MC LC

BNG K HIU CC CH VIT TT ......................................................................... 1

DANH MC CC HNH V ........................................................................................... 3

DANH MC CC BNG ............................................................................................... 4

M U .......................................................................................................................... 5

Chng 1 GII THIU TNG QUAN V BLUETOOTH ............................................. 6

1.1. Khi nim Bluetooth ............................................................................................... 6

1.2. Lch s hinh thnh v pht trin ca Bluetooth. ................................................... 6

1.3. Cc c im ca Bluetooth................................................................................. 8

1.4. ng dng ca Bluetooth. ..................................................................................... 9

Chng 2 K THUT BLUETOOTH . ..................................................................... 10

2.1. Cc khi nim dng trong cng ngh Bluetooth. ................................................... 10

2.2. Cch thc hot ng ca Bluetooth. ...................................................................... 12

2.3. Cc tng giao thc trong Bluetooth. ...................................................................... 12

Chng 3 CC PHNG PHP NH V............................................................ 14

3.1. Thi gian sng ti .............................................................................................. 14

3.2. Sai khc ca thi gian sng ti .......................................................................... 14

3.3. Gc sng ti ...................................................................................................... 14

3.5. Mc cng sut thu ............................................................................................. 16

Chng 4 H THNG NH V BNG BLUETOOTH ........................................... 19

4.1. Thit k ca h thng nh v bng Bluetooth .................................................... 19

4.1.1. Nguyn l hot ng ca h thng. ................................................................ 19

4.1.2. Widcomm Bluetooth SDK ............................................................................. 22

4.2. Thc thi h thng ............................................................................................... 29

4.2.1. Phn cng v phn mm ................................................................................ 29

4.2.2. Lp trnh ng dng nh v ............................................................................ 33

4.3. Kt qu thc nghim v nh gi ....................................................................... 35

4.3.1. Xy dng d liu tng quan gia RSSI v khong cch. ............................. 35

4.3.2. Xc nh v tr t c s d liu ...................................................................... 36

4.4. Mt h thng nh v xut trong tng lai ..................................................... 39

4.4.1. Yu cu ca mt h thng nh v bng Bluetooth ......................................... 39

4.4.2. H thng nh v xut................................................................................ 39

4.4.3. ng dng ca h thng nh v bng cng ngh Bluetooth ............................ 40

TNG KT .................................................................................................................... 42

TI LIU THAM KHO............................................................................................... 43

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BNG K HIU CC CH VIT TT

ACL Asynchronous Connectionless

AGPS Assisted GPS

AOA Angle Of Arrival

API Application Programming Interface

CRC Cyclic Redundancy Check

DLL Dynamic-link Library

EDR Enhanced Data Rate

FCC Federal Communications Commission

FTP File Transfer Profile

GPS Global Positioning System

GRPR Golden Received Power Range

GSM Global System for Mobile Communications

GUID Globally Unique Identifier

HCI Host Controller Interface

ISM Industrial, Scientific, Medical

L2CAP Logical Link Control and Adaptation Protocol

LAN Local Area Network

LBS Local Based Services

LMP Link Manager Protocol

LOS Light Of Sight

LSE Least Squared Estimation

MAC Media Access Control

OBEX Object Exchange

RSSI Received Signal Strength Indicator

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SCO Synchronous Connection-Oriented

SDK Software Development Kit

SDP Service Discovery Protocol

SIG Bluetooth Special Interest Group

TDOA Time Difference Of Arrival

TOA Time Of Arrival

UUID Universal Unique Indentifier

WLAN Wireless LAN

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DANH MC CC HNH V

Hnh 1.1 Logo ca Bluetooth................................................................................6

Hnh 1.2 Cc thit b s dng Bluetooth...............................................................6

Hnh 2.1 - Minh ho mt Piconet...........................................................................10

Hnh 2.2 - Minh ho mt Scatternet.......................................................................11

Hnh 2.3 Hot ng ca mt piconet...................................................................12

Hinh 2.4 - Qu trinh truy vn to kt ni...............................................................12

Hinh 2.5 - Cc tng nghi thc Bluetooth...............................................................13

Hnh 3.1 Phng php AOA................................................................................15

Hnh 3.2 Phng php nhn dng cell.................................................................16

Hnh 3.3 - Xc nh v tr t cng sut thu..............................................................17

Hnh 3.4 Lin h gia cng sut thu v khong cch...........................................18

Hnh 4.1 Khong Thu Vng..................................................................................20

Hnh 4.2 Bluetooth stack dnh cho Windows......................................................24

Hnh 4.3 Ca s ng dng nh v.......................................................................33

Hnh 4.4 o trong phng trng............................................................................35

Hnh 4.5 o trong phng c c.....................................................................36

Hnh 4.6 S b tr thc nghim.......................................................................37

Hnh 4.7 S b tr cc access point.................................................................39

Hnh 4.8 M hnh h thng nh v xut.........................................................40

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DANH MC CC BNG

Bng 4.1 Cc Class ca WIDCOMM SDK........................................................24

Bng 4.2 - Cc gi tr GUID chun cho cc lp dch v Bluetooth.....................26

Bng 4.3 Hm StartInquiry()..............................................................................27

Bng 4.4 Hm StopInquiry()..............................................................................27

Bng 4.5 Hm OnDeviceResponded() .............................................................28

Bng 4.6 Hm OnInquiryComplete().................................................................28

Bng 4.7 Hm GetConnectionStats().................................................................29

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M U

inh vi c xem la mt chc nng quan trong cua truyn thng di ng . Kh nng nhn bit vi tri cho phep thc hin cac ng dung va dich vu mi . Mt s ng dng hu ch c th k n nh gim st ti sn, d ng c trin khai trong thc t nh c h thng nh vi ton cu. H thng inh vi toan cu (GPS) l mt h thng dn ng toan cu da vao cac v tinh , trong v tr ca thit b di ng c th c xc nh nu bit c khong cch t thit b n 4 v tinh gn nht.

Tuy nhin GPS khng th dung trong nha vi b thu GPS thng la v dung nu nh mt i ng khng che khut (light of sight LOS) ti v tinh . H thng Assisted GPS (AGPS) c th m rng ti mi trng trong nha , tuy nhin khi y b thu tr nn l thuc vao h tr cua mang . Xut pht t yu cu thc tin nh trn m vic pht trin mt k thut nh v mi cho cc thit b trong ta nh hay ni b che khut tr thnh mt vn rt c quan tm hin nay.

Tnh nng nh v c thit k cho mng cc b khng dy (WLAN), tuy nhin cng ngh ny c nhiu hn ch nh s lng thit b c chc nng wi-fi cn t v t , nng lng tiu hao ln nn khng dng c trong thi gian di. Bluetooth cung tng t nh WLAN hin nay nu xet v vic inh vi , mt khc cng ngh Bluetooth c nhiu u im vt tri cho mt h thng nh v cc b. Do o nay sinh nhu cu inh vi vi Bluetoot h, c bit khi ma cac thit bi Bluetooth ngay cang c s dung nhiu. Xut pht t nhng yu t , lun vn tin hnh nghin cu v th nghim mt h thng nh v dng cng ngh Bluetooth.

Lun vn c t chc nh sau: Chng mt gii thiu tng quan v cng ngh Bluetooth, bao gm lch s pht trin v cc c im cng nh ng dng. Chng hai trnh by cc l thuyt v c im k thut ca cng ngh Bluetooth. Chng ba cp n cc phng php nh v vi Bluetooth. V cui cng mt h thng nh v bng Bluetooth cng vi kt qu thu c s c cp trong chng bn. Trong chng ny cng s xut mt h thng nh v tip tc pht trin trong tng lai.

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Chng 1 GII THIU TNG QUAN V BLUETOOTH

1.1. Khi nim Bluetooth

Bluetooth la m t chun cng ngh khng dy m cho php trao i d liu gia cc thit b di ng trong phm vi ngn bng sng v tuyn qua bng tn ISM (Industrial, Scientific, Medical) trong day tn 2.40 - 2.48 GHz. Cng ngh ny to ra mt m hnh mng d liu phm vi nh gi l mng c nhn (Personal Area Netwoks PAN) c bo mt cao. c khi pht t Ericsson Mobile Communication gia thp nin 90 nh la mt cng ngh thay th dy cap , Bluetooth a tr nn ph bin sau mt thi gian ngn. Ngy nay c h tr bi hn 18000 cng ty trn ton th gii [10].

