Nhóm 07 - Bai Bao Cao Chuyen De Thong Tin Quang (ĐTVT 11)

7/28/2019 Nhm 07 - Bai Bao Cao Chuyen De Thong Tin Quang (TVT 11)

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Nng,Thng 02 nm 2013.

B GIO DC V O TO

HC VIN CNG NGH BU CHNHKHOA: in T Vin Thng

Ngnh: K Thut in T - Truyn Thng

BI TP BO COMn: Chuyn Thng Tin Quang

Ti: Kt Hp K Thut Radio Over Fiber v mng truy nhpkhng dy.

Gio Vin Hng Dn : GV.Ths Trng Xun TrungSV nhm 7 thc hin : Lng Vn Nghip (29)

: Trn nh Giang (18)

Lp : 11CQVT09 N ( TVT11)

Kha : 20011- 2013


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Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.

MC LC1 Chng 1:.....................................................................................................................7

1.1 Radio over Fiber nh ngha:.........................................................................................71.1.2 Cc thnh phn c bn ca tuyn quang s dng RoF................................................7

1.1.3 Tuyn RoF.................................................................................................................81.2 Xu th mng truy nhp v tuyn hin ti :........................................................................81.2.1 Mng truy nhp v tuyn hin ti..............................................................................81.2.2 S kt hp gia si quang v v tuyn.......................................................................81.2.3 Cc c im quan trng ca mng RoF...................................................................9

1.3 K thut RoF M u:.................................................................................................101.3.1 Gii thiu v truyn dn RoF...................................................................................101.3.2 K thut truyn dn RoF..........................................................................................101.3.3 Kt lun chng 1....................................................................................................11

Chng 2: ............................................................................................................................12

KT HP K THUT RADIO OVER FIBER V MNG TRUY NHP KHNG DY...............................................................................................................................................122.1 Gii thiu........................................................................................................................122.1 Gii thiu. .12.1 Gii thiu. Gii thiu.dng kthut Rdio over Fiber vo

mng truy nhp khng dy........................................................................................122.2 Mng v tuyn cellular da trn k thut RoF................................................................12

2.2.2 Tnh a dch v ca mng RoF kt hp k thut WDM.........................................132.3 RoF trong WLAN bng tn 60Ghz Giao thc MAC................................................14

2.3.1 Gii thiu.................................................................................................................142.3.2 Kin trc mng........................................................................................................15

2.3.3 M t giao thc MAC Giao thc bn c...............................................................172.4 K thut RoF trong mng truyn thng Road Vehicle....................................................202.4.1 Gii thiu.................................................................................................................202.4.2 Kin trc mng........................................................................................................21

..............................................................................................................................................232.4.3 Hot ng c bn trong mng..................................................................................232.4.4 MAC qun l tnh di ng chuyn giao.............................................................252.4.5 Kt lun chng 2....................................................................................................28

2.5 Tng kt..........................................................................................................................28Ti liu tham khoGSM System Enginr, Asa Mehrotra. Artech House, Inc.

Boston, London, 1997..................................................................................................32

DANH MC CC K HIU - CC CH VIT TT

SV Nhm 07 Thc Hin - Lp - H TVT11. GVHD.Ths Trng Xun Trung. Trang 2


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AMC Adaptation Modulation and Coding B iu ch v m hoAMPS Advanced Mobile Phone Service Dch v di ng tin tinAP Access Point im truy cpBB Base Band Bng tn c sBPF Band Pass Filter B lc bng thngBPSK Binary Phase Shift Keying Kho dch pha nh phnBWAN Broadband Wireless Access Network Mng truy nhp v tuyn bng

rngCDMA Code division Multiple Access a truy cp phn chia theo mCS Central Station Trm trung tmCSPDN Circuit Switched Data Network Mng chuyn mch d liuDFB Distributed Feed Back(laser) Laser hi tip phn tnDMOD DeMODdulator B gii iu chDWDM Dense Wavelength Division Multiplexing Ghp knh theo bc sng mt

caoEA Electro Absorption B hp th electronEAM Electro Absorption Modulator B iu ch hp th electron

EAT Electro absorption Transceiver B thu pht hp th electron

EDFA Erbium Droped Fiber Amplifier B khuych i si quangEOM External Optical Modulator B iu ch ngun quang ngoiFDD Frequency Division Duplexing B ghp knh chia tn sFDM Frequency Division Multiplexing B a cng chia tn sGSM Global System for Mobile Communication H thng thng tin di ng ton

cuHSCSD High-Speed Circuit-Switched Data Chuyn mch d liu tc caoIEEE (Institute of Electrical and Electronics

Engineers).

Vin k s in v in t

IF Intermediate Frequency tn s trung tnITS Intelligent Transportation System H thng giao thng thng minhLAN Local area network Mng ni b

LO Laser Ocsillator B dao ng laserMAC Medium Access Control S iu khin truy nhp mi

trngMH Mobile Host Thit b di ngMOD MODulator B iu chMSC Mobile Switching Center Trung tm chuyn mch di ng

MZM Mach-Zehnder Modulator B iu ch Mach-ZehnderNLOS Non line of sight Tia khng theo ng thngOADM Optical add/drop multiplexer B xen r sng quangOFDM Orthogonal Frequency Division

Multiplexing giaoGhp knh theo tn s trc

OFDMA Orthogonal Frequency Division MultipleAccess

a truy cp theo tn s trc giao

OSSBC Optical Single-Side-Band Modulation iu ch quang n bin



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PSPDM PACKET SWITHCHED DATANETWORK

Mng chuyn mch gi d liu

PSTN Public Switching Telephone Network Mng chuyn mch in thoicng cng

QAM Quadrature Amplitude Modulation iu ch bin vung gc

QoS Quanlity of Service Cht lng dch v

QPSK Quadrature Phase Shift Keying iu ch kho pha vung gcRF Radio Frequency Tn s v tuynRoF Radio over Fiber K thut truyn sng v tuyn trn

si quang



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LI NI UMng truy nhp l nt cui cng trong mng vin thng, l thnh phn giao tip vi con

ngi trong qu trnh a dch v ti ngi s dng cui v l thnh phn tt yu ca mng.

Hin nay, mng truy nhp ang ngy cng pht trin khng ngng vi nhiu loi hnh khc

nhau nh mng truy nhp cp ng, mng truy nhp si quang, mng truy nhp v tuyn,

Mi loi hnh ca mng u c nhng c im khc nhau, tuy nhin mng truy nhp v tuyn

ang c nhiu nht v pht trin mt cch nhanh chng m chng ta c th thy c

chung quanh nh mng thng tin di ng 2G, 3G, mng LAN khng dy cho cc kt ni trong

nh vi tn gi WiFi m cnh tranh vi n c th l cng ngh HSPA (High-Speed Packet

Access) da trn nn 3G c s h tr ca AT&T. Hay thm ch cc mng NGN ngy nay

cng c pht trin theo chiu hng h tr wireless. l nh nhng u im vt tri cak thut khng dy mang li, t tnh di ng cao m cc k thut truy nhp hu tuyn khng

th c c. Mc khc, vi s pht trin ca mng truy nhp bng thng rng th mng truy

nhp v tuyn gn bt u gp phi nhng nhc im ca mnh, tc thp vi vng ph

sng hp. V vy, ngy cng c nhiu cng ngh v k thut c nghin cu v pht trin

khc phc nhc im ny, mang li cho ngi dng mt mng truy nhp v tuyn bng thng

rng.

