Do an Tot Nghiep ( Pham Linh)

8/3/2019 Do an Tot Nghiep ( Pham Linh)

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MC LC

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LI M U

Thng tin di ng c coi nh l mt thnh tu tin tin trong lnh vc thng tin

vin thng ca con ngi vi c im cc thit b u cui c th truy cp dch v

ngay khi ang di ng trong phm vi vng ph sng. Thnh cng ca con ngitrong lnh vc thng tin di ng khng ch dng li trong vic m rng vng ph

sng phc v thu bao khp ni trn ton th gii, m cc nh cung dch v, cc

t chc nghin cu pht trin cng ngh di ng ang n lc hng ti mt h

thng thng tin di ng hon ho, cc dch v a dng, cht lng dch v cao. 3G-

H thng thng tin di ng th h 3 l ci ch m th gii ang hng ti.

Ho chung vi xu th pht trin ca th gii. Cc nh cung cp dch v thng tin

di ng Vit nam v ang n lc ht mnh cung cp ti khch hng nhng

dch v vi cht lng tt nht v vi yu cu ngy cng cao ca khch hng th

vic tin ln h thng thng tin di ng th h 3 l iu tt yu. a phn cc cng ty

cung cp dch v thng tin di ng Vit nam p dng cng ngh GSM v cung

cp dch v di ng cho phn ln thu bao di ng Vit nam. V vy, pht trin

ln 3G th l trnh bt buc s l t GSM tin ln WCDMA (a truy nhp phn chia

theo m bng rng) theo hp chun IMT_2000. V em chn ti: IU

KHIN CNG SUT V CHUYN GIAO TRONG H THNG THNG

TIN DI NG WCDMA lm ti nghin cu tt nghip. Ni dung ca tigm:

Chng I: Tng quan v h thng WCDMA

Chng II: iu khin cng sut v chuyn giao trong h thng thng tin

di ng CDMA

Chng III: iu khin cng sut v chuyn giao trong h thng WCDMA

Em xin chn thnh thnh cm n s hng dn nhit tnh ca thy Bi nh

Thnh cng nh s dy bo tn tnh ca cc thy, c trong t mn in t vin

thng khoa in- in t hng hi, trng i hc Hng hi Vit Nam. gip em trong sut bn nm hc tp v trong ba thng lm n va qua.

Mt ln na em xin chn thnh cm n !

Hi Phng , thng 2 nm 2011

Sinh vin: Phm Vn Linh

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CHNG I

TNG QUAN V H THNG WCDMA

1.1 KHI QUT CHUNG V WCDMA- WCDMA (Wide Code Division Multy Access): a truy nhp phn chia theo m

bng rng l cng ngh truy nhp v tuyn chnh ca h thng thng tin di ng

th h th 3- h thng UMTS (Universal Mobile Telecommunications System)

Nn tng cng ngh chnh ca WCDMA l cng ngh a truy nhp phn chia

theo m (CDMA). Trong lch s thng tin di ng tn ti cc phng thc a

truy nhp khc nhau l: FDMA a truy nhp phn chia theo tn s; TDMA a truy

nhp phn chia theo thi gian v CDMA. S khc nhau ca 3 phong thc truy

nhp c ch ra trong hnh 1-1

Hnh 1-1 : Cc phng thc a truy nhp

- Trong h thng a truy nhp theo tn s (FDMA), rng bng tn c cp

pht cho h thng l B Mhz c chia thnh n bng tn con, mi bng tn con c

n nh cho mt knh ring c rng bng tn l B/n Mhz. Cc tn hiu cho mi

ngi s dng khc nhau c truyn trong cc knh khc nhau vi cc tn s iu

ch khc nhau. Mi ngi s dng khi truy nhp mng s c n nh mt knh

tn s. V v mi ngi c cp pht mt knh tn ring trong di bng tn ca h

thng nn cn phi c khong bo v gia tng knh phng nga s khng hon

thin ca cc b lc v cc b dao ng trnh nhiu giao thoa knh ln cn. V

vy, m bo FDMA tt tn s phi c phn chia v quy hoch thng nht

trong ton h thng.

- H thng a truy nhp phn chia theo thi gian (TDMA), cc tn hiu ca ngi

s dng khc nhau c truyn i trong cc khe thi gian khc nhau. My pht ca

mi ngi s dng khng pht lin tc m ch pht vo ng khe thi gian c

n nh cho ngi s dng. S truyn dn ny c gi l cm. S pht i mt cm

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c a vo mt cu trc thi gian c gi l khung, tt c cc my u cui v

tuyn phi pht theo cu trc ny. TDMA vn ng b rt quan trng. ng

b cho php xc nh ng v tr ca cm cn ly ra my thu hay cn pht i

my pht tng ng. Ngoi ra, ng b cn phi xt n c v tr ca cc my di

ng so vi trm gc. So vi FDMA, TDMA cho php tit kim tn s v thit b

thu nh pht nh gn hn. Tuy nhin, nu ch s dng mt cp tn s sng mang

th khng m bo dung lng ca mng. V th TDMA thng c s dng

kt hp vi FDMA tng cao dung lng ca mng. Do , vn quy hoch

mang l mt vn rt quan trng trong cc mng TDMA c bit l c ch ti s

dng tn s.

- CDMA l phng thc a truy nhp m mi knh c cung cp mt tn

s v mt m duy nht. y l phng thc a truy nhp mi, phng thc ny datrn nguyn l tri ph. Trong cc h thng thng tin, thng thng rng bng

tn l vn quan tm chnh v cc h thng ny c thit k s dng cng t

rng bng tn cng tt. Trong cc h thng thng tin tri ph (SS: Spread

Spectrum) rng bng tn ca tn hiu c m rng trc khi pht i. Khi ch c

mt ngi s dng trong bng tn ca h thng SS th khng c hiu qu. Tuy

nhin, mi trng nhiu ngi s dng, cc ngi s dng ny c th dng chung

mt bng tn SS khi vic s dng bng tn c hiu sut cao hn. Mt h thng

thng tin c coi l h thng SS nu: Tn hiu pht chim rng bng tn ln

hn rng bng tn ti thiu cn thit pht tin; Tri ph c thc hin bng

mt m c lp vi s liu. Vi cc cng ngh khc nhau s ngi s dng ln nht

c th chia s ng thi cc knh vt l l c nh. Tuy nhin trong h thng

CDMA, cc tn hiu cho ngi s dng khc nhau c truyn i trong cng mt

bng tn ti cng mt thi im. Trong CDMA ti nguyn v tuyn c phn b

da trn cc m gi ngu nhin. Do vy, nhng ngi s dng ng thi c th

chim dng cng mt bng tn trong cng mt khong thi gian. Mi ngi sdng c gn cho mt hoc nhiu m ring bit. V nhng m c s dng

phn bit cell, knh truyn dn v ngi s dng. Mi tn hiu ngi s dng ng

vai tr nh l nhiu i vi tn hiu ca ngi s dng khc, do dung lng ca

h thng CDMA gn nh l mc nhiu, v khng c con s ln nht c nh, nn

dung lng ca h thng CDMA c gi l dung lng mm. CDMA l cng

ngh thc hin tri tn hiu gc thnh tn hiu bng rng trc khi truyn i. Ngoi

ra th do s dng cng mt bng tn cho tt c mi ngi s dng nn h s ti s

dng tn s ca h thng CDMA l bng mt.

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- WCDMA s dng k thut tri ph chui trc tip DS- CDMA vi tc Chip

l 3.84Mps lm vic bng tn 5Mhz v p dng phng php ghp song cng

phn chia theo tn s FDD. Gii php FDD l s dng hai bng tn 5 MHz vi

hai sng mang phn cch nhau 190 MHz: ng ln c bng tn nm trong

di ph t 1920 MHz n 1980 MHz, ng xung c bng tn nm trong di

ph t 2110 MHz n 2170 Mhz. Mc d 5 MHz l rng bng danh nh,

ta cng c th chn rng bng t 4,4 MHz n 5 MHz vi nc tng l 200

KHz. Vic chn rng bng ng n cho php ta trnh c nhiu giao

thoa nht l khi khi 5 MHz tip theo thuc nh khai thc khc. Bng tn rng

hn v tc tri ph cao lm tng li x l v mt gii php thu a

ng tt hn

- H thng WCDMA s dng ch khng ng b gia cc BS v vykhng cn duy tr mt qu trnh ng b chnh xc gia tt c cc BS. N

c s dng nhm mc ch m bo d dng vic trin khai ph kn sng

bi cc BS cho cc mi trng truyn sng trong nh v ngoi tri, cng nh

d dng trong vic lp thm cc BS tng lu lng phc v tai cc BS b

qu ti

- WCDMA h tr trn vn c dch v chuyn mch knh v chuyn mch gi tc

cao v m bo s hot ng ng thi cc dch v hn hp vi ch gi hotng mc hiu qu cao nht. Hn na, WCDMA c th h tr cc lp tc s

liu khc nhau, da trn th tc iu chnh tc . Chun WCDMA hin thi s

dng phng php iu ch QPSK, mt phng php iu ch tt hn 8-PSK, cung

cp tc s liu nh l 2Mbps vi cht lng truyn tt trong vng ph rng. V

h tr cc tc s liu khc nhau cho nhiu loi dch v ln cn c phng thc

hiu qu kt hp cc dch v vi cc tc khc nhau. V vy, trong WCDMA

i vi ng xung m tri ph OVSF c ng dng cc m trong b m ny

c to ra trc giao vi nhau cho d h s tri ph SF l khc nhau. iu ny chophp cung cp cc dch v vi tc bt khc nhau qua cc knh trc giao vi nhau.

ng ln s dng cc m ngu nhin phn bit gia cc ngi s dng khc

nhau. Cc m ngu nhin ny c mng n nh. MS s nhn c thng bo m

ngu nhin no c cp cho mnh trong bn tin cho php truy nhp trn knh tm

gi ng xung.

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Bng 1-1 ch ra mt s dch v ca h thng thng tin di ng th h 3

Bng 1-1 Cc loi loi dch v chnh ca WCDMA

Kiu knh Dch v h tr

CS 12.2Kb/s Voice

CS 64Kb/s Video Phone

PS 64Kb/s Email, Web

PS 384Kb/s Email, Web ,Video Streaming, Mobil TV

1.2 CU TRC H THNG WCDMA

1.2.1 Cu trc mng WCDMA

Cu trc mng vin thng di ng ton cu (UMTS) vi c s nn tng l h

thng a truy nhp phn chia theo m bng rng (WCDMA) c khi qut bi

hnh 1-2

UuIu

UE UTRAN CN

Hnh 1-2 Cu trc tng quan h thng UMTS

Theo chc nng th cc phn t mng c nhm thnh cc nhm:

+ Mng truy nhp v tuyn RAN (Mng truy nhp v tuyn mt t UMTS l

UTRAN). Mng ny thit lp tt c cc chc nng lin quan n v tuyn. M ha,

iu ch, ghp knh . . .

+ Mng li (CN): Thc hin chc nng chuyn mch v nh tuyn cuc gi v

kt ni d liu n cc mng ngoi.+ Thit b ngi s dng (UE) giao tip vi ngi s dng v giao din v tuyn.

V d: mn hnh, bn phm, micro, loa . . .

Theo cc c t ch ra trong quan im chun ha, c UE v UTRAN u bao gm

cc giao thc hon ton mi, vic thit k chng da trn nhu cu ca cng ngh v

tuyn WCDMA mi. Ngc li, vic nh ngha mng li (CN) c k tha t

GSM. iu ny em li cho h thng c cng ngh truy nhp v tuyn mi mt nn

tng mang tnh ton cu l cng ngh mng li c sn, nh vy s thc y s

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qung b ca n, mang li u th cnh tranh chng hn nh kh nng roaming ton

cu.

