Chuyên đề tốt nghiệp: Truyền thông tin và những ứng dụng của mạng VANET

BO GIAO DVC DAO TAO TRIAING DAI HQC THANG LONG --o0o-

CHUYEN BE TOT NGHIVI

TRUYEN THONG TIN VA NIIING irNG D1VNG CUA MANG VANET

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: ThS. HOANG TRQNG MINH : NGUYEN VAN CONG : A14025 : TIN VIEN THONG

GM() vial' huirng din Sinh vien air hit'n MA sink vial' Chuyen nghanh

HA NO! - 2013

MVC LTC

1

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Lta MO tau

2 CHU'ONG 1. TONG QUAN Vt H$ THONG MANG VANET (cid:9)

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1.1. GIOI THIU CHUNG Vt MANG VANET

2 1.1.1. KIthi ni0m. (cid:9)

2 1.1.2. Tgi sao co hf thong Vanet? (cid:9)

2 1.2. NGUYEN TAC CO BAN VA THACH THITC (cid:9)

5 1.3. LJCH St' VA SU' PHAT TRIEN CUA VANET (cid:9)

6 1.3.1. Tit dA4 den' gifia nhiing nein; 1990 (cid:9)

7 1.3.2. Tit mkt nhiing nOm 1990 den nay (cid:9)

11 1.3.3. Kit quci cia ceic dv an hien tai (cid:9)

16

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1.4. ICET LUAN

17 CHID ING 2. TRUYEN THONG TIN TRONG VANET (cid:9)

17 2.1. GIQI THEW (cid:9)

18 2.2. DO LUVING Vf mi HIN HANH (cid:9)

19 2.2.1. Cam &in trong xe (cid:9)

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2.2.2. Ccic hf that' Ig dinhvi nhtf Li mOt nguiejn thong tin.

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2.3. TRUYEN TAI THONG TIN...

26 2.3.1. Ccii thien viec kit not mang (cid:9)

28 2.3.2. Truyea tai thong tin (cid:9)

30 2.4. TONG HIP CAC PHEP DO (cid:9)

33 2.5. TONG H1P D' Lieu DjA LY (cid:9)

43 2.6. ICET LUAN (cid:9)

44 CHVONG 3. NHONG ONG DUNG CUA VANET (cid:9)

44 3.1. GIen TIM (cid:9)

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44 3.2. HAN CHE

45 3.2.1. Khci rang (cid:9)

46 3.2.2. Kit not (cid:9)

49 3.2.3. Cgnh tranh. (cid:9)

50 3.3. (ING DVNG (cid:9)

51 3.4. BIEN HOA TRUYEN THONG (cid:9)

52 3.4.1. He fixing tip trung khcich chri (cid:9)

52 3.4.2. Mo hinh ngcrng haw (cid:9)

55 3.4.3. TnOn thong trong VANET (cid:9)

57 3.5. XAC SUAT, TAP HQP THEO VUNG (cid:9)

57 3.5.1. Phcic thcio FM (cid:9)

58

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3.5.2. Cc c ban phcir thcio cho kip h9p dir lieu trong VANET

59 3.5.3. Phcic than trgng that mem (cid:9)

60 3.5.4. Binh thOnh khu vitc ion hon tong h9p (cid:9)

61 3.5.5. Nghien csiu zing dim (cid:9)

62 3.6. TAP HQP THOI GIAN DI CHUYEN (cid:9)

63 3.6.1. nip h9p d4a3 Ira clam mOc (cid:9)

65 3.6.2. Danh gici chilt hi9ng thong tin (cid:9)

66 3.6.3. Ceti' 4 tnic king h9p ∈ me' c (cid:9)

67

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3.7. KET LUAN

68

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TONG KET

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THUAT Nal VIET TAT

71 TAI LIEU TRAM 'MAO (cid:9)

DANH MIJC IliNH ANH, BANG BIEU

3 Hinh 1.1 Bieu di mink hga cic cinh lbio nguy hiem (cid:9)

10 Hinh 1.2 MO hinh tong quan ye clic giii phip VANET (cid:9)

12 Wnh 1.3 Vi dy h§ thing the nghi§m tgi Michigan (2008) (cid:9)

Bing 1.1 I3in di ctia VSC-A eng dgng an town vi kich bin cic vy tai ngn 14 dutrc quan tam nhit (cid:9)

18 Hinh 2.1 frng dieing phi bien dip tren VANET (cid:9)

23 Hinh 2.2 Trao diii thong tin ngim (cid:9)

33 Hinh 2.3 Tang him tOc (10 alit xe teen mlii phan dogn trong SOTIS (cid:9)

35 Hinh 2.4 H§ thing quan sit hru luvng (cid:9)

36 Hinh 2.5 Tang kip nhim cic bin ghi CASCADE (cid:9)

38 Ifinh 2.6 Cay hi phan (cid:9)

42 Ifinh 2.7 Thivi gian di Tour Eiffel den Arc de Triomphe (cid:9)

43 Hinh 2.8 M§t mting luid duirng phan clip trail tilting. (cid:9)

47

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Hinh 3.1 M§t 'lc suit dui kit not vo tuyen

48 Hinh 3.2 Phi bien de lieu bing cich se dyng cic chuii vi xe di dOng (cid:9)

49 Hinh 3.3 Anh hir&ng cult cic don vi ben ii throng (cid:9)

54 Hinh 3.4 Phan phiSi cic thiet bi ngang hing teen mOi phin doin duirng (cid:9)

58 Hinh 3.5 The h§ vie how nhit cis tip hip phic thio FM (cid:9)

60 Hinh 3.6 wet him phic thio & tiling thii mem (cid:9)

62 Hinh 3.7 D§ chinh xic cis tin him & xa

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64 Hinh 3.8 Ting Nip diem mic (cid:9)

66

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Hinh 3.9 Thong tin ci sin & cic cip dO khic nbau

CHUONG 1. Tang quan vi he tilting mang Vanet

Ltla MO DAU

Ngay nay voi xu the ph& trien mph me ve tong nghe thong tin, dien tai van thong ket hqp v6i sq da clang va phong phd ye phuong tien k3 thuai da tao nen nhung hinh thai phat trien mai nham phuc vu cho den song con ngu6i. Thong tin lien lac duqc m6 rung v6i nhitng rinh vqc mai hira hen nhieu sq phat trien. Mang di dung thy bien trong xe hai cling la mOt rinh vqc dang duqc cac nu6c phat trien nghien ciru va dua vao sir dung nhi ► dua lei nhfang hieu qui, nhlang diem nhin m6i trong bu6c phat then cua xe hai. Be c6 the hieu has ve sir ph& trien, nhung buem tien cilia rinh vqc nay tOi mu6n giai thieu t6ng quan ye nhung khai niem, t6ng quan ve m8 hinh by thong cling nhu la ntang cong nghe duqc sir ch,mg trong m8 hinh mpg trong mpg di dOng thy bien cho xe hai (VANET). VANET (Vehicular Ad-hoc Network) la mOt (rug dung mang nhu the. 1)6 11 mOt he thong mpg s(r dung cac giao tiip khOng day phan tan gift nhieu diem truy c#p Ichic nhau ma khemg can ten bit dr mOt cc; s6 ha ding c6 djnh lac). Bit cu thiet bj cam tay vii co djnh nio nhu dien thoai di dOng, laptop, may nhin tin, cac tram v8 tuyen ca so deu c6 the la mOt kenh thong tin trong mang VANET tao thimh mpg town ciu, rung khip mqi nai. Cic thiet bj nay c6 the tich hqp vao cac d6i tuqng di chuyen (xe cu, tau thuyen,..) ho#c tl#t co djnh o cac diem khien cho viec truyen thong ce the dies ra o mqi lfic, mqi nai. M8i phuang den tham gia giao thong (duqc tich hqp mOt thiet bj c6 khi Wing kit n6i day) lit( thinh mOt nut ciia mpg.

Bao cio bao gam ba chirong:

Chuang 1: Glen thieu chung ve he thong Vanet va cac nguyen tic ca ban va

thich thirc ctla VANET, trinh bay mOt ljch sir ngin gun cac hog dOng cilia VANET.

Chuang 2: M8 to cac phuong phap de ph6 Wen thong tin va t#p Nip trong

VANET can thiet de h8 trq cac img dung hieu qui va tien lqi.

Chuang 3: Duqc xay dqng tree chuang 2 va tip trung vao cac img dung "Meng

an tan" do d6 muc tieu chi yeti la hieu qui va tien lgi.

MOc (cid:9)

lqc nghien ciru de hall thanh chuyen de cim minh, nhung do !den thirc va th&i gian con hp chi nen trong chuyen de t8i khang tranh kh6i nhfkng thieu set. Toi rat mong nhon duqc cac d6ng g6p, nh#n xet tir phia flay co va cac ban.

CuOi cling t8i xin chfin thimh cam an sir huong din va taco dieu kien ctla thiy

Holing Trong Minh trong su6t qua trinh t8i lam bito c.ao nay!

CHUONG 1. Ting quan ver ha th6ng mang Vanet

CHU•ONG 1. TONG QUAN Vt HE THONG MANG VANET

1.1. GIO1 THIEU CHUNG Vt MANG VANET

1.1.1. Khdi niflm

VANET (VEHICULAR AD-HOC NETWORKS) li mpg trong da cic xe (vehicule) se duqc trang bj thiet bj thu/phit, chang se ter thinh cic node nhu trong mpg ad-hoc. Cic xe se lien lac vai nhau (Car-to-Car Communication), hay M2M (machine-to-machine communication) de chia se thong tin lin nhau. ThOng tin ye traffic, ye tinh trang kit xe, thong tin ye tai not giao thong, nguy hiem can trinh...M0 chile xe ding c6 the trb thinh mOt Relay Node a chuyen tii th8ng tin cho xe khic...VANET sfr chum chuin Wifi 802.11. 1.1.2. Tgi sao eó h? thong Vanet?

— Cong nghiap xe ngiy ding phit trier.

—S6 vu tai non giao thong, On tic ngiy tang tang.

—Cic phuang flan thiet bj phut vu cho giao thong chtra tai uu...

1.2. NGUYEN TAC CO BAN VA MACH Marc

Khii niem co bin cda VANET la khang phi= tap: thuc thi tram deg nghe WLAN dian rang vi khong qui dit, tart li ket n6i giva cic may tinh vii nhau hoot vii intemet, vi vai nhieu cii lien no duqc ip dung len xe cO. Diu lien, thong to xem x& den co hOi. Neu cic phuong den c6 the truyen thong tnrc tap vii nhau vi v6i co so ha Ling, meo hinh hob toin moi cho nheng (mg clang an toin cba phuang den 06 the se duqc hinh thinh. Thtl hai, nheng thich thac mad da thrqc too ra Uri phuong tian tee do) cao vi mad trubng tic dOng llrc lan. Thir ba, nheng yeu ciu can phii c6 Ye an loin d6i yeti cic frog dung mad, bao gim nheng 10 vqng mad cho phin phii gei tin cao vi dO trg gei tin thip. Han naa, phin (mg mb flint cM khich hang vi su gin sit caa ha thing giim sit dem lei 10 vqng cao ye an ninh vi sir rieng tut.

Them chi ngiy nay, chiec xe too ra vi phial tick luqng bfm de lieu, mac thl de lieu nay thubng china trong mOt chi& xe duy nhit. ce VANET, dim nhin (kha Whig nh$n biet xung quanh) cue cic phuang tian giao thong vi cue lii ACC duqc tang len ding Ice. Truyen thong VANET c6 the thuc hian true till) gala cic xe nhu Owen th8ng "mOt buoc", hoot phuang tian ce the truyen lai bin tin, do da cho phdp truyen thong "da Woe. De tang yang phtl sang hoc dO ben yang cult truyen thong, chuyen tie') lc ben thrtmg c6 the duqc trien khai. Co so ha tang ben throng clang c6 the duvc sfr dung nhu mOt deg vio internet vi do da de lieu vi th8ng tin net cinh c6 the duqc thu thap, luu Ire vi "6 mqi nor, vi du ca so ha ling mang cue coag nghe ditat town dim may sip tad.

2 CHISONG 1. Tang quan ve he thong mung Vanet

N6 dim bao ring mpg lien kit gift cic xe se thfic diy manh me b6i su phong phi caa cic Ung dung co the dugs kich hoot. Truoc het, cic ting dt,mg an toan chb dOng, tirc la cic ting dung phong ch6ng tai nun se duqc hiding lqi mOt cich true dip tfr truyin thong. Thir hai, bang cich thu thilp dtt lieu twig thii giao &Ong ter mOt yang rung han, luu luqng giao thong c6 the dirge cal thief', thstri gian di chuyin c6 the duqc giim cling nhtr nheng lchi thii hY cic phuang lien. Nhu n6 di duqc ghi chinh xic nhu cic nguyen 1 cult he th6ng giao th8ng thong minh (Intelligent Transportation System World Congress) nam 2008: Tiet kiem th6i gian.

Cic 16p (mg dung "an tan" vi "hien qui" c6 the duqc sfr dung de phan loci cdc Ung dung dlra tren mix dich chinh cia chimg. Tuy nhien, cic khia can't an toile vi hieu qui khong the quan niem nhu cic tinh Wing tech r6i hoiln town. R8 tang, tai min xe c6 the din den tic nghen giao thong. MOt bin tin th8ng bio mOt vu tai non ce the duqc xem nhu la mOt thong bio an town * diem quan sit caa xe gin d6. Ban tin Wang tu c6 the duqc nhin cic phuong lien 8 xa han nhu mOt diu veto de tinh toin mOt 10 trinh thay the trong mOt (mg dung hieu qui giao thong.

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Ifinh 1.1 Bilu (IS minh has cdc cdnh bdo nguy hiim

Trong khii niem don giin, thiet ke vi tan khai cic VANET la met luc kq diy thich thirc ve ky thust va kinh to Mich thirc chinh ve ky thuUt bao g6m cic vin de sau:

— Cie Scil dam c6 ham cda kenh v8 twin dien. Cic kich ban hien nay mia VANET vbi nhieu die diem khong thu0n lqi cho vies phit trien truyen th8ng khong diy, vi du: nhieu doi tuqng phin inh co the lam suy giam dO mph vi chit luqng ctia song tin hieu nhen duqc. Ngoai ra, do tinh di dOns cia cic dii

CHISONG 1. TOng quan ve hg thong mong Vanet

trung xung quash ho#c chting tv gfri vi tv nkftn, hilt' Ong mb din phii duqc dua vio sv tinh toin.

trung trvc tory& vi (cid:9) —Thies mOt sv quin (cid:9)

don vj phOi bqp. Vilc sir dtmg ding bing vi hilu qui bang thong mkt kenh lchang day li mOt nhilm vp kh6 khan trong mOt mong ur t6 chrrc vi phan cep hoin toin. Vi$c thieu mOt thvc the c6 khi Wing ding bO h6a vi quip cic sv ki/n truyen tid cara cic of khic nhau co the din den sir dung kenh kern hilu qui vi din den s6 hrqng lon cic vv va ch?m g6i tin.

—Mb di ding cao, yen (cid:9)

khi Ring mfr ring, vi sw da ding cast Min kiln mdi trnimg. Nheng thich th(rc cia mOt mong tg t6 clac plan cep duqc die bilt nhin manh den t6c dO cao. Tinh di dOng cao li mOt thich thirc cho cic thuig toin t6i uu 1#p nhim s6r dung tot ban bang thong kenh hoc sb dung cic tuyen dutmg duqc dinh nghTa tru6c de chuyen tiep thong tin.

—An ninh vi nhu cis rieng hr vi cfc m6i plan tam. C6 mOt thich thirc ve can d6i gifts nhu ciu ve bio m#t vi tinh rieng tu. MOt mkit, ben nh(in mu6n dim bio ring c6 the tin liking ngu6n thong tin. Wit khic, sir tin luting d6 c6 the mau than voi cic yeu ciu rieng to cfia ben gtli.

—Tien chain boa so (cid:9)

limb ding. C6 mOt nhu ceu cho truyin thong tieu chuin cho phep VANET lim vile qua cic kieu khic nhau vi cic chuin caa OEM. Tuy nhien, chic chin ring OEM se mu6n too ra vii sv kbic hilt v6i cling nghl VANET. Nhung raw tieu niy li c6 ye se khi kh6 khan.

Mich thfrc chink ye mat klub ti xi

—Phan tich vi xic dish &Nov cic lqi ich cult VANET cho an toils giao thong vi hien qua vin tii. Cho den nay, rit it vile da duqc thvc hi¢n de dinh gia tic dung c6a VANET nhu mOt ngu6n thong tin ve hinh vi lii xe. Re ring, nhung thich thirc lien quan trong vile giii quyet vin de dinh gii tic ding li m8 hinh c6a cic khia conh lien quan den yeti t6 con ngutri.

—Phan tich vi xic dinh thrqc dic m6i (plan he chi phi - lqi lick adia VANET. Do thieu cic nghien ciru ye lqi ich c6a VANET, v#y plan tich chi phi - lqi ich kh6 ce the duqc thvc hiOn. Chien luqc trien khai thiet ke cho load hinh VANET li kitting dra tren mOt cc s6 141 tong hoc mOt nhtt cung cop dich vp nio. Vile thiet bj VANET ce dirge hay kh8ng con phv thuOc vio cic d6i tic truyen thong, cic hi thong mong hiln thOi c6 the h8 trq duqc hay khOng.

—Nhing VANET trong kJ& trac hi thong giao thing thing minh. VANET 0 la mOt phlin cua mOt hi thong giao thong thong minh noi mi Wing yes t6 khic duqc sinh ra boi diet' khien den giao thong hay cic cic load bin tin bio

CHUt5NG 1. TOng quan ve he thong mpg Vanet

hieu khic nhau. COng nhu vay, giao thong ci nhan vi Ong cling phii duac nim trong tii khoin trong mOt kiln cich chung. Bei vay, he thing hqp tic Nit sir cin duqc phit triin.

Nhu co the thiy tfr danh sich 6 tan etc ring (twig, ky thuat vi vie khia cunh kink to xi hOi, linh Arc (mg dung xe vi cic Ong nghe lien mpg dua tren ding nghe tren mOt no lirc lien nginh trong truyin thong vi mang, thiet bj dien ter tong xe, quin vi van hinh throng b0, cling cep cic th8ng tin vi dick vv. Do de VANET ce the duqc xem nhu li mOt phin quan tong cia he thing giao th8ng dieing minh (Intelligent Transportation Systems) (ITS).

Trong 'chi nhiiu du in khic nhau da thio luan chi& luqc tan lchai oho VANET, cic nghien c(ru chi yeti giii quyit nhitng thich thee ky thuat. Hien nay, mOt sir thay dii to rich dip can "ter dm% led" co dien Bing cich tap can "te tren xuong" Ly tueng nhit, ci hai phuang phip tiip can cutii ring se gap nhau• nhang gi duqc goi li mOt yeu ciu cho viec tan khai mang lui lqi ich co the duqc hi trq bOi nhing tier b0 cong nghe. 1.3. LOCH sir VA skr PHAT MIEN CUA VANET

Lich sir cea viec sir dung song v8 tuyin vi hing ngoai cho truyin thong gifts xe vei xe vi xe vei ben dueng gin lien vei sir phit trim ctia 14 thing giao thong th8ng minh. Nhu them khio trong Shladover vi tong Lasky vi Ravani, cic khii niem ca ban oda tu dung Ma dueng b0 nhu viec se dung the ky thuat truyin %Ong vi dieu Ichien di giao thong duting b0 an tan, hieu qui vi than thien vei mOi truing.

Sau de, vac cam' nheng am 1960, he thing tu dOng hes dating b0 dva tren song

v8 tuyin duqc phit triin vi cheng minh Ki hY do, co rat nhiiu de lieu dugs quan sit:

Chi di chinh li an tan, hieu qui vi than thien voi mOi trubng, tong tam lien tuc thay doi theo thin gian. Vi du, trong thei gian diu he thing hueng din tuyin dueng da duqc dieu tra. Sau do, he thing thu phi, nghien ciru lii xe tu dOng tre nen ph6 ban. Nghien ciru vi phit trier o khu vuc khic nhau, chi yiu 6 my, Nhat Bin, vi Chau Au, mi can o cic nai khic tren the giOi cing co anh huong. l>e tii de duqc dinh diu bei sir tap trong 'chic nhau cia 8 t8 vi cic cling ding giao thong van tii.

MOt chi di nhit quin theo thei gian li "ngan sich - ai se tri phi?". MOt mat, nginh cong nghiep 8 to vi dien ter nghi ng6 cic ca se hu tang dog rung cho he thing dueng cao tic thong minh (Intelligent Vehicle - Highway Systems) (IVHS) se khong bao gib thich hien thuc. Mat khic, cic dan vi chi quin dueng cao tic nghi nge lieu tong nghe IVHS se cung cep giii phip thuc ti cho cic vin di dueng cao tic thqc sir.

Trong phin du& day, se di cap din cic hoot dung buec tien quan tang lien quan

din VANET.

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CHISONG 1. Ting quan ve hg th6ng mane Vanet

1.3.1. TIr &iu din giea nhihog nano 1990

O My, mot ho thing hutmg din &Ong dien to (Electronic Route-Guidance System) (ERGS) d8 duqc de xuit trong Rosen: "He thing djnh hutmg diem den. Ngutri dieu khien xe nhap vito mOt mA, dal dien cho dja chi dich c0a minh vao thiit bj xe. Sau d6 khi phuang tien tien den mil diem giao ma dich duqc chuyin den atic tram ben dtrong tai de n6 duqc giai ma, theo mOt chtrong trinh ltru tat, va mOt chi din dinh tuyen duqc truyen lai cho chiec xe."

He thing truyen thong sbr dung tin só 170 kHz clOng Ang-ten yang duqc lip d*t tai nut giao %Ong va gin vao phia sau caa xe. Tic dO truyin catlieu bao cao la 2000 bit/gialy. Nhung nhang n8 luc ERGS bj chim dirt do cac ca so hu tang ben duong dit tien.

Tai Nh.t Ban, he thing dieu lchien giao thong 8 te tan dien (CACS) duqc thuc hien 1973-1979 do ca quan deg nghiep Khoa hac va C8ng nghe dui BO Thucmg mai va C8ng nghiep Quic ti (MITI). Muc lieu cua CACS duqc trinh bay trong Kawashima vin con hien luc sau han 30 Min:

—Giant un tic giao thong dubng Xi;

—Giam khi thai gay ra bbd su tic nghen giao thong;

—Phong ngta tai non;

—Nang cao vai fro cling ding va xa hOi cila 8 t6.

Be flat duqc muc lieu nay, bin muc tieu thuat di duqc de ra:

— Huang din lai xe di then cac tuyin chgmg thich hqp nhit de tranh On tic va 8

nhiim khOng khi;

— Cung cep th8ng tin lieu ich de hi trq lai xe an town;

—Uu tien cac xe ding cling hotic truing hap khan cep;

—Cung cap thong tin kip thin cho ngutri lai trong throng hqp khin cap.

Cac du an CACS ding duqc thuc hien thi diem vei 98 thin bi ben dtrong A. 330 xe tht? nghiem (Nakahara vi Yumoto). Dii vai truyen thong ben throng thi xe, cac tram ben dubng str dung Ang ten Ong con cac phucmg tien giao thong sa dung Ang-ten 101 cho tic dO truyen tai ctia bao cao la 4.8 kbps.

Tai chat' Au, de an Prometheus (chuang trinh giao &Mg chAu Au vai gia cao nhit chua mang lui hien qua vi an tan) ichoi xutmg vao nom 1986 va ra mit nom 1988 c6 * nghlit kich thick host ding nghien dru va phat tan trong rah vuc deg nghe th6ng tin va twin th8ng di dung cho xe c6 ding ca va nhang con duOng. Prometheus di drat hi trq boi 19 quic gia chau Au vb. cac Oy ban cling ding Chau

CHYONG 1. Ten quan ye he thOng mpg Vanet

Au (Walker nam 1992; Williams 1988). Nhu vi du neu trong Gillan, Prometheus di duqc t6 chi= tai cac he thong khhc nhau, bao g6m:

— PRO-CAR: lai xe

trq bb i he thong dien tb;

— PRO-NET: truyen thong gitta xe yeti xe;

— PRO-ROAD: truyen thong gifts xe va m8i trutmg.

Trong Prometheus, truyin th8ng gitta xe va xe (long met vai Ire n6i b#1: bao cao cat' Dabbous va Huitema vin c6 the duqc chu Sr cep nh#t trong nhieu khia canh. Dabbous va Huitema phan Lich cac yeu ciu truyen thong Ara tren ldch ban dien hhih, vi du cho chin ttp that' &Si lin &Ong. Gii sfr mOt chain luqc quing ba dinh kjr va you ciu dO chinh xAc khoing cach va chum, ho chi ra ring met danh gin th#n tong t6c de truyin ban tin tang thai cda mii xe se djnh ki gfri 20 phien truyen tren mil giay ciut m6i Dabbous va Huitema cang cho thiy cac neu gam di you clu ve de chink xlic khoang cach va chum va gioi thieu cac phuang phap du dam 05 the lam Ohm ding ke s6 lin you ceu truyen tai. DA duqc tip trung tren clic he thong hog ding 6 bang tin 60 GHz.

Su quan tam trong truyin thong gifts xe v6i xe tilp top 6 Nh#t Bin va my. cuoc khao sit trong Kawashima trich din hai bin bio cao thu#t cis JSK hiep hOi cling nghe dien tfr cho lai xe va 8 to (Association of Electronic Technology for Automobile Traffic and Driving) duqc xuit ban Nilo nam 1986 va 1988, Wong Ong, lc& qua thil nghiem truyen th8ng gitta xe vai xe. 6 My, nhu duqc nett trong Shladover, mOt trinh dieu khien chinh xuit hien de to ding lai xe va nhieu phuong den. Trong Sachs va Varaiya, cac you cau va thong se ky thuit de truyin th8ng giita xe v6i xe vi gitta xe yeti thiet bi ben diking de cho xe to gong duqc trinh biy. Tong kit du in hoot gag cha thtri ki nay tai My, Chau Au, va NIgit Ban cling nhu nhin ve twang lai doi vai he thong throng truyen cao tec th8ng minh (Intelligent Vehicle-Highway Systems) &gm dua ra beri Jurgen.