Bn cnh , si quang ngy nay cng ang c s dng tr nn ph bin hn bi uim l bng thng rng. Tuy c nhng nhc im nht nh trong lp t, bo dng cng

nh gi thnh ca si quang v thit b i km cn t hn so vi cp ng nhng vi bng

thng ln ca si quang th khng c mt mi trng no c th so snh c. V vy, si

quang c xem l c s trin khai cc mng bng thng rng m hin ny ta c thy c

nh mng ng trc, FTTx, cc ng dng trn si quang ngy cng nhiu.

Mt trong nhng phng php t c mng truy nhp v tuyn bng thng rng l kt

hp vi k thut truy nhp bng si quang, vi u im l bng thng ln v c ly xa. Mt

trong nhng s kt hp l k thut Radio over Fiber, mt k thut m hin nay c coi l

nn tng cho mng truy nhp khng dy bng thng rng trong tng lai.



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Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.Hc tp v nguyn cu mn hc, chuyn thng tin quang mang li cho sinh vin nghnh

in t vin thng c kin thc mi v c s lnh vc sau ny cng nh tip cn cc gii php

k thut v cng ngh mi.

V vy, trong chuyn ny, nhm chng em s tm hiu v K thut Radio over Fiber

cng nh nhng ng dng ca n trong mng truy nhp v tuyn

. Ni dung ca chuyn bao gm 2 phn:

Tm hiu v k thut Radio over Fiber.

Kt hp k thut Radio over Fiber v mng truy nhp khng dy.

thc hin nhng yu cu ra ca chuyn , cc vn trn s ln lt c trnh

by trong cc chng.

Chng 1: Ni v k thut Radio over Fiber, k thut l g v v sao c k thut ny.

Chng ny s tm hiu cc k thut truyn dn sng radio qua mi trng l si quang.

mi k thut s c nhng u nhc im ring ca n, ty vo nhng u nhc im ring m

n cng s c nhng ng dng trong tng mi trng c th, s so snh cc u nhc im ca

mi k thut s c a ra.

Chng 2: Cc ng dng ca k thut Radio over Fiber trong mng truy nhp v tuyn s

c trnh by c th trong 2 mng c th l mng wireless LAN dng bng tn mm v mng

truyn thng RVC c s h tng ca mng ITS. Qua kin trc ca mng Radio over Fiber s

c m t trong mi phn cng nh nhng kh khn v vn cn khc phc. c bit l tnh

a dch v ca k thut RoF trong cc kin trc mng nn cc dch v s c trin khai mt

cch linh hot v d dng hn trn cng mt mng.

Phn cui cng dnh tng kt nhng vn lm c trong chuyn cng nh hn

ch v hng pht trin ca ti.

Trong qu trnh nguyn cu ti mc d nhm chng em c gng nhiu nhng do trnh

v thi gian c hn nn khng th trnh khi nhng sai st, nhm chng em rt mong nhnc s ph bnh, hng dn v gip ca Thy, bn b.

Nhm em xin chn thnh cm n s gip tn tnh ca Thy Ths Trng Xun Trung

trong thi gian qua nhm chng e hon thnh tt ti nhm.

Nng, Ngy 24 thng 02 nm 2013



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1Chng 1:K THUT RADIO OVER FIBER

1.1 Radio over Fiber nh ngha:

1.1.1 nh ngha.RoF l phng php truyn dn tn hiu v tuyn c iu ch trn si quang.

RoF s dng cc tuyn quang c tuyn tnh cao truyn dn cc tn hiu RF (analog)

n cc trm thu pht.

1.1.2 Cc thnh phn c bn ca tuyn quang s dng RoF.

Mobile Host (MH): l cc thit b i ng trong mng ng vai tr l cc thit bu cui. Cc MH c th l in thoi i ng, my tnh xch tay c tch hp chc nng, cc

PDA, hay cc my chuyn dng khc c tch hp chc nng truy nhp vo mng khng dy.

Base Station (BS): c nhim v pht sng v tuyn nhn c t CS n cc MH,

nhn sng v tuyn nhn c t MH truyn v CS. Mi BS s phc v mt microcell. BS

khng c chc nng x l tn hiu, n ch n thun bin i t thnh phn in/quang v

ngc li chuyn v hoc nhn t CS. BS gm 2 thn phn quan trng nht l antenna v

thnh phn chuyn i quang in tn s RF. Ty bn knh phc v ca mi BS m s lng

BS ph sng mt vng l nhiu hay t. Bn knh phc v ca BS rt nh (vi trm mt hoc

thp hn na ch vi chc mt) v phc v mt s lng vi chc n vi trm cc MH. Trong

kin trc mng RoF th BS phi rt n gin (do khng c thnh phn).

Central Station (CS): l trm x l trung tm. Ty vo kh nng ca k thut RoFm mi CS c th phc v cc BS xa hng chc km, nn mi CS c th ni n hng ngncc BS. Do kin trc mng tp trung nn tt c cc chc nng nh nh tuyn, cp pht knh,u c thc hin v chia s CS v th c th ni CS l thnh phn quan trng nht trong

mng RoF (cng ging nh tng i trong mng in thoi). CS c ni n cc tng i,server khc.

Mt tuyn quang ni gia BS v CS nhm truyn dn tn hiu gia chng vi nhau.

Cc thnh phn ca mng c biu din nh hnh v 1.1.



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1.1.3 Tuyn RoF.

Mt tuyn RoF c kin trc nh trn hnh s bao gm t nht l thnh phn bin i sng v

tuyn sang quang, thnh phn chuyn i quang thnh sng v tuyn, mt tuyn quang (song

hng hay n hng). Cc thnh phn thuc kin trc RoF khng c chc nng quang nh

n-ten thu pht v tuyn thuc phn v tuyn, chc nng x l giao tip ca CS thuc phn

mng ta khng xt y.

K thut RoF c kho st y bao gm tt c cc k thut pht v truyn dn sng

radio t CS ti BS trn si quang v ngc li.

Hnh 1.1 CS BS MH mt microcell trong kin trc RoF

1.2 Xu th mng truy nhp v tuyn hin ti :

1.2.1 Mng truy nhp v tuyn hin ti.

Mng truy nhp v tuyn hin nay c th c chia lm 2 loi l v tuyn di ng (mobile)

nh mng thng tin di dng 1G, 2G, 3G, WiMax v v tuyn c nh (fixed) nh WiFi.

Trong cc mng ny th ngi ta ch nht n 2 yu t l bng thng v tnh di ng. So

vi mng c nh th mng mobile c tnh di ng cao hn nhng b li th bng thng ca n

li thp hn, tnh di ng cng cao nhng vn cn trong giai on th nghim nh s dng cc

k thut mi tin tin hn. Nh vy ta thy rng xu hng ca cc mng v tuyn ngy nay l

tnh di ng v bng thng ngy cng tng t c mng bng thng rng .

