RFID Tracking System Using Zone Segmentation and Transmit-Only Tags
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Solution Overview
Problem
Existing tracking systems for persons and objects in facilities, such as correctional and healthcare settings, are costly and disruptive due to their reliance on multilateration or triangulation techniques, which require extensive hardware, high power consumption, and continuous visibility, often providing more information than needed and suffering from accuracy issues due to building materials.
Innovation Solution
A radio-based tracking system using low-power, transmit-only radio frequency tags with limited range and minimal hardware requirements, where the monitored area is divided into subareas with gateways having shaped fields of view, allowing for reduced hardware and power consumption, and determining presence in specific subareas without continuous detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multilateration or triangulation techniques are used with multiple antennas and receivers, then location determination capability is improved, but system cost and hardware complexity increase significantly
Solution Approach 1:
The system divides the monitored facility into multiple zones, each with a single antenna. Instead of requiring multiple antennas to track a person continuously, the system segments the tracking function across zone boundaries. When a person crosses from one zone to another, the system detects the transition by comparing presence/absence data from adjacent zone antennas, achieving location determination through spatial segmentation rather than continuous multilateration.
Solution Approach 2:
The invention extracts only the essential function needed for tracking - detecting presence/absence in zones - rather than implementing full continuous location determination. By taking out the complex multilateration mathematics and retaining only the binary presence detection capability, the system achieves sufficient tracking functionality with dramatically reduced hardware complexity.
2Loss of information
If RFID tags continuously transmit signals for multilateration, then location visibility is improved, but power consumption increases
Solution Approach 1:
Instead of continuous transmission, RFID tags transmit signals periodically or event-driven. The system detects location by monitoring presence in zones at discrete intervals or triggered by movement events such as zone transitions. This periodic action maintains sufficient location visibility for tracking purposes while dramatically reducing the power consumption compared to continuous transmission required for real-time multilateration.
3Reliability
If multiple wireless access points are installed throughout the facility, then tracking coverage is improved, but installation cost and disruption increase
Solution Approach 1:
The system uses existing wireless access points already present in the facility for their primary networking function, repurposing them to also serve as RFID detection points for tracking. By making the access points multi-functional, the system achieves comprehensive tracking coverage without requiring separate dedicated tracking infrastructure, thereby eliminating installation costs and disruption.
Solution Approach 2:
The system leverages the existing wireless infrastructure that the facility already possesses and maintains. The wireless access points, already installed and powered for networking purposes, automatically serve dual functions by detecting RFID tags in their vicinity. This self-service approach allows the tracking system to utilize existing resources rather than requiring new installations.
4Length of stationary object
If RFID tags transmit at higher power levels for continuous visibility, then detection range is improved, but battery size and recharging requirements increase
Solution Approach 1:
RFID tags transmit at higher power levels periodically rather than continuously. The tags can operate at lower power during idle periods and switch to higher power transmission when movement is detected or at scheduled intervals. This periodic high-power transmission maintains sufficient detection range for zone transition detection while extending battery life by minimizing the duration of high-power operation.
Solution Approach 2:
The system changes the power transmission parameter dynamically based on operational needs. RFID tags adjust their transmit power level according to detected movement, zone transition events, or time-of-day patterns. By varying the power parameter rather than maintaining constant high power, the system achieves adequate detection range when needed while conserving battery energy during stationary periods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly reduces costs and complexity while maintaining accurate tracking of persons and objects within subareas, eliminating the need for constant visibility and minimizing hardware requirements, thus addressing the limitations of existing systems.
Implementation Method 1
a radio frequency transmitter that transmits a unique identifier
Data Source
AI summary
A tracking system that tracks persons and/or objects of interest without the need for triangulation techniques is disclosed. The tracking system utilizes very low power active radio frequency tags with limited effective broadcast range that operate only in the transmit mode with no need to establish two-way communication with any part of the system. The person or object of interest is provided with a radio frequency tag incorporating a unique identifier. Gateways connected to a common network interface are positioned relative to specific areas within the facility to be monitored. A computer connected to the same network as the gateways analyzes data relating to the strength of the of the radio frequency signals received by the radio frequency receivers from the radio frequency tags to determine if, and when, persons and/or objects of interest are present within particular subareas within the facility.