V cc thnh phn ca mng WCDMA c ch ra trong hnh 1-3.

UE UTRAN CN

UuIu

USIM

ME

Cu

Nt B

Nt B

Nt B

Nt B

RNC

RNC

MSC/VLR

SGSN

HLR

GMSC

GGSN

PLMN, PSTN,ISDN

Internet

Mng ngoi

IurIub

Hnh 1-3 Cc thnh phn ca mng WCDMA

Thit b ngi s dng(UE) bao gm 2 phn:

Thit b di ng(ME) l u cui v tuyn s dng giao tip v tuyn qua

giao din Uu.

Modul nhn dng thu bao UMTS (USIM- User Identity Module) l mt th

thng minh m nhn vic xc nhn thu bao, thc hin thut ton nhn thc, v

lu gi kho m mt, kho nhn thc v mt s cc thng tin v thu bao cnthit ti u cui.

UTRAN: nhim v chnh ca UTRAN l to v duy tr cc knh mng truy nhp

v tuyn thc hin thng tin gia thit b di ng UE vi mng li CN.

UTRAN bao gm 2 phn t:

Nt B: chuyn i d liu truyn gia giao din Iub v Uu. N cng tham gia

vo qun l ti nguyn v tuyn.

B iu khin mng v tuyn(RNC-Radio Network Controller) s hu v iu

khin ngun ti nguyn v tuyn trong vng ca n (gm cc Nt B ni vi n).. Cc phn t chnh ca mng li

HLR (B ng k thng tr) l mt c s d liu trong h thng thng tr ca

ngi s dng, lu tr cc bn gc cc thng tin hin trng dch v ngi s

dng, hin trng v dch v bao gm: thng tin v dch v c php s dng,

cc vng roaming b cm, thng tin cc dch v b sung nh: trng thi cc cuc

gi i, s cc cuc gi i N c to ra khi ngi s dng mi ng k thu

bao vi h thng, v c lu khi thu bao cn thi hn. Vi mc ch nh

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tuyn cc giao dch ti UE (cc cuc gi v cc dch v nhn tin ngn), HLR

cn lu tr cc thng tin v tr ca UE trong phm vi phc v ca MSC/VLR

hoc SGSN.

MSC/VLR (Trung tm chuyn mch di ng/B ng k tm tr) l mt b

chuyn mch (MSC) v c s d liu (VLR) phc v cho UE v tr tm thi

ca n cho cc dch v chuyn mch knh. Chc nng MSC c s dng

chuyn mch cc giao dch s dng chuyn mch knh, chc nng VLR l lu

tr bn sao v hin trng dch v ngi s dng l khch v thng tin chnh xc

v v tr ca thu bao khch trong ton h thng. Phn ca h thng c truy

nhp thng qua MSC/VLR thng l chuyn mch knh.

GMSC(MSC cng): l mt b chuyn mch ti v tr m mng di ng mt t

UMTS kt ni vi mng ngoi. Tt cc kt ni chuyn mch knh n v i uphi qua GMSC.

SGSN (Node h tr GPRS phc v) c chc nng tng t nh MSC/VLR

nhng thng c s dng cho cc dch v chuyn mch gi.

GGSN(Node cng h tr GPRS) c chc nng gn ging GMSC nhng phc v

cc dch v chuyn mch gi.

Mng ngoic th chia thnh 2 nhm:

Cc mng chuyn mch knh: Cc mng ny cung cp cc kt ni chuyn mchknh, ging nh dch v in thoi ang tn ti V d nh PSTN.

Cc mng chuyn mch gi: Cc mng ny cung cp cc kt ni cho cc dch v

d liu gi, chng hn nh mng Internet.

Cc tiu chun ca h thng vin thng di ng ton cu (UMTS) c cu trc

sao cho khng nh ngha chi tit chc nng bn trong ca cc phn t mng m ch

nh ngha giao din gia cc phn t mng logic

Cc giao din m chnh c nh ngha: Giao din Cu: y l giao din gia th thng minh USIM v ME. Giao din

ny tun theo tiu chun cho cc th thng minh.

Giao din Uu: y l giao din v tuyn WCDMA. Uu l giao din nh UE

truy cp c vi phn c nh ca h thng, v v th c th l phn giao din

m quan trng nht trong UMTS.

Giao din Iu: Giao din ny kt ni UTRAN ti mng li. Tng t nh cc

giao din tng thch trong GSM, l giao din A (i vi chuyn mch knh), v

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Gb (i vi chuyn mch gi), giao din Iu em li cho cc b iu khin UMTS

kh nng xy dng c UTRAN v CN t cc nh sn xut khc nhau.

Giao din Iur: Giao din m Iur h tr chuyn giao mm gia cc RNC t cc

nh sn xut khc nhau, v v th b sung cho giao din m Iu.

Giao din Iub: Iub kt ni mt Nt B v mt RNC. UMTS l mt h thng in

thoi di ng mang tnh thng mi u tin m giao din gia b iu khin v

trm gc c chun ho nh l mt giao din m hon thin. Ging nh cc giao

din m khc, Iub thc y hn na tnh cnh tranh gia cc nh sn xut trong

lnh vc ny.

1.2.2 Cu trc mng truy nhp v tuyn UTRAN

H thng thng tin di ng th h 3- WCDMA c xy dng trn c s mngca h thng GSM vi vic s dng cng ngh mng li ca GSM. Chnh v vy m

im khc bit ln nht v mt cng ngh gia WCDMA vi GSM l mng truy

nhp v tuyn UTRAN vi vic p dng k thut a truy nhp theo m hon ton

mi.

Kin trc UTRAN c m t nh hnh 1-4

UE

UTRANCN

UuIu CS

USIM

ME

Cu

Nut B

Nut B

Nut B

Nut B

RNC

RNC

MSC/

VLR

SGSN

IurIub

Iu PSRNS

RNS

Hnh 1-4: Kin trc UTRAN.

UTRAN bao gm mt hay nhiu phn h mng v tuyn (RNS). Mt RNS l

mt mng con trong UTRAN v bao gm mt b iu khin mng v tuyn (RNC)

v mt hay nhiu Nt B. Cc RNC c th c kt ni vi nhau thng qua mt giao

din Iur. Cc RNC v Nt B c kt ni vi nhau qua giao din Iub.

Cc yu cu chnh thit k kin trc, giao thc v chc nng UTRAN:

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Tnh h tr ca UTRAN v cc chc nng lin quan: Yu cu tc ng ti thit k

ca UTRAN l cc yu cu h tr chuyn giao mm (mt thit b u cui kt ni

ti mng thng qua 2 hay nhiu cell ang hot ng) v cc thut ton qun l

ngun ti nguyn v tuyn c bit ca WCDMA.

Lm tng s tng ng trong vic iu khin d liu chuyn mch gi v chuyn

mch knh, vi mt ngn xp giao thc giao din v tuyn duy nht v vi vic s

dng cng mt giao din cho cc kt ni t UTRAN n min chuyn mch gi

v chuyn mch knh ca mng li.

Lm tng tnh tng ng vi GSM.

S dng phng thc vn chuyn ATM nh l c cu chuyn vn chnh trong

UTRAN

a. B iu khin mng v tuyn (RNC)B iu khin mng v tuyn (RNC) l phn t mng chu trch nhim iu

khin ngun ti nguyn v tuyn ca UTRAN. N giao tip vi mng li (thng l

vi mt MSC v mt SGSN) v cng l phn t cui cng ca giao thc iu khin

ngun ti nguyn v tuyn, xc nh cc thng ip v th tc gia my di ng v

UTRAN, v mt logic, n tng ng vi BSC trong GSM.

RNC phc v (SRNC): RNC cho mi my di ng l mt RNC m xc nh

bin gii c lin kt Iu cho s vn chuyn d liu ngi s dng v bo hiu .

SRNC cng xc nh bin gii ca Bo hiu iu khin ngun ti nguyn v

tuyn, n l giao thc bo hiu gia UE v UTRAN. N thc hin x l cc d

liu chuyn qua giao din v tuyn. Hot ng qun l ngun ti nguyn v tuyn

c bn, nh l nh x cc thng s mang thng tin truy nhp v tuyn thnh cc

thng s knh chuyn vn giao din v tuyn, quyt nh chuyn giao, v iu

khin cng sut vng bn ngoi. Cc hot ng ny c thc thi trong SNRC.

SRNC cng c th l CRNC ca mt s Nt B s dng bi my di ng cho kt

ni vi UTRAN. Mt UE kt ni vi UTRAN th ch c duy nht mt SRNC. B RNC tri (Drif RNC) : DRNC l mt RNC bt k khc vi SRNC iu

khin cc c MS s dng. Khi cn DRNC c th thc hin kt hp v phn

tp v m. DRNC khng thc hin x l s liu trong lp kt ni s liu m ch

nh tuyn s liu gia cc giao din IUb v IUr. Mt UE c th khng c hoc c

mt hay nhiu DRNC.

Ch rng mt RNC mc vt l bao gm ton b cc chc nng CRNC,

SRNC v DRNC.

b. Nt B (Trm gc)

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Chc nng chnh ca Nt B l thc hin x l giao din v tuyn (ghp xen

v m ho knh, thch ng tc , tri ph .v.v.). N cng thc hin mt s hot

ng qun l ti nguyn v tuyn nh l iu khin cng sut vng bn trong. V

mt logic n tng thch vi trm gc trong h thng GSM. Lc u nt B c s

dng l mt thut ng tm thi trong qu trnh chun ho nhng sau n khng b

thay i.

1.3 CC KNH V TUYN

1.3.1 Knh vt l

Trong h thng CDMA th cc knh vt l tng ng vi tn s v m nh knh.

h thng WCDMA th rng bng tn l 5 MHz vi hai sng mang phncch nhau 190 MHz: ng ln c bng tn nm trong di ph t 1920 MHz

n 1980 MHz, ng xung c bng tn nm trong di ph t 2110 MHz

n 2170 Mhz. Mc d 5 MHz l rng bng danh nh, ta cng c th chn

rng bng t 4,4 MHz n 5 MHz vi nc tng l 200 KHz. Khung v

tuyn l mt khi x l bao gm 15 khe thi gian c chiu di 38400 chip,

mt khe thi gian c chiu di 10ms gm 2560 chip. V th s bit trn mt

khe c th khc nhau v trong mt vi trng hp c th bin i theo thi

gian. Cu trc khung v tuyn c biu din trn hnh 1- 5

Hnh !-5: Cu trc khung v tuyn

Ngoi ra th mi knh cn c n nh bi mt m nh knh. M nh

knh l cc m trc giao c h s tri ph bin i (OVSF) m bo s trc

giao gia cc knh vt l. Cc m OVSF c nh ngha theo cy m trn

hnh 1- 6. Mi mc trn cy m xc nh mt m nh knh vi chiu di

Khe 0

Khe 14Khe 1 Khe i

Data

Tslot

=2560 chip, 10.2k bit (k=0,1..,6)

Tf

= 10ms

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bng h s tri ph SF. Tt c cc m trong cy khng th dng ng thi

trong cng mt cell. Mt m ch c s dng trong mt cell khi trong cell

khng s dng mt m no khc nm trn ng t mt m c th ti gc

cy hay trong cy con di m y. iu y c ngha rng s m nh knh

kh dng l khng c nh m ph thuc vo tc v h s tri ph ca mi

knh vt l. Cc m nh knh c k hiu l Cch,SF,ktrong ch l knh, SFl h s tri ph v 0 k SF-1 l s m. H s tri ph l t s gia tc

chip vi tc k hiu a ln tri ph v n cng bng chu k hay di

ca chui tri ph. Mi cy m c xc nh bi mt m ngu nhin ha

nhn dng BS hoc UE.