1.3.2. Tw min nhang nans 1990 din nay

Nth sau cha nhiang nam 1990 la cet mec quan tong ghi lai met su thay doi 16n. Kit qua An ttrong ye trinh dieu khien hqp tic dOc 1#p duqc chimg minh tai San Diego, bin gioi thieu cOa cac dei tac California cho nang cao vfn tIi va doting cao tec (Advanced Transit and Highways) (PATH) vho nam 1997, giai dap 2 giai thieu ye nang cao tinh an town phucmg den (Advanced Safety Vehicle) (ASV) vho Mtn 2000 tai thanh phi Tsukuba, Nh#t Bin, va trong du in PROMOTE CHAUFFEUR European. TOp trung sau de chuyen tfr lai xe kit hop to quan sang he thong trq trinh dieu khien hqp tic. Ti My cac sang kill phucmg tien thong minh (Intelligent Vehicle Initiative) (NI) trong nhiang atm 1998-2005 (Hartman va Strasser ) t#p trung vao an tohn hieu qui hqp tac. Tai chau Au, cac du in CarTalk vi FleetNet cba Franz nghien

CHUONG 1. Tong quan ye he thong mong Vanet

ciru ding nghe va cac (mg dung he trq hqp tic Idi xe. T31 NhUt Ban, giai don 3 caa dg an tiring cep an tan phuang lien cling th6a then vai tr6 cult truyin thong lien phucmg tien de he trq hqp tic lai xe.

Sq thay del tin 96: 5.9 GHz DSRC

IChai niem ve VANET di bi inh huong bei nhtIng lien b0 trong Ong nghe va tieu chuitt hea ke tfr gitta nhting nam 1990. Nim 1999 la mOt "sir thay dei tan se" xay ra khi 1:Jy ban Truyin thong lien bang my phis be bang thong 75 MHz cua did 5,9 GHz cho truyin thong tam ngin chuyen dung (Dedicated Short-Range Communication) (DSRC).Thuet net truyin th8ng tam ngin chuyen dung (Dedicated Short-Range Communication) di duqc sir dung nhu mOt tht4t net tuang 14p ve Ong nghe cho =yen thong khong day tam ngin gifts cac xe va ca s8 ho ting.

MOt rim sau, ASTM International thinh lep met nh6m lam viec de ghat trien cac yeu caw ve tieu chum DSRC tuang (mg. Trong nim 2001, Uy ban tieu chuin 17.51 cut ASTM chcm IEEE 802.11a la c8ng nghe v8 tuyen nen tang cho DSRC. Cac lieu chitin Wang ting di duqc dua ra trong nam 2002 vi sM di vac nam 2003 (ASTM E2213-03 2003). Cac ap lqc phai sir dung kenh duqc giao va tinh kha thi ¢ua cac deg nghe Ara chuin IEEE 802.11a thi lam tang ding ke cac hoot dung nghien cuu va phat tan. DUc biet, cling deng mong di dOng quan tam den chili de caa ming luoi xe di duqc hei sink. Nim 2004, IEEE bit ttiu deg viec stla 661802.11p va tieu chuin truy cUp lchong day trong m8i tramg xe CO (Wireless Access in Vehicular Environments) (WAVE) dqa tren cac lieu chitin ASTM (Jiang va Delgrossi). Dir an truyin thong an town phucmg On (Vehicle Safety Communications) (VSC) duqc he trq ben to ch(rc do (CAMP), cuc quan trj luting an town va ch?m (Crash Avoidance Metrics Partnership) (FHWA), va ban duting cao tec lien bang My (US Federal Highway Administration) quart ly an town giao th8ng dtrong bO My (US National Highway D•ajjic Safety Administration) (NHTSA) khao sat ccIng nghe DSRC 5.9 GHz dang n6i trong nhUng nam 2002 den flint 2004 va ket luin ring phuang phalp dip clura tren chuin IFFF, 802.11a se c6 the M trq hiu hit cac (mg dung an town ma VSC di chcm. Cac bao cao cu6i cling mkt VSC (VSC 2006), cOng dun ra met ckh rO rang nhttng thach &tic cna truyen th8ng c6 dO trg thep vi if& sin sing cao colt cac kenh vo tuyen cling nhu cac yin de lien quan den Icha fling caa kenh nei chung. Nam 2004, HOi thao qu6c to ACM diu lien ve mong xe CO bit djnh (Vehicular Ad Hoc Networks) di din ra Philadelphia, sau de thuUt net "VANET" di duqc det ra.

Cac dy in Mtn tai vi host dung Trong phin nay, di cep mOt cai nhin teng quan kh8ng day du ye cac dir an VANET dang dign ra va cac hoot dung 6 chau Au, Nht Ban, va Hoa Ky. Met cal nhin

CHISONG 1. 'fling quan ve he thong mung Vanet

t6ng quan cho they mirc dO hoot dung cao trong linh vvc nghien cuu vi phit tan VANET vi de chirng minh li cic deg nghe truyin thong khong day duqc bio dim li ca so cua lieu het cic hout Ong cila VANET tren toin the gioi (hinh 1.2).

Trong chuang trinh khung se 6 cua EU, ben dv in duqc bit dau trong cic linh Arc ce lien quan den VANET: COOPERS, CVIS, PReVENT, vi SAFESPOT. Dv in he thong hqp tic cho an toil) duOng b0 th8ng minh (Intelligent Road Safety) (COOPERS, 2006-10) t#p trung vio img dung vin thong tien tier cho quin hqp tic giao th8ng. Tir gee go truyin thong, th8ng tin ch6 yeu lit truyin thong gitta xe vi cic from ben throng vi s>3r dung lieu chain CALM nhu giao dien truyin thong hung ngoui CALM. CALM li ISO TC 204 (ITS) Working Group 16 (Communication) trong "giao dien kheong day lien tic cho khoing cich tittnmg binh den". CALM nham muc dich trq truyin th8ng lien tic cho xe bang cich sfr dung cic phuang tien truyen thong khic nhau vi cic giao dien truyen th8ng. Cic dv in he thong co ser hit tang phuang (CVIS, 2006-10) di tip tien hqp tic (Cooperative Vehicle-Infrastructure Systems) trung vio phit trier vi th(r nghiem trivet' thOng cfia phuang tien vol ca s8 hu tang vi theo lieu chat' CALM. CVIS lam cho vies sir dung WAVE WEE 802.11 c6 lien quan giao dien duqc hieu lii giao dien M5 (d6i voi "Microwave 5 GHz) trong khuen kh6 CALM. Dv in SAFESPOT (2006-10) nhim muc dich thiet ke hu thong hqp tic xi cho an tan &gong bto dva truyen th8ng gitta xe Wei xe vi xe vOi ca sO hu tang. Cic deg nghe truyin th8ng duqc s>Sr dung trong dv an SAFESPOT li IEEE 802.11a/p. Dv in PReVENT (2006-08) giii guy& phit tan cic Ong dung an toin dv plitong vi c8ng nghe trong dv an PReVENT tick hqp, cic dv in nho WILLWARN (Wireless Local Danger Warning) t#p tning vio cic cho de call truyin th8ng gift xe v6ri xe vi gitta xe yeti ca so hu tang. He thong WILLWARN dva tren IEEE 802.11a/p vi di sir dung nen tang truyin thong phit trien b Dirc do; in Network on Wheels (NOW). Ngoii ra, dv in Secure Vehicular Communication (SeVeCom, 2006 din nem 2008) di duqc dinh rieng de xic djnh cic mei de do vi quy djnh cu the phuang phip vi Icien trac de dam bio truyen thong xe Icheng day.

CHIANG 1. Toting quan ve 4 thOng mpg Vanet

Hinh 1.2 MS hinh tong quan 4 cdc gitii phdp VANET

Hien nay, theo chucmg trinh 7 khung, huang ten cac thtl nghiem rinh voc duqc tai trqi, dac biet 11 do in PRE-DRIVE-C2X dang chitin 1)1 xay dung cac kh8i an that cho thir nghiem thimh c8ng hoot dung cua VANET a chAu Au.

TO Nhat Bin, mOt tieu chwin a xe ca tilt truyin thong voi co at ha tang da duqc c8ng biS Mtn 2001 vi goi la "Dedicated Short-Range Communication System" (ARIB 001). He thong hoot dung 0 an s6 5,8 GHz, duqc doa tren da truy nhap phin chia theo thbi gian (TDMA) vi trong phom vi 30m. Moc Bich chinh cua he thOng la stt cb,mg trong vier thu phi dies fil nhtmg da duqc tan khai de h8 trq cho cac dich vo 'chic (ARIB 2004). Trong nam 2008, tren 20 trieu don vi bo mach din ter da duqc trian khai.

Ti Nhat Bin, dim tren so thanh c8ng tren he thteg DSRC 5.8 GHz vi truyan thong tren cac xe dtra tren ha tin hang ngooi, nhiau do an vi clic hoot Ong ITS hien

CHUONG 1. Tang quan ve he thong mong Vanet

dang tham gia de chimg minh %/a tang cuing phuang tier, cot sa ha ting va truyen thong xe vii xe duai sang hen an town ITS 2010 Oa NI* Bin. An town xe nang cao sang kien, trong giai down 4, dang giai quyet xe, truyen th8ng xe bang each tray c#p vao mOt met he thong da nhiem (CSMA) dim tren phin ma ring eta ARIB STD T-75. Cruise - ha trq sang kit!' he thong duang cao t6c duqc xay dung tren he thong 5.8 GHz DSRC cling nhu he thong hi trq lei xe an town (DSSS) cling sir dung cOng nghe hang ngooi truyen thong cho xe ben 11 throng. Cac hoot ding Smartway tap Ming vao cac djch vu ITS va mOt nen tang djch vu thong thuang duqc cung cip tren diu trang cat' cac mang hi& hien ca. Trong thing 6 am 2007, n6 di duqc deg b6 kenh 10 MHz trong cac kenh tin s6 700 MHz se duqc phan b6 cho truyen thong lien quan den an tan lien xe toi NI* Ban vim am 2012.

CO mOt s6 do an deg nghiep chinh phi 6 MI duqc thrc hien vi duqc (Lang tren bao. Hai trong s6 nhung do an de duqc m8 tit 6 duai day. Lin diu tien Vehicle Infrastructure Integration (VII) duqc di ten thanh IntelliDrive, gin day met y tuang Ian dit duqc ch(rng minh. Thir hai la do an ang dung truyen thong an town phuang tien do kien se duqc kit thic vao cu6i am 2009. Ca hai du an tren duqc sv tai trq ctla 130 giao thong Hoa KI vi mOt s6 nha san xuit 8 to va nhi cung cep. Ngoii ra, hai do an khitc xirng clang duqc a Op ngin (cid:9)

mOt chr an dang din ra he thong an tan duqc tich hqp tren phuang lien lcham phi cac vim de giao dien ngutri-may vi mOt s6 img dung an town, vii khuyen cao ce khi Wing chang cheo hoc miu thuin, duqc xiy ra ding thai (Doi hoc giao thong vin di Michigan). Dv an tha hai li Cooperative Intersection Collision Avoidance Systemproject gam co ba thanh phin (McHale). Dv an canh bao vi phom 6 Michigan, do an Stop Sign Assist 6 Minnesota vi do an Signalized Left Turn Assist 6 California. Kid xe duqc trang bj CICAS-V den gin mOt ngit tu, cac phuang tien nhon duqc tin hieu vi *Ong tin thai gian tit tin hieu den giao nhau (DSRC). MoSi chi& xe sau da se do down kha Wing ring n6 dang 6 NI tri c6 den do, vi neu thich hqp, cash bao trinh dieu Ichien (Maile). Dv an nay di duqc len Ice hooch dill nghiem vii trinh diet' khien don gian (Maile). 1.3.3. Kit qua can ak dr tin hifn tqi a. TYch kw co sd• hg ling (Vehicle Infrastructure Integration)

Trong ram 2005 130 giao thong van tai Hoa KI bit din di* nghiem met Meng mai. Da s6 cac m8i twang that nghiem nay duqc thtrc hien 6 cac yang ngooi 8 phia tay bic cia Detroit, MI. He thong bao gam 55 tram thiet bj trong yang 116.55km2 vi si dung 27 chi& xe.

C6 bay ung dung duqc phat Wen vi tha nghiem:

CIRIONG 1. Tong quan ve he thong mpg Vanet

—Bio hieu trong xe (In Vehicle Signage): RSE lien tic hien thj ra cac bin tin

thong bio ben trong phucmg lien giao thong;

— Thu thop de lieu them do: Phuung tier di lei cung cap (cid:9)

sir dft ligu ve vi tri cua hciltieu bang vi chia se yeti RSE, me sau da n6 duqc bien soon vi phin tich;

— Thanh toin dies to - thu phi;

—Thanh totin dien to - bai d8 xe;

—Thong tin ngutri di chuyen/bang bit dinh huong;

di nhu 100 msec) t r cac phuung tien bao gem ci tic dO xe vi vj tri;

—Thong tin dinh ki (Heartbeat): RSE thu thep thong bio tang this dinh kjr (vi

—Hien thj tin hieu giao thong: quing be tang thid den giao thong.

kilmtre kite& an tole

Tramphoenkitip, Nastier& tedsnyia

Zhu vw the

rung twin bee

oetwaistro blyiniii

(cid:9) thuilouthies

cgaintied4,einbang &heath co p1ia talc

Hinh 1.3 Vi du he tang thik nghiem tgi Michigan (2008)

MOt s6 kit qui quan tong dtrqc rut ra nhu sau:

— Ti le 18i gei tin la mot chic Wing mph me caa tom nhin thing. Khi elm nhin thing dtrqc duy tri, ti le 18i g6i tin yin 6 mac thip them chi 6 khoing each 100m. Khi tom nhin thing bj mit, ti le lai tang len nhanh chOng.

— IPv6 yen hail tot.

— Chi phi cho may thu GPS thip nhung dtrqc s* dung trong cac POC, !thong se

cung cap cho phan lueng mac dO chinh xic.

— Ma h6a goi tin tfr diu cuoi den diu cuSi thanh cong.

CHIrONG 1. T6ng quan ye h'e' &Ong mang Vanet

—Ung dung thong tin dinh Id lim viec tit cho phucmg tien trong khoing 100 m

cua RSE (lily thuc vio tim quan sat thing)

— He thing an ninh da duqc hien thi de 1km viec, nhung chua chic chin. Ngoii

To, kiem tra quy m6 chua duqc thuc hien.

—Quin 1S, tai nguyen elk mpg truyin thong cho cac img dung chgy deg thbi

phirc top hun du kien.

—Cii dot, ciu hinh va duy tri RSE philc top hon va kh6 khan hon du kiln.

Khi giai dogn nay mkt chuong trinh 7 khung kit thfic, BO ngo3i giao giao thong v#n tai Hoa KS/ di thay vi tri vi di ten the chuong trinh 7 khung (Row). Ten mai cita no la IntelliDrive. NO se nhin monh c8ng nghe khemg day trong cic dich vu ve i'mg dgng an Win. Trich din "The Future of VII" (Row):

Chuong trinh maxi trong tuong lai tip hung nghien ciru cic hoot dOng trong

nfring yang nhu sau:

—Cong nghe quit inh vi nhOn ding vi met s6 cac ceong nghe dem wing khac. Nghien ciru, trinh chin, vi danh gia cac cong nghe cac ling dung an town da kich hogt.

— Sr thiet Ittp cila cac nen thil nghiem de h6 trq cac dui nghiem vi cluing minh

cho veng stir dung chung vi rieng.

—Su phat Wen cult Iden trim vi lieu chuin di me, ra nen tang cho truyen thong

khong day di vi den phuang den.

—Nghien cint ye van de phi k9 thu#t nhu trich nhiem phip ly, tinh bio m#t

thong tin vi (mg chnig elk quy dinh.

—Nghien cuu tren cac lqi ich phu thuec t6i tinh di ding va m8i truemg.

Buck diu, du an Safe Trip-21 dua ra nam 2008 vi di thanh 16p cac trang web Connected Traveler lam tra kit n6i et California. Safe Trip-21 duqc thiet Ice de cai thien an town giao thong vi gikm iln tic bing cach xic dinh vi khai thic cong nghe hien co vi thich img cho cac nhu ciu giao thong v#n tai, vi g chimg minh ring nhing lien bO ding ke trong viec giai quyet yin de giao thong kheing co yen citu du to ca s6 hg ting lon. (SafeTrip-21 nam 2008).

b. ling dong trayin thong an tint

l'ing dung truyen thong an Willi xe (Vehicle Safety Communications- Applications) (VSC-A) la du an gita nam nhi sin =it 8 to (Daimler/Mercedes-Benz, Ford, GM, Honda vi Toyota) vi BO giao thong v#n tii Hoa trong ba nam. Day la du in truyen thong diu lien de theo dii an totin cho xe (2002-2004), vi tip trong vio

CHUtiNG 1. TOng quan ve h4 thong mong Vanet

cic phuung tien truyen th8ng va dinh vi Wang dpi v6i muc tieu to dieu kien cho cac (mg dung an Wan tuang thich (Ahmed Zaid).

Do in VSC da xac dinh tam kich ban caa cic vu tai non "bang xep hung top composite", doa ten th6ng ke cua chinh ph6 Hoa Kp ve tin s6 vu tai non, chi phi, va cic khoan 16 trong cac nam hoot dOng. Tren co s6 nay, VSC Qua ra bay Ong dung an town de giai quyet nhung tinh huing tai non. Nhing Ong dung (Maile):

M t di 'u lchi ma khong c6 phuang tien uu tien hoot dOng Dieu khi&n phuang tien duqc dung lai Cic phuang tien theo huOng ket not lcheng danh tin hieu Xe cO lai au, di ngtrqc chi&

Dieu khien xe giam toc dO

Phuang tien khong la tic nhan (di nguqc chieu) Cac phuang tien thay d6i lan du6ng clang mOt huOng LTAP/OD toi cac nut giao thong khong c6 den tin hieu. Bang 1.1 Ban do mkt VSC-A img dung an toan va kich ban cac via tai nap, dtryc quan

tam nal

(EEBL): canh — Den bao phanh Ichin cip (Emergency Electronic Brake Lights)

&to ye xe phanh dOt ngOt 6 phia tru6c.

— Canh bao dung dO phia tram (Forward Collision Warning) (FCW): earth bao

xe phia sau sip va chom vao xe phia tru6c.

— Cinh bao diem mu (Blind Spot Warning) (BSW)/Canh bao chuyen lan (Lane Change Warning) (LCW): canh bao cho xe biet c6 xe lchac dang di clang huOng mu6n thay d6i lan duting ma nim trong diem mu. Sau d6 khuyen cao cho dt ca cac xe nao dang n&m trong diem mu.

CHUONG 1. Tang quan ve hg thing mpg Vanet

(IMA): canh bao — H8 trq di chuyin qua giao 10 (Intersection Movement Assist)

khi d6 khong phiti la thtii diem an town de vao xa 10.

—Canh btio khong vuqt qua (Do Not Pass Warning) (DNPW): canh bit° khi

chiec xe sip va cham va yeu ciu they d6i lan dutmg neu c8 the.

— Ciuth bao met kiem sofit (Control Loss Warning) (CLW): Ttr tito ra canh bao khi xe

met kiem sat. Cac xe Ichic se duqc doh bao phu thuOc vao moi de Oa.

Trong filth vrc truyin thong, tip trong vao (Caminiti 2009):

— Thong di0p thanh

—Nang luqng tit* nghi0m.

— Th8ng di0p ph6 Wen.

— Hoot Ong da kenh.

—Ph6i hqp va xac nhin tieu chuin.

Nhi0m vu thong diep thanh phin di xtic djnh mOt thong di0p bao an total car ban trq tit ca cac ling dung an town (Caminiti). CEng vi0c nay anh hutmg manh me gin nhu hoan thank cac cuOc dam phan ve nh6m lam vi0c SAE J2735. Tieu chuin/ de nghj cuei cling duqc dua ra vao cuei nem 2009.

CEng viec dul nghiem nang luqng kham phi Ong suit cao (> 20dBm) lam tang hi0u suit ling dung an tan, vi nang luqng thip (<20 dBm) chi ra dieu then tic nghen. So sanh tS7 18i g6i (PER) xung quanh mOt "ngit to khip kin" 'thong c6 tim nhin thing, chr an di the hiOn duqc pham vi truyin thong hiOn tai hon giam 18i ding ke stI dung truyen tai dies nang 33 dBm (tren danh nghia 20 dBm) (Caminiti). Dieu nay cung cep mOt dating di thu vi cho khan' phi, dic bi0t IA trong nhttng thach thirc dot ra boi cac thong tin truyen th8ng tim nhin thing duqc bao cao trong biva bao cao VIIC (Kandarpa).

Cac ban tin ph6 tan se dieu tra vi0c sal dung c8ng suit, hic d), va dieu khien Ichfic de giam thieu sq tic nghen mpg va cal thien viec chuyen ban tin chi thien (Caminiti). Kit qua cuei cung di khong duqc tiet 10 tai thtri diem viet bai nay. Tuy nhien, kit qui c6 ngay sau khi holm thanh du an VSC-A tong thing 11 nam 2009. VSC-A da tich cuc tham gia cac tieu chuin Ichac nhau DSRC, bao gtan IEEE 802.11p, IEEE 1609, va SAE J2735 (Caminiti).

Ngotli ra, VSC-A c6 mOt nhiim vu tip trong vao sq an town cita ban tin eta xe vai xe. Tranh phtua cling bit° mit chuyen dung. Dq an la &nit gia thuit than dubng cong elliptic chid 14 se (ECDSA) (Accredited Standards Committee), Ain d?ng ten thit tang the theo luttng thoi gian (Timed Efficient Stream Loss-Tolerant Authentication) (TESLA) (Perrig), va mOt phien ban situ di.

CHUONG 1. TOng quan ve h'0 thin mpg Vanet

1.4. 'CET LU*14

Trong chuang nay, tea di trinh bay lchai quit ljch sir hinh thAnh va phat trien mia

VANET, nhung nguyen tic co ban vA thach thirc ctia mpg VANET.

1.1-11) UM,' 2. t ruyen tnong tin trong mong v anet

CHUONG 2. TRUYEN THONG TIN THONG VANET

2.1. GIOI THIEU

Cac img dung an total VANET yeu ciu thong tin chi tir nhung vimg giai hon dja 1ST 6 gin xe day kh8ng phai la trueng hqp cho nhieu (mg dung ththin tien va ring dyng cho lai xe. Vi du, he thing chi &Ong c6 the se dung thong tin trong mOt veng rung lan hcrn trong cac tinh huing giao thong hien toi. MOt vi d i khic, he thing do xe eng dung VANET: nhttng thong tin phan loci ve tinh hlnh a xe trong toitn thanh phi. Thong tin duqc thu th#p lien kit va chia se trong mOt yang rung Ion nhu mong luoi dueng cao tic hoc la mong lueri throng bei thanh phi. Th8ng tin c6 the la m#t dO km lugng va theri gian di chuyen, cac nai a xe man phi va cac thong tin khac cif, the nhitng ngueri tham gia mpg khac theo dOi, va duqc thu th#p, phan logi beri cac thiet bj lien ket trong mpg Ad-Hoc tic dO cao.

Phan loci thong tin trong VANET la mOt nhiem vu thach thec len. N6 chi ce the lam duqc khi xem xet tAt ci cac tinh chit va glen hon cua cac thanh phin tong he thing mong VANET. Dec biet c6 hai rang buOc lien quan la su ket n6i va sec chfra. Qua trinh tham gia mpg bj gieri hon din den mOt mmig ter len thea.Ngay ca khi dot duqc tSI le tham Mt) cao, thi ket nii mong vin thueng xuyen bj hon che, vi du trong cac khoang then gian luu luqng thfp. Trong cac hieu (mg khac tic de, ket n6i anh huong truc tiep den tic dO truyen tai thong tin qua VANET va do da truc lief) inh huong len su c#p nhop, su chia se thong tin.

KM riling curt VANET con bj Nut chi bOi cac ket nii kh8ng day.Dung luqng mong se khong du de cung cip thong tin chi tiet vi lien tic cep nh#p mai thay d6i nh6 ye tinh hinh thrc the curt cac thinh vien trong mong.Dieu nay ding duqc nhin monh ben cac ket qua di duqc biet ten cac giOi hon cong mat c6a cac mpg !thong day da buerc. Do khi Wing cua mong bj hon the doi hbi phai ce ca the de gam s6 ltnyng thong tin truyen qua mpg, bing cach teng hqp s6 lieu ci nhan.

Khi Wing hon the cua VANET chri yen la do nhung hon chi cua cac kenh kheing day. Bing truc giac to cung thiy r8 ring ring dung luqng cua mong se khong dii de cung cip thong tin chi tiet vi cip nh#t lien tic tren tit a cac th%rc the dja ly quy m8 nhe cho tat ci cac thinh vien cua mong. KM nang the doi hoi phai c6 ca chi de giam si luqng thong tin can chuyen qua mong, bang cach tong hqp, tep hqp cac muc de lieu ca !than.

Bin thach thec chinh cua mong VANET:

de hinh thanh mOt ca s6 delieu cho cac ting dung.

— Lam the nio de c6 duqc thong tin, cu the la lam the nio de quan sit khu Arc

Ltiu UNIT L. iruyen tnong itn trong mpg v anet

—Lam the nao de vfm chuyin thong tin, tirc la cho ring thong tin co sin toi mOt s6 diem trong mpg VANET vi lam the nao de cung dip cho cac ben quan tam trong cac phin khac cua mong.

—Lam the nao de tom tit cac phep do cac thong s6 twang ttr hoc rat twang tv duqc thqc hien boi ngutri tham gia mpg VANET Ichac biet, de earn sir du thOa khi no kh8ng the quan sat het tit ca cac sir kien.

— Lam the nao de thong tin t6ng hqp 16n horn cac thirc the (ha 1St, xem xet thuc to ring Icha nang han the cfia mong 'thong cho phep mOt cai nhit' chi tiet ve town bO khu vqc rOng lon.

MOt phac thao ca ban he thong ph6 hien duqc the hien tong hinh 2.1. ThOng tin duqc thu thOp tir cac ngu6n nOi b0 va ben ngorli (dm la, ter cac cam bien trong xe va c6 WI rang con ter ca se; ha tang ben duimg) vi duqc luu trif trong mOt ca so du lieu di biet. NOi dung cita ca so dit lieu da Wet nay duqc dAng cho cac (mg dung, va chia se, trao d6i yen xe 8 to Ida& bang pinning tier truyen thong khong day. SO hopg dit lieu trao d6i gitta cac xe duqc gialm bang citch ap dung 1E9 thu#t de tong ket va t#p hqp cac drr lieu trong ca sO drr lieu da biet.

Trong phin nay se trinh bay bOn vim de dif neu 6 tren. Phin tiep theo se xem xet cac yin de va de xuit, kieu dit lieu cuc b0, sau d6 xem xet cac vin de giao thirc truyen tai dit lieu toi muc 2.3. Sau de muc 2.4 va 2.5 bleu dien dit lieu va cac lchfa canh chuyin d6i, t6ng hqp, t#p hqp cac thong tin thu thftp duqc.

