giao trinh cong nghe rfid 120921121946 phpapp01

7/14/2019 Giao Trinh Cong Nghe Rfid 120921121946 Phpapp01

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I HC S PHM K THUT TP. HCM

KHOA IN-IN T

CNG NGH NHN DNG V TUYN RFID

Radio Frequency Identification

TNG HP: NGUYN VN HIP


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Chng 1GII THIU V CNG NGH RFID

I - Cng ngh RFIDCng ngh RFID(Radio Frequency Identification)cho php mt thit b c thng tin

cha trong chip khng tip xc trc tip khong cch xa, khng thc hin bt k giaotip vt l no hoc . Cng ngh ny cho ta phng phptruy .

K thut RFID s dng truyn thng khng dy trong di tn sng v tuyn truynd liu t cc tag ) n cc reader (b c). Tag c th c nh km hoc gn vo itng c nhn dng chng hn sn phm, hp hoc (pallet). Reader scan d liuca tag v gi thng tin n c s d liu c lu tr d liu ca tag. Chng hn, cc tag cth c t trn knh chn gi xe hi h thng thu ph ng c th nhanh chng nhndng v thu tin trn cc tuynng.

Dng n gin nht c s dng hin nay l h thng RFID b ng lm vic nh sau:reader truyn mt tn hiu tn s v tuyn in t qua anten ca n n mt con chip. Readernhn thng tin tr li t chip v gi n n my tnh iu khin u c v x l thng tinlyc t chip. Cc chip khng tip xc khng tch in, chng hot ng bng cch sdng nng lng nhn t tn hiu c gi bi reader.

II -Lch s RFID nh du t nhng nm 1930 nhng cng ngh RFID c ngun gc tnm 1897 khi Guglielmo Marconi pht ra radio. RFID p dng cc nguyn tc vt

l c bn nh truyn pht rad ng in t truyn v nhndng d liu khc nhau.

hiu r hn v s ging nhau ny, hnh dung mt trm radio pht ra m thanh hocm nhc qua mt b pht. D liu ny cn phi m hasang dng sng radio c tn s xcnh. Ti nhng v tr khc nhau, ngi nghe c mt my radio gii m d liu t trm

pht (m thanh hoc m nhc). Mi ngi u nhn bit c s khc nhau v cht lngsng radio khi ngi trn xe hi. Khi di chuyn cng xa b pht tn hiu thu c cng yu.Khong cch theo cc hng hoc cc vng m sng radio pht ra c th bao ph c xc

nh bi iu kin mi trng, kch thc v nng lng ca anten ti mi ng giao tip.S dng thut ng RFID, c chc nng nh mt trm truyn gi l mt transponder(tag) c to thnh t 2 thutng transmitterv responder;vt c chc nng nh radio gil reader(b c) hay interrogator.Antenxc nh phm vi c (range).

Ba thnh phn tag, reader v anten l nhng khi chnh ca mt h thng RFID. Khithay i v nng lng, kch thc, thit k anten, tn s hot ng, s lng d liu v

phn mm qun l v xut d liu to ra rt nhiu ng dng. Cng ngh RFID c th giiquyt rt nhiu bi ton kinh doanh thc t.


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a. Thi k u ca RFIDVo nhng nm 1930 c Army v Navy u gp phi nhng th thch khi xc nh

nhng mc tiu trn mt t, trn bin v trn bu tri. Vo nm 1937 phng th nghimnghin cuNaval U.Spht trin h thng xc nhFriend-or-Foe (IFF)cho php nhng itng thuc v qun ta (friend) v d my bay Allied c th phn bit vi my bay ch. Kthut ny tr nn ph bin trong h thng iu khin lu thng hng khng bt u vo cuithp nin 50. Nhng ng dng ca sng RFvo trong vic xc nh vt th trong sut thpnin 50 gii hn ch yu trong qun i, phng lab nghin cu, trong cc doanh nghip ln

bi v nhng thit b ny c gi rt cao v kch thc ln. Nhng thit b to ln v cng knhny l tin thn ca nhng h thng gi l RFID ngy nay. Hnh 2.1m thnh nh ca mtthit b IFF k bn l thit b RFID ngy nay.

Hnh 2.1 Thit b IFF (bn tri), thit b RFID (tch cc) hin i ngy nay

ng ngh mi nhng sn phm ny gn hn v gi r hn nh: cng nghtch hp trong IC, chip nh lp trnh c, vi x l, nhng phn mm ng dng hin ingy nay v nhng ngn ng lp trnh lm cho cng ngh RFID ang c xu hng chuynsang lnh vc thng mi rng ln.

Cui thp k 60 u thp k 70 nhiu cng ty nh Sensormatic and Checkpoint Systemsgii thiu nhng sn phm mi t phc tp hn v ng dng rng ri hn. Nhng cng tyny bt u pht trin thit b gim st in t (electronic article surveillance EAS) bov v kim k sn phm nh qun o trong ca hng, sch trong th vin. H thng RFIDthng mi ban n ny ch l h thng RFID tag mt bit (1-bit tag) gi r xy dng, thchin v bo hnh. Tag khng i hi ngun pin (loi th ng) d dng t vo sn phm vthit k khi ng chung cnh bo khi tag n gn b c, thng t ti li ra vo , pht

hin s c mt ca tag.


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Hnh 2.2 Cc mc quan trng trong giai on u ca RFID

b. Pht hin cc vt th ring bitSut thp k 70, cng nghip sn xut, vn chuyn bt u nghin cu v pht

trin nhngd n tm cch dng IC da trn h thng RFID. C nhiu ng dng trongcng nghip t ng, xc nh th vt, theo di lu thng. Trong giai on ny tag c IC tiptc pht trin v c tnh:b nh ghi c, tc c nhanh hn v khong cch cxa hn.

u thp nin 80 cng ngh phc tp RFID c p dng trong nhiu ng dng: t ti ng ray M, nh du th vt trn nng tri chu u. H thng RFID cn dng trongnghin cu ng vt hoang d nh du cc loi nguy him.

Vo thp nin 90, h thng thu ph in t tr nn ph bin Thi Bnh Dng: , TyBan Nha, B o Nha v M: Dallas, New York v New Jersey. Nhng h thng nycung cp nhng dng truy cp iu khin phc tp hn bi v n cn bao gm c my tr

tin.u nm 1990, nhiu h thng thu ph Bc M tham gia mt lc lng mang tn E-

ZPass Interagency Group (IAG)cng nhau pht trin nhng vng c h thng thu ph int tng thch vi nhau. y l ct mc quan trng to ra nhng ng dng tiu chun.Hu ht nhng tiu chun tp trung cc c tnh k thut nh tn s hot ng v giao thcgiao tip phn cng.

E-Zpasscn l mt tag n tng ng vi mt ti khon trn mt phng tin. Tag caxe s truy cp vo ng cao tc ca h thng thu ph m khng phi dng li. E-Z Passgip lu thng d dng hn v gim lc lng lao ng kim sot v v thu tin.

Cng vo thi im ny, kha (card RFID)s dng ph bin thay th cho cc thitb my mc iu khin truy nhp truyn thng nh kha kim loi v kha s. Nhng snphm ny cn c gi l th thng minh khng tip xc cung cp thng tin v ngi dng,trong khi gi thnh thp sn xut v lp trnh. Bng 2-1 so snh cc phng php iukhin truy cp thng thng v iu khin truy cp RFID.


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Phng php iukhin truy nhp

u im

Cha kha kim loi

Khng cn ngunin

D s dng D dng copy Kha c th b D b trm

Kha kt hp C th d dng thayi s kt hp

Khng c cha khann khng lo b mthay b nh cp

t hn kha kim loiD b tn cng

Th ng du

Khng th nhn lnd dng nh khakim loi

S dng k thut c tlinh hot

Th dng di t trng Kh copy C sn b c card

S dng lu th s hVic lt t yu cu c

s IT

Th thng minh Cng mt th c th

s dng cho nhiung dng

C kh nng bo mtcao hn th dng dit trng

t hn th t trng

RFID Nh th thng minh Khng cn phi tip

xc C th gn ln sn

phm v di da

t hn th thngminh

iu khin truy nhp RFID tip tc c nhng bc tin mi. Cc nh sn xut xe hi dng tag RFID trong gn mt thp k qua cho h thng nh la xe hi v n lm gimkh nng trm cp xe.


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Hnh 2.3 Nhng mc quan trng t nm 1960 n 1990

c. RFID pht trin trn phm vi ton cuCui th k 20, s lng cc ng dng RFID hin i bt u m rng theo hm m trn

phm vi ton cu. Di y l mt vi bc tin quan trng gp phn y mnh s pht

trin ny.Texas Instrument i tin phong M

o nm 1991, Texas Instrument i tin phong trong h thng RFID M, cng ty to ra mt h thng xc nhn v ng k Texas Instrument (TIRIS). H thng TI-RFID(Texas Instruments Radio Frequency Identification System) n tn cho phttrin v thc hin nhng lp mi ca ng dng RFID.

Chu u bt u cng ngh RFID t rt sm

Ngay c trc khi Texas Instrument gii thiu sn phm RFID, vo nm 1970 EMMicroelectronic-Marin mt cng ty ca The Swatch Group Ltd thit k mch tch hp

nng lng thp cho nhng ng h ca Thy S. Nm 1982 Mikron IntegratedMicroelectronics pht minh ra cng ngh ASICv nm 1987 pht trin cng ngh c bitlin quan n vic xc nh th thng minh. Ngy nay EM Microelectronic v PhilipsSemiconductorsl hai nh sn xut ln chu u v lnh vc RFID.

Pht trin th th ng trong thp nin 90

Cch y mt vi nm cc ng dng ch yu ca th RFID th ng, nh minh hatrong bng 2.2mi c ng dng tn s thp (LF) v tns cao (HF) ca ph RF. C LFv HF u gii hn khong cch v tc truyn d liu. Cho nhng mc ch thc tkhong cch ca nhng ng dng ny o bng inch. Vic gii hn tc

ng khi hng trm thm ch hng ngn tag cng c mt trong trng ca bc ti mt thi im. Cui thp nin 90 tag th ng cho tn s siu cao (UHF) lm chokhong cch xa hn, tc cao hn, gi c r hn, tag th ng ny v

nhng thuc tnh thm vo h thng RFID da trn UHF c lachn cho nhng ng dng dy chuyn cung cp nh qun l nh kho, kim k sn phm.


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Bng 2.2 Cc ng dng tiu biu dng cng ngh RFID LF v HF

iu khin truy nhp Xc nh ng vt

Xc nh hng ha trn my bay Thanh ton tin

Chng trm cho xe hi Gim st in tnh du ti liu nh thi cho th thao

ng nm 1990 u nm 2000 cc nh phn phi nh Wal-Mart, Target, MetroGroupv cc c quan chnh ph nh U.S. Department of Defense (DoD)bt u pht trinv yu cu vic s dng RFID bi nh cung cp. Vo thi im ny EPCglobalc thnhlp,EPCglobal h tr h thng m sn phm in t (Electronic Product Code Network

EPC)h thng ny tr thnh tiu chun choxc nhn sn phm t ng.

Hnh 2.4 Nhng mc quan trng t nm 1990 n nay

III - Thnh phn ca mt h thng RFIDMt h thng RFID l mt tp hp cc thnh phn m n thc thi gii php RFID. Mt

h thng RFID bao gm cc thnh phn sau :

Tag: l mt thnh phn bt buc i vi mi h thng RFID.

Reader:l thnh phn bt buc.

Reader anten:l thnh phn bt buc. Mt vi reader hin hnh ngy nay cng

c sn anten.Mch iu khin (Controller): l thnh phn bt buc. Tuy nhin, hu ht ccreader miu c thnh phn ny gn lin vi chng.

Cm bin (sensor), c cu chp hnh (actuator) v bng tn hiu in bo(annunciator): nhng thnh phn ny h tr nhp v xut ca h thng.


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My ch v h thng phn mm:V mt l thuyt, mt h thng RFID c thhot ng c lp khng c thnh phn ny. Thc t, mt h thng RFID gn nhkhng c ngha nu khng c thnh phn ny.

C s h tng truyn thng: l thnh phn bt buc, n l mt tp gm c haimng c dy v khng dy v cc b phn kt ni tun t kt ni cc thnh phn lit k trn vi nhau chng truyn vi nhau hiu qu.

Hnh 2-5l mt m hnh h thng RFID.

Hnh 2-5 S khi mt h thng RFID

Hnh 2-6 H thng RFID vi cc thit b


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IV - Phng thc lm vic ca RFIDMt h thng RFID c ba thnh phn c bn: tag, u c, v mt my ch. Tag RFID

gm chip bn dn nh v anten c thu nh trong mt s hnh thc ng gi. Vi t ag RFIDging nh nhng nhn giy v c ng dng b vo hp v ng gi. Mt s khc cdn vo cc vch ca cc thng cha lm bng plastic. Cn mt s khc c xy dng

thnh ming da bao c tay. Mi tag c lp trnh vi mt nhn dng duy nht cho phptheo di khng dy i tng hoc con ngi ang gn tag . Bi v cc chip c s dngtrong tag RFID c th gi mt s lng ln d liu, chng c th cha thng tin nh chuis, thi du, hng dn cu hnh, d liu k thut, s sch y hc, v lch trnh. Cng nh

pht sng tivi hay radio, h thng RFID cng s dng bn bng thng tn s chnh: tn sthp (LF), tn s cao (HF), siu cao tn (UHF) hoc sng cc ngn (viba). Cc h thngtrong siu th ngy nay hot ng bng thng UHF, trong khi cc h thng RFID c sdng bng thng LF v HF. Bng thng viba ang c dnh cho cc ng dng trongtng lai.