Hnh 1-6: Cu trc cy m ca m nh knh

Phng php xc nh m nh knh c xy dng trn c s ma trn

Hadamard nh sau:

Cch,4,0 = (1,1,1,1)

Cch,4,1

= (1,1,-1,-1)

Cch,4,2

= (1,-1,1,-1)

Cch,4,3

= (1,-1,-1,1)

Cch,2,0

= (1,1)

Cch,2,1

= (1,-1)

Cch,1,0

= (1)

SF= 1 SF= 2 SF= 4

Cch,2

n

,0C

ch,2

n

,0

Cch,2

n

,0- C

ch,2

n

,0

n n

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Gi tr ngoi cng bn tri trong tng t m nh knh l chui chip c

truyn u tin. Khi kt ni s dng h s tri ph kh bin vic s dng ng n

cy m cng cho php gii tri ph theo h s tri ph nh nht. Do vy, ch cn s

dng m nh knh chn t nhnh c ch th bi m c h s tri ph nh nht.

m bo tnh trc giao gia cc m trong mt cy m cn tha mn quy nh

sau cho vic chn m nh knh cng mt cy m (cng 1 BS hoc cung 1 UE):

ch c th s dng mt m khi v ch khi khng c m no khc c s dng

cng nm trn ng dn t m ny n gc cy hoc cy con pha di m

ny. Cc m trc giao ng xung trong mt trm gc c qun l bi b iu

khin mng v tuyn RNC trong mng.

1.3.2 Knh logic

Cc knh logic l mt nhm cc bit mang mt thng tin c th no : c th l

thng tin v lu lng hay thng tin bo hiu , iu khin. Cc knh ny c phn

chia theo ng xung (t BS n MS) v cc knh ng ln ( t MS n BS).

Cc knh logic WCDMA gm: knh hoa tiu PiCH (ng xung), knh tm gi

PCH (ng xung), knh ng b SCH (ng xung), knh qung b BCH

(ng xung), knh truy nhp ngu nhin RACH (ng ln), cc knh lu lng

TCH c s dng mang thng tin ca ngi s dng (thoi hoc s liu) cng

vi bo hiu gia BS v MS, y l cc knh hai chiu

Cch,1,0

= 1

Cch,2,0

Cch,2,0

Cch,1,0

Cch,1,0

Cch,1,0

- Cch,1,0

1 1

1 -1

ch,2 ,1 - ch,2 ,1..

Cch,2

n

,2

n -1 Cch,2

n

,2

n -1

Cch,2

n

,2

n -1 - Cch,2

n

,2

n -1

Cch,2

n

,2

n -1

Cch,2

n

,0

Cch,2

n

,1

Cch,2

n

,1

.

Cch,2

n

,2

n -1

Cch,2

n

,2

n -1

Cch,2

n

,0

Cch,2

n

,1

Cch,2

n

,1 .

Cch,2

n

,2

n -1

Cch,2

n

,2

n -1

Cch,2

(n+1)

,0

Cch,2

(n+1)

,1

Cch,2

(n+1)

,2

Cch,2

(n+1)

,3 .

.C

ch,2

(n+1)

,2

(n+1) -2

Cch,2

(n+1)

,2

(n+1) -1

= =

=

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a. Knh hoa tiu (PiCH)

Knh hoa tiu PiCH lun c trm gc pht mi knh WCDMA ng

xung. Knh hoa tiu c s dng cung cp tham s chun cho tt c cc tram

di ng, n cung cp tham chun pha cho gii iu ch nht qun. PiCH khng

mang thng tin v l mt tn hiu tri ph khng c iu ch c s dng

ng b cc trm di ng nm trong vng ph ca trm gc, v th cu trc ca

knh ny l mt chui ton khng c tri ph bi hm Walsh 0. Tn hiu hoa tiu

c duy tr mc cao hn knh lu lng vi cng sut tn hiu khng i. Tn

hiu hoa tiu c s dng so snh cng tn hiu gia cc BS khc nhau khi

thc hin chuyn giao v l c s MS iu khin cng sut pht khi truy nhp

mng.

c. Knh ng b (SCH)

Knh ng b c s dng m bo ng b khung, thi gian v cu hnh

h thng cho trm di ng. knh ny ch c mt bn tin c pht i l bn tin

knh ng b. Cc thng s ca bn tin ng b l:

- Nhn dng h thng (SID: System Identification): s nhn dng cho h

thng

- Nhn dng mng (NID: Network Identificatin): s nhn dng mng

- Trng thi m di: m di ti mt thi im xc nh thi gian h thng

- Thi gian h thng

- Tc s liu knh tm gi s knh tm gi, th t khe ca knh tm gi

Bn thn cc bn tin knh ng b c th chim nhiu khung

b. Knh tm gi (PCH)

Knh tm gi mang thng tin t trm gc ti trm di ng. Tn ti bn kiubn tin chnh: b sung, tm gi, lnh v n nh knh. Ni dung ca cc bn tin ny

nh sau:

- Cu hnh ca h thng c truyn cc bn tin b sung: bn

tin thng s h thng, bn tin thng s truy nhp, bn tin danh sch

trm ln cn v bn tin danh sch knh CDMA

- Cc bn tin tm gi cha cc tm gi n mt hay nhiu trm di

ng. Cc tm gi ny thng c pht i khi trm gc nhn c

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mt cuc gi cho mt trm di ng v chng thng c pht t

nhiu trm gc khc nhau.

- Cc bn tin n nh knh cho php trm gc n nh mt knh lu

lng cho mt trm di ng, hay thay i n nh knh tm gi cho

trm di ng ny.

Knh tm gi c mt ch c bit c gi l ch c nh khe. ch

ny cc bn tin cho mt trm di ng ch c pht i cc khong thi gian

nh trc. Kh nng ny cho php trm di ng c th gim cng sut cc khe

thi gian khng dnh cho n, nh vy c th tit kim ng k nng lng ngun

c quy ca my cm tay. Mi MS s c mng n nh mt khe ca knh tm gi.

MS s ly thng tin khe tm gi trn cc bn tin ca knh ng b.

d. Knh qung b (BCH)

L knh ng xung c pht trn ton b cell. BCH c dng pht cc

thng tin mang tnh cht qung b thng tin c truyn di dng kiu truyn n

e. Knh truy nhp ngu nhin (RACH)

Knh truy nhp ch c ng ln. N c trm di ng s dng khi uthng tin vi trm gc v tr li cc bn tin ca knh tm gi. Mi knh truy nhp

u i cp vi mt knh tm gi. Cc knh truy nhp c phn bit vi nhau bi

mt m PN di

f. Knh lu lng (TCH)

Knh lu lng c c ng xung v ln. Knh lu lng truyn:

- Thng tin ca ngi s dng: thoi, s liu

- Thng tin bo hiu

- Thng tin mo u

- Thng tin iu khin

C bn loi bn tin c pht trn TCH: cc bn tin iu khin cuc gi, cc

bn tin iu khin chuyn giao, cc bn tin iu khin cng sut ng xung, cc

bn tin bo mt v nhn thc, cc bn tin cung cp cc thng tin c bit t/ti trm

di ng

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1.4 QUY HOCH PH TN CA WCDMA

Cc bng tn s dng cho WCDMA FDD trn ton cu c cho trn hnh 1-7

WCDMA s dng phn b tn s quy nh cho IMT-2000 (International Mobile

Telecommunications-2000) nh sau. chu u v hu ht cc nc chu bng

tn IMT-2000 l 2 60 MHz (1920-1980 MHz cng vi 2110-2170 MHz) c th s

dng cho WCDMA/ FDD. Bng tn s dng cho TDD chu u thay i, bng tn

c cp theo giy php c th l 25 MHz cho s dng TDD 1900-1920 (TDD1)

v 2020-2025 MHz (TDD2). Bng tn cho cc ng dng TDD khng cn xin php

(SPA= Self Provided Application: ng dng t cp) c th l 2010-2020 MHz. Cc

h thng FDD s dng cc bng tn khc nhau cho ng ln v ng xung vi

phn cch l khong cch song cng, cn cc h thng TDD s dng cng tn s

cho c ng ln v ng xung.UMTS quy nh khai thc song cng phn chia theo tn s l ch tiu

chun cho thng tin thoi v s liu. Hot ng ng thi v lin tc ca cc mch

in pht v thu l cc thay i ng k nht so vi hat ng ca GSM.

Hnh 1-7. Phn b tn s cho WCDMA/FDD.

a) Cc bng c th dng cho WCDMA FDD ton cu; b) Bng tn IMT-2000.

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Bng tn cho hat ng FDD cho cc bng I, II v III c cho trn hnh 1-7.

Bng I (B1) l n nh bng chnh Chu u. Quy nh dnh hai cp pht 60MHz

vi khong cch song cng chun 190MHz, tuy nhin quy nh cng cho php song

cng kh bin, trong khong cch pht thu nm trong khong 130 n 250MHz.

H thng song cng kh bin t ra cc yu cu b sung i vi thit k my pht

thu v cc b t hp tn s my pht v my thu phi hot ng c lp vi nhau.

Bng II (B2) ti s dng bng hin c ca h thng thng tin di ng c nhn v d

nh s dng M m bo ng tn ti UMTS v GSM. Khong cch song

cng ch bng 80MHz i vi bng II v th t ra cc yu cu kh khn hn i

vi phn cng ca my thu pht.

Ti Vit Nam bng tn 3G c cp pht tn s theo tm khe tn s nh cho trong

bng 1-2, trong hai hoc nhiu nh khai thc c th cng tham gia xin cp phtchung mt khe.

Bng 1-2. Cp pht tn s 3G ti Vit Nam

Khe tn s FDD TDD

BSTx* BSRx** BSTx/BSRx

A 2110-2125 MHz 1920-1935 MHz 1915-1920 MHz

B 2125-2140 MHz 1935-1950 MHz 1910-1915 MHz

C 2140-2155 MHz 1950-1965 MHz 1905-1910 MHzD 2155-2170 MHz 1965-1980 MHz 1900-1905 MHz

* BSTx: my pht trm gc

** BSRx: my thu trm gc

L do cp pht cc knh 5MHz khc nhau ti cc nc khc nhau l ch cc

nh khai thc phi quy hoch m v phi trnh vic s dng cc m gy ra nhiu

knh ln cn trong cng mt nc hoc cc nh khai thc khc trong nc lin k.

V th cn phi nghin cu quan h gia cc t hp m tri ph v hot ng cacc knh ln cn. Hin nay ti Vit Nam bng tn I dnh cho WCDMA c

chia l bn khe v c cp pht cho bn nh khai thc: Viettel, VMS, GPC,

EVN+HT

Chng II

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IU KHIN CNG SUT V CHUYN GIAO TRONG H

THNG THNG TIN DI NG A TRUY NHP PHN

CHIA THEO M

Trong h thng thng tin di ng m bo tnh di ng ca thu bao th cc

trm pht phi c t khp ni. Mi trm s ph sng mt vng nht nh v

chu trch nhim vi cc thu bao nm trong vng ph sng ca mnh v h thng

phi m bo tnh lin tc ca tn hiu lin lc khi thu bao di chuyn gia cc trm

pht. Mt khc, do trong h thng CDMA cc thu bao cng s dng chung mt

bng tn ln xy ra hin tng tn hiu mnh ln t tn hiu yu (hiu ng gn xa),

nhiu ng knh. V vy, m bo cht lng QoS yu cu ca dch v h thngphi p dng cc k thut iu khin cng sut v chuyn giao nhm hn ch nhiu

ng knh, gii quyt vn gn xa v lm tng dung lng h thng, tha mn

yu cu roanming.