Ifinh 2.1 Ong citing phd ban dira tren VANET

2.2. DO LikiNG VJ TRf HIgN HANH

Tnroc khi mOt Ong dung ph6 bien dva ten VANET co the bit du truyen thong tin, xir ljr da lieu, xac djnh vj to khu vtrc (t(rc la, do Wong cent mOt ho#c nhieu tham s6 b6) can phai duqc thqc hien. Trong cite giao thirc ph6 bien dit lieu vi cac Ong dung dva tren cac cutoc that:, lu#n thuong dua ra cac thong s6 gia djnh ma bo qua cac

18

vivo Z. iruyen tnong fin trong mang v anet

so lieu thuc 4 6 tren. Tuy nhien, kung don gian de co the 'cac djnh vj tri cic bO, va sq lira chqn cac thong se duqc truyen trong mpg can duqc xem xet can th#n. NO ply; thuOc rat nhieu vito muc dich cu the, muc dich ctla (mg dung, va no lien he met thiet vai cac thong s6 thiet ke !chic lien quan den ca cho, giao th(rc top hqp vv.

2.2.1. Cam ban trong xe

Cac cam bien tich hqp trong xe se cung cap thong tin. Nhieu bi) cam bien di cO sin va duqc sir dung cho cac he thong dien ter 'chic trong xe. NO cung cap thong tin tren cac thong se mei trutmg nhu nhiet dO, cubing dO inh sang, vj tri (GPS), tec hoc dieu kien met du mg (bang, ntroc, vv). Cac thiet bj tinh vi vi xir ly logic Ong ce. the cung clip thong tin nhu lchoing cach xe truck vi cac xe lien tiep (vi du, cite phep do khoing cach radar), tam nhin, hoc cac bien bio giao thong vi den giao thong (thong qua hinh anh camera vi nhtm clang hinh anh Icy thu#t).

Dqc ding to met ce the cung cap thong tin quan trqng va cho phep rut ra kit lu#n ye tinh hinh giao thong hien tai. Di cii thin tinh chinh xic vi chi tiet cilia cac thong tin, co the ket hqp thong tin tir nhieu nguan, qua trinh thutmg duqc gqi 11 cam bien nhiet hitch. Ngay nay, nhieu cam bien xe da duqc kit noi thanh Controller -Area Network (CAN), theo quy djnh cua t6 chirc tieu chuan quik 4 (2003, 2004), vi viec dqc c6 the duqc chart Me thong qua kenh nay. Kit he thong tich hqp vi kit hqp der lieu dr cac nguan khic nhau de dat duqc cii nhin sau sac ye tinh tang throng hien tai. 2.2.2. Clic he thong djnh vi nine la met ngmin thong tin

Phan lOn cic (mg dung tien lqi VANET cho din nay la it nhieu lien quan den mOt thong djnh vi. Vi du la he thong phan phai thong tin cho viec tim kiem cic my& du6ng voi than gian ngan Ara tren tinh hinh giao thOng hien tai va mOt he thOng cho viec tim kiem nai da xe mien phi. TO gOc nhin cOa he thOng thong tin trong VANET, thirc ti la ngiy rang nhieu phuang lien duqc trong bj he thong djnh vj, mOt h¢ than djnh vj kh8ng chi co thong tin chinh xic ve vj tri vi tOc di) hien tai, ma con dua ra thong tin ve huang xe du djnh den. He thong dinh vi c6 the cung cap thong tin vi tri tren mOt mirc dO trUu tuqng cao han: thay vi tqa dO dja khi *it xe chuyin huong hg thong cho biet ID duOng, huang lii xe, hoc them chi lan throng. He thOng phin phai thong tin giao thong nhu SOTIS mkt Wischhof. H thong quan sat Wu hrqng boi Nadeem hoc CASCADE ciia Ibrahim va Weigle thuong sir dung vj tri xe va tac de, xe la nguyen thay ca ban (sau de duqc trao dal trong hinh thin nhieu han hoc it km tong hqp). Neu muc dich cila (mg dung la t6i uu hda viec lira chon tuyen dutrng dim tren tinh hinh giao thong hien tai milt he thong duOng giao thong, mOt cach tap con khic la sir dung thin gian di chuyin doe theo down du6ng nhu cic quan sit cuc bO, voi

uivu 2. i ruyen tnong tin trong mang v anet

sv trq giep curt he thong djnh vj thi rat dan gian de c6 duqc cac thong se do tai dja

phuang.

2.3. TRUYEN TAI THONG TIN

Sau khi nh#n duqc thong tin to cac cam hien khic nhau, ne se tao ra met cai nhin t6ng quan ve tinh hinh quanh khu vvc de. Tuy nhien, Icheng chi chi& xe c6 duqc thong tin nay mai can de lieu nay, ma con cac phuong den khic ding can thong tin nay de c6 the thich img vai nheng hanh vi cite ne. Vi the, vies truyen thong tin cho nhitng chi& xe quan tam den thong tin de 11 rat quan tong. Trong phim dub i se giii quyet van de ve truyin thong tin vai nheng phuang phap Ichic nhau. De tranh nhi'mg quan niem sai lam thi phan nay se xac djnh cac dieu kien phat song, trap lit, va bao hieu nhu sau.

Quang hi thong tin la cach duy nhat truyin met ban tin den tat ca cac nut trong phtun vi cua nut giri. NO thueng duqc sir ding ham nguyen they de chung Iran lit, 6 day phuang phap su ding la phan phei mOt ban tin tren met pham vi Ong cua mpg khong day da buac. Cac nut da nh#n duqc thong tin se quimg hi lei cac ban tin va do de se cung cap cho tat ca cac nut trong mpg hoc mOt t#p hqp con cira chung, vi di cac nut trong met khu Arc dja ly giai hen. Bao hieu them do la viec truyen tai thong tin djnh Icjr cho tit ca cac nut xung quanh. Nh#n IA& bao hieu them do la viec quing ba djnh kjr. Chi met gei duqc truyen boi bito hieu than' de duqc goi la mOt m6c bao.

a. Ctic giao fink truyin Mi titling tin

Phuang phap thin lit va truyin theo vi M dja ly cling duqc biet den la thuong xuyen duqc sir ding trong MANET, mOt trong nheng cach de truyen thong tin rat nhanh la sir ding trim lit. Thv hien dan gifin la khi mo3i nut When duqc thong tin chi dan gian la se quang bi lai ne. De trainh tang 'Op ban tin v8 hen, m8i nit se phat goi tin met ltm.Ngoai ra, con dem thin gian sting (TEL) c6 the duqc sir dung de giOi khu Arc, nth ban tin duqc phan phei. Phuang phap tiep can nay se truyen mOt luqng Ian cac gei de lieu du thea, co Ida Wing din den tic nghen nghiem tang. Dieu nay duqc goi la “vin de bao quang ba"

Trong mpg phuang tien, phuang phap train lvt thuong duqc sir citing de phe hien cac thong tin giao thong cho xe Ichic. The tic chung la mOt chi& xe - nguan phat hien mOt sv kien hoc tinh hueng can thong bao cho cac xe khac. Tir nguen nhu v$y thong tin bit dau thin ng.p. Trong phan clued day giii quyet yeti nheng each tiep c(in Ichac nhau nhim mic dich han the sto luqng cac gei dtk lieu gi6ng nhau trong he thong. 1r tdmg chung ciut tat ca cite phuang phap nay anh hutmg den hanh vi chuyin dip cea cac phuang tien, bang cach thich nghi vii thei gian khi chuyin tiep cac ban tin ho#c bang cacti dua ra cac quy dinh ye viec chi& xe c6 the chuyin tiep tit ca cac bin tin.

Ltiu UNU 2. i ruyen tnong tin trong Inking v anet

De nh#n ra phtrang phap tran lut trong cac lin quang bat tuy thuec vao m#t dO giao thong. Khi giao thong day d#c Ichong phai xe nit° ding can truyen lai thong diep. Ngoai ra, quang bit thong tin ding co the dirge thich nghi von khoang catch giai han. Trong vimg lan Om gin han thi ban tin duqc 10p di 1#p lai obi rit nhieu nut. Bing catch ling nghe, 157 Wong nhit la tit ca hoc gin nhu tit ca cac nit gin v6i he thing quang IA. 0 duqc thong bio. Vai khoang catch ngly cang tang thi tin s6 ctla quimg ba earn. Hoc ce the sir dung tran lut b xung quanh nguOn mkt ban tin. Dieu nay cho phep cac xe b gin han ci the truyen thong tin nhanh nhit ma kh8ng phai bin lut ban tin nao vao khu vrc rung han. Trong Dombush vat Joshi nghien ciru dva vao ki thu#t "phat tan tin din" (rumor spreading), "buen chuyen" (gossip), hoc "clich benh" (epidmice). day, met nut nIgin thong tin thi se luu lai ban tin hien thbi vat diy ne cho cac nit khac.Tuy nhien, nheng Icy thu#1 nay yen sir dung mOt catch dip c4 ► giting nhu trim Iv. De hp chk s6 knyng tin nhin duqc truyen, cac nut sat quyet djnh chi phi bien cgc thong tin mai nhit. Ngoai ra, co the co cac phucmg phap ket hap hai tiring nay. De dap wing cac tieu chuin thich fin met de tY le chi c6 mOt vii xe se tiep tvc quimg bit cac thong tin mai duqc tao ra. KM ban tin chuyen tiep lan len din den ttm si quang ba giam. De tranh nheng vin de bao quang bit ci the km chi nhitng ban tin ding thtri.

MOt de an khac de han the tran lit ctla dieing tin IA de cho ben nh#n quyet djnh ci nen quang ba lai cac ban tin b tit ca cac nut. Vi du trong Chisalita vat Shahmehri xem xet met catch tiep den nhu voy, mOc du chtl you nhin vao cac img dung an tan. Gia djnh ring khi ghat hien tinh huing nguy hiem thi met ban tin canh bao se ducrc pang ba. Ngtrqc lai chi don gian la quang ba lui ban tin nay, met be nh#n cac de lieu nay phan tich cho du no of) quan tam den citnh bao hay khong. DO la trubng hap neu ben nhfm la lai xe tren cling mOt con &ding vat trong cling mOt huang von phuang tien nguin mkt ban tin. Gilt djnh ring neu chinh ni quan tam den cac du lieu vat sau di cac xe o to khac trong vung lan c#n ciut no cling c6 the huang lqi te ban tin. Thong tin se duqc quang ba met lin nita. Catch tiep con nay ci the duqc thea huemg cac thong tin b6 sung trong ban tin de de ding quyet djnh ma tren db cac nut duqc quan tam trong cac dl lieu. Trong Ducourthial trinh bay mOt catch tiep On them dja chi dja ly vao ban tin de tao dieu kien thu#n lqi cho cac nit nh#n ci the phan tich. Bing catch danh gib tinh tang sau di ci the quyet djnh xem ci nen chuyen tiep bitn tin. Tong tlr nhu de an Briesemeister de xuit ce tinh den khoang catch den met nut chuyen flip tnroc di. Cang xa met nut thi kha nang quang ba lai cac ban tin nIgin duqc ngay can cao.Citc nut ling nghe truyen tai gift hai nut khong din quitng bit lei. Sau khi truyen tai met yeu ciu quimg ba toi dt ca cac nut trong pham vi truyen tai gtri met cilia& gay nhieu duqc gqi la "bung no den" von thoi gian phu thuec vao khoang catch gitta nut gen vat cac nut nhan. Nut xa nhit se girl chum gOi tin dal nhit vat chi ra bing cbch girl met

Ltiu ONIJ 2. 1 ruyen thong Lm trong mpg v anet

"quang bi ro" c6 nglif la no muen nh#n duqc gii quing bi. De earn cic chi phi ctla met qui trinh nhu vh, Zhao sir dung met cacti tiep can dlra tren djnh tuyen vi tri dia 15r. day, nguai nh#n quyet dinh can cir vao met bang cic ving lin c#n chart cac nut ncri ma ban tin se duqc chuyen tiep. Do viec sir dung "htrang din" trinh cluing bi, cic nut trong pham vi eua sing ling nghe ban tin.

Trong nghien ciru ban du, Kosch de )(nit di me rung giao thirc djnh tuyen AODV cia Perkins vi Royer Uri met s6 chirc Hang truyen theo vi tri dja ljf. Ban tin c6 chilli thong tin, vi du quang bi thong tin ye dieu kien dubng xi hien tai trong met khu vtrc nhit djnh. Met phuang phip tiep can khic la thong tin duqc phi bien theo met tSr le quan tam cue b6. Neu met nut nao nh#n duqc de lieu nay cuing se chuyen tiep ban tin. M#c di phuang phip nay hip din bbd ci the sir dung cic giao thirc hien co nhung no lai ci han the la no co the duqc nhtm rung trong cac mpg Ian, nai rit nhieu nut la nguin ciat thong tin. De del phi vii cic miu luon di Ong khic biet cia mang phuang hen trong Sormani them met ca chi luu trEt vi chuyen tiep den cic nut tiep nh4n VI vbr, cac nut ding gip vao viec chuyen thong tin bing dutrng truyen kung day cling nhu bing each rieng curt no.

Cin luu Sr ring trong khi truyen ban tin cic not quyet djnh c6 chuyin hip thong tin dua tren lqi ich rieng ma khong quan tam den cac thong tin phi bien duqc cai thien. Dieu nay di b#t ra duqc met vin de nghiem tong ye bleu suit.

Williams va Camp so simh cic each tiep c#n tan lut khic nhau theo hieu suit va chi phi. M#c dU nghien ciru nay duqc thuc hien. trong bii canh chung dui mpg MANET, nhung kit qui c6 the rit httu ich cho VANET. Ket qui vi ket lutut nhin manh ring cic phuang phip tiep cOn trim lut cho thiy hien suit tic nghen rit thip. Trong mOt kjch ban phi) Wen thong tin phuang tien, thong tin tan lut ci the duqc bit diu Uri nhieu nut ding thai c6 the kit qui cis n6 lcheng hit nhu da trinh bay.

b. Yeti cliu fro lid

Truyen thong tin trong bei cinh khong ci giOi hart ye xe duce trang bj ling dung de chi phuang phip chit dung tiep can trin lut. Neu nhieu ngueri sir dung gin nhung thong tin 'thong cin thiet thl co the la gii tri tic dung ter lai hoc do yeu can cult thuet twin. Trong trulyng hqp nay, met chi& xe se yeu ciu met each r8 ring de c6 thong tin cu the bang each truyen met bin tin yeu ciu. Diem den cuei cling cia gii tin nay c6 the duqc biet den, vi du neu ngteri ding yeu eau gii xing hien tai ciut cic he thing Ling flip theo hoc yeu eau so bai a xe cho met chi xe mien phi. Khi Hang chuyin thong diep nay ci the duqc thuc hien theo nhemg each khic nhau.

Cac ban tin yeu cau chuyen tiep trong truyen thong don hurong bang cach xay dung met tuyen r8 ring, hoc sir dung vi tri dua tren phuong phip djnh tuyen. Cac ban tin

L.1-11JUINU Z. i ruyen tnong un trong mpg v anet

frit lbi sau de a duqc tth lei tuang tu nhu yeu cau. Thay vi yeu cau thong tin true tiep t#i ngu6n, xe et-mg c6 the yeu cau cac xe khac di qua cung cap thong tin ma n6 biet ve dieu db. Thai gian chi dqi t#i den do c6 the keo dili du de dien de thong tin vio co so drr lieu dA biet cua dja phuang bang each truy van chc xe lchic. Trong hau het cac nghien cuu khac yeu cau duqc thuc hien mOt each gian tiep bang cach cong b6 cac muc ca sa dit lieu dja phuang. MOt nut nhin duqc ban tin nay c6 the phan tich neu n6 biet thong tin de la men hockhang r6 ngtrbi yeu cau. dim k5 thu#t khic nhau duqc de xuat de thuc hien nhung ca the yeu cau. Trong hinh 2 2 ma to mOt qua trinh c#p nh$t dOc lip. Ngoiti ra thu tic nay ding c6 the dua ra nhang kien th(rc cue b.) khi cac xe khac c6 yeu cau r6 rang ve mOt nui cu the. Ngtrqc lgi vai mOt ca the yeu cau tit 101 don huOng, mOt bulk gluing bi djnh lcSr yeu eau k9 thu#t clua tren mOt cau true clit lieu tuang tu nhu mOt trong nhCmg nghien cuv dit de c#p a tren. Han nits, bang ciich sir dun kg thu#t de nein ch#n firth tiling qua tai ciut mang, de nghj dieu chinh tan s6 elk than yeu cau tny thuOc vao mOt dO giao thong.

Cosbddfludfbik A 42,7

Cosadi/flu8ibik A42,7 B62,1

C 25,9

0) /

Co tdr d6 flu di bik A 42,7 1382,1

Co Vs cift lila a Mk A 42,7 B 62,1 C 25,9

(4)

Hinh 2.2 Trao egi thong tin ngdm.

(1) Hai chiec xe yeti hieu biet ca ban khac nhau.

°NU 2. iruyen tnong tin trong mong v anet

(2) Xe ben trai truyen kien thirc rieng cfia minh. Bing cach so sanh thong btio nay, chi& xe ben phai c6 the phan biet cac muc ma n6 dang so hthi va truyen cac thong tin an thiet cho xe ben trai.

(3) Truyen tai cac muc thieu. (4) Xe ben trai da cop nh#t lden thirc cc; ban. De khic phuc cac phan veng VANET c6 the se dung cac phuong phap djnh tuyen cho phep tre tong the. Kh8ng yeu cAu gel de lieu phai truyen theo met tuyin duong dinh them n6 c6 the truyen theo v1 tri dia ljr den met khu Arc nhit dish va c6 the duqc truyen di ngAm bing su di chuyin dui xe. Bing cach nay, cac phan veng Ichac nhau c6 the duqc mb reng. Viec chuyin cac ban tin tra lei theo cac quy tic tuang

tu nhu cac gel tin yeu ciu.

Qua trinh yeu ciu/tra lbn phai 461 met voi vin de ma reng. VANET c6 kha ming sir dung bit cir ngu6n nito hOi to ye vi kick thuOc cua mpg se tang len den ve cling. VI 4y, nhung phuong phap nay phai quan tam d#c biet a hp the viec trao 461 yeu ciu /tra Ibi cho cac phuang tien gin voi nhau hoc sir dtmg met s6 cach khac de him chi tai tren mgng.

a Mom (Clustering)

Trong met s6 trutmg hqp ban tin trim lut vao tom be mpg la khong thich hqp va se gay ra mirc dO tic nghen cao. D6ng thoi yeu ciu/tra lbi c6 the kung thich hqp, vi du thong tin se tre len can thiet neu c6 rit nhieu nut cling yeu au met Km. Do de c6 cach Ichic de thay the cac gel de lieu trim lut, kung c6 ciu tnic cfia met s6 loci phan ph6i phan cip bang cach sir dung cum.

Agarwal va Littletrinh bay mOt giao thirc Ian truyen c6 huong Directional Propagation Protocol (DPP). Phucmg phap nay xem xet ph6 bien cac thong tin tren cling &rang cao t6c. Khi giao thong day d#c, met s6 nut trong khu vuc hinh thanh mOt nhom. Trong nham nay thong diep duqc chia se voi tit ca cac net cfia nham nay.

De truyen ban tin theo met huong, cum ch6ng click) duqc sir dung de truyen tai bin tin. Cac cum theo huOng d61 10p duqc coi la truyen ban tin. DPP thong qua the toc ctia mpg tre tong the Delay Tolerant Network (DTN). Neu Itheng c6 nhom chimg cheo viec truyen cac ban tin duqc thuc hien don gian bang cach se dung di chuyen cua xe.

MOt cach tiep (cid:9)

ph6 bien cling se dung cac thu#t phan nhom duqc de xuit bei Chang. Neu met chi& xe can thong tin, ne With thanh met nhom. Dieu nay bit diu qua trinh phan nhom. De truyen de lieu vao cac nhom khac chuyen dip cac phucmg tien lc& not hai nhom. Trong giai doon diu tien, thong tin trong met nhom duqc thu th#p trong Time Division Multiple Access (TDMA). Sau giai don tau tier, tat ca cac

utiu UNtJ L. 1 ruyen tnong tin trong mang v anet

nhem dimg diu se cio tit ca thong tin ve cac xe trong nhOm ciut n6. Trong giai down thin hai thong tin sau d6 duqc girl ter lai cho nguiri diu tien, tiro la, cac nut yeu ciu.

MOt each dip c#n dua ten nhOm duqc trinh bay bid Chennikara Varghese.Xe trong mOt khu Arc 'the to tao thank met nhem. Do vine ran On gin gui, ne c6 the true tiep giao tiep yid cac xe. Tuy nhien, thong tin lien lac giea cac xe khk hok lit gifts cac nhem c6 the duqc thuc hien bang cac phucmg tien chuyen tiep la mOt phin cua nhieu nhem. Ta cfmg c6 the se dung phuang phap phan nh6m cac bai (18 xe tmh de ph6 bier trinh tang mkt bai xe.

Leontiadis va Mascolo trinh bay phuang phip flap cOn dua tren me hinh di duqc xuit ban /clang ky. Nhting bim tin duqc ph6 bien va duqc gift trong mOt khu vuc XaC djnh truoc. Neu mOt nut bit ld quan tam den tin nhin ce the Ming ky vao su !den nay tai dja phucmg. Neu met ban tin duqc nhOn bOi nut ma ne ce the a clang kiem tra xem dieu nay phi hqp yin ding Icjf ciut minh hay khong. Thong tin duqc nhan d8i va nhCmg bim sao nay duqc truyin den mOt s6 nut trong khu vtrc. Neu met nut rid kit& thong tin khu Arc nay sau de duqc chuyen den mOt net di chuyen vao khu vuc hose vin con trong khu vuc. Cac tac gia cho thiy trong nghien cim cua ho rang s6 Wong ban sao c6 the duqc tu dOng dieu chinh va not chung thip han so yid s6 luqng thus bao. Sr khfic biet chinh cita phucmg phap nay so yid cac phuang phap ten la thong tin chin phai i lai trong mOt s6 khu Arc.

Cach dip cOn duqc de xuit boi Shinkawa cimg chung mOt y tuemg. Phuong tien di lai c6 thong tin ye khu vuc hien tai dot no. Neu n6 r0i kh6i khu vuc nay thi thong tin duqc b6 di. Nhung de khong bj mit thong tin nay ten town khu Arc, dSe biet la neu mOt de da cac nit la thip, cac the giti de nghi su dyng deng chi' la "message ferries" se khong quimg bit bit 14 thong tin Wien duqc.

d Moe bdo (Beaconing)

Trong nhieu img dung VANET, de lieu thay dii theo thiri gian duqc mOi nut ding b6 djnh k9 theo hInh thirc met m6c. Bing each nay, tong tai mpg duqc gioi han den met mire de c6 djnh duqc xac djnh bid mot dO ctla cite nut va tin s6 m6c bao.

1Chi nhan duqc quang bit met btok, cac nut kh8ng phim img lai bang each truyin din mid trip tiep. Thay vim do ne tich hqp nOi dung ban tin vao ca sa de lieu di Wit ctia no. Vii cac canh bao tiep theo d6 n6 se gei dieing tin nay, hoOc met phin biet sau d6 c6 the duqc phan ph6i dep.

De toi da h6a vise ph6 bien thong tin yid cac hart the la xe chi ce mOt vii trang thiet bj va trong gay tic nghen trong mpg de thich nghi vii cac tSrle cita cac canh bao. Vol khoang each ngity cling tang va toy thuec vao v#n t6c trong binh mkt xe doc theo met con duimg tin s6 ciut cac canh bito duqc truyen di la thich nghi. Tuang tr

(Atli UNIT 2. i ruyen mong tin trong mpg v anet

nhu vOy Fujiki ding xuAt hien mOt ca the thich ling vol tS le canh bao dinh lcSr trong khi db Wischhof khuyen nen dung thanh cac tai khoin cho du co nhang quan diem 'chic nhau ve tinh hinh giao thong a phat sinh tfr biut tin nh#n duqc. Ngoai ra, Wu phan tich mei trubng cita mOt chi& xe. Neu 0 mOt chi& xe mai Ian cdri xuat hien, mgt m6c duqc girl de c#p nh#t vao ca s6 dit lieu di biet dui nb.

Saito sir dung mOt cach tiep (cid:9)

TDMA nai mOt giay duqc chia than!) mu& khe.Khe cam duqc sir dung phu thuOc vao t6c a hien ttii dia mOt nut.Y tuOng la nett cb ach tic giao thong Ric dO hiOn toi a bj giam va mOt canh bio duqc

Torrent-Moreno trinh bay mOt cach tiep On de idem soat tai trcing kenh duqc sir dung bbi cac canh bao an town va cung cap truyen den thong tin dang tin c#y hon cho ngubi nh#n \di ngubi girl. Thay vi thay doi tin s6 cua cac canh bao nhu trong cac nghien cuu d8 de Op 6 tren chimg de xuAt dieu chinh khit nang truyen tai cita cac canh bao. Muc dich lade giiun thieu nguy ca va chum gbi tin thong qua im tat va do de lam tang kha Wing nh n duqc citc canh bao.

2.3.1. Cdi thin vic kit not mgng

Luu ter va chuyen tiep VANET kh8ng chi la mang thuimg xuyen thay dOi, ma cbn la mOt mpg phan yang cao, ket n6i lien tuc 0 the kitting duqc gia dinh trong mOt thiet ke giao thirc. De cho phep ph6 bien thong tin Lim xa voqt ra ngoai, plain mO Ong dia mOt plan yang mpg duy nhat, khai niem tilt cac mang tre tong the cb the duqc ap dung. Dec biet, phuang phip tiep can kho luu trCt va chuyen tiep de vin chuyen thong tin la mOt nguyen tic xfty dung thong thuing ciia cac giao thirc pho bien VANET. kh8ng thong bao ngay lop Trong mOt kho km trO va chuyen tiep cac nut cach tiep ttic ve phia truck, nhung mang cac thong tin cung vai nhang chuyen dOng Cult n6. Khi nhtIng ca hOi xuAt hien, vi du, bang each dap img cac xe khac, thong tin tiep tuc duqc truyen de chuyen tiep. Trong trubng hop don gian, nb lay Ian rn6c bao khip nai.

