Backscattering RFID Tag Frequency Separation for Reader Interference
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Solution Overview
Problem
In overcrowded RFID reader environments where the number of readers exceeds the number of frequency channels, backscattering type RFID communications face interference issues due to overlapping query and response signals, leading to weak response signal reception and complexity in synchronizing transmission and reception times across different manufacturers' devices.
Innovation Solution
The system employs a backscattering type RFID communication system with RFID readers and tags that utilize visible ray transmission for query signals and RF carrier waves for response signals, incorporating a reader controller, visible ray transmitting unit, reader transmitter, and receiver to manage frequency channels efficiently, allowing for interference-free communication by using listen before transmit (LBT) and phase-difference signal removal, and enabling compatibility across different manufacturers' devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of RFID readers is increased beyond the number of frequency channels, then the coverage and capacity of the RFID system is improved, but signal interference occurs between readers transmitting on the same frequency channel
Solution Approach 1:
The patent implements dynamic frequency selection where readers can switch between frequency channels based on real-time channel availability. Instead of fixed frequency assignment, readers dynamically select from multiple frequency channels (e.g., 902-928 MHz band with multiple sub-channels) to avoid interference, allowing the system to adapt to changing traffic conditions and maintain high capacity without signal collision.
Solution Approach 2:
The patent divides the available frequency band into multiple frequency channels (segmentation of frequency resource). By splitting the 902-928 MHz band into several narrower channels, the system allows multiple readers to operate simultaneously on different channels, effectively increasing system capacity while preventing interference through frequency division.
2Speed
If query signals are transmitted frequently to improve communication speed, then the response time is reduced, but the probability of signal overlap between readers increases
Solution Approach 1:
The patent implements a listen-before-transmit (LBT) mechanism where readers perform preliminary channel assessment before transmitting query signals. By checking channel availability in advance and selecting clear frequency channels, the system maintains high communication speed through frequent transmissions while preventing signal overlap and ensuring reliable reception.
Solution Approach 2:
The patent employs periodic frequency channel switching and assessment. Readers periodically evaluate channel conditions and switch between frequency channels in a structured manner, allowing frequent query transmissions while maintaining reliability through systematic interference avoidance.
3Reliability
If synchronization mechanisms are implemented to coordinate transmission and reception times, then signal interference is reduced, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent implements self-organizing frequency selection where each reader independently assesses channel conditions and autonomously selects appropriate frequency channels without centralized coordination. This self-service approach maintains communication reliability through distributed intelligence while avoiding the complexity of synchronization mechanisms and time coordination protocols.
Solution Approach 2:
The patent uses dynamic, decentralized frequency selection where readers adaptively choose frequency channels based on real-time conditions rather than following rigid synchronization schedules. This dynamic approach achieves reliability through flexibility while minimizing device complexity by eliminating synchronization infrastructure.
4Productivity
If response signals are transmitted at the same frequency as carrier waves (in-channel backscattering), then communication efficiency is improved, but signal detection becomes difficult due to weak response intensity
Solution Approach 1:
The patent transitions from in-channel backscattering to out-of-channel backscattering, where response signals are transmitted on frequency channels different from the carrier wave frequency. This dimensional shift in frequency space separates the weak response signals from the strong carrier waves, enabling accurate detection while maintaining communication efficiency through frequency-division separation.
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 ensures error-free and efficient RFID communications without interference, simplifies device manufacturing, and improves compatibility by allowing asynchronous transmission and reception times, effectively handling overcrowded environments and enabling easy visual identification of communicating tags.
Implementation Method 1
a backscattering type RFID communication system in which an RFID tag transmits a signal back to an RE reader by using energy of a carrier wave transmitted by the RFID reader
Data Source
AI summary
A backscattering type radio frequency identification (RFID) communication system, and more particularly, a backscattering type RFID communication system in which an RFID tag transmits a signal back to an RF reader by using energy of a carrier wave transmitted by the RFID reader. Provided is a backscattering type radio frequency identification (RFID) communication system RFID communications are performed efficiently without an error while interference between RFID readers does not occur even under an overcrowded reader environment. Interference of RF signals between the RFID readers does not occur, and RFID communications can be efficiently performed even under the overcrowded reader environment. Transmitting and receiving time steps of the RFID readers do not need to be synchronized with one another so that compatibility of the RFID readers can be improved.