2.1 IU KHIN CNG SUT

2.1.1 C s ca iu khin cng sut

cc h thng thng tin di ng t ong CDMA, cc my di ng u pht chung

mt tn s cng thi gian nn chng gy nhiu ng knh i vi nhau. Chtlng truyn dn ca ng truyn v tuyn i vi tng ngi s dng trong mi

trng a ngi s dng ph thuc vo t s Eb/N0, trong Ebl nng lng bitcn N0 l mt tp m trng Gaus cng bao gm t tp m v tp m quy i t

my pht ca cc ngi s dng khc. m bo t s Eb/N0 khng i v ln

hn ngng yu cu cn iu khin cng sut ca cc my pht ca cc ngi s

dng theo khong cch ca n vi trm gc. Nu nh cc h thng FDMA v

TDMA vic iu chnh cng sut ny khng bt buc th h thng CDMA iuchnh cng sut l bt buc v iu chnh ny phi nhanh nu khng dung lng

ca h thng s gim. Chng hn nu cng sut thu c ca mt ngi s dng

no trm gc ln hn mi ln cng sut pht ca cc ngi s dng khc, th

nhiu giao thoa ng knh do ngi s dng ny gy ra cng ln gp mi ln

nhiu ca cc ngi s dng khc. Nh vy dung lng ca h thng s gim i

mt lng bng chn. Cng sut thu c trm gc ph thuc vo khong cch

ca cc my di ng so vi trm gc v c th thay i n 80 dB. Hin tng cng

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sut thu thay i theo khong cch gia MS v BS c gi l hin tng gn- xa

hin tng ny nh hng ln ti h thng, c th c minh ha nh sau:

Hnh 2-1 : M t hin tng gn- xa

Gi s c hai trm di ng MS1v MS2cch u trm gc BS mt khong l d v

pht i cng mt cng sut l Pt1= Pt2pht cng thi gian v tn s nn MS1v

MS2s gy nhiu ln nhau. Do c hai trm di ng c cng cng sut pht v cchu trm gc nn t s tn hiu trn can nhiu s bng 1:

C/I=Pr1/Pr2= 1

Trong : Pr1, Pr2 l cc tn hiu m BS thu c t MS1v MS2. By gi nu

MS1 ng yn cn MS2 tin gn li trm gc sao cho khong cch t MS2 ti trm

gc l d/2. Gi s suy hao ng truyn t l vi m 4 khong cch th cng sutthu trm gc i vi MS1 s suy hao vi t l d

4 cn i vi MS2s suy hao theo

t l (d/2)4= d4*1/16. Do cng sut thu c trm gc ca MS2 s ln hn cng

sut thu c ca MS1 l 16 ln v t s tn hiu trn can nhiu trong trng hp

ny s l:

C/I=Pr1/Pr2= 1/16

iu c ngha l t s tn hiu trn can nhiu gim 16 ln so vi trng hp

hai trm di ng cng khong cch. gii quyt vn ny ngi ta cn iukhin cng sut pht ca cc trm di ng sao cho cc trm di ng gn trm gc

s pht cng sut nh hn so vi cc trm di ng xa trm gc. Trong trng hp

ny cng sut pht ca trm MS2 s phi gim 16 ln C/I=1.

Dung lng ca mt h thng di ng CDMA t gi tri cc i nu cng sut

pht ca cc my di ng c iu khin sao cho trm gc cng sut thu c l

nh nhau i vi tt c cc ngi s dng. Ngoi vic gim hin tng gn xa,

iu khin cng sut cn c s dng gim hin tng che ti v duy tr cng

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sut pht trn mt ngi s dng, cn thit m bo t s li bit mc cho trc,

mc ti thiu. Nh vy, iu khin cng sut cn cho mt ci li khc l ko di

tui th ca c quy ca MS.

- Ngoi ra th vic iu khin cng sut cn lm tng kh nng gii tri ph tn

hiu thu, lm cho vic thu, tch tch tn hiu c d dng hn: Nu c hai trm di

ng MS1 v MS2 cng thu, pht trn mt knh CDMA c ph tn hiu tng ng

l D1(f) v D2(f). Ph D1(f) v D2(f) c th nm gn hoc xa nhau trn di tn.

Trc khi truyn i cc ph ny s c tri rng ra nh m tri ph c 1(t) v c2(t)

tng ng. Lc ny ph ca tn hiu c dng gn ging ph ca tp m.

Gi s tn hiu ca trm di ng MS1 l tn hiu cn thu, th tn hiu ca MS2 coi

nh l nhiu. Ti pha thu tn hiu cn thu s c a vo gii tri ph vi m gii

tri ph c1(t) l bn sao ng b ca m tri ph ti pha pht. Nh vy ph tn hiu

D1(f) s c nn li ging nh ph ban u. Cc nhiu di hp sinh ra trong qu

trnh truyn tin s c tri ph ra vi m c1(t) v nh vy ta s thu c tn hiu

cn thu ca MS1. Nhng nu ti pha thu tn hiu tri ph tn hiu ca MS2 thu c

vn cn cao hn (do cng sut pht ln) ph tn hiu ca MS1 sau khi nn (ni

cch khc ph tn hiu D1(f) b chm trong nn nhiu) th my thu cng s khng

thu c tn hiu ca MS1 lm mt thng tin. Nh vy thu c tn hiu ca MS1th phi iu chnh cng sut pht ca nn tp m thu c ti my thu ca BTS

l ng u nhau

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Hnh 2-2: M t s tc ng ca cng sut n vic gii tri ph

Nh vy cng sut ca cc my di ng c iu chnh sao cho sau khi gii tri

ph th ph ca tn hiu cn thu s ln hn nn nhiu my thu c th tch v gii

iu ch.

2.1.2 Phn loi iu khin cng sut

iu khin cng sut nhanh v nghim ngt l nt quan trng nht cc h

thng thng tin di ng CDMA, nht l ng ln. Thiu iu khin cng sut,

mt MS pht cng sut ln hn s chn mt b phn ln dn n hin tng gn-

xa CDMA lm gim dung lng h thng. iu khin cng sut ca mt h

thng th ngi ta cn vo cc tham s sau:

- Trn c s o cng tn hiu

- Trn c s t s tn hiu trn tp m SIR

- Trn c s t l li bt BER

Da vo cc tham s trn chng ta c cc phng php iu khin cng sut sau:

a/ iu khin cng sut cho ng xung v ng ln

iu khin cng sut cho ng ln (t MS n BS) h thng DS-CDMA l

mt yu cu rt quan trng v hiu ng gn-xa. Trong trng hp ny, c mt di

ng iu khin cng sut chng 80 dB. Trn ng xung, khng c hiu ng

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gn-xa do m hnh mt-ti nhiu. iu khincng sut c nhim v b nhiu bn

trong cell gy ra bi cc trm di ng, c bit l nhiu gn bin gii ca ca cc

cell ny (c ch ra trong hnh 2-3). Hn th na, iu khin cng sut trn ng

xung c nhim v lm gim thiu nhiu bng cch gi QoS ti mc gi tr mc

tiu.

Hnh 2-3 B nhiu bn trong cell (iu khin cng sut ng xung)

b/ iu khin cng sut phn tn v tp trung

Mt b iu khin tp trung c tt c cc thng tin v cc kt ni c thit lp

v li knh, v iu khin tt c cc mc cng sut trong mng hay mt phn

ca mng. iu khin cng sut tp trung theo yu cu tn hiu iu khin phm vi

rng trong mng v khng th ng dng trong thc t. Chng c th s dng a

ra gii hn v hiu sut ca thut ton phn tn.

B iu khin phn tn ch iu khin cng sut ca mt trm pht n v thut

ton ch ph thuc vo ni b, nh SIR hay li knh ca ngi s dng c bit.

Nhng thut ton ny thc hin tt trong trng hp l tng, nhng trong cc h

thng thc t c mt s hiu ng khng thch hp nh :

- Tn hiu o v iu khin lm mt thi gian dn n thi gian tr trong h

thng- Cng sut pht hp l ca my pht b hn ch bi gii hn vt l v s

lng t ha. Nhng hn ch bn ngoi khc nh cng sut pht cc i trn mt

knh c bit tc ng n cng sut ra.

- Cht lng l mt s o c ch quan v cn phi tn dng s o c khch

quan hp l.

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c/ iu khin cng sut vng kn, iu khin cng sut vng h

Tn ti ba phng php iu khin cng sut sau y:

iu khin cng sut vng h (ch c UE thc hin qu trnh iu

khin) iu khin cng sut nhanh vng kn (c UE v BS cng tham gia qu

trnh iu khin cng sut) gm iu khin cng sut vng trong v

iu khin cng sut vng ngoi.

H thng WCDMA cung cp chc nng iu khin cng sut hai chiu, chiu

v (t BS n my di ng), chiu ln (t my di ng n BS) kt hp vi qu

trnh iu khin cng sut vng h v vng kn. Nhm nng cao dung lng h

thng, m bo cc dch v cht lng cao

2.2 CHUYN GIAO

Do tnh cht di ng ca thu bao di ng nn mng di ng phi t chc theo

mt cu trc a l nht nh tin cho vic kt ni mng v thng tin lin lc ca

UE cng nh cho vic theo di v qun l thu bao di ng ca nh mng. Mt

phng php t chc hp l m ngy nay hu nh tt c cc mng in thoi di

ng u p dng l phng php t chc mng c cu trc nh mng t ong.

Trong thng tin di ng CDMA ni ring, thng tin di ng ni chung th cc thu

bao di ng MS lun di chuyn t vng ny sang vng khc, ni cch khc l MS

lun di chuyn qua lai gia cc t bo ca mng. Vic di chuyn ny c th dn

ti vic ng k v tr mi vo VLR, s canh nghe trn knh tm gi, ng truyn

thng tin trn cc knh lu lng cng phi thay i ph hp vi s thay i ca

tng trm gc BS khc nhau. Qu trnh thay i cho ph hp gi l qu trnh

chuyn giao. Chuyn giao l phng tin cn thit thu bao c th di ng trong

mng. Khi thu bao di chuyn t vng ph sng ca cell ny sang vng ph sng

ca mt cell khc th kt ni vi cell mi phi c thit lp v kt ni vi cell cphi b hy b.

2.2.1 Mc ch ca chuyn giao ( Handoff)

C nhiu l do cn phi thc hin vic chuyn giao. L do c bn ca chuyn

giao l kt ni v tuyn khng tha mn mt b tiu chun nht nh v do hoc

UE hoc UTRAN s thc hin cc cng vic ci thin kt ni . Cc iu kin

chuyn giao thng gp l: iu kin cht lng tn hiu, tnh cht di chuyn ca

thu bao, s phn b lu lng, bng tn

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iu kin cht lng tn hiu l iu kin khi cht lng hay cng tn hiu

v tuyn b suy gim di mt ngng nht nh c nh ngha bi RNC, s suy

gim tn hiu s c nhn bit bng cch o mc tn hiu. Vic o tn hiu c

thc hin c UE v RNC. Chuyn giao ph thuc vo cht lng tn hiu c

thc hin cho c hng ln v hng xung cu ng truyn dn v tuyn.

