Mang Cam Bien Khong Day

HC VIN CNG NGH BU CHNH VIN THNG

Khoa K thut in t I

**********

Ths. V Anh o - Ths. Trn Th Thc Linh

Bi ging:

MNG CM BIN KHNG DY

H ni, 7/2010

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MC LC

MC LC .................................................................................................................................. 2 LI NI U ............................................................................................................................ 6 DANH MC CC HNH V .................................................................................................... 8 DANH MC BNG BIU ...................................................................................................... 11 CC THUT NG VIT TT ............................................................................................... 12 CHNG 1. GII THIU CHUNG ....................................................................................... 17

1.1 C s h tng cho mng cm bin khng dy ................................................................ 17 1.2 Mng cm bin khng dy v ng dng ......................................................................... 19 1.3 Nhng kh khn ca mng cm bin khng dy ............................................................ 26

1.3.1 Cc yu cu k thut ................................................................................................ 26 1.3.2 Cc k thut yu cu ................................................................................................ 28

1.4 Ti sao mng cm bin li khc vi cc mng khc? ..................................................... 29 1..4.1 Mng Ad hc di ng v WSN .............................................................................. 29 1.4.2 Fieldbus and WSN ................................................................................................... 32

1.5 Cc k thut cho WSN ................................................................................................... 33 CU HI N TP CHNG 1 ............................................................................................. 34 CHNG 2. KIN TRC NT N .................................................................................... 35

2.1 Cc b phn phn cng .................................................................................................. 35 2.1.1 Tng quan phn cng ca nt cm bin .................................................................. 35 2.1.2 B iu khin ........................................................................................................... 36 2.1.3 B nh ..................................................................................................................... 38 2.1.4 Thit b lin lc ........................................................................................................ 38 2.1.5 Cc cm bin v c cu chp hnh .......................................................................... 46 2.1.6 Ngun cung cp ca cc nt cm bin .................................................................... 47

2.2 Tiu th nng lng ca cc nt cm bin ..................................................................... 48 2.2.1 Cc trng thi hot ng vi mc tiu th cng sut khc nhau. ............................ 48 2.2.2 Tiu th nng lng b vi x l .............................................................................. 50 2.2.3 B nh ..................................................................................................................... 52 2.2.4 Cc b thu pht v tuyn ......................................................................................... 52 2.2.5 Mi quan h gia tnh ton v lin lc .................................................................... 54 2.2.6 Tiu th nng lng ca cc cm bin v c cu chp hnh ................................... 55

2.3 Cc h iu hnh v mi trng thc hin ..................................................................... 55 2.3.1 Cc h iu hnh nhng........................................................................................... 55 2.3.2 M hnh lp trnh v cc giao din lp trnh ng dng ............................................ 56 2.3.3 Cu trc h iu hnh v ngn xp giao thc .......................................................... 58 2.3.4 Nng lng ng v qun l nng lng ................................................................ 59

2.4 Mt s v d ca nt cm bin ........................................................................................ 60 2.4.1 H Mica Mote .......................................................................................................... 60 2.4.2 Cc nt EYES .......................................................................................................... 60

2.4.3 Btnode ...................................................................................................................... 61

2.5 Kt lun .......................................................................................................................... 61 CU HI N TP CHNG 2 ............................................................................................. 63 CHNG 3. KIN TRC MNG ......................................................................................... 64

3.1 Mng cm bin ............................................................................................................... 64 3.1.1 Ngun v b cha n ............................................................................................. 64 3.1.2 Mng mt bc nhy v a bc nhy ................................................................... 65 3.1.3 a b cha v ngun ............................................................................................... 66 3.1.4 Ba loi chuyn ng ................................................................................................ 66

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3.2 Cc mc tiu ti u v h s cht lng......................................................................... 68 3.2.1 Cht lng dch v .................................................................................................. 68 3.2.2 Hiu qu nng lng ............................................................................................... 69 3.2.3 Kh nng m rng ................................................................................................... 70 3.2.4 Tnh bn vng .......................................................................................................... 70

3.3 Nguyn tc thit k WSN ............................................................................................... 70 3.3.1 T chc phn b ...................................................................................................... 70 3.3.2 X l trong mng ..................................................................................................... 71 3.3.3 Tnh chnh xc v tin cy .................................................................................... 73 3.3.4 Tp trung d liu ..................................................................................................... 73 3.3.5 Khai thc thng tin v tr .......................................................................................... 74 3.3.6 Khai thc cc m hnh hot ng ............................................................................ 75 3.3.7 Giao thc da trn phn t v ti u lp giao nhau ................................................ 75

3.4 Giao din dch v ca WSN ........................................................................................... 75 3.4.1 Cu trc ca giao din ngn xp giao thc/ng dng ............................................. 75 3.4.2 Cc yu cu cho giao din dch v ca WSN. ......................................................... 76

3.5 Khi nim cng vo/ra .................................................................................................... 77 3.5.1 S cn thit ca cc cng vo/ra ............................................................................. 77 3.5.2 Giao tip WSN vi Internet ..................................................................................... 78 3.5.3 Giao tip Internet-WSN ........................................................................................... 79 3.5.4 Giao tip gia cc WSN. ......................................................................................... 80

3.6 Kt lun .......................................................................................................................... 80 CU HI N TP CHNG 3 ............................................................................................. 82 CHNG 4. LP VT L ..................................................................................................... 83

4.1 Gii thiu ........................................................................................................................ 83 4.2 Knh v tuyn v c s truyn tin .................................................................................. 83

4.2.1 Cp pht tn s ........................................................................................................ 83 4.2.2 iu ch v gii iu ch ......................................................................................... 85 4.2.3 Cc nh hng ca truyn sng v nhiu ................................................................ 88 4.2.4 Cc m hnh knh .................................................................................................... 93

4.2.5 Cng ngh tri ph .................................................................................................. 94 4.2.6 ng b v truyn gi tin ........................................................................................ 95 4.2.7 Cht lng knh v tuyn v cc php o ci thin ........................................... 97

4.3 Lp vt l v thit k b thu pht trong WSN. ............................................................... 98 4.3.1 S dng nng lng ................................................................................................. 99 4.3.2 La chn s iu ch .......................................................................................... 99 4.3.3 Antenna .................................................................................................................. 100

CU HI N TP CHNG 4 ........................................................................................... 101 CHNG 5. CC GIAO THC MAC ................................................................................ 102

5.1. Cc nguyn tc c bn ca cc giao thc MAC (khng dy) ..................................... 102 5.1.1 Cc yu cu v rng buc thit k cho cc giao thc MAC khng dy. ............... 102 5.1.2 Phn loi cc giao thc MAC ................................................................................ 104 5.1.3 Cc giao thc MAC cho WSN .............................................................................. 109

5.2 Cc giao thc h s lp y thp v khi nim thc dy (wakeup).............................. 110 5.2.1 Cu hnh mng v vn qun l nng lng ...................................................... 111 5.2.2 S-MAC .................................................................................................................. 113

5.2.3 Giao thc thit b trung gian .................................................................................. 116 5.3 Cc giao thc theo kiu cnh tranh .............................................................................. 117

5.3.1 Cc giao thc CSMA ............................................................................................. 118 5.3.2 PAMAS ................................................................................................................. 118

5.4 Cc giao thc da trn lch trnh .................................................................................. 120 5.4.1 LEACH .................................................................................................................. 120

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5.4.2 SMACS .................................................................................................................. 122

5.5 Giao thc MAC ca IEEE 802.15.4 ............................................................................. 124 5.5.1 Kin trc mng, loi v vai tr ca nt.................................................................. 126 5.5.2 Kin trc ca siu khung ....................................................................................... 127 5.5.3 Giao thc Slotted CSMA-CA ................................................................................ 128

5.6 Tng kt ........................................................................................................................ 129 CU HI N TP CHNG 5 ........................................................................................... 130 CHNG 6. CC GIAO THC LP LIN KT ............................................................... 131

6.1 Cc nhim v v yu cu c bn .................................................................................. 131 6.2 Gim st li ................................................................................................................... 132

6.2.1 Nguyn nhn v cc c tnh ca sai s truyn dn .............................................. 132 6.2.2 Cc k thut ARQ ................................................................................................. 133 6.2.3 Cc k thut FEC ................................................................................................... 138 6.2.4 Cc s lai .......................................................................................................... 143 6.2.5 iu khin cng sut ............................................................................................. 145 6.2.6 iu khin li ........................................................................................................ 145

6.3 nh dng khung .......................................................................................................... 146 6.3.1 Cc s tng thch ............................................................................................ 149 6.3.2 Cc s kim tra tng trung gian ........................................................................ 150 6.3.3 Kt hp ti u kch thc gi tin v FEC ............................................................. 152

6.4 Qun l tuyn. .............................................................................................................. 153 6.4.1 Cc c tnh ca cht lng tuyn ......................................................................... 153 6.4.2 c lng cht lng tuyn .................................................................................. 155

6.5 Tng kt ........................................................................................................................ 157 CU HI N TP CHNG 6 ........................................................................................... 158 CHNG 7. T TN V NH A CH...................................................................... 159

7.1 Cc nguyn tc c bn .................................................................................................. 159 7.1.1 S dng cc a ch v cc tn trong cc mng (cm bin) ................................... 159 7.1.2 Nhim v qun l a ch ....................................................................................... 160 7.1.3 S duy nht ca cc a ch ................................................................................... 161 7.1.4 Phn phi v n nh a ch .................................................................................. 162 7.1.5 nh a ch phn tip u .................................................................................... 163

7.2 Qun l tn v a ch trong cc mng cm bin khng dy ........................................ 164 7.3 n nh cc a ch MAC ............................................................................................. 165 7.4. nh a ch theo a l v da trn ni dung ............................................................. 167

7.4.1 nh a ch da trn ni dung ............................................................................. 168 7.4.2 nh a ch theo a l ......................................................................................... 171

7.5 Tng kt ........................................................................................................................ 172 CU HI N TP CHNG 7 ........................................................................................... 173 CHNG 8. NG B THI GIAN .................................................................................. 174

8.1 Gii thiu v vn ng b thi gian .................................................................. 174 8.1.1 S cn thit ca vic ng b thi gian trong cc mng cm bin khng dy ...... 174 8.1.2 Cc kha nt v vn v chnh xc................................................................ 175 8.1.3 Cc c im v cu trc ca cc thut ton ng b thi gian ............................ 177 8.1.4 ng b thi gian trong cc mng cm bin khng dy ....................................... 179

8.2 Cc giao thc da trn ng b my pht/ my thu .................................................... 180 8.2.1 Giao thc ng b thi gian hng nh - Lightweight time synchronization protocol (LTS) .............................................................................................................................. 180

8.2.2 Lm th no tng chnh xc v c lng lch ...................................... 185 8.2.3 Giao thc ng b thi gian cho cc mng cm bin (TPSN) .............................. 188

8.3 Cc giao thc da trn s ng b my thu/my thu ................................................... 191 8.3.1 S ng b qung b tham kho (RBS - Reference broadcast synchronization) .. 191

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8.3.2 Phn tng tham chiu ng b thi gian (HRTS - Hierarchy referencing time synchronization) ............................................................................................................. 197

CU HI N TP CHNG 8 ........................................................................................... 201 CHNG 9. NH V V XC NH V TR ................................................................... 202

9.1 Cc c im ca quy trnh nh v v xc nh v tr ................................................. 202 9.2 Cc phng php c th ............................................................................................... 204

9.2.1 Phng php da trn s gn gi .......................................................................... 204 9.2.2 Php c tam gic (triangulation) v php o ba cnh tam gic (Trilateration) .... 204 9.2.3 Phn tch cnh ........................................................................................................ 208