Cc tag c th c cp ngun bi mt b pin thu nh trong tag (cc tag tch cc) hoc

bi reader m n wake up(nh thc)tag yu cu tr li khi tag ang trong phm vi(tag th ng).

2-7 er RFI D

Tag tch cc c xa 100 feet tnh t reader v c th l t ag RW (vi b nh c vitln v xa nh mt cng my tnh) hoc l tag RO. Tag th ng c th c c xareader 20 feet v c b nh RO. Kch thc tag, gi c, di c, chnh xc c/ghi, tc d liu v chc nng h thng thay i theo c im nu ra trong thit k v di tn hthng FRID s dng.

Reader gm mt anten lin lc vi tag v mt n v o in t hc c ni mngvi my ch. n v o tip sng gia my ch v tt c cc tag trong phm vi c caanten, cho php mt u c lin lc ng thi vi hng trm t ag. N cng thc thi cc chcnng bo mt nh m ha/ gii m v xc thc ngi dng. Reader c th pht hin tag ngay


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c khi khng nhn thy chng. Hu ht cc mng RFID gm nhiu tag v nhiu u cc ni mng vi nhau bi mt my tnh trung tm, hu nh thng l mt trm lm vicgn bn. My ch x l d liu m cc reader thu thp t cc tag v dch n gia mngRFID v cc h thng cng ngh thng tin ln hn, m ni qun l dy chuyn hoc cs d liu qun l c th thc thi. Middleware l phn mm ni h thng RFID vi mt hthng IT qun l lung d liu.

V - Cc ng dng RFIDCc ng dng thng mi cho u t v cung cp vic qun l dy chuyn ang khin

cho s pht trin v gia tng cng ngh RFID. Wal-Mart, trung tm bn l ln nht thgii, v khu qun s M (DoD), nh iu hnh dy chuyn ln nht th gii thc y sgia tng ny bi vic yu cu cc nh cung cp s dng tag RFID. Wal-Martyu cu 100nh cung cp ln nht bt u lm th pallet v cho vo hp cc th RFID th ng trcthng 1 nm 2005, thc y cc nh bn l khc thc hin k hoch tng t. DoDnhanhchng theo v yu cu thm cc thngng hng c vn c lc a M c cctag RFID ch ng nhn bit ci cha ng bn trong v ngun gc. S pht trin caWal-Mart, DoD, nhim v RFID l a cng ngh ny thnh xu th ch o v lm cho nsinh li nhiu hn.

Hng sp nhp cng ngh RFID thnh dy chuyn c thc y bi c li m dthy trong bn kim k: tng lt vn chuyn, nhn, cung cp c nng sut, gim gi chovic lao ng chn tay, xp hng v s tht thot kim k. Cc reader c ci lc cht hng cc ca bn tu c th pht hin tag trn hng ha hoc cc pallet qua ca. u c gimt lnh n tag pht cc nhn dng ca chng, thu thp thng tin ny v chuyn tip nmy tnh. V my tnh ghi c s d liu kim k da vo hng ha l nhp hay xut. Nuh thng s dng cc tag thng minh, th my tnh c th ghi ngy giao/nhn v thi giantrn tag.

Cng cng nhng kh nng lm cho tng RFID qun l dy chuyn c th mnhtrong an ninh quc gia, v lut php. Cc ng dng gm c tnh kim tra (chng hn sngcm tay, thit b lin lc, my tnh), kim tra bng chng, passport v kim tra visa, kim tracn b trong cc tin nghi v xm nhp h thng iu khin trong cc ta nh hoc cc

phng (chng hn nh cc thit b ra vo khng kha). Cng ngh RFID c xy dngtrong vic x pht v an ninh quc gia rng hn trong lut php.

:

, an ninh:

p: k

:


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: : Fastrak, EZ-pass , nh ht1. RFID trong vic x pht

Cng ngh RFID to iu kin x pht d dng, thay i cc nhim v thng l m ni hi nhiu thi gian thnh cc nhim v in t c thc thi t ng vi chi ph thp.Thm na l c thlu li to h thng hon chnh, hiu qu hn. Vic s dng h thngRFID lm tng an ninh, gim bo lc, to ra mi trng an ton chob phn nhn vin.

Vic x pht California, Michigan, Illinois v Ohio ang s dng mt h thng theodi RFID c pht trin bi cng ty da vo Arizona. H thng ny c 5 thnh phn chnh:my pht c ng h eo tay pht hin s gi mo, mt my pht eo tht lng c mang

bi nhn vin, mt dy tip nhn anten c t theo v tr chin lc, mt h thng mytnh, vphn mm ng dng c quyn.

My pht c mc bi phm nhn v nhn vin gi tn hiu radio duy nht mi 2pht, cho php h thng xc nh v tr ca ngi eo v theo di v ghi nhn s di chuynca h d dng trong thi gian mt u in t m mi 2

pht v gi mt cnh bo nu mt t nhn mt tch. Nu mt t nhn vo mt vng cmhoc c tho my pht ng h eo tay, thit b pht tn hiu mt cnh bo n my tnhgim st. Nu mt t nhn nh nhn vin hoc tho my pht t dy lng ca nhn vin,my pht ca nhn vin gi tn hiu cnh bo. Cc nhn vin cng c th gi mt cnh bo

bng cch nhn mt nt khn cp trn my pht.

H thng RFID ghi li tt c d liu theo di c thu thp ln mt giai on quynh trong mt c s d liu c lu tr c nh. iu ny cho php h thng nhn din v

bo co tt c t nhn trong vng ln cn ca bt k vic tnh c xy ra no gy ra cnh bo.Vic qun l khc bo co cc ng dng gm thuc ung v phn pht ba n, tham gia thikha biu v thng tin ra v c th.

2. RFID trong an ninh quc giaHi an ninh quc gia M (DHS) nm bt RFID nh mt cng ngh c chn cho

vic ci tin an ninh bin gii M v ca khu. Cng ngh RFID l tng xc nh v tr,theo di v xc thc s i li ca mi ngi v cc i tng m h vo ra .

Vo thng 01 nm 2005, DHS thng bo cc k hoch bt u kim tra cng ngh

RFID di sng kin US-VISIT, m gi n dng k thut sinh trc hc xc minh nhndng ca cc khch nc ngoi sn bay 115 v cng 14. Mt ngn tay tr ca khch cscan ly du tay v mt nh s c chp. Du tay v nh c dng xc thc ti liuthng hnh ca khch, c ghi li v c kim tra i chiu vi cc danh sch phn tkhng b.

t ng x l vo ra, kim tra bng chng, DHSs cho cc du khch tag c mt sID duy nht m n lin kt vi du tay s ca h, hnh nh v thng tin c nhn khc trongc s d liu an ninh ca US-VISIT. tng ny l s s dng cc tag ch c th ng


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khng th thay i g c trn n. Thng tin c nhn s khng c lu trn tag. Cngngh RFID ci tin kh nngca hi quan M v nhn vin bo v bin gii so khp svo ra bin gii lnh th nhanh chng, chnh xc v ng tin cy. Tag s cho php t ngghi vic ra vo ca du khch trong khch b hnh, xe c v c th cho nhn vin bin giikim tra nhanh lng thi gian hnh khch li M v h c qu mc visa hay khng.

Vic ngn nga v kh ca cc v ph hoi cng chng t cc thng hng vo M lu th cao khc choDHS. CSIthng bo nm 2002 l thit b pht hin tia phng x v nhX quang hay gamma ang c dng kim tra cc thng ng hng ha trc khi chngc vn chuyn n M. CSI cng cn pht trin cc thng cha thng minh, mt ngdng r rng cho cng ngh RFID. D nhin, RFID s l mt cha kha bo m cho cc

bin gii vh thng giao thng.

3.lm

c y.

.

1Hughes Identification Devices (HID)

/ghi 2-8).

2-9).

-


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2-9

VI - Nhc im ca h thng RFIDGi cao:Nhc im chnh ca cng ngh RFID l gi cao.

D b nh hng:c th lm tn hi h thng RFID bi vic ph vt liu bo v t 2n 3 lp kim loi thng thng ngn chn tn hiu radio. Cng c th tn hi h thngRFID bivic t hai item i ngc, iu c th hy cc tn hiu. iu ny i hi kin thc v k thut v s canh thng hng cn thn.

Vic th tiu cc tag:cc tag RFID c dn bn trong bao b v c ph ra d thtiu. iu ny c ngha l s c nhiu vn khi ngi s dng bit r hn v vai tr catag.

Nhng lin quan ring t ngi s dng:Vn vi h thng RFID th vin ngynay l cc tag cha thng tin tnh m n c th c c d dng bng cc u c tag tri

php.ng u c:Tn hiu t mt u c c th giao tip vi tn hiu t ni khc m

ni tin tc chng cho nhau. iu ny c gi l ng u c. Mt phng phptrnh vn ny l s dng k thut phn chia thi gian a truy cp (TDTM).

ng tag, thiuchun.


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CHNG 2TAG RFID

) RFID l mt thit b c th lu tr v truyn d liu n mt reader trongmt mi trng khng tip xc bng sng v tuyn.Tag RFID mang d liu v mt vt, mtsn phm (item)no v gn ln sn phm . Mi tag c cc b phn lu tr d liu bntrong v cch giao tip vi d liu . Hnh 3-1m t s ca mt s tag tiu biu.

RFID u c vi chip v ngun nng lng ring.

3

Tt c cc tag u c cc im chung, phn loilm vic ca tag. Phn loi tag da trn mt s tiu chun gy nh hng n tag trong ngdng. Chng ta s phn loi tag da trn cc c im vt l, cc giao din khng kh airinterface (cch m chng giao tip c vi b c), kh nng lu tr v x l thng tin.

I - Cc kh nng c bn ca tag:

Gn tag: bt k tag no cng c gn ln itemtheo nhiu cch c tag: tag RFID phi c kh nng giao tip thng tin qua sng radio theo nhiu cch.

Nhiu tag cn c mt hoc nhiu thuc tnh hoc c im sau:

Kill/disable: Nhiu tag cho php b c ra lnh cho n ngng cc chc nng. Sau khitag nhn chnh xc kill code, tag s khng p ng li b c.


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Ghi mt ln (write once): Vi tag c sn xut c d liu c nh th cc d liu nyc thit lp ti nh my, nhng vi tag ghi mt ln d liu ca tag c th c thit lpmt ln bi ngi dng sau d liu ny khng th thay i. Ghi nhiu ln (write many): nhiu kiu tag c th c ghi d liu nhiu ln. Anti-collision: Khi nhiu tag t cnh nhau, b c s gp kh khn nhn bit khi

no p ng ca mt tag kt thc v khi no bt u mt p ng khc. Vi tag anti-

collision s nhn bit c thi gian p ng n b c. M ha v bo mt (Security and encryption): Nhiu tag c th tham gia vo cc giao

tip c mt m, khi tag ch p ng li b c ch khi cung cp ng password.

II -Tag RFID mang d liu c gn ln sn phm c hn

, tag c th c phn loi theo hnh dng vkch thc. Hn na tag c th to thnh t nhiu kiu d liu khc nhau. Sau y l mt vic im vt l:

Tag hnh cc o hoc a lm bng PVC, nha thng thng c mt l gia mc.Tag ny bn v c th s dng li c.

Tag RFID c hnh dng nh th tn dng cn gi l cc th thng minh khng tip xc. Tag nh gn vo cc sn phm nh: qun o, ng h, trang sc ... Nhng tag ny c

hnh dng cha kha v chui kha. Tag trong hp thy tinh c th hot ng trong cc mi trng n mn hoc trong cht

lng.

Hnh 3-2. Cc hnh dng v kch thc ca tag

Mt cch n gin phn v ng gi tag nh hngtrc tip n vic gn tag vo item.


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III - Tn s hot ngTn s hot ng l tn s in t tag dng giao tip hoc thu c nng lng.

Ph in t m RFID thng hot ng l tn s thp (LF), tn s cao (HF), siu cao tn(UHF) v vi sng (Microwave) bng 3-1. V h thng RFID truyn i bng sng in t,chng cng c iu chnh nh thit b radio. H thng RFID khng c gy cn tr cc

thit b khc, bo v cc ng dng nh radio cho cc dch v khn cp hoc truyn hnh.3-

Tn

LF 30300 kHz < 135 kHzHF 330 MHz 6.78 MHz, 13.56 MHz, 27.125 MHz, 40.680 MHzUHF 300 MHz-3 GHz 433.920 MHz, 869 MHz, 915 MHz

(Microwave)> 3 GHz 2.45 GHz, 5.8 GHz, 24.125 GHz

Trong hot ng, tn s RFID thc t b gii hn bi nhng mc tn s nm bn phnIndustrial Scientific Medical (ISM). Tn s thp hn 135kHz khng phi l tn s ISM,nhng trong khong ny h thng RFID dng ngun nng lng t trng v hot ng khong cch ngn v vy nhiu pht ra t hn ti tn s khc.

3-

LF

HF

UHFMicrowave

Gn y tag UHF gim gi dn n vic s dng tag trong cc ng dng tng ln khitrc tag LF v HF c dng ch yu. Tuy nhin tag UHF khng c dng thay thcho tag LF trong tag cy hoc tag vi sng trong cc ng dng khong cch ln (khongcch c hn 10m).

