tính toán đường truyền WCDMA

8/6/2019 tnh ton ng truyn WCDMA

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LI M U

1

LI MU

Ra i vo nhng nm 40 ca th kXX, thng tin di ng c coi nh lmt thnh tu tin tin trong lnh vc thng tin vin thng vi c im cc thi t b

u cui c th truy cp dch vngay khi ang di ng trong phm vi vng phsng.

Thnh cng ca con ngi trong lnh vc thng tin di ng khng ch dng li trong

vic mrng vng phsng phc vthu bao khp ni trn ton th gii, cc nh

cung dch v, cc t chc nghin cu pht trin cng nghdi ng ang n lc hng

ti mt h thng thng tin di ng hon ho, cc dch va dng, cht lng dch v

cao. 3G - H thng thng tin di ng th h3 l ci ch trc mt m th gii ang

hng ti.

T thp nin 1990, Lin minh Vin thng Quc t bt tay vo vic pht trin

mt nn tng chung cho cc h thng vin thng di ng. Kt qu l mt sn phm

c gi l Thng tin di ng ton cu 2000 (IMT-2000). IMT-2000 khng chl mt

b dch v, n p ng c m lin lc t bt cni u v vo bt clc no.

c nh vy, IMT-2000 to iu kin tch hp cc mng mt t v/hoc v tinh.

Hn th na, IMT-2000 cng cp n Internet khng dy, hi tcc mng cnh

v di ng, qun l di ng (chuyn vng), cc tnh nng a phng tin di ng, hot

ng xuyn mng v lin mng..

Cc h thng thng tin di ng th h2 c xy dng theo tiu chun GSM,

IS-95, PDC, IS-38 pht trin rt nhanh vo nhng nm 1990. Trong hn mt tthu

bao in thoi di ng trn th gii, khong 863,6 triu thu bao s dng cng nghGSM, 120 triu dng CDMA v 290 triu cn li dng FDMA hoc TDMA. Khi

chng ta tin ti 3G, cc h thng GSM v CDMA s tip tc pht trin trong khi

TDMA v FDMA schm dn vo qun lng. Con ng GSM s ti l CDMA bng

thng rng (WCDMA) trong khi CDMA s l cdma2000.

Ti Vit Nam, th trng di ng trong nhng nm gn y cng ang pht

trin vi tc tng i nhanh. Cng vi hai nh cung cp dch vdi ng ln nht

l Vinaphone v Mobifone, Cng Ty Vin thng Qun i (Vietel), S-fone v mi

nht lCng ty c phn Vin thng H Ni v Vin Thng in Lc tham gia vo th


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trng di ng chc hn s to ra mt s cnh tranh ln gia cc nh cung cp dch v,

em li mt s la chn phong ph cho ngi s dng. V vy, cc nh cung cp dch

vdi ng Vit Nam khng ch s dng cc bin php cnh tranh vgi cm cn

phi n lc tng cng slng dch vv nng cao cht lng dch v chim lnhth phn trong nc . iu c ngha rng hng ti 3G khng phi l mt tng lai

xa Vit Nam. Trong scc nh cung cp dch vdi ng Vit Nam, ngoi hai nh

cung cp dch vdi ng ln nht l Vinaphone v Mobifone, cn c Vietel ang p

dng cng nghGSM v cung cp dch vdi ng cho phn ln thu bao di ng

Vit Nam. V vy khi tin ln 3G, chc chn hng p dng cng ngh truy nhp v

tuyn WCDMA xy dng h thng thng tin di ng th h 3 phi c xem xt

nghin cu.

Bai giang ny khng nghin cu c th l trnh pht trin t mng thng tin di

ng th h 2 GSM tin ln UMTS nh thno, m nghin cu nhng kha cnh k

thut ca cng ngh truy nhp v tuyn WCDMA (ch FDD) trong h thng

UMTS. Bai giang gm c 4 chng:

Chng 1. Xu hng pht trin ca h thng thng tin di ng ton cu:

Chng ny trnh by xu hng pht trin ln 3G cu, cc t chc chun ho vqu trnh chun ha cc h thng thng tin di ng ton cu.

Chng 2. Nghin cu tng quan cng ngh truy nhp WCDMA trong h

thng UMTS: Chng ny nghin cu t nhng vn l thuyt lin quan n

cng nghWCDMA n nhng c trng ca cng ngh WCDMA, ca h thng

UMTS.

Chng 3. iu khin cng sut v iu khin chuyn giao trong qun l tinguyn v tuyn WCDMA: Chng ny cp cc thut ton qun l ti nguyn

v tuyn trong h thng WCDMA, trong trnh by c th viu khin cng

sut v iu khin chuyn giao, 2 thut ton quan trng v c trng nht trong h

thng WCDMA.

Chng 4. Quy hoch mng v tuyn: Chng ny trnh by v mt bi ton

quan trng khi thit kv xy dng h thng thng tin di ng th h 3 s dng

cng ngh truy nhp v tuyn WCDMA vi nhng c trng ring.


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H ni, ngy 15 thng 8 nm 2009


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Chng 1-Xu hng pht trin ca h thng thng tin di ng ton cu

4

Chng 1. XU HNG PHT TRIN H THNG

THNG TIN NG TON CU

1.1 Xu hng pht trin h thng thng tindi ng trn th gii.

H thng thng tin di ng th h th nht s dng cng ngha truy nhp theo

tn s(FDMA) l h thng tbo tng tdung lng thp v chc dch v thoi,

tn ti l cc h thng NMT (Bc u), TACS (Anh), AMPS (M). n nhng nm

1980 trnn qu ti khi nhu cu v sngi s dng ngy cng tng ln. Lc ny,

cc nh pht trin cng nghdi ng trn th gii nhn nh cn phi xy dng mt hthng tbo th h2 m hon ton s dng cng ngh s. phi l cc h thng x

l tn hiu s cung cp c dung lng ln, cht lng thoi c ci thin, c th

p ng cc dch truyn s liu tc thp. Cc h thng 2G l GSM (Global System

for Mobile Communication - Chu u), h thng D-AMPS (M) s dng cng ngh

a truy nhp phn chia theo thi gian TDMA, v IS-95 Mv Hn Quc s dng

cng ngha truy nhp phn chia theo m CDMA bng hp. Mc d h thng thng

tin di ng 2G c coi l nhng tin bng knhng vn gp phi cc hn ch sau:

Tc thp (GSM l 10kbps) v ti nguyn hn hp. V th cn thit phi chuyn i

ln mng thng tin di ng th h tip theo ci thin dch v truyn s liu, nng

cao tc bit v ti nguyn c chia s

Mng thng tin di ng 2G rt thnh cng trong vic cung cp dch v ti

ngi s dng trn ton th gii, nhng slng ngi s dng tng nhanh hn nhiu

so vi d kin ban u. C tha ra cc thng k v stng trng ca thtrng di

ng phn on theo cng nghnh hnh 1-1.Cn ccc s liu thng k trn ta thy GSM l mt chun v tuyn di ng 2G

slng thu bao ln nht trn ton th gii. Nhng tc d liu b hn chv s

lng ngi dng tng ln c bit l ngi s dng a phng tin c nguy c khng

p ng nhu cu ca thtrng.


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Hnh 1- 1 Thng k s tng trng th trng di ng phn loi theo cng ngh

Mt khc, khi cc h thng thng tin di ng ngy cng pht trin, khng ch s

lng ngi s dng in thoi di ng tng ln, m rng th trng, m ngi s

dng cn i hi cc dch vtin tin hn khng chl cc dch v cuc gi thoi v

dch v s liu tc thp hin c trong mng 2G. Nhu cu ca thtrng c thphn

loi thnh cc lnh vc sau:

Dch v d liu my tnh(Computer Data):

S liu my tnh (Computer Data)

E-mail Truyn hnh nh thi gian thc (Real time image transfer)

a phng tin (Multimedia)

Tnh ton di ng (Computing)

Dch v vin thng (Telecommunication)

Di ng (Mobility)

Hi ngh truyn hnh (Video conferencing)

in thoi hnh (Video Telephony)

Cc dch v s liu bng rng (Wide band data services)

Dich v ni dung m thanh hnh nh (Audio - video content)

Hnh nh theo yu cu (Video on demand)

Cc dch vtng tc hnh nh (Interactive video services)

Bo in t (Electronic newspaper)

Mua bn t xa (Teleshopping)

Cc dch v internet gi tr gia tng (Value added internet

services Dch vpht thanh v truyn hnh (TV& Radio contributions)


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Nhng l do trn thc y cc t chc nghin cu pht trin h thng thng tin

di ng trn th gii tin hnh nghin cu v p dng trong thc t chun mi cho

h thng thng tin di ng: Thng tin di ng 2,5G v 3G

1.2 Cc t chc chun ho 2.5 G v 3G trn th gii

1.2.1 Gii thiu chung vcc tchc chun ho.

Trong mi lnh vc, mun p dng bt ccng nghno trn phm vi ton th

gii u phi xy dng mt btiu chun cho cng ngh bt buc cc nh cung

cp dch v, nh sn xut thit bhay cc nh khai thc phi tun thnghim ngt b

tiu chun ca cng ngh. Vic xy dng btiu chun cho mt cng nghthng

do t chc hay c quan c thm quyn nghin cu a ra d tho xut v nghin

cu nh gi. Lnh vc thng tin di ng cng khng nm ngoi nguyn tc chung

ny.

Mt vn cn quan tm trong lnh vc di ng l trn th gii hin nay ang

tn ti nhiu cng nghdi ng khc nhau ang cng tn ti pht trin v cnh tranh

nhau chim lnh th phn. Nhu cu thng nht cc cng ngh ny thnh mt h

thng thng tin di ng xut hin tlu, nhng gp phi nhiu kh khntrngi.

Trn thc t cc cng nghdi ng khc nhau vn song song tn ti v pht trin.

iu ny ng ngha vi vic trn th gii c nhiu t chc v c quan chun ho

khc nhau.

Hin nay trn th gii, tham gia vo vic chun ho cho h thng thng tin di

ng 2,5G v 3G c cc t chc sau:

ITU-T (T-Telecommunications) C thl nhm SSG (Special Study Group)

ITU-R (R- Radio): C thl nhm Working Group 8FWG8F.

3GPP: 3rdGlobal Partnership Project

3GPP2: 3rdGlobal Partnership Project 2

IETF: Internet Engineering Task Force

Cc t chc pht trin tiu chun khu vc (SDO-Standard Development

Oganization)

Ngoi ra cn c cc t chc khc trong c s tham gia ca cc nh khai thc

thch ng v lm hi ho sn phm trn c scc tiu chun chung. Cc nh khai

thc tham gia nhm xy dng v pht trin h thng thng tin di ng mt cch hp l,

ph hp vi thc tkhai thc. Cc t chc l:

OHGOperators Harmonisation Group

3G.IP: c thl Working Group 8G- WG8G


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MWIF-Mobile Wireless Internet Forum

Cc t chc trn tuy hot ng theo hng khc nhau, da trn nn tng cc cng

nghkhc nhau nhng c cu trc v nguyn tc hot ng tng t nhau. Tt ccc

t chc ny u hng ti mc tiu chung l xy dng mng thng tin di ng 3G.

ng thi cc t chc ny u c mi quan h hp tc gii quyt cc vn kt ni

lin mng v chuyn vng ton cu. Hai t chc OHG v MWIF a ra cc chun

pht trin khnng roaming v ghp ni gia cc mng li 2G: GSM-MAP v ANS41.

Mng li ANSI-41 c s dng bi cc h thng giao din v tuyn AMPS, IS-136

v IS-95. Mng li GSM-MAP c s dng bi cc h thng giao din v tuyn

GSM. C 2 mng li ny u spht trin ln 3G v lun c lin kt hot ng vi

nhau. S xut hin ca 3 t chc OHG , 3G.IP v MWIP cho thy n lc xy dng

mt mng li chung IP mc d iu ch trthnh hin thc khi h thng 3,5G v4G c xy dng.

Cng vic chun ho v xy dng tiu chun cho ANSI-41 c thc hin bi

U ban TR.45.2 ca TIA v qu trnh pht trin mng ny ln 3G ang c thc

hin trong cc nhm xy dng tiu chun k thut ca 3GPP2. Mng li da trn

ANSI-41 sc s dng bi cc mng truy nhp v tuyn da trn cdma2000. Cng

vic xy dng tiu chun GSM ang c tin hnh bi cc u ban SMG ca ETSI v

c lm cho ph hp vi yu cu ca M trong T1P1.5. Mi quan hny vn gi

nguyn i vi c vic chun ho 3G. Pht trin GSM ln 3G c thc hin bi

3GPP v c lm hi ho vi cc yu cu ca M trong T1P1. Mng li da trn

GSM-MAP sc s dng bi mng truy nhp v tuyn da trn UTRA.

Nh vy 2 t chc chu trch nhim chnh trong vic xy dng tiu chun cho

h thng thng tin di ng 3G l 3GPP v 3GPP2. Hai t chc ny c nhim vhnh

thnhv pht trin cc k thut cc lnh vc ring nhm thomn cc tiu chun k

thut ca h thng thng tin di ng 3G thng nht. Phn tip theo s cp ti 2 t

chc ny.