Cng ngh Bluetooth c qun l v chun ha bi mt nhm gi l SIG (Bluetooth Special Interest Group). Cc thnh vin ca SIG hin rt ng o, bao gm cc lnh vc vin thng, my tnh, mng v in t tiu dng. Nhm SIG qun l cc chng trnh thm nh cht lng v bo v thng hiu, mt thit b c chng nhn l mt thit b Bluetooth, thit b phi p ng c cc chun do SIG t ra. Bn cnh vic iu chinh cc giao thc t mc trn cung ti mc di cung cua chng giao thc, Bluetooth SIG con tao ra cac nhom lam vic khac nhau tp trung vao mt ng dng c th v mt phm vi dch v . Mi nhom tp trung vao vic chun ho a mt Bluetooth profile. Bluetooth profile tao ra mt lat ct thng ng qua cac lp giao thc nh ngha mt tp con ph hp ca chun nhm h tr mt dch v c th.[1]

Hnh 1.1 Logo ca Bluetooth

1.2. Lch s hinh thnh v pht tri n ca Bluetooth.

Hnh 1.2 Cc thit b s dng Bluetooth

Thut ng "Bluetooth" (c ngha l "rng xanh") c t theo tn ca mt v vua an Mch, vua Harald Bluetooth, l v vua a thng nht an Mch v Na Uy. Tn gi ny

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xut pht t vic m chi Bluetooth l mt cng ngh c th lm iu tng t vi cc giao thc truyn thng, hp nht cc chun ny thnh mt chun chung.[1]

Nm 1994 hng vin thng Ericsson xut mt chun khng dy tm ngn thay th dy cp RS232, cho php kt ni vi thit b cng lc, gii quyt c vn ng b gia cc thit b.

Cc c t dnh cho cng ngh Bluetooth c chun ha bi nhm SIG, l mt t chc c thnh lp vo nm 1998 bi cc cng ty hng u bao gm Ericsson, IBM, Intel, Toshiba v Nokia, v sau c s tham gia ca nhiu cng ty khc. Tt c cc phin bn ca Bluetooth c thit k c th tng thch ngc. Cc phin bn c pht trin cho n nay bao gm: [10]

Bluetooth v1.0 v v1.0B

Phin bn v1.0 v v1.0B c nhiu nhc im khin cho cc thit b giao tip kh khn.

Bluetooth v1.1

L chun khng dy IEEE 802.15.1-2002, chinh sa cc li ca phin bn trc, ng thi h tr cho cc knh khng m ha. N cng a ra chi s cng cng sut thu (RSSI).

Bluetooth v1.2

L chun IEEE 802.15.1-2005, tng thch vi phin bn 1.1 v c mt s ci tin ng k nh:

- Kt ni v d tim nhanh hn - Cng ngh tri ph nhy tn thch nghi (AFH) gip trnh nhiu. - Tc truyn thng cao hn, ln n 721 kbit/s. - Kt ni ng b m rng (eSCO) gip nng cao cht lng m thanh bng cch

cho php truyn li cc gi tin b mt v c ty chn cho vic tng tr truyn m thanh tng tc truyn d liu.

- Host Controller Interface (HCI) h tr chun UART 3 dy ni. - a vo cc ch iu khin lung v truyn li trong lp L2CAP

Bluetooth v2.0 + EDR

c pht hnh nm 2004 v tng thch vi phin bn 1.2. Khc bit ln nht l s ra i ca cng ngh truyn d liu tng cng (Enhanced Data Rate EDR) gip truyn d liu nhanh hn. EDR l mt tnh nng ty chn i km.

Bluetooth v2.1 + EDR

c pht hnh nm 2007 vi tnh nng ni bt l Secure simple pairing (SSP) gip ci thin kh nng pairing gia cc thit b trong khi tng cng tnh bo mt.

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Bluetooth v3.0 + HS

Phin bn ny c a ra nm 2009, cho tc truyn d liu ln ti 24 Mbit/s. Tnh nng HS (High Speed) gip truyn thng tc cao qua chun 802.11.

Bluetooth v4.0

Bao gm ba giao thc: Classic Bluetooth, Bluetooth high speed v Bluetooth low energy. Phin bn ny c pht hnh nm 2010.

1.3. Cc c im ca Bluetooth

- c im ni bt ca cng ngh Bluetooth l tiu th nng lng thp, cho php ng dng c trong nhiu loi thit b, bao gm c cc thit b cm tay v in thoi di ng vi gi thnh thit b r.[1]

- Khong cch giao tip cho php : Khong cch gia hai thit b u cui c th ln n 10m ngoi tri, v 5m

trong nh.

Khong cch thit b u cui v Access point c th ln ti 100m ngoi tri v 30m trong nh.

- Tuy cng sut tiu th thp nhng tc truyn d liu ca Bluetooth c th t ti mc ti a 24Mbps (v4.0) m cc thit b khng cn phi thy trc tip nhau.

- Nh c cc chun Bluetooth Profile nn d dng trong vic pht trin ng dng, do c th c lp v phn cng cng nh h iu hnh s dng.

- Trong mt mng c nhn (PAN) c 3 knh truyn ting ni, v 7 knh truyn d liu

- Tnh an ton v bo mt c tch hp vi s xc nhn v m ha ( build in authentication and encryption).

- Tnh tng thch cao, c nhiu nh sn xut phn cng cng nh phn mm h tr. [1]

- Nh giao tip bng sng radio m d liu Bluetooth c th xuyn qua cc vt th rn v phi kim. Sng radio ca Bluetooth c truyn i bng cch nhy tn s (frequency hopping), c ngha l mi packet c truyn trn nhng tn s khc nhau. Tc nhy nhanh gip trnh nhiu tt. Hu ht cc nc dng 79 bc nhy, mi bc nhy cch nhau 1MHz, bt u 2.402GHz v kt thc 2.480GHz.

- Bluetooth c thit k hot ng mc nng lng rt thp. c t a ra 3 mc nng lng t 1mW ti 100 mW [1]

o Mc nng lng 1 (100mW): c thit k cho nhng thit b c phm vi hot ng rng (~100m)

o Mc nng lng 2 (2.5mW): Cho nhng thit b c phm vi hot ng thng thng (~10m)

o Mc nng lng 3 (1mW): Cho nhng thit b c phm vi hot ng ngn (~5m)

- Nhng thit b c kh nng iu khin mc nng lng c th ti u ha nng lng bng cch dng nhng lnh LMP (Link Manager Protocol).

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1.4. ng dng ca Bluetooth.

Bluetooth cho php kt ni v trao i thng tin gia cc thit b nh in thoi di ng, in thoi c nh, my tnh xch tay, PC, my in, thit b nh v dng GPS, my nh s, v video game console.[10]

Cc ng dng ni bt ca Bluetooth gm:

- iu khin v giao tip khng giy gia mt in thoi di ng v tai nghe khng dy.

- Mng khng dy gia cc my tnh c nhn trong mt khng gian hp i hi t bng thng.

- Giao tip khng dy vi cc thit b vo ra ca my tnh, chng hn nh chut, bn phm v my in.

- Truyn d liu gia cc thit b dng giao thc OBEX. - Thay th cc giao tip ni tip dng dy truyn thng gia cc thit b o, thit

b nh v dng GPS, thit b y t, my qut m vch, v cc thit b iu khin giao thng.

- Thay th cc iu khin dng tia hng ngoi. - Gi cc mu qung co nh t cc pa-n qung co ti cc thit b dng

Bluetooth khc.

- iu khin t xa cho cc thit b tr chi in t nh Wii - My chi tr chi in t th h 7 ca Nintendo v PlayStation 3 ca Sony.

- Kt ni Internet cho PC hoc PDA bng cch dng in thoi di ng thay modem.

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Chng 2 K THUT BLUETOOTH .

2.1. Cc khi nim dng trong cng ngh Bluetooth.

2.1.1. Master Unit

Master thit lp ng h m xung v kiu bc nhy (hopping) ng b tt c cc thit b trong cng piconet m n ang qun ly v n cng quyt nh s knh truyn thng.