IV -Cc tag RFID c th c phn loi theo hai phng php khc nhau. Danh sch sau

trnh by vic phn loi th nht, da trn vic tag c cha ngun cung cp gn bn trong

hay l c cung cp bi reader: Th ng (Passive) Tch cc (Active) Bn tch cc (Semi-active, cng nh bn th ng semi-passive)


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1. Tag th ngLoi tag ny khng c ngun bn trong, s dng ngun nhn c t reader hot

ng v truyn d liu c lu tr trong n cho reader. Tag th ng c cu trc n ginv khng c cc thnh phn ng. Tag nh th c mt thi gian sng di v thng c scchu ng vi iu kin mi trng khc nghit. Chng hn, mt s tag th ng c th chung cc ha cht gm mnnh acid, nhit ln ti 400F (xp x 204C) v nhit caohn na.

i vi loi tag ny, khi tag v reader truyn thng vi nhau th reader lun truyntrc ri mi n tag. Cho nn bt buc phi c reader tag c th truynd liu ca n.

Tag th ng nh hn tag tch cc hoc tagbn tch cc. N c nhiu phm vi c, thn 1 inch n khong 30 feet (xp x 9 m ).

Tag th ng cng r hn tag tch cc hoc bn tch cc. Th thng minh (smart card)l mt loi tag RFID th ng, ngy nay n c s dng rng ri trong cc lnh vc khcnhau (chng hn nh huy hiu ID). D liu trn tag ny c c khi n gn reader. Tag nykhng cn phi tip xc vi reader trong qu trnh c.

Tag th ng bao gm nhng thnh phn chnh sau:

Vi mch (microchip). Anten.

1.1Vi mchHnh ditrnh by nhng thnh phn c bn ca mt vi mch.


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Thnh phn c bn ca mt vi mch

Trong : B chnh lu(power control/rectifier): chuyn ngun AC t tn hiu anten ca reader

thnh ngun DC. N cung cp ngun n cc thnh phn khc ca vi mch.

My tch xung(Clock extractor): rt tn hiu xung t tn hiu anten ca reader. B iu ch (Modulator): iu chnh tn hiu nhn c t reader. p ng ca tag

c gn trong tn hiu iu ch, sau n c truyn tr li reader.

n v lun l (Logic unit): chu trch nhim cung cp giao thc truyn gia tag vreader

B nh vi mch(memory): c dng lu tr d liu. B nh ny thng c phnon (gm vi block hoc field). Addressability c ngha l c kh nng phn tch (c hocghi) vo b nh ring ca mt vi mch ca tag. Mt block nh ca tag c th gi nhiu loid liu khc nhau, v d nh mtphn ca d liu nhn dng i tng c gn tag, cc bitchecksum (chng hn kim tra li CRC) kim tra chnh xc ca d liu c truynv.v S tin b ca k thut cho php kch thc ca vi mch nh n mc nh hn htct. Tuy nhin, kch c catag khng c xc nh bi kch thc vi mch ca n m bichiu di anten ca n.

1.2AntenAnten ca tag c dng ly nng lng t tn hiu ca reader lm tng sinh lc

cho tag hot ng, gi hoc nhn d liu t reader. Anten ny c gn vo vimch. Antenl trung tm i vi hot ng ca tag.

C th c nhiu dng anten, nht l vi tn s UHF v thit k mt anten cho mt tagl c mt ngh thut. Chiu di anten tng ng vi bc sng hot ng ca tag. Mt antenlng cc bao gm mt dy dn in (chng hn ng) m n b ngt trung tm. Chiu ditng cng ca mt anten lng cc bng na bc sng tn s c dng nhm ti u nnglng truyn t tn hiu anten ca reader n tag. Mt anten lng cc bao gm hai cc, cth gim c nhy chun trc ca tag (tags alignment sensitivity). Reader c th c


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tag ny nhiu hng khc nhau. Folded dipolebao gm hai hoc nhiu dy dn in cni song song nhau v mi dy bng na chiu di bc sng ca tn s c dng. Khi haidy dn c cun vo nhau th folded dipole c gi l 2-wire folded dipole. Loi 3-wirefolded dipolebao gm ba dy dn in c ni sng song nhau.

`Cc loi anten lng cc

Chiu di anten ca tag thng ln hn nhiu so vi vi mch ca tag v vy n quytnh kch c vt l ca tag. Mt anten c th c thit k da trn mt s nhn t sau y:

Khong cch c ca tag vi reader. Hng c nh ca tag i vi reader. Hng ty ca tag i vi reader. Loi sn phm ring bit. Vn tc ca i tngc gn tag. phn cc anten ca reader.

Nhng im kt ni gia vi mch ca tag v anten l nhng kt ni yu nht ca tag.

Nu c bt k im kt ni no b hng th xem nh tag khng lm vic c hoc c thhiu sut lm vic gim ng k. Anten c thit k cho mt nhim v ring bit (nh gntag vo mt hp) c th hot ng km hn khi thc hinnhim v khc (nh gn tag vomt item ring l trong hp). Vic thay i hnh dng anten mt cch t ng (chng hngim hoc gp n li) khng phi l mt tng hay v iu ny c th lm mt iu hngtag, a n hiu sut cng gim theo. Tuy nhin, mt s ngi bit h s phi lm g cth gim anten ca tag mt iu hng n (chng hn nh khoan mt l tag) v tht slm tng kh nng c ca tag.


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Hin ti, anten ca tag c xy dng bng mt mnh kim loi mng (chng hn ng,bc hoc nhm). Tuy nhin, trong tng lai c th s in trc tip anten ln nhn tag, hp vsn phm ng gi bng cch s dng mt loi mc dn c cha ng, cacbon v niken.Hin nay vi mch cng ang c nghin cu xem n c th c in vi loi mc haykhng. Ci tin tng lai ny cho php in mt tag RFID nh m vc

n n chi ph cho mt tag RFID c th gim di mc 0.5$ mt tag. Nu khng

c kh nng in mt vi mch, th anten c in cng c th c gn vo mt vi mch tomt tag RFID hon chnh nhanh hn nhiu vic gn mt anten kim loi.Sau y l cc tagth ng t nhiu i l cung cp:

Instrument


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Tag

2. Tag tch ccTag tch cc c mt ngun nng lng bn trong (chng hn mt b pinhoc c th l

nhng ngun nng lng khc nh s dng ngun nng lng mt tri) v in t hc

thc thi nhng nhim v chuyn dng. Tag tch cc s dng ngun nng lng bn trong truyn d liu cho reader. N khng cn ngun nng lng t reader truyn d liu.bn trong gm b vi mch, cm bin v cc cng vo/ra c cp ngun bi

ngun nng lng bn trong n. V vy, nhng thnh phn ny c th o c nhit xungquanh v pht ra d liu nhit chun. Nhng thnh phn ny c th s dng d liu ny xc nh cc tham s khc nh hn s dng ca item c gn tag. Tag c th truynthng tin ny cho reader (cng vi t nh danh duy nht ca n). Ta c th xem t ag tch ccnh mt my tnh khng dy vi nhng c tnh thm vo (chng hn nh mt cm binhoc mt b cm bin).

i vi loi tag ny, trong qu trnh truyn gia tag v reader, tag lun truyn trc,

ri mi n reader. V s hin din ca reader khng cn thit cho vic truyn d liu nntag tch cc c th pht d liu ca n cho nhng vng ln cn n thm ch trong c trnghp reader khng c ni . Loi tag tch cc ny (truyn d liu lin tc khi c cng nhkhng c reader hin din) cng c gi l my pht (transmitter).

Loi tag tch cc khc trng thi ng hoc ngun yu khi khng c reader. Readernh thc tag ny khitrng thi ng bng cch pht mt lnh thch hp. Trng thi ny titkim ngun nng lng, v vy loi tag ny c thi gian sng di hn tag tch cc c gil my pht k trn. Thm na l v tag ch truyn khi c thm vn nn s nhiu RF trongmi trng cng b gim xung. Loi tag tch cc ny c gi l mt my pht/my thuhoc mt b tch sng-tag c th hot ng ch my pht v my thu. Tag ny ch

truyn khi c reader thm vn. Tag trng thi ng hoc ngun gim khi khng creader thm vn. V vy tt c tag ny c th c gi l transponder.Khong cch c ca tag tch cc l 100 feet (xp x 30.5 m) hoc hn na khi my pht tchcc ca loi tag ny c dng n.

Tag tch cc bao gm cc thnh phn chnh sau:

Vi mch (microchip). Anten.


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Cung cp ngun bn trong. in t hc bn trong.

Hai thnh phn u tin c m t trn. Sau y, hai thnh phn sau s c cp.

2.1Ngun nng lng bn trongTt c cc tag tch cc u mang mt ngun nng lng bn trong cung cp ngun

v truyn d liu. Nu s dng b pin th tag tch cc thng ko di tui th t 2 n 7 nmty thuc vo thi gian sng ca b pin. Mt trong nhng nhn t quyt nh thi gian sngca b pin l tc truyn d liu ca tag. Nu khong cch cng rng th b pin cngtn ti lu v v th thi gian sng ca tag cng di hn. Chng hn, tag tch cc truyn miln vi giy. Nu tng thi gian ny tag c th truyn mi ln vi pht hoc vi gi ththi gian sng ca b pin c ko di. Cm bin v b x l bn trong s dng ngun nnglng c th lm gim thi gian sng ca b pin.

Khi b pin trong tag tch cc hon ton phng in th tag ngng truyn thng ip.

Reader ang c nhng thng ip ny khng bit b pin ca tag c b cht hay l sn phmc gn tagbin mt khi phm vi c ca n tr khi tag truyn tnh trng pin cho readerny.

2.2in t hc bn trongin t hc bn trong cho php tag hot ng nh mt my pht v cho php n thc

thi nhng nhim v chuyn dng nh tnh ton, hin th gi tr cc tham s ng no ,hoc hot ng nh mt cm bin, v.v Thnh phn ny cng c th cho php chn la ktni vi cc cm bin bn ngoi. V vy tag c th thc thi nhiu nhim v thng minh, tythuc vo loi cm bin c gn vo. Ni cch khc th phm vi lm vic ca thnh phnny hu nh v hn. V vy kh nng lm vic v kch thc ca thnh phn ny tng th tagcng tng kch thc. C th tng kch thc vi iu kin l n c th c trin khai(ngha l c gn ng cch vo i tng cn c gn tag). iu ny mun ni cc tagtch cc c th c ng dng rng ri, c mt s hin nay khng cn.


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3-33. Tag bn tch cc (Semi-Passive)

Tagbn tch cc c mt ngun nng lng bn trong (chng hn l b pin) v in thc bn trong thc thi nhng nhim v chuyn dng. Ngun bn trong cung cp sinh lccho tag hot ng. Tuy nhin trong qu trnh truyn d liu, tagbn tch cc s dng ngunt reader. Tag bn tch cc c gi l tag c h trpin (battery-assisted tag).

i vi loi tag ny, trong qu trnh truyn gia tag v reader th reader lun truyntrc ri n tag. Ti sao s dng tag bn tch cc m khng s dng tag th ng? Bi vtagbn tch cc khng s dng tn hiu ca reader nh tag th ng, n t kch ng, n cth c khong cch xa hn tag th ng. Bi v khng cn thi gian tip nng lnglccho tagbn tch cc, tag c th nm trong phm vi c ca reader t hn thi gian c quynh (khng ging nh tag th ng). V vy nu i tng c gn tag ang di chuyn tc cao, d liu tag c th vn c c nu s dng tagbn tch cc. Tagbn tch cccng cho php c tt hn ngay c khi gn tag bng nhng vt liu chn tn s v tuyn(RF-opaque v RF-absorbent). S c mt ca nhng vt liu ny c th ngn khng cho tagth ng hot ng ng dn n vic truyn d liu khng thnh cng . Tuy nhin, ykhng phi l vn kh khn i vi tag bn tch cc.

Phm vi c ca tag bn tch cc c th ln n 100 feet (xp x 30.5 m) vi iu kinl tng bng cch s dng m hnh tn x c iu ch (modulated back scatter)trong

UHF v sng vi ba.Hnh 3-4n 3-6trnh by cc tag tch cc v bn tch cc ca nhiu i l cung cp.


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Hnh 3-4 Tag tch cc Mantis UHF thp 303.8 MHz vi my d s chuyn ng c cit sn ca RFCode, Inc.

Hnh 3-5 Cc tag bn tch cc 2.45 GHz ca Alien Technology

Hnh 3-6 Cc tag bn tch cc 915 MHz/2.45 GHz ca TransCore

Vic phn loi tip theo da trn kh nng h tr ghi chp d liu:

Ch c (RO)Ghi mt ln, c nhiu ln (WORM)c-Ghi (RW)


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4. Read Only (RO)Tag Read Only (RO) c th c lp trnh (tc l ghi d liu ln tag RO) ch mt ln.

D liu c th c lu vo tag ti trong lc sn xut. Vic ny c thc hin nhsau: cc fuse ring l trn vi mch ca tag c lu c nh bng cch s dng chm tialaser. Sau khi thc hin xong, khng th ghi d liu ln tag c na. Tag ny c gilfactory programmed (lp trnh ti nh my).Nh sn xut loi tag ny s a d liu lntag v ngi s dng tag khng th iu chnh c. Loi tag ny ch tt i vi nhng ngdng nh m khng thc t i vi quy m snxut ln hoc khi d liu ca tag cn clm theo yu cu ca khch hng da trn ng dng. Loi tag ny c s dng trong ccng dng kinh doanh v hng khng nh.

5. Write Once, Read Many (WORM)Tag Write Once, Read Many (WORM) c th c ghi d liu mt ln, m thng th

khng phi c ghi bi nh sn xut m bi ngi s dng tag ngay lc tag cn c ghi.Tuy nhin trong thc t th c th ghi c vi ln (khong 100 ln). Nu ghi qu s ln cho

php, tag c th b ph hng vnh vin. Tag WORM c gi l field programmable (lptrnh theo trng).

Loi tag ny c gi c v hiu sut tt, c an ton d liu v l loi tagph bin nhttrong lnh vc kinh doanh ngy nay.

