Chap. 1 The basics- Sound, Electrical, Signal, Electromagnetic...

MultiMulti--Reader/MultiReader/Multi--Tag AntiTag Anti--CollisionCollision

KRNET 2006KRNET 2006

COEX, Seoul

June 27, 2006June 27, 2006

JaeJae--Hyun KimHyun Kim(([email protected]@ajou.ac.kr))

WWireless ireless IInformation nformation aaNNdd NNetwork etwork EEngineering ngineering RResearch Lab. esearch Lab. School of Electrical Engineering School of Electrical Engineering

AjouAjou University, KoreaUniversity, Korea

2Jae-Hyun Kim KRNET 2006

ContentsContents

RFID system basicsInterference in an RFID system

TagTag--toto--tag interference tag interference ReaderReader--toto--tag interferencetag interferenceReaderReader--toto--reader interferencereader interference

Anti-collision algorithms in a passive RFID systemMultiMulti--tag antitag anti--collision algorithmscollision algorithms

AutoID Class 0/1ISO 18000-6 Type A/BEPCglobal Class 1 Gen 2

MultiMulti--reader antireader anti--collision algorithmscollision algorithmsFDMA – EPCglobalLBT(CSMA) - ETSI EN 302 208 standardColorwave

ConclusionReference


RFID system basics


What is an RFID System?What is an RFID System?

RFID (Radio Frequency IDentification) system [1],[2]

A simple form of wireless sensor network to identify physical A simple form of wireless sensor network to identify physical objects (tags) in wireless environmentobjects (tags) in wireless environment

RFID applications [1],[2]

Logistics and Inventory ControlLogistics and Inventory ControlTransportation and Electronic CashTransportation and Electronic CashPatient Management in hospitalPatient Management in hospitalCloth Management and so onCloth Management and so on Hospital

Casino: i-coin

Cloth

Secret Document Pet, Cow ID, Credit card


Interference in an RFID system


Interference in an RFID SystemInterference in an RFID System

Tag-to-tag interference [3], [4]

Occur when multiple tags respond to the same reader simultaneousOccur when multiple tags respond to the same reader simultaneouslylyCan be avoided only by having each tag respond at different timesNeed to the multi-tag anti-collision algorithm to resolve this interference.

Tag-to-tag interference



Reader-to-tag interference [3], [4]

Occurs when a tag is in the interrogation zone of multiple readeOccurs when a tag is in the interrogation zone of multiple readers and more rs and more than one reader transmits simultaneously.than one reader transmits simultaneously.

Can be avoided only by having neighboring readers operate at different times or different frequencies.Need to the multi-reader anti-collision algorithm to resolve this interference.

T1T2

T3

R1 Read Range

R1

R2 Read Range

Reader

Tag

Reader-to-tag interference



Reader-to-reader interference [3], [4]

Occurs when the signal from neighboring readers interfereOccurs when the signal from neighboring readers interfereCan be avoided only by having neighboring readers operate at different times or different frequency.Need to the multi-reader anti-collision algorithm to resolve this interference.

R1 R2

T1

R2 Read Range

R2 Interference Range

ReaderTag

R1 Read Range

T2

Reader-to-reader interference


Anti-collision algorithm in Standards


MultiMulti--tag Antitag Anti--collision Algorithms collision Algorithms in Standardsin Standards

Arbitration Air Interface(R->T / T->R)

EPC Data rate(R->T / T->R)

ISO 18000-6TYPE A

Framed Slotted

Pulse interval ASK / FM0

notdefined

33 kbps /40 kbps

None

ISO 18000-6TYPE B

Probabilistic Binary tree

Manchester-ASK / FM0

notdefined

8/40 kbps /40 kbps

None

40/80 kbps /40/80 kbps

AutoID Class 1

Binary treeusing 8 bin slots

Pulse Width Mod. / Pulse Interval AM 64/96b

70.18 kbps/140.35 kbps

8-bit kill

EPCglobal Gen 2

ProbabilisticSlotted

Pulse interval ASK /Miller, FM0

96/496b40 kbps /640 kbps

32-bit kill,Access

Security

Pulse Width Mod./FSK

64/96bAutoID Class 0

Bit-by-bit Binary Tree

24-bit kill


Multi-tag Anti-collision Algorithms


MultiMulti--tag Antitag Anti--collision Algorithmscollision Algorithms

Bit-by-bit Binary TreeAutoID Class 0AutoID Class 0

Binary Tree using Bin SlotAutoID Class 1AutoID Class 1

Framed Slotted ALOHAISO 18000ISO 18000--6 TYPE A6 TYPE A

Deterministic Binary TreeISO 18000ISO 18000--6 TYPE B6 TYPE B

Probabilistic Slotted ALOHAEPCglobal Gen 2 protocolEPCglobal Gen 2 protocolISO 18000ISO 18000--6 Type C6 Type C


