Upload
fatada1478
View
74
Download
12
Embed Size (px)
DESCRIPTION
Mang Cam Bien Khong Day
Citation preview
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
2
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
3
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
4
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
5
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
6
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
7
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
8
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
9
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
10
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
11
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
32
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
35
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