Định Tuyến Trong Cảm Biến Không Dây

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Chng 4

nh tuyn trong cm bin khng dy

Hannes Frey, Stefan Ruhrup, v Ivan Stojmenovic

Mng cm bin khng dy tru tng c hnh thnh bi cc nt cm bin nh communicat-

ing qua cc kt ni khng dy m khng cn s dng mt c s h tng mng c nh. Cc nt cm bin

c mt phm vi truyn hn ch, ch bin v kh nng lu tr ca h nh

cng nh cc ngun nng lng ca h cng b hn ch. Giao thc nh tuyn cho cc cm bin khng dy

mng phi m bo tin cy truyn thng a-hop theo cc iu kin.

Chng ti m t nhng thch thc thit k cc giao thc nh tuyn trong mng cm bin v minh ho

c c cc k thut quan trng t c cc c tnh mong mun, chng hn nh hiu qu nng lng

v m bo giao hng. Chng ti cung cp cho mt cuc kho st ca nh nc-of-the-ngh thut k thut nh tuyn vi

tp trung vo cc tuyn a l, mt m hnh cho php mt thng ip hiu qu hot

nh tuyn m khng khm ph tuyn trc hoc kin thc v cu trc lin kt mng. Bit

ferent chin lc nh tuyn a l c m t cng nh beaconless tuyn

k thut. Chng ti cng cho thy cc tc ng vt l lp trn tuyn v phc tho thm

hng nghin cu.

4.1 Gii thiu

Mng cm bin khng dy c hnh thnh bi cc thit b nh giao tip qua dy

lin kt m khng cn s dng mt c s h tng mng c nh. Bi v ly hn ch

phm vi nhim v, giao tip gia hai thit b i hi cng tc

cc nt mng trung gian chuyn tip, tc l thit b hot ng nh b nh tuyn v h thng kt thc

cng mt lc. Giao tip gia bt k hai nt c th da trivially

n gin ch trn ngp ton b mng. Tuy nhin, cc thut ton nh tuyn phc tp hn

l rt cn thit cho cc ng dng ca mng khng dy nh vy, v nng lng

c bo tn trong cc thit b h tr thp v thng tin lin lc khng dy lun lun dn n

tng tiu th nng lng.

H. Frey ()

S Khoa hc my tnh, i hc Paderborn, Warburger Str. 100,

33.098 Paderborn, c

e-mail: [email protected]

S. Misra et al. (Eds.), Hng dn cm bin khng dy, my tnh Truyn thng

81

v Networks, DOI: 10,1007 / 978-1-84882-218-4 4,

c Springer-Verlag London Limited 2009

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H. Frey et al.

Cc thut ton nh tuyn u tin cho cc mng khng dy theo cn truyn thng

Cch tip ca cu trc lin kt da trn nh tuyn, tc l quyt nh chuyn tip da trn thng tin trong bo

s lin kt v hin sn gia cc nt mng [1-5]. ngh sm

c da trn chin lc nh tuyn ch ng duy tr thng tin nh tuyn v

con ng tt c c sn ngay c khi nhng con ng khng bao gi c s dng. nh tuyn Proactive lm

quy m khng tt trong vic thay i ng topo mng, do , phng php phn ng

duy tr cc ng bay m ch l hin ang s dng c nghin cu Hn th na

Ther trn.

Ngay c phng php nh tuyn phn ng vn c th to ra mt s lng ng k lu lng truy cp

khi topo mng thay i thng xuyn do di chuyn thit b hoc xen k en-

ergy bo tn chu k gic ng. Trong nhng nm gn y, nhn thc v v tr (v d nh cc nt bit

v tr a l ca h) c nghin cu nh l mt gii php tt cc inher-

nhng hn ch ca phng php ent topology-based. Mt s tiu thuyt a l (cn gi l

position-based) cc thut ton nh tuyn c xut, trong cho php cc router c

gn quc tch k t khi chuyn tip gi tin c thc hin bng cch s dng thng tin v

v tr ca cc nt ng c vin trong vng ln cn v v tr ca cc node ch

ch. Thng tin v v tr a l c th c xc nh bng phng tin ca mt tim ton cu

sitioning k thut nh GPS, hoc v tr tng i da trn c lng khong cch trn

mnh tn hiu n [6,7]. a l nh tuyn yu cu v tr thng tin trong bo

s v cc nt ch c c bit hay mua trc. Trong khng dy

mng cm bin, d liu thng c thu thp bi mt nt c ch nh, c gi l bn ra, v

v tr ca cc bn ra c th c m ha cng. Ni chung, tuy nhin, yu cu ca ch ca chng

v s c thc hin bng cch s dng dch v nh v thm [8] sn xut thm

ti mng, trong c c xem xt nu hiu sut ca phng php da trn v tr

c so snh vi nhng topology-based.