9.3 C s ton hc cho cc vn cnh ............................................................................. 209 9.3.1 Gii php vi ba nt neo v sa li cc gi tr khong cch ................................. 209 9.3.2 Gii quyt vn cc li khong cch .................................................................. 210

9.4 Xc nh v tr trong cc mi trng a bc nhy ...................................................... 211 9.4.1 S kt ni trong mt mng a bc nhy .............................................................. 211 9.4.2 Vic c lng phm vi a bc nhy.................................................................. 212 9.4.3 a bn cng tc v lp ........................................................................................... 213 9.4.4 M t v truyn lan vic xc nh v tr theo xc sut ........................................... 215

9.5 Tng kt ........................................................................................................................ 216 CU HI N TP CHNG 9 ........................................................................................... 217 CHNG 10: IU KHIN CU TRC LIN KT MNG (TOPOLOGY) .................. 218

10.1.1 Cc ty chn cho vic iu khin cu trc lin kt mng ................................... 219 10.1.2 Cc kha cnh ca cc thut ton iu khin cu trc lin kt mng .................. 221

10.2 iu khin cu trc lin kt mng trong cc mng phng iu khin cng sut .... 223 10.2.1 Mt s cc kt qu phc tp ................................................................................ 224 10.2.2 Cc gii hn ca cc tham s ch cht ................................................................ 225 10.2.3 Vi cu trc v giao thc v d ............................................................................ 227

10.3 Cc mng phn tng xng sng ............................................................................. 229 10.3.1 ng c v nh ngha ......................................................................................... 229 10.3.2 Mt s xp x phn tn ........................................................................................ 234

10.4 Mng phn tng phn nhm (clustering) ................................................................ 237 10.4.1 nh ngha cc phn nhm .................................................................................. 237 10.4.2 Mt tng c bn xy dng cc tp hp c lp ......................................... 240 10.4.4 Kt ni cc phn nhm ........................................................................................ 241 10.4.5 Quay cc ch huy phn nhm .............................................................................. 242

CU HI N TP CHNG 10 ......................................................................................... 243 TI LIU THAM KHO ...................................................................................................... 244

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LI NI U

Nhng tin b gn y trong thng tin v tuyn v in t cho php pht trin cc

mng cm bin gi thnh thp. Mng cm bin c th c s dng trong cc ng dng khc

nhau nh chm sc sc kho, trong qun s hoc s dng trong gia nh. Mng cm bin

khng dy (WSN) bao gm cc nt nh c kh nng cm bin, tnh ton v trao i thng tin

v tuyn. Mt s giao thc chn ng, qun l nng lng v trao i d liu c thit

k cho WSN vi yu cu quan trng nht l tit kim c nng lng. Cc giao thc chn

ng trong WSN c th khc nhau tu theo ng dng v cu trc mng. Ni chung, cc giao

thc chn ng c chia thnh 3 loi da vo cu trc mng: ngang hng, phn cp hoc

da vo v tr. Ngoi ra, nhng giao thc ny c th c phn loi da theo a ng, yu

cu, hi/p, QoS v lin kt tu thuc vo ch hot ng.

Mng cm bin khng dy (WSN) c th hiu n gin l mng lin kt cc nt vi

nhau bng kt ni sng v tuyn , trong cc nt mng thng l cc (thit b) n gin,

nh gn, gi thnh thp ... v c s lng ln, c phn b mt cch khng c h thng trn

mt din tch rng, s dng ngun nng lng hn ch (pin), c thi gian hot ng lu di

(vi thng n vi nm) v c th hot ng trong mi trng khc nghit (cht c, nhim,

nhit ...).

Cc nt mng thng c chc nng cm ng, quan st mi trng xung quanh, theo di

hay nh v cc mc tiu c nh hoc di ng ... Cc nt giao tip ad-hoc vi nhau v truyn

d liu v trung tm mt cch gin tip bng k thut a bc nhy.

Lu lng d liu lu thng trong WSN thng thp v khng lin tc. Do vy tit

kim nng lng, cc nt cm bin thng c nhiu trng thi hot ng v trng thi ngh

khc nhau. Thng thng thi gian mt nt trng thi ngh ln hn trng thi hot ng

rt nhiu.

Nh vy, c trng c bn nht phn bit mng cm bin v mng khng dy khc

chnh l gi thnh, mt nt mng, phm vi hot ng, cu hnh mng, lu lng d liu,

nng lng tiu th v thi gian trng thi hot ng.

Bi ging Mng cm bin khng dy gm 10 chng: 6 chng u do Ths. V Anh

o bin son v 4 chng sau do Ths. Trn Th Thc Linh bin son. Cun sch gii thiu

cho bn c nhng kin thc c bn v WSN nh cc tiu ch khi xy dng mt WSN v cc

c im ca WSN nh lp MAC, lp lin kt d liu, cch t tn v nh a ch, c th:

Chng 1: Gii thiu chung

Chng 2: Kin trc nt n

Chng 3: Kin trc mng

Chng 4: Lp vt l

Chng 5: Cc giao thc MAC

Chng 6: Cc giao thc lp lin kt

Chng 7: t tn v nh a ch

Chng 8: ng b thi gian

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Chng 9: nh v v xc nh v tr

Chng 10: iu khin cu trc lin kt mng

Tuy nhin, do thi gian bin son c hn nn cun bi ging cn c th c nhng thiu

st, rt mong c bn c gp . Cc kin phn hi xin gi v B mn K thut in t -

Khoa K thut in t I, Hc vin Cng ngh Bu chnh Vin thng.

Xin trn trng gii thiu!

Nhm tc gi

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DANH MC CC HNH V

Hnh 1.1 Mng im im ..................................................................................................... 21 Hnh 1.2 Mng im a im ................................................................................................ 21 Hnh 1.3 Mng a im a im ........................................................................................... 22 Hnh 1.4 S nguyn l mng chia s kt ni dng ad hoc ................................................... 30 Hnh 2.1 Cu trc phn cng ca nt cm bin ....................................................................... 36 Hnh 2.2 u cui RF ............................................................................................................... 43 Hnh 2.3 Tit kim nng lng v chi ph cho cc ch ng ................................................ 49 Hnh 2.4 Nng lng/hot ng vi di in p ng trn Intel StrongARM-1100 ................ 51 Hnh 2.5 Hai m hnh khng tng thch vi h iu hnh WSN ........................................... 56 Hnh 2.6 M hnh lp trnh da trn s kin ............................................................................ 57 Hnh 2.7. Nt Mica ................................................................................................................... 60

Hnh 2.8 Nt cm bin EYES ................................................................................................... 61 Hnh 2.9 Btnode ........................................................................................................................ 61

Hnh 3.1 Ba loi b cha trong mt mng cm bin mt bc nhy n gin ........................ 64 Hnh 3.2 Mng a bc nhy .................................................................................................. 65 Hnh 3.3 Nhiu ngun/nhiu b cha ...................................................................................... 67 Hnh 3.4 B cha di ng dch chuyn qua mng cm bin .................................................... 67 Hnh 3.5 Vng cc cm bin tm kim s kin ........................................................................ 68 Hnh 3.6. V d tp hp ............................................................................................................ 72 Hnh 3.7 Hai la chn giao din dch v vi ngn xp giao din ........................................... 76 Hnh 3.8 WSN vi nt cng vo ra, c th truy cp n i tng xa qua Internet ............. 78 Hnh 3.9 Giao tip WSN Internet ......................................................................................... 79 Hnh 3.10 Giao tip Internet-WSN .......................................................................................... 79 Hnh 3.11 Kt ni gia hai WSN qua Internet ........................................................................ 80 Hnh 4.1 Ph in t - tn s v tuyn .................................................................................... 84 Hnh 4.2 V d v ASK .......................................................................................................... 86 Hnh 4.3 V d v PSK ............................................................................................................. 87 Hnh 4.4 V d v FSK ............................................................................................................. 87 Hnh 4.5 M t hin tng truyn sng .................................................................................... 88 Hnh 4.6 Truyn sng a ng ............................................................................................. 89 Hnh 4.7 Tc li bit ca PSK v FSK nh phn c tch sng nht qun ........................ 92 Hnh 4.8 V d v tri ph dy trc tip ................................................................................... 95 Hnh 4.9 V d v ly mu v ng b .................................................................................... 97 Hnh 5.1 Tnh hung u cui n (cc vng trn l di truyn dn v nhiu) ....................... 103 Hnh 5.2 Bt tay RTS/CTS trong IEEE 802.11 ...................................................................... 108 Hnh 5.3 Hai vn trong bt tay RTS/CTS .......................................................................... 108 Hnh 5.4 S thc dy nh k ............................................................................................ 111 Hnh 5.5 Chu trnh lm vic STEM ca mt nt n ............................................................. 112 Hnh 5.6 Nguyn l S-MAC ................................................................................................... 113

Hnh 5.7 Khung S-MAC v t NAV .................................................................................... 115 Hnh 5.8 Giao thc thit b trung gian vi cc b ho gii khng rng buc ......................... 116 Hnh 5.9 Nhiu gia cc nhm ............................................................................................... 121 Hnh 5.10 T chc ca chu k LEACH ................................................................................. 122 Hnh 5.11 SMACS: ci t tuyn cho hai nt n ................................................................. 123 Hnh 5.12 Cc ng dng ca Zigbee ...................................................................................... 125 Hnh 5. 13 Cc kiu mng ca ZigBee ................................................................................... 126 Hnh 5.14 Cu trc siu khung ca IEEE 802.15.4 ................................................................ 127 Hnh 5.15 Bt tay gia b iu phi v thit b khi thit b tm kim gi tin ......................... 129 Hnh 6.1 Format ca mt khung lp vt l IEEE 802.11/802.11b ......................................... 133

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Hnh 6.2 nh dng gi tin DLL ......................................................................................... 134 Hnh 6.3 V tr ca FEC trong chui gi/nhn; thc hin m ho v gii m FEC................ 138 Hnh 6.4 Chi ph nng lng ca m Reed-Solomon vi kch thc khi v t l m khc nhau .......................................................................................................................... 140

Hnh 6.5 Hot ng ca m chp ........................................................................................... 141 Hnh 6.6 Tiu th nng lng trong khi truyn 10 kB d liu qua tuyn vi suy hao ng truyn 70 dB theo cc s m ho khc nhau ..................................................................... 142 Hnh 6.7 Nng lng s dng truyn thnh cng 1 bit d liu vi cc t khc nhau ......... 144 Hnh 6.8 Nng lng/bit hu dng cho d liu c kch thc u = 100 v u = 500 vi t l li bit khc nhau ........................................................................................................................... 148

Hnh 6.9 Nng lng/bit hu dng vi t l li bit p c nh v kch thc d liu u thay i .................................................................................................. 148 Hnh 6.10 nh khung truyn thng vi header/d liu/kim tra tng so vi nh khung kiu kim tra tng trung gian ......................................................................................................... 151 Hnh 6.11 Tiu th nng lng v tr mong i ca cc gi thng tin c kch thc khc nhau L (theo byte) v cc t l li trng thi tt khc nhau. ............................................................ 153 Hnh 6.12 ng cong biu th xc sut nhn tin cho cc gi tin c to ra t nt trung tm vi hai cng sut khc nhau.................................................................................................... 154 Hnh 6.13 T l nhn tin cc b thu c khong cch khc nhau .......................................... 155 Hnh 6.14 M t vn c lng ......................................................................................... 156 Hnh 7.1 V d cho s phn chia ca mng ........................................................................... 161 Hnh 7.2 V d cho s phn chia ca mng ........................................................................... 163