1.2.2 S kt hp gia si quang v v tuyn.

t c mng bng thng rng, ngy nay cc cng ngh truy nhp v tuyn ang

hng dn v kin trc mng cellular, tng tnh di ng cho cc thit b trong mng. Trong khi

tng bng thng th ngi ta p dng cc k thut truy nhp tin tin hn nh CDMA,


E/O

O/E

SOURCE

O/E

E/O

Am

CSMOBILE

MOBILE

MHBS


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Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.OFDM, v c xu hng, a.gim kch thc cc cell li tng s user ln do s lng trm

thu pht tng ln theo, b. chuyn sang hot ng bng tn microwave/milimeterwave (mm-

wave) trnh s chng ln ph vi cc bng tn sn c v m rng bng thng hn na. Hai

xu hng trn c tc ng qua li mt cch cht ch. i vi bng tn mm ngoi nhng u

im ca n nh: kch thc nten nh, bng thng ln, tuy nhin tn s mm suy hao ca n

trong khng gian rt ln do i hi nhiu BS th r rng gi thnh ca mi BS s l mt vn phi gii quyt trong bi ton kinh t. gim gi thnh cho cc BS th ngi ta a. cu trc

BS tht n gin b. a ra kin trc mng tp trung. Vi kin trc mng tp trung, cc chc

nng nh x l tn hiu, nh tuyn, chuyn giao, nh tuyn, c thc hin ti trm trung

tm CS (Central Station), mi CS ny phc v cng nhiu BS cng tt, nh kin trc tp trung

ny th r rng cc BS tht s n gin, nhim v ca chng by gi ch cn l pht cc tn

hiu v tuyn nhn c t CS v chuyn cc tn hiu nhn c t MH (mobile host) v CS.

So vi cc BTS trong mng cellular tm hiu chng 1 th cc BS c chc nng n gin

hn nhiu v ngoi chc nng thu pht sng thng thng th cc BTS ny c thm chc nng

x l tn hiu (gii iu ch ri truyn v cc BSC bng lung T1/E1 c ni bng cp quang

hay v tuyn).

kt ni CS vi cc BS, ngi ta s dng si quang vi nhng u im khng th thay

th c l bng thng ln v suy hao b, mi si quang c th truyn c tc hng

trm Gbps vi chiu di ln n hng chc km. Cc k thut truyn dn tn hiu v tuyn t

CS ti BS v ngc li c gi l k thut RoF. Cn mng truy nhp v tuyn da trn k

thut RoF c gi l mng truy nhp v tuyn RoF m ta s gi tt l mng RoF.

1.2.3 Cc c im quan trng ca mng RoF.

Cc chc nng iu khin nh n nh knh, iu ch, gii iu ch c tp trung

CS nhm n gim ha cu trc ca BS. Cc BS c chc nng chnh l chuyn i

quang/in, khuch i RF v chuyn i in quang.



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Kin trc mng tp trung cho php kh nng cu hnh ti nguyn v cp bng thng

ng (thnh phn ny c th s dng bng thng thnh phn khc nu bng thng thc s

ri) cho php s dng bng thng hiu qu hn. Hn na nh tnh tp trung nn kh nng nng

cp v qun l mng n gin hn.

Do cu trc BS n gin nn s n nh cao hn v qun l s BS ny tr nn n

gin, ngoi tr s lng ln.

c bit l k thut RoF trong sut vi cc giao din v tuyn (iu ch, tc bit,)

v cc giao thc v tuyn nn mng c kh nng trin khai a dch v trong cng thi im.

Nu khc phc cc nhc im trong RoF th mt CS c th phc v c cc BS rt

xa, tng bn knh phc v ca CS.

1.3 K thut RoF M u:

1.3.1 Gii thiu v truyn dn RoF.

Khng ging vi mng truyn dn quang thng thng, cc tn hiu c truyn i

thng dng s, RoF l mt h thng truyn tn hiu tng t bi v n chuyn ti cc tn

hiu dng v tuyn t CS ti BS v ngc li. Thc t th cc tn hiu truyn dn c th dng

v tuyn RF hay tn s trung tn IF hay bng tn gc BB. Trong trng hp tn hiu IF hay BB

th c thm cc thnh phn mi a t tn s BB hay IF ln dng RF BS. Trong trnghp l tng th ng ra ca tuyn RoF s cho ta tn hiu ging nh ban u. Nhng trn thc t

th di s tc ng ca cc hin tng phi tuyn, p ng tn s c hn ca laser v hin

tng tn sc trong si quang m tn hiu ng ra b sai khc so vi ng vo gy ra mt s gii

hn trong truyn dn nh tc , c ly tuyn. Hin tng ny cng nghim trng hn trong

tuyn RoF ny v tn hiu truyn i c dng analog, do cc yu cu v chnh xc l cao

hn so vi cc h thng truyn dn s. y l nhng kh khn trong trin khai k thut RoF .

1.3.2 K thut truyn dn RoF.



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Hnh 1.2 S dng phng php iu ch vi sng mang quang

Hnh v 1.2 gii thiu mt trong nhng cch truyn sng v tuyn trn si quang n

gin nht. u tin, tn hiu d liu c iu ch ln tn s v tuyn RF. Tn hiu tn s RF

ny c a vo iu ch (cng ) sang dng quang truyn i. y, ta s dng phng

php iu ch cng n gin nht l iu ch trc tip. Nh vy, sng v tuyn c iu

ch ln tn s quang, s dng tn s quang truyn i trong si quang. Ti pha thu, ta sdng phng php tch sng trc tip, tch thnh phn sng mang quang, a tn hiu quang

tr li dng in di tn s RF. Mt b lc thng thp pha cui u thu nhm lc nhng

nhiu gy ra trn ng truyn.

Cng trng in tE(t) trn si quang c biu din bi cng thc sau y:

+=

optj

RF etStE )()(

Trong SRF(t) l tn hiu cn truyn tn s v tuyn cha iu ch, opt l tn s quang

v l gc pha ca tn hiu quang.

1.3.3 Kt lun chng 1.

ng dng k thut RoF v mng WLAN hot ng bng tn mm l mt trong nhng ng

dng n gin ca k thut trn vo mng truy nhp v tuyn. Vi c ly nh, bn knh ph

sng cc picocell khng cn qu ln, gi thnh BS khng phi l qu t nn cc nhc im

ca sng mm tr nn khng ng k na, trong khi cc u im ca k thut nh kin trctp trung, bng thng rng, tnh di ng cao li c pht huy.

So vi mng WLAN thng thng th mng WLAN hot ng bng tn mm c nhiu

im khc nhau. T c im tn hao ln ca sng mm, s lng BS cn c lp t s nhiu

hn ph sng mi trng indoor. Trong nhiu mng tng t vi s lng cc micro cell

ln th vn qun l di ng l tht s quan trng. Vi giao thc MAC, gi l giao thc



12/33

CS

Lp vtuyn

Lp quang

MS

si quang

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.chuyn giao bn c, vi c tnh l nhanh vi chuyn giao n gin v tch hp QoS, n

c xut l giao thc trong mng WLAN hot ng bng tn mm ny.

Chng 2:KT HP K THUT RADIO OVER FIBER V MNG TRUY NHP KHNGDY2.1 Gii thiu.

2.1 Gii thiu. .12.1 Gii thiu. Gii thiu.dng kthut Rdio over Fiber vo mng truy nhp khng dy chng ny chng ta s kt hp mt mng truy nhp khng dy v k thut Radio over Fiber

xem chng khc v ging vi nhng mng truy nhp hin ti nh th no.Mng truy nhp

v tuyn kt hp k thut RoF ta gi l mng RoF Chng ta s tm hiu v kin trc mng RoF

nh th no v ng dng ca k thut RoF trong mng truy nhp v tuyn ra sao sau khi tm

hiu k thut RoF trong chng 1.