4.2 Bi cnh

nh tuyn trong mng cm bin khng dy khc vi nh tuyn thng thng trong mng li c nh

hot ng trong nhiu cch khc nhau: Khng c c s h tng, kt ni khng dy l khng ng tin cy,

cc nt cm bin c th tht bi, v cc giao thc nh tuyn phi p ng tit kim nng lng nghim ngt

yu cu. Nhiu thut ton nh tuyn c pht trin cho cc mng khng dy trong

ni chung. Cc thut ton nh tuyn m thc hin mt giao nhn end-to-end vi

da trn my ch a ch c th c phn loi nh topo da trn, nu cc im n l

c a ra bi mt ID, hoc nh v tr da trn, nu cc im n l mt v tr a l.

Sau ny cng c gi l thut ton nh tuyn a l. C hai topology-based v

cc thut ton nh tuyn a l l a ch trung tm, v bn cnh cc loi,

nh tuyn m hnh trung tm d liu tr nn ph bin trong cc khu vc ca mng cm bin.

Trung tm d liu nh tuyn da trn cc truy vn c ban hnh bi cc bn ra mt yu cu d liu.

Cc yu cu ny khng c cp n cc nt cm bin c th. Thay vo , cc nt cm bin

c th cung cp cc d liu yu cu s tr li cc truy vn. Tng quan v cc a d liu

cc thut ton nh tuyn trung tm c a ra trong [9].

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4 Routing trong cm bin khng dy

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Mt tiu ch phn loi na l vic s dng cc thng ip: Mt phng php nh tuyn

c gi l mt chin lc n ng, nu c ch l mt v d ca nhng tin nhn trong

mng bt c lc no. Chin lc chuyn tip khc c th c phn loi nh l mt phn l lt

v a ng nh tuyn, ty thuc vo cc thng ip c chuyn tip n mt s nc lng ging

trong tng bc nh tuyn hoc khi nh tuyn c thc hin cng mt vi con ng d nhn bit,

tng ng. Chin lc con ng duy nht l tit kim ti nguyn hn, k t khi h gi

s truyn tin n mc ti thiu i lp vi a ng hay l lt

phng php tip cn da. Tuy nhin, l lt t c kt qu tt hn trong mng li rt nng ng

kch bn lm vic [10], trong khi a ng nh tuyn to thnh mt s tha hip gia hai

thi cc. Bo m phn phc v phn loi nh thm cc n ng, a

con ng, v chin lc nh tuyn thot l, da trn xem xt trong chng ny. Gi s mt

l tng, chng trnh va chm truy cp min ph, cc thut ton m bo giao hng ca mt by nhng thng ip

sage, khi ngun v ch c t trong phn vng cng mt mng. Routing

thut ton b sung c th c phn loi nu h yu cu cc nt duy tr trng thi trong-

hnh thnh v nhim v nh tuyn lin tc, c gi l ghi nh trong vn hc.

N l thch hp hn trnh ghi nh ca giao thng trn bt k nt, nhng tuy nhin, nh

ghi nh lu khng dn n mt s phc tp nhn tng, iu ny khng phi l

mt phn quan trng xy dng cc giao thc tit kim ti nguyn. B nh ngay c trn cc thit b nh

d kin s tng theo cp s nhn trong tng lai, trong khi ti nguyn truyn thng s

vn l yu t hn ch.

4.3 Greedy Packet Forwarding

Cc thut ton nh tuyn tham lam gii hn quyt nh chuyn tip cc thng tin v lo-

cation ca nt hin chuyn tip, cc nc lng ging, v cc im n tin nhn.

