RFID Tag Position Tracking Using Phase Detection
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Solution Overview
Problem
Current RFID systems face challenges in accurately tracking the position and motion of tags in a retail environment due to limitations in RFID reader protocols, interference from multiple tags, and the inability to read tags quickly enough to determine their location and direction, especially when thousands of tags are present, leading to inaccurate analytics and potential security breaches.
Innovation Solution
Implementing a system where RFID tags are assigned short local addresses, allowing for faster and more deterministic reading of tags in motion, using a ping command to receive phase information, and employing motion-based communication schemes to isolate moving tags, enabling accurate tracking and alarming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If standard RFID inventory protocols are used to read tags, then tags can be identified, but the reading speed is too slow to accurately track tag position and motion in real-time
Solution Approach 1:
The patent segments the RFID reading process into two distinct phases: a fast ping phase for position tracking using short addresses, and a detailed inventory phase for full EPC reading. This segmentation allows the system to prioritize speed during tracking while maintaining accuracy when needed, resolving the contradiction between reading speed and position tracking accuracy.
Solution Approach 2:
The system dynamically switches between different reading modes based on operational needs. During motion detection, the system uses fast ping commands with short addresses for rapid position updates. When full identification is needed, it transitions to standard inventory protocols. This dynamic adaptation allows optimal performance for both speed and accuracy depending on the operational context.
2Area of stationary object
If RFID readers broadcast signals to cover large areas, then more tags can be detected, but the directional accuracy and ability to determine tag motion is lost
Solution Approach 1:
The patent segments the monitoring function across multiple readers positioned at different locations. Each reader covers a specific zone and uses phase difference measurements to determine tag position relative to that zone. By combining data from multiple segmented readers, the system achieves both wide coverage and precise directional accuracy.
Solution Approach 2:
The system uses phase difference as an intermediary measurement to indirectly determine tag position and motion direction. Instead of requiring direct line-of-sight tracking, the phase information from multiple readers serves as a mediator that enables accurate position and motion calculation even when tags move quickly or change direction.
3Quantity of substance
If multiple tags are present in the RFID environment, then inventory coverage is improved, but interference and collisions increase making accurate tracking difficult
Solution Approach 1:
The patent segments the tag identification process by using short addresses for rapid ping commands that can be sent to multiple tags simultaneously without interference. This segmentation of the communication protocol allows the system to track multiple tags in parallel, increasing the number of trackable tags while maintaining reliability through collision-free communication.
Solution Approach 2:
The system performs preliminary actions by assigning and using short addresses for tags before full inventory reading. This preliminary identification allows the system to rapidly establish trackable tags and their positions, enabling multi-tag tracking to proceed efficiently without interference from other tags during the tracking phase.
4Measurement precision
If single tag selection commands are used to improve tracking accuracy, then position determination is more precise, but the command speed becomes 3 times slower than normal inventory commands
Solution Approach 1:
The patent segments the command structure into ping commands with short addresses for rapid position tracking, and separate full inventory commands for detailed reading. This segmentation allows the system to use fast ping commands for continuous position monitoring without the speed penalty of full single-tag selection protocols, while maintaining accuracy when needed.
Solution Approach 2:
The system uses partial action by reading only the necessary short address information during ping commands for position tracking, rather than performing complete tag selection and full EPC reading for every position update. This partial reading approach maintains sufficient accuracy for tracking while executing commands at much higher speed.
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 allows for the reliable and accurate tracking of multiple tags in real-time, increasing read speed by 16 times, reducing errors, and enhancing security by ensuring valid alarms and precise analytics in a busy retail environment.
Implementation Method 1
Using Radio Frequency Identification ('RFID') tags for tracking of items going in or out of a retail store or secured location
Implementation Method 2
determining a first position of the first tag in the given area based on the phase of the ping command response signal
Data Source
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AI summary
Systems and methods for determining a tag's position in a given area. The methods comprise: performing, by a tag reader, a standard inventory process to obtain a unique identification code for a first tag in a randomly selected timeslot; assigning, by the tag reader, a local short address to the first tag that is shorter than the unique identification code; wirelessly communicating the local short address from the tag reader to the first tag; performing, by the tag reader, an enhanced inventory process to receive a ping command response signal including the local short address from the first tag in an assigned timeslot; and determining a first position of the first tag in the given area based on the phase of the ping command response signal.