2.1.2. Slaver Unit

L tt c cc thit b cn li trong piconet, mt thit b khng l Master thi ph i l Slave.

2.1.3. Piconet

Picotnet l mt loi kt ni bao gm mt tp hp cc thit b c hnh thnh thng qua k thut Bluetooth theo m hinh Ad -Hoc. Cc thit b Bluetooth s ng vai tr cc thit b ngang hng, c th ng vai tr l master hay slave. Tuy nhin trong 1 Piconet thi ch i c 1 thit b l Master cn cc thit b khc l slave. Ti a 7 Slave cng hot ng trao i d liu ng thi trong 1 Piconet.

Hnh 2.1 - Minh ho mt Piconet

Hai Slave mun thc hin lin lc phi thng qua Master bi chng khng trc tip trao i c vi nhau.

2.1.4. Scatternet:

L 2 hay nhiu Piconet c lp v khng ng b, cc Piconet ny kt hp li truyn thng vi nhau.[1] Mt Scatternet c hnh thnh khi mt thnh vin ca mt piconet (master hay slave) c chn tr thnh slave ca mt piconet khc. Hin ti vic thc thi scatternet cn rt hn ch v gii hn ca Bluetooth v giao thc a chi MAC.

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Hnh 2.2 - Minh ho mt Scatternet

2.1.5. Kt ni theo kiu ad hoc

Kt ni ad hoc da vo s lin lc gia cc im, khng cn thit b h tr kt ni gia cc thit b di ng, khng cn mch iu khin trung tm cho cc unit da vo thit lp kt ni. Trong Bluetooth, l mt s lng ln cc kt ni ad hoc cng tn ti trong mt vng m khng cn bt k mt s sp xp no, cc network c lp cng tn ti chng cho ln nhau [1]

2.1.7. Trng thi ca thit b Bluetooth

C 4 trng thi chnh ca 1 thit b Bluetooth trong mt piconet: [1]

- Inquiring device (inquiry mode): thit b ang pht tn hiu tim thi t b Bluetooth khc.

- Inquiry scanning device (inquiry scan mode): thit b nhn tn hiu inquiry ca thit b ang thc hin inquiry v tr li.

- Paging device (page mode): thit b pht tn hiu yu cu kt ni vi thit b a inquiry t trc.

- Page scanning device (page scan mode): thit b nhn yu cu kt ni t paging device v tr li.

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2.2. Cch thc hot ng ca Bluetooth.

Hnh 2.3 Hot ng ca mt piconet

- Mt kt ni mi c thit lp da trn tin trinh INQUIRY v PAGE. Tin trinh Inquiry gip mt thit b d tm pht hin cc thit b khc trong tm hot ng cng vi a chi v xung ng h (clock) ca n.

- Sau thit b thc thi tin trinh Paging to kt ni. Thit b no thit lp kt ni s phi thc hin tin trinh paging v t ng tr thnh Master ca kt ni. C hai dng paging. Mt chin lc paging bt buc tt c cc thit b Bluetooth u phi h tr, dng khi cc Unit gp trong ln u tin, v trong trng hp tin trinh paging theo ngay sau tin trinh inquiry . Hai Unit sau khi kt ni nh dng chin lc bt buc ny, sau c th chn dng paging khc.

- Sau th tc Paging (PAGE), Master thm d Slave bng cch gi packet POLL thm d hay packet NULL rng theo nh Slave yu cu. Chi c Master gi tn hiu POLL cho Slave, ngc li khng c.[1]

Hinh 2.4 - Qu trinh truy vn to kt ni.

2.3. Cc tng giao thc trong Bluetooth.

Cng ngh Bluetooth s dng rt nhiu giao thc khc nhau. Cc giao thc ct li c nh ngha bi t chc SIG. Cc giao thc khc c a vo bi cc t chc khc. Chng giao thc Bluetooth c chia thnh hai phn: mt phn l controller stack cha giao din radio v mt phn l host stack gii quyt mc d liu bc cao. Tng controller stack c thc thi ti mt thit b silicon gi thnh thp cha Bluetooth radio v mt vi x l. Tng host stack thng c thc thi nh l mt thnh phn ca h iu hnh hoc nh mt thnh phn c th ci t vo mt h iu hnh. Vi cc thit b tch hp nh tai nghe Bluetooth thi host stack v controller stack c th chy chung trn cng mt vi x l gim gi thnh, y c gi l mt h thng hostless.[10]

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Hinh 2.5 - Cc tng nghi thc Bluetooth.

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Chng 3 CC PHNG PHP NH V

Cc phng php nh v bao gm s tc ng qua li gia hai hay nhiu thit b truyn thng vi nhau. Mt thit b truyn thng c th ng vai tr l my pht hoc my thu ti mt thi im no . Trong tt c cc phng php nh v th mt tn hiu s c pht i t my pht v truyn qua knh truyn i n my thu. My thu c lng v tr ca n da trn tn hiu thu c v cc c im ca n. Cc c im ny thay i khi tn hiu truyn qua knh v khc nhau vi tng phng php nh v. C nhiu phng php nh v mt thit b di ng bng cng ngh sng radio. Da vo cc c tnh truyn sng m ta c th c cc cch tip cn khc nhau i vi vic nh v. [7]

3.1. Thi gian sng ti

Mt phng php xc nh v tr ca mt thit b di ng l bng cch o thi gian ti (Time Of Arrival TOA) ca tn hiu, khi bit c thi im truyn v tc truyn. Ngun tn hiu xut pht t mt thit b tnh bit v tr chnh xc. Qu trinh o bao gm vic c lng khong cch gia thit b di ng v thit b tnh (ngun pht tn hiu). Mi mt khong cch o c s to thnh mt vng trn c tm l thit b tnh. V tr ca thit b di ng c xc nh t giao im ca cc vng trn . Khong cch o c s tng ng vi thi gian ti, quan h y l ti l thun: khong cch bng thi gian nhn vi tc truyn.

Trong thc t thi chnh xc ca phng php TOA chu nh hng rt ln ca h thng ng h. Ta bit rng tc truyn tn hiu khng dy trong khng kh l 3x108 m/s, v vi mt sai s 1s s dn ti sai s o khong cch vo khong 300m. Do phng php ny yu cu chnh xc rt cao ca ng dng cng nh chnh xc ca php o TOA m iu ny ph thuc vo phn cng.

3.2. Sai khc ca thi gian sng ti

Mt phng php nh v khc l o sai khc thi gian ca sng ti (TDOA). H thng ny dng nhiu b thu tnh c s ng b ha rt cao v mt thi gian. Tn hiu truyn i t thit b di ng n cc b thu ng b ha. Mi b thu lu li thi gian lc n nhn c tn hiu ny v truyn ti cc b thu khc. Thi gian sai khc gia hai b thu lin tip tng ng vi khong cch gia thit b di ng v b thu tnh.

Phng php TDOA ny cng ging nh TOA, yu cu mt h thng ng h chnh xc cao, m iu ny thi thng khng c vi cc thit b di ng thng thng.

3.3. Gc sng ti

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Phng php nh v bng gc sng ti (AOA) ca mt tn hiu nhn c dng gc ny nh mt chi s gc t my thu so vi ngun tn hiu. Vic o AOA ca mt tn hiu yu cu phi c mt anten nh hng. Anten ny c to bi mt dy cc phn t anten m c kh nng chia cc bp sng tng ng nhau theo cc hng khc nhau. Ti bp sng m c cng cao nht thi chnh l v tr gc m sng thu c. Trong h thng ny thit b di ng ng vai tr l my pht v thit b tnh ng vai tr l my thu, do cc thit b di ng thng khng c anten nh hng. H thng nh v AOA cn rt nhiu anten, iu ny l rt bt li trong thc t.

Hnh 3.1 Phng php AOA

3.4. Nhn dng cell

Mi thit b Bluetooth u c mt con s nhn dng duy nht. Ngay khi mt thit b kt ni ti mt piconet, n s nhn c cc s nhn dng (ID) duy nht t cc thit b khc. Cc gi tr ID ny l chia kha cho vic nh v bng nhn dng cell. Mt trm c s c nh s gi s ID ca n cho thit b mi kt ni ti. Vi mt thit b Bluetooth chi hot ng trong khong 10m nn ngi dng vi thit b Bluetooth s bit c l anh ta ang trong phm vi 10m so vi trm c s. Gi tr ID ny cn c th c lu vo c s d liu cho php nh v vi chnh xc 10m.

chnh xc ca phng php ny c th c nng cao nu nh c nhiu trm c s hn. Nu thit b c th kt ni ti hai hay nhiu trm c s thi chnh xc c tng ng k. Khi v tr ca thit b nm trong vng giao nhau ca cc ng trn.

