Chapter 11 - Reducing Interference in RFID Reader Networks

Figure 11.1 Basic RFID operation Tag RFID data processing subsystem Reader Backscatter signal Antenna High power CW Network

Figure 11.2 Reader-to-tag collision Interrogation region R1’s read range R2’s read range Tag R1 R3 R3’s read range

Figure 11.3 (a) Reader-to-reader collision R1 read range R2 read range Reader Tag R2’s interference range R2 T1 T2 T3 T4 R1‘s interference range

Figure 11.3 (b) Reader-to-reader collision R1 read range R2 read range Reader Tag R2’s interference range R2 Figure 11.3 (b). Reader-to-reader collision. T1 T2 T3 T4

Table 11.1 The ISO 18000 standards for RFID Frequencies Spectrum ISO/IEC 18000-2:2004 Below 135 kHz Low frequency ISO/IEC 18000-3:2008 At 13.56 MHz High frequency ISO/IEC 18000-4:2008 At 2.45 GHz Microwave ISO/IEC 18000-6:2004 At 860 MHz to 960 MHz UHF ISO/IEC 18000-7:2008 433 MHz

Figure 11.4 RFID reader anti-collision algorithms Scheduling based approaches Control mechanism based approaches Coverage based approaches Central cooperator based approaches Other approaches TDMA based anti- collision algorithms DCS Colorwave AC-MRFID HiQ learning Pulse DiCa McMAC Clustering based Transmission Power control based

Figure 11.5 Frame structure of TDMA based anti-collision algorithm …. Tn F1 F2 Reader to reader communication period. Reader to Tag communication period. Tn-1

Figure 11.6 DCS Pseudocode DCS Subroutine If experienced collision current color == random(maxcolors) broadcast kick with new color If kick packet received with current color select different color ramdomly within maxcolors

Figure 11.7 An illustration of AC-MRFID protocol R1’s interference range (ri1) R1’s read range (rr1) R1 R2 T1 T2 T3

Figure 11.8 Hierarchical structure of Q-learning Root Q-server Q-server R-server R1 R2 R4 R5 R3 R6 R7 R8 Frequency and Timeslot allocation Collision Information R9 R10 R11 R12 R13 Rn1 Rn2 Rn4 Rn5 Rn3 Rn6 Rn7 Rn8 ……

Figure 11.9 MCMAC working principle Reset Tmin -Lost this cycle Listening in CCN -CM NOT received (for Tmin) -CN is free -Enter in contention phase -CM received -Check for free CN -Occupy the DCN -Broadcast CM -Finished reading -Continue cycle -Send control packet (every slot interval) CN: Channel CCN: Control Channel DCN: Data Channel Tmin: Minimum Listening Time CM: Control Message No Yes

Figure 11.10 CC-RFID system architecture CC Receiver Module 1 CC Relay Module CC Sender Module 1 CC Sender Module 2 CC Storage Module CC Receiver Module 2 T R2 R4 R10 Central Cooperator device modules

Figure 11.11 Two working schemes of CC-RFID CC Schedule & Multiplexing Feedback from Tag To Tag From Reader Inverse Multiplexing Send to Each Reader CC-RFID scheme one. CC Timer CC Feedback Query to Tag CC-RFID scheme two (Updating process). CC Module Tags Readers CC Search CC-RFID scheme two (Reading communication).

Table 11.2 Comparison of reader anti-collision algorithms Function used Carrier sensing Major Overhead Distributed Control Fixed Channel Assignment (FCA) Dynamic Channel Assignment (DCA) Tag side consideration for collision avoidance Colorwave Color number  Time synchronization  AC-MRFID HiQ Learning Cost function Management overhead Pulse Beacon frame Energy consumption and additional channel resource DiCa Energy aware Additional channel resource and time MCMAC LBT Additional channel resource and computational overhead CC-RFID MP2P Special hardware ACHA Probability based channel hopping Multiple channel resources

Table 11.3 Comparison in terms of channel assignment Criterion  Algorithm  Multi Chann el Multi- data Channel Dedicated Control Channel Requiremen ts Indispensabl e Initiative Optimization Technique MCMAC Yes LBT in multi channel Multiple data channel assignment ACHA LBT & channel hopping Multiple data channel hopping Pulse No Beaconing in control channel Control signaling DiCa Handshakin g Improved control channel range

Figure 11.12 Throughput comparison