Hnh 7.3 Xc sut sinh nht m k ngoi 142n trm la chn cc a ch ngu nhin khng c cc xung t ....................................................................................................................... 166 Hnh 8.1 Xc nh gc ti ca mt s kin m thanh xa bng mt mng cc cm bin m thanh. ...................................................................................................................................... 174

Hnh 8.2 Mt phn s ca hot ng trong ng b my pht/my thu ........................... 182 Hnh 8.3 LTS a bc nhy phn tn ..................................................................................... 185 Hnh 8.4 S ng b my pht/my thu trong TPSN ............................................................. 190 Hnh 8.5 V d RBS: hai nt i v j v mt my pht R .......................................................... 192 Hnh 8.6 Nhiu min qung b ............................................................................................... 196 Hnh 8.7 Tch hp gi tin, chuyn tip v bin i nhn thi gian ....................................... 196 Hnh 8.8 ng b thi gian: ng b trong mt min qung b n l ................................. 199 Hnh 9.1 Xc nh v tr ca cc nt cm bin vi s h tr t mt s cc im neo; khng phi tt c cc nt l cn thit trong giao tip vi tt c cc nt neo. .................................... 203 Hnh 9.2 Php c tam gic bi ba vng trn giao nhau ........................................................ 205 Hnh 9.3 Bn cht ngu nhin ca vic nh x cc gi tr RSSI ti cc khong cch [25]. ... 206 Hnh 9.4 Gc to bi hai nt neo ............................................................................................ 208 Hnh 9.5 c lng khong cch Euclidean trong s vng mt ca kt ni trc tip [22] ... 213 Hnh 9.6 a bn lp: cc nt A, B, v C c th xc nh cc v tr ca n trong vi php lp (cc mi tn m ch cc ng ni m phm vi ca chng c s dng trong mt php lp cho) .................................................................................................................................... 214 Hnh 9.7 Cc kch bn cn phi bn cho a bn lp ............................................................... 215 Hnh 9.8 S x l theo xc sut cc v tr ca nt [25] .......................................................... 216 Hnh 10.1 Cu trc lin kt mng trong mt mng cm bin khng dy c trin khai vi mt cao. .............................................................................................................................. 219 Hnh 10.2 Cu trc lin kt mng tha hn sau khi gim cng sut pht. ............................. 220 Hnh 10.3 Gii hn cu trc lin kt mng bng cch s dng mt xng sng. .................. 220 Hnh 10.4 S dng cc phn nhm chia mt s thnh cc phn. ................................. 221 Hnh 10.5 Mc tiu ti u ha iu khin cu trc cu trc lin kt mng: xc sut ca mng c kt ni so vi kch thc trung bnh ca thnh phn cu thnh ln nht. ..................... 223

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Hnh 10.6 Cu trc ca RNG: vng ti phi khng cha cc nt no khc cho hai nt c kt ni. .......................................................................................................................................... 227 Hnh 10.7 Minh ha vng tip sng ca nt i vi nt r (vng ti ch th cc im ni m tip sng c hiu sut cao hn thay v truyn thng trc tip) ...................................................... 228 Hnh 10.8 Hai kch bn lm cch no xy dng cc nt ln cn cho nt i ngoi cc vng tip sng vi cc nt khc. ............................................................................................................ 229 Hnh 10.9 Minh ha mt thut ton tp hp chi phi n gin da trn vic pht trin mt cy (cc ng nt m ch cc cnh trong cy, cc nt mu en to thnh tp hp chi phi. .... 231 Hnh 10.10 S v d mt la chn khm ph tham vng da trn li ch mt bc b tht bi .................................................................................................................................... 232 Hnh 10.11 Cu trc tp hp chi phi tham vng vi v khng vi vic nhn v pha trc. 233 Hnh 10.12 Tnh n s cn thit kt ni hai nt mu en ph v mi quan h gia hai nt A v B. .................................................................................................................................... 234

Hnh 10.13 S v d cho vic nh du cc nt vi cc nt ln cn khng c kt ni. 236 Hnh 10.14 Mt s v d vi mt tp hp c lp cc i ................................................ 238 Hnh 10.15 Tp hp c lp cc i to ra cc phn nhm chng nhau hoc khng chng nhau ........................................................................................................................................ 239

Hnh 10.16 Hai phn nhm c ni bi hai cng chnh phn tn ........................................ 239 Hnh 10.17 Thut ton c bn xc nh cc tp hp c lp, s dng cc s nhn dng nt nh xp hng (cc nt mu trng l cha c xc nh, cc nt mu en l cc ch huy phn nhm, cc nt mu xm l cc thnh vin phn nhm. .......................................................... 241

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DANH MC BNG BIU

Bng 2.1 Mt nng lng ca cc loi pin chnh v ph khc nhau. .................................. 47 Bng 2.2 Mt s tham s v tiu th nng lng ca b thu pht (N/A : khng cho php) .... 54 Bng 2.3 V d v mt s c tnh ca cc cm bin ............................................................... 55 Bng 4.1 Mt s di ISM .......................................................................................................... 84 Bng 6.1 S lng d liu k tng ng vi s lng bit c th hiu chnh t khc nhau trong khi n=1023 bit i vi m BCH ........................................................................................... 144 Bng 7.1 Tp hp cc ton t ................................................................................................ 169

12

CC THUT NG VIT TT

Ch vit tt Ting Anh Ting Vit

ADC Analog/Digital Convert B bin i tng t/s

ANDA Ad hoc Network Design Algorithm Thut ton thit k mng Ad hc

API Application Programming Interface Giao din lp trnh ng dng

ARQ Automatic Repeat Request Yu cu lp li t ng

ASIC Application-Specific Integrated

Circuit

Mch tch hp chuyn dng

ASK Amplitude Shift Keying Kho dch bin

AWGN Additive White Gaussian Noise Tp m Gaussian cng sinh

BCH Bose Chaudhuri Hocquenghem M BCH

BER Bit-Error Rate T s li bit

BPSK Binary Phase Shift Keying Kho dch pha nh phn

BSC Binary Symmetric Channel Knh i xng nh phn

CCA Clear Channel Assessment Kim tra knh truyn c ri khng

CCK Complementary Code Keying iu ch kho m b

CDMA Code Division Multiple Access a truy cp phn chia theo m

CIR Carrier to Interference Ratio T s tn hiu/nhiu

CPU Central Processing Unit Khi x l trung tm

CRC Cyclic Redundancy Check Kim tra tnh d tun hon

CSMA Carrier Sense Multiple Access a truy cp cm nhn sng mang

CTS Clear To Send Chc chn gi

DAC Digital/Analog Converter B bin i s/tng t

DAD Duplicate Address Detection Pht hin a ch p

DBPSK Differential Binary Phase Shift

Keying

Kho dch pha nh phn vi sai

DCF Distributed Coordination Function Hm to phn b

13

DHT Distributed Hash Table Bng bm phn b

DLL Data Link Layer Lp lin kt d liu

DPM Dynamic Power Managemen Qun l nng lng ng

DQPSK Differential Quaternary Phase Shift

Keying

Kho dch pha t phn vi sai

DSP Digital Signal Processor B x l tn hiu s

DSSS Direct Sequence Spread Spectrum Tri ph dy trc tip

DVS Dynamic Voltage Scaling Di in p ng

EEPROM Electrically Erasable Programmable

Read-Only Memory

B nh ch c lp trnh c xo bng

in

EHF Extremely High Frequency Tn s cc cao

FDMA Frequency Division Multiple

Access

a truy cp phn chia theo tn s

FEC Forward Error Correction Hiu chnh phng li

FFD Full Function Device Thit b chc nng y

FFT Fast Fourier Transform Bin i Fourier nhanh

FHSS Frequency Hopping Spread

Spectrum

Tri ph nhy tn

FIFO First In First Out Vo trc Ra trc

FPFA Field-Programmable Gate Array Mng cng logic kh trnh

FSK Frequency Shift Keying Kho dch tn

GPS Global Positioning System H thng nh v ton cu

GTS Guaranteed Time Slot Khe thi gian m bo

IEEE Institute of Electrical and

Electronics Engineers

Vin cng ngh k thut in -in t

IF Intermediate Frequency Tn s trung gian

ISI InterSymbol Interference Nhiu lin k hiu

ISM Industrial, Scientific, and Medical

Cng nghip, khoa hc v y t

14

LEACH Low-Energy Adaptive Clustering

Hierarchy

Phn cp nhm thch ng cng sut

thp

LED Light-Emitting Diode Diode pht quang

LNA Low Noise Amplifier B khuch i tp m thp

LOS Line Of Sight ng nhn thng

MAC Medium Access Control iu khin truy cp mi trng

MANET Mobile Ad Hoc Network Mng ad hc di dng

MCDS Minimum Connected Dominating

Set

Tp hp chi phi c ni nh nht

MDS MultiDimensional Scaling Chia t l a chiu

MEMS MicroElectroMechanical System H thng vi c in t

MLE Maximum Likelihood Estimation Cc i ho kh nng c lng

tham s

MPDU MAC-layer Protocol Data Unit Khi d liu giao thc lp MAC

NAT Network Address Translation Dch a ch mng

NAV Network Allocation Vector Vector nh v mng

NLOS Non Line Of Sight Khng c ng nhn thng

OOK On-Off-Keying Kho ng m

PAN Personal Area Network Mng c nhn

PA Power Amplifier B khuch i cng sut

PDA Personal Digital Assistant Thit b h tr c nhn k thut s

PHY Physical Layer Lp vt l

PPDU Physical-layer Protocol Data Unit Khi d liu giao thc lp vt l

PPM Pulse Position Modulation iu ch v tr xung

PSD Power Spectral Density Mt ph cng sut

PSK Phase Shift Keying Kho dch pha

QAM Quadrature Amplitude Modulation iu ch bin vung gc

QPSK Quaternary Phase Shift Keying Kho dch pha t phn

15

QoS Quality of Service Cht lng ca dch v

RAM Random Access Memory B nh truy cp ngu nhin

RFD Reduced Function Device Thit b gii hn chc nng

RFID Radio Frequency Identifier B nhn dng tn s v tuyn

RF Radio Frequency Tn s v tuyn

GRT Geography RouTing protocol Giao thc nh tuyn a l

RISC Reduced Instruction Set Computer My tnh c b lnh rt gn

ROM Read-Only Memory B nh ch c

RSSI Received Signal Strength Indicator B ch th cng tn hiu nhn

RS Reed Solomon M Reed Solomon

RTS Request To Send Yu cu gi

SDMA Space Division Multiple Access a truy cp phn chia khng gian

SFD Start Frame Delimiter Bt u du tch khung

SINR Signal to Interference and Noise

Ratio

T s tn hiu/nhiu v tp m

SMACS Self-Organizing Medium Access

Control for Sensor Networks

iu khin truy cp mi trng t t

chc ca cc mng cm bin

SNR Signal-to-Noise Ratio T s tn hiu/tp m

STEM Sparse Topology and Energy

Management

Giao thc cu hnh mng v vn

qun l nng lng

TCP Transmission Control Protocol Giao thc iu khin truyn dn

TDMA Time Division Multiple Access a truy cp phn chia thi gian

TRAMA Traffic-Adaptive Medium Access Truy cp mi trng lu lng thch

ng

UTM Universal Transverse Mercator Cc v tr trong cc ta

UWB UltraWideBand Bng siu rng

VLF Very Low Frequency Tn s rt thp

WLAN Wireless Local Area Network Mng khng dy cc b

16

WPAN Wireless Personal Area Network Mng khng dy c nhn

WRP Wireless Routing Protocol Giao thc nh tuyn khng dy

WSDL Web Service Description Language Ngn ng m t dch v Web

WSN Wireless Sensor Network Mng cm bin khng dy

17

CHNG 1. GII THIU CHUNG

Mc ch ca chng

Cc ng dng phi c nh hnh v xy dng da trn cng ngh m n s dng.

iu ny c bit ng vi mng cm bin khng dy v n c th c xy dng theo cc

cch khc nhau. Chng ny s trnh by khi nim ca mng cm bin khng dy v mt s

ng dng ca n. T cc v d trnh by s phn thnh cc loi hoc cc lp ng dng.