Khi nbi den viec thu hop khoang cach mpg gifts cac nhbm xe tren cling mOt con duing, quan sat thay ring viec sir dung cac xe dang di tai mang lai hieu xuAt cao hen. Dec biet la khi thong tin ye dieu kien giao thong, throng giao thong duqc trao doi, nb la quan tong de giao tiep clit lieu cho xe, lai xe 6 xa so voi khu vuc nai ma cac quan sat duqc thuc Men. Thong tin ye tinh hinh giao thong nhu v#y tit cac nguOn tao ra thong tin chuyen Ong cung mOt huang la kheong huu ich. Tuy nhien, sir dung giao thong dang tai a chuyen tiep cac thong tin rat cb the cai thien hieu suit cia he thing.

Dun vj ben throng Hai cau hoi duqc at ra trong qua trinh truyen thong tin: tSr le tie= nhOp ttoi thieu thiet la gi, va cac yeu cau khic can phai duqc dap img a phO bien (earth bag)) ban tin nhanh hen ye su v#n Ong thuin tuy cua xe? T#p tning chinh 6 day la lieu nb cb the

CHUUNIal., truyen wrong tm trong mpg vanet

truyen dtt lieu mOt each nhanh cheng den cac Wag xa xed voi chi c6 mOt vii xe duqc tang bj.

Theo nghien chi ctia Yang vi Recker kit luen ring cin ce it nhit 120% s6 xe phii duqc trang bj deg agile VANET. Tuy nhien kit qui phu thuOc ding ke vio pliant vi thong tin lien lac. Nei Chung, khi sic djnh gibi ban ve tj► them nli(tp can thiet ngin nhu kh8ng the vi met dO giao thong they d6i rat nhieu Wy thuOc yap con dubng cu the, thbi gian tong ngiy vi vi vey, tt le them nh#p dy dd trong cao diem 6 mOt trong tam thanh ph8 c6 the hoin toes chua dy de can thbi gian ban dem ho#c trong mOt khu vuc nong den. Do de din phai sic djnh met dO thin bj they vi milt dO cua cic xe duqc trang bi dy du VANET tren throng.

Dec 1(tp voi tt le than' nh#p ho#c met dO thief bj cu the, Yang vi Rettker quan sit . ditc biet li trong viec trien khai, khi c6 rit it xe duqc trang bj, cac hien pbip dim boo kit n6i b6 sung cho den mot dO cin thin cho nhieu erg dung sau nay disking xuyen duqc xic nhen. H9 de nghi phis Lich tic dOng ctia cc( s6 ha tang bi• sung caz don vi ben le dubng. Thiet bj ca s6 ha ding nhu 4y di xuit hien trong cic tai lien khic nhau. Vi du trong Goodman, cho thiy ngoii cic thong tin nhu gii sang c6 the dtVqc ctmg cip thong qua cic he thitng thong tin, hok chi dun gian b6i diem truy cep WiFi. Cie dieu khoin khic di duqc so dung trong cic di lieu bao g6m (c6 dinh) cac "On vi h6 trq" vi "don vi ben le Queue Roadside Unit (RSU). (3 dity, se so dung thu#t n thir hai.

RSU n6i chtmg ce the hi mOt tong hai thief bj dOc lip ma chi giao tiep v6i cac phuung lien thong qua truyin th8ng kheong dity, ho#c chimg c6 the thrqa kit n6i v6i nhau thong qua mOt mpg xtrung song, tfr d6 c6 the duqc thqc hien hok bang c6 day ho#c co se ha ting khOng day (GSM, UMTS,...), hok thong qua mOt along lir& call cite RSU. Ve ca ban, muc dich ctja chkg 18 he lute kit not VANET cic ngu6n thong tin ben ngoii, hok de gia tang khi Wing kit not hoc khi Whig cda mpg. Vi du khi duqc lip d#t tai cOt den giao thong, cic thiet bj nay c6 the nhen duqc thong tin n1 xe 8 to di qua vi se thong bao cho cac xe mtfli duqc tiip cen yeti de lieu nay.

1r Mang cda vier so dung logi co ar ha tang thief bit nay lchong phiti lit mei. Tr?, lai rim 1964, Bowes vi Covault trinh bay ket qui tb mOt thtl nghiem dtrqc so dung truyin thong phit thanh ben dubng. H9 di phan tich cho du khi thi de cii ck RSU

a cung cep cic trinh dieu Bien them th8ng tin vi kiem soft giao them*. Ben canh

nheng thich that 1/ thuet cda he thong nhu very, ngteri so dung phai chip nh$n vi chi phi di duqc d(tt thanh yin de. M#c dtl dieu kien lien quyet ky thuit la khli khic nhau, cac muc tieu ctia cac don vi ben throng di duqc so sixth yeti nhung thao lu$n nay nay. Nhttng sq c6 khic nhau di duqc tit* nghiem di c6 mOt s6 filth huong ye an toan hooc hru luqng giao th8ng. That bj v8 tuyin duqc cii d#t trong xe nh(tn duqc cic tin nhin

27

•

LkIU UNU 2. iruyat tnong trong mpg V anet

tfr cac cac don vj ben dating khi di ngang qua. Tr& voi thong diep dft lieu ky thigh so stl dung ngity nay, ho sak dung tin nhin thogi diu ra thong qua loa phat tharth.

Vi m#t thuyet ph& tich hieu suit (Art cic loci khic nhau tong c*c don vj ha thy. D#c biet, xem xth cic kit nai RSU )(gang sting, ho#c cic he thong ea so, mpg luei RSU, va cec RSU doc 10p. So sink s6 lugng 110 thiong clin thiet d4 gift cho sq ch#m g6i tin tap. MOt kit lu#n la can nhieu han rat nhieu (5-7 lin) KW dimg mOt minh de dot duqc hieu suit Wang to nhu yid cac hu thing co so kit n6i yeti nhau. Banerjee dung mOt m8 hinh tau tuqng, ngtiu nhien chuyin dOng nut. 106i vol RSU dOc lip, nut di chuyen la quan tong di cung clip thong tin din cac Ang Mt hon. Trong thqc to cac nut trong VANET thubng xuyen di chuyin theo mOt huemg (v1 du nhu, dal vol trung tam thanh ph6 trong gib cao diem bu6i sang). Nhu da di cup b ten, cic img dung then hinh ph6 ban th8ng tin tim xa_yeu ciu thong tin di theo Wang chuyin dOng chinh. RSU kit noi yeti nhau c6 the dap Ong cac yew ciu nay vi phanh cheng cung cep thong tin den cac yang xa xed - hieu quit km nhieu so v6i cac R$U &mg mOt minh. VI vily, trong thuc to VANET, lqi Ich hieu suit cua mpg RSU c6 the (Iv lden se thitt thOm chi con 16n horn.

Cic RSU sear dung cling mOt Ong dung nhu cac phuang lien thong thding. Di c6 mOt tic dOng ding ke, cite don vj ha trq duqc kit nal voi nhau thong qua mOt mpg xuang stag, chin hpn n6 c6 the sir dung mOt nen tang Id& thfrc chung: ngay sau khi mOt dun vj nh#n duqc mOt s6 thong tin, tit ca cic cac dan vi ha trq khic c6 the stl dung ne vi dep tic phan ph6i. Trong Locher, kiln Ira tic dOng ales s6 luting cac RSU yeu clu vi vi tri ctla n6 trong mOt thinh ph6 vac) thoi gian di hti tilt kiem dirt duqc vai mOt he thong dire tren thong tin giao thong VANET, va co the sit dung mOt sa thu#t Wan di truyin di tim kiem vi tri tat nhit cho cic RSU.

IChai niem ve RSU Ithong bj gi6i han stir dung yeti cic chuong trinh (cid:9) Win mac Vi du, phin tich lam the nio cac RSU dec lip hotic kit nai cung cap thong tin lien 1pc di ding horn gitta cic nhom xe. Ttai day, ca ban cic diem iruy cep RSU thrqc d#t ben dubng, cang them gia trong giao thirc phan Whom.

2.3.2. Truyin tdi tisOng tin

Trong khi thin Min lam the nio de vin chuyin th8ng tin trong mpg, nhieu nghien cfru citing xem xth truyen mOt phin cha thOng tin ho#c bin tin. Mire dO pha hqp chirc Wing sir dung so skill drill moi ho#c tim quan trung c6a cac bin tin sin ch. Co the stir dung tu6i vi khoang cach den mOt ngu6n tai nguyen cho cic chrrc Hang phi hqp, hotic phin lopi cac tin nhin nhin (taw theo teem quan trong cfia no. KM truyen tii kiln thirc dja phuang din cic xe khic, mOt ban tin day la cho din khi Idich thu6c goi tin dot tai da. Dieu nay se giap cic kich thy& ban tin 6 mOt mirc dO c6 ajnh vi tranh

28 11-1/UUNt-tl. Inwen tnong tin trong mpg vanet

tic nghen mpg. Citc s6 lieu khic de quyit djnh mOt phin th8ng tin dja pinning cin phai duqc truyin duqc de xuit t6t trong Saito cho catch tiep ckin khic nhau. Trong mOt phuang phi!" lira chon xic suit Ichang ci sip the to cac thong tin (kw thqc hien nhung cac de lieu duqc gel duqc xdc djnh mOt cach holm town ngiu nhien. Cling ci di nghj sip the to cac th8ng tin dua vio tu6i cult ni. Trong trubng hqp ma chi sir dung cac th8ng tin mei nhit va phuang phip nay xem xet viec truyin th8ng tin ca di khemg lam mit th8ng tin.

Trong Fujilci gift djnh ring th8ng tin v6 cac yang lan can Wit mOt chic xe duqc yeu ciu thubng xuyen hcm thong tin ve mOt khu Arc xa x6i. VI thi, btu ich di truyin tai cac de lieu thubng xuyen hon. Adler di nghj tinh toga lqi ich town ciu (ctla mOt ban tin duqc gtlti. Quyin lqi nay duqc s>Sr dung di them s6 quy trinh truy c(Ip trimg binh. MOt ban tin thich hqp duqc diu tien, gig dotal r-Inh tranh &Tr sfra dpi theo thir ttir uu tien clic ban tin. Diiu nay duqc thuc hien bang catch thich nghi voi kith thy& cua eft s6 canh tranh. Tuy nhien, trong mOt flied trilling c6 truyin di va xem )ott Oak suit) m8 hinh Ian truyin thuc ti hon dai phat thanh, nhung di la mOt phtrong phip uu tien c6 the se khong dal digit hieu qua mong mute.

MOt catch dip cfn ngim ho#c tang thii mim di chia se thOng tin tong mOt Ichu vuc giii ban. Gii dish ring niu hai chiic xe dap img, ni se trao thec dja phuang cua ni. Di Ilan chi kich thuOc cua thong tin, chi c6 cac muc mai nhit duqc truyin di. Mig 'chic, bing each them thong tin mai vio cac car so de lieu di hilt, de lieu hien ci se c6 tu6i va mit sau mOt thoi gian.

Ngoii viec c6 the di thong tin ban do vj tri cac thuc the hqp IS? trong mang lux% throng bO, cac th8ng s6 finh cila mpg lubi dubng bO duqc Wet din Uri a* he thing djnh vi (thing hen nhtr, tic dO d#c trong tree nhttng con dubng) cling c6 thi duqc sat thing rit len giup tao de lieu di la btu ich trong cac eng dung VANET. 146 la mOt lua chon that ki di thong ha° cho cac xe khic chi trong Inking hqp lech gia trj "dien hinh" la ding ki. Vi dy, mOt Ong dung thong tin giao thong ci the bio cat) thbi gian di chuyin chi khi ho c6 khic biet ding ki so vii nhttng gl thubng duqc du kiin tren con dubng tuong (mg. Phuang phip tip ce ► nhu v(ty c6 kha Jiang c6 thi tiit kiem bang th8ng. Di danh gig tai dja phuang cho dd tin tai dO Nth, thin gian di chuyin tuong Ong til cac de lieu ban doS tinh cila he thing dinh vj c6 the phuc vu nhu le mOt tai lieu them Ichio.

Tuy nhien, c6 mOt vin di chung mkt cgc phuang phip tier, Qin “t6i (cid:9)

truyin trong trubng hqp IchOng Co thong tai th8ng tin duy nhit tong nhttng hoin canh cu (cid:9) tin nil° algin duqc, n6 la khong tt rang cho tau nay bl do thuc ti ring tinh hinh la "binh thubng", hotic xem lieu ci don gian la kh8ng ci pile') do hien tai, vi v$y kh8ng

29 l...1-11JUNly Z. 1 ruyen thong un trong mvng vanet

ce gi duqc bat den. MOt lin nea, toy thuOc vao cach thong tin duqc sb dung va gill thich bai cac (mg dung, dieu nay c6 the duqc chip nhin hay khang.

2.4. TONG HOP CAC PREP DO

Cac phip do tyi die phtrung di duqc giai thieu de lam the nao co the thu duqc de lieu va tim ra mOt s6 phuang phap de ce the truyin &Ong tin nay den tay nguei quan tam. Tuy nhien, viec phin phii tit ca cic phop do rieng le duqc thyc hi(in bai tit ca caz xe 6 t6 cho ben nhin nprai quan tam tree &rang, khu vyn la c6 the duqc ve ring it thuyet vi tuang tuqng - nhung dieu nay hien nhien la dieu khang the. VI the, co che yeu ciu giam so luting de lieu tong mang hong khi cac thong so mai toding duqc theo del bei he thing khac, ma vi tri ctia xe va ciu tic wing luen luan thaw va de lieu duqc trao d6i 6 bit dr nui nao ce the. Do vty trong phin con lyi cia thuung nay tip trung vao the vin de t6ng hqp, gong hqp so lieu do luting.

Trong cac (mg dyng phi bien VANET, thubng lit train hqp c6 nhien phep do ten thng hoic tan cdc thyc the quan sat lien quan chit che ce s&n trong mpg. Vi dy, nhieu xe c6 di qua cang down doting, m6i xe trong s6 di lyi do thin gifts di qua tha mink. Neu ching duqc kit hqp thanh mOt gia tri duy nhit, vi khong cin that de ltru ter hai gia tri tyi et diem. Quan trqng la sau d6 ding khang can thiet phai truyin hai gia tri lchi thong tin duqc trao don gifts nhttng nguai them gia myng. Myc dich tha vier ket hqp lit de tao ra mOt de lieu duy nhit phan anh duqc thong tin. Gqi la qua trinh kit hqp nhieu quan sat t6ng hqp.

MOt hq hang ca tong hqp la tip hqp, va su khac biet gift tong hqp vi tip hqp khang phai lic nao cling re rang trong cac tai lieu. (3 dily, tip hqp ce nglia la de lieu lien quan den nhttng thuc the khac nhau va duqc ket hqp thiinh mOt gia tri. Myc Bich cia tip hqp la de two ra dyi dien de lieu kb& quit cdc khu vyn b khoing cich lan ham, ce the tiet kiem bing th6ng thim chi con ket hqp cac phep do nhieu thane s6 twang tv thong qua tong kit. Trong phi n flip theo se de cip den tip kip. a. 7157/s loin one mi awn bank

Hinh th(rc don gian nhit c6a t6ng hqp de lieu la khi mOt thiet bi them gia vao VANET thl phai dii nit vai hai gia tri rieng biet cho mOt them so (vi dy, $6 luqng ch8 418 xe mien phi tren mOt (Alt diem d8 cy the, hoic thbi gian cAn de di chuyttn thug mOt down &rang): mOt trong cac gia tri c6 the duqc ltru tre tong co so de lien di cis ni, gia tri khac duqc liy t>Y mOt ngu$n th8ng tin. Vi dy, chi& xe c6 tuft di thuc quan sit cac tham so rieng va bay gilt nhin mOt gia tri twang ty UY mOt chi& xe khac. Int nhttng th8ng tin them nhu nhin thai gian duqc luu tie vi duqc truyen cunt vOi de lieu thl ding khang phai la d8 clang chit de guy& dish co neu cep nhit gia tri hien tai trong cu sa de lieu cin hay khang. Xu vi Barth thao luin ve cac vin de gong hqp de lieu

LIIU UM.; Z. iruyen thong un trong mong v anet

trong bii canh do thbi gian di chuyen doc doon doing. Hq thiet lap khe thbi gian cfs dinh mubi phut, va ting kit cac phep do thin gian di loi ten cOng doon dubng thuOc_ cUng khe thbi gian. Phuong thirc diu tien, khi thbi gian di loi doe theo mOt doon dubng la nhen duqc tir mOt chiec xe Ichic, clic gia tri nhan duqc mkt dia phucmg &roc tinh trong binh, va gia tri trong binh duqc hru Ire trong ca sO du lieu di biet. Tuy nhien phuang phip nay clang Wong hoot ding tit. Vin di la cac pile') do duqc thyc hien som Ara° diu ctla mOt khe thbi gian thi gia tri Inmg binh ty gong &roc cep nhat. Khi them cac pile') do duqc thyc hien sau nay, cac gia tri lirc diu di duqc cac xe khic biet den, vi vay ma ho thubng nhan duqc cic thong tin men.

b. Nita do& gian dira tren so stink

Vin de nay chi ra Wong ye bi sung clic gia 14 do luting bang nhln thbi gian. Khi mOt chiec xe bit diu quan sat, no luu trf klittng chi co gia tri quan sat thiy tong ca sir de lieu coa no, ma don thbi gian hien hank. Khi de lieu duqc chuyen den nhftng ngubi khic tham gia trio mong, cac nhan thbi gian duqc gui cOng vofri caa gia tit MOt ca the "tang hop" dan gian ne thubng duqc sir dying trong cac tai lieu la de thay the cho cac pile') do cu bang nheng phep do moi han, tren ca dr so sinh nhan thbi gian. Phucmg phip nhu trey gia dinh ring cac dam vi ding gap diy du chinh auk ding bO thbi gian. Day lchtong phai la bit hqp 1Sr khi VANET cho phEp xe sir dung mOt s6 he thing nhu GPS b moi nai. Cac he thing My c6 the ph ► c vy nhu la Intl nguin thbi gian co dOi chinh xic cao, va do dO yeu ciu mist ding bO thbi gian la khong qui nghiem tong.

Nhan thbi gian dya tren ca the so stinh chic chin tranh duqc yin de ma clic phep do ce vin tin toi trong mong va thay vao de la ale iii tri moi hon dtroc thay the thubng xuyen. Tuy nhien, no Ong ca nghTa ring gia tri trong co so du lieu cua mai chile xe se luon lute xuit phat tilr sy quan sat duy nhit. Cho du day la mOt vin de hay lchtong phi thuOc vim img dung, dac biet li no phy thuOc vao cdc nguOn ft lieu cu the: tong he thing giing nhu mOt de milli caa Caliskan, ncri ca so ha tang cO ainh ( toi cdc (ha diem d6 xe) too ra cac phep do gin nhu chfith xac, gia tri mai han se twc sy lute luon m8 to tinh hinh hien nay tot han so voi nhftng cai cri han. Nhu tray, tong trubng hqp nay, thay the clic phep do ce dua tren nheng cai mei han la chic chin thick hqp, va la mOt cach dl ding de dot duqc de lieu chit luting tit.

Trong nhftng tinh hutong khic, dac biet la khi etc pig, do bi nhilu viec chi gift loi mOt gia tri cep nhat mad nhit khong phai la mOt ttrang tit. Khi thbi gian di chuyen thong qua quan sit troc tiep mla nhftng chi& xe, anh hiking den cac yeti t6 nhu cacti lai xe, cac tin bleu den... co the gay ra cac hien dii lan. Vi trey mil cac do Wong 'thong phin ail dung tinh hinh thyc te.

31

Ltiuuriv 2. iruyen tnong tm trong mane v anet

c Moan thei gian dira fin link lode trims birth

Xu vi Barth dang tranh cii ye hai huang phit trien chuong trinh tinh toin trung binh thbi gian mil. Ci hai thuit toin deu gin shin thbi gian cho gii thbi gian di chuyen. Cich tiep diu lien la riga tren gin gii trf tali hon tong ltrog &tip hob tren trung binh: khi mOt quan sit man duqc thuc hien hoic khi gii tri nhin duqc tir chiec xe khic (khOng phan biet cho du diu thbi gian cult n611 man han hotic ion hen), tide toin tong luqng trung binh duqc thuc hien, gii trf ntlo ci hon thi se duqc gin tong s6 thip hon.

Vol cich tap centh ba, de nghf cop Whit thbi gian di chuyen dua Oen co so de lieu di biet chi khi tu chiec xe to ra mOt quan sit man han; xe 8 to khic tit nhien yin h6 trq trong viec phin ph6i cic gii trf trung binh. Trong do, cic phuang time luu trQr s6 luong miu trong cic khe thbi gian hien tali cho den thbi diem hien tai, lcS7 hieu la n, T Whin thbi gian cis cic quan sit mai nhit dang gap vio gii trf, vi gii tri thbi gian di chuyen trung binh v bin than. MOt o gii trf cia them s6 nay mad duqc quo sit thiy c6 the sau d6 trong xe quan sit duqc tich hqp trung binh trong mOt cich thick hqp, tao ra tic v gii trf man, theo each sau:

v, =

1(nv + a) (2.1) n +

Khi mOt bin clip nhit duqc thuc hien, T duqc clip nhit den thbi diem hien tai, vi n duqc tang len. Cic thong si n vi T duqc trityin din cic xe khic cling vai gii trf trung binh hien tai. Khi dft lieu duqc nhin cic phuang tien khic, dtra hien nhiin thbi gian T hoic gii tri cµc bO hoic gii trf nhin duqc se duqc ltru lei; gii trf ci hvn trong hai gii trf tren se bf

De in nay bio dim ring m6i ink chi duqc tinh mOt lin trong cic gii trf t6ng ket, with ca cite pile') do nay Op pan vio gii try' trung binh co cOng trong s6. N6 yin c6 the xiy ra, du, cic quan sit niy duqc thuc hien b6i mOt chic xe vi bao g6m gii tri bf mAt trong tic buac sau do. Dieu niy xiy ra trong tinh huing sau My: gii set mOt chiec xe A thuc hien mOt quan sit vi dua vio trong ca sa dtt lieu di biet cia no. Trong qui trinh hoot dOng, ne ding clip nhit nhin thbi gian lien quan. Sau mOt thbi gian ngin, xe B ven chua nhen duqc de lieu cep nhet tb A, nhung n6 ttr thuc hien mOt quan sit cue thong s6 nay, vi doh hop no vio tong gii trf cqc bO tuang (mg Oa no. DO lieu trong ca so dft lieu di biet cue B Wong c6 tic quan sit cilia A, nhung n6 mang mOt nhin thbi gian man ban. Klu hai mqc de lieu nay duqc trao d6i trong mpg vi duqc so sinh, dtt lieu cia B se "thing" vi thay the citt lieu cue A, do d6 uu tien hold dOng cep nhit duqc thuc hien sam hen b6i A. Vi 4y, deng gap cua A se bf mit. Bit chip ket qui nay, Xu vi Barth tim ra ring trong ba de in ma ho de xtdit, phuang phip nay mang lai cic trinh bay chinh xic nhit cia cic gii tri thbi gian di chuyen chinh xic.

d Trung binh plain dope Swam

ILINU 2. 1 ruyen tnong un trong mpg v anet

MOt Win the lthic cia qui trinh fink toin tnmg binh duqc sir dung tong SOTIS mkt Wischhof. Cic ca chi chung ip dung cho tong hqp th8ng tin ttl nhieu ngu6n duqc (SODAD). SODAD lit gqi li Segment-Oriented Data Abstraction and Dissemination dine ten mOt phin cia doan dutmg. Cic dap throng duqc ma hea cimg, do de tat ca cic xe d6ng nhit tr6n cling mOt phan doan, vi m& don c6 the dace gin mOt ID duy nhit. Tai dja phucmg, cic phep do cia m8i xe duqc trao d8i gifta tic xe, do de mOt chi& xe nio de se c6 the thu th#p nhieu miu tiY vung lin c(In ngay liip tire. De ph6 bier thong tin cho cic khu Arc xa hen tong ming, xe se kit hqp cic miu ma n6 c6 cho tic phin don dutmg lchic mi n6 dang di. Khi tao, tic gii tri m8i (loan duqc gin mOt nhin thlri gian th6i diem t6ng kit di duqc thuc hien.lChi n6 duqc ph6 bile tong mpg, nhin th6i gian xic dinh gii tri hien tai tong co str de lieu ho#c mOt gii tq moi nh#n dirge luu gift.

T6ng hqp SOTIS Doan during ID: 43 T6c d5 hung binh: 47.5

•

Tic 50 48 (cid:9)

Tic d0 43

(cid:9)

T6c tIO 52

T6c 4:10 47 (cid:9)

(cid:9)Don (krona 43 (cid:9)

Hinh 2.3 T4ng hqp toc d¢ cue xe tren miii phdn dogn trong SOWS.

Ch6c ning quyet djnh cic min rieng to se duqc kit hqp nhu the nio vio mOt tong kit 6 m8i doan, li (mg dung phi) thuOc. Trong throng hqp cu the curt SOTIS, the (mg dung dine ten trao d6i thong tin ve vin t6c cia xe. Tham s6 do t6c xe hien tai. Tem tit tic thong tin vin t6c mkt xe bang nhieu pile') do tren cling mOt phin down dutmg, gii tri trung binh duqc di:1h toin. Bien de the hien trong hinh 2.3. 2.5. TONG KIP DIY 'nu DIA Lit

Cic ky thu(tt duqc deg hqp thio luffn tong phin tnr6c cho phep so sinh vi kit hqp dftlieu tt nhieu lin quan sit lien quan din cling mOt thaw stS, gi6ng nhu t6c dO lii xe hien hank ten cling mOt don &Ong trong SOTIS hoc s6 nui d6 xe ran phf ten cling mOt nai d xe trong hu6ng din d xe ccia he thOng cia Concklin. Nhu v(ty, tong kit c6 the gift s6 luqng dft lieu cua m6i lilting s6 duqc do kitOng that' dd. He thong thrtrng lan hen of du nhu trong tan think ph6 ho#c mOt mpg luii du6ng cao t6c, tut' vin con c6 mOt s6 luqng lan tic dft lieu bj mit: s6 linyng cac don Mow trong mOt thinh ph6, vi du, nhu li s6 bid d8 xe nhieu han. Nei Chung, neu quan sit cic thong duqc dOng nhit vi dutc phan phiSi tren khu Arc cilia ming, sau de s6 krung ccla nto se

(AIU UNIT L. inwen tnong un trong mong v anet

ting birth phuong vii bin lcinh duqc bio dim. Olt% hon bling thong c6 s&n cho cic Ong ding phi Win trong VANET se kh8ng cho truyin lien tic th8ng tin chi tiet nhu v$y tren lchoing cich dii, lutin luon duy trl mOt trong thii tot trong toan mfg.

