RFID Tag Singulation via State Information Masking
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Solution Overview
Problem
RFID reader performance decreases significantly in dense environments due to the need to read large numbers of already-identified tags, leading to a substantial decrease in tag reads per second, often experiencing a third-order exponential decay.
Innovation Solution
RFID tags store state information in non-volatile memory, allowing readers to update tags to a quiesced state after identification, preventing them from responding to subsequent interrogations, thus reducing unnecessary reads and increasing reader performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If RFID readers continuously interrogate all tags in dense environments, then complete inventory tracking is achieved, but reader performance deteriorates due to third-order exponential decay in tag reads per second
Solution Approach 1:
The patent extracts already-identified tags from the active interrogation pool by writing their EPC codes to a blacklist in the reader's memory. This removal prevents these tags from being repeatedly read, thereby eliminating the exponential decay effect and maintaining high reading speeds while still achieving complete inventory tracking of unique tags.
Solution Approach 2:
The patent changes the state parameter of identified tags by storing their EPC codes in a blacklist data structure within the reader's memory. This parameter change (from unidentifying to identified) allows the system to differentiate between new and previously seen tags, enabling selective exclusion of known tags from subsequent interrogations and thus maintaining productivity.
2Loss of information
If RFID readers read all tags in the environment, then comprehensive data collection is achieved, but unnecessary re-reading of identified tags increases processing time
Solution Approach 1:
The patent performs preliminary action by maintaining a persistent blacklist in the reader's memory that stores EPC codes of previously identified tags. Before each interrogation cycle, the reader checks this pre-prepared blacklist to determine which tags should be excluded, thereby avoiding unnecessary reading operations and reducing inventory completion time while ensuring no unique tag data is lost.
Solution Approach 2:
The patent implements feedback by continuously updating the blacklist with newly identified tag EPC codes during each interrogation cycle. This feedback mechanism ensures that the system learns from previous readings and progressively refines its reading strategy, eliminating redundant reads of already-identified tags while maintaining complete data collection of unique tags.
3Duration of action of stationary object
If state information is stored in non-volatile memory, then tag state persistence is achieved, but memory space is consumed
Solution Approach 1:
The patent applies local quality by storing state information (EPC codes of identified tags) in a specific localized region of non-volatile memory dedicated to the blacklist function. This localized storage approach allows the system to maintain state persistence across power cycles while consuming minimal memory space, as only the essential identification data is stored rather than complete tag state information.
Data Source
AI summary
A method of interrogating a plurality of RFID tags comprises interrogating a first RFID tag with a read command comprising a masking value for a predefined portion of a User Memory Bank of the first RFID tag. The predefined portion stores state information for the first RFID tag. The masking value corresponds to a non-quiesced state relative to the read command interrogation. The method further comprises receiving a response from the first RFID tag that indicates that the first RFID tag is in the non-quiesced state. The method further comprises interrogating the first RFID tag with a write command that instructs the first RFID tag to write a predefined value to the predefined portion of the User Memory Bank, wherein writing the predefined value to the predefined portion places the first RFID tag in a quiesced state relative to a subsequent read command interrogation comprising the masking value.