Abstract
Radio frequency identification (RFID) technology facilitates a myriad of applications. In such applications, an efficient reader–tag interrogation process is crucial. Nevertheless, throughout reader–tag communication, significant amounts of time and power are consumed on inescapable simultaneous tag replies (i.e., collisions) due to the lack of carrier sensing at the tags. This paper proposes the modulation cutoff intervals (MCI) process as a novel reader–tag interaction given the lack of carrier sensing constraints in passive RFID tags. MCI is facilitated through a simple digital baseband modulation termination (DBMT) circuit at the tag. DBMT detects the continuous-wave cutoff by the reader. In addition, DBMT provides different flags based on the duration of the continuous-wave cutoff. Given this capability at the tag, the reader cuts off its continuous-wave transmission for predefined intervals to indicate different commands to the interrogated tag(s). The MCI process is applied to tag interrogation (or anti-collision) and tag-counting protocols. The MCI process effect was evaluated by the two protocols under high and low tag populations. The performance of such protocols was significantly enhanced with precise synchronization within time slots with more than 50% and more than 55.6% enhancement on time and power performance of anti-collision and counting protocols, respectively. Through the MCI process, fast and power-efficient tag identification is achieved in inventory systems with low and high tag mobility; alternatively, in addition to the rapid and power efficient interaction with tags, anonymous tag counting is conducted by the proposed process.
Highlights
Passive radio frequency identification (RFID) technology is the backbone of many applications that require cost-effective and prompt detection/identification of tagged objects [1,2,3,4]
The modulation cutoff intervals (MCI) process depends on the digital baseband modulation termination (DBMT) circuit to interpret different continuous wave (CW) cutoff intervals from the reader as commands
The DBMT circuit is placed within the logic and memory module of the tag to provide a prompt and accurate reaction to the reader CW cutoff
Summary
Passive radio frequency identification (RFID) technology is the backbone of many applications that require cost-effective and prompt detection/identification of tagged objects [1,2,3,4]. Reader(s) emits an RF signal to the power and communicate with one or more tags. The impedance of the tag’s antenna is modified to return, absorb, or shift the phase of the reader’s signal. On the other side, the reader interprets the reflected, absorbed, or phase-shifted signals from the tag into a stream of binary bits [9]. Due to the simplicity of passive RFID tags, reader–tag communication is designed based on time division multiple access techniques [9,14,15]. In TDMA, tags send/receive their data within specific periods (or slots) These slots are initiated by the reader, which sends given data (a command) followed by CW transmission. The tags decode the command and reply by changing their antenna impedance to backscatter the reader’s CW. Addressing two or more tags will cause interference at the reader (collision slots); on the other hand, addressing no tag will no replies (empty slots)
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