2.2 Mng v tuyn cellular da trn k thut RoF.2.2.1 a truy nhp 2 lp.

Trong mng truy nhp v tuyn s dng k thut RoF, lp vt l bao gm 2 lp con l

lp v tuyn v lp quang pha di. Lp quang by gi nh thnh phn trung gian a

cc tn hiu RF t tt c cc MS trong mng v CS. Lp CS s x l cc tn hiu v tuyn ny.

Hnh 2.1 m t 2 lp quang v v tuyn ca mng.

Hnh 2.3 Mng khng dy a truy nhp 2 lp



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Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.Trc ht, lp v tuyn, mi BS phi phc v rt nhiu MH, ng thi mi CS li phc

v rt nhiu BS, trong BS ch ng vai tr trung gian chuyn cc tn hiu t CS ti MS

v ngc li. Do , c th xem mi CS phc v gin tip rt nhiu cc MS. Nh vy mt k

thut a truy nhp (multiaccess) lp v tuyn c hnh thnh.

Cu trc mng n gin nht lp quang l cu trc mng hnh sao: cc tuyn RoF kt

ni point-to-point s kt ni CS vi mi BS bng mt si quang. Tuy nhin, cu trc ny gylng ph si quang nn ngi ta a ra nhiu cu hnh tt hn, nht l khi s lng BS l tng

i nhiu. Nu mt si quang phc v c nhiu hn mt BS, th lc lp quang cng tr

thnh mt h thng a truy nhp th hai, c lp vi lp a truy nhp v tuyn.

K thut a truy nhp lp quang l rt a dng, n c th s dng k thut SCM (FDMA),

CDMA, TDMA, WDM

2.2.2 Tnh a dch v ca mng RoF kt hp k thut WDM.

Hin nay, hu ht cc mng iu c thit k truyn ti cho mt dch v nn linh

hot ca mng khng cao. Th nht l do bng thng ca mng cha ln phc v

nhiu dch v cng mt lc. Th hai na l cc loi dch v khc nhau c cc chun khc

nhau, yu cu phi c mt k thut truyn dn trong sut vi cc k thut khc. Tuy nhin, k

t khi bng thng si quang c s dng hiu qu hn nh k thut WDM v tng ln nhiu

ln m c bit l k thut WDM trong sut vi tt c cc k thut truyn dn, chun iu ch,

nn mi si quang c th truyn ti nhiu loi hnh dch v khc nhau mt cch ng thi.

Cc tn hiu ca cc loi hnh dch v khc nhau c truyn ti trn cc bc sng khc nhau.

Tt nhin l cc dch v khc nhau phi c hot ng vi cc tn s khc nhau, kiu iu

ch RF khc nhau vi nhng cell khc nhau, vv Dch v cung cp c th l v tuyn c

nh hay di ng, dch v bng hp hay dch v bng rng, vv D , RoF c th c

ng dng trong mng truyn ti ca cc ng dng thng thng. Trong mng RoF a dch v

th mi dch v hot ng trn mt bc sng khc nhau, cc bc sng c chn la mtcch thch hp phc cho cc tn hiu t CS ti BS v ngc li. Ta c th xem mt v d

hnh



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Hnh 2.4 K thut WDM cho php trin khai a dch v trn mng

K thut RoF m ta nghin cu chng 1 l mt k thut truyn dn tn hiu v tuyntrn si quang sao cho tn hiu v tuyn truyn i c cng xa cng tt vi tuyn tnh cao

nht.

Trong nhng phn tip theo, ta s tm hiu xem, k thut RoF c kt hp vi mng truy

nhp v tuyn nh th no? N em li nhng li ch g? Nhng kh khn khi ng dng cho

mi mng v hng gii quyt ra sao?

3 kiu hnh mng c chng ta tm hiu y l:

Mng Wireless LAN Mng truyn thng Road Vehicle Communication (RVC)

2.3 RoF trong WLAN bng tn 60Ghz Giao thc MAC.

2.3.1 Gii thiu.

K thut RoF c ng dng cho mng WLAN s l mt trong nhng ng dng ha hn

nht, vi cc BS ch thc hin cc chc nng n gin v c kt ni n CS thng qua mt

si quang, cc chc nng nh tuyn v x l c tp trung ti CS. Tuy nhin, trong mng

WLAN ny, do bn knh ph sng ca cc BS nh nn mi s di chuyn ca MH s cn phi

c yu cu chuyn giao. Do s chuyn giao thc hin lin tc khi MH di chuyn nn trong

mng WLAN ny cn phi c mt giao thc chuyn giao n gin nhng phi tin cy bng



15/33

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.tn mm. Trong phn ny chng ta s cp ti giao thc MAC (media access control) c gi

l Chess Board Protocol (Giao thc chuyn giao bn c) c ng dng cho mng WLAN

s dng k thut RoF hot ng bng tn 60GHz, vi c tnh chuyn giao nhanh v n

gin, tch hp QoS. Vi kh nng iu khin tp trung ca mng RoF nn n ph thuc vo m

chuyn mch tn s FS (frequency switch) cung cp mt c ch chuyn giao n gin, v

cc picocell lin nhau c n nh cc m FS trc giao vi nhau trnh hin tng giao thoang knh. C ch ny cho php cc MH c th hiu chnh tn s trong sut qu trnh chuyn

giao, chnh l c tnh quan trng nht ca giao thc chuyn giao bn c.

2.3.2 Kin trc mng.

i vi mng WLAN, do cu trc mng cn n gin, cc thit b gi thnh r nn thng

mng s dng cc k thut cng n gin cng tt. i vi mng WLAN trong chng ny ta

gi s chng c c tnh sau: (1) song cng phn tn s v (2) kh nng thay i knh RF ng.

Hnh v 2.3 ch ra mt v d v kin trc RoF c ng dng trong mng WLAN.

Vi kin trc ny, mng s dng phng php iu ch sng mang con, phng php n

gin v c th s c s dng rng ri trong mng RoF. Trong k thut ny, d liu t tuyn

truyn dn theo hng downlink (t CS ti MH) u tin c iu ch ln min tn s RF

thch hp bi mt ngun v tuyn (c gi l subcarrier) sau mi c iu ch ln min

quang (c gi l maincarrier) bng mt ngun quang. Tn hiu ny c truyn trn si

quang n BS, y cc tn hiu quang li c chuyn v thnh tn hiu v tuyn v c

pht i t BS n cc MH. i vi tuyn uplink (t MH n CS) th cc tn hiu nhn c

BS s c iu ch sang min quang bng mt ngun quang. N c truyn dn thng qua

tuyn quang ti CS v c gii iu ch sang tn hiu v tuyn y bi PD. Sau cc d

liu ca mi user s c tch ra. Do c im ca mng WLAN l khong cch t BS n cc

CS l khong vi trm mt nn nh hng ca cc hin tng phi tuyn ln tn s RF l tng

i thp, v th tn hiu truyn trn si quang c truyn tn s RF. Hot ng c m ttrong hnh 2.3.



