he thong sau 3g

8/14/2019 he thong sau 3g

1/95

HC VIN CNG NGH BU CHNH VIN THNG

C S TI THNH PH H CH MINH

KHOA VIN THNG II

_____________

N

TT NGHIP I HCCHUYN NGNH: IN T - VIN THNG

H O TO: VN BNG HAI

ti:

CC CNG NGH DI NG

SAU 3G

M s ti: 09406861003

Sinh vin thc hin: PHM HONG DNG

M s sinh vin: 406861003

Lp: 06VTK1

Gio vin hng dn: PHM THANH M

TPHCM 2009


2/95

Cc cng ngh khng dy Sau 3G i

Sinh vin thc hin: Phm Hong Dng 06VTK1

Mc lc

Li ni u 1

Chng 1: S pht trin t 2G qua 3G ln 4G 31.1. Na u thp k 1990: Vin thng ch yu l thoi 3

1.2. T 1995 n 2000: s ct cnh ca vin thng di ng v Internet 3

1.3. T 2000 n 2005: Dot Com suy sp, xut hin Web 2.0 v Mobile Internet 4

1.4. T 2005 n nay: thoi di ng ph sng ton cu, VoIP v Mobile

Broadband bt u ph bin 6

1.5. Tng lai Nhu cu i vi cc h thng Sau 3G 7

1.6. Tt c cc h thng ny u da trn IP 10Chng 2: Tng quan cc kin trc Sau 3G

Cc h thng UMTS, HSPA, v HSPA+ 13

2.1. Tng quan 13

2.2. UMTS 14

2.2.1. Gii thiu 14

2.2.2. Kin trc mng 14

2.2.3. Giao tip v tuyn v mng truy nhp v tuyn 22

2.3. HSPA (HSDPA v HSUPA) 33

2.3.1. Cc knh dng chung (shared channel) 332.3.2. a m tri 34

2.3.3. iu ch cp cao hn 35

2.3.4. Sp t lch truyn, iu ch v m ha, HARQ 36

2.3.5. Cp nht v chuyn giao cell 37

2.3.6. HSUPA 38

2.4. HSPA+ v nhng ci tin khc: Cnh tranh vi LTE 40

2.4.1. iu ch cp cao hn na 40

2.4.2. MIMO 41

2.4.3. Kh nng truyn gi lin tc (Continuos Packet Connectivity) 41

2.4.4. Cc trng thi Enhanced Cell-FACH, Enhanced Cell/URA-PCH 44

2.4.5. Ci tin mng v tuyn: Mt ng hm duy nht (One-tunnel) 46

2.4.6. Cnh tranh vi LTE di tn 5 MHz 47

Chng 3: LTE v LTE-Advanced 483.1. Gii thiu 48

3.2. Kin trc mng 49

3.2.1. Cc trm c s ci tin 49

3.2.2. ng giao tip gia mng li vi mng truy nhp v tuyn 503.2.3. Gateway ni vi Internet 51


3/95

Cc cng ngh khng dy Sau 3G ii


3.2.4. ng giao tip vi c s d liu ngi dng 52

3.2.5. Chuyn qua chuyn li gia nhng cng ngh v tuyn khc nhau 52

3.2.6. Thut ng thit lp cuc gi gi tr thnh lch s 52

3.3. Air Interface v mng v tuyn ca LTE 53

3.3.1. Truyn d liu hng xung 533.3.2. Truyn d liu hng ln 55

3.3.3. Cc thng s vt l 56

3.3.4. T khe n khung 57

3.3.5. Cc k hiu tham chiu v cc knh truyn 58

3.3.6. Hng xung: Knh qung b 59

3.3.7. Hng xung: Knh nhn tin 60

3.3.8. Hng xung v hng ln: Cc knh truyn ti v knh iu khin

dnh ring, v vic nh x chng vo knh vt l dng chung 60

3.3.9. Hng xung: Cc knh iu khin tng vt l 603.3.10: Hng ln: Cc knh iu khin tng vt l 61

3.3.11. Cp pht lch truyn linh ng v cp pht lch truyn lu di 61

3.3.12. Truyn MIMO trong LTE 62

3.3.13. Tnh ton thng sut LTE 63

3.3.14. Kim sot ti nguyn v tuyn 64

3.3.15. Trng thi tch cc RRC 65

3.3.16. Trng thi ri RRC 65

3.3.17. X l cc gi d liu eNodeB 66

3.4. Cc th tc bo hiu c bn 673.4.1. Tm kim mng v qung b cc thng tin h thng 68

3.4.2. Lin h ban u vi mng 68

3.4.3. Xc minh thu bao (authentication) 68

3.4.4. Yu cu cp pht mt a ch IP 69

3.5. Tng kt v so snh vi HSPA 69

3.6. LTE-Advanced 70

Chng 4: WiMAX (IEEE 802.16) 714.1. Gii thiu 72

4.2. Kin trc mng 72

4.2.1. Cc mng nh dnh cho khch hng c nh 72

4.2.2. Cc mng t va ti ln v tnh di ng 72

4.2.3. ASN-GW 74

4.2.4. Xc minh v m ha 74

4.2.5. Cp pht a ch IP cho my khch v cc knh R6 76

4.2.6. Qun l tnh di ng tm vi m 76

4.2.7. Qun l tnh di ng tm v m 77

4.3. Giao tip v tuyn v mng v tuyn ca WiMAX c nh 802.16d 78

4.4. Giao tip v mng v tuyn ca WiMAX di ng 80


4/95

Cc cng ngh khng dy Sau 3G iii


4.4.1. OFDMA (Orthogonal Frequency Division Multiple Access) 81

4.4.2. Truyn MIMO trong WiMAX 82

4.4.3. Cc h thng ng-ten thch nghi (AAS) 82

4.4.4. Cc th tc chuyn giao 83

4.4.5. Ch tit kim in nng v ch ng 844.4.6. Ch ri 84

4.5. Cc th tc bo hiu c bn 85

4.6. Tng kt v so snh vi HSPA v LTE 86

4.7. Cc cng ngh ny cnh tranh lnh mnh 87

Danh mc cc t vit tt 88

Ti liu tham kho 91


5/95

Cc cng ngh di ng Sau 3G 1


Li ni u

Trong nhng nm gn y, cc mng thoi t ong(cellular telephone network1, hay ngn gnhn: cellular network) bin i thnh nhng mng truy cp chuyn gi rt mnh m, phc vcho c truyn thoi ln truy cp Internet. Cc mng 3.5G hin ti, chng hn nh UMTS/HSDPAv CDMA 1xEvDO, gi y cung cp nhng thng lng ln n vi Mbps cho nhng ngidng ring r, v kh nng truy cp di ng vo Internet t cc thit b cm tay v my tnh xchtay khng cn c xem l thp hn mt mi ni kt DSL hoc cp na. Th nhng, yu cu v

bng thng v dung lng vn khng ngng tng ln do bi lng ngi dng gia tng trongcc mng y v do nhng ng dng i hi cao v bng thng chng hn nh truyn phim nhv truy cp Internet di ng t my tnh xch tay. V vy, cc nh ch to mng v cc nh iuhnh mng vin thng cn tm ra nhng phng cch no lm tng dung lng v hiunng lm vic trn cc mng ca h, trong khi vn gi gi thnh thp hay thm ch cn gim i.

Trong qu kh, s tin ha ca mng truyn thng khng dy ch yu lin quan n vic thitk cc mng truy nhp c di tn cao hn v thng lng ln hn. Khi chng ta tin n thi kcc kin trc mng Sau 3G2, gi y c mt s tin ha cn nhanh hn na cc mng li, vquan trng nht l cc thit b v ng dng dnh cho ngi dng. S tin ha ny tip tcnhng xu hng cng ngh vn ng trn trong th gii mng Internet ng truyn cnh hin nay. Cc h thng in thoi chuyn knh ang c thay th bi cc cng nghVoIP, cn Web 2.0 th khuyn khch ngi dng tr thnh nhng nh sng to ni dung v chias thng tin ca mnh vi ton th gii. Trong tng lai, cc mng khng dy broadband s c

mt nh hng rt quan trng i vi xu hng ny, bi l in thoi di ng v my tnh xchtay l nhng cng c l tng sng to v tiu th ni dung. Phn ln cc in thoi di ngv my tnh xch tay hin nay u c trang b nhng my nh s tin tin, v kh nngquay phim chp nh ca chng ngy cng tt hn.

Mt khc, chng ta ang chng kin cc cng ngh mobile broadband ngy cng tr nntng ng v mt giao tip v tuyn (air interface) v kin trc ni mng (networkingarchitecture); chng ang c hi t thnh mt kin trc mng da trn IP cng vi cng nghgiao tip v tuyn da trn OFDMA (Orthogonal Frequency Division Multiple Access _a truycp phn tn trc giao). Mc d s tin ha v kin trc mng cha t n mc hi t y v thc s, nhng cc loi mng truy cp khng dy nhng giai on khc nhau ca qu trnh

tin ha ny amg c thit k p ng vic truyn cc dch v a phng tin khp nithng qua vic ni kt lin mng.