1.2.23GPP

Nm 1998, cc c quan pht trin tiu chun SDO khu vc ng thnh lp

mt t chc chu trch nhim tiu chun ho UMTS, c t tn l 3GPP ( 3rd

Generation Partnership Project). Cc thnh vin sng lp nn 3GPP bao gm :

ETSI-European Telecommunication Standard Institute- ca Chu u

ARIB-Association of Radio Industry Board- ca Nht BnTTA- Telecommunication Technology Association- ca Hn Quc


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T1 ca Bc M

TTC- Telecommunication Technology Committee- ca Nht Bn

CWTS- China Wireless Telecommunication Standard group - ca Trung Quc.

Ngoi ra cn c cc i tc vt vn thtrng l:3G.IP ca M

GSA ca Anh

GSM Association ca Ireland

IPv6 Forum ca Anh

UMTS Forum ca M

3G American ca M

3GPP cn c mt squan st vin l cc t chc pht trin tiu chun khu vc c tim nng tr thnh thnh vinchnh thc trong tng lai. Cc quan st vin

hin ti l:

TIATelecommunications Industries Association -ca M

TSACC-Telecommunications Standards AdvisoryCouncil of Canada- ca Canada

ACIF-Australian Communication Industry Forum - ca c

Cc thnh vin ca 3GPP thng nht rng, cng ngh truy nhp v tuyn l

hon ton mi v da trn WCDMA, cc thnh phn ca mng sc pht trin trnnn tng ca cc mng thng tin di ng th h2 c vi nguyn tc tn dng cao

nht c th. V mng li da trn m hnh GSM chng tc hiu qu trong s

dng thc t, cc u cui 3G cng s mang mt card tho lp c mang thng tin

lin quan n thu bao v cc chc nng c th ca nh cung cp dch v theo cch

ging nh GSM s dng SIM.

3GPP c chia thnh cc nhm tiu chun k thut (TSG Technical

Specification Group) chu trch nhim v tng lnh vc nht nh nh sau:TSG-SA: v dch vv kin trc

TSG-CN: vtiu chun ho mng li

TSG-T: v thit bu cui

TSG-GERAN: v mng truy nhp cho GSM v 2,5G

TSG-RAN: v mng truy nhp cho 3G

Cc nhm k thut trn c qun l bi mt nhm phi hp hot ng dn PCG

(Project Co-ordination Group). Cu trc chc nng c trnh by trong hnh 1-2


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CU TRC BN TRONG 3gpp

Nhm phi hp d n

TSGMng truy

nhp v tuyn

TSGMng li

TSGCc thit b

u cui

TSGCc kha cnhh thng v

dch v

TSGMng truy

nhp v tuynGSM/EDGE

Cc c tnh k thut

Hnh 1- 2 Cu trc chc nng ca PCG v TSG trong 3GPP

Bng 1- 1 Cc tham s c bn ca UTRA FDD v TDD, ARIB WCDMA FDD v TDD

ETSI UTRA(Chu u) ARIB WCDMA [ Nhat ban ]

FDD TDD FDD TDD

Phng php a

truy nhpWCDMA TD-CDMA WCDMA TD-CDMA

Tc chip Mcps 3,84 3,843,84

(1,024/7,68/15,36)

3,84

(1,024/7,68/15,36)

Khong cch sngmang

5MHz 5MHz 5(1,25/10/20)MHz 5 (1,25/10/20)MHz

di khung 10ms 10ms 10ms 10ms

S ln iu khin

cng sut trong

mt khe thi gian

15 15 15 15

Khong thi gian

mt khe thi gianKhng tn ti 625s Khng tn ti 625s

iu ch s liu

(DL/UL) QPSK QPSK QPSK/BPSK QPSK/BPSK

iu ch tri ph

(DL/UL*)QPSK QPSK QPSK/QPSK QPSK/QPSK

H s tri ph 4-512 1,2,4,8,16 2-512 2-512

Dng xunghm cos nng

r= 0,22

hm cos

nng r= 0,22

hm cos nng

r= 0,22

hm cos nng

r= 0,22

*DL/UL - ng xung/ ng ln

Cc tiu chun dnh cho 3G m 3GPP xy dng c pht trin da trn giao

din v tuyn GSM-MAP v UTRA WCDMA. Khi nim UTRA bao gm ccc ch

hot ng FDD v TDD h trmt cch hiu qucc nhu cu dch v UMTS


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khc nhau v cc dch v i xng v khng i xng. Trong qu trnh nh gi

UTRA trong ETSI SMG2, vic kho st c tp trung vo chFDD. Khi nim

TD-CDMA c chp thun dng cho ch TDD cha ng hi ho cc tham s

gia FDD v TDD. Cc tham s ca UTRA c trnh by trong bng 1-1.

xut WCDMA ca ARIB bao gm c 2 ch hot ng, FDD v TDD.

Ch FDD ca xut ny kh ging vi ch FDD ca ETSI UTRA. Tuy nhin,

chTDD c thit k gn ging vi chFDD, nhng chp nhn mt sc

trng ring bit nh cng nghiu khin cng sut vng mv phn tp pht. Sau

quyt nh vo thng 1 nm 1998 ca ETSI SMG, h thng truy nhp c i tn l

TD-CDMA thay cho tn WCDMA trc y, bi v mt snt c trng ca TDMA

c kt hp vo tn dng nhng u im vcng ngh ca TD-CDMA.

1.2.3 3GPP2

3GPP2 c thnh lp vo cui nm 1998, vi 5 thnh vin chnh thc l t

chc pht trin sau tiu chun sau:

ARIB-Association of Radio Industry Board- ca Nht Bn

CWTS- China Wireless Telecommunication Standard- ca Trung Quc

TIA- Telecommunication Industry AssociationCa Bc M

TTA- Telecommunication Technology Association- Ca Hn Quc

TTC- Telecommunication Technology Council- ca Nht Bn

Ngoi ra t chc ny cn c mt scc i tc t vn thtrng nh:

CDG- The CDMA Development Group

MWIF-Mobile Wireless Internet Forum

IPv6 Forum

C th nhn thy rng thnh phn tham gia 2 c quan chun ho 3GPP v

3GPP2 vc bn l ging nhau, chkhc im 3GPP c s tham gia ca ETSI. V

vy ddng suy ra vc bn, cu trc t chc, nguyn l hot ng ca 2 c quan nygn ging nhau. Skhc nhau ch yu ca 2 c quan ny nm con ng pht

trin ln h thng 3G.

V cu trc chc nng, trc ht 3GPP2 c mt ban ch o d n- PSC

(Project Steering Commitee). PSC s qun l ton bcng tc tiu chun ho theo cc

nhm k thutTSG. 3GPP2 hin nay c 4 nhm TSG, bao gm:

TSG-A: nghin cu vcc h thng giao din mng truy nhp

TSG-C: v CDMA2000

TSG-S: vcc kha cnh dch vv h thng


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TSG-X: v hot ng lin kt cc h thng.

Ta c th thy cng vic chnh ca cng vic chnh ca 3GPP2 chnh l xy dng

tiu chun ho CDMA2000. CDMA2000 cung cp mt con ng pht trin ln 3G

bng cch s dng cc tiu chun TIA/EIA-95B hin c, bao gm:

TIA/EIA-95B: cc tiu chun trm di ng v giao din v tuyn.

IS-707: tiu chun cho cc dch v s liu(dng gi, khng ng bv fax)

IS-127: tiu chun cho bm ho thoi tc 8,5Kbps EVRC

IS-733: tiu chun cho bm ho thoi tc 13kbps

IS-637: tiu chun cho dch v nhn tin ngn (SMS)

IS-638: qun l cc tham sv vic kch hot qua khng gian (h trvic cu hnh

v kch hot dch v ca cc trm di ng qua giao din v tuyn).

IS-97 v IS-98: cc tiu chun dnh cho cc hot ng mc ti thiu

Cu trc knh TIA/EIA-95 c bn.

Cc tiu chun m rng cho cc cu trc knh TIA/EIA-95B c bn b tr, lp

ghp knh v bo hiu h trcc knh pht qung b (Knh hoa tiu , knh tm

gi, knh ng b)

IS-634A: khng chu s thay i quan trng no khi dng cho CDMA2000; cu

trc phn lp ca CDMA2000 dn dn tch hp vi cu trc thnh phn ca IS-

634A.

TIA/EIA-41D: khng cn thay i nhiu khi s dng cho CDMA2000; cu trc

phn tng ca CDMA2000 to ra khnng d tch hp vi cc dch vgi tr gia

tng.

Cc tiu chun ca 3GPP2 c pht trin theo cc pha sau y:

Pha 0: ton bcc tiu chun c cc SDO hon thin

Pha 1: ch yu l cc chtiu k thut cho Release 1 k tha ton b phn 2G

IS-95A v IS-95B. Hon thin vo nm 2000.

Pha 2: bt u t gia nm 2001 nhm h trkhnng IP Multimedia, phin bn

u tinhon thin trong nm 2002, cc phin bn sau trong nm 2003.

Pha 3: thm cc chc nng theo hng mng li IP. Hin nay giai on ny c

khi ng.

Ngoi ra, hin nay CDMA2000 1xEV ca 3GPP2 c ITU chnh thc chp

thun 3G.

1.2.4 Mi quan hgia 3GPP v 3GPP2 v ITU

3GPP v 3GPP2 hp tc ln u nhm gii quyt vn kt ni lin mng, chuyn

vng ton cu, tp trung vo 3 kha cnh chnh:


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Truy nhp v tuyn

Thit bu cui

Mng li

Hot ng hp tc ny ch yu thng qua OGH v cc nhm ad hoc c stham gia ca c2 bn 3GPP v 3GPP2. Hin nay, IETF l mt trong cc nhn t mi

cng vi 3GPP v gii quyt hng mng li chung ton IP. Mi y, sau khi

nghin cu HSDPA (3GPP) v 1xEV-DO (3GPP2), c hai t chc ny ang tip tc

n lc theo hng mng li IP chung qua cc cuc hp nm 2002.

ITU chu trch nhim phi hp s hot ng ca cc t chc tiu chun ho, c

thl 2 n v chu trch nhim trc tip:

ITU-T SSG- Special Study GroupITU-R WP8F- Working Party 8F.

Trong , ITU-T SSG c 3 nhm lm vic vi 7 vn , gii quyt 90% cng tc

chun ho v mng (Network Aspects), tp trung vo cc mng:

Giao din NNI

Qun l di ng

Yu cu giao thc

Pht trin giao thc

Ngc li, ITU-R WP8F c trch nhim gii quyt 90% cng tc chun ho v giao

din v tuyn tp trung vo cc nhim v :

Cc chtiu ton din ca mt h thng IMT-2000

Tip tc chun ho ton cu bng cch kt hp vi cc c quan tiu chun SDO v

cc Project (3GPP v 3GPP2)

Xc nh mc tiu sau IMT-2000:3,5G v 4G

Tp trung vo phn mng mt t (tng tc d liu, mng theo hng IP)Phi hp vi ITU-R WP8P v v tinh, vi ITU-T v ITU-D v cc vn lin

quan.

Vai tr ca tng thnh phn trong mi quan h gia cc t chc ny c th rt

gn nh sau:

3GPP v 3GPP2: m bo pht trin cng nghv cc chtiu giao din v tuyn

cho ton cu;

Cc t chc tiu chun khu vc SDO: lm thch ng cc tiu chun chung cho

tng khu vc. Kt qu l s xut hin ca cc tiu chun IMT-2000 trn c sch

tiu k thut ca 3GPP v 3GPP2.


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ITU-T v ITU-R: m bo khnng tng thch v roaming ton cu vi cc ch

tiu. C thr vic phn cng v trch nhim qua ITU-R.M 1457 v ITU-T Q.REF.

Hin nay, c3GPP, 3GPP2, ITU v IETF tip tc phi hp cht ch gii quyt

mng li chung IP theo cc cng ngh3,5G v 4G.

1.3 Tnh hnh chun ho 2,5G v 3G

1.3.1 Mu

Hin nay, cc btiu chun cng ngh 2,5G vc bn c hon thin, c th

nh sau:

3GPP hon thin chtiu k thut GPRS, t cc t chc chun ho khu vc

c b tiu chun k thut GPRS. Mt scc nc thuc nhm cng nghny

nh Chu u, Hng Kng, Nht Bn bin son hoc chp nhn nguyn vn

chun cho ph hp vi iu kin cng ngh ca mnh.

3GPP2 hon thin cc ch tiu k thut CDMA2000 1xEV-DO. Cc t chc

chun ha khu vc ca cc nc c cng ngh IS-95A hoc IS-95B hu ht c

tiu chun p dng nguyn vn cng ngh 2,5G.

Vi cng ngh3G, tnh hnh chun ho phc tp hn vi 3 mng chnh sau:

Cng ngh truy nhp v tuyn

Mng li

Giao din vi cc h thng khc.