16/33


Hnh 2.3 Kin trc mng RoF cho WLAN

Vi kin trc cho mng WLAN ny th mi CS s c rt nhiu b thu pht (TRX) bng vi

s lng ca BS, v mi b thu pht bao gm (1) ngun sng pht tn hiu nh laser, (2)

mt PD cho hng uplink (3) v mt modem pht v nhn d liu min RF. Nhn vo cu

hnh trn ta cng thy rng BS ch c nhng chc nng n gin l thu v pht tn hiu, ngoi

ra khng c chc nng x l tn hiu no c thc hin BS. i vi mng WLAN chng ta

ang kho st th cc b iu ch ngoi c s dng thay cho cc LD v chng hot ng

tn s 60GHz, tn s m cc LD khng th p ng kp. Cc b thu pht c th c trang b

cc b dao ng c th iu chnh c nhng v gi thnh cao, nn i khi chng c trang

b cc b dao ng vi tn s c nh. S thay i b giao ng s nh hng n qu trnh

phn b tn s cho mng RoF ny.



17/33


Hnh 2.4 Hng downlink

2.3.3 M t giao thc MAC Giao thc bn c.

a. Gii thiu

Hnh 2.5 Giao thc chuyn giao bn c.

Nh ta bit, trong mng WLAN ph sng mt ta nh (building) th mi phng s c

ph sng bi t nht mt BS, gi l mt picocell. Do bn knh mi picocell l tng i nh

nn ta nh s c ph sng bi rt nhiu cc picocell, do qun l tnh di ng ca cc

thit b trong mng l mt iu rt cn thit. Trong mng WLAN, ta gi s mng s dng mng


MHs

CS RoF link

BS

fopt

fRF


18/33

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.hot ng ch song cng phn tn s FDD (Frequency Devision Duplex), do cc thit b

s dng bng phng php ny n gin, r tin v ang c pht trin rt thnh cng. Bng

cch phn chia bng thng tng ca h thng thnh 2n knh vi n knh downlink c k hiu

lf1, f2, , fn v n knh uplink c k hiu l fn+1, fn+2, , f2n. Ch rng bng thng, b rng

ph mi knh tn s, ca tuyn downlink v uplink l khng ng nht, khng ging nhau, v

vy mng c kh nng h tr lu lng bt i xng. Hn na, trc thi gian cng c th cchia thnh cc cc khe thi gian (time slot) bng nhau v n khe thi gian c nhm li thnh

mt mt khung. Hnh 2.5 m t khung thi gian vi n=10.

b. M t giao thc.

Trc ht, khi MH tham gia vo qu trnh truyn d liu, n s c n nh mt cp

knh tn s no trong 2n knh v tuyn m mng WLAN h tr (fi, fn+i) i=1, 2, 3, ,n v

mt cp khe thi gian (tk, tk+1) tun hon chu k n cho tuyn downlink v uplink (xem hnh).

Khi MH nhn c tn hiu cho php truyn t knh downlink fi trong khe thi gian tk th n

c php truyn dn cc gi thng qua knh uplinkfi+n trong khe thi gian k tip tk+1. Mi BS

u h tr cc knh (tn s kt hp khe thi gian), tuy nhin mi chng ch c s dng

nhng khe thi gian quy nh sn. Trong hnh v l mt v d vi n=5. Trong mi khung thi

gian, mi khe thi gian trong n khe ch c s dng ng 1 ln. Cc picocell k nhau khng

c s dng li knh (c quy nh bng mt m FS) trnh hin tng nhiu giao thoa

ng knh. Mt m FS ch c s dng bi mt picocell v c th c s dng li bi mt

picocell khc khi khong cch ca chng ln trnh hin tng giao thao tn hiu. Mt

vn quan trng trong giao thc ny chnh l vn ng b. Do s dng phng php

TDM nn vic ng b gia cc thit b l khng th thiu, tuy nhin vn ng b tn s v

khe thi gian tng i n gin. Vi giao thc ny, vic ng b phi c thc hin trn

ton b cc picocell, tc l cc picocell cng phi c ng b khe thi gian vi nhau, vic

ng b cc cell tht s n gin nh kin trc tp trung, CS s m nhn vai tr ng b ny.

ng b vi cc BS, cc CS bt u o khong thi gian truyn tn hiu n BS ri truyn

ngc v CS (round-trip time) gi l RTT. Lc CS c th n nh c khong thi gian

truyn t BS ti CS l RTT/2 ng b cc BS.

Giao thc chuyn giao bn c c ng dng nhiu trong mt s h thng s dng

phng php nhy tn nh BlueTooth thng thy cc in thoi di ng ngy nay. Tuy

nhin trong mng WLAN giao thc chuyn giao bn c c mt s im khc bit: (1) trong h



19/33

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.thng nhy tn th cc BS v MH s thay i knh tn s theo mt quy lut cho trc (gi l

m gi ngu nhin), tuy nhin trong giao thc bn c th ch c cc BS hiu chnh tn s ca n

cn MH vn gi nguyn cp tn s hot ng ca n, (2) giao thc chuyn giao bn c c

kt hp vi kin trc mng tp trung CS nn c trnh c hin tng nhiu giao thoa ng

knh, trnh c vic s dng 2 tn s chuyn mch cng nhau trong cc picocell gn nhau.

Do trong h thng WLAN s dng giao thc bn c ngi ta thng s dng khi nimchuyn i tn s (frequency swiching) thay cho khi nim nhy tn (frequency hopping).

c. Chuyn giao.

Mt c im quan trng ca giao thc bn c ny l qu trnh chuyn giao khi MH di

chuyn t BS ny sang BS khc l rt n gin v nhanh. Thi gian chuyn giao ch mt ti a

(2n+1) khe thi gian. Nh s n gin v nhanh nn giao thc c s dng trong mng

WLAN, gim bt s phc tp ca cc MH. Ta s tm hiu mt v d chuyn giao khi MH di

chuyn t BS ny sang BS khc nh hnh v di. Trong hnh 2.6 l v d vi n = 5.

C ch chuyn giao xy ra nh sau: trc ht cell c cc MH nhn tn hiu cho php

khung thi gian c t mu en v tr li li bng ti cc khe thi gian c ng gch cho (

c m t trong giao thc bn c). Lc ny MH s s dng cp tn s (fi, fn+i) cho 2 chiu up

v down. Gi s MH di chuyn t picocell c sang picocell mi th n vn s dng cp tn s

ny cho truyn d liu. Tt nhin l khi qua cell khc, do tnh trc giao (c iu khin bi

CS) nn n s hot ng khe thi gian khc do vn khng thay i cp tn s (c im ca

giao thc chuyn giao bn c ). Khi n n vng bin gii ca c 2 picocell th n ng thi

nhn c c 2 khe thi gian ca c 2 picocell. Khi n cng s tip tc lin lc vi picocell

c cho n khi thit lp knh mi vi picocell mi c thnh lp. Khi lin lc vi picocell c

tht s b mt do i qu tm ph sng th n mi bt u yu cu picocell mi cp cho n mt

knh hot ng, cng vic ny c MH chun b t khi nhn c tn hiu ca picocell

mi (xem hnh). Vic cp bng thng cho MH s c thc hin khung tip theo. Nhn vo

hnh v 2.6, ta thy thi gian chuyn giao ti thiu l 2n +1 khe thi gian.



20/33


Hnh 2.6 tr chuyn giao trong giao thc chuyn giao bn c.