1 Cellular c cn ng l cell, cn cell y c ngha l ngn, , hoc l t ong. Gi nh vy l v, cccell trong mng c m hnh bng nhng hnh lc gic sp k cn nhau ti s dng tn s nhng vng cch xanhau theo nguyn tc a truy cp phn chia theo khng gian (SDMA). Cch sp xp ny ging cch sp xp cc lhay ngn trong cu trc ca t ong (cellular construction of a beehive).

2 Thut ng Sau 3G l c chuyn t thut ng Beyond 3G trong ting Anh sang. Thut ng gc nyvn ch c qui c tm ch cha c nh ngha chnh xc, dng ch cc h thng cng ngh di ng thuc loiEnhanced IMT-2000 theo qui nh ca ITU (xem Chng 1), nhng tr nn ph bin (thm ch c dng

mt s nc khng ni ting Anh). Vit Nam, thut ng c chuyn thnh Hu 3G v Sau 3G, trong Hu 3G ph bin hn so vi Sau 3G (c th kim chng iu ny bng cch tm kim cc cm t trn Webthng qua cc cng c nh Google, Yahoo! hoc Bing chng hn), tuy nhin y chng ti s dng Sau 3G.


6/95



Tuy cc xu hng tin ha cng ngh ny v ang din ra, c rt t ti liu m t chng vmt k thut, nht l Vit Nam. Lun vn ny c gng m t s tin ha ca nhng cng nghtruyn thng khng dy t 3G tr v sau. N tp trung bn v s tin ha ca truyn thng ding 3G v Sau 3G, nh c xy dng bi t chc chun ha 3GPP (3rd GenerationPartnership Project), lu n s tin ha v k thut truy cp v tuyn v mng truy nhp.

Lun vn ny bao gm bn chng. Chng 1 im qua lch s tin ha ca cc mng ding trong qu kh, ri lit k nhng xu hng tin ha ang ni ln hin nay. Chng 2 bnsu v cc cng ngh truy cp v tuyn hu du ca cng ngh GSM ph bin hin nay: UMTS,HSPA v HSPA+. Chng 3 bn tip v cc th h ci tin ca HSPA: LTE v LTE-Advanced.Cui cng, chng 4 bn v cng ngh WiMAX vi hai phin bn c trin khai cho tinay: 802.16d v 802.16e.

Do khun kh lun vn c hn m cc lnh vc cp li qu rng ln v mi m, nn chngti khng dm bn su vo mt s kha cnh k thut nn tng trong cc cng ngh, v d nhnn tng l thuyt ca cc phng thc iu ch v m ha, chi tit v h thng bo hiu s 7(SS-7) vn vn cn c dng trong UMTS, chi tit v cc tng giao thc trong cc h thng

mng, v nguyn l chi tit ca OFDM v OFDMA, chi tit k thut ca truyn MIMO, v.v...Do kin thc cn hn ch, lun vn ny chc chn khng trnh khi nhiu thiu st. Xin cm

n thy Phm Thanh m tn tnh hng dn ti trong thi gian lm lun vn ny. Xin gili cm n n cc thy c Khoa Vin Thng 2 ging dy, cung cp kin thc v gip ng vin ti c th hon thnh c lun vn ny.

Xin cm n nhng ngi thn trong gia nh ti, cm n nhng ngi bn thn thit gip ti trong nhng lc kh khn nht.

Phm Hong Dng.


7/95



Chng 1:

S pht trin t 2G qua 3G ln 4G

Trong 15 nm va qua, truyn thng qua ng dy c nh v khng dy cng nh Internet pht trin c th ni l rt nhanh nhng cng c th ni l rt chm, ty theo ngi ta quan stlnh vc ny nh th no. nh gi khi qut v nhng s pht trin cho n hin ti v trongtng lai trong lnh vc ny, chng ny s cung cp mt ci nhn tng quan v nhng s kinchnh gip nh hnh ba lnh vc truyn thng ny trong mt thp k ri va qua. Tuy phn

ln nhng s pht trin m t di y din ra nhng nc cng ngh cao nht, nhngnhng yu t a phng v chnh sch iu chnh ca mi quc gia lm gim i hay tng lntc xy ra cc s kin y. V vy, khong thi gian c th c phn chia thnh mt sgiai on, v nhng mc thi gian c th s c cung cp ty theo mi quc gia c xt.

1.1. Na u thp k 1990: Vin thng ch yu l thoiMi lm nm trc, vo nm 1993, vic truy cp Internet cha ph bin rng khp, v hu

ht nhng ngi dng n u ang nghin cu hoc lm vic ti cc trng i hc hay trongmt vi cng ty chn lc trong ngnh IT. Vo lc , ton b cc trng i hc c ni ktvi Internet mt tc truyn l 9.6 Kbit/s. Nhiu ngi trong s h c my tnh ti nh ring,nhng vic quay s ni vo mng ca nh trng cha c p dng rng ri. Cc mng dinn chuyn (bulletin board) chng hn nh Fidonet3 c s dng rng ri bi lngngi dng t i online c vo lc .

V th, c th ni rng vin thng 15 nm trc ch yu ch l thoi, xt theo quan im thtrng i chng. Mt tp ch trc tuyn v vin thng cung cp mt s hnh nh th v v gic dch v vin thng vo lc , khi cc cng ty vin thng c quyn vn cn hin din huht cc nc chu u. V d, mt cuc gi ng di ni a 10 pht c trong gi lmvic, b tnh tin l 3,25 Euro (nhng vn cn r hn so vi gi c thoi ng di Vit Namvo lc ).

V pha truyn thng khng dy, cc mng tng t th h u lc c mt c vi

nm ri, nhng chi ph s dng chng t hn nhiu, v cc thit b di ng knh cng v c gikhng vi ti ni, tr cc nh doanh nghip. Vo nm 1992, cc mng GSM u tin ctrin khai mt s nc chu u, nhng ch mt s t ngi ch n cc mng ny.

1.2. T 1995 n 2000: s ct cnh ca vin thng di ng vInternet

Khong nm 1998, cc cng ty vin thng c quyn co chung nhiu nc chu u.Lc , nhiu nh cung cp dch v vn chun b t trc cho s kin ny nhanh chng nhy

3 FidoNet (www.fidonet.org) l mt mng my tnh ton cu, c dng lin lc gia cc h thng din

n chuyn (bulletin board system _ BBS) bng cc giao thc FTP v Telnet. N c nhiu ngi bit n nhtvo u nhng nm 1990, trc khi xut hin nhng kh nng truy cp d dng v phi chng vo Internet. Mngny n nay vn tip tc hot ng, nhng thu hp li kh nhiu, ch yu l do s ng ca ca nhiu BBS.


8/95



vo thay th, v gi c h xung nhanh chng trong vi tun l v vi thng u sau khi quinh mi (bi b vin thng c quyn) c hiu lc. Kt qu l, gi c ca cuc gi ng dini a 10 pht nhanh chng ri xung ch cn mt phn nh ca gi lc u. Xu hng ny nnay vn tip tc, v chi ph mt cuc gi nh th hin nay ch khong vi xu M. Hn na,nhng cuc gi ng di lin quc gia chu u v thm ch lin lc a n nhiu nc, nh

M v nhng nc cng nghip ha khc chng hn, cng c tnh vi gi tng t.Cng khong thi im , ngnh vin thng t n mt ct mc quan trng. Khong 5

nm sau khi cc mng di ng GSM u tin c trin khai, bng gi cc cuc gi in thoi ding cng nh gi c in thoi di ng t n mt mc khuyn khch c s chp nhnrng ri ca th trng i chng. Trong khi vo nhng nm u ca GSM, vic s dng inthoi di ng c coi l xa x v ch yu ch phc v nhu cu lm n ca cc doanh nhn, thvo cui thp k , vic chp nhn ca i chng tng ln n chng mt, v in thoi ding nhanh chng bin i t mt thit b gi cao dnh cho doanh nhn thnh mt cng ctruyn thng khng th thiu c i vi phn ln ngi dn cc nc tin tin.