6. Read Write (RW)Tag RW c th ghi d liu c nhiu ln, khong t 10.000 n 100.000 ln hoc c

th hn na. Vic ny em li li chrt ln v d liu c th c ghi bi reader hoc bitag (nu l tag tch cc). Tag RW gm thit b nh Flash v FRAM lu d liu. T ag RWc gi l field programmablehoc reprogrammable (c th lp trnh li). S an ton d

liu l mt thch thc i vi tag RW, thm vo na l loi tag ny thng t nht. TagRW khng c s dng rng ri trong cc ng dng ngy nay, trong tng lai c th cngngh tagpht trin th chi ph tag gim xung.

7. Mt s kiu tag khc7.1Tag SAW (Surface Acoustic Wave SAW)

bn

).Ta .


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Tag SAW

Tag SAW khc vi cc tag da trn vi mch. Tag SAW bt u xut hin trn thtrng v c th c s dng rng ri trong tng lai. Hin ti th thit b SAW c sdng trongcc mng in thoi t bo, tivi mu, v.v

Tag SAW s dng sng RF nng lng thp hot ng trong bng tn ISM 2.45 GHz.Khng ging nh cc tag da trn vi mch, tag SAW khng cn ngun DC tip sinh lchot ng cho n truyn d liu. Sau y l hnh trnh by cch hot ng ca loi tag ny.

Hot ng ca tag SAW

Tag SAW bao gm mt anten lng cc c gn vo my bin nng interdigital(IDT)c t trong nn p in (piezoelectric substrate) c lm bng lithium niobatehoc lithium tantalate. Mt dng in cc ring l nh nhng dng phn x (c lm bng

nhm hoc khc axit trn nn) c t trn nn. Anten t mt xung in vo IDT khi nnhn tn hiu RF ca SAW reader. Xung ny pht sinh sng (surface) cn gi l sngRaleigh, thng i c 3.000 m n 4.000 m trn giy trn nn . Mt s sng ny c

phn x tr li IDT bi nhng dng phn x (reflector), vic ngh c thu bi nn ny. Ccsng phn x to thnh mt m hnh duy nht, c xc nh bi cc v tr phn x, miu td liu catag. Cc sng ny thng c chuyn i thnh tn hiu RF trong IDT v ctruyn li reader qua anten ca tag. Reader gii m tn hiu nhn c c d liu catag.


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Tag SAW c cc u im sau y:

S dng nng lng rt thp v n khng cn ngun DC tip sinh lc hot ng. C th gn tag vo nhng vt liu chn sng v tuyn (RF-opaque v RF-absorbent),

nh kim loi hoc nc.

C phm vi c ln hn tag vi mch hot ng trong cng bng tn (bng tn 2.45 GHz)

C th hot ng tn hiu v tuyn ngn tri ngc vi tag da trn vi mch (cn thihiu tn hiu t reader n tag di hn nhiu)

Vic c c t l chnh xc cao. Thit k n gin. Khng cn giao thc phng nga ng (anti-collision protocol). Giao thc nga

ng ch cn c thchin reader thay v c reader v tag nh tag vi mch (v vygim chi ph tag SAW)

Cc SAW reader t xy ra nhiu vi cc SAW reader khc. Tag SAW rt tt, l s lachn duy nht trong cc hon cnh no v cng c s dng rng ri trong tng lai.

Mt s tag c th truyn d liu n reader m khng s dng sng v tuyn.

7.2Tag Non-RFIDKhi nim gn tag v truyn v tuyn ID duy nht ca n n reader khng phi l

vng sng dnh ring. C th s dng cc loi truyn v tuyn khc cho mc ch ny.Chng hn c th s dng sng siu m hoc sng hng ngoi i vi vic truyn thng giatag vi reader.

Vic truyn siu m c u im l khng gy ra nhiu vi thit b in hin c vkhng th xuyn qua tng. V th nhng h thng gn tag siu m c th c trin khaitrong bnh vin m ni k thut nh th ny c th cng tn ti vi thit b y t hin c.Thm na l reader siu m v tagphi nm trong cng phng reader c c d liu catag. iu ny gip d kim sot ti sn.

Tag hng ngoi s dng nh sng truyn d liu n reader. V nh sng khng thxuyn qua tng nn tag v reader hng ngoi phi t trong cng phng truyn vinhau. Nu c vt cn ngun sng ca tag th tag khng cn truyn vi reader na (y l mtnhcim).

7.3(Electronic Article Surveillance EAS)

h .

-

.


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.

.

.

.

V - Giao thc tagTrong phn ny, ta s nghin cu cc giao thc m reader v tag s dng trao i

thng ip thng qua giao din khng gian (air interface) cng nh xem xt chi tit thng tin

c lu tr trn tag.Jargon File l mt t in v cc thut ng k thut (Eric S.Raymond, The Jargon

File, v3.0.0.0, July 1993,http://catb.org/~esr/jargon/),n nh ngha giao thc:

Mt tp cc quy tc chnh thc m t cch truyn d liu, c bit l qua mt mng.Cc giao thc cp thp xc nh cc tiu chun v in, v vt l c tin hnh theo kiu

bit v kiu byte, vic truyn, vic pht hin li v hiu chnh chui bit. Cc giao thc cpcao cp n nh dng d liu bao gm c php ca thng ip, on i thoi gia ucui ti my tnh, cc b k t, s sp xp th t ca thng ip, v.v

Vi nh ngha ny, cc giao din khng gian s l cc giao thc cp thp, cn cc giao

thc c m t di dy l cc giao thc cp cao. N xc nh c php ca thng ip vcu trc ca on i thoi gia reader v tag. Phn u xoay quanh mt s thut ng vkhi nim quan trng hiu c giao thc tag v gii thch nhiu hn v mi quan h giacc chun m vch v m ha tag, n s hu ch cho ngi pht trin xy dng cc ng dngEPC. Sau y ta tho lun mt s loi th tc chng ng v singulation minh hacch reader nhn dng tag trong mt cn phng cht.

Ban u giao thc singulation dng nh ch nhng ngi quan tm mi bit nhngchng c tp trung tranh lun si ni trong gn y v l nguyn nhn gy ra
http://catb.org/~esr/jargon/%29http://catb.org/~esr/jargon/%29http://catb.org/~esr/jargon/%29http://catb.org/~esr/jargon/%29


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nhng quyt nh then cht trong thi gian thng qua k thut RFID trong nhiu ngnh cngnghip. C th l s cng b c t Gen2 vo u nm 2005 l mt trong nhng s kin cth d on trc nht trong cng ngh RFID lc .

1. Thut ng v khi nim Singulation: Thut ng ny m t mt th tc gim mt nhm (group) thnh mt

lung (stream) qun l k tip nhau c. Chng hn mt ca xe in ngm l mt thitb gim mt nhm ngi thnh mt lung ngi m h thng c th m v yu cu xuttrnh th. Singulation cng tng t khi c s truyn thng vi cc tag RFID, v khng c cch no cho php tag tr litch bit, nhiu tag s p ng mt reader ng thi v c th

ph v vic truyn thng ny. Singulation cng c hm rng reader hc cc ID ca mi tag n kim k.

Anti-collision: Thut ng ny m t mt tp th tc ngn chn cc tag agkhc v khng cho php c thay i. Singulation nhn dng cc tag ring bit, ngc lianti-collision iu chnh thi gian p ng v tm cc phng thc sp xp ngu nhinnhng p ng ny reader c th hiu tng tag trong tnh trng qu ti ny.

Identity: Identity l mt ci tn, mt s hoc a ch m n ch duy nht mt vt hocmt ni no . Malaclyse the Elder l mt identity ch mt con ngi c th. 221bBaker Street London NW1 6XE, Great Britain l identity ch mt ni c th,urn:epc:id:sgtin:00012345.054322.4208 l identity ch mt widget.

2. Phng thc lu tr d liu trntagGiao thc truyn thng tag cp cao hiu c cc loi ID v phng thc lu tr d

liu trn tag. Tuy nhin v mt reader ch lin lc vi mt tag nn sp xp v mt vt l thct ca b nh trn tag ty thuc vo nh sn xut. Layout c cu trc logic nh sau:

Trong :

CRC l mt checksum EPC l ID ca tag. Password l mt m cht lm mt kh nng hot ng ca tag.Chun EPC phin bn 1.1 (hay 1.26) nh ngha EPC l m hnh meta-coding v n cho

php ID hin ti c m ha sang ID EPC hoc to ID mi hon ton. Chun ny nhngha m ha General ID (GID) dng to m hnh nhn dng mi v nm kiu m ha cth c gi l cc ID h thng cho nhng ng dng c th. Cc ID h thng da trn ccID GS1 hin ti (EAN.UCC).

Bng cc t nh danh ng dngpha di m t cc loi m ha ny v v d v ngdngca chng. ID ng dng l mt s lm tin t trong m vch phn bit ID.


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CCITT-CRC

CRC (Cyclic Redundancy Check) l mt phng php xc minh mt khi d liukhng thch hp do b sa i. Ngi gi khi d liu ny s tnh mt gi tr bng cchx l ton khi thnh mt s ln v chia n bi mt s c gi l a thc CRC. S d ca

php ton ny l CRC. Ngi gi s gi CRC ny cng vi d liu v ngi nhn dng

phng php tng t tnh CRC qua khi d liu so snh. Nu CRC t ngi gikhng tha vi CRC c tnh bi ngi nhn th ngi nhn yu cu d liu c gili. pht sinh CRC, cc giao thc EPC s dng a thc CCITT-CRC m n ging athc c s dng pht hin li trong hu ht cc a v trong cc giao thc truyn fileXMODEM. Giao thc ny dng chui 16 bit CRC s dng a thc x16+x12+x5+1. N c th

bt c 99.998% li.

Thut ton tnh CRC: u tin tnh gi tr hex cho a thc. Thc hin bng cch tnh t15 xung (v y l chui CRC 16 bit) v nh du 1 cho mi ly tha xut hin trong athc. i vi mi ly tha khng c trong a thc ta nh du 0. iu ny c ngha l ta c1 v tr 212 v 1 v tr 25. V a thc kt thc l 1, ta cng 1 vo cui s, s l mt s

0001000000100001 hoc s hex 1021(s ny l CCITT). Ly a thc khi d liu chia choa thc ny, s d l CRC.

cc t nh danh ng dng

nh danh ng dng nh danh Tn

(21) SGTINSerialized GlobalTrade Item Number

(00) SSCCSerial ShippingContainer Code

(414) GLN

Global Location

Number(8003) GRAI

Global ReturnableAsset Identifier

cho

(8004) GIAIGlobal IndividualAsset Identifier

GID General Identifier

GID nh ngha mt header, 3 trng: General Manager Number (GMN), Object Class,Serial Number. GMN c EPCglobal gn cho cng ty hoc thc th v n l duy nht.

Trng Object Class v trng Serial Number khng cn phi l duynht cho mt GeneralManager, cc General Manager khc nhau c th dng cng Object Class v Serial Number.

Lu identity c ngha nh m t trong phn . EPC nh ngha 3 lp nhndng: Lp nhn dng Pure(nguyn cht), lp Encoding(m ha), lpPhysical Realizationof an Encoding

. M ha l mt th tc phi hp nhn dng pure vimt thng tin c th c c php, nh gi tr lc hoc checksum, sau biu din thng tin


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ny theo dng c c php. Nhn dng pure c th c biu din theo dng m ha m vch,m ha tag RFID hoc mt EPC URI (Uniform Resource Identifier) c in ra mt t giy.

Physical realization of an encodingl mt php bin i ring ca m ha cho php lutr n dng m vch, ghi vo b nh ca tag hoc c thc hin qua mt vi cng nghkhc. Hnh sau cho mt v d minh ha v m ha mt nhn dng pure nh m vch hoctag EPC.

M ha mt nhn dng pure

Ch , GID m ha ch yu cho tag EPC. Nhng m ha khc (m ha m vch chnghn) nhn mt ID v chuyn n v mt dng c c php tng t vi GID:

Header.GeneralManagerNumber.ObjectClass.SerialNumber.

M ha GS1 SGTIN

Reader EPC v middleware RFID trnh by d liu tag theo m ha EPC. Vic giaotip vi reader hoc middleware t nht cn phi bit v m ha tag g ri m. Vic hiu

bit v m ha cng cn phixc nh cc s kin v cc b lc. SGTIN l v d c th vnhn dng v m ha.

EPC-SGTIN l m rng ca GS1 GTIN, dng nhn dng cc loi i tng. Mvch UPC 12 s v m vch EAN 13 s l tp con ca GTIN. GTIN khng c mt con sserial cho item v vy SGTIN thm vo mt s serial l gi tr c gn bi GeneralManager.

Hnh di ytrnh by mt m vch UPC tiu biu. chuyn n thnh EPC v lun vo mt tag RFID ta phi chuyn n v GTIN. M vch ny c mt s Indicator Digit(0), mt Company Prefix (12345), mt Item Reference (54322) v mt Check digit (7). chuyn n v GTIN ta ly ton b m thnh mt chui v thm 2 s 0 vo u chui thnhchui GTIN 00012345543227. Lu l Company Prefix tr thnh 00012345, l mt octet.Sau s chuyn GTIN thnh SGTIN cho php ta theo di tng item bng cch cng vo

mt s Serial Number (4208).