Gia nhp vo mng WLAN: Khi mt MH mi bt u gia nhp vo mng WLAN th cng

vic u tin ca n l ng b vi CS, sau n chn mt knh bt k ngu nhin nu n c

kh nng thay i knh tn s hoc l s dng mt knh nh trc nu n khng c kh nng

thay i knh. Sau n lng nghe nhng khe thi gian tuyn downlink. N s nhn c

mt tn hiu trong khe thi gian no ca khung v n nh khe thi gian cho MH hot ng.

Sau khi nhn c gi tin n nh khe thi gian, n s bt u gi tn hiu xc nhn ngay khe

tip theo trong tuyn uplink gia nhp vo mng. Sau n bt u truyn nhn d liu trn

knh c n nh nh c m t trong phn giao thc.

2.4 K thut RoF trong mng truyn thng Road Vehicle.

2.4.1 Gii thiu.

Mng truyn thng Road Vehicle (Road Vehicle Communication RVC) l c s h tng ca

mng ITS (intelligent transportation system), c ng dng cho cc phng tin ang dichuyn c th truy cp vo mng, t cc phng tin tr thnh nhng thnh phn ca mng

thng tin, chng c th lin lc vi nhau c s dng trong vic iu khin cc phng tin

mt cch t ng bi trung tm. Nhng yu cu ca h thng RVC ny l phi t c tc

t nht 2-10Mbs cho mi MH nu cn. Hn na, mng phi khng ch h tr thoi v d liu

m cn phi h tr cc dch v a phng tin nh video thi gian thc khi cc MH ang di



21/33

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.chuyn. T nhng mng thng tin di ng cellular hin ti v pht trin ln bng tn micromet

nhng vn khng th no cung cp bng thng, do cc bng tn mm trong khong t

36GHz n 60GHz ang c xem xt, ci tin ng dng cho mng RVC ny. Tuy di bng

tn ny c bng thng cao hn so vi bng tn micromet, nhng bn knh ph sng ca cc cell

nh hn do suy hao trong khng gian. Do c tnh ca mng RVC l s lng BS ln

ph sng hon ton mi ni v s lng ngi s dng ln, h tr tnh di ng. Nh vy kintrc mng cn cc yu cu chnh sau: (1) mng phi c gi thnh tt v (2) tch hp kh nng

chuyn giao nhanh v n gin phc v mt s lng cc user.

Tuy nhin, trong RVC th mt th tc chuyn giao nhanh thc hin kh hn rt nhiu so vi

mi trng indoor, nht l tc d liu cao ln tc di chuyn. thc hin c kh

nng ny, h thng phi c c ch qun l chuyn giao thc hin vic chuyn giao lin tc

v chnh xc. Ta c th ly mt v d l mt chic xe ang di chuyn vi vn tc 100km/h, th

vi bn knh cell l khong 100m th s chuyn giao thc hin mi 3.6s mi ln. Nu vng

chng ln gia 2 cell l 10m th yu cu chuyn giao phi c thc hin trong 0.36s. Trong v

d ny ta thy c trong mng RVC cn mt th tc chuyn giao nhanh v n gin p

ng yu cu di chuyn nhanh ca cc MH. ng thi, trong kin trc mng th phi tnh ton

n vng chng ln ca 2 cell ln sao cho chng c thi gian chuyn giao v cng khng

c qu nh khin cho s lng BS tng ln, khng c li trong vic qun l cng nh gi

thnh mng tng. Trong chng ny ta s c tm hiu th tc MAC thc hin chuyn giao

trong mng RVC c ng dng k thut RoF vi c tnh l chuyn giao nhanh v c bit l

kh nng cp bng thng ng. N c thc hin da trn kh nng iu khin tp trung ca

mng RoF qun l tnh di ng mt cch hiu qu.

2.4.2 Kin trc mng.

H thng RVC s dng k thut RoF c th hin trong hnh 2-7, y mi BS c kt

ni lin tc n mt s lng BS thng qua si quang, v mi BS y l loi phc v chomng RVC vi tm ph sng rng v cc c tnh ph hp mng. chng ny ta ch kho st

cc con ng mt chiu, vi hng di chuyn ca MH c CS bit trc. i vi cc

ng nhiu chiu, ng dng c th trin khai trong thnh ph. Cc CS c kt ni n mng

ng trc, mng ng trc c th l mng PSTN hay l mng Internet. Mi BS s ph sng

mt khu vc m ta gi l cell (khng gi l picocell nh trong mng WLAN na). Do c tnh



22/33

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.ca sng mm bng tn 36GHz cho n 60GHz c suy hao ln nn bn knh ca mi mi cell

ch nm trong khong t vi chc n vi trm mt v s lng BS ph sng nguyn con

ng l kh ln. t c kin trc tp trung v cu trc BS n gin vi tm ph sng

CS ln th nhiu k thut RoF c tho lun trong chng 2 s c ng dng vo mng v

hin nay ngy cng c ci tin. Tuy nhin trong chng ny, ta ch tho lun v kin trc

mng, cn cc k thut c p dng nh th no trong mng c tho lun chng1. Kin trc mng RVC s dng k thut RoF c th hin trong hnh 2.7

Hnh 2.7 Mng RVC da trn k thut RoF.

Phng php truyn dn tuyn uplink v downlink c ni chng 1. Da vo hnh

v ta thy cu trc BS rt n gin ch gm mt PD, mt LD, mt EOM v c th c mt b

khuch tn s RF. BS khng thc hin bt c mt chc nng x l tn hiu no, n ch ng vai

tr trung gian chuyn ti sng RF gia BS v MH. Mi CS s c rt nhiu b thu pht TRX

(transceiver), mi TRX phc v cho mi BS. TRX c th c trang b b dao ng c tn s

c nh hay c th iu chnh c. Vi b dao ng RF iu chnh c tn s th h thng c

kh nng n nh ti nguyn mm do hn.



23/33


Hnh 2.8 Kin trc mng RVC da trn k thut RoF.

2.4.3 Hot ng c bn trong mng.

Gi s CS c kt ni n N BS nh trong hnh v 2.8, v s lng BS ph sng hon

ton con ng. N BS ny s c chia lm S nhm (1 < S < N), trong tp hp cc BS trong

mt nhm c t gn nhau, v tp hp cc vng ph sng ca nhm c gi l VCZ

(vitual cellular zone). TDMA c s dng trong h thng vi cc super-frame c kch thc

c nh, bao gm M khe thi gian m mi khe c n nh cho mi VCZ, mi khe c lp

y mt gi d liu c kch thc ti thiu. Knh RF bn trong mt VCZ cng tng t, v ccVCZ lin k khng c dng chung knh RF trnh hin tng giao thao ng knh. Do

khi mt MH ang di chuyn trong cng VCZ th chng khng nht thit phi i knh tn s.

N ch phi thay i knh RF khi chuyn sang VCZ khc. Mi super-frame c chia thnh

cc frame nh hn cho cc cell bn trong VCZ, m mi khung bao gm c knh uplink ln

downlink. Kch thc mi khung c th c thit k sao cho cn i vi lu lng ca mi

cell.



24/33


Hnh 2.9 n nh khung trong khi di chuyn.

