RSSI Tag Location Estimation via Zone Segmentation
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Solution Overview
Problem
Existing RSSI-based algorithms for determining the location of EAS tags in retail environments face uncertainties due to factors like antenna loading and spatial orientation, leading to inaccuracies in identifying the presence and location of security tags within interrogation zones.
Innovation Solution
The method involves combining multiple received RSSI signals from detectors to estimate a tag's position by creating and correlating RSSI profiles for different zones and orientations, using a computing device to determine the likelihood of a tag's location within specific zones or areas, and employing statistical analysis to enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RSSI-based algorithms are used to determine tag location, then location estimation can be obtained, but measurement precision deteriorates due to antenna loading and spatial orientation uncertainties
Solution Approach 1:
The patent divides the interrogation zone into multiple discrete zones and creates separate RSSI profiles for each zone. By segmenting the detection area and using multiple detectors positioned at different locations, the system can identify which specific zone a tag is in based on RSSI patterns, thereby improving location precision despite signal uncertainties.
Solution Approach 2:
The patent introduces spatial orientation as an additional dimension for location determination. By analyzing the spatial relationship between multiple detectors and the tag, and considering different tag orientations (e.g., vertical, horizontal, diagonal), the system disambiguates location estimates that would otherwise be uncertain due to signal scattering and loading effects.
2Measurement precision
If multiple detectors are used to improve location accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes each detector serve multiple functions: detecting tag presence, measuring RSSI for location estimation, and providing spatial orientation information. The same detector array used for basic EAS detection is also utilized for precise location determination, eliminating the need for separate location-specific hardware and reducing overall system complexity.
Solution Approach 2:
The patent creates RSSI profiles that serve as reference copies of expected signal patterns for different zones and orientations. By comparing actual RSSI measurements against these pre-established profile copies, the system can quickly determine tag location without complex real-time calculations, simplifying the processing architecture.
3Measurement precision
If RSSI profiles are created for different zones and orientations, then location determination accuracy improves, but loss of information increases due to the need to store and correlate multiple profiles
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing RSSI profiles for all possible zones and orientations before actual tag detection. This offline profile creation allows the system to quickly match measured RSSI patterns against known profiles during operation, reducing real-time computational burden and information processing overhead while maintaining high accuracy.
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 approach improves detection accuracy by averaging RSSI values and using relational ratios to discriminate between tag orientations and distances, effectively reducing uncertainties and enhancing the precision of tag location determination within retail store environments.
Implementation Method 1
The RFID element can be interrogated by an RFID reader to obtain RFID data therefrom
Implementation Method 2
A security tag with an EAS element (e.g., an acousto-magnetic element) can be attached to an article offered for sale
Data Source
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AI summary
Systems (100) and methods for determining a location of a tag (310). The methods involve : receiving, at each detector of a plurality of detectors (202-216, 306, 308), a device transmission periodically transmitted from the tag; determining, by the detectors, Received Signal Strength indictors ("RSSIs") for the device transmission received thereat; determining, by a computing device (218), a probable location of the tag within the passage, first demarcated area or second demarcated area using the RSSIs and relationships between the RSSIs; determining a first likelihood value indicating the likelihood that the probable location is correct; and determining an estimated location of the tag within the passage, first demarcated area or second demarcated area based on the probable location when the first likelihood value meets a first criteria.