Tip theo l nhng thch thc i vi cc ng dng ny v a ra l do ti sao cng ngh hin

nay khng th tho mn nhng thch thc ny.

Phn cui ca chng l nhng nh gi v cc loi ng dng ny i vi mng cm

bin khng dy v a ra nhng gi v gii php cng ngh cho chng, c phn cng v k

thut mng.

1.1 C s h tng cho mng cm bin khng dy

Mt mng cm bin bao gm s lng ln cc nt cm bin c phn b c bn trong

v bn cnh hin tng. V tr ca cc nt cm bin khng cn phi thit k hoc xc nh

trc. iu ny cho php phn b ngu nhin trong cc a hnh phc tp hoc cc hot ng

tr gip thm ha. iu ny cng c ngha l cc giao thc ca mng cm bin v cc thut

ton phi c kh nng t t chc. Mt c im quan trng khc ca cc mng cm bin l

kh nng phi hp gia cc nt cm bin. Cc nt cm bin c gn mt b x l bn trong.

Thay v gi i s liu th ti nt ch, chng s dng kh nng x l thc hin cc tnh

ton n gin v ch truyn s liu c x l theo yu cu.

Chn ng trong WSN rt kh khn do cc c tnh ring phn bit ca mng ny vi

cc mng v tuyn khc nh cc mng ad-hoc hoc cc mng t bo. Trc ht, do s lng

nt cm bin l kh ln nn khng th xy dng mt quy tc cho a ch ton cc khi trin

khai v phn iu khin cho vic thit lp ID l cao. V vy, cc giao thc da trn IP truyn

thng c th khng p dng c cho WSN. Th hai, khc vi cc mng thng tin ni chung,

hu ht cc ng dng ca mng cm bin yu cu truyn s liu cm bin t nhiu ngun ti

mt nt gc. Th ba, cc nt cm bin b hn ch v cng sut, kh nng x l v dung lng

nh. Th t, trong hu ht cc ng dng, cc nt trong WSN thng c v tr c nh. Tuy

nhin, trong mt s ng dng, cc nt cm bin c th c php di chuyn v thay i v tr

(mc d vi di chuyn rt thp). Th nm, cc mng cm bin thng ph thuc vo ng

dng. Th su, v tr ca cc nt cm bin ng vai tr quan trng v vic la chn s liu

thng da vo v tr. Hin nay cha thch hp cho vic s dng cc phn cng ca h thng

nh v ton cu (GPS) cho mc ch ny. Cc phng php xc nh v tr ca cc nt cm

bin thng da vo cng tn hiu t mt s im xc nh. Cui cng, s liu c la

chn bi cc nt cm bin trong WSN thng da vo hin tng chung, do s c d

tha. Cc giao thc chn ng phi khc phc c d tha ny s dng hiu qu

bng thng. Tm li, phng php chn ng trong WSN cn phi quan tm n cc c

tnh ring ca WSN cng vi cc yu cu v ng dng v cu trc.

Nhn chung, cc thit b tnh ton u phi x l thng tin t cch thc n gin n

18

phc tp. Trong nhiu ng dng, v d nh cc ng dng vn phng, cc thit b tnh ton ny

thng c s dng x l thng tin lin quan n con ngi, nh vy i tng y

quan h gin tip vi mi trng vt l.

Trong mt lp ng dng khc, mi trng vt l li tp trung vo i tng. Tnh ton

c s dng iu khin i tng thng qua cc qu trnh vy l. V d nh iu khiu

khin cc qu trnh ho hc trong nh my iu chnh nhit v p xut. y, qu trnh

tnh ton s c kt hp vi iu khin v n c gi l nhng trong mi trng. Khng

ging nh cc loi h thng trc kia, cc h thng nhng ny thng khng da vo s

tng tc vi con ngi v v th, n c mt s yu cu v mt k thut lm c vic .

Trong cc h thng ln th n c quan h mt thit vi nhim v iu khin.

Cc h thng nhng c bit n v s dng trong mt thi gian di (trn thc t,

trn 98% cc thit b tnh ton s dng nhng). Chng xut hin hng ngy, hng gi

quanh cuc sng ca chng ta v pht trin mt cch nhanh chng. Hu ht cc thit b gia

dng u s dng nhng, v d nh my git, my quay phim, in thoi Trong cc ng

dng ny, h thng nhng da trn s tng tc vi con ngi.

Xu hng cng ngh ny khng ch xut hin trong cc thit b ln nh my git m n

cn c thc hin trong cc thit b nh hn, thm ch trong c hng tp ho. Nhiu thit b

khc nhau s kt hp vi thng tin x l iu khin cc qu trnh vt l v tng tc vi

ngi s dng. Cng ngh ny c a ra bi Marc Weiser. Bng cch tch hp tnh ton v

iu khin trong mt mi trng vt l, m hnh tng tc c bit n y l ngi

ngi, ngi my v my my v cui cng l ngi mi trng vt l. Tng tc vi

mi trng vy l s quan trng hn l ch lm vic vi cc s liu.

thc hin iu ny, yu cu ngoi vic tnh ton v iu khin l thng tin. Tt c

cc ngun tin ny c th chuyn thng tin thnh v tr ca c cu chp hnh hoc ngi s

dng v n c th kt hp li vi nhau to nn mt bc tranh chnh xc v mi trng thc

t khi c yu cu. i vi mt s ng dng, nh cc mng cm bin v c cu chp hnh, rt

d xy dng h thng vi cc cng ngh mng hu tuyn c. Tuy nhin, vi mt s ng

dng, c rt nhiu tr ngi thc hin iu ny nh gi thnh cao (ln n 200 USD/ 1 cm

bin). c bit l trong mt h thng c s thit b rt ln, chng ta c th hnh dung ra c

s phc tp ca n, vn bo dng ng dy, dy dn cn tr s di chuyn ca i tng,

ngn khng cho cm bin/c cu chp hnh li gn i tng iu khin. Do , thng tin v

tuyn gia cc thit b ny, trong nhiu ng dng, l mt yu cu tt yu.

Mt lp mng mi xut hin trong nhng nm gn y, l mng cm bin khng

dy (WSN - Wireless Sensor Network). Mng ny bao gm nhng nt n c th tng tc

vi mi trng bng cch cm bin v iu khin cc tham s vt l. Nhng nt ny cng tc

hon ton vi nhau hon thnh nhim v ca n v mt nt n khng th lm c g v

chng s dng thng tin v tuyn thc hin iu ny. Cc nt thuc mng ny t nht cng

cha mt s php tnh, giao tip v tuyn v c chc nng cm bin hoc iu khin. Mc d

thc cht mng ny bao gm cc c cu chp hnh nhng thut ng mng cm bin khng

dy li l tn gi ph bin. i khi n cn c gi l mng cm bin v c cu chp hnh

khng dy (wireless sensor and actuator network).

19

WSN hu dng khi n dng h tr cho nhiu ng dng thc t khc nhau. Mng ny

tn ti nhiu thch thc trong qu trnh nghin cu v nhiu vn v mt cng ngh v n rt

phc tp. Do khng th c cch duy nht phn loi mt cch r rng cc WSN v cng

khng th tn ti mt gii php thc hin cc yu cu thit k. V d, trong rt nhiu ng

dng ca WSN, cc nt n trong mng khng th d dng kt ni vi ngun cung cp m

phi da vo ngun pin gn trn n. Trong cc ng dng ny, vic s dng nng lng c

hiu qu l nhim v rt quan trng, sao cho n c th hot ng trong thi gian lu nht c

th. Trong mt s ng dng khng c ngun cung cp th cc tham s khc li ng vai tr

quan trng hn, v d nh chnh xc ca kt qu nhn c. Kch thc v gi thnh ca

mt nt n cng c xem xt n trong mt s ng dng. V mt kch thc, n phi

nh nm trn ngun pin cn v mt gi thnh, n ph thuc trc tip vo cht lng cm

bin ca nt. Thng thng, chnh xc ca kt qu c th nhn c t cc nt n. S

lng, gi thnh v chnh xc ca cc nt n c lin quan n nhau khi so snh mt h

thng c nhiu nt cm bin vi mt mng tp trung. Nt t tin s cho chnh xc cao

hn. S dng nhiu cm bin n gin v gn vi hin tng cn nghin cu s to ra mt

kin trc h thng va n gin, va s dng nng lng c hiu qu so vi mng phn b.

Cch hiu su hn mng cm bin khng dy l hin thc ho n.

1.2 Mng cm bin khng dy v ng dng

c trng v cu hnh mng cm bin

Mt nt trong mng WSN thng thng bao gm 2 phn: phn cm bin (sensor) hoc

iu khin v phn giao tip v tuyn (RF transceiver). Do s lng nt trong WSN l ln v

khng cn cc hot ng bo tr, nn yu cu thng thng i vi mt nt mng l gi thnh

thp (10 - 50 usd) v kch thc nh gn (din tch b mt vi n vi chc cm2).

Do gii hn v ngun nng lng cung cp (pin...), gi thnh v yu cu hot ng

trong mt thi gian di, nn vn tiu th nng lng l tiu ch thit k quan trng nht

trong mng cm bin:

- Lp vt l (physical layer) (s c trnh by trong chng 4) tng i n gin,

gn nh do rng buc v kch thc v kh nng tnh ton ca nt. K thut iu ch tn hiu

s nh QPSK, FSK ci thin hiu sut b khuch i cng sut. Cc k thut m ha sa

sai phc tp nh Turbo Codes khng c s dng, k thut tri ph c s dng ci

thin SNR thit b thu v gim tc ng ca fading ca knh truyn...

- Lp MAC (s c trnh by trong chng 5): k thut a truy cp TDMA hoc

CSMA-CA hiu chnh vi mc ch gim nng lng tiu th.

WSN thng c trin khai trn mt phm vi rng, s lng nt mng ln v c

phn b mt cch tng i ngu nhin, cc nt mng c th di chuyn lm thay i s

mng... do vy WSN i hi mt s mng (topology) linh ng (ad-hoc, mesh, star ...) v

cc nt mng c kh nng t iu chnh, t cu hnh (auto-reconfigurable).

Trong mt s WSN thng dng (gim st, cm bin, mi trng ...) a ch ID cc nt

chnh l v tr a l v gii thut nh tuyn da vo v tr a l ny gi l giao thc nh

tuyn a l (GRT - Geography RouTing protocol). i vi mng c s lng nt ln, s

mng khng n nh ... GRT gip n gin ha gii thut tm ng, gim d liu bng nh

tuyn (routing table) lu tr ti cc nt. GRT ph hp vi cc WSN c nh, tuy nhin i vi

20

cc nt di ng (a ch ID node thay i) giao thc nh tuyn tr nn phc tp v khng n

nh.

- Phn nhm: phn chia mng din rng (hng trm, hng ngn nt) thnh cc nhm

n nh cu hnh mng, n gin ha gii thut nh tuyn, gim xung t (collission) khi truy

cp vo knh truyn nn gim c nng lng tiu th , n gin ha vic qun l mng v

cp pht a ch cho tng nt mng (theo nhm).