Cng ngh truyn tn hiu s trn ng dy c nh cng pht trin mt mc nht

nh trong khong thi gian ny, v cc modem vi tc 3056 Kbit/s dn dn c chpnhn bi cc sinh vin v nhng ngi dng my tnh khc truy cp Internet thng qua trngi hc hoc thng qua cc nh cung cp dch v quay s Internet t nhn. Khong thi imny, truyn thng da trn vn bn cng bt u pht trin, v cc trnh duyt Web ua nhauxut hin, c th hin th c cc trang Web vi ni dung ha. Ngoi ra, e-mail cng vtqua ci mc tiu gio dc ban u ca n. Ni dung trn Internet vo lc ch yu c cng

b bi nhng hng thng tn ln v cc t chc IT, v rt ging mt m hnh phn phi t trnxung (top-down), trong ngi dng ch yu l ngi tiu th ch khng phi ngi cungcp thng tin. Ngy nay, m hnh ny c gi l Web 1.0.

Tuy cc cuc thoi qua cc mng di ng nhanh chng thnh cng, song truy cp Internet

di ng lc y vn ang l nhng bc i chp chng. Lc , cc mng GSM ch cho phptruyn d liu vi tc t 9.6 n 14.4 Kbit/s qua cc ng ni kt chuyn knh. Tuy nhinkhi y ch c mt s t ngi s dng d liu di ng, ch yu l do chi ph cao v thiu thn ccng dng v thit b. Tuy vy, cui thp k ngi ta thy nhng ng dng truyn d liudi ng u tin, chng hn nh cc trnh duyt Web v email di ng trn cc thit b nh PDA(Personal Digital Assistants) chng hn, vn c th truyn thng tin qua li vi cc in thoi ding thng qua cc cng hng ngoi.

1.3. T 2000 n 2005: Dot Com suy sp, xut hin Web 2.0v Mobile Internet

S pht trin vn tip tc v thm ch cn tng tc trong c ba lnh vc truyn thng ny, btchp s suy sp Dot Com (tc cc trang Web) vo nm 2001, vn lm cho c hai ngnh cngnghip vin thng v Internet ri vo mt giai on suy thoi trong vi nm. Mc cho thi knh n ny, c nhiu bc pht trin quan trng mi xy ra trong thi gian ny.

Mt trong nhng bc t ph chnh trong thi gian ny l s tri dy mnh m ca truy cpInternet thng qua DSL v cc modem truyn hnh cp. Nhng kiu truy cp ny nhanhchng thay th cc ng ni kt bng modem quay s bi v chng tr nn c gi c phi chngv cung cp nhng tc kt ni 1 MBit/s v cao hn. So snh vi nhng ng ni kt bngmodem quay s 56 Kbit/s, thi gian ti xung cc trang Web c ni dung ha v cc file ln c ci thin rt nhiu. Vo cui thi k ny, a s ngi dng nhiu quc gia c ckh nng truy cp Internet bng rng, cho php h xem c cc trang Web phc tp hn thnhiu. Ngoi ra, nhng dng truyn thng mi nh Blog v Wiki xut hin, nhanh chng cchmng ha s mt cn bng gia ngi to v ngi tiu th ni dung. t nhin, ngi dng


9/95



khng cn ch l ngi tiu th ni dung na m ng thi cng l ngi to ra ni dung choton th gii thng thc. y l mt trong nhng c im chnh ca ci c gi vi tnh chti chng l Web 2.0.

Trong th gii truyn thoi ng dy c nh, gi c cho cc cuc gi quc ni v quc ttip tc st gim. Vo cui khong thi gian ny, c nhng n lc u tin s dng Internet truyn i cc cuc thoi. Nhng ngi u tin chp nhn hnh thc ny khm ph ra cngdng ca Internet telephony v thc hin nhng cuc gi in thoi qua Internet thng qua ccng kt ni DSL hoc modem cp ca h. Nhng chng trnh c quyn nh Skype tnhin cho php ngi dng gi cho bt k thu bao Skype no trn th gii min ph, vi chtlng thoi cc tt trong nhiu trng hp. Tuy nhin, i vi chuyn ny th min ph l mtkhi nim tng i thi, bi v c hai bn tham gia cuc gi u phi tr tin truy cp Internet,nn cc nh cung cp dch v vin thng vn hng li t nhng cuc gi ny nh cc phhng thng cho cc mi ni kt DSL v modem cp. Thm vo , nhiu cng ty mi thnh lp bt u cung cp dch v thoi tng t cho cc hng chuyn i d liu thoi qua giao thcIP bng cch s dng giao thc SIP (Session Initiation Protocol) chun ha truyn ti cc

cuc thoi qua Internet. Cc thit b media gateway bo m rng nhng thu bao nh vy c thlin lc vi nhau qua cc s in thoi bng ng dy c nh thng thng, v c th gi nbt k in thoi tng t no trn th gii. Nhng hnh thc truyn thng ng di mi niny cng khin Internet c s dng mt cch tch cc truyn i nhng cuc thoi quc t,v v th gip cho chi ph thoi thp hn.

Nm 2001, dch v GPRS (General Packet Radio Service) ln u tin c a vo ccmng GSM cng cng. Khi nhng in thoi di ng c kh nng GPRS u tin nhanh chngxut hin sau , vic truy cp Internet di ng tr nn kh thi trong thc t i vi ng ongi dng hn. Trc , truy cp Internet di ng ch c th thc hin c thng qua nhngcuc gi d liu chuyn knh. Tuy nhin, tc truyn d liu, thi gian thit lp cuc gi, vvic nht thit phi duy tr knh truyn ngay c trong nhng qung thi gian khng tch cc cng

khng thch hp cho hu ht cc ng dng Internet. Nhng vn ny, cng vi nhng mnhnh hin th nh v n sc ca cc in thoi di ng v phn mm di ng trong thi k thu ny ca n khin cho nhng dch v Internet khng dy lc u (WAP 1.0) cha bao gi trnn ph bin. n nm 2005, cc thit b trng thnh hn, nhng mn hnh mu phngii cao c a vo cc in thoi di ng tm trung, v cc trnh duyt Web di ng WAP2.0 cng cc chng trnh khch e-mail di ng d dng kt hp vi GPRS thnh mt tng vnchuyn chuyn gi, cui cng cho php truy cp Internet di ng i vo th trng i chng.

Nhng cho d c nhng tin b ny, th nhng mc gi v cuc u tranh gia nhng khu vctruy cp m v ng (lt na s bn k hn) lm gim ng k s pht trin Internet di ng.

T y v sau, trong ti liu ny chng ti s dng cc thut ng truy cp di ng vo

Internet v truy cp Internet di ng thay v thut ng Internet di ng. l v thut ngsau khin ngi c lm tng rng c th c mt s phn bit gia Internet ng dy cnh v Internet di ng. Tuy ng l mt s dch v c ct may ring dng trn ccthit b in thoi di ng, thm ch cn hng li t v tn dng tnh di ng ca ngi dng,nhng xu hng chung l ngy cng c nhiu ng dng, dch v, v ni dung c cung cp vhu ch cho c cc thit b di ng nh nhn ln cc thit b cm tay ln hn hoc c nh.

Mt ct mc quan trng na i vi truy cp Internet khng dy trong khong thi gian nyl, cc mng 3G bt u c a vo hot ng nhiu nc vo cc nm 2004 v 2005.Trong khi GPRS c tc truyn gn vi modem quay s, th UMTS nng tc truyn dliu ln n 384 Kbit/s trong thc t, v s dng chng c v cng nhanh nh s dng DSL vy.

Nhng ch gi c ca cc nh cung cp dch v mng cng lm cho s chp nhn rng ri 3Gphi chm li vi nm.


10/95



1.4. T 2005 n nay: thoi di ng ph sng ton cu, VoIPv Mobile Broadband bt u ph bin

T 2005 n nay, t l dn chng cc nc cng nghip ha truy cp Internet thng qua ccng ni kt bng rng DSL hoc cp tip tc gia tng. Ngoi ra, nhiu nh cung cp dch

v mng bt u trin khai ADSL2+, v cc modem mi cho php tc ti xung vt qu15 Mbit/s i vi nhng ngi dng sng gn cc tng i. Nhng ng VDSL v cp quangtrin khai n trm phn phi hoc n tn nh thu bao cn cung cp nhng tc truyn lnhn na. K t nm 2005, mt hng pht trin khc ngy cng gia tng l Voice over IP (VoIP)thng qua mt cng in thoi trn router DSL hoc modem cp. iu ny ang lm cho mngin thoi tng t truyn thng i n ch co chung, v cc nh cung cp dch v thoi ngdy c nh nhn thy lng khch hng ca h ngy cng st gim.