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M vch UPC

trnh by mt nhn dng pure, EPC s dng URI c biu din thnh k hiuURN. i vi SGTIN, k hiu ny l:

urn:epc:id:sgtin:CompanyPrefix.ItemReference.Seria lNumber

K hiu ny ch c thng tin phn bit item ny vi item khc ch khng c GTIN

check digit hoc gi tr lc. y Item Reference thc s l Indicator Digit cng vi ItemReference t GTIN. V d minh ha s c m ha nh sau:

urn:epc:id:sgtin:00012345.054322.4208

biu din mt nhn dng c m ha thnh SGTIN-96 l mt gi tr ph thucvo loi tag th EPC s dng mt nh dng khc cho URN:

urn:epc:tag:sgtin-96:FilterValue.CompanyPrefix.ItemReference.SerialNumber

Khi dng k hiu ny, v d s c m ha nh sau:

urn:epc:tag:sgtin-96:2.00012345.054322.4208

Cc bc m ha EPC 96 bit thnh chui nh phn nh sau:

Tm header ph hp cho loi nhn dng. Tra cu gi tr partition da vo chiu di ca Company Prefix. Rng buc cc trng header 8 bit, lc 3 bit v partition 3 bit. Gn vo Company Prefix v cc trng khc ph hp vi nhn dng (Item Reference

v Serial Number cho SGTIN)

Tnh CRC v thm EPC vo cui CRC.2.1Tm Header

Header nhn bit mi loi nhn dng v m ha ca n. gi tr header caSGTIN trnh by v d m ha SGTIN i vi cc th 96 bit v 64 bit. Lu header ca th64 bit ch c 2 bit.

gi tr header ca SGTINType HeaderSGTIN-96 0011 0000SGTIN-64 10


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2.2Tm partitionTa c 96 bit, i vi nhng bit ny m ha ch nh 44 cho Company Prefix v Item

Reference. Cc cng ty khc c chiu di Prefix khc nhau. S partition cho ta bit phngthc dng bao nhiu bit cho trng Item Reference da vo phng thc dng bao nhiu bitcho Company Prefix. bit phng thc dng bao nhiu bit cho Company Prefix xem

phn Company Prefix trongb -96 parti tion

. V d minh ha v CompanyPrefix 00012345 (chiu di 8 s) tng t vi partition 4 trong b -96partition. T nhng ct khc trong hng ny, ta s thy ta cn 27 bit m ha CompanyPrefix trn th v s c 17 bit m ha Item Reference.

g -96 partition

Partition Company Prefix Item ReferenceBits Digits Bits Digits

0 40 12 4 11 37 11 7 2

2 34 10 10 33 30 9 14 44 27 8 17 55 24 7 20 66 20 6 24 7

2.3Rng buc header, gi tr lc v partitionLu tn trng Filter Value. N khng phi l thnh phn ca SGTIN m n thay

th mt phng thc chn EPC nhanh da trn cc kiu chung. Chng hn gi tr filter 1 c

th s dng cho nhng item nh hn trong khi bng 3 cho nhng item ln c chuyn chring l nh mt t lnh chng hn.Bng cc gi tr fileter SGTIN lit k ccgi tr lcSGTIN. Ta s s dng gi tr lc 2 trong v d ch mt

Standard Trade Item Groupingnh mt pallet hoc carton (thng ng hng). Tt ccc m ha u h tr gi tr filter 0, SGTIN v SSCC cng h tr 1 ngha l khng xcnh. SSCC nh ngha 2 cho Logistical/Shipping Unit. Nhng gi tr filter thm na cth s c nh ngha trong tng lai.

Bng cc gi tr fileter SGTIN

Gi tr

(fileter)

0 0001 0012 010

3 011

4 100


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5 101 ho tng lai6 1107 111

Khi ta xy dng mt SGTIN-96 gi tr header chun l 00110000 hoc mt s hex 30.

Vic xy dng SGTIN-96 l mt vn n gin rng buc cc bit, bt u vi header lMSB (most significant bit) theo sau bi cc bit filter (3 bit) v partition (3 bit). Trng nynh sau (c trnh by tng chui 4 bit vi chui bit cui cha hon chnh): 0011 00000101 00

2.4Thm Company Prefix, Item Reference v Serial NumberTa thm Company Prefix vo cc bit u tin bng cch ch nh 27 bit dnh sn cho

n chng biu din gi tr ph hp. Trng ny nh sau:

0011 0000 0101 0000 0000 0000 0001 1000 0001 1100 1

m n c th c trnh by thnh dng s hex bng 305000181C vi bit m rng 1. Sau thm Item Reference 17 bit vo cui s, trng ny bng 305000181C B50Ccngthm 2 bit 10.

Ta li thm Serial Number 38 bit. Trng ny l mt con s 12 byte hoc 96 bit, nbng 305000181CB50C8000001070.

2.5Tnh CRC v thm EPC vo nGi tr ny c lu trn tag vi CRC 16 bit (CCITT-CRC), n s l FFF1 trong

trng hp ny. Gi tr ny khi c CRC s l FFF1305000181CB50C8000001070.

Hnh di ytrnh by nhng phn m ha cn li.

- 4

i vi mi ln nhn dng h thng s c c t m t mt m ha khc cho cc tag 64bit. lm cho nhn dng thnh mt m ha 64 bit, Company Prefix b xa v mtCompany Prefix Index thay th. Index ny l mt offset trong bng Company Prefix.Company Prefix Index c cung cp v GS1 cn nhng thc th , v chng c nh sdng cc tag 64 bit. Bng ny gii hn n 16,384 mc, v m hnh m ha ny nh mtgii php tm thi cho n khi cng nghip chp nhn cc tag 96 bit hoc ln hn na. Lu rng m ha SGTIN-64 c header duy nht cha bit 1 trong MSB cho php n ch c chiudi 2 s nh phn (11 c dnh ring cho cc m ha 64 bit khc).


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3. Th tc Singulation v Anti-CollisionCh k tip lin quan ti phng thc m mt reader v mt tag s dng giao din

khng gian (air interface). C nhiu phng thc khc nhau cho cc reader v tag lin lcvi nhau nhng tt c c th c phn loi thnh Tag Talks First (TTF) hoc Reader TalksFirst (RTF). n gin nht l mt tag trong mi trng thng bo s c mt ca n chonhng th c lin quan. Tuy nhin trong thc t, y l mt iu kh tr nhng tag c khnng dn xp, tag s ni trc. Mt s tag tch cc u trn s dng cc giao thc truynTTF nhng mt nhm mi l cc smart label v cc tag th ng s dng cc giao thcRTF. Trong phn ny, ta s nghin cu cc giao thc ph bin nht cho RFID: SlottedAloha, Adaptive Binary Tree, Slotted Terminal Adaptive Collection v c t EPC Gen2mi.

3.1Slotted AlohaSlotted Aloha xut pht t mt th tc n gin Aloha v c pht trin trong

nhng nm 1970 bi Norman Abramson ca Aloha Network ti Hawaii trong truyn vtuyn gi. Aloha l ngun cm hng cho giao thc Ethernet v s bin i ca th tcny vn c dng trong thng tin v tinh cng nh cho cc th RFID ISO 18000-6 Type Bv EPC Gen2.

i vi th tc ny, cc tag bt u broadcast (thng bo) ID ca chng ngay khireader np nng lng cho chng. Mi tag gi ID ca n v ch mt khong thi gianrandom (ngu nhin)trc khi broadcast li. Reader nhn cc ID, mi tag s broadcast trongkhong thi gian cc tag khc im lng. Du sao th reader cng khng tr li cc tag. uim ca th tc ny l tc v tnh n gin. Lun l ca tag rt nh v vi giao thc yunhth ny th tc c ch t cao nht khi ch c mt vi tag hin din.

Tuy nhin, cc tag thm vo lm gim c hi truyn. C ngha l ch cc tag truyn li

n khi truyn ht, n ph thuc vo khong cch truyn, v khng th thc thi theo di itemc khong 8 n 12 tag. Slotted Aloha ci tin giao thc bng cch thm vo khi nimsingulation v yu cu cc tag ch broadcast vo lc bt u mt khe thi gian no v thn lm gim ng mt cch ng k. V c kh nng c gn 1,000 tag trong mt giy.

Slotted Aloha s dng 3 lnh chn th: REQUEST, SELECT v READ. Lnh u tinl REQUEST cung cp mt nh du thi gian cho bt k tag no c trong dy. LnhREQUEST cng cho bit phng thc cc tag s dng cc khe c sn. Mi tag chn mttrong nhng khe , n da vo tng s ty chn ca reader, chng chn ngu nhin khongthi gian ch trc khi tr li lnh REQUEST. Sau cc tagbroadcast ID nhng khe chn. Khi nhn ID, reader pht lnh SELECT cha ID . Ch tag no c ID ny mi tr li.

Sau reader pht lnh READ. Sau reader pht li lnh REQUEST. Cc hnh bn di trnh by s bin i trng thi ca readerv bin i trng thi ca th.


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S trng thi ca Slotted Aloha reader

Cng t khe th vic c cng nhanh, cng nhiu khe th ng cng t. Reader c th

tng tng s khe nu REQUEST b ng v tip tc tng lnh REQUEST cho n khivic truyn ID khng cn ng na. Reader cng c th s dng mt lnh BREAK chobit cc tag ch i. Trong mt s trng hp, tag s vo trng thi SLEEP (cng c th gil DORMANT hoc MUTE) khi c thnh cng, v vy cho php cc tag cn li c nhiu chi c chn hn.

S trng thi th Slotted Aloha

V d sau y c th gip hiu r hn v giao thc Slotted Aloha. Ta c mt reader v3 tag s dng giao thc bao gm lnh BREAK v SLEEP. Hnh dung ra bn din vin: mtngi ng vai tr reader cn nhng ngi cn li l tag 1, tag 2 v tag 5.

Ta bt u trong mt phng trng. Mt ng h ln treo trn mt bc tng cho bitthi gian hin thi tnh bng mili giy. Reader ang c t bc v cc tag t ca lnvo, chng bn tri sn khu.

Reader: C ai y khng? By gi l thi gian t. Ti c cc khe thi gian t+10,t+20, t+30, t+40 v t+50. Xin vui lng tr li.(tag 1, 2 v 5 vo)Tag 1: chn t+40 (chn kiu tr chi sc sc) Tag 2: chn t+20Tag 5: chn t+10(ng h nh t+10)Tag 5: Five!


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Reader: im lng no! Do ti chn Five.(Tt c tag (tr tag 5) u lc u chn ngn vn im lng. Tag 5 ci toe tot)Tag 5: Ti y! Ti l Five!

Reader: Bn c d liu no chia s khng, Five?Tag 5: FFF1305000181CB50C8000001070, ti l Five!

Reader: Vng, cn gi th anh im lng nh Five. Cn ai na khng? By gi l thigian t. Ti c cc khe thi gian t+10, t+20, t+30, t+40 v t+50. Xin vui lng tr li.Tag 5 ngi im lng v tag 1 v tag 2 ang chn. Reader c th cho bit kt thc ca mt khe

bng mt tn hiu c gi l slot marker. Giao thc chng ng s dng cc tn hiuny c gi l cc giao thc Slot Marker. Slot Marker ca giao thc Slotted Aloha cnglm vic nh m t trn, ngoi tr kt thc ca mt khe c cho bit bi mt tn hiuch khng phi bi s kt thc ca mt thi gian thit lp. iu ny cho php mt s khedi hn cc khe khc v nh th c nhiu c hi c mi khe hn.

3.2Adaptive Binary Tree (Cy nh phn thch ng)Cc tag UHF EPC lp 0 v lp 1 phin bn 1.0 (Generation 1) s dng mt cch tipcn phc tp hn cho singulation v chng ng l th tc Adaptive Binary Tree. Th tc

ny s dng tm kim nh phn tm mt tag trong nhiu tag. Ta quen thuc vi cy nhphn nhng hiu r ta s xem li nhng khi nim c bn. Sau ta s gii thch mt ssc thi tm kim nh phn s dng cch tip cn query/response ( hi/p) tng t nh

phn Slotted Aloha. Khng ging vi Slotted Aloha, cc tag s dng giao thc ny s tr lingay tc th. c t EPC i vi giao din khng gian ca cc tag UHF s s dng 2

ring cho bit 1 v bit 0 trong p ng tag. Bi v giao thc ny khng ch nphng thc p ng nhiu tag vi bit 1 hoc bit 0 m ch ch n mt tag c p nghoc hn na. Giao thc ny khng yu cu ch mt reader m n c th yu cu cu hnh

cn thn cc reader gn nhau.Mt phng thc d dng l on tng s. Khi ta bt u ta khng c thng tin, v th

ta hi S u tin l 1 phi khng?. Nu tr li vng th ta c th thm 1 vo chui s vhi S k tip l 1 phi khng?. Nu tr li khng th ta c th thm 0 vo chui s. Cuhi v cu tr li lp li cho tng s cho n khi ta bit ht ton b s. Hnh ditrnh bycy. Cc mi tn trnh by cc s chnh xc mi bc.

By gi p dng chin lc ny tm mt tag trong nhiu tagbng nhng bit trong IDca tag. Nh ni l ta bt u khng c thng tin. Reader gi mt cu truy vn C tag


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no c bit u (MSB) l 1 khng?. Tt c tr li khng th dng p ng, cn nhng tagtr li c th c hi cu hi tng t cho bit k tip. Vi cch ny, cc tag tip tc b thuhp dn cho n khi ch cn mt tag tr li. Bng phng thc ny reader c th thu hp vmt tag m khng i ht ton ID, mc d trong trng hp xu nht th c th tm kim IDtun t s cn i n bit cui cng (LSB).

Vi giao thc Adaptive Binary Tree, s tng tc gia reader v tag gp nhiu phctp hn so vi Slotted Aloha. Giao thc ny s dng c ch trng thi hnh thnh bn phn

ph thuc ln nhau. Th nht l tp cc trng thi c kt hp vi cc lnh ton cc (globalcommand) bao gm trng thi Dormant. Phn tip theo l trng thi lin lc ng c(calibration) ngha l ng b my to dao ng thi gian tag vi thi gian ca reader. Skhc nhau trong ch to, tui th ca cc thnh phn v ngay c nhit c th nh hngn vic tnh thi gian m vic canh ng c ny l then cht t c tc c hp l.