1.3.2 Chun ho cng nghtruy nhp v tuyn

Trn th gii hin ang tn ti nhiu cng nghthng tin di ng 2G khc nhau

vi s vn u t tng i ln. Vic xy dng mt h thng thng tin di ng tin

tin hn lun i hi phi ch ti vn li nhun kinh t, c ngha l cc h thng

thng tin di ng mi phi tng thch ngc vi cc h thng 2G hin c, tn

dng su t vc sh tng ca cc h thng c. Nh vy, mc tiu pht trin n

mt tiu chun duy nht cho IMT-2000 l khng tht c. Trn thc t, ITU

chp nhn s tn ti song song ca 5 hcng nghkhc nhau:

IMT-MC (IMT-Multi Carrier): CDMA2000

IMT-DS (IMT- Direct Sequence): WCDMAFDD

IMT-TC: WCDMA-TDD

IMT-SC: TDMA mt sng mang, cn gi l UWC-136 v EDGE

IMT-FT: DECT


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14

Cc hcng nghny c nn tng cng nghkhc nhau v c cc c quan t

chc tiu chun ho khc nhau thc hin cc vic xy dng chun c trnh by

trong hnh 1-3

UTRA FDD

DIRECTSEQUENCE

UTRA TDDcac toc o chip

cao va thap

3GPP UWCC 3GPP2 ETSI

TIMECODE

SINGLECARRIER

MULTI-CARRIER

FREQUENCYTIME

UWC 136 DECTcdma 2000

Hnh 1- 3 Cc h cng ngh c ITU-R chp nhn

Trong nm 2002, ITU-R chp thun 7 loi cng ngh c th, m thc cht

thuc 5 hcng nghtrn:

CDMA a sng mang (cdma2000)

CDMA1x-EV

CDMA TDD (UTRA)

CDMA TDD (TD-SCDMA)

W-CDMA (UTRA - FDD)

UWC-136 (FDD)

FDMA/TDMA: DECT.

Cc cng nghtrn bao gm:

-Hai tiu chun TDMA: SC-TDMA (UWC-136) v MC-TDMA (DECT)

-Ba tiu chun CDMA : MC-CDMA (cdma2000 ), DS-CDMA (WCDMA) v

CDMA-TDD (bao gm TD-SCDMA v UTRA-TDD).

Ta xt cc tiu chun TDD vi cc c im sau:-TDD c th s dng cc ngun ti nguyn tn skhc nhau v khng cn cp tn s.

-TDD ph hp vi truyn dn bt i xng v tc gia ng ln v ng xung,

c bit vi cc dch v d liu dng IP

-TDD hot ng cng tn scho ng ln v ng xung, ph hp cho vic s

dng cc k thut mi nh anten thng minh

-Chi ph thit b h thng TDD thp hn, c th thp hn t20 n 50% so vi cc

h thng FDD.

Tuy nhin, hn chchnh ca h thng TDD l tc di chuyn v din tch ph

sng. Cc h thng TDD chthch hp vi vic trin khai cho cc dch va phng


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15

tin trong cc khu vc mt cao v c yu cu cao vdung lng thoi, d liu v

cc dch va phng tin trong cc khu vc tp trung thu bao ln. TD-SCDMA l

cng ngh do Trung Quc xut, cn UTRA-TDD c xem l phn b sung cho

UTRA-FDD ti nhng vng c dung lng rt cao. Hn na cc cng nghny cha

c sn phm thng mi. Trn thc t chc 2 tiu chun quan trng nht c sn

phm thng mi v c kh nng c trin khai rng ri trn ton th gii l

WCDMA (FDD) v cdma2000. WCDMA c pht trin trn c stng thch vi

giao thc ca mng li GSM (GSM MAP), mt h thng chim ti 65% thtrng th

gii. Cn cdma2000 nhm tng thch vi mng li IS-41, hin chim 15% thtrng.

Qu trnh pht trin ln 3G cng s tp trung vo 2 hng chnh ny, c thc tm

tt trong hnh 1-4.

NMT(900)

TACSGSM (900)

AMPS cdma2000Mx

WCDMA

SMR

GSM (1800)

GSM (1900)

IS-136TDMA (800)

IS-95CDMA (800)

IS-136(1900)

IS-95(J-STD-008)

(1900)

GPRS

iDEN (800)

GPRS

EDGE

cdma20001x

1G 2G 2.5G 3G

Hnh 1- 4 Qu trnhpht trin ln 3G ca 2 nhnh cng ngh chnh

1.3.3 Phn tch hai nhnh cng nghchnh tin ln 3G

1.3.3.1 Hng pht trin ln 3G sdng cng ngh WCDMA

WCDMA l mt tiu chun thng tin di ng 3G ca IMT-2000 c pht

trin ch yu Chu u vi mc ch cho php cc mng cung cp khnng chuyn

vng ton cu v h trnhiu dch v thoi, dch va phng tin. Cc mng

WCDMA c xy dng da trn c smng GSM, tn dng c sh tng sn c


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16

ca cc nh khai thc mng GSM. Qu trnh pht trin tGSM ln CDMA qua cc

giai on trung gian, c thc tm tt trong s sau y:

GSM GPRS EDGE WCDMA

1999 2000 2002

Hnh 1- 5 Qu trnh pht trin ln 3G theo nhnh s dng cng ngh WCDMA

1.3.3.1.1 GPRS

GPRS l mt h thng v tuyn thuc giai on trung gian, nhng vn l h

thng 3G nu xt v mng li. GPRS cung cp cc kt ni s liu chuyn mch gi

vi tc truyn ln ti 171,2Kbps (tc s liu nh) v h trgiao thc Internet

TCP/IP v X25, nhvy tng cng ng kcc dch v s liu ca GSM.

Cng vic tch hp GPRS vo mng GSM ang tn ti l mt qu trnh n

gin. Mt phn cc khe trn giao din v tuyn dnh cho GPRS, cho php ghp knh

s liu gi c lp lch trnh trc i vi mt s trm di ng. Phn h trm gc ch

cn nng cp mt phn nhlin quan n khi iu khin gi (PCU- Packet Control

Unit) cung cp khnng nh tuyn gi gia cc u cui di ng cc nt cng

(gateway). Mt nng cp nh v phn mm cng cn thit h trcc h thng m

ho knh khc nhau.

Mng li GSM c to thnh tcc kt ni chuyn mch knh c mrng

bng cch thm vo cc nt chuyn mch s liu v gateway mi, c gi l GGSN

(Gateway GPRS Support Node) v SGSN (Serving GPRS Support Node). GPRS l

mt gii php c chun ho hon ton vi cc giao din m rng v c th

chuyn thng ln 3G v cu trc mng li.

1.3.3.1.2 EDGE

EDGE (Enhanced Data rates for Global Evolution) l mt k thut truyn dn

3G c chp nhn v c th trin khai trong ph tn hin c ca cc nh khai thc

TDMA v GSM. EDGE ti s dng bng tn sng mang v cu trc khe thi gian ca

GSM, v c thit k nhm tng tc s liu ca ngi s dng trong mng GPRS

hoc HSCSD bng cch s dng cc h thng cao cp v cng nghtin tin khc. V

vy, c sh tng v thit bu cui hon ton ph hp vi EDGE hon ton tng

thch vi GSM v GRPS.

1.3.3.1.3 WCDMA hay UMTS/FDD

WCDMA (Wideband Code Division Multiple Access) l mt cng ngh truy

nhp v tuyn c pht trin mnh Chu u. H thng ny hot ng ch


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17

FDD v da trn k thut tri ph chui trc tip (DSSS- Direct Sequence Spectrum)

s dng tc chip 3,84Mcps bn trong bng tn 5MHz. Bng tn rng hn v tc

tri ph cao lm tng li x l v mt gii php thu a ng tt hn, l c

im quyt nh chun b cho IMT-2000.

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 chgi

hot ng mc hiu qu cao nht. Hn na WCDMA c th h trcc 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.

WCDMA l cng ngh truyn dn v tuyn mi vi mng truy nhp v tuynmi, c gi l UTRAN, bao gm cc phn t mng mi nh RNC (Radio Network

Controller) v NodeB (tn gi trm gc mi trong UMTS)

Tuy nhin mng li GPRS/EDGE c thc s dng li v cc thit bu cui

hot ng nhiu chc khnng h trGSM/GPRS/EDGE v c WCDMA.

1.3.3.2 Hng pht trin ln 3G sdng cng ngh cdma2000.

H thng cdma2000 gm mt snhnh hoc giai on pht trin khc nhau h

trcc dch v phc tng cng. Ni chung cdma2000 l mt cch tip cn a

sng mang cho cc sng c rng n ln 1,25MHz hot ng chFDD. Nhng

cng vic chun ho tp trung vo gii php mt sng mang n 1,25MHz (1x) vi

tc chip gn ging IS-95. cdma2000 c pht trin t cc mng IS-95 ca h

thng thng tin di ng 2G, c thm tqu trnh pht trin trong hnh v sau:

IS-95A IS-95B Cdma2000 1x Cdma2000 Mx

1999 2000 2002

Hnh 1- 6Qu trnh pht trin ln 3G theo nhnh cdma2000.

1.3.3.2.1 IS-95B.

IS-95B, hay cdmaOne c coi l cng ngh thng tin di ng 2,5G thuc

nhnh pht trin cdma2000, l mt tiu chun kh linh hot cho php cung cp dch

v s liu tc ln n 115Kbps

1.3.3.2.2 cdma2000 1xRTT

Giai on u ca cdma2000 c gi l 1xRTT hay ch l 1xEV-DO, cthit k nhm ci thin dung lng thoi cua IS-95B v h trkhnng truyn s


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liu tc nh ln ti 307,2Kbps. Tuy nhin, cc thit bu cui thng mi ca

1x mi chcho php tc s liu nh ln ti 153,6kbps. Nhng ci thin so vi IS-

95 t c nha vo mt scng nghtin tin nh iu chQPSK v m ho

Turbo cho cc dch v s liu cng vi khnng iu khin cng sut nhanh ng

xung v phn tp pht.

1.3.3.2.3 cdma2000 1xEV-DO

1xEV-DO, c hnh thnh t cng ngh HDR (High Data Rate) ca

Qualcomm, c chp nhn vi tn ny nh l mt tiu chun thng tin di ng 3G

vo thng 8 nm 2001 v bo hiu cho spht trin ca gii php n sng mang i

vi truyn s liu gi ring bit.

Nguyn l c bn ca h thng ny l chia cc dch v thoi v dch v s liu

tc cao vo cc sng mang khc nhau. 1xEV-DO c thc xem nh mt mng

s liu xp chng, yu cu mt sng mang ring. tin hnh cc cuc gi va c

thoi, va c s liu trn cu trc xp chng ny cn c cc thit b hot ng 2

ch1x v 1xEV-DO.

1. 3.3.2.4 cdma2000 1xEV-DV

Trong cng ngh 1xEV-DO c s d tha v ti nguyn do s phn bit c

nh ti nguyn dnh cho thoi v ti nguyn dnh cho s liu. Do , CDG, nhm

pht trin CDMA, khi u pha th ba ca cdma2000 a cc dch v thoi v s liu

quay v chdng mt sng mang 1,25MHz v tip tc duy tr s tng thch ngc

vi 1xRTT. Tc s liu cc i ca ngi s dng ln ti 3,1Mbps tng ng vi

kch thc gi d liu 3940 bit trong khong thi gian 1,25ms.

Mc d k thut truyn dn c bn c nh hnh, vn c nhiu xut cng

nghcho cc thnh phn cha c quyt nh k ctiu chun cho ng xung ca

1xEV-DV.

1.3.3.2.5 cdma2000 3x(MC- CDMA )

cdma2000 3x, hay 3xRTT, cp n s la chn a sng mang ban u

trong cu hnh v tuyn cdma2000 v c gi l MC-CDMA (Multi carrier) thuc

IMT-MC trong IMT-2000. Cng nghny lin quan n vic s dng 3 sng mang 1x

tng tc s liu v c thit k cho di tn 5MHz (gm 3 knh 1,25Mhz). S

la chn a sng mang ny chp dng c trong truyn dn ng xung. ng

ln tri ph trc tip, ging nh WCDMA vi tc chip hi thp hn mt cht

3,6864Mcps (3 ln 1,2288Mcps).


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1.3.4 Tng kt

Nh vy, trn th gii hin ang tn ti cc cng nghkhc xy dng h

thng thng tin di ng 3G. Cc nc khi la chn cc cng ngh3G c thcn c

theo ITU-R M.1457 xc nh cc chtiu ch yu ca hcng ngh truy nhp v

tuyn v xy dng tiu chun trn c stp hp bin son hoc p dng nguyn vn

theo cc tiu chun ca SDO sao cho ph hp vi iu kin ca mnh.


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Chng 2- Tng quan cng ngh WCDMA trong h thng UMTS

20

Chng 2.TNG QUAN CNG NGH WCDMA

TRONG H THNG UMTS.

2.1 Nguyn l CDMA

2.1.1 Nguyn l tri ph CDMA

Cc h thng sc thit k tn dng dung lng mt cch ti a. Theo

nguyn l dung lng knh truyn ca Shannon c m ttrong (2.1), r rng dung

lng knh truyn c thc tng ln bng cch tng bng tn knh truyn.