Di khic phic hon chi nay, di ce di xult str ding Icy thu#t mong der lieu t#p hqp, nhibn muc dich kit hqp cAc gia tri hien t?i coa nhiIu tham so vio mOt gii ding hqp duy nhit. MOt gii tri tong hqp c6 the li t8c dO trong binh ten mOt down cas duang cao t6c, hoc t6ng s6 dia diim d8 xe milli phi trong ci thinh phi. Trong phin nay se neu ra cich hqp de lieu cho VANET. a. GOp cdc nhont xe twang tr

He thOng quan sit luu luqng cua Nadeem nhim moc dich to diet' kien thuen lqi cho plain ph& hqp tic giim sit giao th6ng cda doon dusimg cao t6c phis tram cOrt chit c xe. Moc lieu niy tuong to nhu cM SOTIS, nhung hi thOng quan sit hru Itrong c6 mOt cich tiip lchic dOi v6i cic loci thong tin c6 sin qua mpg. Quan sit luu luqng dlra tren du lieu vi vi tri hien toi vi t6c dO mkt tfrng phuong den eh* Idiong phii la ten vOn tic trong binh tren doon throng nhu trong SOTIS. Vi s6 luqng de lieu nhanh chong vtiqt qui glen hon, mOt co chi thich nghi gip hqp duqc s6r ding. Toi dirt phuong m8i chic xe c&t gitt dash sich ID ctia xe, vi tri vi tic de. Ch'ing duqc troy& den cic xe lAn c#n thong qua cic cinh bio. Kich thu6c ctia cinh bio duqc gioi hen, vi do d6 cot chi duqc gioi thieu di &gm s6 luqng de lieu nhung ding thOi phii truyin dot gin dimg thong tin vi phuang tier. 136i vii moc dich niy, cic nett ctla he thOng quan sit luu luqng stY ding hg so t6ng hqp trong viec twin tai. H6 so tong hqp ales ti khong phii la mOt phucmg lien duy nhit, ma li nhem cic loci xe voi tinh chit tuong to.

NW hi so tong hqp trong quan sit luu luqng bao elm tic dO duy nhit, vi trl, vi gia tri nhan thoi gian, cung voi mOt dash rich cic ID ctla xe. Dieu nay se flit Idem bing th8ng cho truyin cic gii tri rung biet cho m8i chiic xe rieng le. Cic gii tri tic dO vi vi tri trong ghi chip tong hqp la tong s6 tnmg blnh tren cic tham s6 tuong img cua m8i loci xe trong h6 so. met bleu di tong hqp duqc thi hien trong birth 2 4 He thong quan sit luu luqng de xuAt cic toin tong hop la tham s6 cho cic khu voc cite (loon dulmg phis truck. Cic thong s6 diu vii quan tong nhit la ty le t#p hqp, cho thiy c6 bao nhieu xe non duqc kit hqp thinh mOt tin hop, vi so luong dit lieu ce thi duqc truyin cho mOt khu voc nhAt dinh. Doa tren cic th8ng s6 cba he thing quan sit hru luqng sau d6 hqp cic gii tri thich hop, nhim gift cho cic 18i la nhe nhit.

Di in CASCADE cda Ibrahim Vil Weigle cho th&y mOt s6 diem tuong ding voi cich dip gin he lilting t6ng hqp quan sat hru luqng. N6 cling phi') phOi thOng tin vi vi tri vi vOn tic cM xe voi nap tieu h8 trq nAng dOng 10 With ki hooch bIng he thOng dinh vi tren mong. CASCADE siY dung c6 phip nen c‘un cic loci xe c6 vi tri vi van

°NU2. i ruyen tnong Un trong.mang v anet

t6c tuong ttr nhau. Cic nhem phuong tien duqc tem tat trong mOt bin ghi, not s6 ltrqng de lieu cho mgi chi& xe trong cic ban ghi duqc t6i that' hoi.

Trung binh Traffic view VI tri bung binh: 9.96 T6c 60 trung binh: 47.5 Thoi glen nh6 Mat 12

ID xe: 1, 2, 3, 4 •

ID 2 VI tai 14 T6c CIO 52 Therl gian 16

ID 1 (cid:9) Vi tri 17 (cid:9) T6c CIO 47 (cid:9) Merl glen 12 (cid:9)

ID 3 Vi trl 8 T6c 69 48 Theri glen 15

ID 4 Vi trl 4 T6c dO 43 Then ciao 16

40' dilio

Hinh 2.4 He thing quan sat luu luvng

Trong CASCADE xe ce th8ng tin chi tilt Ye teng xe trong khu Arc d6, (cid:9)

goi stir hieu biet chi tilt cfia mOt chi& xe duqc AA lh " tim la "bin ghi chinh". (cid:9) Cic pinning tien th8ng tin c6 sen duqc nhom lai thin& cic cum nly nhin cic (cid:9) thuOc vao khoing catch chiec xe , nhom va dO cao ciut xe. Cic cHt ligu lien mOt chi& xe trong cic cum hO so sau d6 duqc nen bing catch the hien toa dO xe vat tOc dO twang d6i so yeti cic cum thing tim vi van the trong binh. Sau d6 mOt bin ghi cum tong hqp c6 chira vi tai cum (tuyet d6i) vi the dO,va mOt bin ghi ngin gon (co tQa dO Mang doi so Yeti cum) cho m8i chi& xe trong cum nhu the hien trong hlnh 2 5 T6ng hqp thong tin duqc phin ph6i tren mOt khoing catch deli ham. 'Chi nhin duqc bin ghi tong hqp, ho hqp nhit lai de c6 "cii nhin may rang" ye phin hOi cis xe.

SOTIS, he thOng quan sit kin luqng vi CASCADE du c6 mOt s6 diem Wong dOng. Ca ba dew thu thip th8ng tin ye vi tri vi the dO cis xe, vi ket hqp thong tin ye pinning tien vbi cic gii tai tham s6 twang qr. Khong cii nio trong s6 cic 110 thong nay h8 trq kit hqp phin cep cic th8ng tin tren tan bO mpg luai &rang b0, tirc la, thong tin tren nheng con &king khic biet lA khong bao gib ket hqp. VI viy, Oheng trueng hop trio nom gitta tong hqp vi tip hqp. 6 day, guy& dinh phin loai cic co chi SOTIS de gum de lieu nhu li tong hqp, vi he thong quan sit bin luqng vi CASCADE nhu li kit hqp, vi SOTIS xem xet de lieu xe lam milu cis tham s6 cOng mOt vin tOc tree mOt doan dubng vi saw d6 tem tit cic min nay. He th6ng quan sit luu luqng vi CASCADE, nguqc lai, coi xe rieng biet do Q6 d6i xti nhu nhung thuc the quan sit khic biet.

LA-1U ONLY L. i ruyen uiong tin trong mang v anet

NhOm cic ban ghi CASCADE

VI VI bung tint- 10,75 T6c el) trung blnh: 47.5 Bin ghi cep nhet ID 1, vi tri chanh lech +6,25, vin the chenh lech -0,5 Ban ghi cep nhet ID 2, vi trl chanh Itch +3,25, 4n the chenh *di + 4,5 Ban ghi cep nhat ID 3, vi trI chanh lech -2,75, van the chenh Itch +0,5 Ban ghi cep 'that ID 4, vj trt chart Itch -6,75, van bk_chanh tech -4,5

ID 1 Vi trl 17

d0 47

ID 2 Vi trI 14 T6c dO 52

ID 3 VI trI 8 T6c dO 48

ID 4 Vj trt 4 T6c d0 43

Binh 2.5 Tong hpp nhem cdc ban ghi CASCADE

b. Ain lofd dlt in then nhom

Trong he th6ng StreetSmart cda Dornbush va Joshi gild quy& nhttng vin di cia mOt he th6ng giim sit phan ph6i giao thong tit mOt gdc dO khic. Trii v6i phuong phip tiep cen dA &roc thao lu#n cho den nay, StreetSmart kliong trao d6i bit try' dl lieu vi met xe hotic doon dudng. Trong StreetSmart, mgi miu h6 so xe cc, ban la vj tri va the de tren con throng chuyen den riling cda nd. Vj tri de lieu ci nhan trong StreetSmart &roc dai diet Uri mOt ID diang vi mOt Ichohng thing. Nheng miu nay Icheng truyin den cic phuang tien khic. Ching la d6i tuqng chic bO Oa thu#t khai thic de lieu, de two ra mOt cii nhin trilu Wong hon. Quan diem tong hop nily dirqc truyin qua mpg.

Cic miu t6c dO/vi tri cuc bO t6ng hop bing cich citing mot co the phan nhdm de lieu v6i nhttng bier phip Wong to nhu mOt ing dung phi hop. Bien phip nay phi thuec vao dubng (1) phi') do dA duvc thoc hien, (2) vi tri doc then throng, va (3) t6c de ghi duqc s>Y dung de xic dinh them miu the hien t6c thAp bit ng6 tren mOt va khong tuong to trong cic tieu chi die di c#p 6 teen. Neu cum miu the hien met t6c dO ma khong phbi la Ulu bieu cho diang twang img, Un tic giao thong dim gib dinh t6n tai. Cum nay duqc ip dung sau dd th6ng bio cho nhttng ngudi khic trong mpg, m8 ta tau Wong thong qua cic cum tong tam.

VI vtly, trong khi StreetSmart cung sir dung Run cis t#p de lieu twig to, cic be de lieu miu la vi tri/t6c dO diroc thu th#p qua thdi gist xe twang to ahau, cic he th6ng truck dd thao luan quan sit luu luting CASCADE h6 so fling hop vi tr1/t6c de tfr cic lo3i xe khic nhau.

C. nip kw trin cdc Ichn vise plan cip

Cic phuong phip tiep gin de ctip al de lieu t6ng hqp tiY cic phuong ties khic nhau, hoc cic phi') do nhau lien tiep dtrqc thoc hien bdi nhttng xe hrong to nhau.

131-1U (cid:9)

iruyen tnong un trong mpg V anet

Cac phucmg phip d6 c6 the lam gum ding ke thong tin duqc trao d6i. Nhung n6 lei khong khic phut duqc cic vin de ve m6 rung vi hai ly do. Ly do this nhit lit cic phuang phip d6 chi c6 the ket hqp de lieu tren mOt con throng vi Iii xe theo cling mOt huang. Vi v#y t6ng de lieu trong mpg Yin nhanh cheng tang len v6i kith thy& bao ph0 mpg thrbng b0. Ly do thin hai va c6 le thin chi con quan mpg hen la Itrung dilr lieu sto luqng xe dang ngay cling gia tang: tong he th6ng quan sit luu luqng va CASCADE, tip hqp china dash sich cic ID g6m xe. VI 4y, giam s6 luqng cic byte duqc stl dung cho m8i chide xe, nhung ldch thu6c mkt nhitng tip hqp Yin phit trait tuyin tinh yeti s6 luqng dit cic trubng de lieu. Trong StreetSmart, phep do cvc b0 duqc tip trung, nhung mOi chide xe phan 136 trvng tam Cu n6 trong m0t mpg luoi hoin chink, khong can tip hqp them, do de, tlang de lieu tang len cling vol mOt luung lan xe(ho#c bang, mOt khu we duqc bao 16n hun). VI v#y xem xet de xuit nui ma kich thu6c va s6 luqng t6ng hqp de lieu dal dien la dOc 1#p yen s6 luqng phucmg den do, va s6 hrqng de lieu khong tang tuyin tinh v6i dien tich (ho#c vol s6 luqng ddrng trong khu Arc duqc bao phi).

Cic phucmg phip dip cin diu den dat doge mOt tang thai nhu v#y da ducm de xuit trong Caliskan vi Lochert. Trong nheng deg trinh, khu yvc dva tren m8 hinh tip hqp duqc s(r dung: vol khoing cich ngay cling tang, cic phep do tar cic khu vine 16n hen vi 16n bun duqc kit hqp vao gii tri t6ng hqp. Bai au xe phan cap huOng din chucmg trinh duqc m8 ti tong Caliskan st1 dung mOt chucmg trinh t6ng hqp. Ca so ha tang dirt phuong tai m8i nui xe duqc std dung ngay trong viec t6ng hqp thOng tin ye toan 130 thbi gian au xe curl bai d#u xe. Dieu nay duqc thanh 1#p tren gia dinh ring tic bid au xe 16n hen thutmg se c6 ca so ho tang cho viec thanh toin hay cho phep cai d#t theo bit ki each nit° do. V(iy ca so ha ding di ce the sin sang aftp nhtt t6ng quan cia viec dung do tai bai xe. "Nguyen ttl" (Atomic) th6ng tin ye firth tang chi& dung hien tai cua mOt biti au xe duy nhit. Trong mpg, cic tip hqp doge hinh thanh. Cic tip hqp nay dpi dien cho tinh hinh bai xe b cic 134) phin cia mOt thanh ph6 lon hun, bang each m6 to t6ng s6 dia diem au xe man phi tren tit cit cic bai au xe trong mOt s6 khu vvc lon hon. MOt phan khu c6 dinh cia thanh ph6 duqc sir dung, dirge quy dinh bei mOt cay tar phan (Quadtree) trong m#t phing hai chieu. Cay tar phan la mOt ph& khu thir b#c cua m#t phing thanh cac hinh vuOng nhe hun vil nh6 bon, nhu slurp chi ra trong hinh 2 6 Trong vong bin kink nhit dinh, thong tin ve tit ca cic bai d6 xe ci nhan &Km trao d6i tong mang, Ir nhQag khoing each lon hen, chi c6 gia tri t6ng hqp duqc sil dung. Nhung gii tri t6ng hop tr6 nen th8 him va th6 hen cic khu Arc xa hen duqc m6 ta. Cac dOng Ivc di tip hop phin cap r0 rang hY cic 'bag dung tip trung 6 mOt khoing cich lan hen, ne la &I de biet ve tinh hinh gin ding vi chi dao th8 nui au xe c6 the duqc tam thiy. C6 the !thong can thiet de Met mart dt) chiem dung chi tiet

37 1,1-11JUINli Z. 1 ruyen tnong unirong mpg V anet

xe. Xe gun han se den khu Arc dich curt no, thong tin se duqc cfra tat ca citc bai (cid:9) cung cAp chi tiet han, de cu6i cung ce the duqc guy& djnh cho mOt Mai au xe cu the.

1111111PrAgir rilrarr

Hinh 2.6 Cdy tzi phdn

Phucmg tien di lqi du& dung tip hqp mkt mirc thitp nhit (dm la, cic to brio trong mpg luoi cay tit phan nhe What) bang each them s6 luqng dja diem au xe mien phi duqc hitt den trong khu Arc. D6 la, lieu mOt chitc xe da nhOn duqc thong tin nguyen ttl mOt s6 nai dOu xe trong cong mOt to bao quadtree, ne c6 the to ra mOt tang hqp cap dial) nhAt. Nheng t6ng hqp nay lui duqc su clung lin nu& 6 khoang each 16n han trong cac muc dO cao han cilia he thong phan cAp quadtree. Chung &Km tqo ra tfr tap hqp cfra cic cap dO dip theo han, bing cfich them clic con s6 tuang Ong cfra nai dui xe mien phi tfr bon thank phin tang hqp nhe hon. VI vey, tap hap 16n hon la phan cap duqc tqo ra tfr tap hap nhe han.

MOt qua trinh t6ng hqp ca ban bao g6m chc ID vi mite dO he th6ng di) hoc cilia cic to brio quadtree tuang Ong, mOt nhiin thbi gian, vri t6ng s6 dja diem xe mien phi. Nhu vuy, tang hqp diu ce cling kich thuOc, bit ke kich thuac cart khu vuc, n6 bao g6m vi s6 luqng cic xe tong khu Arc do. Do do, d6i van met mime de tap hap ngay cang tang vi do da gia tang khoang each dja ly tfr khu vuc duqc ma ti s6 Wong de lieu ten mOt earn diet' tich.

So sanh vi hqp nhit tap hqp cac t6ng hqp khu Arc. Trong phin then da de cop den biing cach s>Sr dung cac When th6i gian, ngubi to c6 the dl ding gift lig gia Ili man nhit duqc quan sit thiy d6i vai mOt so tham s6, loui b6 cfic phip do cil. Dieu nay 11 c6 the bei vi vier cup nil& the duqc so sank thin tren clic nhin th2ri gian. ThSit Ich8ng may, (lieu nay Itheng the duqc chuyin mOt citch don gian de gip hqp m8 tit nhieu hem mOt do la mOt may phat dien tang hqp - mOt chiec xe hod trong mpg thtrang tham s6. Ithang ce thong tin "hoar hao" (hoan chinh va duqc cep nhot day du) c6 san cho citc lin tong hqp. Nhu mOt vi du cu the, hay xem x& mOt ling dung ph6 bien thong tin ye tinh hinh nai dui xe. Gia sil rang ba ctic trang web au xe A, B, C niim trong met khu

Lriu oiNiti 2. truyen tnong tm trong mang V anet

Arc duqc tang hqp. Xe x biat rang tai A c6 10 (ha diim d#u xe mien phi tai then gian tl, vi tai theri gian t2 c6 15 dia diem d#u xe mien phi tai B. x kh8ng c6 thong tin vi C. Ting hqp duqc to ra beri chiic xe x se tat trong khu Arc c45 tang sa 25 dja diim biii d#u xe mien phi. Xe y cer nhiiu thong tin cfp nhig 6 B han x, vi biit duqc 19 dia diem xe mien phi tai mOt si diem trong thii gian dram nhat la t2. y cling biet khoing 13 dja diem d(tu xe mien phi tai C 6 then gian t3, nhung kheng biit bat cir diiu gi vi tang hqp curt A, vi c6 32 dirt diem d#u xe mien phi trong khu Arc. Gia sir bay gi6 ma met chiic xe thir ba z (tryc dip ho#c gian flip) nh(in duqc cac uan Mang ling t>7r ci hai x vi y. 1/#y mOt thong tin co lqi han nen gift lei? Re rang, cau trit lei cho caw hii nay icheng phai la dam grain, niu cer met cau tri 16i xac dinh 6 tat ci. Cac thong tin trong ark pan tang hqp lcha ching cheo, va Itheng xe nio trong sa d6 re rang chiim uu the khac.

TAY vt dy tren to they rang sy tang hap se khong tidal dien "hoin hio" cria tinh hinh hien tai trong khu Arc bao phi, nhung chi gin ding tat 'that li due tren nheng th8ng tin hien tai curt nut no ra. Neu ck nut khac nhau tao ra tong hqp cho cling mOt Ulu Arc, nheng tang hop nay thutmg se duqc dya tren cac thong tin 'chic nhau , vi mOt phlin th8ng tin bj ching cheo. Ck van di ca bin nay sinh la mOt nhan th6i gian duy flat Wrong thi the hien day di, OA da th6i gian cfia tang. met du tic dtt lieu m8 ti t#p hqp cac th8ng tin va citc nhan theri gian twang ling re rang ding khong phii la mOt lya chon, bed vi ni se can nhic nham myc dich tang hqp nhi, kich thuic se Ming niu dung luqng chin de lieu kheng tang.

ve van di tang hqp vi tap hqp cac ca chi gild guy& khac nhau nhung thong drying ca hai cii nay diu s* dyng cach ping down flan thii gian. Vi du, SOTIS s* dyng thbi gian cia thi he tang hqp nhu la mOt than then gian cho tang hqp,tuy nhien n6 Ong c6 the li met nut yeti thong tin ca vi kheng day di no ra mOt tong hqp, vi tang hqp nay sau di duqc xem nhu c#p nh$t nhiiu hen vi chic chin hen. Cac di an, tang hqp nhAn then gian cho cic TrafficView (ncri ma cac nhin thiti gian quan sat al What duqc sir dyng) va Caliskan he thing hying din a xe (tinh tofu' cac nhan then gian trung binh) cue cac thinh phan duqc sir dyng cho t#p hqp. Nhang tinh hang c6 the de ding xay dyng tang hqp yen pham vi bao phi Icha taint dien vi cap nhet duqc cap mOt nhan th6i gian lon han t#p hqp via met ca so thong tin yin.

Da c6 de xutit su dyng nheng dit lieu el* dien di khic phyc van de nay: bang cach km try cac quan sat trong caw tric xac suit tring 1#p de lieu nhay aim duqc goi li "soft-state sketches". Nan bin v8 tinh ci nghTa li thong tin da ci mtit 6 ca hai t#p hqp nguan se khan tic dOng tin kit qui Tr61ai vi dy tren, soft-state sketches khang can phai tra 16i cac caw hii "tong hai pan toting hop thi cai nio tat han", bed vi ni co the hop nil& t#p hqp cart x vi y thanh mOt va loai bi tring Tit hai t#p hqp nguen, c6 the tao ra met gip hop z, trong di ce thong tin ve A, B, va C. T6ng hqp sip

Ltiu uevu L. 1 ruyen tnong un trong mung v anet

niy sau d6 s8 ket hqp tit ci cic th8ng tin vi se dui din cho t6ng s6 10 + 19 + 13 = 42 nui xe mien phi.

Bing cich s(r dung ca the de, kheng cin so sitnh cic tap hqp lien quan: khong cin phi i loai b6 mOt trong nheng tap hqp, Uri vi nhung thong tin co trong ci hai tap hqp deu co the duqc luu gift, th8ng qua sip nhep bit cu nui nio NIA bit khi nio "thich hqp" trong mpg. 1Cheng cin mOt chiec xe c6 khi ruing thu thep diy du thong tin cho lin thu tilt) diu tier, me sau d6 phii tinh toin t6ng hqp, vi c6 the chi duqc cep nhet th8ng qua tinh toin hoin chinh. Thay vio de, tip hop c6 the kit hop thong tin mai cic th8ng s6 ben duei bit cir khi nio, trong khi cic xe dang di chuyin xung quanh mung•

Soft-state sketches dip tren ciu trfic dft lieu duqc de xuit boi Flajolet vi Martin , FM-sketches ban diu duqc thiet ke de uoc tinh s6 luqng cdc yeti t6 rieng biet trong mOt thiet lap theo thiii gian tuyen tinh. Vi chung duqc thiet ke phu hqp vhi cic ting dung VANET, do d6 c6 the duqc stl dung de thu th#p vi phan ph6i cic s6 do. Ngotli ra con cho phep mOt phin mtr rung c6 the to dOng log' be (soft-state) cic quan sit cU, neu ne khOng duqc hg trq cac pile') do men. Hun the ctla sketch dip tan nheng dtt lieu xic suit - drc la, no kheng luu trft gii tri chinh xic c6a cic thong s6, nhtmg n6 li xic suit xip xi. DO chinh xic curt soft state sketches c6 the duqc dieu chinh, stir trao ddi giim dO chinh xic d6i v6i kich thuoc t6ng hqp. Nei chung, met dui dien gin ding cfia cic phi!) do c6 ve hqp ly tong cic img dung VANET dien hinh. Phin mem soft- state titer rung cho vies loci be cic dft lieu ci ding c6 the cho kit qui trong kilt:411g thtri gian nhit dinh gifta mOt gii tri thay d6i vi thay d6i duqc phin inh trong cic tong hqp. Trong khoing thtri gian nay, tuy cOng met mire dO nhu ch#m trg gay ra boi trg do yen chuyin dft lieu qua mpg VANET, trong thuc to dieu nay kh6 c6 the trinh lch6i. Met vi du mo rung li lam the nio y Wong nay c6 the duqc sir dung de phan ph6i s6 diem a xe mien phi, n6 sa duqc de cep trong chuang ye cic Ong dung tier lqi VANET. 1Chii quit cic khii niem ve cic khu Arc tap hqp &Cr b#c trong Lochert. Cich tiep can dlra tren cay tir phan duqc dung tong Caliskan cho phip met each clg ding de giii guy& cic khu vuc vi he th6ng phan cip. Tuy nhien, n6 c6 nheng bun the khong xem xet topo colt thinh ph6 nim ben duoi: cling mOt trutmg tren cay ttr phan bao g6m cac khu vuc hiu nhu Icheng kit n6i trong mpg throng be, vi cic thuOc tinh chi yeti trong de c6 the khic nhau vi du, khu vuc hai ben cUa mOt con song hoar duong sit. Cic khu Arc Alp hqp nen thuc hien theo ciu trim lien kit ming duong be cc, ban, vi dua ra mOt ding thfrc chung cua mOt he th6ng philn cip tap hqp, cOng voi mOt s6 gqi y ye lam the nio de ne c6 the duqc that ke de cho phep ket hqp c6 hieu qtui dua ten sketch.

1,11.UUNU Z. truyen thong un trong mong V anet

d Clu trac kit hpp thdi gian di chuyin trong ntpng giao thong dig

Cac thuat town tap hqp duqcm8 to trong Caliskan va Lochert phuc vg tot trong cac biding hqp img dung doi hei tom tit theo vOng, tin la, mu8n khi co mOt cai nhln tong quan (t6ng cOng, trong binh, tOi da,..). Gia tri cOa mOt s6 tham so trong pham vi len hon. MOt he thong Wong din a xe ph6 hien tong so dja diem d6 xe man phi trong phom vi mOt khu vvc thvc so lit mOt vi du dien hinh cho (mg dung nhu vay. Titip theo se xem xet truing hqp thtri gian di chuyin trong mOt mong doing b0. NO giOp to hitt tong s6 die diem d8 xe man phi tren tit a cac con doing trong mOt phin cue thanh ph6 vi du, tong s6 thoi gian di chuyen doc theo tit ca cac tuyen doing nay, gia tri nay khOng truyin dot thong tin hen ich cho qua trinh lap ke hooch thong qua cac khu Arc cu the. VI vay, doi vii mOt he th6ng din doing phan cep mo rOng, viee due ra thOi gian di chuyen thong qua mOt mong &king b0 lit rit quan tong co the duqc doi dien mOt cach tong hqp phan cep th8 hon.

Trong Lochert xem xet mOt he thong ph6 hien thud gian di chuyen doe theo don doing nhu co So cho he thong dinh vi. De xuit viec sit dung phan cfp xip xi cua mong throng 130 vii Ichoang cach ngay ming tang. Thlti gian di chuyin doc theo cac doing lien kit Oa tit ca cac nut giao thong tai (ha phuong duqc quan sat, va &roc trap d6i trong yang Wm can. Cac nut quan trong sau d6 duqc se dung nhu "tip hqp diem m6c", ye mOt mpg duong b0 xip xi duqc xily dung, trong d6 bao g6m cac diem mOc va mOt tap hop cac lien kit ao gifts chting. Chi c6 diem trung tam va cac kit nOi tr‘lu tuong gitta chung duqcxem xet. DO la, mpg lir& &Ong gin dung theo mOt nghia nao d6 gib') don gian ciu trtic lien kb., bing cach rbi khei doing ph6 nho hon va cac nut giao va tong hqp thong tin thtti gian di chuyen tren tit ca cac tuyin co the co gitta cac cap m6c. Trong hinh 2 7, vi du nhftng 8 t8 se duqc sung cap nhOng thong tin chi tiet ve thtri gian di loi gitta tit ca cac diem m6c (doi dien bbi cac Ong ton), tang lchi xe di qua mOt diem m6c nhit dinh chi biet ring thoi gian di loi ngin nhit co the co gitta nheng diem m6c " Tour Eiffel "va" Arc de Triomphe" la 70s. Trau tocyng trong tv cue mong dtrong hi) cOng duqc sit dung trong mOt s6 thuat town hien doi de nhanh cheng xac djnh con throng ngin nhit thong qua mong hen giao thong &tong b0.

uriu UM' Z. 1 ruyen tnong tm trong mpg v anet

Hinh 2.7 MX gian di Tour Eiffel din Arc de Triomphe.

