Approach 1:
The patent implements preliminary actions by having the coordinator send timing advance information to nodes before they go into sleep mode, and by pre-scheduling polling requests during the node's wake periods. This allows nodes to maintain synchronization without needing to remain continuously connected
Solution Approach 2:
The patent uses periodic action by implementing duty cycle-based operation where nodes alternate between sleep and wake periods, with the coordinator sending polling requests and timing corrections at regular intervals during the node's active periods. This periodic interaction maintains synchronization while allowing energy-saving sleep modes
3Measurement precision
If the network increases polling request frequency to maintain synchronization, then time synchronization quality is improved, but channel congestion and radio frequency emissions increase
Solution Approach 1:
The patent implements dynamic adaptation by having the coordinator adjust polling request frequencies and timing based on each node's specific duty cycle, wake periods, and synchronization needs. This dynamic scheduling optimizes synchronization quality while minimizing channel congestion by polling nodes only when necessary
Solution Approach 2:
The patent changes the parameter of polling frequency from a fixed value to a variable parameter that adapts to each node's operational state, duty cycle, and synchronization requirements. This allows the system to maintain synchronization quality while reducing overall channel congestion by polling less frequently for nodes that don't need frequent updates
Data Source
AI summary
Systems and methods are described for time synchronization and message scheduling among network elements involving wireless nodes, data controllers, and a network manager. The network manager provides configuration information for the data controllers and the wireless nodes. The wireless node includes a timing circuit with a duty cycle which is initially configured based on the configuration information. Subsequent to the initial configuration, the network manager schedules polling requests for the data controller to transmit to the wireless nodes based on a time at which sensor data is received from the wireless nodes, thereby correcting for timer drift.