C = B. log2(1+S/N) (2.1)

Trong B l bng thng (Hz), C l dung lng knh (bit/s), S l cng sut tnhiu v N l cng sut tp m.

V vy, i vi mt t s S/N c th (SNR), dung lng tng ln nu bng

thng s dng truyn tng. CDMA l cng ngh thc hin tri tn hiu gc thnh

tn hiu bng rng trc khi truyn i. CDMA thng c gi l K thut a truy

nhp tri ph (SSMA).T s rng bng tn truyn thc vi rng bng tn ca

thng tin cn truyn c gi l li xl (GP) hoc l h s tri ph.

GP = Bt / Bi hoc GP = B/R (2.2)

Trong Bt :l rng bng tn truyn thc t

Bi: rng bng tn ca tn hiu mang tin

B : l rng bng tn RF

R : l tc thng tin

Mi quan h gia t sS/N v t s Eb/I0, trong Ebl nng lng trn mt

bit, v I0l mt phnng lng tp m, th hin trong cng thc sau :

p

bb

GI

E

BI

RE

N

S 1

00

(2.3)

V th, vi mt yu cu Eb/I0 xc nh, li xl cng cao, th t sS/N yu

cu cng thp. Trong h thng CDMA u tin, IS-95, bng thng truyn dn l

1.25MHz. Trong h thng WCDMA, bng thng truyn khong 5MHz.


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Trong CDMA, mi ngi s dng c gn mt chui m duy nht (m tri

ph) tri tn hiu thng tin thnh mt tn hiu bng rng trc khi truyn i. Bn

thu bit c chui m ca ngi s dng v gii m khi phc tn hiu gc.

2.1.2 K thut tri phv gii tri ph

Tri ph v gii tri ph l hot ng c bn nht trong cc h thng DS-

CDMA. D liu ngi s dng ng l chui bit c iu chBPSK c tc lR.

Hot ng tri ph chnh l nhn mi bit d liu ngi s dng vi mt chui n bit

m, c gi l cc chip.y, ta ly n=8th h s tri phl 8, ngha l thc hin

iu ch tri ph BPSK. Kt qu tc d liu l 8xR v c dng xut hin ngu

nhin (gi nhiu) nh lm tri ph. Vic tng tc d liu ln 8 ln p ng vic

mrng (vi h sl 8) ph ca tn hiu d liu ngi s dng c tri ra. Tn hiu

bng rng ny sc truyn qua cc knh v tuyn n u cui thu.

Hnh 2- 1 Qu trnh tri ph v gii tri ph

Trong qu trnh gii tri ph, cc chui chip/d liu ngi s dng tri phc

nhn tng bit vi cng cc chip m 8 c s dng trong qu trnh tri ph. Nh

trn hnh vtn hiu ngi s dng ban u c khi phc hon ton.2.1.3. K thut a truy nhp CDMA

Mt mng thng tin di ng l mt h thng nhiu ngi s dng, trong mt

slng ln ngi s dng chia s ngun ti nguyn vt l chung truyn v nhn

thng tin. Dung lng a truy nhp l mt trong cc yu tc bn ca h thng. K

thut tri phtn hiu cn truyn em li khnng thc hin a truy nhp cho cc h

thng CDMA. Trong lch sthng tin di ng tn ti cc cng ngha truy nhp

khc nhau: TDMA, FDMA v CDMA. Skhc nhau gia chng c ch ra trong

hnh 2-2.


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22

Hnh 2- 2 Cc cng ngh a truy nhp

Trong h thng a truy nhp theo tn sFDMA, cc tn hiu cho cc ngi s

dng khc nhau c truyn trong cc knh khc nhau vi cc tn siu chkhc

nhau. Trong 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. Vi cccng nghkhc nhau, sngi s dng ln nht c th chia sng thi cc knh vt

l l cnh. 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. 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 cnh, nn dung lng ca h thng CDMA c gi l dung lng mm.

Hnh 2-3 ch ra mt v dlm thno 3 ngi s dng c th truy nhp ngthi trong mt h thng CDMA.

Hnh 2- 3Nguyn l ca a truy nhp tri ph

Ti bn thu, ngi s dng 2 s gii tri phtn hiu thng tin ca n trli tn

hiu bng hp, chkhng phi tn hiu ca bt cngi no khc. Bi v s tng

quan cho gia m ca ngi s dng mong mun v cc m ca ngi s dng khcl rt nh : vic tch sng kt hp s ch cp nng lng cho tn hiu mong mun v

mt phn nhcho tn hiu ca ngi s dng khc v bng tn thng tin.


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23

li x l v c im bng rng ca qu trnh x l em li nhiu li ch

cho cc h thng CDMA, nh hiu sut phcao v dung lng mm. Tuy nhin, tt

c nhng li ch yu cu vic s dng k thut iu khin cng sut nghim ngt

v chuyn giao mm, trnh cho tn hiu ca ngi s dng ny che thng tin ca

ngi s dng khc.

2.2. Mt sc trng ca lp vt l trong h thng WCDMA.

2.2.1. Cc m tri ph.

Trong h thng tri ph chui trc tip DSSS, cc bit d liu c m ho vi

mt chui bit gi ngu nhin (PN). Mng v tuyn UMTS mng s dng mt tc

chip cnh l 3.84Mcps em li mt bng thng sng mang xp x 5MHz. D liu

c gi qua giao din v tuyn WCDMA c m ho 2 ln trc khi c iu ch

v truyn i. Qu trnh ny c m ttrong hnh v sau:

Hnh 2- 4 Qu trnh tri ph v trn

Nh vy trong qu trnh trn c hai loi m c s dng l m trn v m nh

knh.

M nh knh: l cc m h s tri ph bin i trc giao OVSF gitnh trc

giao gia cc knh c cc tc v h s tri phkhc nhau. Cc m la chn c

xc nh bi h s tri ph. Cn phi ch rng: Mt m c thc s dng trong

cell khi v chkhi khng c m no khc trn ng dn t mt m c thn gc

ca cy m hoc l trn mt cy con pha di m c s dng trong cng mt

cell. C thni tt ccc m c chn la s dng hon ton theo quy lut trc giao.

M trn. M trn c s dng trn ng xung l tp hp chui m Gold.

Cc iu kin ban u da vo sm trn n. Chc nng ca n dng phn bit cc

trm gc khc nhau. Thng qua m phng, n c xc nh l t s gia t tng quan

v tng quan cho khi thay i s chip b ct bt do thay i t s S/N. Kt quc

ch ra trong bng 2-1.


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Bng 2- 1 Quan h gia S/N v s chip b ct bt

C hai loi m trn trn ng ln , chng dng duy tr s phn bit gia cc

my di ng khc nhau. C hai loi u l m phc. M th nht l m ho Kasami rt

rng. Loi thhai l m trn di ng ln thng c s dng trong cell khng

pht hin thy nhiu ngi s dngtrong mt trm gc. l chui m Gold c chiu

di l 241-1.

2.2.2.Phng thc song cng.

Hai phng thc song cng c s dng trong kin trc WCDMA: Song cngphn chia theo thi gian (TDD) v song cng phn chia theo tn s (FDD). Phng

php FDD cn hai bng tn cho ng ln v ng xung. Phng thc TDD ch

cn mt bng tn. Thng thng ph tn sc bn cho cc nh khai thc theo cc

di c th bng 2x10MHz, hoc 2x15MHz cho mi biu khin. Mc d c mt s

c im khc nhau nhng c hai phng thc u c tng hiu sut gn ging nhau.

ChTDD khng cho php gia my di ng v trm gc c tr truyn ln, bi v

sgy ra ng gia cc khe thi gian thu v pht. V vy m chIDD ph hp

vi cc mi trng c tr truyn thp, cho nn ch TDD vn hnh cc pico cell.

Mt u im ca TDD l tc d liu ng ln v ng xung c th rt khc

nhau, v vy m ph hp cho cc ng dng c c tnh bt i xng gia ng ln v

ng xung , chng hn nhWeb browsing. Trong qu trnh hoch nh mng, cc

u im v nhc im ca hai phng php ny c th b tr. n ny ch tp

trung nghin cu ch FDD.

Hnh di y ch ra sphn b ph tn s ca h thng UMTS Chu u.

1900 19801920 2010 2025 2110 2170 MHz

nbang

nbang

Song bang

ng len ng xuong

Hnh 2- 5Phn b ph tn cho UMTS chu u.


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2.2.3. Dung lng mng.

Kt qu ca vic s dng cng ngh a truy nhp tri ph CDMA l dung

lng ca cc h thng UMTS khng b gii hn cng, c ngha l mt ngi s dng

c th b sung m khng gy ra nghn bi s lng phn cng hn ch. H thng

GSM c s lng cc lin kt v cc knh cnh chcho php mt lu lng ln

nht c tnhton v hoch nh trc nhs dng cc m hnh thng k. Trong

h thng UMTS bt c ngi s dng mi no sgy ra mt lng nhiu b sung cho

nhng ngi s dng ang c mt trong h thng, nh hng n ti ca h thng.

Nu c sm th mc tng nhiu do tng ti l ccu gii hn dung lng chnh

trong mng. Vic cc cell b co hp li do ti cao v vic tng dung lng ca cc cell

m cc cell ln cn n c mc nhiu thp l cc hiu ng th hin c im dung

lng xc nh nhiu trong cc mng CDMA. Chnh v th m trong cc mngCDMA c c im dung lng mm. c bit, khi quan tm n chuyn giao mm

th cc ccu ny lm cho vic hoch nh mng trnn phc tp.

2.2. 4. Phn tp a ng- B thu RAKE.

Truyn sng v tuyn trong knh di ng mt t c c trng bi cc s phn

x, ssuy hao khc nhau ca nng lng tn hiu. Cc hin tng ny gy ra do cc

vt cn tnhin nhto nh, cc quidn n hiu ng truyn sng a ng.

Hnh 2- 6Truyn sng a ng

Hiu ng a ng thng gy ra nhiu kh khn cho cc h thng truyn dn

v tuyn. Mt trong nhng u im ca cc h thng DSSS l tn hiu thu qua cc

nhnh a ng vi tr truyn khc nhau v cng tn hiu khc nhau li c th ci

thin hiu sut ca h thng. kt hp cc thnh phn tcc nhnh a ng mt

cch nht qun, cn thit phi tch ng cc thnh phn . Trong cc h thng

WCDMA, b thu RAKE c s dng thc hin chc nng ny. Mt b thu

RAKE bao gm nhiu b thu c gi l finger. B thu RAKE s dng cc bcnbng v cc b xoay pha chia nng lng ca cc thnh phn tn hiu khc nhau c


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pha v bin thay i theo knh trong schm sao. Sau khi iu chnh tr thi

gian v cng tn hiu, cc thnh phn khc nhau c kt hp thnh mt tn

hiu vi cht lng cao hn. Qu trnh ny c gi l qu trnh kt hp theo t s ln

nht (MRC), v chc cc tn hiu vi tr tng i cao hn rng thi gian ca

mt chip mi c kt hp. Qu trnh kt hp theo t s ln nht s dng tc chip

l 3.84Mcps tng ng vi 0.26s hoc l chnh lch vdi ng dn l 78m.

Phng php ny gim ng k hiu ng phadinh bi v khi cc knh c c im

khc nhau c kt hp th nh hng ca phadinh nhanh c tnh bnh qun. li

thu c t vic kt hp nht qun cc thnh phn a ng tng t vi li ca

chuyn giao mm c c bng cch kt hp hai hay nhiu tn hiu trong qu trnh

chuyn giao.

2.2.5. Cc knh giao din vtuyn UTRA FDD.

Giao din v tuyn UTRA FDD c cc knh logic, chng c nh x vo cc

knh chuyn vn, cc knh chuyn vn li nh xvo knh vt l. Hnh v sau ch ra

scc knh v snh x ca chng vo cc knh khc.

Hnh 2- 7 S nh x gia cc knh khc nhau.

Ph lc B s ch ra chi tit cc knh UTRA khc nhau.

2.2.6. Trng thi cell.

Nhn di gc UTRA, UE c thchri hoc chkt ni. Trong

chri, my di ng c bt v bt c knh iu khin ca mt cell no ,

nhng phn UTRAN ca mng khng c thng tin no v UE. UE chc thc

nh a ch bi mt thng ip (chng hn nhthng bo tm gi) c pht qung

b n tt c ngi s dng trong mt cell. Trng thi chri cng c gi l


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trng thi ngh trong cell. UE c th chuyn sang chkt ni bng cch yu

cu thit lp mt kt ni RRC. Hnh v sau y chra cc trng thi v s chuyn tip

cc trng thi cho mt UE bao gm ccc ch GSM/GPRS.