Vo u nm 2009 ny, lng ngi dng in thoi di ng trn ton th gii t n 3 t.Th c ngha l gn nh c hai ngi trn a cu th c mt ngi s hu mt in thoi ding, mt mc pht trin m nm nm trc him c ai tin on c. Nm 2007, cc nh cung

cp dch v mng ng k mi pht 1000 thu bao mi. Phn ln s tng trng ny l nhs trin khai cc mng GSM/GPRS 2G v 2.5G cc th trng ang ni ln. Do s cnh tranhton cu gia cc nh cung cp, cc thnh phn thit b mng cng h n mc c th trin khaic cc mng khng dy nhng nc c mc thu nhp trn u ngi rt thp. Mt yu tquan trng khc ng gp vo s tng trng chng mt ny l s xut hin ngy cng nhiu ccin thoi di ng GSM gi cc r, khng n 50 USD. Ch trong vi nm, cc mng di ng thay i hnh thc hot ng v truy cp thng tin cho nhng nhng ch doanh nghip nh nhti x tc-xi v ngi bun bn nh cc th mi ni. Cc mng GSM gi y c mt hu htmi ni trn th gii.

cc nc cng nghip ha, cc mng 3G tip tc pht trin, v nm 2006 chng kin nhngcuc nng cp mng u tin t UMTS ln HSDPA (High Speed Data Packet Access). Thi gianu, iu ny cho php nng tc truyn d liu ca ngi dng ln n mc t 1 n 3Mbit/s. Vi cc thit b u cui di ng cao cp, tc chc chn cn cao hn na. Hin nay,nhng tc truyn cao nh vy ch yu ch c ch khi phi hp vi cc my tnh xch tay cungcp Internet bng rng cho ngi dng hu nh mi ni, nhng sau ny chc chn HSDPAcng s rt c ch cho nhng ng dng di ng mt khi vic ti xung cc file ghi m bi thuyttrnh (podcast), m nhc v phim nh trn cc thit b di ng tr thnh nhu cu ph bin caqun chng.

Hnh 1.1: T l doanh thu truyn d liu di ng ca vi hng dch v vin thng nm 2007.


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Tuy cc mng 3G xut hin vi nm ri, vic ngi dng chp nhn chng vn cn chmchp cho ti khong 2006/2007, khi cc nh cung cp dch v mng di ng cui cng mi ara nhng bng gi hp dn. Gi h xung 40 n 50 Euro hoc thp hn cho ph thu bao truycp Internet bng rng khng dy v dung lng ti hng thng khong chng 5 GBytes. Nhth l qu cho mi th ngoi tr chia s file qua mng v truyn ti phim nh s lng ln.

Cc nh cung cp cng bt u a ra nhng gi thu bao nh hn trong phm vi t 6 n 15Euro mt thng nu ngi dng thnh thong mi truy cp Internet bng my tnh xch tay. Hinnay c hng cung cp nhng gi vi gi tng t nh vy cho thu bao duyt Web v emailkhng gii hn trn in thoi di ng. Gi c v mc sn dng 3G hin nay vn khc bit tytheo quc gia. Vo nm 2006, doanh thu truyn d liu di ng ring M t n 15,7 t la, trong s 50 n 60 phn trm l doanh thu t cc dch v cao hn SMS. mt s nc,doanh thu truyn d liu di ng gi y chim khong 20 n 30 phn trm tng doanh thu canh cung cp dch v vin thng (xem Hnh 1.1).

Trong khi vic roaming d liu khng dy vn cn ang d dm nhng bc u tin, th nhiu nc kh nng truy cp Internet khng dy thng qua cc SIM card tr trc c cung

cp nhng mc gi tng ng vi gi dnh cho thu bao tr sau. y ng l mt bc tinquan trng khc, bi v n m ra cnh ca truy cp Internet bt k lc no v bt k u chonhng ngi dng sng to chng hn nh sinh vin, loi ngi thch dng SIM tr trc hn ltr sau hng thng. Ngoi ra, n khin nhng ngi thng xuyn i cng tc xa thy thun tinhn (nhng ngi ny trc y khng c kh nng truy cp Internet trn ng i tr khi cchotspot khng dy ti cc sn bay v khch sn).

1.5. Tng lai Nhu cu i vi cc h thng Sau 3GKhi nhn vo tng lai, cu hi chnh t ra cho cc nh cung cp dch v v cung cp thit b

mng l khi no v ti sao ngi dng cn n cc mng khng dy Sau 3G (Beyond 3G, vit ttl B3G). Mi my nm trc, in thoi l ng dng u tin c di ng ha. Vi nm sau th SMS (Short Message Service) tr thnh ng dng truyn d liu di ng u tin voc th trng i chng. n nay th nhng mng in thoi di ng n gin nht cng ckh nng truyn SMS do bi yu cu thp v bng thng ca n. C th xem SMS chnh l dchv tin phong ca nhng dch v truyn d liu khc nh e-mail di ng, duyt Web di ng,vit blog di ng, Push to Talk (PTT, tc dch v dng in thoi di ng nh my b m), tinnhn tc thi di ng, v nhiu dch v khc na. Nhng ng dng nh vy tr thnh hin thcl nh s xut hin cc mng khng dy truyn cc gi d liu theo giao thc IP v cc thit bdi ng ngy cng mnh m. n nay th dung lng ca cc mng 3G v 3.5G vn cho yucu v bandwidth ca cc ng dng ny v s lng ngi dng hin c. Nhng c th thyr l trong tng lai khng xa, mt s xu hng s lm tng yu cu v bandwidth:

Mc s dng mng khng dy ngy cng tng: do gi c ngy cng h, ngy cng cnhiu ngi s dng cc ng dng khng dy cn truy cp mng.

Ni dung a phng tin: tuy nhng n lc u tin di ng ha Web ch t c cctrang Web ch yu l vn bn, nhng ni dung ha ngy cng tr nn ph bin hn.Mt hnh nh c th ni thay cho hng nghn t ng, nhng n cng lm tng lng dliu cn c truyn i cho mi trang Web. Vic ti xung m nhc v phim nh cngang tr nn ph bin hn, lm tng hn na yu cu v bandwidth.

Cc mng x hi di ng: tng t nh trong Internet ng dy c nh, c mt dngng dng mi ang thay i cch thc con ngi s dng Internet. Trong qu kh, ngidng ch yu ch tiu th ni dung. Ngy nay th cc blog, podcast, cc site chia s hnhnh v cc cng truyn ti phim ang nh hnh li Internet, bi v ngi dng khng cnch tiu th ni dung na m nay dng mng chia s nhng tng, hnh nh v


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phim nh ca h vi ngi khc. V d, nhng ng dng nh Shozu v Lifeblog cho phpngi dng ti hnh nh, phim nh v cc bi vit blog t cc thit b di ng ln Web.Vic truyn hnh nh, podcast v phim nh s lm tng gp bi lng d liu m ngidng gi v nhn qua Internet.

Voice over IP: th gii thoi ng dy c nh ang nhanh chng chuyn sang hngVoIP. Nhiu kh nng l ch khong nm nm na, nhiu mng thoi chuyn knh ngdy c nh hin nay s chuyn hon ton sang truyn thoi da trn IP. Tng t nh vy,v phng din truy cp mng, nhiu ngi dng s s dng VoIP nh dch v thoi chnhca h, v d nh qua cc mng DSL hoc TV cp. Hin nay c th thy nhng ngthi chuyn dch ny ri, bi v th trng thoi chuyn knh ang chu p lc ngy cngtng do s st gim s lng thu bao. Kt qu l, nhiu nh cung cp dch v thoi ngdy c nh khng cn u t vo cng ngh chuyn knh na. C th quan st thy mtxu hng tng t trong cc mng khng dy. Tuy nhin, y s chuyn dch chm hnnhiu, c bit l do yu cu bandwidth cao hn truyn cc cuc thoi qua mt ngtruyn chuyn gi. Ch ny s c bn k hn trong mc 1.6.

S thay th cho ng dy c nh: trong khi lng thng thoi ngy cng tng thdoanh thu ngy cng gim c cc mng ng dy c nh ln khng dy do cc thu

bao ngy cng gim. V vy nhiu nc, cc nh cung cp dch v khng dy ang cgng km gi hoc tng doanh thu bnh qun trn mi thu bao bng cch cho mi khnng truy cp Internet cho my PC, my tnh xch tay v cc thit b di ng trn cc mngUMTS/HSDPA hoc CDMA ca h. Nh vy l h bt u cnh tranh trc tip vi ccnh cung cp dch v DSL v cp. Mun cnh tranh thnh cng, h cng phi tng thm

bng thng trn mng ca mnh.

S cnh tranh t nhng nh cung cp dch v Internet khng dy khc: mt s nc,cc nh cung cp dch v khc v ang cho mi kh nng truy cp Internet khng dy

broadband bng cc mng WiFi hoc WiMAX/802.16. Nhng nh cung cp dch v nhth cnh tranh trc tip vi cc nh cung cp dch v UMTS v CDMA truyn thng vnang hot ng trong th trng ny.