AutoID Class 0


AutoID Class 0 Features (UHF)AutoID Class 0 Features (UHF)

Operating frequency range860860--960 MHz960 MHz

Air interface RR-->T : AM pulse width modulation>T : AM pulse width modulationTT-->R : Passive Backscatter : FSK>R : Passive Backscatter : FSK

Data rate (North America)RR-->T : 40/80 kbps>T : 40/80 kbpsTT-->R : 40/80 kbps>R : 40/80 kbps

Collision arbitrationBitBit--byby--bit binary treebit binary tree

Security2424--bit killbit kill

Tag read speed1000 tags/sec1000 tags/sec


BitBit--byby--bit Binary Treebit Binary Tree

Basic operation [5]

After initializing, all tags send 1 bit information out of theirAfter initializing, all tags send 1 bit information out of their ID(MSB ID(MSB first)first)If there is no collision, a reader transfers the same bit informIf there is no collision, a reader transfers the same bit information ation received from the tag.received from the tag.If the collision occurs (a reader received both 0 and 1 bit infoIf the collision occurs (a reader received both 0 and 1 bit information), a rmation), a reader selects one out of two groups ( 0 or 1) based on the critreader selects one out of two groups ( 0 or 1) based on the criteria.eria.Assuming that a reader selected the group having transferred 0 bAssuming that a reader selected the group having transferred 0 bit it information, a reader transfers the 0 bit information to the taginformation, a reader transfers the 0 bit information to the tag..In previous step, the tags having transferred 0 bit information In previous step, the tags having transferred 0 bit information send next send next one bit information.one bit information.The tags having transferred 1 bit information go to the inactivaThe tags having transferred 1 bit information go to the inactivation state tion state where the tags do not respond next readerwhere the tags do not respond next reader’’s request temporarily.s request temporarily.


BitBit--byby--bit Binary Treebit Binary Tree

Basic operation [5]

REPLY

TAG

X(0)

READER

REPLY

TAG READERTAGREADERTAGREADERREADER

TAG3(100)

TAG2(011)

TAG1(001)

STATE

X(0)REPLYCMDREPLYX(0)CMD

0

0

X

0

1

1

0

X 001 X

1 1


Tag State Transition DiagramTag State Transition Diagram


AutoID Class 1


AutoID Class 1 Features (UHF)AutoID Class 1 Features (UHF)

Operating frequency range :860860--960 MHz960 MHz

Air interface RR-->T : AM pulse width modulation>T : AM pulse width modulationTT-->R : Passive Backscatter : Pulse interval AM>R : Passive Backscatter : Pulse interval AM

Data rate (North America)RR-->T : 70.18 kbps>T : 70.18 kbpsTT-->R : 140.35 kbps>R : 140.35 kbps

Collision arbitrationBinary Tree using 8 BinBinary Tree using 8 Bin--slotslot

Security88--bit killbit kill

Tag read speedNot specifiedNot specified


Binary Tree using 8 BinBinary Tree using 8 Bin--slotslot

Basic operation [6]

After initialization, the reader sends After initialization, the reader sends PingIDPingID commandcommandThe tags matching [VALUE] beginning at location [PTR] reply by The tags matching [VALUE] beginning at location [PTR] reply by sending 8 bits of the tag identifier beginning with the bit at lsending 8 bits of the tag identifier beginning with the bit at location [PTR] ocation [PTR] + [LEN]+ [LEN]The 8The 8--bit reply is communicated during one of eight Bin slots delineatbit reply is communicated during one of eight Bin slots delineated ed by the reader. by the reader.

The tags whose 3 MSBs of ID after [VALUE] field is ‘000’ choose Bin 0 and whose 3 MSBs of ID after [VALUE] field is ‘111’ choose Bin 7.

The reader sequentially processes Bin slots from Bin 0 to Bin 7.The reader sequentially processes Bin slots from Bin 0 to Bin 7.When two or more tags choose the same Bin slot, the reader retraWhen two or more tags choose the same Bin slot, the reader retransmits nsmits PingID command to the tags. PingID command to the tags.

In which case, [LEN]=[LEN]+3If only one tag chooses one Bin slot, the reader sends If only one tag chooses one Bin slot, the reader sends ScrollIDScrollID command command to identify the tag. to identify the tag.