Chuyn giao do nguyn nhn lu lng xy ra khi dung lng lu lng ca

cell t ti mt gii hn ti a cho php hoc vt qu ngng gii hn . Khi

cc thu bao ngoi ra ca cell (c mt ti cao) s c chuyn giao sang cell

bn cnh (c mt ti thp). Bng cch thc hin chuyn giao nh vy, ti h

thng s c phn b u v nh cu v dung lng v vng ph sng c iu

chnh mt cch c hiu qu p ng nhu cu lu lng trong mng.

S lng chuyn giao ph thuc vo tc di chuyn ca thu bao. Khi UE dichuyn theo mt hng nht nh khng thay i, tc di chuyn ca UE cng

cao th cng c nhiu chuyn giao thc hin trong RAN. trnh nhng chuyn

giao khng cn thit, thu bao chuyn ng vi tc cao c th c thc hin

chuyn giao t cc cell vi m (micro-cell) n cc cell v m (macro-cell). Trong

trng hp ngc li thu bao di chuyn vi tc chm, thu bao ny c th c

chuyn giao t cell v m sang cell vi m nhm ci thin cht lng tn hiu.

Quyt nh thc hin chuyn giao thng thng c thc hin bi RNC ang

phc v thu bao , loi tr trng hp chuyn giao v l do lu lng. Chuyngiao do nguyn nhn lu lng c thc hin bi trung tm chuyn mch di ng

(MSC)

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o lng:- o cc tham s

- Bo co cc tham so c

Quyt nh:-Cc tham s thutton-Cc c tnh chuyngiao

Thc hin;- Tn hiu chuyn giao- Phn b ti nguynv tuyn

2.2.2 Trnh t chuyn giao

Trnh t chuyn giao gm c ba pha nh hnh v, bao gm : pha o lng, pha

quyt nh v pha thc hin.

Hnh 2-4:Tin trnh thc hin chuyn giao

a/ o lngo lng l mt nhim v quan trng trong qu trnh chuyn giao v hai l do c

bn sau :

- Mc tn hiu trn ng truyn dn v tuyn thay i rt ln ty thuc

vo pha inh v tn hao ng truyn. Nhng thay i ny ph thuc vo

mi trng trong cell v tc di chuyn ca thu bao.

- S lng cc bo co o lng qu nhiu s lm nh hng n ti h

thng

thc hin chuyn giao, trong sut qu trnh kt ni, UE lin tc o cng

tn hiu ca cc cell ln cn v thng bo kt qu ti mng, ti b iu khin truy

nhp v tuyn RNC. D liu o lng ca UE c th chia thnh cc nhm sau :

- D liu o cng tn s l d liu o cng tn hiu cng tn s ca cc

knh vt l ng xung.

- D liu o cc tn s khc nhau l d liu o cng tn hiu c tn s

khc nhau ca cc knh vt l ng xung.

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- D liu o gia cc h thng bao gm d liu o cng ca cc knh

vt l ng xung ca cc h thng truy nhp khc, v d nh h thng

GSM.

- D liu o mt lu lng gm d liu o mt ng ln.

- D liu o cht lng l d liu o cc tham s cht lng, chng hn nh

FER ca ng xung.

- D liu o ni b gm cc s liu o cng sut truyn dn UE v mc tn

hiu thu ti UE

Tn hiu o c kch bi cc iu kin sau :

- Thay i ca cell tt nht (cell c mc tn hiu cao nht).

- Nhng thay i mc tn hiu ca knh hoa tiu

- Nhng thay i v t s tn hiu trn tp m SRN- Thng bo c tnh cht chu k.

- Thi im kch.

b/ Quyt nh chuyn giao

Pha quyt nh chuyn giao bao gm nh gi tng th v QoS ca kt ni so

snh n vi cc thuc tnh QoS yu cu v c lng t cc cell ln cn. Ty theo

kt qu so snh m ta c th quyt nh thc hin hay khng thc hin chuyn giao.

SRNC kim tra cc gi tr ca cc bo co o c kch hot mt b cc iu kinchuyn giao. Nu cc iu kin ny c kch hot, RNC phc v s cho php thc

hin chuyn giao.

Cn c vo quyt nh chuyn giao, c th phn chia chuyn giao ra thnh hai

loi nh sau :

- Chuyn giao quyt nh bi mng NEHO (Network Evaluated Handover).

- Chuyn giao quyt nh bi thu bao di ng MEHO (Mobile Evaluated

Handover)

Trong trng hp chuyn giao thc hin bi mng (NEHO), SRNC thc hin

quyt nh chuyn giao. Trong trng hp MEHO, UE thc hin quyt nh chuyn

giao. Trong trng hp kt hp c hai loi chuyn giao NEHO v MEHO, quyt

nh chuyn giao c thc hin bi s phi hp gia SRNC vi UE.

Ngay c trong trng hp chuyn giao MEHO, quyt nh cui cng v vic

thc hin chuyn giao l do SRNC. RNC c trch nhim qun l ti nguyn v

tuyn ca ton b h thng v cc thng tin cn thit khc phc v cho vic thc

hin chuyn giao.

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Quyt nh chuyn giao da trn cc thng tin o c ca UE v BS cng nh

cc iu kin thc hin thut ton chuyn giao. Cc thut ton chuyn giao

khng c tiu chun ha, chng c lp vi qu trnh xy dng h thng. Do

cc thut ton chuyn giao tin tin c s dng t do da trn cc tham s sn c

kt hp vi kh nng o c cc phn t ca mng, s phn b lu lng, quy

hoch mng, cu trc h tng mng v chin lc lu lng ca ton b h thng

c s dng bi cc nh cung cp dch v.

c/ Thc hin chuyn giao

Qu trnh chuyn giao c th xy ra trng thi ri hay trng thi knh lu

lng.

- Chuyn giao trng thi riChuyn giao ri hay thay i knh tm gi xy ra khi MS chuyn t vng ph

ca BS ny sang vng ph ca BS khc trng thi ri. MS xc nh rng xy ra

chuyn giao khi n pht hin ra hoa tiu mi ln hn hoa tiu hin thi.

Cc knh hoa tiu c nhn dng bi dch thi ca chui PN ngn. Cc knh

ny c nhm vo cc tp m t trng thi ca chng lin quan n cc th tc tm

kim hoa tiu. trng thi ri, ba tp hoa tiu c duy tr: tch cc, k cn, v cn

li. i vi mi tp hoa tiu, ca s tm kim c nh ngha. Ca s ny cho

php MS tm kim ng truyn trc tip cng nh cc thnh phn ca cc ngkhc ca tn hiu hoa tiu. Nu MS xc nh rng hoa tiu tp k cn hoc tp cn

li ln hn hoa tiu ca tp tch cc, chuyn giao ri c thc hin

- Chuyn giao trng thi knh lu lng

Chuyn giao trng thi knh lu lng l qu trnh chuyn giao xy ra khi MS

c n nh knh lu lng

C cc trng hp chuyn giao l: chuyn giao bn trong v chuyn giao gia cc .

Chuyn giao gia cc gm :

- Chuyn giao gia cc thuc hai BTS khc nhau nhng cng mt BSC

- Chuyn giao gia cc thuc hai BTS khc nhau ca hai BSC cng MSC

- Chuyn giao gia cc thuc hai BTS thuc hai MSC khc nhau.

Cn c vo cc trng hp chuyn giao khc nhau trong h thng CDMA tn ti

cc dng chuyn giao sau :

1) Chuyn giao cng ( chuyn giao cng lin tn v lin h thng)

2) Chuyn giao mm

3) Chuyn giao mm hn

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Chuyn giao cng

- Chuyn giao cng da trn nguyn tc: Ct trc khi ni. Trong chuyn giao

ny kt ni vi knh c b ct trc khi kt ni vi knh mi c thc hin. V vy

m trong qu trnh chuyn giao cng tn hiu lin lc s b gian on tuy nhin

khong gin on ny cc MS khng th nhn bit c. Trong CDMA th chuyn

giao cng ch yu dng chuyn giao gia cc sng mang CDMA khc nhau hay

chuyn giao vi cc h thng di ng khc

Chuyn giao mm v mm hn

- Chuyn giao mm v mm hn da trn nguyn tc kt ni: Ni trc khi ct.

Chuyn giao mm l chuyn giao trong trm di ng bt u thng tin vi mt

trm gc mi m vn cha ct thng tin vi trm gc c. Chuyn giao mm ch c

th c thc hin khi c trm gc c ln trm gc mi u lm vic cng tn s - Chuyn giao mm hn l chuyn giao mm c thc hin gia cc on cacng mt .

Cng nh iu khin cng sut chuyn giao mm v mm hn cn phi c cc

h thng thng tin di ng CDMA v l do sau: trnh hin tng gn- xa xy ra

khi MS tin su vo vng ph sng ca ln cn m khng c BTS ca ny

iu khin cng sut dn n n s gy nhiu rt ln cho cc MS khc ny.

Chuyn giao cng thng xuyn v nhanh c th trnh c iu ny, nhng

chuyn giao ny ch c th thc hin c vi mt thi gian tr nht nh, trongkhong thi gian ny c th xy ra hin tng gn- xa. V th cng vi iu khin

cng sut, cc chuyn giao mm v mm hn l cc cng c k thut quan trng

gim nhiu CDMA

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CHNG III

IU KHIN CNG SUT V CHUYN GIAO

TRONG H THNG WCDMA

3.1 IU KHIN CNG SUT

3.1.1. Cc dng iu khin cng sut

iu khin cng sut nhanh v nghim ngt l nt quan trng nht cc h

thng thng tin di ng WCDMA, nht l ng ln. Do cng ngh WCDMA

s dng k thut tri ph nn tt c cc thu bao c th thu, pht chung trn cng

tn s gy ra hin tng nhiu ng knh. Do , thiu iu khin cng sut, mt

MS pht cng sut ln hn s chn mt b phn ln dn n hin tng gn- xa

CDMA lm gim dung lng h thng. Nh vy dung lng h thng tc cc i cn iu khin cng sut pht ca tt c cc MS trong mt sao cho

mc cng sut m chng to ra BS s bng nhau. Trong h thng WCDMA tn

ti cc phng php iu chnh cng sut sau:

- iu khin cng sut vng h (ch c trm MS tham gia qu trnh iu khin)

- iu khin cng sut vng kn (c trm gc v trm di ng u tham gia

qu trnh iu khin) gm iu khin cng sut vng trong v iu khin

cng sut vng ngoi.

Ngoi ra gim nhiu do cc BTS gn nhau gy ra trong WCDMA cng thc

hin iu khin cng sut ng xung BTS da trn bo co kt qu FER

(Frame Error Ratio) o c t MS. Trn ng xung, khng c hiu ng gn-xa

do m hnh mt-ti nhiu. iu khincng sut c nhim v b nhiu bn trong

cell gy ra bi cc trm di ng, c bit l nhiu gn bin gii ca ca cc cell ny

(c ch ra trong hnh 3-1). Hn th na, iu khin cng sut trn ng xung

c nhim v lm gim thiu nhiu bng cch gi QoS ti mc gi tr mc tiu.

Hnh 3-1: B nhiu bn trong cell (iu khin cng sut ng xung)

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Trong hnh 3-1, MS2 phi chu nhiu nhiu bn trong cell hn MS1. V th

p ng mc tiu cht lng ging nhau, cn nhiu nng lng cp pht cho cho

cc knh ng xung gia BS v MS2.

3.1.2 Nguyn l iu khin cng sut vng hiu khin cng sut vng h ch yu iu khin cng sut ng ln, thchin nh gi gn ng cng sut ng xung ca tn hiu knh hoa tiu da trn

tn hao truyn sng ca tn hiu ny. Trong h thng WCDMA phng php iu

khin cng sut ny thng c s dng thit lp cng sut gn ng khi truy

nhp mng. Hnh 3-2 cho ta thy qu trnh iu khin cng sut khi MS truy nhp

mng trn knh RACH.