Cell DCH

Cell FACH

Cell PCH

URA PCH

Che o ket noi GSM

Che o ket noi GPRS

Ngh

tr

ongce

ll

UTRAN

Ngh

tr

ongcel

l

GSM/GPRS

Che o ket noi UTRARRCChe oRoi

Hnh 2- 8 Cc ch ca UE v cc trng thi iu khin ti nguyn v tuyn

Nhn chung vic n nh cc knh khc nhau cho mt ngi s dng v vic

iu khin ti nguyn v tuyn c thc hin bi giao thc Qun l ti nguyn v

tuyn. Trong chkt ni ca UTRA, c 4 trng thi RRC m UE c th chuyni gia chng: Cell DCH, Cell FACH, Cell PCH v URA PCH.

Trong trng thi Cell DCH, UE c cp pht mt knh vt l ring trn ng ln v

ng xung.

Trong 3 trng thi khc UE khng c cp pht knh ring. Trong trng thi

Cell FACH, UE gim st mt knh ng xung v c cp pht mt knh FACH

trn ng ln. Trong trng thi ny, UE thc hin vic chn la li cell. Bng cch

gi thng ip cp nht cell, RNC bit c vtr ca UE mc cell.

Trong trng thi Cell PCH v URA PCH, UE chn la knh tm gi (PCH) v

s dng vic tip nhn khng lin tc (DRX) gim st knh PCH chn la

thng qua mt knh lin kt PICH. Trn ng ln khng c hot ng no lin quan

n trng thi ny. Skhc nhau gia 2 trng thi ny nh sau: Trong trng thi Cell

PCH vtr ca UE c nhn bit mc cell tu theo vic thc hin cp nht cell cui

cng. Trong trng thi URA PCH, vtr ca UE c nhn bit mc vng ng k

UTRAN (URA) tu theo vic thc hin cp nht URA cui cng trong trng thi CellFACH.


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2.2.7. Cu trc Cell.

Trong sut qu trnh thit k ca h thng UMTS cn phi ch nhiu hn n

sphn tp ca mi trng ngi s dng. Cc mi trng nng thn ngoi tri,

thngoi tri, hay th trong nh c h trbn cnh cc m hnh di ng khc

nhau gm ngi s dng tnh, ngi i bn ngi s dng trong mi trng xe c

ang chuyn ng vi vn tc rt cao. yu cu mt vng phsng rng khp v

kh nng roaming ton cu, UMTS pht trin cu trc lp cc min phn cp vi

kh nng phsng khc nhau. Lp cao nht bao gm cc v tinh bao phton btri

t; Lp thp hn hnh thnh nn mng truy nhp v tuyn mt t UTRAN. Mi lp

c xy dng tcc cell, cc lp cng thp cc vng a l bao ph bi cc cell cng

nh. V vy cc cell nhc xy dng h trmt ngi s dng cao hn. Cc

cell macro nghcho vng ph mt t rng kt hp vi cc micro cell tng dunglng cho cc vng mt dn scao. Cc cell pico c dng cho cc vng c

coi nhl cc im nng yu cu dung lng cao trong cc vng hp (v d nhsn

bay). Nhng iu ny tun theo 2 nguyn l thit k bit trong vic trin khai cc

mng tbo: cc cell nh hn c thc s dng tng dung lng trn mt vng

a l, cc cell ln hn c th mrng vng phsng.

Do cc nhu cu v cc c tnh ca mt mi trng vn phng trong nh khc

vi yu cu ca ngi s dng ang i vi tc cao ti vng nng thn, din n

UMTS pht trin 6 mi trng hot ng. i vi mi m hnh mt ngi s

dng c th trn mt km2v cc loi cell c don cho cc m hnh c tnh di

ng thp, trung bnh, cao.

Hnh 2- 9 Cu


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trc cell UMTS.

2.3. Kin trc mng

2.3.1 Kin trc hthng UMTS

H thng thng tin di ng th h 3 UMTS tn dng kin trc c trong hu

ht cc h thng thng tin di ng th h2, v thm ch c th h th nht. iu ny

c chra trong cc c t k thut 3GPP

H thng UMTS bao gm mt scc phn t mng logic, mi phn tc mt

c mt chc nng xc nh. Theo tiu chun, cc phn t mng c nh ngha ti

mc logic, nhng c th li lin quan n vic thc thi mc vt l. c bit l khi c

mt scc giao din m(i vi mt giao din c coi l m, th yu cu giao

din phi c nh ngha mt cch chi tit vcc thit b ti cc im u cui m

c th cung cp bi 2 nh sn xut khc nhau). Cc phn t mng c thc nhm

li nu c cc chc nng ging nhau, hay da vo cc mng con cha chng.

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 ccc chc nng lin quan n v tuyn.

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

ni d liu n cc mng ngoi.

+ Thit bngi s dng (UE) giao tip vi ngi s dng v giao din v tuyn.

Kin trc h thng mc cao c chra trong hnh 2-10

UuIu

UE UTRAN CN

Hnh 2- 10Kin trc h thng UMTS mc cao

Theo cc c t chra trong quan im chun ha, cUE v UTRAN u bao

gm cc giao thc hon ton mi, vic thit kchng 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

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

cu.


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H thng UMTS c thchia thnh cc mng con c th hot ng c lp hoc

hot ng lin kt cc mng con khc v n phn bit vi nhau bi s nhn dng duy

nht. Mng con nh vy gi l mng di ng mt t UMTS (PLMN), cc thnh phn

ca PLMN c chra trong hnh 2-11.

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 2- 11 Cc thnh phn ca mng trong PLMN

Thit bngi sdng (UE) bao gm 2 phn:

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

din Uu.

Modul nhn dng thu bao UMTS(USIM) l mt ththng minh m nhn vic

xc nhn thu bao, thc hin thut ton nhn thc, v lu gikho m mt, kho

nhn thc v mt scc thng tin vthu bao cn thit ti u cui.

UTRAN cng 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.

Biu khin mng v tuyn (RNC) shu v iu khin ngun ti nguyn v

tuyn trong vng ca n (gm cc Nt B ni vi n). RNC l im truy cp dch

v cho tt ccc dch vm UTRAN cung cp cho mng li.

Cc phn tchnh ca mng li GSM:

HLR(Bng k thng tr) l mt c sd liu trong h thng thng tr ca

ngi s dng, lu trcc bn gc cc thng tin hin trng dch vngi s dng,

hin trng v dch v bao gm: thng tin v dch vc php s dng, cc vng

roaming b cm, thng tin cc dch v bsung 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 tuyn cc giao

dch ti UE (cc cuc gi v cc dch v nhn tin ngn), HLR cn lu tr ccthng tin vtr ca UE trong phm vi MSC/VLR hoc SGSN.


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MSC/VLR (Trung tm chuyn mch dch vdi ng/Bng k tm tr) l mt

b chuyn mch(MSC) v c sd 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 vngi 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 vtr m mng di ng mt t

cng cng UMTS kt ni vi mng ngoi. Tt cc kt ni chuyn mch knh n

v i u phi qua GMSC.

SGSN(Nt htrGPRS phc v) c chc nng tng tnh MSC/VLR nhng

thng c s dng cho cc dch v chuyn mch gi.GGSN(Node cng htrGPRS)c chc nng gn ging GMSC nhng phc v

cc dch v chuyn mch gi.

Mng ngoic thchia thnh 2 nhm:

Cc mng chuyn mch knh: Cc mng ny cung cp cc kt ni chuyn mch

knh, ging nh dch vin thoi ang tn ti V dnh ISDN v 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 giao din mc bn ca UMTS:

Giao din Cu: y l giao din gia ththng minh USIM v ME. Giao din ny

tun theo tiu chun cho cc ththng minh.

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

truy cp c vi phn cnh ca h thng, v v thc thl phn giao din m

quan trng nht trong UMTS.

Giao din Iu: Giao din ny kt ni UTRAN ti mng li. Tng tnh cc giaodin tng thch trong GSM, l giao din A (i vi chuyn mch knh), v Gb (i

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

xy dng c UTRAN v CN tcc nh sn xut khc nhau.

Giao din Iur: Giao din mIur h trchuyn giao mm gia cc RNC tcc nh

sn xut khc nhau, v v th b sung cho giao din mIu.

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 biu khin v

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


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

vc ny.

2.3.2. Kin trc mng truy nhp v tuyn UTRAN.

Kin trc UTRAN c m tnh hnh 2-12.

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 2- 12Kin 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 Biu khin mng v tuyn (RNC) vmt hay nhiuNt B. Cc RNC c thc 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:

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

ca UTRAN l cc yu cu h trchuyn 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 stng 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 tUTRA 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

UTRA.

S dng kiu chuyn vn trn c s IP nh l c cu chuyn vn thay th trong

UTRAN k t Release 5 tri.


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a. Biu khin mng v tuyn

Biu 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 m xc nh cc thng ip v th tc gia my di ng vUTRAN. V mt logic, n tng ng vi BSC trong GSM.

*Vai tr logic ca RNC.

RNC iu khin mt Nt B (nh l vch gii hn cho giao din Iub ti Nt B)

c coi nh l bRNC ang iu khin (CRNC) ca Nt. Biu khin CRNC chu

trch nhim iu khin ti v iu khin nghn cho cell ca n, v iu khin thu nhn

v phn bm cho lin kt v tuyn c thit lp trong cc cell.

Trong trng hp mt kt ni UTRAN, my di ng s dng ngun ti nguyn

t nhiu phn h mng v tuyn RNS, th cc RNS bao gm 2 chc nng logic ring

bit (vphng din kt ni my di ng - UTRAN ny).

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 RANAP

tng thch qua mng li (kt ni ny c gi l kt ni RANAP). 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 lp 2 cho cc d liu chuyn

qua giao din v tuyn. Hot ng Qun l ngun ti nguyn v tuyn c bn, nhl nh xcc thng smang thng tin truy nhp v tuyn thnh cc thng sknh

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 thl

CRNC ca mt sNt B s dng bi my di ng cho kt ni vi UTRAN. Mt UE

kt ni vi UTRAN th chc duy nht mt SRNC.

BRNC tri ( DRNC): DRNC c thl bt cRNC no ngoi SRNC, n iu

khin cc cell s dng bi my di ng. Nu cn thit, DRNC c th thc hin kt

hp hay chia nhphn tp macro. DRNC khng thc hin x l d liu ngi s

dng lp 2, nhng nh tuyn mt cch trong sut d liu gia giao din Iub v Iur,

ngoi trkhi UE ang s dng mt knh chuyn vn dng chung. Mt UE c th

khng c, c mt hoc c 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)

Chc nng chnh ca Nt B l thc hin x l lp 1 giao din v tuyn

(ghp xen v m ho knh, thch ng tc , tri ph.v.v.). N cng thc hin mt


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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 GSM.

2.4 Cc dch vv ng dng UMTS.

2.4.1. Gii thiu.

c im mi ni bt ca UMTS l tc bit ngi s dng cao hn: c th

t c tc ca kt ni chuyn mch knh 384kbps, kt ni chuyn mch gi ln

ti 2Mbps. Tc bit d liu cao hn cung cp cc dch v mi nh in thoi hnh,

v ti d liu nhanh hn.

So vi GSM v cc mng di ng ang tn ti, UMTS cung cp cc c tnh

mi v quan trng, l n cho php tho thun cc c tnh ca mt bmang v

tuyn. Cc thuc tnh nh ngha c trng ca chuyn vn bao gm: thng lng, tr

truyn, v t s li d liu. L mt h thng hon ho, UMTS phi h trrt nhiu

cc dch v c cc yu cu cht lng dch v (QoS) khc nhau. Hin ti, ta cng

khng don c ht cc c im v cch s dng ca rt nhiu cc dch v v

cng kh c th ti u cc dch vUMTS thnh ch mt tp hp cc ng dng. Cho

nn cc b mang UMTS phi c c im chung, h trcc ng dng ang tn ti

ng thi thun tin cho vic cho vic pht trin cc ng dng mi. Ngy nay khi m

hu ht cc dch v vin thng u l cc ng dng Internet hoc N-ISDN, th r rng

cc ng dng v cc dch vny ch yu l gi cc th tc iu khin cc b mang.

Phn ny khng nghin cu su vcc bmang, m s cp n cc lp dch v ca

UMTS.

2.4.2. Cc lp QoS UMTS.

Cc ng dng v dch vUMTS c chia thnh cc nhm khc nhau. Ging

nh cc giao thc chuyn mch gi mi, UMTS c gng p ng cc yu cu QoS t

cc ng dng hoc ngi s dng. Trong UMTS, c 4 lp lu lng c xc nh:

- Lp hi thoi (conversational).

- Lp lung (streaming).

- Lp tng tc (interactive).

- Cc lp nn (background).

Cc yu tphn bit gia cc lp l s nhy cm vi tr ca lu lng cc lp.

Lp hi thoi dnh cho lu lng nhy cm vi tr nht, trong khi lu lng lp nn

t nhy cm vi tr nht.

2.4.2.1 Lp hi thoi.


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ng dng c bit n nhiu nht ca lp ny l dch v thoi trn b mang

chuyn mch knh. Kt hp vi Internet v multimedia c cc ng dng mi nh:

thoi qua giao thc Internet ( Voice Over IP), v in thoi hnh (Video Telephony).

Cc dch vny c thc hin l cc cuc hi thoi thi gian thc c c im sau:

tr gia cc u cui thp (c xc nh bng cc th nghim ph hp vi khnngcm nhn m thanh v hnh nh ca con ngi, nh hn 400ms), lu lng l i

xng hoc gn nh i xng.