Do gii hn kh nng tnh ton ca tng nt mng cng nh tit kim nng lng,

WSN thng s dng cc phng php tnh ton v x l tn hiu phi tp trung (gim ti cho

nt gn ht nng lng) hoc gi d liu cn tnh ton cho cc trm gc (c kh nng x l

tn hiu mnh v t rng buc v tiu th nng lng).

Khi cm bin khng dy tr thnh thng phm quen thuc trn th trng th vic la

chn gia cc loi cm bin v kiu mng mi v c lm au u cc chuyn gia v lm cho

h phi xem xt li nhng chin lc xy dng kin trc mng m trc y tng b gt

sang mt bn. Sau y, chng ta cng tm hiu v 3 kiu mng c bn s dng cho cm bin

l kiu mng im - im (point to point), im - a im v mng a im a im.

Cu trc mng im im

L kiu kt ni n gin nht, hai nt truyn thng qua hai anten thu pht cng sut cao

hng trc tip vi nhau. Trn l thuyt, kiu mng ny l an ton nht v ch c 1 im trong

mng c kh nng xy ra s c, l im mng ch hay cn gi l host. nng cao kh

nng ca h thng mng ch cn b sung thm 1 host d phng. Tuy nhin, vic ni dy 2

host li l vn ng bn. Mt s cu trc mng ny h tr tn hiu iu bin tn cho dy

dn truyn ti tn hiu ca nhiu cm bin trn cc knh FM ring bit. Mt s chun (nh

HART bus) h tr ng truyn tn hiu s song cng cho nhng ng truyn tn hiu tng

t sn c trong mt s nh my cng ngh c. Kiu kin trc nh vy xa nha danh gii

khc bit gia cu trc mng im - im v cu trc mng a im.

Nhng kiu mng khng dy u tin s dng tn hiu tn s radio (RF - Radio

Frequency) n gin cho cu trc mng im - im. Cu trc mng ny s dng modem RF

2 u mng. Mt ci t ti u pht lm nhim v chuyn tn hiu RS-232 thnh tn hiu

radio v ci cn li t ti u thu lm nhim v chuyn tn hiu v trng thi vn d ca n.

Fluke (Everett, Washington) pht trin mt loi vn k s c th nhn tn hiu in p v

truyn i qua mt knh tn s radio chuyn bit. Tuy nhin, cch ny b nghi ng v tin

cy v thit b ny c thit k cho nhng tn hiu FM m ha n gin. Cn trong mi

trng nh my, cc yu t gy nhiu c th lm gim ng k cht lng ca tn hiu, do vy

mng tr nn khng ng tin cy, tr khi n c chm sc rt chu o.

Kiu mng LAN khng dy cng c s dng trong cu trc mng ny nhng n ch t ra

hp vi mi trng vn phng hn l nh my. Nhng nh thit k s dng h thng thu thp

d liu t xa kt hp vi cu trc mng ny bng cch dng b gom d liu v y d liu

ny ti b truyn tn hiu radio truyn ti host, ti y, tn hiu s c a tr v hnh hi

ban u vn c ca n.

21

Hnh 1.1 Mng im im

im a im (Point-to-Multipoints)

Kt ni c chia s gia nt ti ln (Nt kt ni ti mng Internet thng qua ng

truyn hu tuyn cung cp kt ni Internet cho ton mng) dng anten a hng vi cc

nt ti xung (Nt kt ni ti mng v c kh nng phc v c kt ni hu tuyn v v tuyn

cho mng) hoc nt lp (Nt kt ni vo mng v khng dng phc v cc client ch ng

vai tr l nt trung gian lp tn hiu) vi anten thu cng sut cao. Cu hnh mng ny d trin

khai hn cu hnh im im v khi thm mt thu bao mi ch cn lp t thm thit b ti

khu vc thu bao ch khng phi lp ti nt ti ln. Tuy vy, cc trm thu phi nm trong

phm vi ph sng v c ng nhn thng vi trm pht sng gc. Cc vt cn nh cy ci,

nh ca, i ni, ... s gp phn lm cu hnh mng li im a im hot ng khng

hiu qu.

Hnh 1.2 Mng im a im

a im a im (Multipoints to Multipoints)

Mi nt c vai tr khng ch l im truy nhp cho cc trm m cn lm nhim v

chuyn tip d liu.

Cu hnh ny c tin cy mng cao nht do cc nt c s lin thng vi nhau, mt nt

22

ch cn c kt ni vi mt nt bt k m khng cn phi c kt ni trc tip vi nt ti ln

nh trong cu hnh im a im, l c th kt ni vi ton mng. Tuy nhin, i li giao

thc tm ng ca mng s c phc tp cao hn.

Hnh 1.3 Mng a im a im

Yu cu ca mng cm bin khng dy l cng ngh ca n phi thun tin vi cc ng

dng hin c v tht s mang li hiu qu. Ngoi s cn thit l phi xy dng mt mng gi

r, n gin trong lp trnh v mng, cc nt cm bin c tui th di, thnh phn bt buc v

ch yu pht trin cc ng dng trn thc t l kh nng cm nhn v thc hin ca cc

cm bin trong mng. i vi nhiu tham s vt l, cng ngh cm bin thch hp tn ti

c th c tch hp trong mt nt ca WSN. Cc tham s l nhit , m, nh sng

hng ngoi v nh sng nhn thy (k c nh sng pht ra t camera), m thanh, rung ng (v

d nh pht hin ri lon a chn), p sut, cc cm bin ho hc Thm ch n c th cm

nhn c cc i tng phc tp hn nh chi trong vn tr c th c cm gic.

Cc c cu chp hnh khng th c iu khin mt cch trn vn bng mt nt ca

mng cm bin khng dy. Thng thng, cc c cu chp hnh kim sot mt thit b c kh

nh mt a servo, hoc c th bt/tt mt s thit b in bng rle in nh bng n,

micro hoc thit b tng t. Trn c s cc nt c cm bin v /hoc c cu chp hnh s

kt hp vi kh nng tnh ton v giao tip to ra nhiu ng dng khc nhau vi nhiu kiu

nt khc.

Cc ng dng cu tr thin tai: y l mt trong nhng ng dng c ch nht

ca WSN. Hin tng thng gp nht l pht hin chy rng: cc nt cm bin c trang b

nhit k v c th xc nh v tr ca n (theo h to tuyt i hoc tng i, tc v tr ca

n so vi cc nt khc). Cc cm bin ny c th vo mt m chy, v d nh mt khu

rng v t mt chic my bay. Chng to ra mt bn nhit chung ca khu vc hoc

xc nh chu vi ca khu vc c nhit cao c th tip cn t bn ngoi. V d tng t l

kim sot tai nn ti nh my ha cht.

23

Mt s cc ng dng cu tr thin tai c im chung vi cc ng dng qun s, khi cc

cm bin c dng pht hin, v d, qun ch ch khng phi l chy rng. Trong ng

dng nh vy, cm bin nn c gi thnh r c th dng mt ln v cn phi dng vi s

lng rt ln v yu cu thi gian tn ti khng qu cao.

Gim st mi trng v lp bn a dng sinh hc: Cc WSN c th c dng

gim st mi trng, v d nh cc cht nhim ha hc ti v tr rc. Lin quan mt thit

vi vic gim st mi trng l s dng cc WSN bit s lng cc loi ng thc vt

sng trong mt mi trng.

u im chnh ca cc WSN y l cc cm bin khng phi gim st, hot ng

trong thi gian di, giao tip v tuyn c c th t gn i tng c quan st. Do cc cm

bin c th c cu to nh khng b l nn n ch hi lm phin cc ng thc vt

c quan st m thi. Thng thng, yu cu v s lng cm bin cao hn yu cu v thi

gian hot ng ca n.

Cc ta nh thng minh: S lng ph nng lng ca cc to nh gm mt lng ln

nng lng do s dng m, thng gi, iu ha nhit (HVAC) khng hiu qu. S tt

hn nu gim st theo thi gian thc, c phn gii cao nhit , lung khng kh, m v

cc thng s vt l khc trong to nh bng WSN. iu ny c th lm tng mt cch ng k

mc thoi mi ca ngi dn v gim lng tiu th nng lng. Ci thin hiu sut nng

lng v tng mc thun tin l nhng mc ch ca "ta nh thng minh" hng ti. Do

, cc h thng hu tuyn hin nay nh BACnet, LonWorks, hoc KNX hoc ang c

trin khai. Cc tiu chun ny cng bao gm vic pht trin thnh phn khng dy hoc kt

hp chng trong tiu chun.

Ngoi ra, cc nt cm bin nh vy c th c s dng theo di mc chu ng c

hc ca cc ta nh trong khu hot ng a chn mnh. Bng cch o cc thng s c hc

nh ti un ca dm c th nhanh chng xc nh thng qua WSN l liu to nh c an

ton vo sau trn ng t mc d n sp sp? y l mt li th ng k cho nhn vin

cu h. Cc h thng tng t cng c th c p dng cho cc cy cu. Loi cm bin khc

c dng tm ngi trong mt ta nh b sp v chuyn thng tin cho mt i cu h.

u im chnh y l lp bn cng tc ca cc thng s vt l. Ty thuc vo ng

dng c bit, cm bin c th c trang b thm vo cc ta nh hin c (cho cc ng dng

loi HVAC) hoc phi c a vo ta nh sp xy dng.

Qun l thit b: qun l c nhiu hn cc thit b trong mt ta nh, cc WSN

cng c mt lot cc ng dng c th. Mt v d n gin l vo khng cn cha kho

nhng ni mi ngi eo ph hiu, n cho php WSN kim tra nhng ngi c php vo

cc khu vc . V d ny c th c m rng pht hin k xm nhp, v d nh khi

phng tin ca h ra khi c quan trong gi lm vic. Mt WSN din rng c th theo di v

tr ca mt phng tin no v bo cho nhn vin an ninh. ng dng ny c nhiu im

chung vi cc ng dng trong qun s. Theo cch khc, mt WSN c th c s dng trong

mt nh my ha cht kim tra r r ha cht. i km cc ng dng ny l cc yu cu y

thch thc nh s lng cm bin c th ln, phi c tnh cng tc (nh trong v d theo di)

v c th hot ng bng pin trong mt thi gian di.

24

Bo dng v gim st my: Mt tng l c nh cc nt cm bin nhng ni t

my mc nhng kh tip cn, ni n c th pht hin cc chn ng v n cho thy s cn

thit phi bo tr. Trng hp ny c th l cc robot hoc cc trc xe ca on tu. Cc ng

dng khc trong sn xut nh my t nhng ni c phng x, cha nhiu cht c hi,

hoc nm su di lng t... u im chnh ca cc WSN y l hot ng khng cn dy

ni nn khng cn phi bo dng, cc cm bin c gi thnh thp v c th thng xuyn

c ci t li. Ngun cp bng dy dn th lc c, lc khng ph thuc vo tng ng dng.

Nu khng c ngun nui th vic cm bin phi hot ng trong mt tri gian di bng

ngun pin c nng lng hn ch l khng thc t v tn km. Th nhng kch thc v gi

thnh ca cc nt thng khng phi l vn qu quan trng.

Trong nng nghip: p dng WSN vo nng nghip lm cho vic th phn v ti

tiu c chnh xc bng cch t cc cm bin o m/ thnh phn t vo mi trng.