Hnh 3-2 Qu trnh iu khin cng sut vng m khi MS truy nhp mng trn

knh RACH

truy nhp mng MS thc hin th truy nhp bng cch pht i nhiu chui

thm d truy nhp. Lc u chui thm d truy nhp c pht i mt cng sut

tng i thp trn c s nh gi cng sut m MS thu c (cng sut pht nyc xc nh theo nguyn tc l: khi thu c mt hoa tiu mnh t trm gc c

ngha l suy hao ng xung thp, nu coi suy hao ng ln cng nh vy th

trm di ng ch cn pht mt cng sut thp v ngc li). Nu khng nhn c

tr li t BTS trn knh PCH, MS pht thm d truy nhp tip theo vi mc cng

sut cao hn v qu trnh ny c lp nhiu ln cho n khi n nhn c tr li t

BTS.

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Mi bc cng sut Pi c gi l mt hiu chnh cng sut vng h. Khi ny cng

sut pht khi u ca trm di ng c xc nh nh sau:

Pt= -Pr-72+ NOM_PWR+INT_PWR

V cng sut pht ca trm di ng sau khi nhn c tr li ca BTS

Pt= -Pr-72+ NOM_PWR+INT_PWR+Tng cng sut ca cc ln hiu

chnh thm d truy nhp (Pi).

Trong :

Pt: Cng sut pht trung bnh (dB)

Pr: Cng sut thu trung bnh (dB)

NOM_PWR: iu chnh danh nh

INT_PWR: iu chnh ban u

c tnh c-ng hoa tiu

P_tx =1/C- ng hoa tiu

Hnh 3-3 : Nguyn tc iu khin cng sut vng h

Qu trnh iu khin theo vng m ny din ra lin tc sau khi trm gc xc

nhn yu cu truy nhp ca my di ng

Tuy nhin nhc im ln nht ca phng php ny l: do iu kin truyn

sng ca ng xung khc ng ln nht l do pha inh nhanh nn s nh gi sthiu chnh xc.

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3.1.3 Nguyn l iu khin cng sut vng kn

Phng php iu khin cng sut vng kn c m t nh hnh v

Cc lnhiukhincngsut ncc MS

MS 1

MS 2

Duytrcc mc

cngsut P1vP2bngnhau

Hnh 3-4 C ch iu khin cng sut vng kn

phng php ny BTS thng xuyn nh gi t s tn hiu trn can nhiu

(SIR) thu c v so snh n vi t s SIR ch im t

SIRsetpoint= (Eb/N0)req req = request

Nu SIR thu cao hn SIRsetpoint th BTS ra lnh cho MS h thp cng sut, tri li

n ra lnh cho MS tng cng sut. Chu k o lnh phn ng ny c thc hin

1500 ln trong mt giy. Tc ny s cao hn mi s thay i tn hao ng

truyn v thm ch c th nhanh hn pha inh nhanh khi MS di chuyn vi tc

thp. Bit iu khin cng sut (PCb) c ghp vo knh TCH ng xung. Cc

bit iu khin cng sut c ghp vo knh lu lng theo hng sau b m ha,

v th cc PCb khng c m ha chng li. iu ny c thc hin gim trc hu khi gii m ha. V iu khin cng sut theo vng kn c s dng

chng lai hin tng pha inh nhanh. Cc PCb khng c m ha my thu di

ng nhanh chng c th thu li PCb v iu chnh cng sut pht cho ph hp.

Mi bit iu khin cng sut ny to ra thay i 1,2,3 dB gn hn n gi tr ch.

Cn lu rng c th vic iu chnh cng sut ny khng thnh cng v N0 lun

lun thay i

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Hnh 3-5 Nguyn l iu khin cng sut vng kn

K thut iu khin cng sut vng kn nh vy c gi l vng trong cngc s dng cho ng xung mc d y khng c hin tng xa- gn. Tuy

nhin l do bt buc iu khin cng sut y nh sau: Khi MS tin gn ti bin

gii , n bt u chu nh hng ngy cng tng ca nhiu t cc khc. iu

khin cng sut trong trng hp ny to mt lng d tr cng sut cho cc

MS trong trng hp cc trng hp ni trn

-iu khin cng sut vng ngoi

iu khin cng sut vng ngoi thc hin iu chnh gi tr SIRsetpoint BTS cho

ph hp vi yu cu ca tng ng truyn v tuyn t c cht lng cc

ng truyn v tuyn nh nhau. Cht lng ca cc ng truyn v tuyn thng

c nh gi bng t s li bit BER hay t s li khung FER. L do cn t li

SIRsetpoint nh sau: SIR yu cu chng hn l FER=1% ph thuc vo tc ca

MS v c im truyn a ng. Nu ta t SIRsetpoint ch cho trng hp xu

nht (tc ca MS l cao nht) th s lng ph dung lng cho cc kt ni tc

Gii triph

My thuRAKE

o SIR

So snh vquyt nh SIR ch

o chtlng

So snh vquyt nh

To bit iukhin cng

sut

Chtlng

ch

Vngtrong

Vngngoi

Tnhiuthu

Ghp bit iu khin csvo lung pht

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thp. Nh vy, tt nht l SIRsetpoint th ni xung quanh gi tr ti thiu p ng

c yu cu cht lng.

Hnh 3-6 iu khin cng sut vng ngoiHnh 3-6 cho thy s thay i ca SIRsetpoint theo thi gian. thc hin iu

khin cng sut vng ngoi, mi khung s liu ca ngi s dng c gn ch th

cht lng khung l CRC. Vic kim tra ch th cht lng ny s thng bo cho

RNC v vic gim cht lng v RNC s lnh cho BTS tng SIRsetpoint. L do t

iu khin vng ngoi RNC v chc nng ny thc hin sau khi thc hin kt hp

cc tn hiu chuyn giao mm.

Tn s ca iu khin cng sut vng bn ngoi thng l 10-100Hz.

3.1.4 Qu trnh thc iu khin cng sut ng ln

Cng sut pht ca my di ng l mt hm ca qu trnh iu khin cng suttheo vng h v vng khp kn. Cc hnh 3-7 v hnh 3-8 ch ra qu trnh thc hin

lc iu chnh cng sut ng ln. i vi qu trnh iu khin cng sut

vng khp kn, trm gc c ton b vng iu khin ngoi v mt phn ca vng

iu khin trong; my di ng c cc phn khc ca vng iu khin trong. i vi

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qu trnh iu khin cng sut theo vng m, ton b phn iu khin theo vng m

nm trong my di ng.

Quyt nh:

Nu gi trEb/N0- c tnh >ngng thPCb=1(UE gim 1dB) Nu gi trEb/N0- c tnh


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c tnh cngsut thutrung bnh

Quyt inh: Nu PCb=0 tng cng

sut pht 1dB Nu PC b=1 gim cng

sut pht 1dB

G ii iuch

My thu

M y pht Kh nh l- u l- ng - ng lnS liu

P C b

S liu thuVng khp kn

antenthu

antenpht

K = 72 dB

NOM_ PW R (dB)

Tng tt c c c gi tri hiuchnh th m d truy nhp

INIT_P WR (dB)

P r

Hnh 3-8 Qu trnh iu khin cng sut ng ln c thc hin trm di ng

V pha my di ng (xem hnh 3-8), my di ng thu tn hiu t ng truynxung. N khi phc li cc bit PCb a ra quyt nh tng hoc gim cng sut

pht i 1,2,3 dB. Vic quyt nh l s hiu chnh theo vng khp kn

3.1.5 Qu trnh thc iu khin cng sut ng xung

Trong trng hp l tng th vic iu khin cng sut ng xung l

khng cn thit. L do l trm gc ang pht tt c cc knh nht qun trong cngmt bng tn RF, theo m hnh mt ti nhiu. Tuy nhin, trong thc t mt my di

ng c th gn mt ngun nhiu nghim trng v phi chu mt nn nhiu ln,

hoc my di ng c th phi chu mt suy hao ng truyn ln trn tn hiu tng

hp thu c ngoi tp m nhit. Ngoi ra, th iu khin cng sut ng xung

cn b v gim nhiu giao thoa gia cc cell ln cn. Nh vy, vic iu chnh

cng sut hng xung l vn cn thit. Tuy nhin, ni chung l yu cu iu khin

cng sut i vi hng xung l khng nghim ngt nh yu cu i vi iu

khin ng ln

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thc hin qu trnh iu khin ny th trm di ng c quy nh lun phi

bo co phn hi cht lng ca ng truyn xung ti trm gc. My di ng

lin tc gim st FER ca ng truyn xung v n bo co gi tr FER ny v

trm gc trn mt bn tin c gi l: bn tin bo co php o cng sut (PMRM).

Trm di ng thng gi bn tin ny theo mt trong hai cch sau: mt cch l my

di ng bo co thng k bn tin PMRM (Power Measurement Report Message)

v cch th hai l my di ng ch bo co PRMR khi gi tr FER ca ng truyn

xung vt qu ngng nht nh. Trm gc thi bn tin PMRM, nhn bit cht

lng ca ng truyn xung, sau c th iu chnh cng sut pht ca n ti

my di ng. Thut ton chnh xc ca qu trnh iu khin cng sut ny ph thuc

vo cc nh sn xut cu trc h tng ring bit. Qu trnh ny hu nh lun l c

quyn ca mi nh sn xut

3.1.6 iu khin cng sut trng thi chuyn giao mm

trng thi chuyn giao mm (trng m kt ni mi c thit lp trc khi ct

kt ni c), cng sut pht ca UE c iu chnh da trn vic la chn lnh iu

khin cng sut TPC ph hp nht t nhng lnh iu khin cng sut m n nhn

c t cc BS c kt ni n UE . Trong trng hp UE nhn cc lnh iu

khin cng sut c ni dung khc nhau. Cc lnh ny khc nhau c th do li trongkhi truyn dn cng c th do mng. Do vy, UE phi x l tnh hung c mu

thun gia cc lnh iu khin cng sut. gii quyt mu thun UE thc hin

lnh iu khin cng sut theo nguyn tc: nu cc lnh cng sut ging nhau l

cng tng th UE tng cng sut pht ca mnh, cn cc trng hp khc th UE s

gim cng sut pht. Qu trnh iu khin cng sut trong trng hp ny c m

t nh hnh v

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=>UE gim cng sut

TPC: "gim cng sut"

=>UE gim cng sut

TPC: "gimcng sut" TPC: "t ng cng sut" TPC: "gimcng sut"

=>UE t ng cng sut

TP C: "tng cngsut" TPC: "t ng cng sut"

Hnh 3-9: iu khin cng sut trng thi chuyn giao mm

3.2 CHUYN GIAO

Nh chng II chng ta bit bt k h thng thng tin di ng t bo no

cng phi p dng k thut chuyn giao p ng cc yu cu v cht lng dch

v, kh nng di ng ca cc thu bao, iu chnh ti ca h thng trnh tc

nghn mng. Trong h thng WCDMA do vic dng chung cng mt bng tn v

p dng k thut tri ph nn c kh nng h tr y chuyn giao mm. c bit

WCDMA kt hp chuyn giao mm vi vic iu khin cng sut nhanh v nghim

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ngt cng lm tng thm hiu qu trong vic chng nhiu v gii quyt vn gn-

xa. Tuy nhin do WCDMA l bc tin ha ca h thng GSM tin ln 3G ln

trong WCDMA cng p dng c k thut chuyn giao cng. Ngoi ra, th tuy rng

h s ti s dng tn s trong WCDMA c th bng mt nhng trong WCDMA vn

p dng quy hoch ti s dng tn s cho cc vng inh v LA khc nhau v vy

vic p dng chuyn giao cng l vn cn thit trong WCDMA.

