RF Tag Wake Scheduling for Low-Power Indoor Localization
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Solution Overview
Problem
Existing indoor localization systems face a trade-off between energy efficiency and accuracy, as they often keep RF tags in an active state for frequent transmissions, leading to high energy consumption despite efforts to improve energy efficiency by using hibernation states.
Innovation Solution
RF tags switch between active and inactive states only when necessary, using a reveille time determined by their ID and the DP's ID to wake up and communicate, and return to hibernation immediately after, while also implementing a two-way authentication mechanism for security and using a 'listen before transmit' approach to conserve energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RF tags are kept in an active state for frequent transmissions to update locations, then localization accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic wake-up cycles where RF tags alternate between hibernation and active states. Tags wake up at predetermined intervals to exchange location data with detection points, then return to hibernation. This periodic operation maintains acceptable localization accuracy while dramatically reducing energy consumption compared to continuous active operation.
Solution Approach 2:
The system performs preliminary actions by pre-scheduling wake-up times and pre-establishing communication protocols before tags need to be active. Detection points continuously broadcast wake-up signals, and tags prepare to wake up at predetermined times, eliminating the need for continuous monitoring and reducing energy consumption while maintaining system responsiveness.
2Use of energy by moving object
If RF tags switch to hibernation state to save power, then energy efficiency is improved, but the system requires wakeup signals and continuous readiness which limits energy savings
Solution Approach 1:
RF tags autonomously determine their own wake-up schedules based on predetermined algorithms and local clocks, eliminating the need for complex centralized scheduling. Each tag independently calculates when it should wake up and communicates with detection points only during these self-determined intervals, simplifying the overall system architecture while maintaining energy efficiency.
Solution Approach 2:
The system uses periodic wake-up cycles with predetermined intervals between active and hibernation states. This regular pattern simplifies the wakeup mechanism compared to event-driven approaches, as both tags and detection points can anticipate communication events, reducing the complexity of signal processing and state management.
3Reliability
If RF tags remain active after receiving wakeup signals to maintain network readiness, then communication reliability is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic communication cycles where tags wake up, exchange data with detection points, and then return to hibernation. This periodic operation ensures reliable communication at predetermined intervals while minimizing the duration of active states, thereby reducing energy consumption compared to maintaining continuous network readiness.
Solution Approach 2:
The system dynamically adjusts the balance between reliability and energy consumption by optimizing wake-up intervals and active durations. Tags transition between hibernation and active states based on predetermined schedules and communication needs, creating a dynamic operational mode that adapts to system requirements while minimizing energy usage.
4Use of energy by moving object
If tags use imprecise clocks for hibernation timing to save power, then energy efficiency is improved, but synchronization accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where detection points with precise clocks broadcast timing information to tags during wake-up cycles. Tags use this feedback to correct their imprecise local clocks, ensuring synchronization accuracy is maintained despite using low-power imprecise timing hardware during hibernation. The feedback loop compensates for clock drift without requiring continuous precise timing operation.
Solution Approach 2:
The system uses periodic synchronization events where tags wake up at predetermined intervals not only to exchange location data but also to recalibrate their imprecise clocks against the precise clocks of detection points. This periodic correction maintains synchronization accuracy while allowing tags to use energy-efficient imprecise clocks during hibernation periods.
Data Source
AI summary
The present invention is directed to energy-efficient hibernation in indoor wireless localization systems. A tag passively associates with a detection point (DP) and establishes a reveille time. The tag will awaken at the reveille time and send or receive a beacon to or from its associated DP. If the tag is receiving a beacon, it will awaken, receive, phase-lock its clock based on when the beacon was expected and when it was actually received, and return to hibernation. The DP transmits a scattershot of beacons, one for every tag in the system. If the tag is sending a beacon, it will awaken, send its beacon, and return to hibernation. The DP will receive the beacon and adjust its own clock based on the delay between when the beacon was expected and when it was actually received. The tag will broadcast its location to the DP on a set interval.