The tags matching [VALUE] beginning at location [PTR] reply by sending their all ID. In this case only one tag sends its full ID to the reader



Basic operation [6]

Can select specific tags for identificationCan select specific tags for identificationUse 8 bin slots (3 bit info.) to singulate the tagsUse 8 bin slots (3 bit info.) to singulate the tags

Reader TAG

COMMANDPOINTER

VALUE

REQ.

STATUS

TAG 1

TAG 2

Bin 0(000)

Bin 1(001)

Bin2(010)

Bin 3(011)

Bin 4(100)

Bin 5(101)

Bin 6(110)

Bin 7(111)LENGTH

TAG 3

PingID0000 00000000 0100

1010

(1010001110101010)

(1010010101001010)

(1010010010011010)

00111010

01010100

0100100101001101

10100101

(1010001110101010)

(1010010101001010)

(1010010010011010)

IDLE IDLE SUCC IDLE IDLE SUCC IDLE IDLE

PingID0000 00000000 01111010010

IDLE SUCC COLL IDLE IDLE IDLE IDLE IDLE

(1010001110101010)

(1010010101001010)

(1010010010011010)

TAG 1 sends ITM ( Full ID )(1010001110101010)

(1010010101001010)

(1010010010011010)

ScrollID0000 00000000 01111010001

(1010001110101010)

(1010010101001010)

(1010010010011010)



0 0 0[LEN] = 1

Bin000

Bin111

Bin110

Bin101

Bin100

Bin011

Bin010

Bin001

0 0

00 0 0[LEN] = 4 0 0

………………

………………

0 1 1 0 0 1 1 1Tag_1 1 0 0 0 0

0 1 1 1 0 1 0 1Tag_2 1 1 0 0 0

0

1 1

PingID [LEN]=1,[VALUE]=0

ScrollID [LEN]=7,[VALUE]=0011001

PingID [LEN]=4,[VALUE]=0011

………………0 1 1 1 0 1 1 1Tag_3 0 1 0 0 0

0

0

0

01

00 0 0[LEN] = 4 0 0 1 1PingID [LEN]=7,[VALUE]=0011101



Basic operation [6]


Proposed AntiProposed Anti--collision Algorithmcollision Algorithm

Fast Anti-collision Algorithm in EPC Class 1 UHF [7]

Ajou Univ. proposedAjou Univ. proposedEnhance the performance of the algorithm defined in AutoID ClassEnhance the performance of the algorithm defined in AutoID Class 11Basic concept of the proposed algorithmsBasic concept of the proposed algorithms

By using Sequence information of whole ID obtained from the tag By using ScrollAllID command Reduce the number of PingID commands

By using a proposed tree-search algorithmReduce the number of unnecessary procedures

0 0 1 0 0 1 …… X 0 X X 0

(N-1) bits

X

PingID ( [PTR]=N-1, [LEN]=1,[VALUE]=0)

……0

0 1 0 1 0 1 0 1

0 1 0

0

0

1

1


Proposed antiProposed anti--collision algorithmcollision algorithm

Number of Ping ID commands ( )Conventional algorithmConventional algorithm

Proposed algorithmProposed algorithm

17

2 0 0

1 1 11k k k

L L Lm r r r

total kL k n

r n r n L r nI mr r n r n r nr

−∞

= = =

⎛ ⎞− − − − −⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟= + − − ⋅⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎜ ⎟− − −⎝ ⎠ ⎝ ⎠ ⎝ ⎠⎝ ⎠

∑∑∑

1k

mr

>where,

totalI

1 1 1

0 10 1

1 1 11k km m

r rkto ta l k k

k k

r m rI I I rr r rr

− −−∞ ∞

−= =

⎛ ⎞− −⎛ ⎞ ⎛ ⎞⎜ ⎟= = + × − − ⋅⎜ ⎟ ⎜ ⎟⎜ ⎟⎝ ⎠ ⎝ ⎠⎝ ⎠

∑ ∑

1 1k

mr − > , I0 = 1 (Number of first reader command)where,


Simulation and analysis result (1/4)Simulation and analysis result (1/4)

Number of PingID command vs. Number of used tagsRandom tag IDRandom tag ID

20 40 60 80 100 120 140 160 180 2000

100

200

300

400

500

600

The number of used tags

The

num

ber

of P

ingI

D c

omm

and

Conventional EPC CLASS 1(analysis)Conventional EPC CLASS 1(simulation)Proposed algorithm(analysis)Proposed algorithm(simulation)Proposed algorithm using ScrollAllID(analysis)Proposed algorithm using ScrollAllID(simulation)