3.2.1 Cc trng thi GlobalSau y l cc trng thi ton cc c th c vo bt k im no:

Dormant(khng hot ng): Trng thi khng hot ngl trng thi khi to ca tagkhi n c np nng lng. N cng l trng thi ca tag sau khi c c. Global Command Start (Bt u lnh ton cc):Sau khi nh c thnh cng, tag

trng thi Global Command Start v ch bit 1 hoc bit 0 t reader. Bit 1 gi th tag vo trngthi Global Command cn bit 0 gi th tag vo trng thi Tree Traversal (tr khi tag cc ri, trong trnghp ny 0 lm cho tag vo trng thi Dormant).

Global Command (Lnh ton cc):Trong trng thi ny, tag sn sng nhn v x llnh nh hng n tt c tag hoc nhm tag khng c singulate. C mt s lnh nh lnhkill khng th dng nh lnh ton cc.

Calibration (Hiu chnh):Mi khi mt tag nhn mt thng ip reset t reader gith n s vo trng thi Calibration, ch my to dao ng v cc xung nh c d liu treader. Nu khng hp l, tag s tr v trng thi Dormant.


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S trng thi giao thc Adaptive Binary Tree

3.2.2 Cc trng thi Tree walkingCc trng thi sau y xy ra khi giao thc qua cy nh phn:

Tree Start:Trong trng thi ny, d liu null s tng b m null bng1. Nu l 0 thtag trng thi Tree Traversal. Nu l 1 th tag trng thi Traversal Mute tr khi b mnull l 2, trng hp ny th tag s vo trng thi Global Command.Kiu null ny nhm vonhng nhm ) vi mt chui singulation cc b.

Tree Traversal:Khi tag trng thi ny th n gi ngay bit u tin (MSB) ca n.Sau reader vi bit m tag gi thtag s gi bit kt th tag vo trng thi Traversal Mute v ch mt d liunull. Nu singulation ang s dng ID gi to (pseudo) th c mi bit th 10 c xem lbit bin. Nu singulation ang s dng EPC th bit bin l bit cui cng ca EPC cng viCRC. bit bin, tag gi bit nh thng thng, nu reader xc nhn tag ny th tag s gi bittng t li trong trng hp EPC hoc bit k tip trong trng hp ID gi to. Nu readerp ng vi bit 1 hoc bit 0 th tag s vo trng thi Traversal Mute. Nu p ng t readerl d liu null th tag vo trng thi Singulated Command Start. Nu tag nhn d liu nullvo mt lc no khc th tag svo trng thi Traversal Mute.

Traversal Mute:tag ch mt cch im lng trong trng thi ny cho n khi n nhnc d liu null, ti im m n bt u vo trng thi Tree Start v reset b m null cc

b.


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3.2.3 Cc trng thi SingulatedCc trng thi ny xy ra khi mt tag vn trng thi c sau khi cy nh phn c

i qua.

Singulated Command Start:tag i vo trng thi ny t trng thi Tree Traversal saukhi bit cui cng ca ID c xc nhn v n nhn mt gi tr null t reader. Bt k gi tr

null thm vo u b t chi, trong khi gi 1 cho tag th tag s trng thi SingulatedCommand. Gi tr 0 s t mt c nhn dng v tag s vo trng thi Dormant. C nhndng ny cho bit tag c c.

Singulated Command:Ngay ti y tag nhn cc lnh 8 bit t reader. Nu c mt lixy ra, tag s trng thi Singulated Command Mute. trng thi ny tag s ch i chon khi n nhn c d liu null (data null) th n s trng thi Singulated CommandStart.

3.3Slotted Terminal Adaptive Collection (STAC)Giao thc STAC tng t v nhiu mt vi Slotted Aloha, nhng c mt s c im

lm cho n phc tp hn v phi c cch gii quyt ring. STAC c xc nh l mt thnhphn ca c t EPC i vi cc tag HF. Bi v n xc nh n 512 khe c chiu di khcnhau, c bit l n ph hp vi singulation vi mt tag dy c. Giao thc ny cng cho

php chn cc nhm tag da trn chiu di ca m EPC bt u bng MSB. Bi v m EPCc t chc bi Header, Domain Manager Number, Object Class v Serial Number tMSB n LSB, c ch ny c th d dng chn nhng tag ch thuc v mt DomainManager hoc Object Class no . V cc tag HF thng c dng xc thc item ring lnn iu ny rt hu dng chng hn nh nu ng dng mun bit c bao nhiu item trnmt pallet hn hp l nhng thng giy A4.

Cng nh Slotted Aloha, STAC cng s dng cc khe. Hnh di minh ha phngthc s dng cc khe.

Khe STAC

Khe F (hoc c nh) lun lun tn ti v lun c chiu di khng i. Theo sau l cc khe c chiu di thay i v c nh s. Cc khe ny phi bt u bng mt kh e0 v phi c cc khe bng ly tha no ca 2. S khe chnh xc c reader chn v

c iu chnh lin tc cn bng gia nhu cu c nhanh v mt vi s ng . Cng tkhe hn th vic c nhanh hn nhng nhiu khe hn th s lm cho ng t hn.

STAC ch nh ngha mt tp nh cc trng thi v cc lnh nhng cc bc trong giaothc i hi phi c mt s gii thch. Hnh di ytrnh by cc trng thi v cc lnh gyra s chuyn i.


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Ch d tag ang trng thi no n cng s tr v trng thi Unpowered (khngc cung cp lc) nu n di chuyn ra khi phm vi ca reader (Trng hp ngoi l canguyn tc ny l tag trng thi Destroyed c ngha l tagb mt kh nng hot ng vnhvin v khng th c c hoc s dng li c). Mt s bin i trn giao thc ny cho

php cc tag nh c chng trng thi Fixed Slot trong mt khong thi gian d lnng lng b mt. Trong s bin i ny, mt lnh Complete Reset cho php reader pcc tag vo trng thi Ready khi cn thit cho d tag c nh ra n trc n trng thi

Fixed Slot. Vic ny c th xy ra trong trng hp mt tag di chuyn di bng ti gia ccreader. Tc l reader u tin c tag, tag tin trng thi ca n phi l Fixed Slot. Tuynhin reader mi li cha nhn thy tag ny v s bt tag vo trng thi Ready khi c npnng lng, do reader mi ny pht lnh Complete Reset.

Danh sch di y m t tng trng thi STAC kt hp vi singulation cng th mtrng thi Destroyed. Trng thi Write (c trong cc tag HF EPC lp 0 hin hnh m ID EPCch c t bi nh sn xut) khng c trnh by. Sau y l cc trng thi:

Unpowered:Khi tag ngoi phm vi ca reader, tag trng thi Unpowered. Cho nkhi vo phm vi ca reader th tag mi vo trng thi Ready.

Ready: trng thi ny tagphi ch lnh Destroy, Write hoc Begin Round. Nu tagnhn lnh Begin Round c hoc khng c s la chn chiu di bng vi EPC ca tag th tagu vo trng thi Slotted Read.

Slotted Read:Trong trng thi ny tag s chn mt khe ngu nhin do reader a ra.Khe ny c th l bt k khe no ngoi tr khe F. Nu tag nhn lnh Fix Slot sau khi githng tin ca n th n s i vo trng thi Fixed Slot. Nu lnh Fix Slot, Close Slot hocBegin Round c thm la chn so khp th tag vn trng thi Slotted Read. Nu lnhBegin Round c thm la chn khng so khp th tag s tr v trng thi Ready.

Fixed Slot:Khi tag ang trng thi Fixed Slot n s p ng trn khe Fv s tip tclm nh th i vi nhng p ng sau cho n khi nng lng b mt (tc l thot rakhi phm vi ca reader)

Destroyed:Nu tag nhn c lnh Destroyed v password trong lnh ny khp vipassword trong tag th tag s gi ID ca n v ngng hot ng vnh vin. Mi khi b lmmt hiu lc th tag c th khng cn s dng c na.


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3.4EPC UHF lp 1 Gen 2Vic nghin cu mi y v giao din trung gian EPC UHF lp 1 c gi l Giao

thc Gen2. Gen2 phn tch mt s gii hn ca giao thc UHF u tin bng cch nhngha cc s bin i giao thc m n c th lm vic theo quy tc RF ca Chu u (CEPT)v Bc M (FCC).

Giao thc EPC Gen 2 h tr singulation tag nhanh hn giao thc trc, tc c l1600 tag trn giy Bc M v 600tag trn giy Chu u. iu then cht ca Gen2 lcc tn hiu reader pht ra c mt khong cch xa. Nu 2 reader cch nhau 1 km th vnxem chng cng mi trng hot ng.

Giao thc m t 3 th tc truyn gia reader vi th. Reader chn cc tag bng cch sosnh tag vi mt bitmask, hoc kim tagbng cch singulate tag, hoc truy cp tag cthng tin, ghi thng tin, lm mt kh nng hot ng hoc ci t trng thi kha bngmemory bank number.

3.4.1 B nh tagGiao thc Gen2 cho php thm user memory (b nh ngi dng)v Tag Identifier

(TID) vo CRC+EPC m n c gi l Object Identifier (OID). B nh tag gm nhiuphn, mi phn c t chc thnh mt addressable bank (bank a ch) (xem bng ccmemory bank ca th), cc lnh c v ghi ly bank address xc nh xem thao tc tcng vo bank no.

Mi th phi c access password, m kill. Tuy nhin c th l mt gi tr zero. Lnhchn bankch hot ng trong bank . chuyn bank, reader phi pht lnh mi.

Bng cc memory bank ca th

Bank00 password, kill code, bit protocol ...01 OID (CRC+EPC)10 TID serial number ISO 1569311

3.4.2 Lnh kim tagKhi reader bt u kim mt nhm tag l lc bt u mt session (phin giao dch).

Trong mt phin, mi tag ch lin lc vi mt reader nhng c th time-slice n 4 session

lm cho mt tag c th lin lc vi 4 reader mt lc. Tag gi 4 c: S0, S1, S2 v S3. C c 1trong 2 gi tr: A hoc B.

Reader lm vic phin zero khng th thy gi tr ca c ca 3 phin kia nhng nuc mt reader thay i gi tr trn mt s tag hoc kha OID bank th tt c cc phin u bnhhng.

Trong qu trnh kim reader dng phng php Slotted Random Anticollision. Ndng cc khe xc nh thi im tag s p ng reader, tag chn khe bng cch ci mt


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b m khe vi s ngu nhin 16 bit gim n khi bng zero. Khi khe ca tagbng zero, ns gi s ngu nhin 16 bit mi cho reader. Reader dng s ny che cc khi khi lin lcvi tag, do vic lin lc gia reader vi tag c mt m. Cc lnh kim:

Query:Reader bt u kim t lnh Query, n ch nh phin v tng s khe. Tag phts ngu nhin v dng chng xc nh khe no s p ng. Tag chn khe zero vo trngthi Reply, nhng tag khe khc vn trng thi Arbitrate.

Query Adjust:thay i tng s khe trong mt chu k kim tag. N cng c th thm,bt mt khe trong tng s khe hoc gi nguyn. Tagpht sinh s ngu nhin v chn khengu nhin t phm vi mi ny. Tag chn khe zero vo trng thi Reply, tag chn cc khekhc vn trng thi Arbitrate.

QueryRep:khi reader pht QueryRep, tag gim b m khe i mt. Nu b m vzero tag s vo trng thi Reply, nu khng tag vn trng thi Arbitrate.

ACK:Reader p ng tag bng ACK, gi gi tr 16 bit n tag. NAK:Reader pht NAK chiu di 8 bit c gi tr 0xCO. Khi tag nhn NAK, n chuyn

v trng thi Arbitrate tr khi n trng thi Kill hoc Ready th tag s l i NAK.

3.4.3 Lnh SelectReader c th khng kim tt c cc tag, lnh Select yu cu tag so snh ni dung ca

mt bank b nh no vi bitmask. Nu bitmask hp vi b nh ca tag th tag t c SL(selected flag) bng true hoc c inventoried flag (S0/S1/S2/S3) bng mt gi tr do lnhSelect ch nh. Mi Select cth t mt trong hai gi tr: c select hoc c inventoried.

3.4.4 Lnh accessLnh access cho php reader i ni dung b nh ca tag, c b nh, kha bank b

nh, kill tag hoc yu cu tagpht s ngu nhin 16 bit. Reader phi nhn dng tag dngmt trong nhng lnh access. Lnh access truyn d liu: password, ID t reader cho tagdi dng mt m (ciphertext) s dng mt cover code (nh bitmask). Chun Gen2 i hic tag v reader phi h tr cc lnh access sau y:

Req_RN:yu cu mt s ngu nhin do tag pht. Read:c d liu t mt bank b nh ca tag. Write:ghi d liu vo mt bank b nh ca tag. Reader pht lnh Req_RN trc mi

ln ghi. Tag p ng bng mt s ngu nhin 16 bit, sau reader dng cover code bov d liu 16 bit c gitrong lnh Write. i vi chui d liu di hn th Req_RN-Write

c lp li nhiu ln. Kill:lm mt kh nng hot ng ca tag. Lnh ny ging lnh Write l u tin reader

yu cu tagpht mt s ngu nhin 16 bit, n dng cover code cho 16 bit u tin ca killpassword. Vic ny li c lp li i vi 16 bit th hai. Khi lnh ny hon tt tag s khngbao gi p ng lnh no khc. Tuy nhin, nu kill password ca tagbng zero th tag khngb kill v s l i lnh ny.