Internet bng rng khng phi ch c c thng qua nhng cm trn tng: ngynay, rt nhiu ngi dng cc thit b im truy cp (access point) WiFi xy dnglnh a Internet bng rng ca mnh. V vy, Internet bng rng hu nh lun baoquanh h. Trong tng li, ngi ta s khng ch dng nhng lnh a nh vy cho mytnh bn v xch tay, m cn cho cc thit b nh hn, nh in thoi di ng c sn khnng WiFi chng hn. Nhng thit b nh hn ny cng s thay i cch thc chng ta tipnhn nhng lnh a Internet nh th. Khng cn cn thit phi ngi mt ch ring bit,

nh trc my tnh chng hn, th mi truyn thng (bng VoIP, e-mail, nhn tin tc thi),ly thng tin xung t hoc gi thng tin ln Web (tranh nh, cc trang blog, phim nh,v.v..). Khi khu vn bng rng ca c nhn khng cn na, cc thit b di ng s chuynsang dng mng t ong. Trong tng lai, cc mng t ong s m rng ra c nhng khu vcm hin nay chng cha ph sng, v thng lng kh dng ca chng s tng ln png s lng ngi dng tng thm v s lng ng dng c ni kt thng qua chng.Vic chuyn qua chuyn li gia nhng lnh a Internet c nhn ti nh v mng t ongrng ln hn bn ngoi s tr nn v hnh (tc ngi dng s khng nhn ra s chuyndch ) khi cc dch v v thit b cho mng t ong pht trin thm.

Mt s cng ngh khng dy hin ang c xy dng hoc ang trong giai on trin khaiban u, c thit k p ng nhu cu tng lai ny: LTE (Long Term Evolution) ca 3GPP,

HSPA+ v WiMAX. Tt c cc cng ngh ny s c bn k hn trong Chng 2. Cu hi t


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ra l trong bi cnh nh vy, nhng cng ngh no l 3G hin nay, v cng ngh no c xeml 4G trong tng lai?

C quan chu trch nhim phn loi cc mng khng dy l ITU (InternationalTelecommunication Union). ITU phn loi cc mng vin thng di ng quc t (internationalmobile telecommunication _ IMT) nh sau:

Cc h thng IMT-2000: tc nhng h thng m ta gi l 3G hin nay, v d nh UMTSv CDMA2000. Danh sch tt c cc h thng ITU-2000 c lit k trong khuyn ngh ITU-R M.1457-6.

Cc h thng Enhanced IMT-2000: s pht trin ca cc h thng IMT-2000 (tc Sau 3G),v d nh HSPA, CDMA 1xEvDo v nhng th h pht trin hn na ca chng trong tnglai.

Cc h thng IMT-Advanced: cc h thng thuc loi ny c xem l h thng 4G.

Hin nay vn cha c nh ngha r rng no v cc c tnh ca cc h thng IMT-Advanced(4G) trong tng lai. Khuyn ngh ITU-R M.1645 cung cp mt vi gi u t in, nhng vn ng khi nim y:

It is predicted that potential new radio interface(s) will need to support data rates of up toapproximately 100 Mbit/s for high mobility such as mobile access and up to approximately 1 Gbit/s

for low mobility such as nomadic/local wireless access, by around the year 2010 [. . .] These datarate figures and the relationship to the degree of mobility [. . .] should be seen as targets forresearch and investigation of the basic technologies necessary to implement the framework. Future

system specifications and designs will be based on the results of the research and investigations.

Khi so snh vi cc c t hin nay ca WiMAX vi cc yu cu k thut ny, r rngWiMAX khng t cch c xem l mt chun 4G IMT-Advanced, bi v tc truyn

d liu ca n cn thp hn kh nhiu, ngay c trong nhng iu kin l tng (WiMAX c nhch c tc truyn d liu ti a l 70 Mbps, WiMAX di ng cn thp hn).

Chun hu du ca chun UMTS do 3GPP xy dng, gi l LTE, cng kh m p ngnhng yu cu ny. Ngay c trong mt h thng MIMO (Multiple Input Multiple Output) bn-ng-truyn, tc truyn d liu di tn sng mang 20 MHz cng khng th vt qu 326Mbit/s. (Ngay c con s ny cng c tnh kh nng ti a ri, bi v vic t bn ng-tenvo trong mt thit b nh hoc trn mi nh trong thc t khng h n gin).

C l cng nn so snh cc h thng 4G tng lai ny vi qu trnh pht trin ca cc hthng 3G hin nay. Qu trnh pht trin ca UMTS l mt v d tiu biu. Vi HSDPA vHSUPA, tc truyn ca ngi dng gi y vt mc d on lc u 2 Mbit/s dnh cho

cc h thng IMT-2000. Th nhng qu trnh pht trin ca cc h thng ny vn cha dng li.Nhng n bn chun mi xy dng Release 7 v 8 trong 3GPP c gi l HSPA+, vn bao gmc cng ngh MIMO v nhng cng ngh ci tin khc, cng a cng ngh UMTS ci tin nyn mt mc dung lng v bng thng nh ang c ch nh cho LTE trn di tn sng mang5 MHz. HSPA+ r rng cng khng phi l mt h thng 4G IMT-Advanced, bi v n ch citin v mt cng ngh v tuyn so vi cc h thng 3G IMT-2000 hin nay thi. V vy, HSPA+c xp loi l mt h thng IMT-2000 nng cao (Enhanced IMT-2000 system).

p ng nhng yu cu trng i ca IMT-Advanced, cc c quan son tho chunWiMAX v LTE bt u nhng n lc u tin ci tin hn na cc cng ngh ca h. V

pha WiMAX, nhm cng tc 802.16m ang tin hnh chun ha mt k thut giao tip v tuynnhanh hn trc. V pha LTE, mt chng trnh lm vic tng t c t tn l LTE+ hocEnhanced LTE cng bt u khi ng.


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Nhng nghin cu hin nay ch ra rng nhng yu cu v tc truyn c m t trongITU-R M.1645 ch c th t c di tn 100 MHz hoc hn na. y l mt thch thc thcs, xt theo quan im k thut cng nh do s thiu thn cc di tn cao ny. V vy, khngchc lm l nhng yu cu ny c cn c gi nguyn trong nh ngha cui cng v 4G IMT-Advanced hay khng.

Trong thc t, vi cng ngh mng khc nhau s cng c mt v pht trin trong tng lai p ng yu cu v mt bng thng v dung lng. Cng c th mt s kt hp cc h thng vtuyn khc nhau, nh LTE cng vi WiFi chng hn, s c dng tha mn yu cu v dunglng.

T quan im ngi dng v quan im dch v th cng ngh mng no c coi l 3.5G,3.9G hay 4G cng khng thnh vn . Cho nn ti liu ny dng thut ng cng ngh Sau 3Ghay B3G ch tt c cc cng ngh m c kh nng tha mn yu cu dung lng trong tnglai, bao gm cc cng ngh c xy dng mi hon ton cng nh pht trin t cc h thnghin ti.

1.6. Tt c cc h thng ny u da trn IPTuy v mt mng v tuyn (giao tip vi thu bao), kh on trc c tp hp nhng cng

ngh 4G hay 3G pht trin no s c dng trong tng lai, nhng tng lai ca cc mng lic nh v di ng li d tin on hn nhiu. Mt trong nhng c im chnh ca cc mng 3Gl vic hu thun cho c cc dch v chuyn knh ln cc dch v chuyn gi. Trong cc mng ding trc 3G, b phn chuyn knh ca mng li cng vi cc dch v chuyn knh ca mnggiao tip v tuyn c thit k chuyn vn chuyn cc cuc thoi (n thun ting cng nhc c hnh). Vic iu khin dch v ph thuc hon ton vo MSC (Mobile Switching Center),thnh phn chnh ca mt mng chuyn knh. Bi v cc thu bao c th chuyn vng (roaming)ty trong mt mng di ng, nn cn c mt c s d liu theo di v tr hin ti ca thu

bao cng vi thng tin v thu bao, l HLR (Home Location Register). thit lp mt cucgi, in thoi di ng phi lun lin lc vi MSC. Tip n, MSC s dng s in thoi ch tra vn HLR v v tr ca thu bao ch. Sau , cuc gi c gi chuyn tip n MSC ny, riMSC bo vi thu bao ch v cuc gi n. Qu trnh ny c gi l bo hiu (signaling). Mtng truyn chuyn knh (circuit-switched channel) c thit lp gia hai thu bao y thngqua ma trn chuyn mch (switching matrix) ca MSC, cn cc tn hiu bo hiu cn thit chocuc gi c truyn trn mt mng bo hiu c lp, bi v ng truyn chuyn knh kia chvn chuyn tn hiu thoi thi.