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Hnh 3.2 Phng php nhn dng cell

3.5. Mc cng sut thu

Mt cch khc nh v l o cng sut tn hiu thu. Vi cng sut thu suy gim khi tn hiu truyn qua khng kh v suy gim t l vi khong cch nn khong cch ny c th c c lng khi bit cng sut tn hiu thu.Phng php ny da trn cng sut t mt s ngun.T cc gi tr v tr ca thit b di ng c th c xc nh t giao im ca cc ng trn tng ng vi mi ngun pht.

chnh xc ca phng php ny ph thuc vo chnh xc ca vic truyn tn hiu ti mt cng sut c nh v chnh xc ca vic o cng sut ti my thu.

Mt khc, bt k s bin thin cng sut truyn no u l n s i vi my thu, v nh vy my thu s cho rng nhng s bin thin nh vy l do suy gim theo khong cch. Do h thng cn u tin ngun pht m c cng sut pht c nh. Cc tc ng khc c nh hng ti cng tn hiu l li ca anten v nhiu a ng.[3]

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Hnh 3.3 - Xc nh v tr t cng sut thu

suy gim cng sut thu c th c m t bng m hinh truyn sng trong khng gian t do:

= + + + 20 log

4 10

Trong PRX l mc cng sut thu, PTX l mc cng sut pht; GTX, GRX ln lt l li ca anten pht v thu (o bng dBi) ; c l vn tc truyn sng (3.108 m/s); f l tn s sng mang; n l h s suy gim ( n bng 2 trong khng gian t do); v d l khong cch gia my pht v my thu.

Mi lin h gia cng sut thu v khong cch theo m hinh truyn sng c biu din nh hinh di y. [4]

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Hnh 3.4 Lin h gia cng sut thu v khong cch

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Chng 4 H THNG NH V BNG BLUETOOTH

4.1. Thit k ca h thng nh v bng Bluetooth 4.1.1. Nguyn l hot ng ca h thng.

Vic inh vi trong nha bng Bluetooth vi chinh xac vao khoang mt vi mt s gip thc hin cc dch v da vo v tr (LBS). Cc dch v ny bao gm dch v nh v y t , mng my tnh v i cc sensor wireless , thu nhn d liu di ng va cac h thng theo du , bn trong nh (e-map) cho cac ng dung an ninh va cac thit bi thng minh vi kha nng nhn inh vi tri .

Hin ti h thng nh v cho thit b di ng ph bin l GPS. Tuy nhin h thng ny chi hot ng ngoi tri, ni c t vt cn; mt khc, chnh xc ca h thng nhiu khi cha p ng c cc yu cu c th trong phm vi hp hay a hnh phc tp. nh v thit b trong mi trng trong nh (indoor) l mt trng hp in hnh cn phi c mt k thut nh v mi. [7]

Trong s cc phng php nh v khng dy nghin cu: Gc sng ti (AOA), Thi gian ti (TOA), Sai khac thi gian ti (TDOA) thi i vi phng phap u tin , AOA, yu cu phai co mt dan anten c bit o goc tin hiu nhn c . Kt qua la cn co mt h thng chuyn bit vi gia cao . Vic dung ky thut da vao thi gian (TOA v TDOA ) yu cu co cac ng h chinh xac trong h thng. chnh xc ng h / tri thi gian trong mt thit bi di ng la ~ 1s nhng cn phai co chnh xc 3 ns nu mun c chnh xc v tr 1m.[4]

H thng nh v y chn k thut nh v da theo cng sut thu. V thit b Bluetooth khng cho ta mt giao din no ly ra gi tr cng tn hiu nhn thc t nn h thng ny s dng gi tr RSSI c nh ngha trong chun Bluetooth suy ra c lng khong cch gia access point v thit b di ng.

Ta cn lu rng vi mi trng trong nh th yu t nhiu tc ng rt ln ti cng sut thu, chng hn nh a ng do phn x hay hp th. Do vy vic dng m hnh truyn sng trong khng gian t do l rt kh khn. Do , trong h thng ca chng ta, cc tnh ton khong cch s c tnh bng xp xi ca chi s cng tn hiu (RSSI) da trn s c lng v mi lin h gia RSSI v khong cch. Cc gi tr RSSI c o bng thc nghim, v c tin hnh trong cc v tr v khong cch khc nhau.

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4.1.1.1. c lng khong cch t RSSI

Binh thng h thng Bluetooth dung chi s cng tin hiu nhn may phat t ng iu chinh cng sut nhm am bao ti s tin hiu trn nhiu : RSSI (Received signal Strength Indicator) . Gi tr RSSI c th chuyn i thnh mc cng sut tuyt i nu mt vng c gi l Khong Thu Vng (Golden Received Power Range - GRPR) ca mt my thu c th bit. [11]

nh ngha ca Khong Thu Vng c minh ha nh hinh sau:

Hnh 4.1 Khong Thu Vng

Khong Thu Vng c gii hn bi hai ngng. Ngng di c nh ngha r rng bng mt gi tr lch 6dB so vi nhy thc t ca my thu. Gi tr ln nht c xc nh l -56dBm. Ngng trn l gi tr nm cao hn 20dB so vi ngng di. chnh xc ca ngng trn l khong 6dB.

Nu cng sut i vo nm xung quanh ngng di th h thng Bluetooth s yu cu thit b cn li tng cng sut u ra. iu ny l do mc cng sut thp s khin cho vic truyn d liu tr nn kh khn. Cn nu cng sut thu vo nm trong phm vi ngng trn th thit b s s c yu cu gim cng sut pht gim cng sut tiu th. [2]

nh ngha v khong thu vng lm hn ch cho vic chuyn i t RSSI sang khong cch. Nu gi tr RSSI nm trong khong thu vng th n lun bng 0, nh vy s khng xp xi c cc gi tr ny bng mt hm duy nht. Do chi nhng php o no cho gi tr RSSI khc khng mi c th s dng xp xi hm. [4]

Chng ta thc hin c lng bng cch chn hm xp xi tt nht bng cch xc nh tham s ca mt trong cc hm sau y:

y = c lnx + b,

y = c0 + c1x + c2x2,

21

y = c0 + c1x + c2x2 + c3x

3

4.1.1.2. c lng v tr t cc khong cch o c.

Vi mi gi tr RSSI nhn c, ta c mt c lng ca khong cch. Vi duy nht mt vt mc (thit b tnh thu nhn gi tr RSSI) thi r rng l khng c c lng v tr chnh xc. Cn t nht ba vt mc thc hin mt php o tam gic (triangulation), trong v tr ca thit b di ng nm trong phn chung nhau ca ba vng trn c tm l ba vt mc. c c lng chnh xc hn, ta dng thut ton binh phng ti thiu (LSE) x l cc s liu RSSI o c c. [4]

Gi s s trm c s (vt mc) l N2 v v tr ca mt trm c s k c nh ngha bi = ( ,)

, 1. .

Theo , cc khong cch , ( ) gia cc trm c s i, j v mt im trong mt

phng x-y c cho bi = (, ) l:

=

2 + 2

= 2

+ 2 (1)

Gii h phng trinh (1) cho ta hai giao im ca hai ng trn tng ng. Do , c c mt nghim duy nht th cn thit phi tnh v tr ca thit b di ng da trn khong cch gia thit b v t nht l ba trm c s khc nhau.

Nu bit c khong cch t cc trm c s n thit b di ng th v tr ca thit b di ng c th c tnh theo thut ton LSE. Phng php ny cho ta mt v tr ca thit b trn mt phng x-y m c tng binh phng khong cch n tt c cc min gii hn bi cc ng trn cho bi phng trinh (2) l nh nht.