Trong cac de an dirge di 'cat, tap hqp la thai gian di chuyen dqc theo nhung lien kit io gift cac diem moc. Trong topo lien ket dieing bO, ce the c6 nhieu tuyen du6ng n6i hai diem moc hti yeti nhau bang mOt lien kit ito. Gia tri tong hqp chit yen chi nei ring no c6 the lai xe tir moc A den moc B tong Yong vai gily. De tinh tote gia tri tong hqp cua mOt chiec xe sit dung cac thong tin quy m6 nh6 dia phuong ve dm% gian di het dogn du6ng de tinh Man thlri gian di tar A den B la nein nhit. Diem min chot 6 day khong phai la nir ph6 bien doting di ngin nit& hay diet th6i gian di chuyin tren tang dogn (fitting khic nhau ma dm hitt cai xe d6 6 khoang each lan. Nhitng diem moc trtlu tuqng ya th6i gian di chuyen giita chung la du cho quy hogch tuyen doting. Bei vi thong tin chi fiat ham nhu xe din gin han y6i khu Arc tuong ung, yi sau de ce the Vic dinh chinh xac duong thqc stir cho phi') di ttY A den B trong thei gian nhit.

Citc Ichai niam gin giOng nhau dugs lip dung tren cip bac cao han dal diet' cho mgng lueri giao thong 6 nhung khoing cich 16n hon. Cling giong nhu mOt tap hqp con cata khu Arc giao cat dirge bieu thi nhu cac diem moc clip mOt, mOt tap hqp con c6a diem moc clip mOt d8ng thoi cling la mOt caot moc cip thin hai. Diem moc cap cao dang kit not thong qua lien kit ito voi cap cao han, to thanh ming lueri giao thong xip xi yai mire dO ha thong phan cap nay cling tang. Hinh 2.8 cho dac diem nay: chiec xe 6 Ming tam caa hinh ce thong tin chi tiet ye citc dogn doting rieng le trong Yong ton ben trong. D6i Yeti nhang yung xa han hen bin d6, thong tin co ban trong cac hinh thtic lien kit Ito gitta cac moc cao han duqc sir dung.

uttu °Diu 2. i ruyen tnong tm trong mpg v anet

Hinh 2.8 Mek mgng hteri &rang phan ccip trizu tugng.

Then gian di chuyin doc theo lien kit io cep cao han tao thanh nhttng t6p hop cep cao twang ting, duqc tinh tfr thbi gian di chuyin doc theo cic lien kit io cua cic cep flip theo the') km, vi mOt len ntta dpi dien cho thbi gian di chuyen dcc theo duong din twang (mg nen nat. Do li, thbi gian di chuyin dcc theo do?n &rang chrqc sb clang de tinh toin thbi gian di chuyin gitta cic diem m6c tren mirc phan cep du tien, Mang lien ket io deu lien phac vu nhu li ca sb cho viec tinh tam thbi gian di chuyen gitta cic diem moc ctia he thong phan cep titer hai.

2.6. 'CET LU4N

Trong chuong de dua ra drx diem tit* &Ong cult cic bng clang den lqi tong VANET. Ling dung nay doi hed phai dugc phan b6 tong mOt yang rung 16n hon. Khio sit cic ngu6n tin Ichic nhau vi xem xet lam the a° de lieu c6 the duqc thu ngay tb du. Sau d6 xem xit cic giao thirc ph6 bien vi cic thu6t toin, cung cep phtrang tien di truyin &it lieu ter diem nguton den khu Arc cila mi c6 yeu ceu vi huu ich.

Cu6i cAng se Wong den ca chi t6ng hqp vi t6p hqp dit lieu. Nhieu quan sit c6 the duqc kit hqp thanh dpi dien nho haft, vi cich tong hqp clit lieu c6 the duqc duy trl vi cep nh.t, hqp tic vai nhau trong mpg. Bed nhung d6c diem hp the c6 httu ctia mang kitting diy da hex, d6c biet ye Ichi ring, ca chi, thl d6 li nun tan cho cic img dtmg ph6 been VANET.

CHUONG 3. NHONG UNG DIJNG COA VANET

CHIrCING 3. NH'fiNG ONG DVNG CUA VANET

3.1. GI61 THEP

Cic img dung thuan tien ci the chimg minh lit mOt khi ning quan trung cUa deg nghe VANET. Cic img dung lien quan den an toin, ching hon nhu cinh bio giao diem yeu ciu chic nting duqc chuin boa de c6 the sir dung. MOt img duns huing din mOt ngutri lai xe den nui d8 xe pha hqp hoc trinh an tic gam thong, nginX 10, nit huu dung de cic nha sin xuit dic the vi cung cep mOt lqi the khic big so vii cic nha sin xuit khic. Day la mOt dung luc rat mph de diu to vio cic img dung VANET Ichang lien quan den an tan.

Dtong thtri cic (mg dung thuan tier yeu ciu xem xet rat can thgt khi guy& dinh lieu ci thich hqp de lip dg trong truyen th8ng truc tier) gifts cic xe. Ba 1ST do chinh de truyen thong truc tiep ci the khong li mOt su Ixra chun t6i uu cho mOt (mg dung nhit djnh: KM Wing hon the caa mpg, su thieu kit noi, vi cuei cUng, su hien dien cUa dog nghe conh tranh nhu cic mong di dOng.

MOt mg la su ttrong phin gitta cic hon chi co bin caa cic img dung gen lqi va su thinh ceng trong cung cap cic img dung. Trong phin nay g neu nhttng hon chi co bin trong phit tan img dung VANET. Tiep theo li cal thin tong quan ve cic ting dung khOng an Wan di duqc de xuit cho VANET. Sau de se lin luqt de c#p den he thong th8ng tin giao thong hqp tic (TIS) nhu la mOt 16p d#c big ph6 hien cic img dung tong VANET. Cic he thong nay thu tIgip nhing quan sit caa ci nhan xe tinh hal giao th8ng hien tai vi sau d6 plan phei chimg cho nguei them gia khic trong mong, nui ma thuing duqc sir dung cho quy hooch tuyen throng. Thich thirc chU yeu trong 16p cic img dung nay la mOt s6 luqng lin cic th8ng tin duqc phan phei tii nhieu ngutri nhfin rieng big. C6 ba cich khic nhau: giai phtip sfr dung mOt miy chd trung tam ket not thong qua mOt mong di dung, stl dung ct5ng nghe ngang hang tren mong di dOng, vi mOt citch tiep c. n dua tren VANET.

Sau khi da neu ra nhttng uu vi nhuqc diem cfia m8i phuung phip tiep con, se dua ra cic giii phip dua tren VANET, vi hien thj gip hqp tit lieu nhu duqc thio luan trong chuong tren dtt lieu ph6 bien c6 the duqc sti dung de 'chic phuc vin de cot 18i la khi Wing cUa mong.

3.2. HO CHI

Khi phit Wen mOt tang dung trong VANET quan trqng li nhan &tic duqc nhing hon the trong m8i trutmg nay. Nhttng thich thirc chinh la hon che khi fling, kit not giOi hen, vi deg nghe thay the cash tranh. Trong phin nay se m8 ti chi tilt nhttng thich thirc vi cung cap gqi y de lam the nip c6 the vtrqt qua nhang hon che. Trqng tam cUa phin nay la nhttng hon the cult giao tiep xe veri xe.

CHUONG 3. NHONG I:JNG D1)NG CI:JA VANET

3.2.1. %hi ning

Trong bii bao mang tinh bark ngo#t cia Gupta vi Kumar di chi ra ring dung luqng truyen cia met nut trong mpg kh8ng day da buerc hOi to tai 0 nhung s6 luqng cac nut trong mpg gia tang. VANET la mOt mgng khang day da buerc, nem hgn chi cu bim nhit ma cac nha phut Win phai dai mkt veri cac ing dung khong an toen lien quan den kha Hang hgn chi cia mgng.

Th#t Idiong may, ciu frac lien kit eta VANET lei ci the khuech dgi nheng hgn chi khit fling. Vin di quan trcong la, trong VANET cac nut khong duqc phan b6 diu tren met dien tich hai chat', ching bj hgn chi phai di chuyen dpc theo mOt dubng. Xem xit nhttng trubng hqp diem hinh la tren mOt dubng cao tic, nai met ban tin duqc truyin ti met ngubi gbi den ngutri nhin. Tren dirtmg cao tic nil chung thi chieu rung bi him the nen bit ki dubng truyin kh6ng day nao cling bao phi toil' be chieu rung cia ni. Vi 4y, truyin th8ng diep tb ben gfri den ben nitifin tren thuc to thong tin xe tan ng$p tren tan be dubng cao tic gitta hai xe cho di dit sir dung thu#t town djnh tuOn th8ng minh vi hieu qua.

Tit ca cac xe nh#n duqc cung met bang thing cho truyen du lieu de c6 the nh#n nheng th8ng tin ma hp chpn. Truyin bit ki nhu v$y se la gbh n#ng cho ngu&i nhin va ngutri S6 luqng ngiy cling tang nhu m#t de trung binh cia xe vai khoing each tning blnh gitta ben nhin vi ben gii. Ket qui la, sau khi xem xet thi dun elm de thiy ring 'chi Hang ci sin cho nt8i ben gin se giam cheng lgi su can di nguqc tS, le giea m#t dO trung binh cia xe vi Ichoimg each gift vies gui vi nliftn ban tin.

C6 nhieu each de ded ph6 vOi hgn chi khi Wing cia VANET. Cach tiep c#n din gifin nhit a chic chin la cic hing se duqc ltra chpn nhu 4y ma cong suit ciut mpg kliong vugt qua melt ting dung nhit dinh. VI du cac img dung thiet ke chi yeu ceu met tic de de lieu nho tren mOt khoang each tuung dei ngin. Ho#c c6 the nhim muc dick cii thien t6c de dtt lieu mOt busk duy Whit de phi hqp v6i yeu ciu thong tin lien lgc cua (mg dung.

MOt each tinh vi hun de di phi vol hpn chi ye kha Wing trong VANET la thiet ke cic (mg dung sao cho cluing tro thinh van of) khi fling mer Ong trong med trutmg nay. Met each tiip c#n thubng duqc sCr dung xuit ph& ter Grossglauser vi nal ma sq di chuyin cia cic nut tham gia duqc sir dung de ring cao kha nang cia mpg. Thong tin (mg dung lien quan den VANET, ching hen nhu thong bao the nghen datmg bt) can phai duqc truyen cho cac xe 8 to b phia sau, ngutri gill dun gib la ci the twin thong diep tOi xe b huOng nguqc lgi. Chiec xe nay se thrc hien tin nhin cho den khi nb ci the ducrc giri true tiep den ngutri nh#n du dinh. Cach nay c6 the lam giim kha fling hgui chi cia mpg.

CHYONG 3. NHC/NG UNG D1JNG CUA VANET

MOt cach Ichic di loci be mat dO clia ngtrei gui tir kha nAng hen che. DOi vdi nhiAu Ong dung ctia VANET lien quan din vies tniyen de lieu khOng phii cu thi c#p ngueri gai-nh#n. Cac de lieu ching hon nhu firth hinh On tic hien tai hoc s6 luqng ctia khong gian xe mien phi c6 ich cho nhiiu loci xe. VI v#y, khong can cho tit ca ck xe bao cao ve met phin dui thong tin. CM can mOt trong nhang dpi dien phat di mOt thong diep d6i v6i nhihig khu vqc nth ma cac th8ng tin cel thi hftu ich. Nhu dii neu trong chuong ph6 hien de lieu, dieu nay c6 thi duqc kit hop yeti mOt phuang phap t6ng hqp. MOt phucmg phi') nhu vy c6 thi loci be nheng yin di ye khoang cach ngoli ra d cc vin de met dO, mem deo diy de khl Wing met reng cac Ong dung VANET.

3.2.2. Kit not

Thach thirc quan trang thti hai cac Ong dung VANET khong an town phai d6i met la han chi khl Wing kit n6i ctla mpg. Meng Wei duqc hinh thimh bed thong tin lien lac trqc tiep eta xe 8 to bao g6m nhieu cum khOng duqc kit n6i veri nhau tai bit kk diim nao theo thei gian. CO hai lk do din din dieu nay, diu tien la mat dO hien khai ban diu ctia cOng nghe VANET se o =lc thip tong mOt thbi gian dal sau khi chikc xe diu tien duqc trang bj. MOt nghien ciru bbd Matheus ngay ca khi tit ca cac xe tang trung luu ter len duqc trang bj c8ng nghe VANET, ne se mit ba nAm de do duqc 10% thAm nh#p thj truong va khoing 16 am di dot duqc 45%.

Lk do tit* hai tai sao mpg gifts cac xe philn veng cao thi kha hinh thinh mOt chuSi lien tic ck xe trong pham vi sting vo tuyin giam theo dip s6 nhan. Lochert gill thich chi hit va c6 ngu6n gtm dung dii vdi sq hinh thanh chu8i. Ifmh 3 1 cho thiy xac suit cua kit n6i khOng bj gian don, ttly thuOc vac s6 luqng xe duqc trang bj trong m8i phi= vi song v8 tuyin (p) va khoang cach bao phti Dieu quan trong la nh#n ra dAy la met uac luqng kha quan, bdri cac m8 hinh phan tich gib djnh la cac xe claw phan ph6i d6ng nhit tren dulmg. Trong tlArc ti, cac xe c6 xu hueng hinh thanh ck cum, s8 lam giam Itha Whig cult str hinh thanh chu8i.

Kha nAng kit n6i hp chi c6 the mong dqi tir VANET, hiu het cac Ong ding an town duqc de xuit ho(ic thra vac cac truyen thong cic b0 (vi di nhu tit ca cdc Ong dung lien quan din an town) hok stl ding cac xe di dOng di thu hep khoeng cach kit n6i. Chuyen giao de lieu din luu luqng diu vao ho#c don gian chi can mang theo cac tilt lieu trong mOt thbi gian khong chi lam giam yeu ciu ciia Ong dung mi con cho phap ph6 biin d2 lieu ngoai mOt phin veng ctia VANET.

CHLIONG 3. NHUNG ONG DUNG CUA VANET

1

0.8 10.6 1 0.4 A

0.2

................................

. (cid:9)

.. „ .........

•

• (cid:9)

0 5 10 15 20 25 30 35 40 45 50

DO diiciaphikemitimpbisooe

Hinh 3.1 MOt xdc suit cita kit not vo tuyin

quan trong

Hinh 3.2 (a) cho thiy dO tu6i trung binh eta cac thong tin co sin trong mOt chitc xe nhu mOt chirc Wing curt khoang cach tfr cac ngu6n thong tin. C6 the thiy ring dO tint phat hien xip xi tuyen tinh theo khoing cach. T6c dO truyen tang len clang ke yeti mOt dO thiet bj ngay citing tang. Dieu nay la bei xic suit cart skr hinh thish chit& diti tang vii mftt dO thiet bj nay cling tang, ce nghia lit vin chuyen du lieu thong qua truyen th8ng kheng day ngay cling trO nen chi& uu the, trong khi (cid:9) giao thong vOn tai thong qua chuyen dung gam.

Tai nai mOt dO thiet bj thip, thin gian trung binh cho viec ph6 Bien thong tin cho cac khu vuc ben ngotli c6 the dot duqc mOt gik tri cao tai 400s. Tuy nhien, met dO thiet bj thip ce anh htrong thOm chi can nghiem tang ham vao khit fling c6a mOt chi& xe biet bit cu dieu gi ve ngu6n g6c &I lieu. Th6ng ke, sau 500s mkt thOi gian m8 phOng, duqc ma tit trong Hinh 3.2 (b), 'Lac suit de c6 thrac thong tin tui mOt khoAng cach ngtly cling tang gitun xu6ng nhanh chang. LS, do chinh curt tinh trung nity lit phiti mit mOt khoing th6i gian de mOt chiec xe bit diu chuyen di tir mOt khu vuc din cu, mOt bai xe..., cho den khi n6 gap mOt chiec xe khac ma ttl d6 n6 co the ce &Km thong tin. T6 nheng kit quit, c6 the thiy ring mOt dO thiet bj cao la cAin thiet di ph6 bkin thong tin du tin 4y. Kit quit, giai clop trier khai trong mOt (mg dung VANET, nai ma mot dO thiet bj c6 sin thip, la mOt vin di kh6.

CHUONG 3. NHONG ONG D1,JNG CUA VANET

0'0'0* 41,

.40 41.441"ara 11 akarA.A. a a A.A.& 2.

1000 2000 3000 4000 5000 6000

6 el**

a)Tu6i trung binh ciia thong tin

0 0 1000 2000 3000 4000 5000 6000

ICboing akb(s)

(b)Phlin nhe Oa thong tin ve xc

IBM 3.2 Phd hien de lieu being cdch sri dung citc chuifi va xe di deng.

De 118 trq cu the then khai giai door', no dit duqc de xuait d cai dot mOt se luang nhe cac darn vj ben le thrZ ► g (RSU) tai nit giao thong duimg bO quan trung. Nhthig RSU thaw gia vito mang vi tAt ca kit ntoi vai nhau bai mOt mpg luoi du mg truc, do do chia sb mOt nen tang kiln thirc ph6 Wen chung vi ce the litm cAu khoing cdch lan. Anh huong cia vier sir dung bay RSU ket nei vei nhau trong kich bin m8 ti 6 ten co the duqc the hiOn tong hbah 3 3

48 CHUONG 3. NHUNG UNG DI NG CUA VANET

500 i 400 1 300 f 1 200 I 1 100

"...... ***VOVI • 004* 411**.ef. 1)0'4 A44.4tA14 4 illA•arit A !tit& it 4

•Ar nn•4n-n ••-.6.4-&-a••••••"&••••

1000 2000 3000 4000 5000 6000

Khaki &Xis)

(a)Tuei trung binh cia thong tin

1 wail qt:, Is

0.8 • (cid:9)

a II 0.8

1 i 0.4

1 02

0.75x

025 at —*— - - -s- — 0.5 ist - — a- — --a-

1.02st

1000 2000 3000 4000 5000 8000

o o

Moine aidiss)

(b)Phan nh6 cia th8ng tin ye xe

Hinh 3.3 iinh huom ctia cetc dun vi ben a duang

BM h9c duqc * nhitng thi nghiEm nay la ngay ca mOt s6 hrqng ttsong d6i nhe ciut cc: so ha ling b6 sung ce the de dot duqc chi thin ding ke. Tuy Whim, su chum tri vi mOt phin ding ch6 Sr la chic xe khong c6 diy •thi thong tin, vi viy, ay thuOc vao dtic diem cua (mg dung, ket noi yin con la mOt vin de quan tong via RSU.

3.2.3. Cfnh trunk

Giao flip truc tiep giita xe phai di mOt yeti su cash tranh mph me to truyen thong di dung hiEn tai vi Wong lai. Vi du, hE thong 3G dit cung cAp truy cOp Internet di dung gii ca phai chling vI ph6 Men rung raj. D6 la ho ljr de gii djnh ring chi phi truy Op Internet thip di dung sE sem duqc 06 hien truck khi cong nghE VANET tro thinh mOt thqc ti. Uu diem chinh cia truyin thong di dung la chi co mOt buoc nhAy Wong day. MOt khi cic d0 lieu den cic hE thong co so cia mOt man di dung, khOng phai kha 'ling \fa cOng khOng htm che kit not neu phic thio ten duqc ip dung. Dieu

49

CHUONG 3. NHUNG ONG D1,JNG COA VANET

nay la d(tc biet quan tong neu th8ng tin lien loc tren mat khoitng citch dirt ly dIi. Hon nee, cic mong di dung da tun toi trong khi ding nghe VANET c6 the kbong c6 sin trong nhieu nam ten. VI vb, mOt s6 luqng lan cic img dung dal hei th'6'ng tin lien lac giita mOt chi& xe va Internet ho#c gifts hai chiec xe cu the 11 khi Wing sir dung mpg di dung.

Kit khic, citch giao tiep eta VANET phi hqp von trao dui kh6i hrqng de lieu cuc bO nhanh va cao. N6 chi don giim la nhanh hen va hieu qui hon de trao dai de lieu gift hai chi& xe trong phom vi sting v8 tuyen trqc tiep hon lit sir dung thong qua mOt mong di dOng. Ngoiti ra, c6 nheng (mg dung, chang hon nhu mat he thong thong tin giao thong, not de lieu duqc quan tam nhieu hotic them chi tat ca cic xe tang yang lin c# ► cira xe truyen. Dieu nay ceng la mOt tInh huang trqc tie') giao tie') gilIa xe c6 the c6 lqi the hon cic mpg di dung, bed vl cic thuac tinh wing bi cic bO cala truyiln Ichteg day c6 the duqc khai thic. Cu6i thong tin lien loc VANET van main phi, lam cho ne hip din dal v6i bat img dung nio, neu c6 the d6i phe vai hon chi kha

Wing vi kit n6i.

3.3. I'.TNG DUNG

Y twang de trao dai th8ng tin gitta cic xe di lam tang cic de xuat cho cic (mg dung. Trong phim nay, se lam nai b#t mOt sa 16p img dung thu6ng xuyea de cep khi thio lu#n ve VANET thufm tien vi ling dung hieu qui.

Mat trong cic img dung dau tien duqc de xuat cho phuong tien giao tiep vai Intemet.Trong mOt s6 dq in VANET duqc coi la mat phin m6 rang di dOng cue Internet. Doyen de lieu gifts xe sau da se duqc mat rich Wong tu nhu (firth tuyen cic goi tin tren mong Internet vOi cic phuong tien 11 tuong ducmg voi bO djnh tuyen Internet. Vai hon chi ve khi Wing neu tren, quan diem truy cep Internet di they dai khi nhieu. Hien nay VANET duqc coi la c6 the m6 rang phm vi cite cic diem truy cup khong day duqc dot sang v8 tuyen. Lai xe sau de c6 the duqc cap ket n6i Internet trong mOt thtri gian dai hon so Wei kit n6i trqc tie!) vai mOt he th6ng. Thong thutmg, kit n6i se duqc cung cap mien phi vi dai lei cic chu ser httu cue cic diem truy cep se nigin duqc mOt s6 lqi ich ye met tii chinh. Vi du, c6 the di gluing cao cho gii khi dat ho#c cic sin pham Ichic. MOt dich vu c6 the duqc quan tam cho cic img dtmg doi hOi phai c6 ket n6i Internet lien tuc. MOt vi du c6 the day monh truy cep thu dien tir. Tuy nhien, trong bat ky tru6ng hqp nio man phi truy cup Internet lien tuc se phii cash trash vai cic dich vu ding tin coy cung cap th8ng qua mong di (tang. Djch vu c6 the rat r8 trong tucmg lai gin.

MOt 16p img dung lien quan den truy cep Internet la phan phoi pang bi bang cic phuong tien truyen thong gift cic xe. Vi du, Lee de xuat mat he thong not ma cic

CHYONG 3. NHaNG UNG DUNG CUA VANET

phucrng lien nhan duqc mOt thec diy co the bito ve vi thuc hien quart ba trong mOt inking VANET.

Nhu m8 Ilinh mieu to 6 tren thi truy cap Internet thtdmg man phi nhtmg n6 duqc IA hop vei mOt s6 hinh thirc quing ba phan tan. Ke ti'r khi quing ba pilau tan lit giao tiep don buck cite yeti Icheng bj can to bei kha Wing ho#c cac yin de ket n6i.

Mong mu6n c6 duqc mOt diem den nhanh nhlit c6 the trong khi tieu thu ngu6n tai nguyen t6i thieu di duqc nghien ciao tren VANET dtra tren th6ng thong tin giao thong (TIS) nai "thong tin giao thong" nei chung c6 the duqc hieu theo nghia rung.

tueng c6t 18i cola cac img dung nay 11 se dung cac phuang tags nhu cac cam bien dies thoai di dOng theo d8i cac thong s6 nhu mat de giao thong, dtrImg b0 vi eau kien thei tiet, ho#c thong tin ye Ichang gian dd xe bj chiem dung. Thong tin sau de duqc phan ph6i cho cac xe kink, nai n6 c6 the duqc se dung cho cac muc dich nhu t6i uu hea tuyen doing ho#c thich nghi cac hanh vi lai xe. VANET dua tren ltru luqng truy cap h th6ng thong tin di nhan duqc nit nhieu su chit tong nhang nam dm day. Han naa, de la mOt vi du tuyet von cho mOt ling dung diy the thich dOi voi nhtkng hen chi neu tren: mOt kh6i luqng 16n dtt lieu V Ong thay d6i duqc truyen di bing xe tren mOt khoang cach diti. D6ng thei, cac mang di dung la mOt d6i this canh tranh mash me yeti VANET de phan ph6i theng tin lien quan den giao thong. Trong phi!' con lai cola chucmg nay, se xem xet ky han tai cac h th6ng thong tin giao thong. Mix tieu la sir dung chung nhu mOt vi du cho cac quyet djnh vi qua trinh that Ice cac fing dung tien lqi VANET. Bit diu bang cach dieu tra chop thay the thiet ke tiem nang, d#c biet lien quan den vies se dung cac mpg di dOng. Sau thao Juan nay se tip trung vio nhang thich thec khi Wing de phan ph6i thong tin ye firth hinh giao thong hien tai vi firth With iii d8 xe bj chi& dung trong VANET.

3.4. BIEN HOA TRUYEN THONG

Nhttng hart chi c6 hitu curt thong tin lien lac VANET, mat de Unit bj VANET ban du bj glen hap, vi earth tranh vei cac he th6ng truyen thong di dOng nhin mph rang VANET kitting phiti la duy nhit. Khi chting ta nghl ye cac ang dung thuan lien xe, thi chang ta lute Ithan thio Wan ye nheng lqi ich vi han the cola nhing me hInh truyen thong Ichic nhau trong chi at nhieu han mOt chat. Trong pluin nay, xem xet cic tinting hqp cu the cola mOt he th6ng thong tin giao thong (TIS) tap trung vio ting dung cu the nay, se Wong phis VANET- dip tren thong tin lien lac vOl hai phuang phi') tiep cOn co se ha tang 116 trq: cach don gian xay dung nhu la mOt m8 hinh Ichich/che, vi each flip 4n ngang hang nai nhang chi& xe tao thinh mOt mang luoi thong qua truyin thong di dung.