Dch v thoi a tc thch nghi (AMR).

UMTS s dng bm ho v gii m thoi theo cng ngha tc thch nghi

AMR. Bm ho thoi AMR c cc c im sau:

- L mt bm ho/gii m thoi tch hp n vi 8 tc ngun: 12.2 (GSM-E

-

- FR), 10.2, 7.95, 7.40(IS-641), 5.90, 5.15 v 4.75 kbps.

- Bm ho AMR hot ng vi khung thoi 20ms tng ng vi 160 mu vi tn

s ly mu l 8000 mu/s. S m ho cho chm ho a tc c gi l

Bm ho don tuyn tnh c kch thch bi m i s (ACELP).

- Tc bit AMR c thiu khin bi mng truy nhp v tuyn tu thuc vo ti

trn giao din v tuyn v cht lng ca kt ni thoi. Khi ti mng mc cao ,c bit l trong gibn, c th s dng tc bit AMR thp hn yu cu dung

lng cao hn trong khi cht lng thoi gim i rt t. Cng tng t , khi MS chy

ra ngoi vng phsng ca cell v ang s dng s dng cng sut pht ln nht

ca n, th s dng tc bit AMR thp hn mrng vng ph ca cell. Vi b

m ho thoi AMR c tht c siu ho gia dung lng vng ph ca mng

v cht lng ca thoi tutheo cc yu cu ca nh iu hnh.

in thoi hnh.

Dch vny c yu cu trtng tnh dch v thoi. Nhng do c im ca

nn video, yu cu BER nghim ngt hn thoi. UMTS chra cc c tnh trong

ITU-T Rec. H.324M s dng cho in thoi hnh trong cc kt ni chuyn mch knh

v giao thc khi to phin (SIP) h trcc ng dng a phng tin IP bao gm

dch vin thoi hnh.

2.4.2.2 Lp lung.

Lung a phng tin l mt k thut chuyn d liu nh d liu c cx l nh l mt lung lin tc v u n. Nhc cng nghstreaming, ngi s


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dng c th truy cp nhanh ti nhanh chng cc file a phng tin cc trnh duyt

c th bt u hin th d liu trc khi ton bfile c truyn ht.

Cc ng dng streaming thng rt khng i xng, cho nn phi chu nhiu

tr hn l cc dch v hi thoi i xng. iu ny c ngha l chng phi chu nhiu

jitter hn trong truyn dn.

Cc ng dng c chia thnh 2 phm vi mc ch khc nhau: Qung b web,

lung hnh nh theo yu cu. Cc nh cung cp dch v qung web thng hng

mc tiu n ng o khch hng m c kt ni vi mt my chphng tin

truyn c ti u ha hiu sut thng qua Internet. Cc dch v lung video theo yu

cu thng s dng cho cc cng ty ln mong mun lu trcc video clip hoc cc

biging vo mt my chc kt ni vi mt mng intranet ni bbng thng cao

hn.

2.4.2.3 Lp tng tc.

Khi ngi s dng u cui online yu cu d liu tcc thit b txa (my

ch), th lp tng tc c s dng. Lu lng tng tc l mt m hnh giao tip

d liu khc m c c trng bi mu p ng yu cu ca ngi s dng u cui,

thi gian tr round-trip, v tnh trong sut khi vn chuyn (vi tc li bit thp).

Mt ng dng quan trng ca lp ny l Computer game s dng cng ngh J2ME.

2.4.2.4 Lp nn.

Lu lng d liu ca cc ng dng nh l Email, dch v nhn tin ngn SMS,

dch v nhn tin a phng tin MMS (MMS l mt s mrng hon ho ca SMS)

ti vc sd liu, nhn cc bn ghi o c c th s dng lp nn v cc ng dng

ny khng i hi cc hnh ng tc th. Lu lng nn c cc c im sau: im

ch khng mong chd liu trong mt thi gian nht nh, cho nn t nhiu khng

nhy cm vi thi gian phn pht d liu; ni dung cc gi khng nht thit phi

chuyn mt cch hon ton trong sut; d liu bn thu khng c li.

Ngoi ra, trong WCDMA cn c cc dch vv ng dng da vo vtr: Dch

vnh v da vo vng phsng ca cell; skhc nhau v thi gian quan st; cc

dch vc h trca h thng nh vton cu (GPS).

2.4.3. Khnng htrdch v ca cc lp u cui.

Trong WCDMA, cc thit bu cui phi thng bo trn kt ni thit lp

cho mng mt tp hp cc thng s cho bit tnh tng thch ca phn truy nhp v

tuyn vi cc thit bu cui c bit. Khnng c th l tc d liu ngi s

dng ln nht m cu hnh v tuyn h tr mt cch c lp trn c ng ln v


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37

ng xung. 3GPP ch ra khnng truy nhp v tuyn ca thit bu cui, mt

s tham kho sau y c 3GPP chun ho choRelease99 nh sau:

Lp 32 kbps : Lp ny cung cp cc dch v thoi c bn, bao gm thoi AMR, v

d liu tc hn chln ti 32 kbps.

Lp 64 kbps: Lp ny cung cp dch v thoi v s liu bao gm c d liu v thoi

AMR ng thi.

Lp 128 kbps: Lp ny c khnng trn giao din v tuyn cung cp cc dch v

chng hn nh in thoi hnh v cc dch v d liu khc nhau.

Lp 384 kbps: Lp ny l lp tng cng cho lp 128 kbps v c chc nng a m

vi mc ch h trcc phng thc d liu gi tin tin.

Lp 768 kbps: c nh ngha l mt bc trung gian gia lp 384 kbps v lp 2

Mbps.

Lp 2 Mbps: Lp ny l tng cao nht ca lp cht lng d liu cao, chc nh

ngha cho ng xung.

Cc lp c xc nh theo quy lut cc lp cao hn c tt ccc khnng ca

lp thp hn. Trong WCDMA Release 5 a ra khnng Truy cp d liu gi ng

xung tc cao HSDPA, khnng tc ca thit bu cui c thln ti 10Mbps.

2.4. Tng kt vcng ngh truy nhp v tuyn WCDMA trong h thng UMTS

WCDMA l cng ngha truy nhp phn chia theo m bng rng s dng cho

phn giao din v tuyn cho h thng thng tin di ng th h3 UMTS. Cc thng s

ni bt c trng cho WCDMA nh sau:

WCDMA l h thng a truy nhp phn chia theo m tri phdy trc tip bng

rng DS-CDMA, ngha l cc bit thng tin c tri ra trong mt bng tn rng bng

cch nhn d liu ngi dng vi cc bit gi ngu nhin (gi l chip), cc bit ny xut

pht tcc m tri phCDMA. h trtc bit cao (ln ti 2Mbps), cn s dng

cc kt ni a m v h s tri phkhc nhau.WCDMA c tc chip l 3.84 Mcps dn n bng thng ca sng mang xp x

5MHz, nn c gi l h thng bng rng. Cn cc h thng DS-CDMA vi bng

tn khong 1 MHz nh IS-95, thng c gi l h thng CDMA bng hp. Bng

thng rng ca sng mang WCDMA h trcc tc d liu cao ca ngi dng v

em li nhng li ch hiu sut xc nh, nh l tng khnng phn tp a ng. Cc

nh vn hnh mng c th s dng nhiu sng mang 5MHz tng dung lng, c th

bng cch s dng cc lp tbo phn cp. Khong cch gia cc sng mang thc t

c thc chn l li 200KHz trong khong 4.45Mhz tu thuc vo nhiu gia

c


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38

c sng mang.

WCDMA h trtt cc tc d liu ngi dng khc nhau hay ni cch khc l

h trtt c tnh bng thng theo yu cu (BoD). Mi ngi s dng c cp cc

khung c rng 10ms, trong khi tc ngi s dng c gi khng i. Tuy

nhin dung lng ngi s dng c ththay i gia cc khung. Vic cp pht nhanh

dung lng v tuyn thng thng sc iu khin bi mng t c thng

lng ti u cho cc dch v d liu gi.

WCDMA h trm hnh hot ng c bn: Chsong cng phn chia theo tn

sFDD v song cng phn chia theo thi gian TDD (Time Division Duplex). Trong

chFDD, cc tn ssng mang 5MHz khc nhau sc s dng cho ng ln

v ng xung, trong khi ch TDD, chc 1 sng mang 5MHz c s dng

bng cch chia s min thi gian cho cc ng ln v ng xung.WCDMA h trhot ng ca cc trm gc d b, khc vi h thng ng b IS-

95, nn khng cn chun thi gian ton cu ,nh l GPS, Vic trin khai cc trm gc

micro v trm gc indoor s ddng hn khi nhn tn hiu m khng cn GPS.

WCDMA p dng k thut tch sng kt hp trn cng ln v ng xung

da vo vic s dng knh hoa tiu. Mc d c s dng trn ng xung IS-95,

nhng vic s dng tch sng kt hp trn ng ln trong h thng WCDMA l mi,

c khnng tng tng th dung lng v vng phsng ca ng ln.

Giao din v tuyn WCDMA c xy dng mt cch kho lo theo cch ca ccb thu CDMA tin tin, nh l khnng tch sng nhiu ngi dng v cc anten

thch ng thng minh, c thc trin khai bi cc nh iu khin mng nh l mt

h thng c chn la tng dung lng v vng phsng. Trong hu ht cc h

thng th h2, khng c cc iu khon cho cc khi nim b thu ny, c ngha l

chng khng c khnng ng dng hoc khng thp dng mt cch bt buc vi

vic tng hiu sut mt cch hn ch.

WCDMA c thit k giao tip vi GSM. V th, s chuyn giao gia GSM

v WCDMA c h tr ci tin vng ph sng ca GSM bng cch s dng

WCDMA.

Bng 2- 2 Tm tt cc thng s chnh ca WCDMA

Phng thc a truy nhp DS-CDMA

Phng thc song cng FDD/TDD

Vic ng b trm gc Hot ng khng ng b

Tc chip 3,84Mcps

Chiu di khung 10msGhp cc dch v Nhiu dch v vi yu cu cht lng khc nhau


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c ghp xen trn mt kt ni

Khi nim a tc Htrtc tri phkhc nhau v a m

Tch sng Tch sng kt hp s dng i din knh pilot

hoc knh pilot chung

Tch sng nhiu ngi s dng,cc Anten thng minh

c h trbi cc chun, tu chn trong qutrnh thc thi

S khc nhau gia WCDMA v cdma2000 (hay cn gi l cdmaOne bng

rng) c th ch ra trong mt scc c im c trnh by trong bng 2-3.

Bng 2- 3 Cc im khc nhau c bn ca W-CDMA v cdma2000

Thng s cdma2000 ETSI W-CDMA

Phng thc truy nhp UL: DS-CDMA

DL:Multicarrier/DS-CDMA

UL&RL: DS-CDMA

Tc chip (Mcps) Bi sca 1.2288 Bi sca 1.024

Tc iu khin cng

sut

800Hz (Tc cao hn ang

c nghin cu)

1600Hz

Cu trc knh ng

xung

Cc knh Fund/Supp c ghp

theo m

Knh pilot chung duy tr + knh

pilot ph

Cc knh c ghp theo

thi gian.

Knh pilot c ghp theo

thi gian

Cu trc knh ng ln

htrcc dch v d

liu tc cao HSD.

Knh m n vi cc m Walsh

bin i

Cc knh a m

Tri phng ln S kt hp ca m di v m

ngn tng tnh CDMA 2G

Cc m ngn da vo cc

chui m trc giao lp. M

di trn c scc m Gold.

Knh Pilot ng ln Knh pilot c ghp theo m Knh pilot c ghp theo

thi gian

Sng b trm gc ng b (cn c GPS) Khng ng b

* Ch : UL: Uplink-ng ln, DL: Downlink-ng xung


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Chng 3-iu khin cng sut v chuyn giao trong qun l ti nguyn v tuyn

40

Chng 3. IU KHIN CNG SUT V CHUYN

GIAO TRONG QUN L TI NGUYN V TUYN.

3.1 Gii thiu chung qun l ti nguyn v tuyn trong h thngWCDMA.

3.1.1 Mc ch chung ca qun l ti nguyn v tuyn

Vic qun l ti nguyn v tuyn (RRM) trong mng di ng 3G c nhim v ci

thin vic s dng ngun ti nguyn v tuyn. Cc mc ch ca cng vic qun l ti

nguyn v tuyn RRM c thtm tt nh sau :

m bo QoS cho cc dch vkhc nhau.

Duy tr vng phsng c hoch nh.

Ti u dung lng h thng.

Trong cc mng 3G, vic phn b ti nguyn v nh c qu ti ca mng

khng cn kh thi na do cc nhu cu khng don trc v cc yu cu khc nhau

ca cc dch vkhc nhau. V th, qun l ti nguyn bao gm 2 phn : t cu hnh

v t li cu hnh ti nguyn v tuyn.