Trong nhng kiu thit k mng gn y, cc MSC c tch ra thnh hai thnh phn: mt lMSC Call Server chu trch nhim x l chuyn bo hiu, cn thnh phn kia l mt mediagateway, chu trch nhim gi chuyn tip cuc gi thoi, nh c minh ha trong Hnh 1.2.Thay v dng nhng knh ni c nh, cc media gateway s dng cc ng ni kt ATMchuyn gi hoc IP gi chuyn tip cuc gi. iu ny loi b s cn thit phi vn chuynd liu thoi qua cc ng truyn chuyn knh trong mng li.

Tuy cch gii quyt ny rt thch hp vn chuyn cc cuc gi thoi vi mt di tn cnh v nhng yu cu nghim ngt v tr, nhng n hot ng khng tt i vi vic truycp Internet. Trong Internet, tt c d liu u c vn chuyn trong cc gi d liu. Hn na,cc gi d liu ch c trao i gia hai thit b u cui (endpoint) khi c mt ng ni ktc thit lp, nhng ng ni kt ny hay thay i. V d tiu biu l mt phin duyt Web,trong mt ngi dng gh n vi trang Web, thm ch nhiu khi cng mt lc gh n nhiutrang. Khi mt trang Web c truyn i, n mun s dng cng nhiu thng lng hin c cng

tt ch khng phi b gii hn mt knh chuyn knh vn c thit k vn chuyn nhnglung d liu thoi hoc hnh s ha bng hp. Cc ng ni kt Internet nhiu khi cng chy


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khng ti (tc khng vn chuyn d liu g c) trong mt thi gian di. Trong thi gian ny, ttnht l ti nguyn mng nn trao cho nhng ngi dng khc. iu ny cng khng th thchin c i vi mt ng truyn chuyn knh, bi v khi c thit lp th n l mt knhdnh ring (exclusive channel), cung cp mt thng lng khng i gia hai bn tham gia, btk h c tm ngng ni gia cuc gi hay khng.

Hnh 1.2: H thng chuyn knh vi cc thnh phn mng x l nhng phn vic chuyn bit.

V nhng l do ny, cc mng 3G u cha mt thnh phn mng li ring gi chuyn tipcc gi d liu thay v chuyn knh, nh c minh ha trong Hnh 1.3. Mng giao tip v tuyn

phc v c mng chuyn knh v mng chuyn gi, v khi ngi dng di ng cn phc v thty theo h cn mt ng truyn chuyn knh hay mt ng truyn chuyn gi, mt kiung truyn thch hp s c thit lp qua khng trung. Mt s h thng mng, nh UMTSchng hn, cn cho php cc thit b dng ng thi cc ng truyn knh v gi, cho nnngi dng c th thc hin mt cuc gi trong khi ang kt ni Internet v ang truyn d liu.

Hnh 1.3: Kin trc i chuyn knh v chuyn gi tiu biu ca cc mng 3G. Thnh phnHLR khng c trnh by y.

Trong mng li, mi knhdnh ring vn chuyn mtcuc thoi hoc truyn d

Trong mng v tuyn, ccng truyn chuyn knhc dng cho cc cuc gi.D liu thoi v bo hiu khng


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Cc mng ng dy c nh truyn thng s dng mt kin trc phn i tng t nh vy ng thi thc hin c cuc gi thoi v truy cp Internet. T khi dch v DSL tr nn ph

bin, dch v thoi tng t v DSL s dng cng mt ng truyn vt l dn n nh khchhng. V th, ngi ta dng mt splitter phn tch tn hiu thoi analog khi tn hiu DSL, biv chng hot ng nhng di tn khc nhau. tng i, ngi ta dng mt splitter tng t

nh vy kt ni ng dy thu bao vi tng i chuyn knh chuyn tip cc cuc githoi v vi mt b tch knh truy cp DSL (DSL Access Multiplexer _ DSLAM) kt niInternet. Sau cc tng i in thoi c ni vi nhau thng qua cc ng truyn chuynknh, cn cc DSLAM th ni kt vi mt mng li chuyn gi. Tuy nhin sau khng lu,ngi ta cn ngh ra mt cch gii quyt khc hn vn chuyn cc cuc gi thoi qua ccng kt ni Internet. Thay v ni in thoi tng t vi splitter, thit b truy cp DSL ctrang b mt jack cm dnh cho in thoi. Thit b truy cp DSL s ha tn hiu thoi ri gi ni di dng cc gi IP qua ng dy DSL. Trong nhiu trng hp, ngi ta dng mt SIPServer da trn giao thc IP v RTP (Real Time Transport Protocol) thay cho tng i inthoi chuyn knh a phng. Cch gii quyt ny c vi u im:

Ch cn mt loi mng li duy nht, bi v cc tng i chuyn knh v mng chuyn knhgia gia chng khng cn cn thit na.

S dng mt mng IP truyn cc cuc gi thoi s gip cc cng ty cung cp dch vInternet no khng phi cng ty in thoi d cung cp cc dch v thoi hn, bi v b phniu khin mng khng cn cn phi c t ti tng i a phng na. Nh cung cp dchv c th kt hp cc dch v thoi vi cc dch v khc. Bi v khi ng truyn c thnglng ln hn, ngi dng c th s dng n cho mc ch khc, v d nh trao i nh vingi khc trong khi ang tham gia cuc thoi, hoc a thm phim nh vo mt thi imno trong khi tr chuyn.

Trong khi xu hng chuyn sang VoIP v ang din ra trong cc mng ng dy c nh,

th cc mng khng dy vn cha theo kp. y, mi s din ra chm hn nhiu v mt s ldo. L do chnh l cc mng di ng 3G khng c thng lng cn thit hu thun VoIP, vni hi mt tc truyn cao hn so vi cc cuc gi chuyn knh. S chnh lch ny gn y c gim thiu phn no bi vic trnh lng cc mng 3.5G, nhng ch cc mng Sau 3G(Enhanced IMT-2000 v IMT-Advanced) mi c thng lng v mt mng giao tip vtuyn c ti u ha hu thun VoIP quy m ln.


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18/95



2.2. UMTS

2.2.1. Gii thiu

Nhng phc tho u tin ca cc ti liu chun UMTS c gii thiu cho cc t cng tcca 3GPP vo cui nm 1999, nhng nhng cng trnh nghin cu kh thi v h thng ny

bt u sm hn nhiu. Mt vi mng UMTS c ra mt cng chng vo nm 2003, nhngmi ti cui nm 2004, khi cc in thoi di ng UMTS tha ng (v gi c v chc nng)c tung ra th trng v cc mng UMTS c trin khai ra nhiu thnh ph, th nhng ngichp nhn u tin mi kh nng v thc s s dng UMTS. Qu trnh t khi c b c tu tin cho n khi c nhng cuc trin khai u tin mt n nm nm, l iu khng bnhthng, v c l do tnh phc tp ca n. C l cng nn xem xt iu ny khi kho st nhngcng ngh mng mi ni ln nh LTE v WiMAX, vn cng ang giai on chuyn tip gialc chun ha v lc trin khai.

2.2.2. Kin trc mng

Hnh 2.1 cho thy mt ci nhn tng qut v kin trc ca mt mng UMTS. Pha trn bn trica hnh l thnh phn truy cp v tuyn ca mng, vn c cc chun ca 3GPP gi lUTRAN (UMTS Terrestrial Radio Access Network _ Mng truy nhp V tuyn Mt t caUMTS).

Hnh 2.1: Kin trc ca mng chung GSM/UMTS.

2.2.2.1. Trm c s (base station)

UTRAN bao gm hai thnh phn con: Base Station (trm c s) v Radio Network Controller(b iu khin mng v tuyn). Cc trm c s (c gi l NodeB trong cc ti liu v chun

ca 3GPP) nm ra ngoi ca mng, lin lc vi cc thit b di ng qua khng trung. ccthnh ph, mi trm c s thng ph sng mt vng(area) vi bn knh khong 1 Km, i khi


19/95



t hn, ty theo mt dn c v yu cu v thng lng. gia tng lng d liu v s lngcuc gi thoi ng thi trn mi trm c s, vng ph sng ca mi trm thng c chia rathnh hai hoc ba phn vng(sector), hoc (cell) nh c gi trong cc chun. Mi phnvng c ng-ten nh hng v thit b thu pht ca ring n. Nh vy, mt NodeB vi ba sector

bao gm ba cell ring r. Nu mt ngi dng i quanh mt trm c s nh vy trong thi gian

mt cuc thoi ang din ra hoc trong khi d liu ang c truyn ti, anh ta hoc ch ta s lnlt c phc v bi tng cell ca trm y. Trong sut thi gian y, mng v tuyn s chuyngiao (hand-over hoc hand-off) mi ni kt ca anh ta t cell ny sang cell k cn khi thy iukin tn hiu v tuyn xu i. Nh vy, v mt k thut th s chuyn giao gia cc cell ca cngmt trm c s c rt t s khc bit vi s chuyn giao gia cc cell ca cc trm c s khcnhau. Tnh hung ny v nhng tnh hung qun l tnh di ng khc s c bn k hn trongmc 2.2.3. H thng kt ni v tuyn gia cc thit b di ng v trm c s cn c gi l airinterface (tm dch: giao tip v tuyn4). Cc in thoi di ng, thit b u cui(terminal), hoc thit b di ng (theo cch gi thng thng) s dng mng UMTS c gil cc UE (User Equipment _ thit b ngi dng) hoc MS (Mobile Station _ Trm Di ng)trong chun ny.