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Lock:t quyn c/ghi chocc bank b nh hoc cc password c th. y c th lpermalock (kha c nh), khng th thay i quyn li c.

Access(optional): nu tag c password khc 0 th reader c th dng lnh Access ttag trng thi Open sang trng thi Secured. Nu tag Secured th n vn Secured. Dolnh c cha password nn n c pht hai ln c cover code ngha l reader pht lnhReq_RN, cung cp cover code, dng n cho na u ca password v lp li vic ny chona cui ca password.

BlockWrite(optional): ging lnh Write nhng c th ghi nhiu khi 16 bit mt lnm khng c cover code. V vy lnh ny khng cn lp li tng khi, cng khng cn nlnh Req_RN trc.

BlockErase (optional): cho php reader xa nhiu khi t mt bank b nh ca tag.Lnh ny c bo v bng CRC-16.

3.4.5 Trng thi tagReady:tag ch khi hin ti n khng c kim k.

Arbitrate:tag ch khi n l mt phn ca bng kim k.Reply: tag trng thi Reply n s pht s ngu nhin 16 bit gi cho reader. Nu n

nhn li ACK th n vo trng thi Acknowledged, nu khng n s tr v trng thiArbitrate

Acknowledged:tag i vo bt k trng thi no ngoi tr Killed.

Open: tag c nonzero password s vo trng thi ny khi n trng thiAcknowledged v nhn lnh Req_RN t reader. Tag c th i vo bt k trng thi nongoi tr Acknowledged.

Secured:tag c password zero s vo trng thi ny khi n nhn Req_RN khi ang trng thi Acknowledged, tag c nonzero password s vo trng thi ny t trng thi Openkhi n nhn lnh Access. Tag c th vo bt k trng thi no ngoi tr Open hocAcknowledged.

Killed:khi tag vo trng thi Killed, n s gi p ng thnh cng cho reader, sau n mt kh nng hot ng vnh vin, n s khng bao gi p ng lnh no t reader cna.

4. Cch khc phc s c communication tagTrong trng hp reader mt lin lc vi tag ta c th hi l do reader hay tag.

Th tag vi reader , nu tag mi lm vic c th tag kia hng, nu tag mi khnglm vic c th reader hng (hoc trong trng hp hai tag u hng th tt nht l th vitag cho chc). Reader dng mt anten hoc nhiu hn na lin lc vi tag. Ta c th ianten vi reader khc khng? Ta nn cn thn, ch i anten t nhng reader y nh nhau.Hu ht reader h tr nhiu loi tag: tag ISO, tag EPC, HF hay UHF. Cn tag th c th lmvic vi hp kim loi hay v cao su.

B quyt n gin kim tra l di chuyn tag xung quanh v xem nh sng c sng haytt. du tag th ta ch vic t mnh gia tag v reader


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CHNG 3)

Reader RFID c gi l vt tra hi (interrogator), l mt thit b c v ghi d liu lntag RFID tng thch. Hot ng ghi d liu ln tag bng reader c gi l to tag. Qutrnh to tag v kt hp tag vi mt i tng c gi l a tag vo hot ng(commissioning the tag). Decommissioning tag c ngha l tch tag ra khi i tng cgn tag v ty lm mt hiu lc hot ng ca tag. Thi gian m reader c th pht nnglng RF c tag c gi l chu k lm vic ca re ader.

Reader l h thn kinh trung ng ca ton h thng phn cng RFID thit lp victruyn vi thnh phn ny v iu khin n, l thao tc quan trng nht ca bt k thc thno mun lin kt vi thc th phn cng ny.

Tag th ng (passive tag) c kch thch ngun nng lng bng qu trnh truynsng radio v b phn thu s lng nghe qu trnh truyn ny. Cc tag tch cc cng cn cgiao tip vi b phn thu c gn vo h thng. Trong quy trnh RFID, im cui ca thit

b truyn/h thng cgi l b c (reader). Reader c t gia tag v b lc s kin(event filter) trong mt h thng RFID. Reader ng vai tr giao tip vi tag, to ra cc skin mc nng lng thp tqu trnh c v gi nhng s kin ny n b lc s kin.

I - Cc thnh phn vt l ca mt Reader RFIDMt reader c cc thnh phn chnh sau:

1. My pht (Transmitter).2. My thu (Receiver).3. Vi mch (Microprocessor).4. B nh.5. Knh vo/ra i vi cc cmbin, c cu chp hnh, bng tn hiu in bo

bn ngoi (mc d y l nhng thnh phn khng bt buc, chng hu nh lunc cung cp vi mt reader thng mi).

6. Mch iu khin (c th n c t bn ngoi).7. Mch truyn thng.8.Ngun nng lng.

Hnh 4-1trnh by mt reader minh ha c cc thnh phn ny.


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4-

1. My phtMy pht ca reader truyn ngun AC v chu k xung ng h qua anten ca n n

tag trong phm vi c cho php. y l mt phn ca my thu pht, thnh phn chu trchnhim gi tn hiu ca reader n mi trng xung quanh v nhn li p ng ca tag quaanten ca reader. Anten ca reader c kt ni vi thnh phn thupht ca n. Anten careader c th c gn vi mi cng anten. Hin ti th mt s reader c th h tr n 4cng anten.

2. My thuThnh phn ny cng l mt phn ca my thu pht. N nhn tn hiu tng t t tag

qua anten ca reader. Sau n gi nhng tn hiu ny cho vi mch ca reader, ti ni nyn c chuyn thnh tn hiu s tng ng (c ngha l d liu m tag truyn choreader cbiu din dng s).

3. Vi mchThnh phn ny chu trch nhim cung cp giao thc cho reader n truyn thng vi

tag tng thch vi n. N thc hin vic gii m v kim tra li tn hiu tng t nhn tmy thu. Thm na l vi mch c th cha lun l thc hin vic lc v x l d liu cc t tag.

4. B nhB nh dng lu tr d liu nh cc tham s cu hnh reader v mt bn k khai cc

ln c tag. V vy nu vic kt ni gia reader v h thng mch iu khin/phn mm bhng th tt c d liu tag c c khng b mt. Tuy nhin, dung lng ca b nhsgii hn s lng tag c c trong mt khong thi gian. Nu trong qu trnh c m vickt ni b hngth mt phn d liu lusb mt (c ngha l b ghi bi cc tag khcc c sau ).


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5. Cc knh nhp/xut ca cc cm bin, c cu chp hnh v bng tn hiuin bo bn ngoi

Cc reader khng cn bt sut. Cc tag c th ch xut hin lc no v ri khireader mi mi cho nn vic bt reader sut s gy lng ph nng lng. Thm na l giihn va cp trn cng nh hng n chu k lm vic ca reader. Thnh phn ny cungcp mt c ch bt v tt reader ty thuc vo cc s kin bn ngoi. C mt s loi cm

bin nh cm bin v nh sng hoc chuyn ng pht hin cc i tng c gn tagtrong phm vi c ca reader. Cm bin ny cho php reader bt ln c tag.Thnh phncm bin ny cng cho php reader xut tn hiu iu khincc b ty thuc vo mt siu kin qua mt bng tn hiu in bo (chnghn bo bng m thanh) hoc c cu chphnh (v dm hoc ng van an ton, di chuyn mt cnh tay robot, v.v).

6. Mch iu khinMch iu khin l mt thc th cho php thnh phn bn ngoi l con ngi hoc

chng trnh my tnh giao tip, iu khin cc chc nng ca reader, iu khin bng tnhiu in bo v c cu chp hnh kt hp vi reader ny. Thng th cc nh sn xut hpnht thnh phn ny vo reader (nh phn mm h thng (firmware) chng hn). Tuy nhin,c th ng gi n thnh mt thnh phn phn cng/phn mm ring phi mua chung vireader.

7. Giao din truyn thngThnh phn giao din truyn thng cung cp cc lnh truyn n reader, n cho php

tng tc vi cc thnh phnbn ngoi qua mch iu khin, truyn d liu ca n, nhnlnh v gi li p ng. Thnh phn giao din ny cng c th xem l mt phn ca mchiu khin hoc l phng tin truyn gia mch iu khin v cc thc th bn ngoi. Thcth ny c nhng c im quan trng cn xem n nh mt thnh phn c lp. Reader cth c mt giao din tun t. Giao din tun t l loi giao din ph bin nht nhng ccreader th h sau s c pht trin giao din mng thnh mt tnh nng chun. Cc reader

phc tp c cc tnh nng nh t pht hin bng chng trnh ng dng, c gn cc Webserver cho php reader nhn lnh v trnh by kt qu dng mt trnh duyt Web chunv.v

8. Ngun nng lngThnh phn ny cung cp ngun nng lng cho cc thnh phn ca reader. Ngun

nng lng c cung cp cho cc thnh phn ny quamt dy dn in c kt ni vimt ng ra bn ngoi thch hp.

II - Cc thnh phn logic reader RFIDPhn iu khin reader RFID, chng ta c th hnh dung 4 thnh phn ring bit chu

trch nhim khc nhau. Hnh 4-2ch cc thnh phn logic ca mt b c.


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Hnh 4-2 Cc thnh phn logic ca mt reader

1. Reader API(API) cho php cc ng dng

khc yu cu kim tra tag,kim sot tnh trng ca reader hoc kim sot thit lp cuhnh nh mc nng lng, thi gian hin hnh. Thnh phn ny cp n vic to ra mu

tin gi n h thng RFID vphn tch mu tin nhn t h thng. API c th ng bhoc khng ng b.

2. (Communication)H thng giao tip s iu khin vic ca bt c giao thc reader no

dng giao tip vi phn mm trung gian (middleware). y l b phn c th thc thiBluetooth, Ethernet hoc cc giao thc c nhn cho qu trnh nhn v gi tin n API.

3. Qun l s kinKhi reader nhn ra tag ta gi l gi

n cc ng dng bn ngoi ca h thng. Vi reader thng minh, chng ta c th ng dngvo cc x l phc tp mc ny to ra lu thng h thng. V bn cht mt vi phnthit b qun l s kin ca middleware t di chuyn v kt hp vi thnh phn qun l skin ca reader.

4. (antenna subsystem)Anten ph bao gm giao din v logic gip reader RFID giao tip vi tag RFID v iu

khin cc anten vt l.

III - Phn loi READER1. Phn loi theo giao din ca Reader

Cng nh tag, reader cng c th c phn loi bng hai tiu chun khc nhau. Tiuchun u tin l giao din m reader cung cp cho vic truyn thng. Trong tiu chun ny,reader c th c phn loi ra nh sau:


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Serial

Network

1.1Serial reader (Reader ni tip)Serial reader s dng linkt ni tip truyn trong mt ng dng. Reader kt ni

n cng ni tipca my tnh dng kt ni RS-232 hoc RS-485. C hai loi kt ni nyu c gii hn v chiu di cp s dng kt ni reader vi my tnh. RS -485 cho php cpdi hn RS-232.

u im ca serial reader l c tin cy hn network reader. V vy s dng readerloi ny c khuyn khch nhm lm ti thiu s ph thuc vo mt knh truyn.

Nhc im ca serial reader l ph thuc vo chiu di ti a ca cp s dng ktni mt reader vi mt my tnh. Thm na l thng th trn mt my ch th s cng nitipb hn ch, c th phi cn nhiu my ch (nhiu hn s my ch i vi cc networkreader) kt ni tt c cc serial reader. Mt vn na l vic bo dng nu phnmmh thng cn c cp nht chng hn, nhn vin bo dng phi x l mi reader. Tc

truyn d liu ni tipthng thp hn tc truyn d liu mng. Nhng nhn t ny dnn chi ph bo dng cao hn v thi gian cht ng k.

1.2Network reader (Reader h thng). Thc t,

reader hot ng nh thit b mng. Tuy nhin, chc nng gim st SNMP (Simple NetworkManagement Protocol) ch sn c i vi mt vi loi network reader. V vy, a s readerloi ny khng th c gim st nh cc thit b mng chun.

u im ca network reader l khng ph thuc vo chiu di ti a ca cp kt ni

reader vi my tnh. S dng t my ch hn so vi serial reader. Thm na l phn mm hthng ca reader c th c cp nht t xa qua mng. Do c th gim nh khu bodng v chi ph s hu h thng RFID loi ny s thp hn.

Nhc im ca network reader l vic truyn khng ng tin cy bng serial reader.Khi vic truyn b rt, chng trnh ph tr khng th c x l. V vy h thng RFID cth ngng li hon ton. Ni chung, reader c b nh trong lu tr cc ln c tag. Chcnng ny c th lm cho vic cht mng trong thi gian ngn hn mt t.

2. Phn loi da trn tnh chuyn ng ca ReaderVic phn loi th hai da trn tnh chuyn ng ca reader.

C nh mt ch (stationary) Cm tay (hand-held)

2.1Reader c nhLoi ny c lp trn tng, trn cng hoc vi ni thch hp nm trong phm vi c.

Nhng ni lp t l ch c nh. Chng hn, c mt s reader c nh c gn trn thangmy, hoc bn trong xe ch hng. Tri ngc vi tag, reader khng chu c mi trng


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khc nghit. V vy, nu t reader ngoi ca hoc nhng i tng chuyn ng, phign ng cch. Reader c nh thng cn anten bn ngoi c tag. Reader c th cungcp n 4 cng anten bn ngoi.

Chi ph cho reader c nh thng t hn reader cm tay. Reader c nh l loi phbin nht hin nay. Hnh 4-3v 4-4trnh by mt s reader c nh.