Tag identification time vs. Number of used tagsRandom tag IDRandom tag ID

20 40 60 80 100 120 140 160 180 2000

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2


Tag

iden

tific

atio

n tim

e(se

c)

Conventional EPC CLASS 1(analysis)Conventional EPC CLASS 1(simulation)Proposed algorithm(analysis)Proposed algorithm(simulation)Proposed algorithm using ScrollAllID(analysis)Proposed algorithm using ScrollAllID(simulation)

태그의개수가 200개일때최대 130%성능향상



Number of PingID command vs. Number of used tagsSequential tag IDSequential tag ID

20 40 60 80 100 120 140 160 180 2000

500

1000

1500

2000

2500


The

num

ber

of P

ingI

D c

omm

and

Conventional EPC CLASS 1Proposed algorithmProposed algorithm using ScrollAllID

20 40 60 80 100 120 140 160 180 2005

10

15

20

25

30

35

40

45

50



Tag identification time vs. Number of used tagsSequential tag IDSequential tag ID

20 40 60 80 100 120 140 160 180 2000

1

2

3

4

5

6


Tag

iden

tific

atio

n tim

e(se

c)

Conventional EPC CLASS 1Proposed algorithmProposed algorithm using ScrollAllID

100 120 140 160 180 2000.35

0.4

0.45

0.5

0.55

0.6

0.65

0.7

0.75태그의개수가 200개일때최대 146%성능향상


ISO 18000-6 TYPE A


ISO 18000ISO 18000--6 Type A Features (UHF)6 Type A Features (UHF)

Operating frequency range860860--960 MHz960 MHz

Air interfaceRR-->T : Pulse interval ASK>T : Pulse interval ASKTT-->R : Passive backscatter : Bi>R : Passive backscatter : Bi--phase Space AMphase Space AM

Data rate (North America)RR-->T : 33kbps>T : 33kbpsTT-->R : 40kbps>R : 40kbps

Collision arbitrationFramed slotted ALOHAFramed slotted ALOHA

SecurityNoneNone

Tag read speed100 tags/sec100 tags/sec


Framed Slotted ALOHAFramed Slotted ALOHA

Basic operation [8]

After the reader has sent After the reader has sent InitInit--roundround command to the tags, it waits command to the tags, it waits for a certain amount of time for their answers.for a certain amount of time for their answers.Tags receiving an Tags receiving an Init_roundInit_round command randomly select a slot in command randomly select a slot in which to respond.which to respond.After the reader has sent the After the reader has sent the Init_roundInit_round command, there are three command, there are three possible outcomes:possible outcomes:

The reader does not receive a response because either no tag has selected slot one or the reader has not detected a tag response. It then issues a Close _slot command because it has not received a response.

The tags receiving the Close_slot command increase their slot counter by oneIf the reader detects a collision between two or more tag responses, it sends a Close_slot command.

The tags receiving the Close_slot command increase their slot counter by one


Framed Slotted ALOHAFramed Slotted ALOHA

Basic operation [8]

If the reader receives a tag response without error, it sends a Next_slot command containing the signature of the tag just received.

When a tag that has transmitted its data in the current slot receives a Next_slot command, it :

Verifies that the signature in the command matches the signature it sent in its last response, andVerifies that the Next_slot command has been received within the defined time

If the tag has met these acknowledge conditions, it enters the Quiet state. Otherwise, it retains its current state.


Probabilistic Slotted ALOHAProbabilistic Slotted ALOHA

Basic operation [8]

TAG4(0101)

TAG3(0011)

TAG2(1010)

TAG1(1011)

STATE

2nd REQSlot4Slot3Slot2Slot11st REQREADER

Frame size = 4

IDLE1011 COLL 0101

0011

1010

1011

0101

0011

1010

Frame size = ?

Need to vary the Frame size for the number of tags


Tag state transition diagramTag state transition diagram



Dynamic Framed Slotted ALOHA [9],[10]

Ajou Univ. proposedAjou Univ. proposedEnhance the performance of the algorithm defined in ISO 18000Enhance the performance of the algorithm defined in ISO 18000--6 6 Type AType A

The problems of ISO 18000-6 type A protocolPerformance will be degraded when :

The number of tags are either (even) more or less than the frame size.Need to dynamically vary the frame size for the number of tags.

No detailed methods in StandardsHow to estimate the number of tagsHow to dynamically allocate according to the number of estimated tags.