CHISONG 3. MOM LJNG DUNG CI:JA VANET

3.4.1. Hf thong gip trung khach chu

V* sit dung mpg thong tin di dung lam earn cac van de thuc hien mOt he th6ng thong tin giao thong tri loi cho cau hei lam the nio de lam cho de lieu tap hqp chung cho tat ca cac ben quan tam. MOt each di (1st duqc dieu nay la stY dung mOt kien true khichichli. Trong phucrng phi') nay, mOt may chit (hoac mOt tap hop may chfi) ten Internet cac luu trft mOt co sli tri fink trung tam bao g8m tit ca de de lieu &I duqc hqp tic thu thep vi deng g6p curt nheng chi& xe. 8 to quan sat, vi du nhu, ve tinh hinh giao thong hien tai, trong khi lei xe. Nheng quan sat nay duqc girl true tiep den may chli.

MOt chick xe sau d6 c6 the yeu cau thong tin nay. D6i vlii muc dich xac dinh t6t nhat curt nhieu tuyen duling thay the al v6i mOt s6 diem den, thong tin tren cic be phOn quan tong clia mpg lulii dutmg bt) la can thiet. De thuc hien nhient vu nay hai each tiep c#n c6 the hieu duct: (i) Cie xe tai ve (vi thuling xuyen cep nh#t) de lieu luu thong cho tat ca cac tuyen dtrtmg ce the thay the. Sau d6 n6 c6 the tinh town con dtrling nhanh nhat den dich dra tren thong tin giao thong hien tai. (ii) Khi tai dlii hOi mOt ng luc truyen thong cao, viec tinh town tuyen du?mg Wan phien c6 the duqc thIrc hien bbd may cha. Dieu nay, dOi hOi ngu6n hrc dang Ice tinh tan tong mOlt vj tri trung tem.

Khi sil dung mOt lden frac khich/chli k& hqp von mOt each tier' can truyen thong dua tren ca so ho tang ting dung TIS c6 the tranh cic van de 16p mpg thuling phit sinh trong VANET. Lqi the ion nhat clia thong tin lien lsc dua tren co se hs bin la tren dive to ring mat dO cua nhitng chiec xe duqc tang bj can thiet cho (mg dung host dung la nh6 hon nhieu so yeti trilling hqp cart VANET.

Thich thirc ky thu#t chtl yeti mkt hO thong tap trung de del pho voi s6 hum lan cac ban cap nhat d8ng thtri vit cac truy van, duqc chi ra bbd Hull, Rybicke in& chi& xe la mOt ngu6n cue cac truy yin vi throng xuyen gud cac phep do curt rieng no. Hon nila, do mtic dO tap trung cao, may chli ce the trli thanh mOt nut that et', chai hoac them chi mOt diem duy nhat cart that bsi. Tuy nhien, ly do chinh kheong su dung mOt he thong tap trung de quan ly thong tin giao thong c6 the lit phi k5 thu#t: n6 chi don gian la kitting mong muon chi ce mOt trung tam quail IS, der lieu, ce Ichit tang se hsn the guy& truy cep vito d2 lieu thu tilt) clia tat ca nguii them gia giao thong.

3.4.2. Ma hinh ngang hang

De tranh nhung hsn chi dui m8 hinh Ichitch/chu giai phi') Rybicki di chi ra lam the nito co so hs tang truyen thong di dOng c6 the duqc thfic day de xiy dung mOt mpg ngang hang phan phoi cho cac he th6ng thong tin giao thong. Cach tiep can nay kit kip mph me kit qua tfr phan cap quan 15, vi tinh dOc lap cue met co quan trtmg

CHLYONG 3. NHUNG LNG DUNG CUA VANET

tam mat khac voi kit n6i duqc cung cap bei co se ha tang truyen th6'ng doa tren cac each khac.

Trong he thong nhu vay, m6i chiec xe tham gia la mOt thiet bj ngang hang. Truy cap de lieu giao dies ctia may chill duqc May the bing mOt bang barn phin ph6i (DHT). DHT lien kit cac kh6a yen cac gia tri. DOi vol he tilting thong tin giao thong, ngtrei to c6 the se ding cac tort dO dia IS, nhu la khea vi cac quan sat tuang fmg nhu cac gia tri. M8i thiet bj ngang hang nhu vay, chju Mich nhiem cho mOt tap hop co the cac kb% vi do, dutmg ph6 vi cac de lieu lien quan. Lap ban d6 r8 rang cala cac kh6a yeti cac thiet bj ngang hang duqc thoc hien bing qua mOt ham bam ngiu nhien va d6ng nhit. Phin chinh ctia DHT 11 viec thoc hien thuat town tim kiem theo kieu phin cep. D6i vol mOt kh6a nao do, tra cfru tra ye mOt that bj ngang hang c6 trach nhiem. Dieu nay duqc thoc hien theo each sau. Nheng ngutri tham gia to thanh mOt mpg lutri bao pile, nth ma m6i thiet bj ngring hang kit n6i yeti mOt s6 thiet bj lan can nhu mOt ciu true duqc Nit ke can than Hoac la Wet bj ngang hang se Mu mOt kh6a cho n6 biet mOt thiet bj ngang hang cung cap mOt lien rrinh huong eh mOt trong nheng etch

nhiem bao phe.

Trong hlnh 3 4, cac kjch ban duqc duqc chia thanh nhieu lTnh voc Ara duqc gin mOt ID duy nhit duqc sir don nhu la kh6a. Trong vi du nay, DHT Chord Stoica duqc sir don nhu cac giao thee tra cum. Trong Chord, ci hai thiet bj ngang hang vi cac kh6a dupe barn mOt dinh danh. Nhitng ID Chord nay tito thanh mOt ciu true Ong. Mai thiet bj ngang hang ce mOt lien ket de Ice thtra true tier, ter n6 (cac fillet bi ngang hang yeti cac ID Chord cao han Ice tiep). Cac Ichea cfing duqc barn vi duqc luu tr( tren phin ter tiep theo. Vi do, khu voc 16 duqc bam cung ID chord 14. VI vay, ngang hang voi cung ID Chord 35 (Ice thea cila cung ID Chord 14) chiu trach nhiem cho cac clit lieu lien quan den khu voc 16.

De tim they mOt thiet bj ngang hang chiu Mich nhiem cho mOt kh6a Qua ra di girl mOt truy yin tim kiem doc theo veng. Bing cacti thong qua cac nut bin can, cu6i cling n6 se dot duqc den dich mkt minh De thoc hien truy van hieu qua han, mOi that bj ngang hang duy tri mOt bang chi duong kilt' finger voi nheng finger chi cho cac xe kirk Wet it nhit 2i ID WA i new cling tang. V& phin me rOng nay, so phfrc tap cat' vi trf cac thiet bj ngang hang chju trach nhiem tro thanh legarit trong s6 nheng ngtrei tham gia man.

Cac that bj ngang hang c6 the tham gia vi raj kh6i mpg mOt each to do. Sau khi tham gia, nheng ngutri tham gia mai chiu each nhiem cho mOt s6 tap hop cac kh6a, giam kh6i loong c,8ng viec trong binh trong mang. Khi rei khoi, cac cap ngang hang chuyin giao de lieu tim tre cho cac cap ngang hang khac.

CHLTONG 3. NHUNG LJNG D!,JNG CUA VANET

Hinh 3.4 Phan phoi cac that bj ngang hang wen moi phcin cloan dining

De sir dung he th6ng mu% ngang hang lam co s6 cho img dung TIS, ngutti tham gia giri cac quan sat cua ho cho cac thiet bj ngang hang chju trach nhiem. Qua d6, thong tin dirge tao truy cop vat) tit ca cac trinh dieu khien kink. De c6 duce thong tin ve dieu kiln giao thong hien tai tren mOt tuyen duting theo ke hooch, img dung thuc hien mOt s6 tra ciru. D6i v6i m8i phan (loan cua tuyen &Ong ngang hang chju trach nhiem Qin phiti duqc tim they va truy yin dtt lieu. Do vier phi!' b6 ngiu nhien cac Ichte biim, mOt m8 hinh sir dung dien hinh lien quan den cac truy yin cho cac phan doan Uhl can tao thanh mOt tuyen du6ng. Rybicki de mutt mOt gill phi') c6 the nham muc dick de di ph6 voi vim de nay. Neu quan sat cua tit ea the phan down cua tuyen throng duqc luu tit nhau trong h¢ th6ng, s6 hrqng tra ciru dOc 14p ce the duqc Om. Be Meng lam don hai den du true Chord, mOt bang finger th(r hai bao gem net nghTa cua cac finger ce the duqc s6 dung. Nhu diem finger 6 cac thiet bj ngang hang chju trach nhiem cho cac phan down dutmg Ian con voi nhang ngutri duqc luu tit tai nhfing ngutii tham gia. (nhu la cac diem finger chju trach nhiem ye phan dap dir6ng lien ke v6i nhttng ngirtri duqc luu tham) Do d6 nut yeu au se chi phai tim mOt thiet bj ngang hang chju trach nhiem dei voi phan down diu tien cfia down throng ke hoach va sau d6 "theo" cac tuyen Ming trong ciiu ink ngang hang ma kung thuc hien tra cuu them trong mOt nghia nio do, mpg lutd dirteng bO duqc phial anh trong

cau true bao phd.

MOt thich th(rc trong cac mang ngang hang 11 dam bio can bing tai. Dieu nay cang tr6 nen quan tong hankhi gill quyet cac dtt lieu sai lech cao, tirc la, khi mOt vai dtt lieu c6 nhieu yeu eau han nhung cal Ithic, d6 cUng la trutmg hop cho cac img dung TIS. Vi du, chju trach nhiem cho mOt phlin down tren dutmg cao tec co nghia la nhieu dIt lieu di luu tray va truy yin han so vai quan mOt con duttng nhe 6 vfing ngogi 8. Cach don gian Mkt de gill quyet yin de nay va de ce duqc mOt can bing di la di tang

CHUONG 3. NW-NG UNG DUNG CUA VANET

s6 luqng cue cac thiet bi ngang hang chiu trach nhiem cho tong phan down, qua d6 giei thieu mOt se du phong va ket qua trong mOt kh6i lucmg cong viec phan phii Ong bang hon.

Cic he thing dii neu 6 tren den nay c6 the cung cip chirc nang tuong to nhu kien tnic Ichach/chu, trong khi n6 khong yeu ciu chuyen dung, co set ha tang t#p trung. Tuy nhien, den nay, chiec xe c6 nhu cau de co (kw nhOng thong tin day du cac tuyen dubng quy hooch va thay the. theo dOi nhttng thay trong filth hinh giao thong tren tuyin dubng quy hooch va phan Ong vol nhttng thay dei, Ong dung thuc hien can truy yin dinh ky yeti cac thiet bi ngang hang khac. Giiti phap tier phong by se too ra mOt se luqng km luqng mung du dills.

MOt giui phip c6 the s* dung m8 hinh truyen th8ng gieng nhu giao tiep nhom, vi du cong cOng/diing ky. Trong phuong phi!) nay, cic (mg dung, thay vi dinh ky yeu ciu thong tin m6i, c6 the (tang ky cho cl* lieu tren cac thiet hi ngang hang chiu trach nhiem "dang ks" Ara se duqc thong bao ye bit thay quan tong tren tuyen dubng quy hooch. Cac thiet bi ngang hang chiu trach nhiem cho tuyen dubng nay thong bit° cho tit ci cac ben quan dm den nhttng thay del trong cac dieu Ides giao thong.

COC61e tinh Wing hip din nhit cda phuang phip dip cn ngang hang la Ichit nling to mer rOng ctla no. Trai ngtrqc vol kien trac khach/chk se luqng cac nguiln tai nguyen c6 sin trong mung la tS, le thutin voi s6 luqng nguiri tham gia. Do d6, quy m8 mung ngang hang tang vol si luqng ngay cling tang alit ngtroTi sir dung. Tir khi de lieu thrqc phan b6 cho nhitng ngtrbi tham gia kliong ce diem that bai vi khOng mit chi phi ye tit chinh va t6 chirc may chi' chuyen chmg.

MOt bao (cid:9)

ngang hang dua tren mpg luoi cu so ha tang thong tin lien lac hien c6. VI y(iy, trong to nhu truting hqp khachkhk cach tiep can khOng phai la phu thuOc vio mOt de thiet bi cao nhu mOt Ong dung VANET. Tuy nhien, mOt nhuqc diem as phuang phi') ngang hang la viec stl dung bang thong ye tang the cao hula so vol mOt kien trim khich NO bao gem clic chi phi chuyen tiep caa cac truy yin Ara c#p nh$t ctla nhttng ngtr6i khic va de duy tri bao phi'.

3.4.3. Truyt4n thong trong VANET

Xem xet cic (Ric diem ctla mOt Ong dung TIS, thiy ring nhieu xe dang quan tam den thong tin tuung ty, dtic biet la khi xe di cnng met hien hoc the diem den cuing tuang tq. Ca m8 hinh mung khach/ch* ding nhu cac inking ngang hang dun tren truyen thong di dOng c6 the lam cho viec s* dung cua thuc to nay met cich thing ye phia truac VANET, nguqc lui c6 the vi ban chit phut song, mei throng mang khong day da buck he tsq cac m8 hinh thong tin lien lac not Mayen thong gOi den nhieu ho#c tit ca

CHUONG 3. NHONG ONG DUNG CUA VANET

cac nut trong van lin c#n gin nhit. Do d6, d6i v6i loui img dung nay, ne kitting phai la bit hqp ly khi dung lam co s6 cho VANET.

MOt each flap can chung se su dung cac canh bao cep nhat djnh 14 theo each sau: xe m6i quan sat ching hun nhu mot dO giao thong, s6 luqng clia diem dO xe mien phi, ...vv, lien quan den mOt vi trf trong Idgeg gian (t(c la, mOt phan down dating ho#c khu Arc nh6) va la mOt muc thbi gian.

IChi quan sat di duqc thuc hien. Tit ca ho#c mOt phin cua thong tin dugs ltru tilt tai dia phuong djnh ky quang ba. Sau khi dip nh$n quang bao nhu Aty, mOt nut kit hqp cac de lieu nh(in duqc vao co str de lieu di Met Bing each so sanh diu thbri gian quan sat, c6 the dam bao ring luon luon la gia tri cop nh#t cho mOi vj trf ckrqc luu hit va phfn ph6i lui.

Trong nhttng vin de va khit fling m6 rong di duqc thao luon 6 ten, cin thiet phai phi bien cac clit lieu do luting va tit ca cac chi tiet trong mOt khu vttc rung 16n. Da khic phuc vin di nay, vies sir dung cac tip hqp dtt lieu phan cip da duqc a xuit: khoang each ngly cang tang, cac quan sat lien quan den cac khu Arc ngay cang 16.n hcrn (ho0c dO dai down dating bO) duqc kit hqp thanh mOt gia tri duy nhit. CO the la mOt gia tri t6ng hqp nhu t6c dO trung binh ten down dating, hokic tS, phin trim cua dja diem d8 xe mien phi trong mOt phin mkt mOt thanh ph6. DO lieu th6 duqc thuc hien tai khoing cash lon ham, dft lieu chi fiat duqc km gift tong yang Ian cfm gin hon.

Chit hr ng cua cac thong tin TIS cung cap cho lai xe ve co ban phu thuOc vao chit luqng cua 14 thu#t tong hqp. VI the tong cac phin tiep theo se xem xet cu It chi tiet hai co chi t#p hqp. tit ca cac muc tieu trong mai trutmg hqp xe lay s6 do ctia thbi gian kink nhau va vj trf phu thuOc vao cac thong s6 va de lieu quan sat nay doge ph6 bian tong VANET thong qua cac cash bao dish kk. Diu tier mer to mOt cash tiep c#n stir dung ky thu#t xac suit de lieu dui dies cho hqp thong tin tong mOt khu Arc: yell Ichoing each ngay cling tang, cac gia tri do lien quan den cac khu Arc 16n hen duqc kit hqp vao mOt muc de lieu duy nhit Dieu nay rat hOu fch cho tip hqp cac th8ng s6 nhu s6 luqng cac dja diem d8 xe mien phi trong khu Arc, mit dO xe, ho#c lieu klen doting.

MOt phuong phap dip c#n dua ten khu Arc ce nhCmg hen the khi de c#p den eau va t#p hqp thtri gian di chuyan trong mOt mung lueri dubng cho mOt hu th6ng chuyan huOng dung. Da xac Binh dieing ngin nhit tir diem diy den mOt diem xac djnh, mOt ban t6m luqc dip tren cac khu Arc don dOc IchOng phai la thtri gian di chuyen trung binh duc theo tit ca cac clop dutmg tong mOt s6 phin cua mOt thanh ph6 kh8ng phai la d#c biet tau fch cho muc dich xac dinh cac tuyin doting t6i uu. Trong phin 3.6 se flip tuc vai mOt each flip con thong tin tuyan dating t6qg hqp.

CHUONG 3. NHONG LING DWG CUA VANET

3.5. XAC SUAT, T4P HcfP THEO VUNG

MOt vein de quan tong ala tip hqp de lieu trong VANET la sv danh gia ye chit luqng hoc cep nhit thong tin tong hqp: Trai nguqc voi quan sat duy nhit, gia trj tang hqp khong the duqc so mirth Ulm tiep dtra tree Whin thoi gian. Cac ban tem tit vi dv, tong s6 dja diem d6 xe trong met se phis c6a thanh ph6 duqc too ra bdri xe thuOng sir kheng phai c6 phien bin cip nhot c6a tit ca cac de lieu co so c6 sin. VI viy, tip hqp nhieu lin cho cung mOt khu vtrc c6 the ten tai, dtra tren cac diem Ichac nhau, nhung c6 kha Wing chin cheo kien thirc. Quyet djnh gift lai cai nao dtra tren dfk lieu co ban la kh6 khan, nett khOng phiti la khemg the. VI viy, lam the nao khi xe duqc cung cip hai phien ban clia cung mOt tong hqp va nen quyet djnh cai nao cin gift (va ph6 bit% n6)?

De tra 16i cho cau bed nay, phai mo rung Sr tuOng du lien duqc neu trong chuong phi Bien thong tin va thito Juin chi flit hon ve mOt ke hooch, ban du duqc de xuit trong Lochert. Cach tie') can nay cho thiy vin de c6 the duqc lchic phvc neu ca hai quan sit va tjip hqp don 16 kh8ng mang gia trj quan sit trqc tiep, nhung thay vi ce ch(ra mOt gia trj xip xi trong hinh thirc cOa mOt phac thao cai goi la tang thai thai mem. Trong khi phac thao tang thai mem vin 'thong cung cip mOt cach de so mirth chit luqng c6a hai tap hqp trtrc tiep, cho ph6p mOt cai gi d6 tit hon: nhieu tip hqp cho cung mOt khu Arc c6 the duqc sap nhip, mang loi mOt str kit hqp mai mi ch(ra thong tin cua bit hqp nao. Do d6, khong cin phai quyet djnh tang hqp c6 chfra thong tin cip nhit.

3.5.1. Phdc thdo FM

Phic thao trong thai mem la mOt phien ban ma rung va sea d6i bin phac thao FM. Cac phac thao FM ban du duqc gioi thieu trong b6i cimh co stY du lieu, NH Flajolet va Martin. MOt phac thao FM dal dien cho mOt xip xi dm mOt se nguyen ducmg truting bit S = se,..., s,, chieu dai w 1 throng bit duqc Uteri to bang !thong tit ca cac vj tri. De them mOt x yeu t6 de phac thao, n6 duqc brim thanh mOt ham barn h. V e mitt hlnh hoc, ham barn nay di plain ph6i tich cvc diu ra s6 nguyen, xic suit ma gia trj bitm h(x) caa x la bing i la duqc dua ra bOi deg thir

P(h(xi) = 24.(31) Han shoo sau d6 duqc that lip. (VOi xac suit 2', c6 h(x)>w, trong tnthng hqp nay, hoot dOng kh6ng duqc thvc hien.) MOt him brim v6i cac thuOc tinh cin thief c6 the dg ding duqc bit nguen tir mOt ham blim ph6 bien IA du ra thong nhit phin ph6i chugi bit bing citch ding vj tri cua cacl- bit die lien trong chugi du ra li gia trj brim.

Kit qui quan tong (cid:9)

Flajolet vi Martin li mOt xip xi C(S) c6a 56 luqng cac yeu to dac trong duqc them vac de phic thio co the thu duqc tir chieu dai c6a chugi ban diu Ichong bj gian doan, duqc dua ra.

MIXING 3. NI-ONG ONG DIJNG CI:JA VANET

E E No I KwA s i4.1 = 0) U {w)), (3.2)

Z(S) (cid:9)

(s)

rp ~ 0.77351

2z — (3.3) C(S)

Phuang sai (khit 16n) cia Z (S) c6 the duqc gilun bing cich sir dung ban phic thbo song song, bing cich s6 dyng mOt ky th4t goi 1a tinh xic suit trung binh ngiu nhien (PCSA). De blot them chi tiet, xem Flajolet and Martin khi phic thbo m duqc sir dung, PCSA mang lni mOt sai so chuin khoing 0,78 / I m.

Phic thao FM co the duqc sip nhip de ce duqc t6ng so cic yeti t6 rieng biet duqc them vio bit Ick xe nio trong sO de chi don &in bang mOt ph6p toin OR. Quan tong la, bang each ciu true cia n6 c6 that ket hqp nhieu lan nhang ban phic thbo twang tq hocthem cic yen t6 di c6 sin mOt lin nee 'thong lam thay dui ket qui, bit ke la cic hoyt dung nay dinra thutmg xuyen hoic theo dui n it.

3.5.2. Ctic ban pink thao cho tflp hop dtt Iiin trong VANET

Vai muc dich ctla cuOc thbo luin don gian, xem zit mOt loci cic he th6ng thong tin giao thong cu the: gib sir rang dang quan tam den vies ph6 bien s6 nai de xe mien phi. Doi yeti th6i diem nay, b6 qua thuc to la s6 hrqng thay dei theo tit& gian. Buck diu tien, sir dung mOt phic thbo (hoic PCSA, hocmOt top hqp cic bin phic thbo) cho me i Boon du6ng. Gib dinh rang mOt chi& xe c6 the quan sat sO Wang nai do xe mien phi tai nai n6 di qua, vi du bing each thu thip de lieu tar cam bien vbo nbeng nai d6 xe. Sau khi di qua mOt (loan &Ring WA ID vb quan sit duqc x diem d6 xe mien phi ten de, mOt chitc xe c6 the them cic bO de lieu (r, 1 ),..., (r, x) de phic thbo cho r, bling each aim n6 vb thiet lop s6 bit tucmg img.

17,4)

h(V17,2) h(17, (cid:9)

1 (cid:9)

1 1 (cid:9) 1 (cid:9) 0 (cid:9)

Phisc thao trtretc khi tigp nhilin

2 Phac thao sat nhOp eau khi Otto nh4In

iii

Philo Maio de truyen

co I 2 o (cid:9)

h(17,3) (cid:9)

h(17,1) h(17,2) (cid:9)

h(17,4) h(17,5)

Ifinh 3.5 The` hg va hqp nil& cinz Op hop ph& thew FM

Cac phic thbo luu tre cac &>}n throng cuc be duqc quang bb dinh kiy tai cac net lin can bang mOt buac nhiy Sau khi ben nhin, nhin duqc vb phic thao chit phuang duqc sap nhip bang cich tinh toin phep toin OR cac bit. illnh 3.5 minh hqa cho the

CHYONG 3. NHONG UNG D1,JNG CVA VANET

tuc nay. Hai xe 8 to, A va B, c6 the quan sit dOc 1(1p tren cang met /loan du/mg (veri ID 17). A quan sit ben dja diem d8 xe mien phi vi do de bam thinh (17.1 ),..., (17.4) phic thio cho do?n du/mg 17. B quan sit c6 Wan diem de xe mien phi, vi do de be sung them (17.1 ),..., (17.5) neu A vi B g#p, vi nit#n duqc met truyin c6 china phic thio cua B, kit hqp n6 v6i cic bit vi c6 duqc mOt phic thio m6i, thay the cii truck de. Re ring, dieu nay c6 the duqc 14 di 1#p lai bit dr khi nao c6 xe a to dip (mg, de th8ng tin a xe tiep tic c6 the duqc kit hqp, trap dei, vi truyin lai, qua de licit liiy "kien

thirc" teng hqp.

Luu jr ring cic be de lieu bilm (r, i) la gi8ng het nhau cho nhitng quan sit 'chic nhau, gia trj quan sit duqc xic djnh duy nhit lam the nao de be de lieu dupe them vao. Neu mqi ngtai quan sit se dung cling met ham ham, cling mOt so dja diem de xe mien phi tren can met doa ► dueng se thiet 1#p cic bit Luang a. Cic thu#t toin ca ban hien nay, cic bit met lin duqc thiet 1#p se khOng bao gib duqc bo, va do de phic thio kh8ng the Ilan giam gii tri. Do de biy gib lam the nao de me ring ciu tree de lieu de khic phuc han chi nay.

3.5.3. Pluic than trgng thai mem

MOt bit bao gib ding duqc fiat lip, cic ban phic than se dpi dien cho tit ca cic gii trj kitting quan sit thiy cua tong down duang. De khic phuc vin di nay, met phuang phip cin thiet de loci b6 cic quan sit ce. Dieu nay duqc thuc hien bing cich thay cic phic thio FM ban diu. Su dung bO dem nhe chi& dai n bit thay vi mOt bit duy nhit tai mei chi se vi tri. Cic be dem nay dai dien cho met thei gian tem tai (TTL) trong - 1 bit de. Cic hoot ding thiet lip mOt bit de sau khi quan sit duqc thay khoing 0,. (cid:9) the bing cich thiet lip cic troy c#p Wang ling voi TTL, t6i da, T: = 2° -1.

