Contactless Card Identification via Correlator Scanning
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Solution Overview
Problem
Contactless card readers face challenges in efficiently identifying multiple cards within an interrogation field due to signal collisions, requiring lengthy deterministic or probabilistic anti-collision methods to individually select each card.
Innovation Solution
A system and method utilizing a correlator in the reader to scan encoded identifier signals, allowing for bulk identification of contactless cards by generating and encoding unique identifiers resistant to collisions, using pseudo-random number generators and error correction codes to discriminate between multiple transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If deterministic anti-collision methods are used to identify multiple contactless cards, then each card can be individually identified, but the identification process becomes lengthy and time-consuming
Solution Approach 1:
The system performs preliminary actions by having cards pre-generate random numbers and pre-calculate time slot assignments before the actual identification process. When a collision is detected, the cards can immediately resume transmission in their assigned time slots without needing to re-negotiate or re-generate identification sequences, significantly reducing the time required for multi-card identification while maintaining deterministic accuracy
Solution Approach 2:
The system dynamically adjusts the identification process by combining deterministic time slot assignment with probabilistic collision resolution. When collisions occur, the system transitions to a probabilistic resumption mode where cards randomly select time slots to retry, then returns to deterministic mode once collisions are resolved. This dynamic approach reduces overall identification time compared to purely deterministic methods
2Productivity
If probabilistic anti-collision methods are used to identify multiple contactless cards, then identification speed improves, but reliability decreases when the number of cards increases
Solution Approach 1:
The identification process is segmented into distinct phases: an initial deterministic phase where cards are assigned specific time slots based on their identification numbers, and a probabilistic phase where colliding cards randomly select time slots for retry. This segmentation allows the system to maintain high reliability through deterministic assignment while achieving fast identification speed through probabilistic collision resolution
Solution Approach 2:
The system changes the operational parameters of the identification process based on the detection of collisions. When no collisions occur, the system operates in deterministic mode with fixed time slot assignments. When collisions are detected, it transitions to probabilistic mode where cards randomly select time slots, effectively changing the parameter from deterministic to probabilistic to resolve the conflict and maintain reliability
3Quantity of substance
If the number of time slots is increased to improve probabilistic anti-collision effectiveness, then more cards can be identified simultaneously, but the system complexity increases
Solution Approach 1:
The system applies different quality levels to different time slots based on local needs. Time slots are not uniformly used; instead, the system dynamically activates only the necessary number of time slots based on the detected number of cards and collision patterns. This local optimization reduces the effective complexity of time slot management while maintaining the capability to handle large numbers of cards when needed
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
Enables rapid and efficient identification of multiple contactless cards without the need for lengthy individual identification processes, improving the speed and accuracy of card selection in crowded interrogation fields.
Implementation Method 1
the reader typically transmits an electromagnetic carrier wave. This transmitted carrier wave serves on the one hand to power the contactless card, which derives by induction the energy required for its operation
Data Source
AI summary
A communication system includes at least one contactless card configured to transmit an encoded identifier; and a reader configured to receive the encoded identifier and compare the received encoded identifier with an encoded reference card identifier, wherein the reader requests data from the contactless card if the encoded identifier matches the encoded reference card identifier.