=

2 + 2

= 2

+ 2 , i, j 1. . (2)

Phn gii hn bi cc ng trn cho bi phng trinh:

2

2 = ( )2 + ( )

2 ( )2 ( )

2 (3)

Gi s c lng v tr l = ( , ) th c tnh theo cng thc

. = (4)

Vi:

22

=

(2,1) (2,1)

(,1) (,1)

(,1) (,1)

, = , =

2,1

,1

,1

V

, = 2

, = 2

, = 2

2 + 2

2 + 2

2

T , c lng v tr ca thit b c xc nh t cng thc:

= ()1 (5)

4.1.2. Widcomm Bluetooth SDK

Vn u tin m h thng cn gii quyt l tim cch thu c gi tr RSSI t thit b Bluetooth. lm c vic ny, trc ht ta cn kho st cc Bluetooth stack, l s thc thi ca Bluetooth protocol stack (chng ngn xp Bluetooth). Cc Bluetooth stack c th chia thnh hai loi: [9]

- Thc thi vi mc ch tng qut: tp trung vo tnh nng l mm do, thng l dnh cho my tnh bn. C th h tr thm cc Bluetooth profile t cc trinh iu khin (drivers).

- Cc h thng nhng: nhm vo cc thit b c ti nguyn gii hn v c nhu cu t hn, chng hn nh cc thit b ngoi vi.

H thng ca chng ta pht trin trn nn tng my tnh bn s dng Windows, do vy ta dng Bluetooth stack loi th nht. Hin nay c khong 6 Bluetooth stack chnh dnh cho Windows c th k nh:

- Widcomm Stack - Microsoft Stack - Toshiba Stack - EtherMind Stack - BlueSoleil - BlueFritz!

Qua tm hiu ta thy rng tt c cc Bluetooth Stack ny u c h tr RSSI theo cch no . Tuy nhin, hu ht chi h tr cho cc h thng di ng nh Windows Mobile 6/CE. Chi c WIDCOMM stack h tr RSSI qua my Desktop trn Windows XP SP2/3.

23

4.1.2.1. Gii thiu WIDCOMM SDK

B pht trin phn mm (SDK) WIDCOMM Bluetooth cho Windows h tr lp trnh cho cc ng dng Bluetooth vi cc lp giao thc truy cp trc tip ti cc tng giao thc:

- L2CAP - RFCOMM - OPP - FTP - SDP - LAP - OBEX

B pht trin phn mm (DK) ny bao gm c:

- Mt th vin lin kt ng (DLL) - Cc file header C++ - Cc file ngun cho cc ng dng mu

Ng cnh hot ng cho b DK l mt nn tng Bluetooth PC chun c ci t phn mm WIDCOMM BTW. Cc ng dng ty chn c pht trin s dng DK c th chy ng thi vi ng dng WIDCOMM Bluetooth ln cn v cc profile. V mt chc nng thi DK cung cp mt giao din C++ cho cc hm Inquiry v Discovery ca lp SDP. Cc hm DK cho php truy cp ti c s d liu discovery v ti cc gi tr thuc tnh trong . ng dng ty chn c th thm vo hay xa i t SDP service database.

i vi cc lp SDP, OPP, FTP, L2CAP v RFCOMM, cc lp C++ c cung cp vi y cc hm m c th c thc thi bi WIDCOMM Blueooth stack.

4.1.2.2. Phn tch cu trc ca WIDCOMM SDK

Hnh di l mt ci nhn tng quan v DK trong ng cnh Windows Bluetooth.

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Hnh 4.2 Bluetooth stack dnh cho Windows

B DK cha mt DLL, mt file th vin v hai file header.

- WidcommSdk.dll cn c t ti ng dn tm kim ca DLL, thng l th mc lm vic (working directory) hay th mc h thng Windows.

- Cc ng dng phi c lin kt vi WidcommSdk.dll - BtIfDefinitions.h l mt file header nh ngha cc hng s v cc cu trc dng

bi DK v cc ng dng. - BtIfClasses.h l mt file header nh ngha cc lp cho bi DK

Cc Class cho bi DK

DK Class Chc nng

CbtIf Cung cp cc hm qun l mc giao din, chng hn nh cc hm inquiry v service discovery

CL2CapIf Giao tip vi L2CAP cho vic ng k, cp pht b hp knh giao thc/dch v (PSM) v cc thit lp bo mt

CL2CapConn iu khin cc kt ni L2CAP

CSdpService Qun l mt bn ghi dch v SDP.

CSdpDiscoveryRec Cha mt bn ghi SDP discovery v cc hm truy vn n.

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CRfCommIf Giao tip vi RFCOMM cho vic cp pht S knh Dch v (SCN) v cc thit lp bo mt.

CRfCommConn iu khin cc kt ni RFCOMM

CFtpClient Cung cp giao din pha client cho FTP

COppClient Cung cp giao din pha client cho OPP

CLapClient Cung cp giao din pha client cho truy cp LAN s dng PPP

CSppClient Cung cp giao din pha client cho cc kt ni cng SPP COM

CSppServer Cung cp giao din pha server cho cc kt ni cng SPP COM

CObexServer Cung cp giao din pha server cho OBEX

CObexClient Cung cp giao din pha client cho OBEX

CObexHeaders Cha class cho tt c cc cu trc header OBEX

CObexUserDefined Cha class cho OBEX header do user nh ngha

Bng 4.1 Cc Class ca WIDCOMM SDK

- Cc hm o (VIRTUAL FUNCTIONS)

Cc DK Class cung cp cc hm o cn thit cho cc ng dng phn ng vi cc s kin giao thc Bluetooth.

V d khi mt ng dng yu cu mt lin kt RFCOMM v nh ngha mt lp ng dng dn xut t lp c s CrfCommPort. Lp dn xut nh ngha cc hm dn xut thay th cho cc hm o trong CrfCommPort.

Hm OnDataReceived() c gi chuyn mt gi d liu n ng dng.

Hm OnEventReceived() c gi khi mt s kin ng lu c pht hin, chng hn nh vic kt ni hay hy kt ni.

Vi hm o l thun o tc l khng c s thc thi mc nh trong lp c s, v vy ng dng phi cung cp mt hm dn xut. Chng hn nh CSppClient::OnClientStateChange() v CLapClient::OnStateChange().

Cc hm o m khng phi l thun o c thc thi mc nh khng lm g trong lp c s DK c. Cc hm ny c th s dng cho mt ng dng nhng li khng dng cho ng dng khc.

Cc ng dng c th ly gi tr mc nh nu hm khng c ch. V d nh CRfCommPort::OnModemSignalChanged() v CRfCommPort::OnFlowEnabled().

- Hm hy cho cc DK Class

Tt c cc DK Class u c hm hy khng tm thng (non-trivial). Cc ng dng dng DK classes hay application classes dn xut t cc DK class, t khi xp (heap) phi xa cc object ngn vic r ri b nh ng dng.

26

- Cc hm dn xut chy trn cc thread ring bit

Cc hm dn xut chy trong mt ng cnh khc vi ng dng. Cc hot ng c thc thi trong cc hm dn xut phi c m bo thread-safe cho ng dng .

- M t v cch dng CBtIf Class

Class ny cung cp mt giao din ngn xp cho vic inquiry thit b v discovery dch v. Mt i tng (object) ca class ny cn c thuyt minh trc khi bt k lp DK no khc c s dng (in hnh l lc khi ng ng dng). Mt i tng ca lp ny khng nn xa cho n khi ng dng hon thnh tt c cc trao i vi ngn xp (thng l ti thi im tt ng dng ).

Class ny nh ngha nh ngha cc hm thun o CBtIf::OnDeviceResponded() v

CBtIf::OnDiscoveryComplete(). ng dng phi cung cp mt lp dn xut cho cc hm . N cng nh ngha mt hm o CBtIf::OnInquiryComplete(), m ng dng c th nh ngha khi cn thit.

Mt tp cc gi tr GUID chun cho cc lp dch v Bluetooth c cung cp nh l cc thnh phn d liu ca lp ny.

Bng 4.2 - Cc gi tr GUID chun cho cc lp dch v Bluetooth

27

4.1.2.3. Cc hm quan trng

- StartInquiry()

Khi ng qu trnh d (inquiry) thit b Bluetooth.

Bi vi ngn xp Bluetooth l a ngi dng nn tin trnh inquiry c th khng bt u ngay lp tc khi hm ny c gi, m ngn xp c th ang bn x l thao tc khc.