Ch cn mt s lng tng i cm bin nh l , khong mt cm bin cho mi vng c

din tch 100 m 100 m. Tng t, gim st su b c th c thc hin bng mt b theo

di c phn gii cao. Ngoi ra, chn nui c th tng li nhun t vic gn cm bin cho

mi con ln hoc b kim sot tnh trng sc kho ca ng vt (bng cch kim tra nhit

c th, m bc) v bo ng nu vt qu ngng cho php.

Chm sc sc khe v y t: Cng cch lm tng t, s dng WSN trong cc ng

dng chm sc sc khe em li rt nhiu li nhun nhng cng gy tranh ci v mt o

c. Phm vi p dng l t chm sc sau phu thut v chuyn su, ni m cm bin trc tip

gn vo vi bnh nhn th hin li th so vi hu tuyn - gim st bnh nhn trong thi

gian di (thng l ngi cao tui) v qun l thuc t ng (cm bin nhng vo bao b

ca thuc, bt bo ng khi s dng sai cho bnh nhn). Do , cc h thng theo di bnh

nhn v bc s trong bnh vin gip tit kim thi gian.

Thng tin: Cc cm bin nhng vo trong cc ng ph hay l ng c th thu

thp thng tin v iu kin giao thng t a ra nhng gii php tt hn. Cc cm bin

ny c th tng tc vi xe i trn ng cnh bo nguy him v cc iu kin ng hay

ch tc giao thng pha trc.

Bn cnh , cc ng dng khc ca WSN h tr ct cnh cho my bay, trong cc nh

my x l nc thi, thit b o c ca phng x l cht bn dn v cc ng hm gi,

trong "nh tr thng minh" (ni c s tng tc gia chi v tr em), pht hin ca l lt,

gim st mi trng sng ca chim trn mt hn o, v cm bin cy vo c th ngi (

theo di lng ng hoc vng mc gi).

Hu ht cc ng dng ny u c th c thc hin theo mt cch no bng cng

ngh hin nay m khng cn cc mng cm bin khng dy. Nhng, cc ng dng s lm vic

tt hn khi c nhiu thng tin hn v gii php khng gian v thi gian ca i tng cn

quan tm so vi nhng g m cng ngh cm bin truyn thng c th c c. Cc mng

cm bin khng dy c phm vi cung cp thng tin ln vi chnh xc yu cu ti cng thi

im v c lng tiu th nng lng l t nht c th.

Mng cm bin c th s dng trong rt nhiu lnh vc. Nu phn loi da vo chc

nng ca mng th c th hnh dung ng dng ca cc mng cm bin nh sau:

25

- Cm bin mi trng (qun s: pht hin mn, cht c, dch chuyn qun ch...;

cng nghip: h thng chiu sng, m, phnh chy, chng r r...; dn dng: h thng iu

ha nhit , chiu sng...).

- iu khin (qun s: kch hot thit b, v kh qun s ...; cng nghip: iu khin t

ng cc thit b, robot ...).

- Theo di, gim st, nh v (qun s: nh v, theo di s dch chuyn thit b, qun

i...).

- Mi trng (gim st l lt, bo, gi, ma ... pht hin nhim, cht thi...).

- Y t (nh v, theo di bnh nhn, h thng bo ng khn cp...).

- H thng giao thng thng minh: giao tip gia bin bo v phng tin giao thng,

h thng iu tit lu thng cng cng, h thng bo hiu tai nn, kt xe ... h thng nh v

phng, tr gip iu khin t ng phng tin tin giao thng...

- Gia nh (nh thng minh: h thng cm bin, giao tip v iu khin cc thit b

thng minh ...)

Hu ht cc ng dng ny c c tnh c bn ging nhau. Khc bit r rng gia cc

ngun d liu (nt cm bin) l mi lin h gia d liu o c b cha - v cc nt (ni

d liu c gi i). B cha c khi l mt phn ca chnh mng cm bin, nhng c khi n

l cc h thng ngoi mng. Do , s ngun thng nhiu hn b cha (nhng khng phi

lc no cng vy) v b cha khng bit hoc khng ch n vic nhn dng ngun. y

d liu c vai tr quan trng hn nhiu.

M hnh tng tc gia ngun v b cha c th hin theo mt s cch sau:

Pht hin s kin: Cc nt cm bin phi bo co vi b cha khi n pht hin s xut

hin ca s kin. Nhng s kin n gin nht c th c pht hin bi mt nt cm bin

n (v d nh vt qu ngng nhit ; loi s kin phc tp hn yu cu phi c s cng

tc ca cc b cm bin ln cn hoc thm ch l cc cm bin xa quyt nh xem liu s

kin xy ra cha (v d nh ng bin thin nhit tr nn qu dc). Nu nhiu s kin

khc nhau xy ra th phi thc hin phn loi s kin.

Cc php o nh k: Cc cm bin c th c giao nhim v thu thp cc s liu o

c tnh nh k. Thng thng, d liu c c khi mt s kin pht hin c kch hot; chu

k ca d liu ph thuc vo ng dng.

Chc nng xp x v pht hin bin: Cch gi tr vt l (v d nh nhit ) thay i

t ni ny sang ni khc c th c coi l chc nng ca a im. WSN c th c s

dng xp x chc nng cha bit ny (ch xt cc c tnh khng gian ca n), bng cch

s dng mt s gii hn cc mu ly ti mi nt cm bin ring bit. Bn xp x ny phi

c thc hin b cha. Lm th no v khi no cp nht bn ny, chnh xc ca chc

nng xp x v mc tiu th nng lng ph thuc vo nhu cu ca cc ng dng.

Tng t nh vy, vn lin quan l c th c tm thy cc khu vc hoc cc im

c cng gi tr thu c. V d, tm nhng im thuc ng ng nhit khi chy rng

26

pht hin bin gii ca m chy thc t. iu ny c th c tng qut tm ra "bin "

trong cc chc nng nh vy hoc gi tin nhn dc theo ranh gii ca cc mu trong c

khng gian v /hoc thi gian.

Theo di: Ngun ca mt s kin c th di chuyn (v d khi theo di trm t nhp).

WSN c th c s dng cp nht v tr, nh gi tc v hng ca ngun s kin n

b cha. lm nh vy, thng thng cc nt cm bin phi hp tc vi nhau trc khi cp

nht d liu cho b cha.

Cc nt cm bin tng tc vi nhau c v thi gian v khng gian (bo co s kin ch

thc hin trong mt khong thi gian nht nh v ch t cc khu vc nht nh). Nhng yu

cu ny cng c th thay i mt cch linh hot theo thi gian; b cha phi thng bo cho

cc b cm ng yu cu ca chng trong qu trnh hot ng. Tng tc c th din ra ch

nhm phc v mt yu cu c th ca b cha, hoc phc v cho mi quan h lu di gia cc

b cm bin v b cha.

Cc v d cho thy s a dng trong cc la chn ng dng. C th c nh v tr

t cc nt cm bin (nh trong cc ng dng bo tr my mc thit b) hoc c th t cc

nt cm bin mt cch ngu nhin bng cch th mt s lng ln cc nt t my bay vo

mt m chy rng. Ngoi ra, cc nt cm bin c th t di chuyn b p thiu st trong

qu trnh trin khai v n v tr mi m ti , nhim v cm bin ca n thc hin c tt

hn. N c th di chuyn gim st thm cc i tng khc (trong cc ng dng hu cn)

v mng thch ng vi n.

Cc ng dng cng nh hng n vic la chn bo dng: C nht thit phi bo

dng cc cm bin v cc my mc thit b c lin quan? Bo dng l khng ph hp v

cc mng ny ch c trin khai trong mng ad hoc, theo cch thc ngn hn, b gii hn bi

thi gian thc hin ti a (nh trong cc hot ng khc phc thm ha)? Cc cm bin ny

c chc nng khng gim st trong mt thi gian di nn khng c kh nng bo tr?

Trong mt s ng dng, ngun cp hu tuyn c th thc hin c v y khng c

vn g v cung cp nng lng. i vi cc nt cm bin t hot ng, ty thuc vo yu

cu v thi gian thc hin m nng lng cung cp c th khng ng k (vi nhng ng

dng yu cu thi gian thc hin l mt vi ngy) hoc s l vn i vi cc ng dng

khng th bo dng m yu cu thi gian thc hin l vi nm. R rng l gi c v kch

thc mi nt ng mt vai tr quan trng trong vic thit k cung cp nng lng.

1.3 Nhng kh khn ca mng cm bin khng dy

X l mt lot cc loi ng dng nh trn s gy kh khn cho mng cm bin. Tuy

nhin, vn c c im chung cho cc ng dng nh vy, c bit l trn kha cnh c tnh

v cc k thut yu cu. Hin thc ho cc c tnh ny bng k thut mi l kh khn chnh

i vi mng cm bin khng dy.

1.3.1 Cc yu cu k thut

Cc c tnh sau c yu cu trong hu ht cc ng dng ca mng cm bin khng

dy:

27

Loi hnh dch v: Chc nng ca mng thng tin thng thng hin nhin l di

chuyn cc bit t ni ny n ni khc. i vi mt WSN, di chuyn cc bit ch l bc kt

thc, nhng khng phi l mc ch thc t. Hn th na, mt WSN c k vng l cung

cp thng tin c ngha v/ hoc hnh ng theo nhim v cho. Ngoi ra, cc khi nim

phm vi tng tc, khu vc a l c trng hay khong thi gian s tr nn quan trng. Do

yu cu phi c mt m hnh mng mi vi cc giao din mi v cch ngh mi v dch v

mng.

Cht lng dch v: Lin quan cht ch n cc loi hnh dch v mng l cht lng

dch v. Thng thng, cht lng ca dch v th hin trong cc ng dng thuc loi hnh a

phng tin. Tr b chn hoc bng thng ti thiu khng thch hp cho cc ng dng c tr

hoc khi bng thng ca d liu truyn i rt nh. Trong mt s t trng hp, vic cung cp

cc gi d liu c th tha, trong nhng trng hp khc, yu cu tin cy rt cao. Nhng

trng hp nh vy s lm tng vai tr ca tr khi cc c cu chp hnh c iu khin theo

thi gian thc bi mng cm bin. Cht lng dch v ch cn c vo h s cung cp gi tin l

cha y v n cn lin quan n s lng v cht lng thng tin v i tng hoc khu

vc c quan st.

Mc chu li: Do cc nt c th ht nng lng hoc b hng, hoc thng tin v tuyn

gia hai nt b gin on nn WSN c th c li. Trong nhng trng hp nh vy, hn

ch li th WSN nn c s nt nhiu hn mc cn thit.

Thi gian s dng: Trong nhiu trng hp, cc nt phi da vo ngun nng lng

hn ch (s dng pin). Vic thay th ngun pin ny l khng thc t v khng th thc hin

tc thi. WSN phi s dng c t nht l trong thi gian thc hin nhim v c giao. Do

, tui th ca WSN rt quan trng v hin nhin, cch thc WSN s dng nng lng

mt cch c hiu qu thc s cn thit.

thay i hoc b sung thm nng lng cho WSN, ngun c cng sut hn ch (v

d nh pin mt tri) cng c th c s dng cho cc nt cm bin. Thng thng, cc

ngun ny khng mnh m bo cho hot ng c din ra lin tc nhng n c th

dng xc pin. Vi cch lm nh vy th tui th ca WSN, theo l thuyt, s l v hn.

