Chapter 11 - Reducing Interference in RFID Reader Networks

Figure 11.1 Basic RFID operation

RFIDTag

RFID data processing subsystem RFIDReader Backscatter signal

Antenna

High power CW

Network

Figure 11.2 Reader-to-tag collision

Reader

R2

T1

Interrogation region

R1’s read rangeR2’s read range

Tag

R1

R3

R3’s read range

Figure 11.3 (a) Reader-to-reader collision

R1

R1 read range

R2 read

range

ReaderTag

R2’s interference range

R2

T1

T2

T3T4

R1‘s interference range

Figure 11.3 (b) Reader-to-reader collision

R1

R1

rea

d ra

ng

e

R2 read

range

ReaderTag

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

ISO 18000 standard 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 UHF

Figure 11.4 RFID reader anti-collision algorithms

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

T1 T2…. Tn

F1

T1 T2…. Tn

F2

Reader to reader communication period. Reader to Tag communication period.

Tn-1 Tn-1

Figure 11.6 DCS Pseudocode

DCS Subroutine If experienced collisioncurrent color == random(maxcolors)

broadcast kick with new colorIf 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)

R1R2

T1T2

T3

Figure 11.8 Hierarchical structure of Q-learning

Root Q-server

Q-server

R-server R-server R-server

Q-server

R-server R-server R-server

R1R2

R4

R5

R3

R6

R7R8

Fre

qu

en

cy an

d T

ime

slot

allo

catio

n

Co

llision

Info

rma

tion

R9R10

R11R12

R13

Rn1Rn2

Rn4Rn5

Rn3

Rn6

Rn7Rn8

…… …… ……

Figure 11.9 MCMAC working principle

Reset T

min

-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: ChannelCCN: Control ChannelDCN: Data ChannelTmin: Minimum Listening Time

CM: Control Message

No

Yes

No

Yes

No

Yes

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

T

T

T

T

T

T

TT

R2

R4

R10

Central Cooperator device modules

R2

R10

Figure 11.11 Two working schemes of CC-RFID

CC Schedule & Multiplexing

Feedback from Tag

To TagFrom Reader

Inverse MultiplexingSend to Each Reader

CC-RFID scheme one.

CC TimerCC Feedback

Query to Tag

Feedback from Tag

CC-RFID scheme two (Updating process).CC Module

Tags

CC Search CC FeedbackFrom Reader

CC-RFID scheme two (Reading communication).

Table 11.2 Comparison of reader anti-collision algorithms

AlgorithmFunction used

Carrier sensing

Major OverheadDistributed Control

Fixed Channel Assignment (FCA)

Dynamic ChannelAssignment (DCA)

Tag side consideration for collision avoidance

Colorwave Color number Time synchronization

AC-MRFID

Color number Time synchronization

HiQ Learning

Cost function Management overhead

PulseBeacon frame

Energy consumption and additional channel

resource

DiCaEnergy 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

Requirements

Indispensable Initiative

Optimization Technique

MCMAC Yes Yes YesLBT in multi

channel

Multiple data channel

assignment

ACHA Yes Yes YesLBT &

channel hopping

Multiple data channel hopping

Pulse Yes No YesBeaconing in control channel

Control signaling

DiCa Yes No YesHandshakin

gImproved control channel range

Figure 11.12 Throughput comparison

0100200300400500600

Color W

ave

CSMA

HiQPuls

eDiC

a

MCM

AC

ACHA

CC-RFID

Ne

two

rk th

rou

gh

pu

t(b

yte

s/se

con

d)