Hnh 2.9 m t mt VCZ bao gm 3 cell v 3 frame c n nh cho mi cell trong

min thi gian nh th no khi s dng cng mt knh RF. iu cn c nhn mnh y l

trong mi chu k ca khung i th ch c s trao i thng tin ca BS i vi CS c thit lp, BS

trong mt VCZ phi c iu khin bi CS tm ra khung thi gian thch hp. V vy mi

knh RF c n nh trnh hin tng giao thoa cng knh gia cc cell trong cng VCZ.

Nu thit b i vo khu vc m khng c chng ln gia 2 cell lin tc th n ch nhn c

mt khung trong cell m n ang ng. Trong khi , khi n di chuyn vo vng chng ln ca

c 2 cell th n s phi lng nghe c 2 khung trong mt super-frame. V d trong hnh 2.9, V1

ch nhn c frame 1, trong khi V2 li nhn c c frame 1 v 2 trong super-frame .

Ch rng mi frame khng ch h tr mt thit b m c th h tr c nhiu thit b nh

trong cell 3. Nh vy mi CS s c nhiu VCZ, s lng VCZ bng vi s lng super-framesc phc v mt cch ng thi.



25/33


2.4.4 MAC qun l tnh di ng chuyn giao.

a. Cu trc khung.

Tuy mng RoF cha c p dng vo thc t, nhng c nhiu ngh v cu trc

khung cho mng nhm t c nhng yu cu ca mng. Ta s tham kho mt cu trc khung

trong mng RVC s dng k thut RoF nh c m t hnh 2.10

Mi khung trong super-frame thuc s hu ca mt BS v bt u vi mt trng beacon

c pht ra bi CS bao gm m s nhn dng BS (ID) v mt bn tin thng bo vic n nh

khe thi gian cho v tr khe u tin v chiu di khung cho mi MH. Tip theo l trng

reservation minislots m chng c truy cp bi MH xc nh quyn u tin truy cp

vo mng, khung ny khng dng cho truyn d liu. Hn na, n c chia nh thnh cc

minislot dnh cho yu cu chuyn giao lin VCZ, lin CS hay mt kt ni mi cho MH khi gia

nhp vo mng. CS c th thay i cu trc ca cc milislot ny qu trnh chuyn giao t

tr cho php. gii quyt vn tranh chp ti nguyn, cc phng php thng thng

c s dng nh p-persistent. Tip theo l trng broadcast qung b thng tin ca mng

cho cc MH tham gia. Cui cng l trng thng tin c chia thnh 2 phn uplink v

downlink. Trng uplink thng c 1 bit dnh cho c ch chuyn giao nhanh trong cng VCZ

m ta s tho lun phn sau.

Hnh 2.10 Cu trc khung (khng c cc on bo v).



26/33

Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.b. Khi to v gia nhp mng.

Khi mt MH bt u gia nhp vo mng, u tin n phi qut tt c cc knh RF. Sau khi

chn c mt knh RF s dng trong cell , n s gi yu cu v s lng bng thng cn

thit ti CS bng cch s dng mt trong nhng reservation mini-slot. Nu yu cu thnh cng

v h thng c bng thng cung cp cho yu cu , th thit b s c n nh lng

bng thng cn thit trong superframe tip theo.c. H tr tnh di ng chuyn giao.

Trong kin trc mng c pht ha trn th mng RVC s h tr 3 kiu chuyn giao

(hnh 2-11):

Chuyn giao gia 2 BS thuc cng 1 VCZ (intra-VCZ handover)

Chuyn giao gia 2 BS thuc 2 VCZ k nhau (inter-VCZ handover)

Chuyn giao gia 2 BS thuc s qun l ca 2 CS khc nhau (inter-CS handover)

Trong tt c cc trng hp chuyn giao th vng chng ln gia 2 BS phi ln sao cho

thit b c thi gian thc hin chuyn giao. V d MH di chuyn vi vn tc 100km/h th

di chuyn 1m ht 36ms. Do cu trc mi superframes nh (1-5 ms) th th tc chuyn

giao c th thc hin trong vng vi mt. Ta s ln lt tm hiu cc th tc chuyn giao .

Hnh 2.11 Mt v d chuyn giao trong mng RVC.



27/33


Intra-VCZ handover:

Trc ht, do tt c cc BS ca mt VCZ u dng cng mt knh RF, do khi MH tin

n vng chng ln gia 2 BS, n s bt u nhn c 2 beacon, mi becon s cha mt BS-

ID khc nhau c trng cho mi BS trong cng mt superframe. MH s gi tr li CS yu cu

chuyn giao bng cch thit lp c handover indication. Sau , CS s gi tr p ng trn

bng lng bng thng c cp cell tip theo v gii phng bng thng knh c sdng cho cc MH khc. Ta c th nhn thy rng ti nguyn dng thc hin chuyn giao t

BS ny n BS tip theo lun sn c bi v c ch MAC tp trung nn n c th hiu chnh

bng cch thu hp chiu di mt khung ca BS m MH ang ri khi v gia tng khong thi

gian khung ca BS m n chun b chuyn sang cung cp cho MH lng bng thng yu

cu. Do , trong chuyn giao intra-VZV, tr chuyn giao v rt chuyn giao c th gn

bng 0, hn na bng thng c n nh trong sut s di chuyn ca MH. y chnh l nhng

c im chnh ca kin trc d tho ny.

Inter-VCZ handover:

Trong trng hp chuyn giao inter-VCZ, MH khng th lng nghe c khung beacon

VCZ mi c v VCZ lin k s dng nhng knh RF khc trnh hin tng nhiu

giao thoa ng knh. Tng t vi th tc thng thng, MH phi qut tt cc cc knh RF

VCZ tip theo, hay cn c gi l th tc chuyn giao cng. Tuy nhin, trong mng RVC, do

CS bit c hng ca MH nn n c th thng bo cho MH ang di chuyn trong cell cui

cng ca VCZ bit c knh RF c s dng trong VCZ tip theo. Khi MH nhn c

thng tin v knh RF c s dng trong VCZ tip theo, n s bt u qut knh RF mi trong

mt chu k, trong giai on ny n cha c cp bng thng knh tip theo. Nu n nhn

c knh RF mi, n s gi yu cu chuyn giao trong reservation-minislot thc hin qu

trnh chuyn giao inter-VCZ. Nu yu cu ti VCZ mi c chp thun v mng bng

thng cp cho VCZ, MH mi c th lin lc c vi mng, cn ngc li l yu cu gi

n mng b li (rt lin lc). Nh vy, chuyn giao inter-VCZ khng ging vi chuyn giaointra-VCZ bi n khng ch thay i knh tn s m cn phi cp li bng thng cho thit b

nn cn mt c ch qun l bng thng. Cc CS c th t cc u tin chuyn giao cho mi

thit b, nhm hn ch bng thng v cho php kt ni iu khin li trong mng thng tin di

ng cellular.



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Inter-CS handover:

i vi chuyn giao gia 2 CS khc nhau, v d MH di chuyn t vng ph sng BS ny

sang vng ph sng BS khc m 2 BS ny t di s qun l ca 2 CS khc nhau, th vn

quan trng nht l phi bo m thng s QoS cho bt k kt ni no ang di chuyn. Th

tc chuyn giao i vi trng hp ny cng tng t vi th tc chuyn giao inter-VCZ

ni trn, nhng im khc nhau c bn l 2 BS ny c qun l bi 2 CS khc nhau nnchng khng c kin trc tp trung na. Trong trng hp ny 2 CS phi lin lc vi nhau qua

mng ng trc (c th da trn giao thc IP). Tuy nhin gii quyt th tc chuyn giao

i vi inter-CS ny th ngoi giao thc iu khin lp vt l th cn c nhng vn lin

quan n n na nh nh tuyn.