Cic canh bio c6 china nlang ban phic thio duqc gei deu (W. Chi dm truOc khi gui mOt cash bit° v6i thong tin ttY ca sat de lieu di biet, tit ca cic be dem dm ban phic thio tai dja phuang diu dOn duqc giam di met, neu gia tri cfia be dem khic khOng. Khi kit hqp met ban phic thio di nh#n duqc vao ca so du lieu di biet, cic phep toin OR dtrqc thay the bang thu#t toin tOi da Lung vj tri. Dieu nay mang lei met Min the ala tang thai mem ye phic than FM, trong d6 cic yeu t6 duqc dua vao truOc de bj chit sau khi TTL caa da het han, tnY khi n6 duqc him mai WA met quan sit mei hon. Sip nh#p duqc m8 to trong hinh 3 6 Xe nh(in dugs met temg hqp tir B xe, vi c#p nh#t phic than mpg thii mem dia minh cho phe hqp.

CHUONG 3. NHCING trNG DIVING CUA VANET

Phac that) trutm kid tiAp nhen

4 Philo thao sat nh ► p sau khi tiep nhen

0 (cid:9)

Pluto Mao de tory&

I (cid:9)

Hinh 3.6 Kit hop phac than a trgng thai mem

De c6 duqc gia tri hien tali t mOt phk thio trung thai mem, thuilt tam yin ca bin Idiong thay d6i, vi tri chi s6 nho nhit c6 gia tri khOng duqc xac dinh va su ding. Luu Sr ring dieu nay phii ganh chiu mOt s6 chin trg neu mOt vi tri bit khong con that 10p trong cac quan sat moi han. Ter 1th vi di tren: quan sat nhCmg nod dir xe, gia sfr ring king c6 quan sat nio flip tic duqc thqc hien mat thiet 1#p mOt vi tri bit ci the (vi di, bbd vi khong con mOt chr5 drS xe mils phi duqc barn veld n6). Neu vi tri di duqc d#t trong mOt tang hqp, sau d6 gia tri TTL se giim theo Uri gian cho den khi n6 den gia tri kung.

3.5.4. Binh thank khu vim Ian hen king hpp

Dva tren phac thio tang thai mem, t#p kip thu b#c c6 the duqc thqc hien theo catch sau. Tnrac tien, cin meth thang phiin cip cac khu vqc thqc hi'e'n t#p hap. MOt khu Arc c6 dO phan cip cao han thong thu6ng bao gam hai ho#c nhieu khu vvc cip dual. Dai vai mgi khu Arc tren ting cip cia he th6ng phan cep, Thqc hien cac thea thu#n cho mOt phac thio trung thai mem dth dien cho cac gia tri (tang hqp) cho khu Arc. Bit kSr quan sat duqc thqc hien cho met sa h tri nao ngay lap tic co the duqc ket hqp vao m8i tang hqp c6 chia cac vi tri. Kit hqp thong tin ve mOt trong nhieu ving phi vio mOt t#p hqp tom han c6 the duqc thqc hien trong cing met cach chinh xac nhu sap nh3p lud ban phac thio cho cing mOt khu vqc: bang cach tinh tom t6i da vi tri cis 'thing bin phac thio trong than mem.

Ti cac d c tinh di a:4 a tren, clA clang thiy ring cac tip hqp duqc hinh thimh theo cach nay bao gam cac phep do tir tit cal cac khu vvc thanh phtut cia no, theo di cac thong tin mei c6 the duqc them vio bit ki tic nio. Bit IcSr khi nao nhon dulqc phac thin ngay 1#p tire c6 the duqc kit hqp van tang hqp lin han bao gam cac Wing cia bin phac thio nh#n duqc. Dieu nay di mang cic thuOc tinh mong mu6n duqc de c#p 6 ten: kung cin phii virt b6 mOt trong nhing t#p hqp thay the nhieu cho cing met khu vqc mat c6 the ket hqp chimg de c6 duqc mot tong hqp mil, c6 the dg Id& de hien thi vimg phi sang tat han vi cung cip han thong tin cep nh#t cia khu vqc nay han bit kir thinh phin ca nhOn d6 duqc hinh thanh

CHLrONG 3. NHUNG ONG DVNG COA VANET

Tat lai yeti vi du ting dyng ye tinh nai d8 xe mien phi, nhang t6ng hop nay se ce tong s6 cac diem d8 xe milli phi tong khu vyc tuang ung. ThOng tin ve cac khu Arc quy m8 nho dien hinh duqc luu gift trong vOng len Qin gin han, trong khi xe 8 to di m xa han se duy tri va phan phei cdc tong hqp nay tOt han tren quy m6 caa khu vue krn hon. 3.5.5. Nghien thu fin dyng

De b6 sung cho cac thito lu#n IS/ thuyet 6 tree, met lc& qua vi dy fir cac nghien dru m8 phong duqc thuc hien trong Lochert, su ding mOt mei tru6ng ma pheng tuang to nhu met 6 tree trong myc 3.2.2, v6i tS, 14 them nhop 20% thief bi VANET trong cling mOt thimh ph6.

So sail ket qua dot duqc voi top hqp xac suit de ce &WC mOt giao thuc tham chieu t6i uu. Trong giao thuc nay, thong tin duqc ph6 hien b6i cac earth bao dinh kjr. Tuy nhien, giao attic t6i uu khong quan tem den nheng giai han bang thong thuc te. Trong m8 phong kich thuac cita gei vii so hrqng thong tin trao dOi gifta cac nut la dOc lip. Giao thuc tham chieu khai thac thyc te va kh8ng tAng hap tit cit thong tin. Thay vao d6, nh#n duqc "tong hqp" bao g6m c#p nh#t gia tri do cia nut giri 6 tit ca cac dia diem. RO rang, thyc hien giao thuc tOi uu nay tham chieu la a clang trong m8 phong, nhung khong phai trong thuc te. Tuy nhien, n6 cfing ph6 hqp nhu la met tieu chuin veil mOt giao thuc thuc te dya ten cac cash bito va co s6 dift lieu di biet, nhftng chiec xe khong bao gib c45 thong tin tOt han.

Dinh gia ca hai de an ten va tham lchao cite giao thuc t6i uu v6i mOt ling dung Wong. Chia nh6 cac khu vyc thanh ph6 thanh 256 khu vqc nhe, ma chung to sift dyng nhu la dia diem duy nhit. MOt qua With ngiu nhien don gian tao ra met gia tri thin gian cho m8i vtIng 'chic nhau, c6 the "do" nhfing chiec xe trong vUng tucmg (mg. Dieu nay ce the duqc hieu la "dem" s6 dia diem d xe milli phi trong khu Arc nay, gin vOi vi dy duqc sir dyng 6 tren. Tuang to nhu vey c6 the coi la met m8 hInh trOu Wang cho bit lcSr khoang th0i gian do lu?mg lchtic nhau. Lien quan den 016i gian m8 pheng twang d6i ngin 15 phitt, nhitng thay d6i cita cac tham s6 m8 pheng rit nhanh chang.

Thiet 1#p nhu v#3, la nit khe khan cho mOt giao thuc ph6 bien ma cin phiti theo d8i chimg. Ngoai ra cac tham s6 Wen thien theo th6i gian rieng cita mink. Dieu nay cho tinh town dpi dien tuang d6i "phin nho cis nai 418 xe min phi" va de phalli biet gifta tinh huOng ma khong c6 thong tin va gia tri ph6 Wen la s6 IchOng.

Hinh 3 7 the hien mOt khu vyc duqc tong hqp ten b6n khu vyc tong m8 phong. Hlnh nay m8 to lam the nao gia tri tong hqp mkt khu vqc nay duqc met chi& xe trong mOt khu Arc Ichac 6 khoing each khoing 3 km thiy duqc. Dieu nay duqc so stinh voi giao thuc tham chi& tOi uu vi gia tri thqc stir meo pheng khu vyc quan sat. D6i yeti ca hai de an nay t#p hqp xac suit va tham Ichito CAC giao thuc toi uu, co mOt khoing th6i

CHUONG 3. NHONG IYNG DUNG CUA VANET

gian re rang cho viec yen chuyin th8ng tin th8ng qua VANET. Doi voi de an tang hqp phic thao tang thii mem, ding c6 met sv chilm trg nhat dish truck khi gia tri giam dm, tucmg Ong vOi thei gian can thiet cho phan ra cUa trong thai me'm cult cac bit kheng can thiet lip. NO cling khong ding ngac nhien Uri ngay c4 nheng giao thfrc tai uu tai lieu thaw khuo khOng phai luc nio ceng c6 thong tin day (II Neu c#p nhOt chi tren cac be ph#n cua khu vrc thi t#p hqp tang sa hien tai vi dl lieu nay lchOng phai luc nao cling la dien hinh cho town bO tang hqp. Tuy nhien, ink tinh phin anh tinh hinh thvc stir trong khu Arc theo m8 hinh tat, dieu nay Ong c6 the thytrong cac truing hqp khic.

tong hqp v xa

Hinh 3.7 flu chink xac (cid:9)

Tom lai, tap hop xic suit dva tren phic thao c6 the dugs se dung de tgo ra tftp hqp gall yen ly thuyet co the dot dtrqc. Day la mOt kit qui rat ding lchich le, trong de nhan marl ring cac thu#t tan de xuat la mOt each phe hqp de vuqt qua khe khan chung thtemg gip cua phin ph6i, tap hqp de lieu kheong phe hqp trong qua trinh pk6 hien.

3.6. T4P HOP THOI GIAN DI CHUAN

T#p hqp theo vung la rat thich hqp neu mOt Ong dung yeu eau tom tit qua cac khu vrc. Tuy nhien khong phai la truing hqp cho mOt img dung cu the, n6 c6 mOt s6 han the Whit djnh. De xay chrng mOt he thong deng, hqp tic djnh huang dueng dva tren VANET, mOt each tie') c#n chung la de phin phai thong tin ye th?ii gian di lai doc theo (loan dating. Trong truing hqp nay, tom tit qua cac khu Arc khong gift') de. Trong khi mOt s6 khai niem chic chin duqc chuyin nhuqng, (ho#c (rung binh) tang thei gian di lai trong met khu Arc khong phai la mOt khai niem hitu fah. Vi 4y, Si Wong la can thiet ph& giiun so luqng dit lieu thin gian di lai vei khoing each nay cling tang, trong khi yin cung cap thong tin hen ich cho nguei nhan. Bay gib chOng to 0 thio lufm mOt each dip c#n chi flit dif duqc phic thito trong chuang phi hien thong tin. Ban du n6 duqc trinh bay trong Lochert va di khic phuc nheng van de t#p hqp

CHUONG 3. NHONG ONG D1,JNG COA VANET

dt•i veri tnrtmg hqp co the dui dit lieu thtri gian di loi h8 trq guy& djnh chuyin Wong du mg bO. lir Meng chinh la sir dung xttp xi Oa mpg luai dutmg bO vci khoitng cach

ngay cang tang. 3.6.1. TOp hpp Ara tan aim mac

Y Mang ca ban cult chucmg trinh tang hqp la dip vao cid gai la diem m6c.Citc diem mac trong mpg huh duang be, dien hinh la cac nut giao diem. Cac diem mac duqc xac djnh tren nhieu cip de cua met he thong phan cap trong mong Wei dulmg be. 6 cip cao nhit, day la nheng nut giao cua cac tuyen &Ong chinh ho#c during cao tac. Cie cap thip han bao gam tit ca cac diem mac mix cao ham cOng vai nut giao thong cua cac throng nh6 hon. Mirc thip nhit la mOt doi dien cua town be mong ltrai dutmg be.

(5 t8 di qua met door dutmg c6 the too ra mOt quan sat thtri gian di loi gifts hai diem mic Ilan can. Thong tin nay duqc phan phOi trong phom vi gin. N6 duqc stir dung Uri xe de tinh town thoi gian di chuyin gitta cac diem mOc cua cap tren trwc tiep, qua d6 tem tit thin gian di chuyin trong khu Arc. Hinh anh th8 tren thoi gian di loi duqc phan phoi trong met dien tich lon han so voi quan sat xe ca nhan NO Ong duqc sit dung de tinh town thtri gian di chuyin gitta cac diem mac cap tren ttvc tiep cua he thong phin cip, va dr nhu 4y. Hinh 3.8 cho thiy mOt vi do cho he thing plan cip duy nhit. Thtri gian di loi gitta hai diem mac Eiffel Tower 4 Arc de Triomphe duqc xfic djnh. Hai diem mac cao cip duqc kit not tilting qua met so toy& du?mg c6 the dOi yeti cac diem mac 6 cip thip han, 6 day chi ra boi cac yang ton. Th6i gian di lid glum nhang dja dank nay thip han mitt duqc Wet den, hoc la t6 nhang quan sat truc tiep ho#c t6 tip hqp duqc nh#n hoctruck day di tinh cip thip han. Thai gian di chuyen duqc tang hqp tir Eiffel Tower va Arc de Triomphe la th6i gian di loi duc theo My& dutmg la th6i gian di chuyen tai thieu gitta hai diem nay. va cot ban, nen tit ca cac thong tin tren tit ca cac con du6ng c6 the c6 gitta hai diem mac cho mOt lien ket "ao" ket not chimg.

63

CHIANG 3. NHUNG UNG DVNG C1:JA VANET

Huth 3.8 Tong hpp aim mek

Czech tiep cOn nay co the duqc ghi nhu sau. Mang luai duOng bet c6 the duqc xem nhu la mOt dung d6 thj G (E, V) bao geNm cic nut v E V va phin down duang e E E

V2 kit n6i cic lien ket nay.

Cic phan (loan duqc gin mOt trong s6 w (v1, v 2) tuang Ong vai thOi gian di lai hien tai. MOt s6 nut giao thong duqc phan biet nhu la diem m6c 1 E L, L S V. MOt tuyen din`mg r (A, B) girra hai diem A vi B 11 mOt chai cua cic m6i (v 1,..., v.) nhu v.y ma vi = A, v„ = B vi tit ci cic cep cua cac mOi n6i lien tikp duot ket n6i boi mett down duOng, tire la cho tit ca cac i = n — leo tun tv (vi, vi+1) E E. Chi phi cua tuyen throng nay

n-1

I I Oh ••• • Vn) I I := E

t=i Cho R(A, B) bieu thj cic thiet cua tit ci cic tuyen duong ter A din B. Sau de

co the xac djnh con duerng nhanh Whit r *(A, B) nhu sau:

r (A, B) = argmin I Ir I I rEs(4.8)

Ile (A, B)I1 dtrqc sil dung nhu than gian di I* gift hai diem A va B 6 mirc cao han, tirc la, cic hoat dung thuc hien khi tinh toan mOt tting hqp de xic djnh lir * (A, BM dVa ten thin gian di chuyen thip han he thong pilau cep. Bit 10 thuUt tofin djnh tuyen tieu chain nio ciing ce the duqc sir dung de tinh toan Or s (A, B)II. Luu si ring no IcheIng c6 lien quan tuyin throng thuc su cho ket quit thOi gian di lai nay. Chi& xe cling xa hai diem m6c, Wiling thong tin hen quan la n6 ce the di ter A den B trong thOi gian Whit djnh. Khi ne den gin han Ichu vut tuang img, n6 se nhon duqc thong tin, sin c6 6 dia phuang vi chi tiet han. Thong tin nay sau da 06 the duqc sir dung cho djnh tuyen.

CHUUNG 3. MOM UNG DUNG CUA VANET

Thai gian di chuyin la tang hqp nen 'thong tinh cho m8i cep mac. Dieu nay se din den trong mOt se tip hqp phat trien nhu 0 (n2) vai sO lacing va nhAn. Tuy Mien, tong hqp than gian di chuyen gifts cac diem mac 6 xa nhau cling khong don gap nhieu th8ng tin: se co nhieu diem mac lchic "6 era", vil mOt chuii cOa tap hqp tin nhung xe c6 the P xa mac. Do de, chi xem xet nhang P khong la xip xi ciut thei gian di loi era cac qui xa nhau. Na co the stl dung mOt tieu chuan c6 djnh, giOng nhu mOt khoang each throng bay thing tai da la Op cOt mac ma tip hqp duqc hinh thank ten mOt mire phan cap nhit dinh cua he thOng, ho#c de dank diu cac P mac ro rang tong cic dit lieu ban 0, nhu v#y mOt xip id cua mong luai throng bO ca ban duqc day tri.

3.6.2. Think gig chit luvng thong tin

Tnrac khi tinh Wan tang hqp than gian di chuyin giita hai diem mac va yao xe kit& di qua no, mOt chi& xe can co the dinh gia xem kien thirc ve firth tong giao th8ng hien tai cho mOt uac luqng tot. T>r quan diem rat chung chung, mOt s6 luqng lon cac doon dm:mg c6 the nom tren mOt tuyin duang c6 the c6 gifira hai diem mac. Do da, can thief de xic dinh nheng doon throng c6 khit nAng c6 lien quan den tinh tan thai gian di loi. TOng hqp c6 the duqc hinh thanh neu thong tin tren cac doon duang lien quan lien dja phuang 11 c6 sin.

De Vic djnh t#p hqp cic doon dating lien quan, chung to nhln viio nheng gi pi la tieu chuan thai gian di chuyen dqc theo (loon duang. Nhung thai gian di chuyin rat kh6 mA has cac dit lieu ban 0 dating bO vi doi dies cho kY vqng hqp 1S, ctla thei gian di chuyen, vi hien dang duqc sir dung cho he thOng djnh vi dating kW:mg du% dOng. MOt each de dang c6 the tinh town cac tuyen duang dot tieu chuan tOi uu r .std(A, B) 131 A den B tren co s6 cdc dit lieu tinh nay chti yen 11 he thOng djnh vi hien toi. Doi vii bat 14 tuyen (tut:mg r, n6 ding de ciing tinh toan than gian di chuyen tieu chain r ol.

Sau da chqn mOt nguang 0 > 1. Xic djnh thiet lip R(A, B) cua doon Ming lien quan gifts hai diem mac A va B bao gOm tit cit cite doon dulmg nam tren mOt tuyin duang mi thai gian di loi cac yeti t6 alit 0 dii han than gian di loi tieu chitin tai uu, tic li, mOt e doon duang trong R (A, B) neu va chi neu co ton tai mOt tuyen dating (v 1,..., vn) VI A den B nhu la mOt phan cua tuyen throng de vi

II( Vb. • ..,V011sid 5 0 . lIrssid(A,B)11std- Tieu chuan nay chi dya ten than gian di chuyen tieu chuin (filth), tip him the doon duang lien quan, khong phu thuOc vio tinh hlnh giao thong hien tai hale Iden thirc hien tai cua xe. Thai gian di chuyin tang hqp ttl A den B co the duqc tinh neu thong tin ye cac doon duang trong R (A, B) c6 sin.

CHUONG 3. NHONG ONG DIJNG CUA VANET

Cau true hing hip dam mec

Di thqc hi'e'n t#p hqp thir 14c, mac chi dinh met mire trong met he th6ng phan cap. Cac diem mac cia cap cao ham cling la thanh vien cua tit ca cac cep thip hon. Cho met t#p hqp cac diem m6c la Li.

1.4c (cid:9) cV > 1

De tgo thisnh met tang hqp tren he th6ng phin cap mire i, nhftng t#p hqp cap i - 1 duqc sir cb,mg gi6ng nhu each quan sat ca nhan cia xe duqc sir dung 6 mac dau tien. VI vily, nhing diem mac tren cap i -1 duqc se dung nhu cac nut trong nhttng than luin tren, va tang hqp thin gian di chuyin gift chimg vao vai fro cua than gian di chuyen

dqc theo cac phin down duing ca nhan.

Hinh 3.9 Thong tin có sand cdc clip 45 kit& nhau

Khu vqc ma trong di cac quan sat ca nhan va t#p hqp duqc quing bi hgn chi dqa tren mire cis ni trong he th6ng phan cap. Quan sat ca nhan duqc philn tan trong met phi= vi rat hgn the trong khi t#p hqp cap cao nhat duqc phan tan tren town be mpg, hinh 3 9 m8 to dieu nay. Wag tin xung quash chi& xe 6 duel cimg cia cho biet cac khu vrc th8ng tin chi tiet, dieu chink cap 0, thong tin tang hqp cap 1, va th8ng tin tang hqp cap 21a ci sin cho chi& xe nay. Khi xe di den dich cim ni, cac khu vqc nay thay d6i cho phi hqp.

Cac diem den cis met chuyin di se kliong phai luc au cling la met mac tri cep cao nhat. Tuy nhien, cac th8ng tin tang hqp co the duqc se dung cho quy hogch tuyen during. De lam nhu v y, met he th6ng djnh vi se "died' th8ng tin thieu gifta cac diem den cuei cing va diem m6c bang each s* dung than gian di chuyen cac tieu

CHISONG 3. NHONG ING DUNG COA VANET

chuin mi h6a dlt lieu ban do. Dieu nay la hop lSr, bpi vi mOt guy& djnh cuei cling ye Oen con lai cult tuyen (luting la chua cin thiet tai giai down nay la diy du neu met Iva chip t6t cho cac quyet djnh djnh tuyen ngay ttic sip ra met c6 the duqc thoc hien. Trong khi xe tiep can diem den clia n6, tuyen dtrOng c6 the duqc cap nhat va loc khi thong tin chi tiet tr6 thank c6 sin.

3.7. ICET LU4N

Trong chuang nay, di xem xet mOt s6 khia canh quan tong c ► a cac Ong dung tien lqi VANET. Vai tro clia ne ce tiem fling ding ke nhu yeu to thj trtimg la mOt thimh c8ng nhung hgn chi, Icha Wing ten tgi va ket nei cling nhu c.anh tranh. Vi co minh hoa lam the nao han che tic dung sau cac Ong dung VANET, do d6 cling chi ra nMng gi nhl cac duet ke giao thirc phai ghi nha trong bpi canh VANET.

tren di trinh biy mOt h thOng giao thong co the, de chimg minh ring cic img dung tien lqi rit lch6 ce the duqc thoc hien thong qua c8ng nghe VANET. Dac biet, tr tren di trinh bay hai phucmg phap tiep thuat toan co the di thiet ke cac giao tinic truyen thong kha Ming mo rung trong VANET, va qua d6 chimg minh lam the nao n6 c6 the doSi ph6 voi Igui chi clia no.

TONG KET

Chuyen de nay da gibi thieu ljch sir phit trien caa VANET qua timg giai down 6 cac khu Arc khic nhau. Va litm the nao de c6 the truyen duqc dit lieu trong mpg VANET, chuyen de cling de cep den cach truyen thong tin trong mpg vi cac vin de han the curt mpg VANET nhu han the lchit tiling cart 'riling, hap the ve lcha !tang kit

nAi, cAnii tranh vai cac mang sin

Sau mOt th6i gian nghien cum, cac lc& qua the hien tong bac) cao chuyen de duqc

tam tit nhu sau:

Mang VANET duqc kY vong nhu mOt ha tang thong minh cho he tilting giao thong hien dui, mOt boat cite tien ich duqc de c#p den trong cac nghien cim va tan khai he thong duqc tam tit trong bito cao. Tuy nhien, su khic biet ye mai tru6ng img dung, cac c8ng nghe mpg vi kiln tic da d(it ra cac thach thirc cho cfic nha nghien tiro va hien khai he thong. Cac vin de tren duqc neu ra trong chucmg 1 nhu phin tien de cho cac vin de duqc gill quyet trong chtrcmg tiep theo.

V6i kiln tic dung, mpg VANET bj anh huong hieu 'ging lon nhit bdri cac gill phap truyen thong. Cac phuang phi') do va tong hqp cac phi') do la nhung nguyen tic nen tang cho tiAp c#n xay dung, dish gia cic m6 hinh truyen thong tree cat img

dung phoS hien cart VANET.

Cac img dung dam bao an toim la mOt trong cac raw tieu then chOt va d#c tha cart he thong truyen thong VANET. Vol m8 hinh hqp tic giao thong, cac giai phi!) dua tren he thong lchach chi, cac he thong ngang hang, vi cac giao dip gifts xe vai xe duqc the hien qua cac phmmg an ky thu#t, phuong an tap hqp du lieu va tic thtgit toin dieu lchien nhim dua tic tinh toin nay vito mai trutrng ting dung thuc te.

cac kiln thuc thu nh#n duqc thong qua qui trinh nghien tiro va tam tit thong tin, em by vong se dip tic tap cAn cac yin de quan tong trong trien khai VANET trong m8i tru6ng thuc to nhu: Cic tic dung du doan, nhau xa, to dOng tam kiem truy

nhp, v..v.

THUAT NGIYVLET TAT

Thu#t ng& fling vi§t

Thutit lige fling anh

Tir vier tit

ASTM Hiep KA 4t lieu vi thir nghiem Hoa ICS, American Society for Testing and Materials

CAMP TO chirc do luting an tan va chum Crash Avoidance Metrics Partnership

Mpg khu vvc dieu khien Controller-Area Network CAN

Phan ph6i bang barn

Distributed Hash Table

DHT

Giao attic Ian truyin có huong Directional Propagation Protocol DPP

Mang tre tong the Delay Tolerant Network DTN

Accredited Standards Committee ECDSA Dugs tong nhOn NM tly ban tieu chain

Den NW phanh Wien cep EEBL Emergency Electronic Brake Light

Phuang tien th6ng minh Intelligent Vehicle Initiative IVI

NHTSA Ban quan l}+ an toil.' giao thong doing b0 my US National Highway Traffic Safety Administration

Nha sin xuit thiet bj g6c Original Equipment Manufacturer OEM

PROMETHEUS

Chuang trinh cho giao thong Chau Au yeti Hieu qui an town cao nhit Programme for European Traffic with Highest Efficiency and Unprecedented Safety

Thiet bj ben duang Road Side Equipment RSE

Dan vi ben &Zing Roadside Unit RSU

SODAD Phan down du lieu triru ttrang vi ph6 bien Segment-Oriented Data Abstraction and Dissemination

THU 1AT NGCT VIET TAT

Da truy nhap_phan chia theo th6i Time Dision Multiple Access TDMA gian

TESLA Nhan clang ten that tin the theo luting thin gian Timed Efficient Stream Loss- Tolerant Authentication

Traffic Information System TIS HO thong thong tin giao thong 'KT tic

TWA gian sting Time To Live TFL

Mang xe cO Mt dinh Vehicular Ad Hoc Network VANET

Tich licrp ha tang xe cO Vehicle Infrastructure Integration VII

VSC Truyen thong an town phuang tier' The Vehicle Safety Communication

WAVE Truy cap Irh8ng day tong moi tnerng xe cO Wireless Access in Vehicular Environment

Wireless Local Area Mang LAN Wing day WLAN Network

TAI LIW THAM KHAO

TALI (cid:9) LifIJ THAN" KHAO

[1] Vehicular Applicattions and Inter - Networking Technologies — Harms

Hartenstein and Kenneth P. Laberteaux.

[2] Gig phip can bang tai sir dung cliu frac thu muc cho mpg ngang hang co

cau trac cult Da Cao Minh.

[3] Trang web http://vi.wildpedia.org