Mi node trung gian p dng nguyn tc ny tham lam n ch, nu pos-

nhim, cui cng t c. Cc c im ca cc thut ton nh tuyn khc tham lam

vi tiu ch ti u ha p dng trong mi bc chuyn tip.

Khong cch gia mt nt S v chiu A

0

ca mt ngi hng xm nt A

ln ng ni S v im n D c nh ngha l s tin b (xem hnh. 4.1).

S

D

C

Mt

E

B

A '

F

d

G

r

r '

V. 4.1 Mt s chin lc nh tuyn tham lam c th c xc nh bi cc khi nim v tin , khong cch v

hng. V d, nt A l ngi hng xm ca S vi hu ht cc tin b v pha trc, B c t nht khong cch

n D v C l gn nht trong hng ti D

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H. Frey et al.

S

C

Mt

B

D

V. 4.2 Mt gi tin gi ti nt D s c gim xung ti nt A, v mi ngi hng xm ca A

(Tc l S v B) l theo hng ngc. Suy tuyn ny c th xut hin trong c hai khong cch trn v

chin lc chuyn tip tham lam tin da trn

Hng xm vi tin b tch cc c biu th l hng v pha trc. Th

phong ph trong hnh. 4.1 nhng ngi hng xm A, B, C, E, v F l hng v pha trc. Cc

nt cn li G c gi l theo hng ngc. Ngoi ra, tham lam

nh tuyn c th da vo khong cch, xem xt khong cch Euclide gia tt c

hng xm ca ngi gi S v cc im n D. Cui cng, phng php hng -da con-

Sider lch (gc gia hop tip theo, hin ti, v nt ch) t

ng ni ngi gi hin ti v ch.

Nhn chung, giao nhn tham lam da trn tin hoc khong cch xem xt cc nt trong

v pha trc hng resp. gn gi hn vi ch ch, do la chn mt nt trong trng

phng hng c th dn n mt vng lp nh tuyn. Do , nh tuyn khng th tham lam

m bo cung cp gi thm ch nu c tn ti mt ng i t ngun n ch. V

V d trong hnh. 4.2 c tn ti mt ng i t ngun S n ch D, tuy nhin, mt

gi cp ti nt D c gim ti nt A, v mi nt trong my bin p ca n

phm vi nhim v l theo hng ngc. Tnh hung nh vy c gi l ti thiu a phng,

v nt ni chuyn tip tham lam l dng li c gi l mt nt lm.

Phng php nh tuyn tham lam khong cch da trn vn loop-free, k t dis-

tm t ch l gim trong mi bc chuyn tip. Ni chung, mi tham lam

nh tuyn cc gi tin chuyn tip thut ton cc nc lng ging gn gi hn vi cc im du lch hoc trong vng

tin v pha trc nht m bo hot ng loop-free, trong khi thut ton tham lam

chuyn tip cc gi tin n ngi hng xm vi hng gn nht (v c th n khc

hng xm) khng loop-free [11].

4.3.1 Cc chin lc c bn c-Path

Vo gia nhng nm 1980 v Takagi Kleinrock [12] gii thiu v pha trc nht trong vng bn knh

(MFR), cc thut ton nh tuyn da trn v tr u tin tt c. Mt gi tin c ch n

D c chuyn tip n nhng ngi hng xm tip theo trong hng v pha trc ti a ha s tin b

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4 Routing trong cm bin khng dy

85

hng D (v d nh nt A trong hnh. 4.1). Vic s dng rng ri chin lc chuyn tip tham lam

bi Finn xut [13] p dng cc nguyn tc tng t nhng thay v xem xt khong cch

tin b, tc l mt nt chuyn tip mt gi tin n nhng ngi hng xm vi khong cch d nh nht

n ch (v d nh nt B trong hnh. 4.1).

Nu cng tn hiu khng th c iu chnh, n l mt la chn tt pht huy ti a cc qung co-

Vance trong tng bc nh tuyn, k t khi n c gng gim thiu s lng cc bc nhy mt

gi tin phi i du lch. Tuy nhin, ngay c khi cng tn hiu l mt tham s c nh, send-

ing mt gi tin n mt ngi hng xm xa xi khu vc bin gii ca kt qu phm vi truyn dn

trong mt xc sut cao hn cc gi tin b mt do suy gim tn hiu v nt di ng.