Vic t cu hnh ti nguyn v tuyn c nhim vphn pht ngun ti nguynmt cch hp l cho cc yu cu mi ang a n h thng cho mng khng

bqu ti v duy tr tnh n nh. Tuy nhin, nghn c th xut hin trong mng

3G v s di chuyn ca ngi s dng.

Vic t li cu hnh c nhim v cp pht li ngun tinguyn trong phm vi

ca mng khi hin tng nghn bt u xut hin. Chc nng ny c nhim va

h thng bqu ti trvlu lng ti mc tiu mt cch nhanh chng v c th

iu khin c.

3.1.2. Cc chc nng ca qun l ti nguyn v tuyn RRM.

Qun l ngun ti nguyn v tuyn c thchia thnh cc chc nng: iu khin

cng sut, chuyn giao, iu khin thu nhn, iu khin ti v lp lch cho gi tin.

Hnh 3-1 chra cc vtr in hnh ca cc chc nng RRM trong phm vi ca

mt mng WCDMA.


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Hnh 3- 1 Cc v tr in hnh ca cc chc nng RRM trong mng WCDMA

a. iu khin cng sut.

iu khin cng sut l mt cng vic quan trng trong tt ccc h thng di

ng v vn tui th ca pin v cc l do an ton, nhng trong cc h thng CDMA,

iu khin cng sut l cn thit bi v c im gii hn nhiu ca CDMA.

Trong cc h thng GSM, chp dng iu khin cng sut chm (tn s xp x

2Hz). Trong IS-95, iu khin cng sut nhanh vi tn s 800Khz c h tr

ng ln, nhng trn ng xung, mt vng iu khin cng sut tng i chm

(xp x 50Hz) iu khin cng sut truyn. Trong WCDMA, iu khin cng sut

nhanh vi tn s1,5KHz c s dng trn cng ln v ng xung. iu khincng sut nhanh khp kn l mt vn quan trng ca h thng WCDMA.

b. iu khin chuyn giao.

Chuyn giao l mt phn quan trng ca h thng thng ti di ng tbo. S di

chuyn gy ra s bin i cht lng lin kt v cc mc nhiu trong cc h thng t

bo, yu cu khi mt ngi s dng c ththay i trm gc phc vn. Sthay i

ny c gi l chuyn giao.

c. iu khin thu np.

Nu ti giao din v tuyn c cho php tng ln mt cch lin tc, vng ph

sng ca cell b gim i di gi tr hoch nh (gi l cell breathing), v QoS

ca cc kt ni ang tn ti khng th m bo. Nguyn nhn ca hiu ng cell

breathing l v c im gii hn nhiu ca cc h thng CDMA. V th, trc khi

thu nhn mt kt ni mi, iu khin thu np cn kim tra xem vic nhn kt ni mi

skhng nh hng n vng phsng hoc QoS ca cc kt ni ang hot ng.

iu khin thu np chp nhn hay t chi yu cu thit lp mt b mang truy nhp v


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tuyn trong mng truy nhp v tuyn. Chc nng iu khin thu np c t trong b

iu khin mng v tuyn RNC, ni m lu githng tin v ti ca mt s cell.

Thut ton iu khin thu np tnh ton vic ti tng ln m do s thit lp thm

vt mang sgy ra trong mng truy nhp v tuyn. Vic tnh ton ti c p dng

cho cng ln v ng xung. Bmang yu cu c thc chp nhn ch khi

iu khin thu np trong c 2 chiu chp nhn, nu khng th n b t chi bi v

nhiu qu mc c thtng thm trong mng.

Nhn chung cc chin lc iu khin thu np c thchia thnh hai loi: chin

lc iu khin thu np da vo cng sut bng rng v chin lc iu khin thu np

da vo thng lng.

Ngi s dng mi khng c chp nhn nu mc nhiu tng th mi to ra

cao hn gi tr mc ngng Ithreshold:

+ Tchi : Itotal-old + I > Ithreshold (3.1)

+ Chp nhn : Itotal-old + I < Ithreshold

Gi trngng ging vi tng nhiu ng ln ln nht v c thc thit

lp bi vic quy hoch mng v tuyn.

Hnh 3- 2ng cong ti

Trong chin lc iu khin thu np da vo thng lng, ngi s dng mi

khng c thu nhn truy nhp vo mng v tuyn nu ton b ti mi gy ra cao hn

gi trngng:

+Tchi : total-old + I > threshold

+Chp nhn : total-old + I < threshold (3.2)


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Ch rng vic iu khin thu np c p dng mt cch tch bit trn c

ng ln v ng xung, v mi hng c th s dng cc chin lc iu khin

thu np khc nhau.

d.iu khin ti (iu khin nghn).Mt cng c quan trng ca chc nng qun l ngun ti nguyn v tuyn l

m bo cho h thng khng bqu ti v duy tr tnh n nh. Nu h thng c quy

hoch mt cch hp l, v cng vic iu khin thu np hot ng tt, cc tnh hung

qu ti s b loi tr. Tuy nhin, trong mng di ng, squ ti mt ni no l

khng thtrnh khi v cc ti nguyn v tuyn c n nh trc trong mng. Khi

qu ti c xl bi iu khin ti, hay cn gi l iu khin nghn, hot ng iu

khin ny s tr li cho h thng ti mc tiu, c vch ra trong qu trnh quy hoch

mng mt cch nhanh chng v c kh nng iu khin c. Cc hot ng iu

khin ti lm gim hay cn bng ti c lit k nh sau:

T chi cc lnh cng sut ti trn ng xung nhn t MS.

Gim chtiu Eb/I0ng ln s dng bi iu khin cng sut nhanh ng ln.

Thay i kch cca min chuyn giao mm phc v nhiu ngi s dng hn.

Chuyn giao ti sng mang WCDMA khc (mng UMTS khc hay mng GSM).

Gim thng lng ca lu lng d liu gi (cc d liu phi thi gian thc).Ngt cc cuc gi trn mt ng iu khin.

Hai hot ng u tin l cc hot ng nhanh c thc hin bn trong BS. Cc

hot ng ny c th din ra trong mt khe thi gian, ngha l vi mt tn s 1,5KHz,

cung cp mt quyn u tin cho cc dch vkhc nhau. Hot ng th3 thay i kch

cca min chuyn giao mm c mt li ch c bit i vi mng gii hn ng

xung.

Cc phng php iu khin ti khc th chm hn. Chuyn giao bn trong bngtn v chuyn giao bn trong h thng c th khc phc c hin tng qu ti bng

cch cn bng ti. Hot ng cui cng l ngt cc ngi s dng dch v thi gian

thc (nh l thoi hay d liu chuyn mch knh) gim ti. Hot ng ny ch

c s dng ch khi ti ca ton b mng vn rt ln thm ch sau khi cc hot ng

iu khin ti khc va c tc dng gim qu ti. Giao din v tuyn WCDMA v

yu cu tng ca lu lng phi thi gian thc trong mng 3G em li nhiu s la

chn cc hot ng kh thi iu khin tnh hung qu ti, v v th nhu cu ct

nhng ngi s dng dch v thi gian thc gim qu ti rt him xy ra.


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3.2 iu khin cng sut

3.2.1 Gii thiu chung

Mc tiu ca vic s dng iu khin cng sut l khc nhau trn ng ln v

ng xung. Cc mc tiu ca iu khin cng sut c thtm tt nh sau : Khc phc hiu ng gn-xa trn ng ln.

Ti u dung lng h thng bng vic iu khin nhiu.

Lm tng ti a tui th pin ca u cui di ng.

Hnh 3-3 ch ra hiu ng gn-xatrn ng ln. Tn hiu tcc MS khc nhau

c truyn i trong cng bng tn mt cch ng thi trong cc h thng WCDMA.

Khng c iu khin cng sut, tn hiu n t MS gn vi BS nht c th chn cc

tn hiu tcc MS khc cch xa BS hn. Trong tnh hung xu nht, mt MS c cngsut qu ln c th chn ton b mt cell. Gii php l phi p dng iu khin cng

sut m bo rng cc tn hiu n tcc u cui khc nhau c cng cng sut

hay c cng t stn hiu trn nhiu (SIR) khi chng n BS.

Hnh 3- 3Hiu ng gn-xa (iu khin cng sut trn ng ln)

Trn ng xung, khng c hiu ng gn-xa do m hnh mt-ti-nhiu. iu

khincng sut c nhim vb 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 3-4). Hn th

na, iu khin cng sut trn ng xung c nhim v lm gim thiu ton b

nhiu bng cch gi QoS ti mc gi tr mc tiu.

Hnh 3- 4B nhiu bn trong cell (iu khin cng sut ng xung)


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Trong hnh 3-4, 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.

C 3 kiu iu khin cng sut trong cc h thng WCDMA : iu khin cng

sut vng m, iu khin cng sut vng kn, v iu khin cng sut vng bn ngoi.

a) iu khin cng sut vng m(Open-loop power control)

iu khin cng sut vng mc s dng trong UMTS FDD cho vic thit

lp nng lng ban u cho MS. Trm di ng stnh ton suy hao ng truyn gia

cc trm gc v trm di ng bng cch o cng tn hiu nhn s dng mch iu

khin tng ch tng (AGC). Tu theo s tnh ton suy hao ng truyn ny,

trm di ng c th quyt nh cng sut pht ng ln ca n. iu khin cng sut

vng m c nh hng trong h thng TDD bi v ng ln v ng xung ltng h, nhng khng nh hng nhiu trong cc h thng FDD bi v cc knh

ng ln v ng xung hot ng trn cc bng tn khc nhau v hin tng

Phadinh Rayleigh trn ng ln v ng xung c lp nhau. Vy iu khin cng

sut vng mchc thb mt cch i khi suy hao do khong cch. l l do t i

sao iu khin cng sut vng mchc s dng nh l vic thit lp nng lng

ban u trong h thng FDD.

b) iu khin cng sut vng kn.

iu khin cng sut vng khp kn, c gi l iu khin cng sut nhanh

trong cc h thng WCDMA, c nhim viu khin cng sut pht ca MS (ng

ln), hay l cng sut ca trm gc (ng xung) chng li phadinh ca cc knh

v tuyn v t c chtiu t stn hiu trn nhiu SIR c thit lp bi vng bn

ngoi. Chng hn nh trn ng ln, trm gc so snh SIR nhn c t MS vi SIR

mc tiu trong mi khe thi gian (0,666ms). Nu SIR nhn c ln hn mc tiu, BS

s truyn mt lnh TPC 0 n MS thng qua knh iu khin ring ng xung.

Nu SIR nhn c thp hn mc tiu, BS s truyn mt lnh TPC 1 n MS. Biv tn s ca iu khin cng sut vng kn rt nhanh nn c th b c phadinh

nhanh v c phadinh chm.

c) iu khin cng sut vng bn ngoi

iu khin cng sut vng bn ngoi cn thit gi cht lng truyn thng ti

cc mc yu cu bng cch thit lp mc tiu cho iu khin cng sut vng kn

nhanh. Mc ch ca n l cung cp cht lng yu cu. Tn s ca iu khin cng

sut vng bn ngoi thng l 10-100Hz.


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iu khin cng sut vng bn ngoi so snh cht lng nhn c vi cht

lng yu cu. Thng thng, cht lng c nh ngha l t li bit mc tiu xc

nh (BER) hay T s li khung (FER). Mi quan h gia SIR mc tiu v mc tiu

cht lng tu thuc vo tc di ng v hin trng a ng. Nu cht lng nhn

tt hn, c ngha l mc tiu SIR cao m bo QoS yu cu. gim thiukhong trng, mc tiu SIR s phi gim. Tuy nhin, nu cht lng nhn xu hn

cht lng yu cu, mc tiu SIR phi tng ln m bo QoS yu cu.

3.2.2 iu khin cng sut nhanh

3.2.2.1 li ca iu khin cng sut nhanh

iu khin cng sut nhanh trong WCDMA em li nhiu li ch cho h thng.

Chng hn i vi dch v m phng c tc 8kbps vi BLER=1% v ghp xen

10ms. Sm phng c to ra trong trng hp c hoc khng c iu khin cngsut nhanh vi bc cng sut l 1dB. iu khin cng sut chm c ngha l cng

sut trung bnh c gi ti mc mong mun v iu khin cng sut chm hon ton

c thb cho nh hng ca suy hao ng truyn v suy hao do cc vt chn, trong

khi iu khin cng sut nhanh c thb c cho phadinh nhanh. Phn tp thu

hai nhnh c s dng trong Nt B. ITU Vehicular A l mt knh 5 nhnh trong

WCDMA, v ITU Pedestrian A l mt knh 2 nhnh trong nhnh th hai rt yu.