Hin nay, cc trm c s UMTS c ni vi mng li thng qua mt hoc nhiu knh truynE1 (theo chun ca chu u) tc 2.048 Kbit/s v T1 (theo chun ca Bc M) tc 1.544Kbit/s. Mi knh truyn E1 hoc T1 lun l c mang trn mt cp ng cp ng vt l. Mtgii php thay cho cp ng l dng mt ng ni vi ba, vn c th mang vi knh E1 lun l.

Nhiu nh cung cp dch v UMTS thch dng cch hn, bi v h khng cn phi tr phthu bao hng thng cho ch ca h tng c s cp ng. s dng ht dung lng giao tip vtuyn ca mt trm c s UMTS nhiu cell, cn n vi knh E1. Giao thc c dng trnnhng knh truyn ny l ATM (Asynchronous Transfer Mode), mt cng ngh truyn ti mnhm, c s dng rng ri nhiu mng vin thng c nh cng nh khng dy khp th giihin nay. Hnh 2.2 minh ha mt t trm c s (base station cabinet) tiu biu t ti l ng.

Trong thc t, cc trm c s thng c lp t trn cc mi nh phng gn ng-ten, bi vnhiu khi khng c ch trng trn mt t, v bi v cch ny lm gim ng k chiu di (v vth, c chi ph) cho h thng cp ni gia t trm c s v ng-ten.

Khi cng ngh pht trin, vic dng cc knh E1 qua cp ng s tr nn kh khn hn bi vs lng ng cp dn n mt trm c s c gii hn thi, v quan trng hn na, tng slng cp th ph thu cp hng thng s cao. V th, cc nh cung cp dch v mng bt udng mt s cng ngh truyn thay th khc ni kt cc trm c s vo mng li:

4 Newtons Telecom Dictionary (20th Edition) nh ngha air interface nh sau:Air interface is a cellular

industry term. It refers to the system that ensures compatibility between equipment (cell phones) and the basestations. It involves the specification of channel frequencies and widths, modulation, power and power sensitivitylevels, and data framing. The system also selects which radio channels are employed during a call. Air interface isthe standard operating system of a mobile network. A four-layer protocol stack which ensures compatibility betweenterminal equipment and base stations, or hubs, through the development of a standard. In terms of the OSIReference Model, the layers include the Physical (PHY), the Media Access Control (MAC) layer, the Data LinkControl (DLC) layer, and the Network layer. The PHY layer specifies radio characteristics such as channelfrequencies and widths, modulation schemes, power and power sensitivity levels, and data framing. The MAC layer,which cuts across the PHY and DLC layers, specifies the procedures by which the wireless terminal and the basestation negotiate selection of the radio channel to be employed. The DLC layer specifies the manner in which theframes are sequenced, and the mechanism used to ensure their integrity during transmission. The Network layerspecifies the mechanism used to identify and authenticate the wireless terminal to the base station. Air interface are specified for technologies such as AMPS (Advanced Mobile Phone System), CDMA (Code Division Multiple

Access), DECT (Digital European Cordless Telecommunications), GSM (Global System for MobileCommunications), PCS (Personal Telecommunications Services), and PWT (Personal WirelessTelecommunications), and TDMA (Time Division Multiple Access).


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21/95



(thoi hay d liu), nhng yu cu v cht lng dch v, v nhng chn la thu bao cangi dng.

Qun l tnh di ng (mobility management) trong khi mt ng truyn ti v tuync thit lp, tc l kim sot s chuyn giao phc v gia cc cell khc nhau v cc trmc s khc nhau ca mng.

Kim sot qu ti (overload control) trong mng v trn ng truyn v tuyn. Trongnhng trng hp m s ngi dng mun truyn ti nhiu hn ti nguyn (s knh truynti, thng lng) kh dng, RNC c th chn li nhng yu cu thit lp knh truyn ti mi phng nga nhng knh c thit lp b suy yu hoc rt. Thay v vy, RNC cng cth gim thiu thng lng ca cc knh c thit lp. V d, c th mt yu cu lp knhtruyn d liu mi t mt thu bao no s b mng chn li nu ti trong cell bao quanhthu bao t n gii hn, nhng nu thu bao yu cu mt cuc thoi mi th mngc th gim thng lng trn mt knh d liu ang c cho php cuc thoi c thitlp. Trong thc t, vic chn s thit lp mt knh truyn d liu rt him khi xy ra, biv hu ht cc nh iu hnh mng u gim st cht vic s dng mng ca h v tho g

nhng ch tc nghn, v d nh bng cch lp t nhng b thu pht b sung mt trm cs, bng cch tng dung lng backhaul gia trm c s v RNC, hoc bng cch lp t cctrm c s b sung lm gim kch thc vng ph sng v v vy gim s lng ngidng ca mi trm.

2.2.2.3. Trung tm chuyn knh di ng (Mobile Switching Center _ MSC)

Nhn sang bn phi Hnh 2.1, ta c th thy rng cc RNC c ni vi cc nt cng ni(gateway) nm gia mng truy nhp v tuyn v mng li. Trong UMTS, c hai thc th mngli c lp vi nhau: mng li chuyn knh v mng li chuyn gi. Gc trn bn phi Hnh 2.1cho thy MSC, l n v trung ng ca mng li chuyn knh. N x l cc cuc gi thoi vhnh, ng thi ph trch vic gi chuyn tip cc tin nhn SMS thng qua mng v tuyn n

cc thu bao. Nh ni trong Chng 1, chuyn mch knh ngha l mt ng truyn dnhring c thit lp cho mi cuc gi gia hai thu bao thng qua MSC, v ng truyn nyc gi khng i trong khi cuc gi ang din ra. Cc mng di ng ln thng c viMSC, mi ci chu trch nhim mt khu vc a l khc nhau. Tt c cc RNC nm trong khuvc ca mt MSC c ni kt vi MSC . Mi MSC trong mng chu trch nhim v vicqun l tt c nhng ngi dng ca mng trong khu vc ca n v vic thit lp cc ngtruyn chuyn knh cho cc cuc gi n v i. Khi mt UE yu cu thit lp mt cuc thoi,RNC vng c thu bao gi chuyn tip yu cu y n MSC ni vi n. K n, MSC nykim tra xem ngi dng c c php thc hin mt cuc gi i khng, nu c th ra lnhcho RNC thit lp mt knh truyn ti v tuyn thch hp. Cng lc , n thng bo cho bnc gi v yu cu thit lp cuc gi ny hoc, nu bn c gi y nm mt khu vc khchoc mng khc, thit lp mt ng truyn chuyn knh n MSC ph trch khu vc hocmng . Nu bn gi trong cng mng vi bn c gi, UE ca h c th lin h thng viMSC ph trch bn c gi. Nhng trong nhiu trng hp, bn c gi khng trong cngmng hoc khng phi l mt thu bao di ng. Trong trng hp nh vy, mt ng truynchuyn knh s c thit lp vi mt GMSC (Gateway MSC _MSC Cng ni), c minh ha pha trn bn phi trong Hnh 2.1. Ty theo s in thoi ca bn c gi, GMSC ny s gichuyn tip cuc gi y n mt mng in thoi c nh hoc di ng bn ngoi. Trong thc t,cc thit b MSC thng phc v lun cc thu bao di ng v ng lun vai tr GMSC.

MSC qun l c cc thu bao v thng bo cho h v cc cuc gi n, cc UE phing k vi MSC khi chng c bt ln. Vo u qu trnh ng k, UE gi i IMSI

(International Mobile Subscriber Identity _ M s Nhn din Thu bao Quc t) ca n, vnc lu trn card SIM ca my, n MSC. Nu IMSI khng c sn trong c s d liu VLR


22/95



(Visitor Location Register) ca MSC t mt yu cu ng k trc , th MSC s tra cu c sd liu ngi dng chnh ca mng HLR (Home Location Register) bit thng tin thu bao(subscription information) v thng tin xc minh (authentication information) ca ngi dng.Thng tin xc minh c dng xc minh tnh hp l ca yu cu ng k v thit lp mtng truyn m ha trao i cc thng ip bo hiu. Sau , thng tin xc minh cng c

dng trong sut qu trnh thit lp mt cuc gi thoi hoc hnh m ha ng ting ca cucgi. Ch rng, s trao i cc thng ip ny khng da trn giao thc IP m da trn mtchng giao thc bo hiu ngoi bng gi l SS7 (Signaling System Number 7).Ngoi bng(out-of-band) ngha l cc thng ip c trao i trong ng truyn dnh ring cho bo hiu,khc vi ng truyn chuyn knh c dng vn chuyn d liu thoi v hnh.