Cho n khi ng dng gi hm StopInquiry() th n mi nhn thng bo v tt c cc thit b mi tim thy, thm ch c khi qu trinh inquiry c bt ngun t tin trnh khc.

Trong khi tin trinh inquiry ang x l th hm OnDeviceResponded() s c gi mi khi thit b phn hi. Thng th mt ng dng s dng hm ny thu thp mt danh sch cc thit b phn hi.

ng dng c th nhn c nhiu hn mt ln gi hm OnDeviceResponded() i vi cng mt thit b, v cn phi b cc a chi BD lp.

StartInquiry() Prototype BOOL StartInquiry();

Parameters None

Returns TRUE if the inquiry was started.

FALSE otherwise.

Bng 4.3 Hm StartInquiry()

- StopInquiry()

Dng mt tin trinh inquiry ang chy.

StopInquiry() Prototype BOOL StopInquiry();

Parameters None

Returns void

Bng 4.4 Hm StopInquiry()

- Hm thun o OnDeviceResponded()

c gi mi khi c mt phn hi inquiry t mi thit b trong vng ln cn. Hm ny c th c kch hot nhiu ln vi mi tin trnh inquiry thm ch l nhiu ln trn mi thit b - mt ln cho a chi, mt ln cho a chi v user-friendly names.

28

pure virtual OnDeviceResponded() Prototype virtual void OnDeviceResponded (

BD_ADDR bda,

DEV_CLASS dev_class,

BD_NAME bd_name,

BOOL b connected ) = 0 ;

Parameters bda The address of the responding device.

dev_class The class of the responding device, see BtIfDefinitions.h

bd_name The user-friendly name of the responding device this is a null-terminated string that will have length 0 when the

device is reporting only its address.

b_connected TRUE if the responding device is currently connected to

the local device.

Returns void

Bng 4.5 Hm OnDeviceResponded()

- Hm o OnInquiryComplete()

Hm ty chn ny c th c gi khi tt c cc tin trinh inquiry hon tt, cha thao tc thu thp cc user-friendly names ca cc thit b trong vng ln cn.

Hm ny b sung, nhng khng thay th cho hm o OnDeviceResponded().

virtual OnInquiryComplete() Prototype virtual void OnInquiryComplete (

BOOL success,

short num responses ) ;

Parameters success TRUE if the inquiry is successful, otherwise there was

a device error.

num_responses The number of devices responding to the inquiry.

Returns void

Bng 4.6 Hm OnInquiryComplete()

- Hm GetConnectionStats()

Ly thng tin thng k v kt ni hin ti. Hm ny c nh ngha trong file header BtIfClasses.h

Cc thng tin thng k v kt ni c nh ngha trong cu trc tBT_CONN_STATS trong file header BtIfDefinitions.h:

typedef struct

{

UINT32 bIsConnected;

29

INT32 Rssi;

UINT32 BytesSent;

UINT32 BytesRcvd;

UINT32 Duration;

} tBT_CONN_STATS;

Trong ,

- bIsConnected 0 ngha l khng c kt ni, gi tr khc bt k ngha l c kt ni.

- Rssi Tr li chi s cng tn hiu. Gi tr 0 ngha l kt ni ti cc thit b Bluetooth mt khong cch ti u, trong vng thu vng. Gi tr dng tng dn ngha l cc thit b ang i li gn nhau. Gi tr m tng dn c ngha l cc thit b ang di chuyn ra xa nhau.

- BytesSent Tng s byte gi t khi kt ni c thit lp. N m s lng byte gi bi ng dng. Khng tnh cc byte thm vo t cc lp giao thc.

- ByteRcvd Tng s byte nhn t khi kt ni c thit lp. N m s lng byte nhn bi ng dng. Khng tnh cc byte thm vo t cc lp giao thc.

- Duration Thi gian tri qua k t khi kt ni c thit lp, o bng giy.

GetConnectionStats() Prototype BOOL GetConnectionStats(BD_ADDR bd_addr, tBT_CONN_STATS *p

conn stats);

Parameters p_conn stats A pointer to the users connection statistics structure, see above

Returns FALSE if a connection attempt has not even been initiated, TRUE otherwise.

Bng 4.7 Hm GetConnectionStats()

4.2. Thc thi h thng 4.2.1. Phn cng v phn mm

c th pht trin phn mm s dng WIDCOMM Bluetooth API, ta xy dng mt h thng gm c:

- My tnh chy h iu hnh Windows XP SP2/3 - Phn mm BTW software ca WIDCOMM - Windows Server 2003 SP1 Platform SDK - Microsoft Visual C++ 6.0 hay Visual Studio 6.0

30

- Mt USB Widcomm Bluetooth dongle (nu my tnh cha c tch hp chip Bluetooth Widcomm).

- Thit b di ng vi tnh nng Bluetooth kch hot.

Sau khi ci cc phn mm cn thit, ta khi ng Microsoft VS 6 C++

Sau ta to mt project mi: File -> New -> MFC AppWizard (exe)

31

Trong phn MFC AppWizard Step 1 ta chn Dialog based Bm Finish hon thnh vic to project.

Tip theo ta cn thm cc th vin ci t vo project ca chng ta c th s dng giao tip vi thit b Bluetooth.

- Bm vo Project -> Settings - Trong Drop-down box "Settings For" chn "All Configurations" - Bm vo tab C/C++ . Ti Preprocessor definitions thm vo _BTWLIB"

32

Sau bm chn tab "Link", trong phn " Category" chuyn thnh "Customize", sau tch vo "Force file output"

By gi ta cn thm vo cc ng dn. Bm "OK" ng cc ca s li v lu cc thit lp trong Project Settings"

Tr li main project bm chn "Tools" -> "Options" -> "Directories" sau thm vo cc "Include files"

"C:\PROGRAM FILES\WIDCOMM\BTW DK\SDK\INC"

"C:\PROGRAM FILES\MICROSOFT PLATFORM SDK\INCLUDE"

Bm chn "Library files" trong phn "Show directories for:"ta thm vo cc dng:

"C:\PROGRAM FILES\WIDCOMM\BTW DK\SDK\RELEASE"

33

"C:\PROGRAM FILES\MICROSOFT PLATFORM SDK\LIB"

Sau bm OK lu li cc thit lp.

4.2.2. Lp trnh ng dng nh v

Hnh 4.3 Ca s ng dng nh v

Sau khi ci t v thit lp cho Microsoft VS 6 C++, ta s bt u xy dng ng dng thu thp chi s RSSI t thit b Bluetooth.

Cc hot ng d tm thit b (inquiry) ca ng dng nm trong lp CBtIf. Do vy ta cn khai bo:

class C(ProjectName)Dlg : public CBtIf

34

Sau thm vo cc th vin v header gip lin kt cc thnh phn trong chng trnh.

#include "btwlib.h" //Widcomm Stack

#pragma comment(lib, "version.lib")

#pragma comment(lib, "Ws2_32.lib")

u tin, khi bt u qu trnh inquiry, ng dng s gi hm virtual void StartInquiry(). Hm ny c tha k t CBtIf v bt u vic gi lp thit b trong tin trnh ring ca n. Khi mt thit b Bluetooth c d thy trong vng ln cn, lp c s s gi mt hm o thng bo v vic ny:

virtual void OnDeviceResponded(BD_ADDR bda, DEV_CLASS

devClass, BD_NAME bdName, BOOL bConnected);

Tham s u tin l mt mng c 6 byte cha a chi ca thit b. Tham s th hai l mt mng 3 byte cha lp ca thit b. Tham s th ba l tn thit b c m ha nh l mt chui ANSI (khng phi l UNICODE) v cui cng l mt gi tr Boolean chi ra thit b c kt ni hay cha.

Sau khi tim thy thit b ta gi hm

BOOL GetConnectionStats (BD_ADDR bd_Addr, tBT_CONN_STATS

*p_conn_stats)

ly thng tin kt ni. Trong tham s th nht l a chi thit b, tham s th hai l con tr ti cu trc tBT_CONN_STATS cha gi tr RSSI.

Ta lu cc gi tr ny vo mt file text xy dng mt c s d liu gi tr RSSI.