2.4.5 Kt lun chng 2.

Mng truyn thng Road Vehicle trong tng lai s hot ng bng tn mm t

c tc d liu cao hn (t 2-10Mbps). c tnh ca mng RVC l bn knh cell tng i

nh v tnh di ng ca cc user cao, do c ch chuyn giao l mt trong nhng vn quan

trng cn phi gii quyt trong mng ny. Khi kin trc mng hon chnh, n s c ng dng

trn cc tuyn ng cao tc, cc BS c th c lp t ti ci ct n gia hay 2 bn ng

rt thun li. Khi cc phng tin giao thng trn ng c th lin lc vi nhau hay lin lc

vi trung tm iu khin, l c s cho mng iu khin t ng cc phng tin trong mng

ITS .Tuy nhin hin nay mng cng ch mc d tho v cn nhiu vn (cc giao thc lp

cao hn, v mt k thut, v mt kinh t,) cn cn phi gii quyt trong tng lai, nhng

nhng g c vit chng ny cho thy s kh quan ca mng RVC trong tng lai.

2.5 Tng kt.

RoF l mt k thut rt hay kt hp truy nhp v tuyn v truy nhp quang. N kt hp

hai mi trng li vi nhau, l s quang v v tuyn, v l mt trong nhng cch tngi n gin truyn cc tn s v tuyn (bng rng) hay tn hiu baseband trn si quang.

N s dng cc tuyn quang tng t truyn dn v phn phi cc tn hiu v tuyn gia CS

v mt s lng ln cc BS. T khi n bt u c gii thiu ln u tin bi Cooper vo

nm 1990 cho n nay, rt nhiu nghin cu nhm vt qua nhng kh khn ca k thut v

thit k mt BS tht n gin. Hin nay, n bt u i vo giai on nghin cu c th



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Bi Tp Bo Co Nhm : Mn: Chuyn Thng Tin Quang.ng dng cho thng mi v cnh tranh vi nhng cng ngh bng rng khc, v chng ta c

th hi vng trong tng lai k thut RoF c nhiu ng dng hn na vi gi thnh thp hn.

Nhng d th no i na th chng ta cng c th thy c 3 c im quan trng ca mng

ng dng k thut ny so vi cc mng truy nhp v tuyn thng thng l: (1) n trong

sut vi bng thng, k thut iu ch v tuyn v cc giao thc lp v tuyn (2) BS n gin,

nh v (3) kin trc mng tp trung.Trong chng ny, chng ta tm hiu c 2 ng dng ca k thut RoF ln 2 kiu mng

truy nhp v tuyn khc nhau cho nhng ng dng khc nhau. Vi 2 ng dng u, cc cell c

bn knh nh v tnh di ng cc user cao, do vn quan trng trong mng l qun l

tnh i ng. Vi nhng kt qu trn, n ch ra rng cc mng truy nhp v tuyn bng rng

ng dng k thut RoF cn nhng vn kh khn cn gii quyt, n c th cnh tranh vi

nhng mng truy nhp v tuyn ngy nay. Trong khun kh ti, chng em cng khng

cp n vn qun l ti nguyn trong mng, l mt iu rt quan trng i vi mng truy

nhp v tuyn. Tuy nhin, vi nhng g tm hiu c th RoF ang l mt cng ngh ha hn

cho cc dch v v tuyn phng tin bng rng v dung lng ln trong tng lai.



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KT LUN

Trong khun kh ca chuyn , cc ni dung c bn ca k thut RoF cng nh ng dng

ca n vo mng truy nhp v tuyn ln lt c trnh by.

Chng 1 chng ta bt u tm hiu v k thut RoF, l mt k thut mi trong vic kt hp

th gii si quang v th gii v tuyn lai vi nhau. Chng 1 nu ln c cc phng

php c ng dng trong k thut RoF ny, nu ln c cc u im v cch ci tin cng

nh cc nhc im v bin php khc phc. Tuy vn tm hiu cha c nhiu v mc

chung nht cho tng k thut, nhng n lm l r bn cht ca k thut RoF.

chng 2, ta thy c cc ng dng ca k thut RoF vo cc mng truy nhp v

tuyn nh th no. u tin l vo mng WLAN bng tn mm. y l loi hnh mng m

tng li s ph bin thay th cho mng WLAN hin nay ang ph bin l WiFi. Tip l

ng dng ca n vo mng RVC, mt phn trong mng thng minh vi cc ng dng l truy

nhp v tuyn cho cc thit b ang di chuyn v tng lai l cc ng dng trong iu khin t

ng cc phng tin. Vi mt kin trc a ra da trn k thut RoF th ng dng ca n cho

mng trn l mt iu c th thc hin c. Tuy nhin trin khai mt mng nh vy trong

thc t th cn nhiu vn phi c tip tc nghin cu v pht trin hn na tt c cc lp

quang, lp v tuyn v lp mng. chng ny chng em cng ch a ra v tm hiu mt

trong s cc vn quan trng nht cho mi mng, m trn thc t cn nhiu.

Nh vy chuyn t c mt s kt qu nht nh nhng bn cnh cng c nhng

vic cha lm c cng vi nhng thiu st cn b sung.



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HNG PHT TRIN TI

V hng pht trin ca ti cng cho nhiu hng lm ti hon chnh v c ni

dung phong ph hn:

(1) Tm hiu su hn v cc k thut ang c ng dng hay tm hiu cc k thut mi

c ng dng trong k thut RoF c cp trong cc ti liu.

(2) Tm hiu cc cu hnh ca mng c s dng k thut RoF. Mi cu hnh nh vy u c

nhng u nhc im ring v ng dng ph hp cho mt s loi mng.

(3) Hoc tm hiu nhng ng dng ca k thut RoF vo cc mng truy nhp khc hoc c

th tm hiu su hn v cc k thut trong mt mng truy nhp b sung cho cc ng dng

ca mng truy nhp. V khi mt k thut c nhiu ng dng trong thc t th ngha ca k

thut cng ln.

C th ni Chuyn v thng tin quang th hin c vai tr ct li cc k quang trng,

ng thi gp phn a cng ngh tin gn hn vi xu th hi t. Qua bi lm ca nhm, nhm

em tm hiu v nghin cu v cc kin thc c s v thng tin quang ni chung v Kt hp

k thut Radio over Fiber v mng truy nhp khng dy ni ring, c bit vi phn tm hiu

su hn vi k tht v thng tin quang th qu nhiu, qu rng, i hi phi i su hn v kin

thc rng hn.Tuy nhin do thi gian hn ch v tm ngun ti liu cha nhiu nn khng trnh

khi nhng thiu st. Nhm chng em rt mong nhn c kin nh gi ca Thy hon

thin thm kin thc ca nhm. Sau cng , nhm em xin mt ln na c gi li cm n ti

Thy Ths :Trng Xun Trung tn tnh ch bo trong qu trnh thc hin chuyn ny.



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Nhóm 07 - Bai Bao Cao Chuyen De Thong Tin Quang (ĐTVT 11)

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