Basic concept of the proposed algorithmsBasic concept of the proposed algorithmsPropose Tag Estimation method (TE)

Estimate the number of tags around the readerPropose Dynamic Slot Allocation method (DSA)

Dynamically allocate the optimal frame size according to the number of estimated tags



Tag EstimationCollision RatioCollision Ratio

Ratio of the number of collided slots to the frame size

11 1 1 .

1

Number of collided slotsFrame size

n

ration

CL L

= = − − +−

⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠


0 100 200 300 400 500 600 700 800 900 10000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Number of tags

Col

lisio

n R

atio

L=8L=16

L=32

L=64

L=128

L=192

L=256

L=320

L=512

L=640


Tag EstimationCollision RatioCollision Ratio

- An example -

Frame size = 320 slots

Collision Ratio =0.46

Estimated number of tags = 400



Dynamic Slot AllocationUse the throughput Use the throughput SS of the system to get the optimal frame size of the system to get the optimal frame size LL

Determine the frame size by selecting the value Determine the frame size by selecting the value L L when when SS is is maximummaximum

Optimal Frame SizeOptimal Frame Size ( )( )

optimalL n=

optimalL

succ

succ coll idle

succP

S PP P P

= =+ +

1 2(1 ) ( 1) (1 ) 0n ndSn p n n p p

dp− −= − − − − =


Simulation results(2)Simulation results(2)

Identification time vs. number of tagsIdentification timeIdentification time means the time taken until all tags are means the time taken until all tags are identified.identified.

100 200 300 400 500 600 700 800 900 10000

0.5

1

1.5

2

2.5

3

Number of tags

Iden

tific

atio

n tim

e(se

c)

Slot-64Slot-128Slot-256Vogt-min

100 200 300 400 500 600 700 800 900 10000.1

0.2

0.4

0.6

0.8

1

1.2

1.4

Number of slots

Iden

tific

atio

n tim

e(se

c)

Vogt-minVogt-estDFSA

Algorithms not estimating the number of tags Algorithms estimating the number of tags


ISO 18000-6 TYPE B


ISO 18000ISO 18000--6 Type B Features (UHF)6 Type B Features (UHF)

Operating frequency range :860860--960 MHz960 MHz

Air interfaceRR-->T : Manchester ASK>T : Manchester ASKTT-->R : Passive Backscatter : Bi>R : Passive Backscatter : Bi--phase Space AMphase Space AM

Data rate (North America)RR-->T : 10 or 40 kbps>T : 10 or 40 kbpsTT-->R : 40 kbps>R : 40 kbps

Collision arbitrationDeterministic Binary TreeDeterministic Binary Tree

SecurityNoneNone

Tag read speed 100 tags/sec100 tags/sec

Flexible selection maskingSelect specific tags for identificationSelect specific tags for identification


Deterministic Binary TreeDeterministic Binary Tree

Basic operation [8],[11]

Use internal 8Use internal 8--bit counter and a random generator to singulate tagsbit counter and a random generator to singulate tagsIn the beginning, a group of tags are moved to the ID state by In the beginning, a group of tags are moved to the ID state by GROUP_SELECT command and shall set their internal counters to 0.GROUP_SELECT command and shall set their internal counters to 0.

1. All tags in the ID state with the counter COUNT at 0 shall transmit their ID.2. If more than one tag transmitted their ID, the reader receives an erroneous response.

The FAIL command shall be sent.3. All tags receiving a FAIL command with COUNT not equal to 0 shall increment COUNT.

All tags receiving FAIL command with a count of 0 shall generate a random number. Those that roll a 1 shall increment COUNT and shall not transmit. Those that roll a zero shall keep COUNT at zero and shall send their UID again.

One of four possibilities now occurs :One of four possibilities now occurs :4. If more than one tag transmits, the FAIL step 2 repeats.5. If all tags roll a 1, none transmits. The reader receives nothing. It sends the SUCCESS command. All the counters decrement, and the tags with a count of o transmit.6. If only one tag transmits without error, the ID is received correctly.7. If only one tag has a count of 1 and transmits, step 5 or 6 repeats. If more than one tag transmits, step 2 repeats.