FILE * f;

f = fopen("output.txt", "a+");

fprintf(f,"%i\n",p_conn_stats.Rssi);

fclose(f);

Khi tt c cc thit b c tm thy, lp c s CBtIf s gi mt hm o khc thng bo v ng dng :

virtual void OnInquiryComplete(BOOL bSuccess, short

nResponses);

Thng s u tin thng bo nu tin trinh d (inquiry) thnh cng v thng s th hai thng bo s lng thit b tm thy.

35

kt thc qu trnh gi lp thit b ti thi im bt k ta c th gi hm void StopInquiry(). Hm ny rt c ch khi mun reset li lc thit b khng cn hot ng ng do nguyn nhn no . [5].

4.3. Kt qu thc nghim v nh gi

Cc php o c thc hin trong cc iu kin khc nhau. Trc ht ta o gi tr RSSI ti cc khong cch bit. D liu RSSI c ly mu 100 ln cho mi v tr, sau ta ly gi tr trung bnh ca mu xy dng mt tp hp d liu biu din mi tng quan gia RSSI v khong cch. D liu ny sau s c biu din bng th v dng cc hm xp xi m hnh ha.

4.3.1. Xy dng d liu tng quan gia RSSI v khong cch.

- o trong iu kin khng c vt cn

u tin ta kho st gi tr RSSI trong iu kin phng tng i l tng, khng c vt cn gia my tnh v thit b di ng. Ta o trong khong 0 14m, mi ln ta dch thit b ra xa 0.4m. Kt qu c biu din trong th sau:

Hnh 4.4 o trong phng trng

Ta thy rng d liu c xp xi tt bi mt hm a thc bc 3

y = -0.023x3 + 0.606x

2 - 5.492x + 1.795

o trong iu kin thng

Php o th hai c thc hin ti phng c c. Kt qu o c thc hin trong mi khong 1m.

y = -0.023x3 + 0.606x2 - 5.492x + 1.795

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

36

D liu cng c xp xi bi mt hm a thc bc 3

y = -0.007x3 + 0.261x

2 - 3.821x - 1.788

Hnh 4.5 o trong phng c c

T cc th ta nhn thy rng cc gi tr RSSI ny dao ng kh mnh v khng tun theo mt quy lut nht nh, iu ny lm cho vic xp xi tr nn kh khn.

4.3.2. Xc nh v tr t c s d liu

Da trn c s d liu v tng quan gia RSSI theo khong cch, ta c th xy dng c mt h thng nh v theo phng php binh phng ti thiu (LSE). Ta thc thi h thng nh v trong mt cn phng kch thc 8m x 10m. Chn mt h ta ngang x-y dc theo cc kch thc ca cn phng.

Cc trm c s c t ti 3 im trong phng ln lt ti cc ta :

A1(0.5, 0.5)

A2(0.5, 9.5)

A3(7.5, 5.0)

y = -0.007x3 + 0.261x2 - 3.821x - 1.788

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

37

Hnh 4.6 S b tr thc nghim

t thit b di ng ti v tr M(3,8).

Thc hin cc php o RSSI ti ba trm c s, gi tr RSSI thu c ti ba trm ny ti A1, A2, A3 ln lt l -20.82, -10.54 v -16.05

T phng trinh xp xi y = -0.007x3 + 0.261x2 - 3.821x - 1.788 , ta tnh c cc khong cch tng ng l r1 = 9.10, r2 = 2.78 v r3 = 5.49.

Khi vic thc hin cc php tnh cho ta cc gi tr:

=

(2,1) (2,1)(3,1) (3,1)(3,2) (3,2)

= 0 18

14 914 9

38

=

2,13,13,2

= 180.09148.43

31.66

= 4.17 8.83

Nh vy v tr c lng ca thit b di ng nm ta M(4.17, 8.83)

Sai s ca h thng trong trng hp ny l:

= 3 4.17 2 + 8 8.83 2

= 1.43 m

Ta thy kt qu o c sai s chp nhn c, sai s c th gim bng cch tng s lng cc trm c s c nhiu gi tr RSSI hn, tuy rng iu ny s lm tng s lng cc php tnh.

Trong thc t, do nh hng ca nhiu rt phc tp, cc vt kim loi trong phng nh bn gh... l yu t lm cho s o RSSI b lch so vi l thuyt, nn vic d on sai s l kh thc hin c. Hn na, i vi mi v tr khc nhau trong phng th sai s cng khc nhau, cng nh sai s trong c lng khong cch t im ti cc access point cng khc nhau.

Ngoi ra, gi tr RSSI thu c i vi mi loi thit b di ng khc nhau cng khc nhau. iu ny gi chng ta cn phi xy dng mt m hinh c lng ring cho tng loi thit b.

39

4.4. Mt h thng nh v xut trong tng lai 4.4.1. Yu cu ca mt h thng nh v bng Bluetooth

Chng ta xy dng thnh cng mt h thng nh v trong nh vi vic thc thi mt m hinh nh v n gin gm 3 thit b ng vai tr l access point v mt thit b l thit b di ng cn nh v. h thng nh v ny p dng c trong thc tin ta cn c thm cc ci tin v pht trin. Xt mt cch tng quan, mt h thng nh v kh thi cn p ng cc yu cu sau: [8]

- Tnh sn sng: thit b di ng c th c nh v ti hu ht cc v tr trong nh ti hu ht cc thi im.

- chnh xc: chnh xc ph hp vi yu cu c th ca ngi dng, c th dao ng trong khong vi mt.

- tr: h thng nh v lun c mt tr no , l khong thi gian k t khi thit b di chuyn cho n khi v tr mi ca n c cp nht. Cn m bo tr ny khng qu ln, v ph hp vi tng ng dng c th.

- Gi c v chi ph vn hnh bo dng: vi h thng nh v bng Bluetooth th chi ph ch yu nm my ch nh v (location server) v h thng cc access point.

- Kh nng m rng: thng th vng hot ng ca h thng khng c ci tt c mt ln, m theo tng phn. Din tch bao ph c thit lp ban u l nh (chng hn cho mc ch kim tra) v sau c m rng ra. Nh vy, kh nng m rng ca h thng tr thnh mt vn rt quan trng.

- Kh nng thch ng: cc thnh phn trong h thng lun c s thay i, chng hn nh cch b tr cc access point, cc vt trong ta nh Nhng chi tit (t-p, phn vng v sp xp cc vt) vn khng ng nht, v khng phi bt bin. Chng c nh hng chnh n chnh xc ca h thng. duy tr chnh xc trong ton khu vc, h thng phi c kh nng thch nghi t thi im ny sang thi im khc (sp xp li cc anten, tinh chinh li cc thng s).

4.4.2. H thng nh v xut

Chng hn, mt m hinh nh v gm cc access point c b tr trong s sau:

Hnh 4.7 S b tr cc access point

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H thng bao gm: cc access point (cc vng trn mu trng), cc Bluetooth server, mt phn mm nh v cho my server v client. Tt cc cc Bluetooth server c ni vi h thng LAN ca ta nh, v c qun l bi mt cng c qun l qua web. iu ny em li cho h thng tnh module, v m bo cho n c kh nng m rng. Tnh kh m l c tnh rt quan trng vi thng th h thng ban u c ci t trong mt phm vi gii hn, v sau c m rng.

Hnh 4.8 M hnh h thng nh v xut

4.4.3. ng dng ca h thng nh v bng cng ngh Bluetooth 4.4.3.1. H thng dn ng

Thc t c rt nhiu a im cn ti vic nh hng v dn ng, mt ta nh ln chng hn nh sn bay l mt v d in hnh. Vic nh hng ti nhng ni n o v ng c vn l mt tri nghim kh khn nht l vi nhng du khch. Do vy mt h thng nh v trong nh s l mt cng c c bit hu ch.

Cng ngh nh v vi Bluetooth rt ph hp trong hon cnh ny. Mt khi du khch, vi thit b Bluetooth trong tay, i vo ta nh s thu nhn c thng tin t cc trm c s b tr ti cc im c nh. Thng tin nh hng c th n di dng file HTML hay di dng web ng.

chnh xc trong ng dng ny khng cn qu cao, vi phm vi 10m l c th p ng c yu cu t ra.