Tui th ca WSN t l nghch vi cht lng dch v: s dng nhiu nng lng s lm

tng cht lng dch v nhng nh vy s lm gim tui th ca mng. Chnh v vy, khi thit

k mt WSN phi cn bng hai yu t ny.

nh ngha chnh xc tui th ph thuc vo ng dng c th ca mng. l khong

thi gian t khi mng bt u s dng cho n khi nt u tin b hng (hoc ht nng lng);

hoc n bao gm khong thi gian t khi mng bt u s dng cho n khi mt kt ni gia

hai hoc nhiu nt v khong thi gian cho n khi 50% nt b hng; hoc l khong thi

gian khi ln u tin mt im nm trong vng quan st khng cn chu s gim st ca bt

k nt cm bin no (trong nhiu trng hp, WSN s dng s nt cm bin nhiu hn yu

cu nn mt im c th chu s gim st ca nhiu nt).

Kh nng m rng: T mt WSN gm mt s lng ln cc nt, kin trc v giao

thc ca mng lm vic c kh nng m rng.

28

Di rng ca mt : Trong mt WSN, s lng nt trn mi n v din tch - mt

ca mng - c th khc nhau ng k. Cc ng dng khc nhau s c mt nt rt khc

nhau. Ngay c trong mt ng dng nht nh, mt c th khc nhau theo thi gian v

khng gian do cc nt di chuyn hoc b hng; mt cng khng phi ng nht trong ton

b mng (do v tr t nt khng hon ho) v mng nn thch ng vi cc bin i .

Kh trnh: khng ch cn cho cc nt x l thng tin m cn n cn dng cc

nt phn ng linh hot hn khi thay i nhim v. Cc nt cn c lp trnh, v chng trnh

phi c thay i trong qu trnh hot ng, khi nhim v mi tr nn quan trng. X l

l thng tin theo mt cch nh sn khng th p ng c yu cu.

C kh nng bo dng: Khi c mi trng ca WSN v chnh bn thn WSN thay

i (ht pin, nt b hng, khi c nhim v mi) th h thng phi thch nghi vi iu . N c

th theo di trng thi ca chnh mnh thay i cc thng s hoc la chn tiu ch hot

ng (v d nh cht lng dch v s b gim st khi ngun nng lng b yu i). Trong

trng hp ny, mng phi t bo dng, n cng c th tng tc vi cc c ch bo dng

bn ngoi qu trnh hot ng m bo cht lng t ra.

1.3.2 Cc k thut yu cu

thc hin cc yu cu ny, k thut i mi mng thng tin, kin trc v cc khi

nim giao thc mi c thc hin. Thch thc y l cn phi tm cng ngh p ng

c cc yu cu v cht lng dch v, tui th v cc yu cu v kh nng bo dng. Mt

khc, cng ngh ny phi s dng c trong nhiu ng dng c th v phi cho thy c

tnh cn thit ca WSN trong cc ng dng ny. Sau y l mt s cng ngh thng c

dng trong cc WSN:

Giao tip v tuyn a bc nhy: Khi giao tip v tuyn l k thut ct li, thng tin

trc tip gia ngi gi v ngi nhn s phi i mt vi mt s hn ch. c bit, giao tip

ng di ch thc hin c khi s dng cng sut pht rt cao. Vic s dng cc nt trung

gian nh cc tr c th lm gim tng nng lng yu cu. Do , vi nhiu loi WSN, ci

gi l giao tip a bc nhy l mt thnh phn cn thit.

S dng nng lng c hiu qu: ko di tui th th vic s dng nng lng mt

cch c hiu qu l k thut trng im. iu ny c th c c bng cch s dng hiu qu

nng lng truyn d liu gia hai nt (o bng bit /J) hoc quan trng hn l xc nh hiu

qu nng lng ca thng tin yu cu. Ngoi ra, tiu th nng lng khng ng u to

nn cc "im nng - hotspot" cng l mt vn .

T cu hnh: WSN s phi t cu hnh cc thng s hot ng ca n, vic ny c lp

vi cu hnh bn ngoi S nt cng t cng tt v b tr n gin l yu cu trong hu ht

cc ng dng. V d, cc nt c th xc nh v tr a l ca n ch bng cch s dng cc nt

khc trong mng. N cn c gi l "t nh v - self-location". Ngoi ra, mng c th c

cc nt hng (v d nh do ht pin) hoc tch hp cc nt mi (v d nh b sung thm nt

khi mng cha p ng c yu cu t ra).

S cng tc v x l trong mng: Trong mt s trng hp, mt cm bin khng th

quyt nh c vic liu s kin c xy ra hay khng nhng nhiu cm bin cng tc vi

29

nhau s cung cp thng tin lm iu . Thng tin c x l trong mng theo cc cch

thc khc nhau c c s cng tc ny. iu ny ngc vi vic mi nt truyn d liu

n mt mng bn ngoi x l.

V d, xc nh nhit cao nht v nhit trung bnh trong mt khu vc v a

gi tr n b cha. gii quyt bi ton ny mt cch c hiu qu, cc kt qu c t cc

cm bin ring l c tp hp li v truyn qua mng. Vic ny s lm gim s d liu

truyn trn mng v do , vic s dng nng lng s hiu qu hn.

Trung tm d liu: Mng thng tin truyn thng thng tp trung vo vic chuyn

giao d liu gia hai thit b c th, mi thit b yu cu c t nht mt a ch mng. Mng c

kin trc nh vy hot ng theo trung tm a ch. Trong WSN, ni m cc nt thng c

b tr d d phng cho vic nt b hng hoc tng cht lng ca thit b ch c mt nt

cm bin. Vic cung cp d liu ging nhau cho cng mt nt mng l khng cn thit. Vn

quan trng y l bn thn d liu nhn c ch khng phi l nt cung cp d liu

. Do , xu hng hin nay l chuyn t m hnh trung tm a ch sang m hnh trung tm

d liu trong vic thit k kin trc v giao thc truyn thng.

V d, m hnh tng tc ca trung tm d liu nh vy s c s dng khi cn c

nhit trung bnh trong mt khu vc cho, n ngc vi yu cu nhit c t cc nt

ring l. M hnh trung tm d liu nh vy cng c th c dng t iu kin cho cc

cnh bo hoc cc s kin ("bt bo ng nu nhit vt qu ngng").

1.4 Ti sao mng cm bin li khc vi cc mng khc?

Trn c s ca mt s ng dng v nhng thch thc chnh, mng cm bin khng dy

c th tr thnh mng Ad hoc di ng (MANET Mobile Ad hoc Network) v fieldbus.

1..4.1 Mng Ad hc di ng v WSN

Mng Ad hoc l mt mng ci t, theo ngha en, cho mt mc ch c th, p ng

nhu cu thng tin xut hin tc thi. V d n gin ca mt mng Ad hoc l mt tp hp cc

my tnh kt ni vi nhau qua cp to thnh mt mng nh, nh mt s my tnh xch tay

trong mt phng hp. Trong v d ny, kha cnh t cu hnh ng vai tr quan trng - mng

d kin lm vic m khng cn qun l hoc cu hnh bng tay.

Mng ad hoc

Ad hoc networks l im bin cui cng ca thng tin khng dy (thng tin v tuyn).

Cng ngh ny cho php cc nt (im ni) mng truyn trc tip vi nhau s dng b thu

pht khng dy (wireless transceiver) m khng cn bt c mt c s h tng c nh no.

y l mt c tnh ring bit ca mng ad hoc so vi cc mng khng dy truyn thng nh

cc mng chia (cellular networks) v mng WLAN, trong cc nt (v d nh cc thu

bao in thoi di ng) giao tip vi nhau thng qua cc trm v tuyn c s (wired radio

antenna).

Ad hoc networks c mong i s lm cch mng ha thng tin khng dy trong mt

vi nm ti bng vic b sung thm vo cc m hnh mng truyn thng (nh Internet,

cellular networks, truyn thng v tinh). Mng Ad hoc cng c th c xem nh nhng bn

30

sao cng ngh ca nhng khi nim my tnh thng gp. Bng vic khm ph cng ngh

mng khng dy Ad hoc, nhng thit b cm tay chng loi (nh in thoi di ng, PDAs,

my tnh xch tay, my nhn tin pager..) v cc thit b c nh (nh cc trm v tuyn

c s, cc im truy cp Internet khng dy, ) c th c kt ni vi nhau, to thnh mng

ton cu, khp mi ni.

Trong tng lai, cng ngh mng Ad hoc c th s l la chn rt hu ch. V d, hy

xem tnh hung sau. Mt cn ng t khng khip tn ph thnh ph ca chng ta, trong

c hu ht cc c s h tng vin thng (nh cc ng in thoi, trm v tuyn c s).

Nhiu i cu h (nh lnh cu ha, cnh st, bc s, cc tnh nguyn vin ) ang n lc

cu mi ngi khi cn ng t v cha tr cho nhng ngi b thng. h tr tt hn

cho i cu h, cc hot ng cu h ca h phi c hp tc vi nhau. R rng l 1 hot

ng hp tc nh th ch t c thnh qu khi i cu h c th giao tip, thng tin vi

nhau, c vi ng nghip ca mnh (v d 1 cnh st vi 1 cnh st khc) v c vi thnh vin

ca i cu h khc (v d 1 lnh cu ha yu cu s tr gip t 1 bc s).

Hnh 1.4 S nguyn l mng chia s kt ni dng ad hoc

Vi nhng cng ngh hin c, nhng n lc ca i cu h s rt kh thnh cng khi

nhng c s h tng vin thng c nh b tn ph nng n. Thm ch nhng thnh vin ca

i cu h ny c trang b PDA hay cc thit b tng t khc trong trng hp khng th

truy cp c vi cc im c nh, ch nhng kt ni gia cc thnh vin ca i cu h

ng gn nhau mi thc hin c. V vy, mt trong nhng u tin trong vic qun l v

khng ch thm ha ngy nay l ci t li cc c s h tng vin thng nhanh nht c th,

bng cch sa cha cc thit b, kt cu h hng hay trin khai cc thit b vin thng tm

thi.

Kh khn ny c th c gii quyt ng k nu chng ta p dng nhng cng ngh

da vo mng Ad hoc: s dng cc giao tip khng dy phn tn gia nhiu im truy cp

khc nhau, thm ch cc i cu h cch xa nhau cng c th lin lc vi nhau hay lin lc

vi cc thnh vin i cu h khc khong gia nh hot ng ca mt trm chuyn tip.

31

V khu vc xy ra thm ha s tp trung nhiu i cu h, nn cc lin lc trong phm vi

thnh ph (hay thm ch l phm vi c nc) c th thc hin c, cho php cc n lc cu

h c hp tc thnh cng m khng cn thit lp li cc c s vin thng c nh.

Thng thng, khi nim v MANET lin quan n truyn thng v tuyn v c bit l

truyn thng a bc nhy v tuyn. S di chuyn ca cc nt l mt thnh phn ca mng.

Cc mng ny c s dng cho hot ng cu tr thin tai - nhn vin cu ha giao tip vi

nhau - hoc dng trong cc a im kh khn nh cng trnh xy dng ln, ni c th vic

trin khai c s h tng khng dy (v d nh im truy cp) trong khi thc hin hu tuyn

khng phi l mt la chn kh thi. Trong mng , cc nt ring l kt hp vi nhau to

thnh mt mng chuyn tip cc gi tin gia cc nt, do n m rng phm vi hot ng

ca mt nt n, m rng khu vc a l gia ngi gi v ngi nhn. Hai thch thc c

bn ca MANET l t chc li mng khi cc nt di chuyn v x l cc vn v hn ch ca

truyn thng v tuyn.

y l nhng tn ti chung ca c mng MANET v WSN. Tuy nhin vn tn ti mt

s khc bit c bn gia hai mng ny m bo s phn bit gia chng.