3.2.1 Cc kiu chuyn giao trong WCDMA

- Chuyn giao cng c th c chia thnh: chuyn giao cng cng tn s v

chuyn giao cng khc tn s. Trong qu trnh chuyn giao cng, kt ni c c

gii phng trc khi thc hin kt ni mi. Do vy, tn hiu b ngt trong khong

thi gian thc hin chuyn giao. Tuy nhin, thu bao khng c kh nng nhn bitc khong ngng . Trong trng hp chuyn giao cng khc tn s, tn s

sng mang ca knh truy nhp v tuyn mi khc vi tn s sng mang hin ti.

Hnh 3- 10 th hin chuyn giao cng cng tn s.

Tn s f1 Tn s f1

BSBS

UE

Iur

RNC RNC

Hnh 3-10: chuyn giao cng cng tn s

Trn hnh 3- 10,do k hoch quy hoch mng, RNC bn cnh khng c kt

ni vi giao din Iur v vy chuyn giao mm gia cc RNC khng thc hin c.

Trong tnh hung nh vy, chuyn giao cng cng tn s l loi chuyn giao duy

nht h tr kt ni v tuyn khi thu bao di ng t BS ny sang BS mi. Trn thc

t, iu ny lm xut hin s kin chuyn giao RNC, trong MSC cng lin quan

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n qu trnh chuyn giao. Thng thng, h s ti s dng tn s i vi WCDMA

bng mt, iu c ngha l cc BS s dng chung mt tn s v tt c cc UE

dng chung tn s trong ton b mng. iu khng c ngha l vic s dng li

tn s khng c thc hin h thng WCDMA. Do , nu cc sng mang khc

nhau c phn b cho cc cell, chuyn giao khc tn s c s dng m bo

ng chuyn giao t cell ny sang cell khc.

Chuyn giao lin tn s cng c s dng trong mng t bo v c cu trc

(HCS) gia cc lp cell ring r, chng hn gia cc cell vi m v cc cell v m,

cc cell ny s dng tn s sng mang khc nhau trong cng mt vng ph sng.

Chuyn giao khc tn s c thc hin khng ch duy tr kt ni (nu khng

thc hin chuyn giao kt ni c th b ngt) m cn m bo yu cu QoS.

Chuyn giao cng lin tn thng thng l NEHO. Chuyn giao lin tn s c thxy ra gia hai mng truy nhp v tuyn khc nhau, v d gia GSM v WCDMA.

Khi , loi chuyn giao ny gi l chuyn giao lin h thng xem hnh 3- 11.

Chuyn giao lin h thng cng l chuyn giao lin tn nhng cc tn s khc nhau

thuc cc h thng khc nhau

Tns f2Tn s f1

BS BS

UE

Hnh 3-11 : Chuyn giao cng khc tn s

Chc nng chuyn giao lin h thng trong WCDMA c thc hin bi mtch lm vic c bit: ch nn. Khi UE ch nn, c th gim h s tri

ph ca knh. Do vy, kt ni giao din v tuyn ch s dng mt phn nh ca

khung WCDMA. Cc khe thi gian cn li c th s dng cho cc mc ch khc,

v d nh o mc tn hiu can nhiu t cc cell GSM bn cch. Ch nn c th

t c bng cch gim tc s liu lp cao hoc gim tc k hiu khi ghp

knh lp vt l. Khi UE s dng giao din Uu ch ny, ni dung ca khung

WCDMA c nn mt bit to ra mt ca s m qua UE c th nhn v gii

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m thng tin t knh qung b (BCH) ca h thng GSM. Ngoi ra, c RAN ca

UMTS v phn h trm gc BSS ca GSM phi c kh nng gi cc thng tin ch

th khc trn cc knh BCH UE c kh nng thc hin vic gii m chnh xc.

Chuyn giao lin h thng gia WCDMA v GSM c thc hin nhng khu

vc m c hai h thng ny cng tn ti. Chuyn giao lin h thng c yu cu

b xung vng ph gia hai h thng nhm m bo phc v lin tc. Chuyn giao

lin h thng c th c s dng iu chnh ti gia cc h thng GSM v

WCDMA, khi vng ph gia hai h thng chng ln ln nhau. Ngoi ra, chuyn

giao ny c th thc hin theo yu cu ca ngi s dng. Chuyn giao lin h

thng l loi chuyn giao NEHO. Tuy nhin, UE phi c kh nng h tr hon ton

loi chuyn giao ny. RNC pht hin chuyn giao lin h thng da trn cu hnh

mng v tuyn (cc nh ngha v cell ln cn) v cc tham s iu khin khc.- Khc vi chuyn giao cng, chuyn giao mm c thc hin theo nguyn l :

thit lp kt ni mi trc khi gii phng kt ni c. Trong h thng WCDMA, hu

ht chuyn giao l chuyn giao mm cng tn s

Tn s f1Tn s f1

BS BS

UE

Hnh 3-12: Chuyn giao mm cng tn s

Chuyn giao mm c thc hin gia cc cell thuc cc BS khc nhau nhng

khng nht thit phi cng mt RNC. Trong trng hp RNC c lin quan n

chuyn giao mm, RNC phi thc hin vic iu khin chuyn giao qua giao din

Iur. Trong trng hp chuyn giao mm, cc cell ngun v cell ch c cng tn s.

Trong trng hp cuc gi chuyn mch knh, cc my di ng thc t thc hin

chuyn giao mm hu nh lin tc nu vng ph sng c cu trc cell nh.

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Chuyn giao mm hn l loi chuyn giao trong tn hiu mi c thm vo

hoc xa khi tp tch cc, hoc thay th bi tn hiu mnh hn trong cc secter

khc nhau ca cng BS (xem hnh)

Secter 2f1

Secter 3f1

Secter 1f1Tn hiu a

-ng quasecter 1

Tn hiu a

-ng quasecter 3

Hnh 3-13: Chuyn giao mm hn cng tn s

Trong trng hp chuyn mm hn, BS pht trong mt secter nhng thu tnhiu secter khc. Trong trng hp ny, UE c cc kt ni v tuyn tch cc

ng ln ti mng qua nhiu secter ca cng mt BS. Nguyn nhn dn n

chuyn giao trong cc on l : do cc BTS thng s dng anten c tnh hng

ln ph ht mt 3600 ngi ta thng dng 3 on 1200 hay 6 on 600

3.2.2 Thut ton chuyn giao trong WCDMA

Nguyn tc chung thc hin thut ton chuyn giao c th hin trn hnh 3-14iu kin u l cc iu kin thc hin quyt nh ca thut ton da trn mc tnhiu hoa tiu do UE thng bo. Cc thut ng v cc tham s sau c s dng

trong thut ton chuyn giao :

- Ngng gii hn trn : l mc tn hiu ca kt ni t gi tr cc i cho

php tha mn mt cht lng dch v QoS yu cu.

- Ngng gii hn di : l mc tn hiu ca kt ni t gi tr cc tiu cho

php tha mn mt cht lng dch v QoS yu cu. Do mc tn hiu

ca kt ni khng c nm di mc .

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- Gii hn chuyn giao : l tham s c nh ngha trc, c thit lp ti

im m cng tn hiu ca cell bn cnh (cell B) vt qu cng

tn hiu ca cell hin ti (cell A) mt lng nht nh.

- Tp tch cc : l mt danh sch cc nhnh tn hiu hoa tiu (cc cell) m

UE thc hin kt ni ng thi ti mang truy nhp v tuyn (RAN).

- Tp ng c: tp ny cha cc hoa tiu khng c trong tp tch cc. Tuy

nhin MS vn thu c cc hoa tiu ny vi cng tn hiu ln

ch ra rng cc knh lu lng ng xung c th c gii iu ch

thnh cng.

- Tp ln cn : tp ny cha cc hoa tiu ln cn hin thi khng c trong

tp tch cc v tp ng c nhng c kh nng lm ng c cho chuyn

giao. Cc hoa tiu ln cn ca mt hoa tiu l tt c cc hoa tiu ca cc ,on nm gn hoa tiu ny. Danh sch hoa tiu ln cn c pht n

MS bn tin thng s h thng trn knh tm gi.

- Tp cn li : tp ny cha tt c cc hoa tiu c trong h thng tr cc hoa

tiu tp tch cc, ng c v ln cn.

Gi i hn chuyngiaoTn hiu tng

C-

ngtnhiu Ng- ng trn

Ng- ng d- i

Thi gian

(1) (2) (3)

Cell A Cell B

Tn hiu A Tn hiu B

Hnh 3-14: Nguyn tc chung ca cc thut ton chuyn giao

Gi s thu bao UE trong cell A ang chuyn ng v pha cell B, tn hiu hoa

tiu ca cell A (ti UE ang thc hin kt ni) b suy gim n ngng gii hn

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di nh hnh trn. Khi t ti mc ngng gii hn di, xut hin kch thch

chuyn giao theo cc bc sau y :

(1) Cng tn hiu A bng vi mc ngng gii hn di. Mt khc, ty

theo gi tr o ca UE, RNC pht hin c tn hiu ca cell bn cnh (tn hiu

B), tn hiu ny c cng ci thin cht lng kt ni. Do , RNC

s nhp tn hiu B vo tp tch cc. Khi UE c hai kt ni ng thi ti

UTRAN. UE s thu tn hiu tng hp ca hai kt ni ny.

(2) Ti v tr ny, cht lng tn hiu B tt hn tn hiu A. Do , RNC coi v

tr l im khi u khi tnh ton gii hn chuyn giao.

(3) Cng tn hiu B bng hoc tt hn ngng gii hn di. Do mc

tn hiu ny tha mn yu cu cht lng dch v QoS ca kt ni.

Bn cnh , tng tn hiu ti UE vt qu ngng gii hn trn v c khnng gy ra nhiu cho h thng. Do vy, RNC s xa tn hiu A khi tp

tch cc.

Kch c ca tp tch cc c th thay i c, thng thng tp tch cc c kch

thc trong khong t 1 n 3 tn hiu.

Do hng chuyn ng ca UE thay i ngu nhin, UE c th quay tr li cell

A ngay sau khi thc hin chuyn giao ln th nht. iu ny s lm xy ra hiu ng

gi l ping-pong. Hiu ng ny lm nh hng khng c li i vi lu lng h

thng cng nh hot ng ca ton b h thng. Vic s dng gii hn chuyn giaoc th trnh c mt s chuyn giao khng cn thit.

Nh trn chng ta bit l thc hin chuyn giao th MS lun lun phi thc

hin gim st cht lng dch v QoS v tm kim, o cng ca cc hoa tiu,

sp xp vo cc tp tng ng. Trong h thng CDMA s dng mt k thut tm

kim hoa tiu gi l ca s tm. Trm di ng thc hin tm kim knh hoa tiu

trong mt khong thi gian cho trc bng s chip ca mt chui hoa tiu PN.

