Asset Tag Wake Scheduling With Clock Drift Recovery
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Solution Overview
Problem
Existing asset tracking systems face inefficiencies in power management and error recovery, particularly in managing battery life and accurately locating assets with clock desynchronization and unresponsive tags.
Innovation Solution
A system and method for asset tag tracking that includes generating response schedules for unicast and multicast communication modes, utilizing motion sensors to activate ranging, and implementing error recovery protocols to correct clock drift and unresponsive tags, thereby optimizing power consumption and enhancing location accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If asset tags continuously transmit location data, then location tracking accuracy is improved, but battery life deteriorates
Solution Approach 1:
The system implements periodic wake windows where asset tags periodically wake from sleep mode to transmit location data, rather than continuously transmitting. This periodic action allows the tags to remain in low-power sleep mode most of the time while still providing location updates at scheduled intervals, thereby extending battery life while maintaining location tracking capability
Solution Approach 2:
The system performs preliminary actions by predicting asset locations based on historical data and movement patterns, allowing the system to estimate positions between actual transmissions. This preliminary prediction reduces the frequency of required transmissions while maintaining acceptable location accuracy
2Speed
If asset tags wake frequently to check for messages, then response time to triggers is improved, but power consumption increases
Solution Approach 1:
The system uses periodic wake windows scheduled at specific intervals rather than continuous monitoring. Asset tags wake at predetermined times to check for configuration messages and triggers, balancing the need for timely response with power conservation by remaining in sleep mode between wake windows
Solution Approach 2:
The system dynamically adjusts wake window timing and duration based on asset behavior patterns, priority levels, and operational context. High-priority assets or those showing active movement patterns may have more frequent wake windows, while stationary or low-priority assets use extended sleep periods, optimizing the balance between response time and power consumption
3Measurement precision
If unicast communication is used for each asset tag, then location accuracy is improved, but system complexity increases
Solution Approach 1:
The system segments asset tags into groups based on location, priority, or operational characteristics. Within each group, assets can be managed collectively through multicast communications for general updates, while individual unicast communications are used only when specific location precision is required, reducing overall system complexity while maintaining accuracy where needed
Solution Approach 2:
The system implements a dual-mode communication architecture where asset tags can receive both multicast messages (for group updates and general configuration) and unicast messages (for individual location requests and precise tracking). This multi-functionality allows the system to use the most efficient communication mode depending on the specific operational requirement
4Measurement precision
If clock synchronization is continuously maintained, then location accuracy is improved, but power consumption increases
Solution Approach 1:
The system performs preliminary clock synchronization during initial configuration and at scheduled intervals during wake windows, rather than continuously maintaining synchronization. Asset tags use stored timing information and predicted schedules to operate between synchronization events, accepting minor clock drift in exchange for reduced power consumption
Data Source
AI summary
A method includes, generating a schedule for an asset tag, the schedule defining: a unicast trigger time for transmission of a unicast trigger to the asset tag; a transmit time succeeding receipt of the multicast trigger; and a wake window intersecting the transmit time and the receipt of the multiact trigger. The method also includes transmitting the schedule from a node network to the asset tag and configuring the asset tag based on the schedule. The method also includes, at the node network, broadcasting the unicast trigger and, at an asset tag: entering a wake mode; receiving the unicast trigger; transmitting a ranging signal; and entering the sleep mode. The method further includes, at the node network: deriving location of the asset tag based on instance of the ranging signal received by nodes in the node network.