Deterministic Binary TreeDeterministic Binary Tree

1 2 3 4 5 6 7 98 10 11 12Iterations

0

T1 T2

T3

T4

0 0

0

1 1 1 1

1

Coll Succ IdleColl Coll Coll Coll IdleSucc Succ Succ

Basic operation [11]


Tag state transition diagramTag state transition diagram


0 200 400 600 800 10000

500

1000

1500

2000

2500

3000

Number of tags

Num

ber

of s

lots

nee

ded

ISO 18000ISO 18000--6 TYPE B6 TYPE B

Performance AnalysisTo identify To identify nn tags, 2.886tags, 2.886nn--1 slots are needed.1 slots are needed.For more details, refer to For more details, refer to [11][11]


EPCglobal Gen 2


EPC Gen2 FeaturesEPC Gen2 Features

Operating frequency860 860 –– 960 MHz960 MHz

Air interfaceRR-->T : PIE ASK>T : PIE ASKTT-->R : FM0 or Miller>R : FM0 or Miller--modulated submodulated sub--carriercarrier

Data rate (North America)RR-->T : 26.7 to 128 kbps>T : 26.7 to 128 kbpsTT-->R : 40 to 640 kbps>R : 40 to 640 kbps

Collision arbitrationProbabilistic slottedProbabilistic slotted

Access control and privacy3232--bit kill and access passwordsbit kill and access passwords

Operating Channels50 channels supported for dense50 channels supported for dense--Interrogator operation.Interrogator operation.


EPC Gen2 Features (EPC Gen2 Features (concon’’tt))

Flexible logical layer1616--bit to 496bit to 496--bit electronic product code (EPC)bit electronic product code (EPC)Optional passwordOptional password--protected access controlprotected access controlOptional user memoryOptional user memory

Reliable operationProbabilistic slotted antiProbabilistic slotted anti--collisioncollisionAdapt to rapidly changing tag populationsAdapt to rapidly changing tag populations

Q-Selection algorithmFlexible selection masking

Can select specific tags for identificationCan select specific tags for identification4 sessions supported


Probabilistic SlottedProbabilistic Slotted


Reader issues a Reader issues a QueryQuery command with a parameter command with a parameter QQStarting the inventory round which is defined as the period between successive Query commands)

Tag loads a Tag loads a QQ--bit random value into its slot counterbit random value into its slot counterRandom number = RAND(0, 2Q-1)If a tag loads a zero, it backscatters an RN16

Reader acknowledges the tag by returning the Reader acknowledges the tag by returning the RN16RN16Acknowledged tag backscatters its Acknowledged tag backscatters its EPCEPCReader issues a Reader issues a QueryRepQueryRep commandcommand

The tag inverts its inventoried flag and leaves the roundAll other tags decrement their slot countersIf any tag decrements to zero, it replies with an RN16



Reader

Command

Session S.C.

Target I.F.

Q S

Act

n.a.

QueryRep

n.a.

0

Select

n.a.

000 A A

S0

S0 S0

Query

A

2

2

Send RN16WaitSend RN16.

Tag1 Tag2

B

ACK

10

QueryRep

n.a.

n.a.

Send EPC (ID)

S0

n.a.

n.a.

S0

n.a.

n.a.


where, S.C. : Slot Counter, I.F. : Inventoried Flag, S : Session, Act. : Action



Basic operationReader Tag

Query (Q)

All tags choose SC ( = rand (0, 2^Q-1))Two possible outcomes :

1) SC=0 : Tag sends RN16

Idle slot

QueryRep

All tags decrease SC (SC=SC-1)Two possible outcomes :


2) SC<>0 : No replySuccessful slot

My RN16 = rcvd RN16 ?Two possible outcomes :

1) Matching : Tag sends EPC

2) Not matching : No reply

ACK(RN16)

QueryRep

Save EPC

All tags decrease SC (SC=SC-1)

One tag’s response

EPC

No response

2) SC<>0 : No reply



Basic operationReader Tag

Query (Q)

All tags choose SC ( = rand (0, 2^Q-1))Two possible outcomes :


Collided slot

Case 1 : QueryRep

All tags decrease SC (SC=SC-1)Two possible outcomes :


2) SC<>0 : No reply

Tags select their new slot counterTwo possible outcomes :


2) SC<>0 : No reply

Case 2 : QueryAdjust(UpDn)

# of responses > 1

2) SC<>0 : No reply

Continue a process



Ready

Arbitrate

Reply

Acknowledged

Power-up and ~killed

CMD : SelectAction : Return to readyReply : None.

CMD : QueryAuction : New roundReply : None

CMD : All otherAction : Remain in ready Reply : None

CMD : SelectAction : Return to readyReply : None.

CMD : QueryAuction : New roundReply : None

CMD : All otherAction : Remain in arbitrate Reply : None

CMD:None within time T2Action : Return to arbitrateReply : None.