MS s dng ba ca s tm kim sau :

1. SRCH_A : l ca s tm m MS s dng bm tp tch cc v tp ng c

2. SRCH_N : l ca s tm m MS s dng gim st cc hoa tiu ln cn

3. SRCH_R : l ca s tm m MS s dng gim st cc hoa tiu tp cn li

Khi qu trnh quyt nh chuyn giao c thc hin theo lu hnh 3-15

Trong

T_ADD: Ngng pht hin hoa tiu

T_COMP : Ngng so snh

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Tmhoa tiutip theo (Px)Tpln cn hay cn li

P(x) v-t ng-ngT_Add

Sai

ng

1.Chuyn hoa tiu vo tpngc2.Gi bn tino c-ng tnhiu

hoa tiu ntrmgc

Sai ng

1. Gi bn tin o hoa tiu ntrmgc2. Thu bn tin h-ng dnchuyngiao ttrmgc3. Chuyn hoa tiuvo tp tch cc (trmding vo chuyn giao mm4. Gi bn tin hon thnhchuyngiao ntrmgc

P(x) v-t T_Comp

so vi 1hoa tiutch cc

VnP(x) tp ngc

Hnh 3-15Lu thut ton quyt nh chuyn giao

3.2.3 Lu thc hin chuyn giao

Sau khi quyt nh chuyn giao thi MS s tin hnh chuyn giao theo hng dn

ca BS. Qu trnh chuyn giao c biu din nh cc hnh di

Hnh 3-16 biu din qu trnh bt u chuyn giao mm

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1

23

4

5

6

7

8

Quyt nhchuyn giao

o c-ng hoa tiu

L-u l- ng rng

o c- ng hoa tiu

MSBS

Phc vMSC BS

ch

9

10

11

12

13

14

15

Yu cu chuyngiao gia c c BSYu cu chuyngiao gia c c BS

Join Request

J oin Acknowledge

InterBase Handoff Ack

InterBase Handoff Ack

Chthchuyn giao

Hon thnh chuyn giao

Thng b o chuyn giao

Handoff Information Ack

Lnh yu cu o hoa tiu

Hnh 3-16 : Chuyn giao mm bt u

1. MS xc nh rng mt trm BS khc c cng tn hiu hoa tiu tr thnh ch ca chuyn giao.2. MS pht bn tin Pilot Strength Measurement (o cng hoa tiu) n

BTS ang phc v n.3. BS ang phc v pht bn tin Interbase Station Handoff ( yu cu chuyn

giao) n MSC ch.4. MSC pht bn tin Interbase station Handoff ti BS ch.5. BS ch thit lp thng tin vi MS bng cch pht bn tin Null Traffic n

MS.6. BS ch pht bn tin Join Request ( yu cu kt ni lin lc ) n MSC.

7. MSC xem xt cc kt ni vi hai BS thc hin chuyn giao m khng lmgin on kt ni, sau pht bn tin Join Request Acknowledge (xc nhnkt ni) n BS ch.

8. BS ch pht bn tin Interbase Handoff Acknowledge n MSC.9. MSC pht bn tin Interbase handoff Acknowledge n BS ang phc v.10. BS ang phc v pht bn tin ra Handoff Direction n MS.11. Ms pht bn tin Handoff Complete n BS ang phc v.12.BS phc v mi pht bn tin Handoff Information ( thng bo chuyn giao)

n MSC.13. MSC khng nh bn tin ny bng bn tin Handoff Information Ack.

14. BS ch pht lnh Pilot Measurement n MS.

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15. Ms pht bn tin Pilot Strength Measurement n BS ch.Trong qu trnh chuyn giao th MS thng tin ng thi vi c hai BS v qu trnh

chuyn giao s kt thc khi tn hiu ca BS c khng cn mnh. Khi ny MS s

loi b trm gc c thc hin lin lc trn trm gc mi

Yu cu t bXc nhn t b

Lnh yu cu o hoa tiu

1

2

3

4

56

7

8

Quyt nhchuyn giao

o c- ng hoa tiu

Interface Primary Transfer

o c- ng hoa tiu

MSBS

Phc vMSC BS

ch

9

10

11

12

Interface Primary Transfer Acknowledge

Handoff Information

HO Information Ack

Chthchuyn giao

Hon thnh chuyn giao

Hnh 3-17 : Kt thc qu trnh chuyn giao MS ri b BS phc v

1. MS xc nh rng trm BS ang phc v n khng cng tn hiu tip tc trng thi chuyn giao mm.

2. MS pht bn tin Pilot Strength Measurement n BS. Bn tin ny yucu BS ri b chuyn giao.

3. BS ang phc v pht bn tin Handoff Direction n MS. Bn tin nych th rng BS ang phc v s ri khi chuyn giao.

4. MS pht bn tin Handoff Complete n BS ang phc v.5. BS ang phc v pht bn tin Interface Primary Transfer ( chuyn s cp

giao din) n BS ch cng vi thng tinbn ghi cuc gi tng ng.6. BS ch khng nh bn tin ny bng bn tin Interfacce Primary

Transfer ck ( xc nhn chuyn s cp giao din).7. BS ch pht bn tin Handoff Information n MSC.

8. MSC pht bn tin Handoff Information Ack n BS ch.

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9. BS ch pht lnh Pilot Measurement Request ( yu cu o hoa tiu)n MS.

10.Ms pht bn tin Pilot Strength Measurement n BS ch.11.BS ang phc v bn tin Remove Request ( yu cu ri b) n MSC

yu cu ri b kt ni.12.MSC khng nh bn tin ny bng bn tin Remove Ack n trm BS

gc.By gi MS lm vic vi BS ch ( BS phc v mi). Nu cn cc chuyn giao

mm b sung th qu trnh chuyn giao c lp li

3.2.4 u nhc im ca chuyn giao mm

Chuyn giao mm l loi chuyn giao c th ca h thng thng tin di ng

WCDMA da trn nguyn tc ni trc khi ct. So vi chuyn giao cng th HO c

mt s u nhc im sau :

a/ u im

- iu ha ti trn mng : trong trng hp ti ca 1 cell v l do no y

tng t ngt th h thng s chuyn giao sang cc cell ln cn c lu

lng thp hn

- Lm cho thng tin ca ngi s dng lin tc hn khng b ngt qung

nh trong chuyn giao cng

- Cung cp cht lng thng tin tt hn, khng b rt cuc gi

- Vic phn b ti ca cc cell lm dung lng h thng tng- Mt u im na ca chuyn giao mm l khi kt hp vi iu khin cng

sut. V thng v tr chuyn giao l ni m cng tn hiu yu ln nu

chuyn giao mm kt hp vi iu khin cng sut s lm gim nhiu ln

cc MS khc

Tuy nhin bn cnh nhng u im k trn th chuyn giao mm cng c mt

s nhc im

b/ Nhc im

- Chuyn giao mm lm gim dung lng ng xung ca h thng dotrong qu trnh thc hin chuyn giao MS thng tin ng thi vi c hai

trm gc tc l n c cp hai knh lu lng lm gim ti nguyn

mng. C MS v BS lun phi gim st cht lng h thng

- K thut chuyn giao mm phc tp hn chuyn giao cng

Tuy cn c nhng nhc im k trn nhng chuyn giao mm vn l k thut

chuyn giao p ng c cc yu cu kht khe ca h thng thng tin di ng

th h 3 vi nhiu dch v cht lng cao

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KT LUN

iu khin cng sut l qu trnh iu khin cng sut ca my pht trong qutrnh hot ng. iu khin cng sut c quan h mt thit vi chuyn giao mm.

Nu kt hp tt hai k thut ny th s gim ng k nhiu cng nh lm tng cht

lng h thng. Li ch chnh ca vic iu khin cng sut l gii quyt vn

gn- xa, hn ch pha inh cng nh s che ti i vi tn hiu ng ln, gim

nhiu giao thoa ng xung

Trong qu trnh thc hin ti em c bn hiu r v c ch cng nh cc thut

ton iu khin cng sut v chuyn giao c p dng trong h thng WCDMA.

Tuy nhin do trnh cng nh thi gian c hn ln ti ca em kh trnh khi

nhng thiu st. Mt ln na em xin chn thnh cm n thy Bi nh Thnh cng

cc thy, c gio trong t mn, dy bo, hng dn em trong nhng nm qua.

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TI LIU THAM KHO

[1] TS. Nguyn Phm Anh Dng, CDMA one v CDMA2000., Nh xut bn bu

in 7/2003

[2] TS. ng nh Lm, TS. Chu Ngc Anh, Ths. Hong Anh, Ths. Nguyn Phi

Hng, H thng thng tin di ng 3G v xu hng pht trin., Nh xut bn khoa

hc v k thut 2004

[3] K s Nguyn Vn Thun, H thng thng tin di ng WCDMA., Hc vin

cng ngh bu chnh vin thng 12/2004

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CC T VIT TT

3G Third Generation Th h 3

A.AMR Adaptive Multi-Rate codec B m ho v gii m a tc thch nghi

B.

BER

BLER

BPSK

BTS

Bit Error Rate

Block Error Rate

Binary Phase Shift Keying

Base Tranceiver Station

Tc li bit.

Tc li Block

Kho dch pha nh phn.

Trm gc

C.CDMA

CN

CRC

Code Division Multiple Access

Core Network

Cylic Redundancy Check

Truy nhp phn chia theo m

Mng li

M vng kim tra d thaD.

DL

DSSS

Downlink

Direct Sequence Spread Spectrum

ng xung

H thng tri ph chui trc tipE.

EDGE Enhanced Data Rates for Evolution

Equivalent Isotropic Radiated Power

Cc tc d liu tng cng

cho s tin hoF.

FDD

FDMA

FER

Frequency Division Duplex

Frequency Division Multiple Access

Frame Error Rate

Phng thc song cng phn chia

theo tn s

a truy nhp phn chia theo tn

s

T s li khungG.

GGSN

GPRS

GSM

Gateway GPRS Support Node

General Packet Radio Service

Global System for Mobile

Telecommunication

Nt h tr cng GPRS

Dch v v tuyn gi chung.

H thng vin thng di ng ton

cuH.

HLR

HO

Home Location Registor

Handoff

B ng k thng tr

Chuyn giaoI.

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IMT-2000

Iub

Iur

International Mobile

Telecommunication 2000

Thng tin di ng ton cu 2000

Giao din gia RNC v nt B

Giao din gia 2 RNC.

M.ME

MSC

MS

Mobile Equipment

Mobile Service Switching Centre

Mobile Station

Thit b di ng

Trung tm chuyn mch dch v di

ng.

Trm di ngO

OVSF Orthogonal Variabel Spreading

Factor

H s tri ph bin trc giao

P.PN Pseudo Noise Gi tp mQ.

QPSK Quardrature Phase Phase Shift

Keying

Kho dch pha cu phng.

R.RAN

RNC

RNSRRC

RRM

Radio Access Network

Radio Network Controller

Radio Network subsystemRadio Resoure Control protocol

Radio Resouse Management

Mng truy nhp v tuyn.

B iu khin mng v tuyn.

Phn h mng v tuynGiao thc iu khin ti nguyn v

tuyn

Thut ton qun l ti nguyn v

tuyn.S.

SGSN

SHO

SIRSNR

Serving GPRS Support Node.

Soft Handover

Signal to Interference RatioSignal to Noise Ratio

Nt h tr GPRS phc v

Chuyn giao mm.

T s tn hiu trn nhiuT s tn hiu trn tp m

T.

TDD

TDMA

TPC

Time Division Duplex

Time Division Multiple Access

Transmission Power Control

Phng thc song cng phn chia

theo thi gian

a truy nhp phn chia theo thi

gian

iu khin cng sut pht

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U.

UE

UL

UMTS

USIM

UTRAN

User Equipment

Uplink

Universal Mobile

Telecommunication System

UMTS Subscriber Identify Module

UMTS Terrestrial Radio Access

Network

Thit b ngi s dng

ng xung

H thng vin thng di ng ton

cu.

Modul nhn dng thu bao UMTS

Mng truy nhp v tuyn mt t

UMTSV.

VLR Visitor Location Registor B ng k tm trW.

WCDMA Wideband Code Division Multiple

Access

a truy nhp phn chia theo m

bng rng

Do an Tot Nghiep ( Pham Linh)

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