T s Eb/N0, v cng sut truyn trung bnh yu cu trong trng hp khng c v c

iu khin cng sut nhanh c trnh by trong bng 3.1 v bng 3.2

Bng 3- 1 Gi tr Eb/N0yu cu trong trng hp c v khng c iu khin cng sut nhanh

iu khin

cng sut chm

iu khin cng sut

nhanh tn s 1.5KHz

li ca iu khin

cng sut nhanh

ITU PedestrianA 3km/h 11.3dB 5.5dB 5.8dB

ITU Vehicular A 3km/h 8.5dB 6.7dB 1.8dB

ITU VehicularA 50km/h 7.3dB 6.8dB 0.5dB

Bng 3- 2 Cng sut pht tngi yu cu trong trng hp c v khng c iu khin

cng sut nhanh

iu khin

cng sut chm

iu khin cng sut

nhanh tn s 1.5KHz

li ca iu khin

cng sut nhanh

ITU PedestrianA 3km/h 11.3dB 7.7dB 3.6dB

ITU Vehicular A 3km/h 8.5dB 7.5dB 1.0dB

ITU VehicularA 50km/h 7.6dB 6.8dB 0.8dB

Trong 2 bng trn ta thy r li m iu khin cng sut nhanh em li nh sau:

li ca cc UE tc thp ln hn cc UE tc cao.


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li theo t s Eb/I0yu cu ln hn li cng sut truyn dn.

Trong 2 bng, li m ti tc 50km/h c ngha l iu khin cng sut chm

l tng sem li hiu sut tt hn so vi iu khin cng sut nhanh thc t.

li m do vic tnh ton SIR khng chnh xc, cc li bo hiu iu khin cng sut,

v trtrong vng iu khin cng sut.

li tiu khin cng sut nhanh trong bng 3-6 c thc s dng tnh

ton d tr phadinh nhanh yu cu trong qu ng truyn. d tr phadinh

nhanh cn thit cho cng sut pht ca UE duy tr iu khin cng sut nhanh vng

kn thch hp. Kch thc cell ln nht c tht c khi UE ang pht vi lng

cng sut khng i ngha l khng c li ca iu khin cng sut nhanh. Gi tr

thng thng cho d trphadinh nhanh cho cc tc di ng thp t2 n 5dB.

3.2.2.2 Phn tp v iu khin cng sut.

Hnh 3- 5 Cng sut pht v thu trong 2 nhnh (cng sut khong h trung bnh 0dB,- 10dB)

Knh phadinh Rayleigh ti 3km/h

Tm quan trng ca phn tp s c phn tch cng vi iu khin cng sut

nhanh. Vi cc UE tc thp, iu khin cng sut nhanh c thb c phadinh

ca knh v gi cho mc cng sut thu khng i. Cc nguyn nhn chnh ca cc li

trong cng sut thu l do vic tnh ton SIR khng chnh xc, cc li bo hiu v tr

trong vng iu khin cng sut. Vic b phadinh gy ra suy gim cng sut truyn

dn. Cng sut thu v cng sut pht l hm ca thi gian, hnh 3-5, 3-6 ti tc ca

UE l 3km/h. Trong hnh 3-5 l trng hp c t phn tp, hnh 3-6 m phng trng

hp phn tp nhiu. S bin i cng sut pht trong trng hp hnh 3-5 cao hn

trong trng hp 3-6 do skhc nhau v slng phn tp. Cc trng hp phn tp

nh: phn tp a ng, phn tp anten thu, phn tp anten pht hay phn tp v m.


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Vi sphn tp t hn th s bin ng ln hn trong cng sut pht, nhng cng

sut pht trung bnh cng cao hn. Mc tng cng sut l c nh ngha l t s

gia cng sut truyn dn trung bnh trn knh phadinh v trn knh khng c

phadinh khi mc cng sut thu ging nhau trn c 2 knh c phadinh v khng c

phadinh. Mc tng cng sut c m ttrong hnh 3-7

Hnh 3- 6Cng sut pht v thu trn 3 nhnh (cng sut khong h nhnhau)Knh phadinh Rayleigh ti tc 3km.

Hnh 3- 7Cng sut tng trong knh phadinh vi iu khin cng sut nhanh

Kt qumc lin kt cho stng cng sut ng ln th hin trong bng 3.3.

Sm phng c thc hin ti cc mc UE khc nhau trn knh ITU pedestrian 2

ng vi cng sut thnh phn a ng t0 n -12.5dB. Trong sm phng ny

cng sut pht v cng sut thu c tp hp trong tng khe. Vi iu khin cng sut

l tng, mc tng cng sut l 2,3dB. iu chng tiu khin cng sut nhanhhot ng c hiu qu trong vic b nng lng cho phadinh. Vi cc UE tc cao


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(>100km/h), mc tng cng sut rt nhdo iu khin cng sut nhanh khng thb

c phadinh.

Mc tng cng sut rt quan trng i vi hiu sut ca cc h thng WCDMA.

Trn ng xung, dung lng giao din v tuyn c xc nh trc tip bi cng

sut pht yu cu, do cng sut xc nh nhiu truyn. V th, lm tng ti a

dung lng ng xung, cng sut pht cn cho mt lin kt phi c gim nh.

Trn ng xung, mc cng sut thu trong UE khng nh hng n dung lng.

Trn ng ln, cng sut pht xc nh tng nhiu n cc cell ln cn, v cng sut

thu xc nh tng nhiu n cc UE khc trong cng mt cell. Chng hn nh chc

mt cell WCDMA trong mt vng, dung lng ng ln ca cell ny sc tng

ti a bng cch gim ti thiu cng sut thu yu cu, v mc tng cng sut skhng

nh hng n dung lng ng ln.

Bng 3- 3 Cc mc tng cng sut c minh ho ca knh ITUPedestrian A a ng vi phn tp anten.

Tc UE Mc tng cng sut trung bnh

3km/h 2,1dB

10km/h 2,0dB

20km/h 1,6dB

50km/h 0,8dB

140km/h 0,2dB

3.2.2.3 iu khin cng sut trong chuyn giao mm.

iu khin cng sut trong chuyn giao mm c hai vn chnh khc nhau

trong cc trng hp lin kt n: vn tri cng sut trong Nt B trn ng

xung , v pht hin tin cy cc lnh iu khin cng sut ng ln trong UE.

a. Stri cng sut ng xung.

Stri cng sut l trng hp xy ra khi thc hin chuyn giao mm m UE gi

mt lnh n iu khin cng sut pht ng xung n tt ccc Nt B trong tphp tch cc. Cc Nt B spht hin cc lnh ny mt cch c lp, bi v cc lnh

ny skhng c kt hp trong cc biu khin mng RNC do sgy ra nhiu tr

v bo hiu trong mng. Chnh v cc li bo hiu trn giao din v tuyn, cc Nt B

spht hin cc lnh iu khin cng sut theo cc cch khc nhau. C th mt Nt B

slm gim cng sut pht ca n ti UE, mt Nt B khc c th li tng mc cng

sut pht ti UE. Skhc nhau dn n tnh hung cng sut ng xung bt u

tri theo hng khc nhau. Hin tng gi l tri cng sut.

Hin tng tri cng sut l khng mong mun, bi v n lm gim hiu sutchuyn giao ng xung. Vn ny c thc iu khin bi RNC. Phng php


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n gin nht l thit lp gii hn tng i nghim ngt cho khong bin ng cng

sut ng xung. Gii hn ny cho cng sut pht c th ca cc UE. R rng

khong bin ng iu khin cng sut cho php cng nh th tri cng sut ln

nht cng nh. Mt khc khong bin i iu khin cng sut thng ci thin hiu

sut iu khin cng sut.

CongsuatphattNutB1

CongsuatphattNutB2

Nut B1

Nut B2

Troi congsuat

Lenh ieu khien cong suatn t UE en ca hai Nut B

1. Phat hien lenh cong suat ng xuong2. ieu chnh oc lap cong suat ngxuong so vi cac Nut B khac=> Cong suat truyen co the troi tngphan

RNCieu khientroi cong suat

Hnh 3- 8 Tri cng sut ng xung trong chuyn giao mm

Lenhieukhiencongsuat

nglen1

Lenhieukhiencongsuat

nglen 2

Nut B1

Nut B2

Kiem tra otin cay

UE co the giam cong suat phatneu co t nhat mot lenh ieukhien cong suat tin cay en no

1. Tnh toan Eb/No cua tn hieu ng lenoc lap vi cac Nut B khac2. Gi lenh ieu khien cong suat en UE=> Hai Nut B khac nhau co the gi cac lenhieu khien cong suat khac nhau ti UE

RNCUE

Hnh 3- 9Kim tra tin cy ca iu khin cng sut ng ln ti UE trong chuyn giaomm


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Mt cch khc gim stri cng sut. RNC c th nhn thng tin tcc Nt

B vcc mc cng sut pht ca kt ni chuyn giao mm. Cc mc ny c tnh

trung bnh trn mt scc lnh iu khin cng sut, v dnh trong 500ms, hay trn

750 lnh iu khin cng sut. Da vo cc thng so c ny, RNC c th gi cc

gi tr tham kho vcng sut pht ng xung ti cc Nt B. Cc Nt B ang thc

hin chuyn giao mm s dng cc gi tr tham kho ny cho vic iu khin cng

sut ng xung cho cc kt ni gim hin tng tri cng sut. Nh vy cn mt

s hiu chnh nhmang tnh nh khng ti cng sut tham kho. Kch chiu

chnh ny t l thun vi chnh lch gia cng sut pht thc tv cng sut pht

tham kho. Phng php ny s gim bt hin tng tri cng sut. Stri cng sut

ch xy ra nu c iu khin cng sut nhanh trn ng xung. Trong IS-95 chc

iu khin cng sut chm trn ng xung nn khng cn phng php iu khin

stri cng sut ng xung.

b. tin cy ca cc lnh iu khin cng sut ng ln.

Tt ccc Nt B trong tp hp tch cc gi mt lnh iu khin cng sut

c lp n cc UE iu khin cng sut pht ng ln. Ch cn mt trong cc

Nt B trong tp hp tch cc nhn ng tn hiu ng ln l . V thUE c th

gim cng sut pht nu mt trong cc Nt B gi cc lnh cng sut xung. C thp

dng s kt hp theo t s ln nht cc bit d liu trong chuyn giao mm ti UE do

d liu ging nhau c gi t tt ccc Nt B thc hin chuyn giao mm, nhng s

kt hp ny khng p dng cho cc bit iu khin cng sut v n cha thng tin khc

nhau i vi mi Nt B trong tp hp tch cc. V th tin cy ca cc bit iu

khin cng sut khng tt bng cc bit d liu, v ti UE, mt ngng c s dng

kim tra tin cy ca cc lnh iu khin cng sut. Cc lnh khng ng tin cy

phi c hu bv chng b hng do nhiu.

c. Ci thin cht lng bo hiu iu khin cng sut .

Cht lng bo hiu iu khin cng sut c thc ci thin bng cch thit

lp mt cng sut cao hn cho cc knh iu khin vt l ring (DPCCH) so vi mc

cng sut ca knh d liu vt l ring (DPDCH) trn ng xung nu nh UE ang

trong trng thi chuyn giao mm. chnh lch cng sut gia hai knh ny c th

khc cho cc cho cc loi knh DPCCH khc nhau nh: cc bit iu khin cng sut,

cc bit pilot v TFCI.

gim cng sut pht UE thng thng c th t c ti 0,5dB vi s

chnh lch cng sut ny. gim ny c tht c do cht lng ca bo hiuiu khin cng sut c ci thin.


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3.2.3 iu khin cng sut vng ngoi.

iu khin cng sut vng ngoi cn gi cht lng thng tin cc mc

yu cu bng vic thit lp mc tiu cho vic iu khin cng sut nhanh. Mc ch

ca iu khin cng sut vng ngoi l cung cp cht lng t yu cu. Cht lng

qu cao s tn rt nhiu dung lng. iu khin cng sut vng ngoi cn thit trn c

ng ln v ng xung. Vng ngoi ng ln c t trong RNC cn vng bn

ngoi ng xung t trong UE. Trong IS-95, iu khin cng sut vng ngoi ch

s dng trn ng ln v khng c iu khin cng sut nhanh trn ng xung.

Cht lng ng ln nhn c sau khi kt hp phn tp v m trong RNC v

SIR mc tiu c gi n cc Nt B. Tn s ca iu khin cng sut nhanh l

1,5KHz v tn siu khin cng sut vng ngoi thng t 10-100Hz.

3.2.3.1. li ca iu khin cng sut vng ngoi.

SIR mc tiu cn phi c iu chnh khi tc ca UE hoc mi trng

truyn sng a ng thay i. SIR mc tiu chnh l Eb/N0. Kt qum phng vi

cc dch v thoi a tc thch nghi AMR v BLER=1% c ch ra trong bng 3-4

s dng iu khin cng sut vng ngoi.

Bng 3- 4 Kt qum phng dch v AMR , BLER= 1%, sdng iu khin cng sut

vng ngoi

Hin trng a ng Tc UE Mc tiu Eb/N0trung bnhKhng phadinh - 5.3dB

ITU Pedestrian A 3 km/h 5.9dB




Cng sut bng nhau trn 3 ng 3 km/h 6.0dB

Cng sut bng nhau trn 3 ng 20 km/h 6.4dB

Cng sut bng nhau trn 3 ng 50 km/h 6.4dBCng sut bng nhau trn 3 ng 120 km/h 6.9dB

C 3 loi a ng c s dng: knh khng c phadinh tng ng vi phn

t LOS kho, knh

tính toán đường truyền WCDMA

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