Hou v Li [14] quan st thy rng bng cch iu chnh cng tn hiu cc nc lng ging gn nht,

xc sut mt thng do va chm c th c gim ng k. H

xut gn nht vi s tin b v pha trc (NFP), trong mi nt gi cc gi tin

cc lng ging gn nht vi s tin b v pha trc (v d nh nt E trong hnh. 4.1). Stojmen-

ovic v Lin xc nh khu vc gn gn (NC) [15], m l mt sa i ca NFP

xem xt khong cch thay v tin b, tc l cc gi tin c chuyn tip n cc khu vc gn

ngi hng xm trong s tt c cc nc lng ging gn gi hn vi cc im n (v d nh nt C trong hnh. 4.1).

khc phc thng mi-off gia tin b v truyn thnh cng ngu nhin

phng php tin b (RPM) [16] bi Nelson v Kleinrock chn ngu nhin (thng nht

phn phi) mt trong tt c cc nc lng ging vi tin v pha trc.

Kranakis et al. la bn xc nh nh tuyn (DIR) [17], trong ngun hoc trung gian

n nt chuyn tip mt gi tin n node hng xm nm hng gn nht so

n ng ni ngi gi v ch. V d trong hnh. 4.1 nt C l trong

hng gn nht lin quan n ng ni lin nt S v ch D. By cn

mit mi n ny ti tng bc nh tuyn, la bn nh tuyn c gng gim thiu

Chiu di ng Euclid mt gi tin phi i du lch.

4.3.2 Ci thin Chin lc c-Path

nh tuyn tham lam da trn tin v khong cch c th c ci thin bng cch cho php mt by nhng thng ip

hin i theo hng ngc cho mt hop, tc l mt thng ip duy nht nu n c th

c a tr li cc nt ca cc bc chuyn tip trc [11]. Trong s kt hp

vi chng trnh ny, nh tuyn tham lam vt qua cc nt lm c mt xm 2-hop

bor gn hn n ch. V d trong hnh. 4.2 mt ip gi ti nt D

vt qua nt lm A, v A chuyn n ti nt B v B c hng xm

C m l gn gi hn vi D hn A. Stojmenovic v Lin [11] xut a l

khong cch nh tuyn (GEDIR), m l mt s ci tin v khong cch da trn nh tuyn cn

mit mi m quy tc lc hu.

T l phn phi cc thut ton nh tuyn hin c tham lam hn na c th c ci thin

nu cc nt trao i thng tin v cc nc lng ging ca h v do mi nt l nhn thc

ca hng xm 2-hop ca mnh (gi l 2-MFR, 2-GEDIR hoc 2-DIR v d) [11]. Cc

nt chuyn tip tip theo c la chn trong s tt c cc nc lng ging mt v hai hop. t c mt

chn hai-hop hng xm C, tiu chun chuyn tip c p dng mt ln na trn tt c cc one-

hop lng ging kt ni vi nt chn C.

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H. Frey et al.

S

Mt

B

D

C

E

F

V. 4.3 Cc ng dn c la chn cho mt tin nhn t ngun S n ch D l SABACBCEFD cho

thay th-GEDIR v SABCEFD cho ri nhau-GEDIR, tng ng

Ghi nh qua giao thng cng c th c s dng gim t l tht bi ca hin tham lam

cc thut ton nh tuyn. Lin v Stojmenovic [18] nh ngha thay th v nh tuyn phn chia

n, m l da trn cc thut ton nh tuyn GEDIR, MFR, v DIR, nhng al-

la chn thp chuyn tip cc nt theo hng lc hu hn mt hop.

C hai phng n duy tr thng tin trng thi trnh lp tin nhn, nhng khc nhau cc

cch nt lm chn nt hop tip theo. Trong nh tuyn tham lam ci thin bng cch la chn cng

n nate mi nt trung gian chuyn tip th i nhn c thng ip ti i-th tt nht

hng xm, theo cc tiu ch chuyn tip p dng. Nu khng c cn li

hng xm thng ip c gim xung bng nt chuyn tip, do , cc vng lp c th ng h

duced trong n ny ch l tm thi v gii hn bi mc nt ti a.