NEW ROUNDCMD : Query[mismatched

inventoried or SL flags]Reply : None

NEW ROUNDCMD : Query[slot>0 & matching

(inventoried or SL) flags]Reply : None

NEW ROUNDCMD : Query[slot=0 & matching

(inventoried or SL) flags]Reply : New RN16

CMD : QueryRep, QueryAdjust[slot<>0]Reply : None

CMD : QueryAdjust, QueryRep [slot=0]Reply : New RN16

CMD : QueryAdjust[slot=0]Reply : New RN16

CMD : ACK[valid RN16]Reply : PC, EPC, CRC-16CMD : Req_RN[invalid RN16]Reply : None

CMD : ACK[valid RN16]Reply : PC, EPC, CRC-16

SlotCounter

QueryQueryRep

QueryAdjustSlot



Qfp=4.0

Q=round(Qfp)Query(Q)

Qfp=max(0,Qfp-c)

# of tag responses

Qfp=Qfp+0 Qfp=min(Qfp+c,15)

0 > 1

1

※ Typical values for C are 0.1<c<0.5.

Q-Selection algorithm


Simulation Results(1/3)Simulation Results(1/3)

Identification time vs. number of tags

0 50 100 150 200 250 3000

100

200

300

400

500

600

Number of tags

Iden

tific

atio

n tim

e(m

s)

T1-3ST1-5ST2-3ST2-5S

- T1-3S : QueryAdjust – 3step (Q value : 1-5/6-10/11-15, c value : 0.5/0.3/0.1)

- T2-5S : QueryRep – 5step (Q value : 1-3/4-6/7-9…, c value : 0.5/0.4/0.3,…)



Identification time vs. number of tags

0 50 100 150 200 250 3000

100

200

300

400

500

600

Number of tags

Iden

tific

atio

n tim

e(m

s)

T1-F(0.1)T1-F(0.2)T1-F(0.3)T1-F(0.4)T1-F(0.5)T2-F(0.1)T2-F(0.2)T2-F(0.3)T2-F(0.4)T2-F(0.5)

- F(0,1) : Fixed 0.1 for c value



Identification time vs. number of tags (Considering BER)

0

200

400

600

800

1000

1200

20 40 60 80 100 120 140 160 180 200

N umber o f t a gs

Ide

nti

fic

ati

on

tim

e(m

s)d

d

T1_3_e0 T1_3_e2 T1_3_e3 T1_3_e4

T2_3_e0 T2_3_e2 T2_3_e3 T2_3_e4



Accuracy vs. number of tags (Considering BER)

0%

20%

40%

60%

80%

100%

120%

20 40 60 80 100 120 140 160 180 200

Nu mbe r o f t ags

Ac

cu

rac

y(%

)d

fdf

T1_3_e0 T1_3_e2 T1_3_e3 T1_3_e4

T2_3_e0 T2_3_e2 T2_3_e3 T2_3_e4



Identification rate vs. types of scenarios (Considering BER)


Multi-reader Anti-collision Algorithms


MultiMulti--reader Antireader Anti--collision Algorithmscollision Algorithms

FDMA (Frequency Division Multiple Access) [12],[13]

EPCglobal Gen 2 protocolEPCglobal Gen 2 protocolA technique to allocate the reader’s transmission with different frequenciesA reader hops within its sub-channels every 0.4 sec.

Channels for RFID (Korea)



LBT (Listen Before Talk) [14], [15]

ETSI EN 302 208 standardETSI EN 302 208 standardCSMA basedCSMA based

Sense the channel before transmission

If idle, then transmit the dataIf not idle, then sense the channel after random back-off time

IDLE

Channel busy ?N

YCommunicate to the

tags

Back-off timerExpired ?

End

Start

N

Sense the channel

Y

Run Back-off timer



TDMA (Time Division Multiple Access) [4]

Colorwave (DCS and VDCS)Colorwave (DCS and VDCS)A technique to allocate the reader’s transmission with different timeA reader varies the max_color based on the criterionDistributed protocol

Collision in Colorwave

Slots in TDMA



Colorwave [4]

A technique to optimize the graph to the smallest number of totaA technique to optimize the graph to the smallest number of total l colors required to achieve a particular percentage of successfulcolors required to achieve a particular percentage of successfultransmissions.transmissions.Two types of conceptTwo types of concept

Distributed Color Selection (DCS)If the transmission collides with another reader, the transmission request is discarded. Furthermore, the reader randomly chooses a new color and reserves this color, causing all of its neighbors to select a new color; Theoretically clearing the timeslot for the next time the reader needs to transmit.