Hnh 4-3Reader mng c nh UHF ca Alien Technology

Hnh 4-4 Reader mng c dy/khng dy (802.11b) UHF thp (303.8MHz) ca RFCode, Inc

Loi reader c nh c gi l my in RFID c th in mt m vch v to mt tagRFID trn smart label (th thng minh) trong qu trnh hp nht. Smart label bao gm mtnhn m vch c mt tag RFID c gn vo n. Cc loi thng tin khc nh a ch ngigi, ngi nhn, thng tin sn phm v ch cng c th c in ln trn nhn. My in RFIDc tag smart label c ghi xc nhn qu trnh ghi l hp l. Nu vic xc nhn nytht bi th my in loi b smart label c in. Thit b ny trnh tnh trng to mt tag

RFID m ni m vch ang c s dng. Ngy nay, mt cng ty ang s dng m vchc th s dng my in RFID nh bc u chp nhn k thut RFID. Thng tin m vchcung cp mt nhn dng human-readable v i tng c gn tag. Cc h thng hin ticng c th tip tc s dng d liu m vch nh th vi mt s thay i hoc khng thayi. Phm vi ca nhn c th cung cp ID tag c gn vo n hnh thc human-readable.Tag RFID c th cung cp kh nng object-level Auto-ID (t ng xc nh mc i tng)v nhng li ch khc. Hnh 4-5 trnh by minh ha smart label. Hnh 4-6trnh by minhha my in RFID.


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Hnh 4-5RFID smart label ca Zebra Technologies

Hnh 4-6My in RFID ca Zebra Technologies

Reader c nh c th hot ng hai ch sau y:

T tr (antonomous) Tng tc (interactive)(Xem thm ph lc)

2.2Reader cm tayReader cm tay l dng reader di ng, thng c anten bn trong. Mc d nhng

reader ny t nht (v t c) nhng nhng ci tin hin nay trong k thut reader cho phpcc reader cm tay phc tp c gi thp hn. Hnh 4-7trnh by mt reader cm tay.


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Hnh 4-7Reader cm tay UHF ca Intermec Corporation

IV - Cch b tr (layout) reader v anten1. Cng ra vo (Portals)

. H thng nythng c lp t nh kho, ni m sn phm thng xut nhp kho. H thng RFID nycn rt hu ch cho nhng sn phm thng di chuyn gia cc khu vc ca nh my ti sn phm mang tag thng di chuyn qua cc ca. H thng RFID ny cn c dng chocc ng dng lu ng, b c v anten thng c xy dng trong cc khung, trn bnhxe chng ta c th y vo trong xe ti hoc xung cc li i. Hnh 4-8 m t mt kiuRFID cho ca ra vo.

Hnh 4-8

2. Tunnel (ng hm)Tunnel l mt hng ro nm bn trn dy chuyn sn xut ti lp vo anten v

reader. Mt tunnel ging nh mt ca ra vo kiu nh c thun li l mt tunnel cng baogm phn chn RF hp th bc x hoc nh hng nng lng RF sai gy cn tr choreader v anten gn . ng dng ny thch hp cho cc dy chuyn lp rp v dy chuynng gi, reader s xc nh nhngsn phm di chuyn trn bng ti. Hnh 4-9m t mtng hm bn trn bng ti.


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Hnh 4-9Mt tunnel

3. Thit b cm tay (Handhelds)Mt thit b cm tay c sn anten, b iu khin cho php ngi dng qut cc sn

phm gn tag trong cc trng hp khng th di chuyn sn phm ti reader. Vic dng

reader RFID cm tay tng t nh reader bar code cm tay. Do , nhiu reader RFID cmtay cng c th c bar code v sn xut t cng nh sn xut ch to ra cc reader bar code.Reader ny cn c th giao tip bng Ethernet khng dy, modem RF. Reader bng tay nyc th kt ni vi cng bn phm hoc cng USB trn my tnh c nhn. Hnh 4-10m tmt b c cm tay.

Hnh 4-10B c RFID cm tay

4. K thng minhK thng minh l nhng k kt hp vi nhng anten reader nhn ra vic xut hinv ly i cc sn phn t k, hoc c tt c sn phm t k theo yu cu. Kh nng ny cho

php kim k tt c cc sn phm trong kho theo thi gian. H thng khng ch m lngsn phm trong kho m cn qun l nhng thng tin d liu ID ca sn phm v d nh thihn s dng v bo cho ngi qun l v cc sn phm ht hn. Hnh 4-11 m t mtthit k v k thng minh.


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Hnh 4-11H thng k thng minh

V -Reader truyn thng vi tag thng qua anten ca reader, l mt thit b ring m n

c gn vo reader ti mt trong nhng cng anten ca n bng cp. Chiu di cp thnggii hn trong khong 6-25 feet. Tuy nhin, gii hn ny c th khc nhau. Nh cp trn, mt reader c th h tr n 4 anten ngha l c 4 cng anten. Anten ca reader cngc gi l phn t kt ni ca reader v n to mt trng in t kt ni vi tag. Anten

pht tn tn hiu RF ca my pht reader xung quanh v nhn p ng ca tag. V vy v trca anten ch yu l lm sao cho vic c chnh xc (mc d reader phi c t hi gnanten v chiu di cp ca anten b hn ch). Thm na l mt s reader c nh c th canten bn trong. V vy trong trng hp ny v tr ca anten i vi reader bng 0. Nichung anten ca RFID reader c hnh dng hp vung hoc ch nht. Hnh 4-12v 4-13trnh by mt s anten ca reader.

Hnh 4-12Anten phn cc Circular UHF ca Alien Technology


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Hnh 4-13Anten phn cc Linear UHF ca Alien Technology

* Du vt ca anten(Antenna Footprint)Du vt anten ca reader xc nh phm vi c (c gi l read window) ca mtreader. Ni chung, du vt anten cng c gi l m hnh anten, c 3min kch thc chnh dng gn ging hnh elip hoc hnh cu nh ra trc anten. Trong min ny, nnglng ca anten tn ti, v vy reader c th c tag t trong min ny d dng. Hnh diytrnh by m hnh anten n gin nh th.

M hnh anten n gin

Trn thc t th do c tnh ca anten, du vt ca anten khng c hnh dng n nh

nh mt hnh elip m lun mo m, c ch nh ra. Mi ch nh ra b bao quanh bi mincht, min cht ny c gi l null. Hnh sautrnh by minh ha m hnh anten nh th.


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M hnh anten mo, nh

S phn x tn hiu anten ca reader trn i tng chn sng RF gy ra multipath.Trong trng hp ny, sng RF b phn x ri rc c th ti anten ca reader khng ng

thi theo nhng hng khc nhau. Mt s sng n c th cng pha (ngha l hp vi mhnh sng ca tn hiu anten gc). Trong trng hp ny, tn hiu anten gc tng khi ccsng ny p t vi cc sng gc lm tng mo dng. Hin tng ny c gi l nhiu cxy dng. Mt s sng c th n ngc pha nhau (ngha l ngc li vi m hnh snganten gc). Trong trng hp ny tn hiu anten gc b hy khi hai dng sng ny p t vonhau. Hin tng ny c gi l nhiu tiu cc. Kt qu l null. Hnh sau trnh by minhha multipath.

M hnh multipath

Tag c t ti mt trong nhng min nh ra s c c cn nu tag di chuynsao cho n nm trong min cht bao quanh th khng th c tag c na. Chng hn ttag xa reader th khng th c tag nhng khi di chuyn (cng hng) li reader th c thc c tag, tuy nhin nu tag ny di chuyn hng khc th khng c c n. V vy


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vic c tag gn min nh ra khng ng tin cy. Khi t anten quanh phm vi c, lm sao khng ph thuc vo min nh ra tng ti a khong cch c l iu quan trng.Chin lc ti u nht l t bn trong min c hnh elip d c ngha l b qua mt vi feet

phm vi c, nhng an ton vn hn.

iu quan trng l xc nh du vt ca anten, du vt anten xc nh nhng ni m cth hoc khng th c tag. Nh sn xut c th quy nh du vt anten nh mt c im kthut ca anten. Tuy nhin, nn s dng thng tin nh mt nguyn tc ch o, v trn thct du vt s khc ty mi trng hot ng. C th s dng k thut hon ton chnh xcnh phn tch tn hiu vch ra du vt anten. Phn tch tn hiu l o tn hiu t tag, sdng thit b nh my phn tch ph hoc my phn tch mng li truyn thanh nhngiu kin khc nhau (chng hn trong khng gian khng c rng buc, nhng hng tagkhc nhau v trn nhng vt liu dn hoc vt liu ht thu). Nh vo vic phn tch cng tn hiu c th xc nh chnh xc du vt anten.

VI - Nhng phn ca mt giao thc readerBt k giao thc reader hin thi no cng cung cp kh nng hot ng trong mt mitrng sn xut. Cho nn tt c giao thc reader u phi tun theo mt cu trc chung.

m t kh nng v cu trc c bn ca giao thc reader, trc tin s gii thiu mt s thutng:

Alert(bo ng): l mt thng ip t reader gi nreader thay i hoc cha thng tin mi nht v sc khe ca reader.

Command (lnh): l mt thng ip t my ch n reader gy ra s thay i trngthi reader hoc phn ng ca reader.

Host(my ch): l mt thnh phn middleware hoc ng dng lin lc vi cc reader. Observation(s theo di): l mt mu tin gm mt s gi tr mt ni hoc mt thiim no , chng hn nhit bn trong thit b lm lnh ti mt thi im no hoc s

xut hin ca tag 42 ti cas 5 vo lc 16:22:32 vo 23 thng 7 nm 2005.

Reader:l mt cm bin lin lc vi cc tag theo di cc nhn dng ri sau linlc nhng theo di ny vi my ch.

Transport(vn chuyn): l mt c ch lin lc c dng bi reader v my ch Trigger: Trigger l mt s tiu chun, chng hn nh thi im trong ngy s gy ra

mt s hot ng. V d mt trigger c c tnh gi, c mi 12 pht th mt reader s ccc tag no c mt .

Vi nhng thut ng c m t, ta c th nh ngha giao thc reader l mt b lutchnh thc xc nh phng thc m mt hoc nhiu my ch v mt hoc nhiu reader cth truyn cc command, observation, alertqua mt transport. Bt k giao thc reader nocng phi gii quyt ba kiu truyn chnh: cc command t my ch n reader, ccobservation t reader n my ch v cc alert t reader n my ch. Hnh sau trnh by

phng thc thng tin xut pht.


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Mc d s ny ch trnh by mt reader v mt my ch nhng v mt l thuyt thtng s reader bt k c th lin lc vi tng s my ch bt k. Cc giao thc reader hinhnh v xut hng ti vic gii hn tng s my ch m mt reader c th lin lc v lich ca hiu sut mng ang thc thi giao thc . Tuy nhin, my ch c th lin lc vitng s reader bt k bng cc giao thc ny.

Hy xem xt k hn cc loi thng tin c trao i gia cc reader v cc my ch.1.Cc lnh

Mt my ch gi cc lnh n mt reader gy ra mt vi phn ng t reader hoc thay i trng thi ca reader theo mt s phng thc. Ta c th chia cc lnh m my chgi n reader thnh ba loi:

Lnh cu hnh:Nhng lnh ny ci t v cu hnh reader. Lnh theo di:Nhng lnh ny reader c, ghi hoc sa i thng tin tag ngay tc

khc.

Lnh trigger:Nhng lnh ny thit lp cc trigger cho cc s kin nh c hoc thngbo.2.Thng bo

Mi khi mt reader theo di hoc pht mt alert th n phi truyn thng bo lin quann nhng s theo di hoc alert ny n my ch. S lin lc c th c khi to bireader (truyn bt ng b) hoc qua lnh request t my ch (truyn ng b).

2.1Bt ng bVi cch tip cn bt ng b, reader bo cho my ch bit c mt s theo di hoc

alert ngay tc th hoc khi c mt trigger xy ra lm cho reader gi thng bo no . Hnhdi ytrnh by s lc cch tip cn ny.


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Phng php ny c th l phng php c hiu qu i vi vic gi cc thng bo tnhiu reader n mt my ch. Kha cnh phc tp ca cch tip cn ny l xc nh cchthc iu khin mt my ch khi n b tht bi (fail). N ph thuc vo qu trnh v chuyn(transport) v iu ny c th c x l bng k thut cn bng ti.

2.2ng b (polling)i vi vic truyn ng b, my ch gi mt lnh cho reader v yu cu c s theo

di ngay hoc mt bo co v s theo di hoc alert no . Reader tr li bng mt danhsch thng tin yu cu. Tin trnh thc hin cc yu cu lp i lp li t my ch c gil polling reader. Hnh sau trnh by cc bc.

Polling d c thc thi, cho php cc my ch fail nhng cch tip cn ny p t chuk CPU thm vo my ch, reader v i hi s dng transport nhiu hn, yu cu cc thng

bo s thng tr v mt danh sch rng, trong khi cch tip cn bt ng b th vic lin lcthng ch xy ra khi thng tin mi sn c.

Ch :Mt s cch tip cn bt ng b gm c tnh nng keepalive m mt thngbo rng t reader n my ch vo khong thi gian thit lp cho thy reader vn hotng d khng c s theo di hoc alert no xy ra.

VII - Cc giao thc ca i l cung cpCc nh cung cp reader RFID khc nhau to ra cc giao thc reader khc nhau

ng k nhng tt c thc hin cng chc nng c bn. Trong phn sau, ta xem xt mt ngdng RFID n gin hello world s dng cc giao thc reader t hai nh sn xut readerhng u, Alien v Symbol.


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1. AlienCng ngh ca Alien s dng cc thut ng ch tng tc (Interactive mode)v ch

t tr (Autonomous mode)i vi hai kiu truyn ng b v bt ng b, nhng ccbc tng ng c thc thi bi reader v my ch th tng t nhau. Reader ca Alienn

giao trinh cong nghe rfid 120921121946 phpapp01

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