Trong nh tuyn tham lam ci thin bng cc chng trnh phn chia, mi nt chuyn tip tin nhn

c ghi nh bi tt c cc nc lng ging v tip tc loi khi b th c tip theo

hop nt ng c vin cho tin nhn. Mt node vi mt tp rng ca th v hp lon

nt didate s th cc tin nhn. n phn chia vn lp min ph, k t

mi nt s nhn c mt thng ip nht l mt ln. Hnh 4.3 a ra mt v d ni

GEDIR m rng chng trnh thay th v tch ri thnh cng, trong khi GEDIR cn

t lt t n s th mt tin nhn lm nt B.

4.3.3 Chin lc a ng v l lt-Based

nh tuyn cc chin lc m mi nt trung gian c chuyn tip cc thng ip c th

nhiu hn mt ngi hng xm trong hng v pha trc c gi l hn ch l lt hng

ing chin lc. L do ng sau thng ip truyn tha l tng

t l thnh cng ca chin lc chuyn tip hin. Mt thng bo gim ti mt nt lm

c th i mt con ng khc dn n ch ca n. Tuy nhin, thm ch hn ch di-

l lt rectional khng m bo giao hng.

Basagni et al. [19] xut cc thut ton nh tuyn hiu qu khong cch cho di ng

(DREAM), mt chin lc da trn hn ch l lt hng, i hi vien

orization trnh lp do chuyn cng mt thng ip nhiu hn mt ln. Ngun

v bt k node trung gian s chuyn tip mt tin nhn mt ln cho tt c cc nc lng ging mt-hop ca mnh

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4 Routing trong cm bin khng dy

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S

D

r

D

r

S

mt

b

V. 4.4 Cc node ch D d kin s u bn trong vng trn miu t (d kin

khu vc). (A) DREAM s chuyn tip tin nhn cho mi nt nm bn trong phm vi gc c xc nh

bi cc tip tuyn i qua S v cc khu vc d kin. (B) Trong LAR 1 chng trnh mi nt trong

khu vc hnh ch nht l mt nt ng c vin c th chuyn tip tin nhn

nm trong mt phm vi gc no n c ch D. Nh m t trong hnh. 4.4a, ny

phm vi c tnh ton t cc tip tuyn hng u t nt chuyn tip n d kin

din tch ca im n D, l mt vng trn tm ti D c bn knh phn nh max-

imum c th chuyn ng ca D k t khi cp nht v tr cui cng (tc l nt D c th c

d kin s u bn trong vng trn). c lp, chin lc tng t da trn

l hng v ghi nh cng c m t bi mt Ko Vaidya [20].

H xut v tr h tr nh tuyn (LAR), m ban u c d nh

h tr cc giao thc nh tuyn da trn phn ng topology trong vic tm kim cc tuyn ng trong mt hiu qu

cch. Giao thc nh tuyn hot thng xuyn s dng xc nh cc tuyn ng ngp lt mi c-

ngun tween v ch. LAR s dng thng tin v tr hn ch l lt

mt khu vc nht nh, gi l khu vc c yu cu. Ch c cc nt trong khu vc yu cu c php

gi pht hin tuyn ng pha trc. Hnh 4.4b m t khu vc yu cu c s dng bi LAR

1 n, tc l con ng khm ph c gii hn trong khu vc hnh ch nht cha

Khu d kin im D v nt ngun S. Cc LAR 2 n hn ch ng

pht hin cc nt vi khong cch n ch D ti hu ht s d ln hn

khong cch gia cc nt chuyn tip trc v D.

Stojmenovic et al. khi qut cc khi nim v hn ch l lt cho hng

distance-, progress-, v hng da trn nh tuyn tham lam v xc nh V-GEDIR,

CH-MFR, v R-DIR, tng ng [21]. tng c bn ca cc thut ton l

xc nh tt c "tt nht" nt next hop c th khi tiu ch chuyn tip l cn

chuc cho tng v tr im n tt trong khu vc d kin ca mnh. Cc phng php

khc nhau nh th no cc nt ny c xc nh mt cch hiu qu. R-DIR xc nh tt c cc nc lng ging

gii hn trong phm vi gc v b sung c th l hai nc lng ging gn nht nm

hng ti mt trong hai tip tuyn (xem hnh. 4.4a). Trong V-GEDIR, nt hop tip theo

c xc nh bi giao nhau s Voronoi ca cc nc lng ging vi d kin

din tch ca im n, trong khi CH-MFR tnh li ca cc nt ln cn

(Chi tit xem [21]).