4.4.3.2. H thng kha t ng

Hin nay con ngi lm vic vi rt nhiu thit b x l thng tin nh my tnh. Do vic m bo cho khng c k xu xm nhp hay m bo ring t l mt yu cu rt quan trng. Vi vic xc nh c khong cch t thit b n ngi dng s gip

41

cho vic thc thi mt h thng kha t ng da trn s c mt ca ngi s hu thit b. tng ny c thc thi nh sau: my tnh s c trng b mt phn mm kha my, vic kha my da vo khong cch o c gia my tnh v mt thit b bluetooth mang km ngi dng (c th l in thoi hay smartphone), khi ngi dng cch my tnh mt khong cch nht nh th h thng s t kha my tnh cho n khi ngi dng tr li. H thng ny c u im hn h thng kha thng thng da vo thi gian, ngi dng khng cn tc ng vo my kha hay m kha.

4.4.3.3. Theo di v ln vt

Vic theo di phng tin hay ngi tr nn ph bin nh c cng ngh GPS, tuy nhin trong mt ta nh th yu cu phi c mt h thng mi. H thng nh v bng Bluetooth c th p ng c nhim v . Vi cc trm c s c nh b tr khp ta nh, h thng cho php xc nh v tr mt thit b theo thi gian. H thng ny mang li nhiu li ch kinh t to ln nu p dng vo nh my sn xut hay trong bnh vin. Trong mt nh my hay dy chuyn sn xut th trong nhng trng hp khn cp cn s tn chng hn, cng nhn c th tm thy li thot him nh c h thng nh v, hoc c pht hin ra bi nhn vin cu h sau mt thm ha. Mt h thng theo di bnh nhn cng cc k quan trng, m bo cho cc bc s pht hin kp thi cc s c c th xy ra.

4.4.3.4. H thng cung cp thng tin da trn v tr

Mt ng dng th v v cng rt hu ch ca h thng nh v bng cng ngh bluetooth l h thng cung cp thng tin v mt a im da trn v tr ca ngi dng. H thng ny mang li li ch cho ngnh du lch, chng hn khi mt du khch n mt a im tham quan, h thng sau khi nhn bit c v tr ca du khch s t ng hin th cc thng tin tng ng. H thng ny gip khch du lch c th khm ph thnh ph mt mnh m khng cn hng dn vin du lch.

H thng nh v GPS cng c th ng dng vo mc ch ny, tuy nhin mt h thng GPS nh vy c gi cao hn nhiu. Hn na vic nh v chnh xc l khng cn thit, yu t duy nht yu cu l thit b nm trong phm vi ca mt trm c s (~10m). Vi vic trang b mt h thng cung cp thng tin nh c h tr nh v bng cng ngh Bluetooth s thc y v gp phn nng cao dch v du lch, em li hiu qu kinh t cao.

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TNG KT

Lun vn thc thi thnh cng mt h thng nh v bng cng ngh Bluetooth. Qua mt qu trnh tm hiu cng ngh Bluetooth cng vi cc phng php nh v bng sng radio, ngi thc hin ti ny chn ra c mt h thng gm phn mm v phn cng ph hp, d dng trong vic trin khai thc t.

H thng thc nghim c tin hnh trn nn tng my tnh (laptop) tch hp tnh nng Bluetooth,v phn mm thc thi l Visual Studio 6.0 C++ cng vi b pht trin phn mm min ph t Broadcom.

Da vo nguyn l tng quan gia chi s cng tn hiu v khong cch gia hai thit b thu pht, h thng a ra mt c s d liu biu th mi tng quan ny v c lng c khong cch tng ng. y vic x l s liu bao gm vic dng cc hm xp xi a thc bc 3 v phng php c lng binh phng ti thiu. Thc nghim cho thy phng php ny mang li kt qu kh tt vi sai s chp nhn c (~2m).

C mt s kh khn gp phi khi thc thi h thng ny. Th nht l do quan h gia chi s cng tn hiu v khong cch tng ng khng tuyn tnh, mt khc, tnh nng iu khin cng sut cng tc ng ti chi s ny, do vy tin cy trong biu din mi tng quan gia chi s cng tn hiu v khong cch chi mang tnh tng i. Th hai l do cc yu t nh nhiu, a ng hay che khut lm cho chi s RSSI thng ging mnh d vi cng mt v tr o v iu kin o. iu ny cn phi c khc phc bng cch ly mt mu ln, dn n tng thi gian o cho mi v tr.

Cui cng, mt h thng nh v c xut nhm p ng cc yu cu trin khai trong thc tin. H thng ny mi dng li tng v cn nhng nghin cu tip theo c th thc thi hon chinh. Mt h thng nh vy, nu xy dng thnh cng, s em li nhiu li ch thit thc trong i sng cng nh an ninh quc phng.

43

TI LIU THAM KHO

Ting Vit

1. o Qu Thi An Trn Th M Hnh (2005), Tm hiu cng ngh Bluetooth v vit ng dng minh ha, Lun vn c nhn tin hc, Trng i hc Khoa hc t nhin.

Ting Anh

2. Timothy M. Bielawa (2005), Position Location of Remote Bluetooth Devices, Virginia Polytechnic Institute and State University Blacksburg, VA

3. Hussein Fadlallah, Reda Haidar, Samer Khattab (2006), Bluetooth Based Location Estimation for Mobile Applications, American University of Beirut

4. Silke Feldmann, Kyandoghere Kyamakya, Ana Zapater, Zighuo Lue, An indoor Bluetooth-based positioning system: concept, Implementation and experimental

evaluation, Institute of Communications Engineering, Appelstr. 9A, D-30167

Hanover.

5. Nicholas A. Hall, VC++ Widcomm Tutorial, http://controllingtheinter.net 6. Samantha Knights (2004), A Comparative Study of Two Bluetooth APIs for

Implementation in an Automated Wireless Identification System (AWIS),

Bachelor of Science (Honours) of Rhodes University

7. M.P. Kodde (2005), Bluetooth Communication and Positioning For Location based Services, Msc. Geodetic Engineering, TU-Delft.

8. Dr. Zeev Weissman (2004), White paper, Indoor Location, Tadlys Ltd. 9. WIDCOMM, Inc. (2002), Bluetooth for Windows - DK API Reference Guide,

San Diego, CA

10. Wikipedia, http://en.wikipedia.org 11. Sheng Zhou and John K. Pollard (2006), Position Measurement using

Bluetooth, IEEE Transactions on Consumer 558 Electronics, Vol. 52, No. 2,

MAY 2006

MC LC BNG K HIU CC CH VIT TTDANH MC CC HNH VDANH MC CC BNGM UChng 1 GII THIU TNG QUAN V BLUETOOTH 1.1. Khi nim Bluetooth 1.2. Lch s hnh thnh v pht tri n ca Bluetooth. 1.3. Cc c im ca Bluetooth 1.4. ng dng ca Bluetooth. Chng 2 K THUT BLUETOOTH . 2.1. Cc khi nim dng trong cng ngh Bluetooth.2.1.1. Master Unit2.1.2. Slaver Unit2.1.3. Piconet2.1.4. Scatternet:2.1.5. Kt ni theo kiu ad hoc 2.1.7. Trng thi ca thit b Bluetooth2.2. Cch thc hot ng ca Bluetooth. 2.3. Cc tng giao thc trong Bluetooth. Chng 3 CC PHNG PHP NH V 3.1. Thi gian sng ti3.2. Sai khc ca thi gian sng ti3.3. Gc sng ti 3.4. Nhn dng cell 3.5. Mc cng sut thu Chng 4 H THNG NH V BNG BLUETOOTH4.1. Thit k ca h thng nh v bng Bluetooth 4.1.1. Nguyn l hot ng ca h thng. 4.1.2. Widcomm Bluetooth SDK 4.2. Thc thi h thng 4.2.1. Phn cng v phn mm 4.2.2. Lp trnh ng dng nh v 4.3. Kt qu thc nghim v nh gi 4.3.1. Xy dng d liu tng quan gia RSSI v khong cch. 4.3.2. Xc nh v tr t c s d liu4.4. Mt h thng nh v xut trong tng lai 4.4.1. Yu cu ca mt h thng nh v bng Bluetooth 4.4.2. H thng nh v xut 4.4.3. ng dng ca h thng nh v bng cng ngh Bluetooth TNG KTTI LIU THAM KHO