Thit b v cc ng dng: ng dng v thit b ca MANET khc WSN. Trong

MANET, u cui c th kh mnh (mt my tnh xch tay hoc mt PDA (Personal Digital

Assistant - Thit b h tr c nhn k thut s)) c ngun pin tng i ln. Cn c thit b

ny v trong cc ng dng MANET in hnh thng c s xut hin ca con ngi: MANET

c s dng cho truyn thng thoi gia hai ng nghip xa, hoc c s dng truy

cp vo mt c s h tng t xa, ging nh mt my ch Web. V vy, thit b phi c

mnh h tr cc ng dng ny.

Nh s dng mt lng ln cc nt cm bin, s dng cng ngh tnh ton v truyn

thng m WSN c th thc hin c rt nhiu ng dng khc nhau. iu khng c ngha

l ch s dng mt gii php m gii quyt c mi yu cu t ra. V d, WSN c th hiu

c rt nhiu mt mng khc nhau, t tha tht dy c, v vy m n s yu cu nhiu

giao thc khc nhau hoc t nht phi l cc giao thc ph hp. S a dng v mt khng

phi l iu ph bin trong cc MANET.

Tng tc vi mi trng: Do cc WSN phi c tng tc vi mi trng nn c

tnh lu lng ca n c th rt khc nhau. Thng thng, cc WSN c tc tc d liu rt

thp mt thi gian di nhng n li c lu lng rt cao khi c hin tng xy ra (v d, i

vi mt h thng thi gian thc l ma hoc bo). Trng thi ngh trong mt thi gian di c

th thay th bng trng thi hot ng rt cao ca mng trong mt thi gian ngn, nng cng

sut ca mng ln gii hn. Trong khi , MANET c s dng h tr nhiu ng dng

thng thng hn (Web, ging ni) vi cc c tnh lu lng khng c s thay i t

bin.

Quy m: Cc WSN thng dng gim st s lng thc th ln hn nhiu (hng

nghn, thm ch hng trm nghn) so vi mng ad hoc.

Nng lng: Trong c hai mng WSN v MANET, nng lng l vn c quan

tm. Cc WSN c yu cu cht ch hn v thi gian s dng, kh nng xc pin hoc thay th

ngun pin ca nt so vi MANET. Do , WSN quan tm nhiu n vic tiu th nng lng

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hn MANET.

T cu hnh: Tng t nh mng ad hoc, cc WSN yu cu t cu hnh thnh mng kt

ni, nhng s khc bit trong lu lng, s dng nng lng c th i hi gii php khc

nhau. Tuy nhin, v mt ny th MANET v WSN tng t nhau.

tin cy v cht lng dch v: Cc yu cu lin quan n tin cy v cht lng

dch v l kh khc nhau. Trong mt MANET, mi nt ring r u phi c tin cy kh

cao, cn trong mt WSN, mt nt ring r khng ng vai tr quan trng. Cht lng dch v

ca Manet c quyt nh bi cc ng dng truyn thng; i vi WSN, khi nim cht

lng dch v l yu cu hon ton mi, v ng nhin, mng s phi s dng nng lng

thc hin yu cu ny.

Trung tm d liu: Vic trin khai d phng cc nt s lm tng kch thc ca cc

giao thc trung tm d liu trong WSN. Cc giao thc trung tm d liu khng lin quan n

MANET.

Dch chuyn: Vn dch chuyn trong MANET bao gm s dch chuyn cc nt di

chuyn, thay i tuyn ng a bc nhy trong mng v iu ny phi c x l. Trong

mt WSN, vn ny cng c th tn ti nu cc nt cm bin di chuyn. Trong WSN, c hai

vn v dch chuyn cn c quan tm.

Th nht, mng cm bin c th c dng pht hin v quan st mt hin tng vt

l (v d nh trong cc chng trnh pht hin xm nhp). Hin tng ny l nguyn nhn ca

s kin xy ra trong mng (bt bo ng) v cng c th to ra mt s x l cc b (v d, xc

nh xem c thc s c phi l mt k xm nhp?). iu g xy ra nu i tng di

chuyn? V mt l tng, d liu ti mt a im c tp hp li v c th s dng cho a

im gn . Ngoi ra, trong cc ng dng theo di, y l nhim v ng nhin ca mng

m bo mt s hnh thc hot ng xy ra trong cc nt xung quanh hin tng quan st.

Th hai, cc b cha thng tin trong mng (cc nt m thng tin phi c gi n)

cng c th di chuyn. V nguyn tc, iu ny l khng khc vi vic di chuyn ca cc nt

trong MANET thng thng, nhng c th lm gim hiu qu hot ng ca cc giao thc so

vi trng thi tnh.

Hn na, trong MANET v WSN, tnh di ng c th tng quan vi nhau, tc l c

mt nhm cc nt cng di chuyn. V d nh trong MANET l mt nhm ngi i du lch

cng nhau. Trong WSN, s chuyn ng ca cc nt c th bo cun i.

Tm li, tuy c nhng im chung nhng trn thc t, WSN h tr cho cc ng dng rt

khc nhau, chng tng tc vi mi trng vt l v phi xem xt tht cn thn mc u tin

ca cc thng s. iu ny thc s lm nn s khc bit gia WSN v MANET.

1.4.2 Fieldbus and WSN

Fieldbus l mng c thit k c bit cho cc hot ng theo thi gian thc v thng

vi dung sai li nh sn. N c s dng ch yu trong cc ng dng iu khin c xem

nh l mt phn ca vng iu khin. V d nh Profibus v mng Token Bus IEEE 802.4

cho t ng ha nh my hoc bus CAN cho cc mng onboard trong xe hi Do cc yu

33

cu v thi gian thc rt nghim ngt nn cc mng ny thng l mng hu tuyn v ch c

cc lp mt (lp vt l), hai (lp lin kt), v by (lp ng dng) ca m hnh chun OSI

c s dng. Trnh giao tip qua nhiu bc v tr khi i qua cc nt trung gian. Mc d

vy, mt s nghin cu vn lit k fieldbus vo loi truyn thng v tuyn.

Do fieldbus cng quan tm n mi trng vt l m n thu thp d liu cm bin t

a ra cc quyt nh iu khin nn vi ngha ny, n rt ging vi cc WSN. Theo mt

cch hiu no th WSN c th c xem nh fieldbus v tuyn. Tuy nhin vn cn mt s

khc bit: WSN khng ch n vn thi gian thc m n tp trung nhiu hn vo cc

ng dng c th chu c tr. Ngoi ra, vic la chn cc c tnh mt cch ph hp l iu

m WSN mun thc hin (v d nh tnh chnh xc i vi hiu qu nng lng), v iu ny

li khng thng hin din trong fieldbus. Fieldbuses khng n lc bo tn nng lng, v

cc giao thc ca n khng c chun b lm iu .

1.5 Cc k thut cho WSN

Xy dng cc mng cm bin khng dy ch tr thnh hin thc vi mt s tin b c

bn trong cng ngh cho php. Trc ht, l cng ngh ti thiu ho phn cng. Kch

thc ca chip cng nh th mc tiu th in nng cng t, thm ch nm trong kh nng tnh

ton ca WSN. iu ny lin quan c bit n vi iu khin v chip b nh, nhng cc

modem v tuyn, chu trch nhim v phn giao tip v tuyn, s lm cho vic s dng nng

lng c hiu qu hn. Gim kch thc ca chip v hiu qu nng lng ci thin i km vi

chi ph gim, iu ny l cn thit thc hin trin khai d phng cc nt mt cch hp l.

Sau vic thu thp v x l thng tin th thit b cm nhn thc t l cng ngh quan

tm th ba. Rt kh bao qut vn ny v c rt nhiu loi cm bin khc nhau.

Chng 2 s trnh by chi tit hn vn ny.

Ba phn c bn ny ca nt cm bin phi i cng vi ngun cp. Cc yu cu ny ph

thuc vo ng dng, pin c dung lng cao th tui th di. Mt cch l tng, nt cm bin

cng c thit b tm nng lng, np pin bng nng lng ly t mi trng - cc t bo

nng lng mt tri l mt la chn.

Tng ng vi cc cng ngh phn cng c bn l phn mm. Cu hi u tin tr

li y l s phn chia nhim v v chc nng trong mt nt n - kin trc ca h iu

hnh hay mi trng hot ng. Mi trng ny phi h tr vic thc hin li nhim v n

gin, trao i thng tin lin lp v c module cho php thc hin cc bo dng n gin.

Kin trc phn mm trn nt n phi c m rng n kin trc ca mng, ni thc hin

vic phn chia nhim v gia cc nt.

34

CU HI N TP CHNG 1

1. Nu by c im c bn ca WSN

2. Cc yu cu k thut ca WSN

3. Cc k thut yu cu ca WSN

4. So snh mng Ad hoc v WSN

4. So snh Fieldbus v WSN

5. Nu mt s ng dng ca WSN trong cuc sng hng ngy

7. Nu c trng v cu hnh WSN

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CHNG 2. KIN TRC NT N

Mc ch ca chng

Chng ny gii thch phn t c bn ca WSN l nt, cc nhim v c bn ca n nh

tnh ton, lu tr, giao tip, cm nhn/vn hnh v cc b phn c yu cu thc hin cc

nhim v ny. Khi , tiu th nng lng ca cc b phn ny cng c cp n: nng

lng c th lu tr, thu thp t mi trng v lu gi n bng cch iu khin ch hot

ng ca cc b phn ca nt mt cch thng minh. Vic iu khin ny do mt h iu hnh

ging nh mi trng thc hin quyt nh.

Cui chng, bn c s c nhng hiu bit nht nh v kh nng v nhng hn ch

ca cc nt trong mng cm bin. N l nn tng ca cc chng sau, trong tp trung vo

cc nguyn tc la chn nt cm bin ring r c th kt ni thnh mt WSN.

xy dng mt WSN, yu cu u tin l cc nt hp thnh phi c trin khai v

c th s dng. Cc nt ny phi c cc yu cu t cc yu cu ca ng dng cho: nh, r

hoc hiu qu nng lng, c trang b cc cm bin tt, c kh nng tnh ton v ti nguyn

b nh cn thit, phi thch hp vi cc phng tin truyn thng. Cc b phn phn cng

ny v cu to ca chng trong nt chc nng c cp trong phn 2.1; cng sut tiu th

ca cc b phn ny v cc tho hip c ni n trong phn 2.2. Trong khi chng ny ch

tp trung v nt ring l th vic la chn k thut giao tip c bit cho kin trc ca mng

cm bin khng dy li c m t trong chng 3.

Ngoi phn cng ca cc nt cm bin, h iu hnh v m hnh lp trnh cng l cc

mi quan tm. Phn 2.3 m t nhim v ca h iu hnh, mt s v d v cc giao din lp

trnh ph hp.

2.1 Cc b phn phn cng

2.1.1 Tng quan phn cng ca nt cm bin

Khi chn cc b phn phn cng cho nt cm bin khng dy, r rng l cc yu cu

ca ng dng ng vai tr quyt nh vi mi quan tm ch yu v kch thc, gi thnh v

tiu th nng lng ca cc nt giao tip v cc phng tin tnh ton thng c quan

tm c cht lng chp nhn c, nhng tho hip gia cc c im v chi ph phi l

ct yu. Trong mt s trng hp c bit, ton b nt cm bin phi nh hn 1 cc, nh hn

100 g, r hn 1 USD v s dng t hn 100 W, thm ch c nhng trng hp kch thc thu

gn ch bng ht bi. Trong nhiu ng dng thc t, kch thc ca nt nh khng quan trng

m s thun tin, ngun cp n gin v chi ph ng vai tr quan trng h