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H. Frey et al.

Ngoi ra thay th v tch ri tuyn tham lam, Lin v Stojmenovic trnh

t ra mt lp hc ca cc phng php nh tuyn a ng tham lam da trn nhng khi nim [18]. Mt

nt ngun ban u v chuyn tip tin nhn cho c hng xm tt nht theo chn lc

s tiu ch. Mt s bn sao ca tin nhn c th i du lch cng mt vi nhn

ng dn, trong khi con ng c la chn l ty thuc nu ban u, thay th, hoc nh tuyn phn chia

c s dng. Trong phng php c tham lam gc (tham lam l mt trong nhng thut ton c s GEDIR,

MFR hoc DIR) mt tin nhn nhn c bng mt nt trung gian chuyn tip mt ln duy nht

ngi hng xm tt nht ca n (nu c) v tt c cc bn sao tip nhn s c b qua.

Cc nt trung gian trong phng php c tham lam thay th c tham lam v tch ri p dng

thay th ban u v tiu ch phn chia, tng ng, v d, nhiu bn sao ban u

thng bo u c i x nh mt thng ip trong cc thut ton ban u.

Routing 4.3.4 Energy-Aware

Sc mnh tnh ton (ngay c trong cc thit b di ng) ang gia tng nhanh chng, trong khi pin

i khng c d kin s tng ng k trong tng lai. Nu cng tn hiu c th

c iu chnh, cc thut ton nh tuyn cc b c th c gng gim tiu th in nng lng

s bng cch chn nt chuyn tip trong phm vi truyn dn ti u. Stojmenovic

v Lin [15] xut mt thc o sc mnh tng hp kt hp tn hiu suy gim ca

s m khc nhau, mt nng lng do bt u ln, va chm, truyn li, v cc bn

knowledgments trong mt biu thc ph thuc vo khong cch gia ngi gi v ngi

thu. Gi s rng cc nt b sung c th c t cc v tr ty gia

ngun v ch, c mt s lng ti u ca khong cch bng nhau trung gian

chuyn tip cc nt sn xut tiu th in nng ti thiu [15]. S lng ti u

cc nt trung gian c tnh t khong cch gia ngun v ch

v cc thng s metric sc mnh tng hp.

Kt qu ny c s dng xc nh cc thut ton nh tuyn in. Cc nt khng th c t

ty tin, nhng gi nh rng tiu th in nng cho cc phn cn li ca con ng bng

cc ti u nht, mi nt trung gian S la chn mt ngi hng xm gn gi hn vi F D thiu

mizing tng nng lng cn thit truyn ti cc gi d liu t S ti F v ti u

tiu th nng lng cn thit chuyn tip cc gi tin t F n ch D qua

r khong cch cn li

0

.

Power-routing s gim thiu tiu th nng lng, nhng cc nt duy nht c th

c la chn bi nhiu nhim v nh tuyn, m s dn n tht bi sm ca h. max-

imize s nhim v nh tuyn thnh cng, mt thc o chi ph c s dng trong [15] xc nh

cc thut ton chi ph nh tuyn. S liu ny l mt chc nng t l vi nghch o ca

cn nng lng pin, by t s min cng ca mt nt chuyn tip mt gi tin.

Mi nt chuyn tip chn mt ngi hng xm gim thiu cc khon chi ph v s liu

chi ph c tnh cho con ng cn li. Cui cng, nng lng-gi-nh tuyn c iu tra

, m c gng gim thiu s kt hp ca sc mnh v chi ph metric.

Kuruvila et al. [22] xut nng lng ni a ha v chi ph thc cc chng trnh nh tuyn

da trn khi nim ca s tin b theo t l. cp n hnh. 4.1, cho php cc nt cur-

ti ang nm gi cc gi tin c S, cho F l mt ng c vin hng xm ca S, v cho D l

ch. Hy jSFj D r; jSDj D m, v jFDj D r

0

, Vi r

0