Variable-maximum DCS (Colorwave)Each reader monitors the percentage of successful transmissionsEach reader varies the max color based on that criterion (percentage) of itself



Distributed Color Selection (DCS)DCS Subroutine 1 DCS Subroutine 1 –– TransmissionTransmission

If transmission requestedIf (timeslot_ID%max_color)==current_colorThen transmitElse idle until (timeslot_ID%max_color)==current_color

DCS DCS SburoutineSburoutine 2 2 –– CollisionCollisionIf attempted transmission but experienced collisioin

Current_color==random(max_color)Broadcast kick stating new color

DCS Subroutine 3 DCS Subroutine 3 –– Kick resolutionKick resolutionIf kick received stating current_color

Randomly change to different color within max_colors



Variable-maximum Distributed Color Selection (VDCS)Colorwave Subroutine 1 Colorwave Subroutine 1 –– Color Change Color Change

If collision percentage is past SAFE threshold ANDTime spent in current max_color exceeds min_time threshold

Change max_color up or down one (depending on threshold exceeded)Next iteration, initiate kick to new max_color

Colorwave Subroutine 2 Colorwave Subroutine 2 –– Kick ResolutionKick ResolutionIf kick received stating current_color

Change to random color within max_color OTHER THAN current colorIf kick received stating change to new max_color AND Collision percentage is past TRIGGER thresholdAND Time spent in current max_color exceeds min_time threshold

Change max_color to kicked valueNext iteration, initiate kick to new max_color

All DCS subroutines are also in use.All DCS subroutines are also in use.


ConclusionConclusion

Anti-collision algorithms in a passive RFID systemMultiMulti--tag antitag anti--collision algorithmscollision algorithms

ISO 18000-6 Type A/BAutoID Class 0/1EPCglobal Class 1 Gen 2

MultiMulti--reader antireader anti--collision algorithmscollision algorithmsFDMA or LBT

For reliable communications in a passive RFID systemMore functional tags neededMore functional tags needed

Trade off for costStronger mechanisms needed for reader and tag communicationStronger mechanisms needed for reader and tag communication

Gen 3 ?Efficient Privacy & security solutionsEfficient Privacy & security solutions


ReferencesReferences[1] S. Sarma, D. Brock, and D.Engels, "Radio frequency identification and electronic product code, " 2001 IEEE

MICRO, 2001.[2] H. Vogt, ”Efficient Object Identification with Passive RFID tags, ” In International Conference on Pervasive

Computing, Zurich, 2002, pp. 98-113.[3] S. Birari and S. Iyer,” PULSE : A MAC Protocol for RFID Networks,” USN’2005, Dec. 2005. [4] J. Waldrop, D. W. Engels, and S. E. Sarma, “Colorwave : an anti-collision algorithm for the reader collision

problem,” in IEEE International Conference on Communications, vol. 2, 2002, pp. 1206-1210.[5] Auto-ID Center, Draft Protocol Specification for a Class 0 Radio Frequency Identification tag., 2003.[6] Auto-ID Center, Draft Protocol Specification for a Class 1 Radio Frequency Identification tag., 2003.[7] H. S. Choi and J. H. Kim, "Anti-collision algorithm using Bin slot in RFID System," in Proc. IEEE TENCON

'05, Melbourne, Australia, Nov. 21-24, 2005, p.71.[8] ISO/IEC 18000-6 : 2003(E), Part 6 : Parameters for air interface communications at 860-960 MHz, Nov. 26,

2003.[9] J. R. Cha and J. H. Kim, "Dynamic Framed Slotted ALOHA Algorithm using Fast Tag Estimation method

for RFID System," in Proc. CCNC2006, Las Vegas, USA, Jan. 8-10, 2006.[10] J. R. Cha and J. H. Kim, "Novel Anti-collision Algorithms for Fast Object Identification in RFID system,"

in Proc. ICPADS2005, Fukuoka, Japan, Jul. 20-22, 2005, pp. 63-67. [11] J. L. Massey, "Collision resolution algorithms and random-access communications, " Univ. California, Los

Angeles, Tech. Rep. UCLAENG -8016, Apr. 1980.[12] EPC™, Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFID Protocol for Communications at

860 MHz – 960 MHz Version 1.0.9, Jan., 2004.[13] ISO/IEC 18000-6 : 2005(E), Part 6C : parameters for air interface communications at 860 MHz to 960 MHz,

2005.[14] ETSI EN 302 208-1 v1.1.1, Sep. 2004. CTAN:http//www.etsi.org[15] ETSI EN 302 208-2 v1.1.1, Sep. 2004. CTAN:http//www.etsi.org

Chap. 1 The basics- Sound, Electrical, Signal, Electromagnetic...

Documents

Transcript of Chap. 1 The basics- Sound, Electrical, Signal, Electromagnetic...