2.2.2.4. Th SIM

Mt thnh phn quan trng trong cc mng UMTS, mc d n rt nh, l th SIM (SubscriberIdentity Module). N cho php vic thu bao mng tch ri vi UE, v vy ngi dng c thmua th SIM v UE ring bit vi nhau. Do , c th dng mt th SIM vi nhiu thit b, hocdng nhiu th SIM vi ch mt thit b. iu ny khuyn khch s cnh tranh gia cc nh cung

cp dch v mng, bi v ngi dng c th i t mng ny sang mng khc nhanh chng nugi c mng c khng cn cnh tranh na. Khi i ra nc ngoi, ngi dng cng c th mua vs dng mt th SIM tr trc ti ni n trnh phi tr ph roaming. Vic tch ri chuynthu bao mng khi cc UE cn c mt li ch na l, ngi dng khng cn bt buc phi muacc UE t mt nh cung cp dch v mng na, m cng c th mua t nhng ca hng c lp,v d nh cc ca hng in t v ca hng in thoi di ng m bn SIM thu bao cho vi nhcung cp dch v mng cng lc. iu ny kch thch s cnh tranh gi c cc thit b di ng,iu s khng xy ra nu ngi dng phi mua thit b t mt ngun cung cp duy nht.

2.2.2.5. Short Message Service Center (SMSC)

C mt dch v truyn d liu ph bin t lu trc khi xut hin cc cng ngh truy cp

Internet khng dy tc cao hin nay, l SMS(Short Messaging Service _dch v nhn tinngn), c dng gi cc thng ip vn bn gia cc ngi dng di ng vi nhau. Bi vdch v ny c t gia thp k 1990, nn n l mt phn khng th thiu ca mng li chuynknh GSM/UMTS. Cc thng ip vn bn SMS c vn chuyn theo kiu tr tm ri chuyntip (store and forward). Khi mt thu bao gi i mt thng ip vn bn, thng ip cgi qua knh bo hiu, vn c mc ch chnh l vn chuyn cc thng ip dnh cho vic thitlp cuc gi v qun l tnh di ng, n SMSC (Short Messaging Service Center _Trung tm

Dch v Nhn tin Ngn). SMSC lu tr thng ip ri tra vn c s d liu HLR tm xemMSC no hin ang ph trch thu bao ch. Sau , n gi chuyn tip thng ip , cngtrong mt knh truyn SS-7, n MSC kia. Khi nhn c thng ip vn bn , MSC kia nhv thu bao ch bng cch gi i mt thng ip nhn tin (paging message) ch khng phichnh thng ip vn bn . iu ny l cn thit, bi v trong nhiu trng hp, thu bao chtuy ni vo mng nhng khng phi ang trong trng thi tch cc (active) khi thng ip vn

bn gi ti n, v v th MSC khng bit cell no hin ang phc v thu bao . Trn giao tipv tuyn, tin nhn c gi i trn mt knh qung b (broadcast channel) m tt c cc thit bni vo mng u nghe thy c. V th UE ca thu bao ch c th nhn thng ip nhn tin v gi mt cu tr li n MSC mc d khng ang trong trng thi truyn thng tch cc vimng. Sau MSC xc minh thu bao y, kch hot ch m ha ri chuyn giao thng ipvn bn n ch. Trong trng hp thu bao ch khng tip cn c (unreachable, tc ngoivng ph sng hoc ang tt my), vic chuyn giao thng ip tm thi khng thc hin c,v SMSC s tm tr thng ip cho n khi li tip cn c thu bao y.


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2.2.2.6. Cc im kim sot dch v (Service Control Point _ SCP)

Cc thnh phn khng bt buc phi c, nhng rt quan trng, trong cc mng li chuynknh l cc c s d liu v h thng lun l kim sot tch hp trn cc SCP (Service ControlPoint _im kim sot dch v). V d nh, cn c mt SCP cung cp cc dch v thoi trtrc, vn cho php ngi dng np tin cho mt ti khon bng phiu tr tin trc ri s dnglng tin c trong ti khon thc hin cc cuc gi thoi v gi cc tin nhn SMS. ivi mi cuc gi thoi hoc SMS nh vy, MSC s yu cu s cho php t h thng lun lkim sot dch v tr trc trn mt SCP. Khi SCP y s kim tra v sa i s d trn tikhon ca ngi dng v cho php hoc t chi yu cu y. Cc MSC lin lc vi cc SCPthng qua cc knh bo hiu SS-7. Khi mt ngi dng tr trc di chuyn (roam) ra ncngoi, cc MSC nc ngoi cng cn lin lc vi SCP trong mng ni a ca ngi dng. Bil c nhiu nh ch to MSC, nn chun CAMEL (Customized Applications for MobileEnhanced Logic) qui nh mt m hnh v giao thc tng tc chung gia cc MSC v SCP.

cung cp dch v thc t, thng th cc MSC ch cn ni vi cc SCP bng cc knh bohiu. Tuy vy mt s dch v, nh dch v tr trc chng hn, cng i hi phi c mt h

thng giao tip cho php ngi dng kim tra d s ca h v np tin cho ti khon ca h.Trong thc t c vi kh nng thc hin h thng giao tip ny. Hu ht cc nh iu hnh mngs dng mt dng th co v mt h thng thoi t ng cho mc ch ny. V th, thng thcng cn c cc mch thoi gia cc cng thoi tng tc c kim sot ca SCP v cc MSC.

Ngoi ra, hu ht cc dch v tr trc cng cho php ngi dng np tin hoc kim tra s dti khon ca h thng qua cc m ngn (v d nh *100#); nh th khng cn thit lp mt cucgi thoi m ch cn gi cc m ngn n SCP thng qua mt knh bo hiu SS-7.

2.2.2.7 H thng tnh cc (billing)

Ngoi h thng tnh cc ca cc ngi dng tr trc, vn c thc hin tc thi trn ccSCP, mng li cn cn cc thit b khc na thu thp thng tin tnh cc t cc MSC dnh

cho cc thu bao tr sau. y l trch nhim ca cc server tnh cc (billing server), khngc minh ha trong Hnh 2.1. Thc cht, server tnh tin thu thp cc bn ghi chi tit cuc gi(Call Detail Records _ CDR) t cc MSC v SMSC trong mng ri lp ghp li thnh mt han tnh tin hng thng cho mi ngi dng cn c theo bng gi c chn. Cc bn ghi chitit cuc gi cha nhng thng tin chng hn nh m nhn din ca bn gi, m nhn din ca

bn c gi, ngy thng v thi gian ca cuc gi v m nhn din ca cell khi u cuc gi.Thng tin v v tr cng cn thit, bi v cc cuc gi c thit lp t cc mng nc ngoitrong khi ngi dng ang roaming c tnh cc khc vi cc cuc gi khi u t mng nia. Mt s nh cung cp dch v mng cng dng thng tin v tr cho vic tnh cc da theokhu vc (zone-based billing), tc l h a ra gi cc gi r hn cho ngi dng khi h nhhoc ti ni lm vic. Mt cch tnh cc ph bin khc na l tnh gi cc r hn vo nhngkhong thi gian nht nh. Hu ht cc nh cung cp dch v mng kt hp nhiu phng ntnh cc vo mt bng gi, v lin tc thay i cc phng n y. iu ny i hi mt dch vtnh cc da trn qui lut mm do, uyn chuyn.

2.2.2.8. Mng li chuyn gi

Cc thnh phn ca mng UMTS c cp t u ti gi c thit k cho truyn tichuyn knh. thng lung vi cc dch v trn Internet, vn da trn chuyn gi, mngUMTS cn mt phng thc tip cn khc. y l l do mt mng chuyn gi c b sungthm cho h tng mng li chuyn knh. Nh c th thy trong Hnh 2.1, RNC ni vi c mngli chuyn knh ln mng li chuyn gi. Thm ch, cc thit b UMTS c kh nng thit lp cc

ng truyn chuyn knh v chuyn gi cng mt lc. V th, ngi dng c th thit lp mtcuc gi thoi trong khi cng lc ang s dng thit b ca mnh nh mt modem cho my


24/95



PC, hoc ti xung nhng ni dung nh mt podcast chng hn v UE ca mnh, m khngcn ngt ng truyn vi Internet cuc gi thoi din ra. Mt li ch khc ca vic c nivi c mng chuyn knh ln mng chuyn gi l, cc phin nhn tin tc thi s khng b ngtkhi thit lp mt cuc gi thoi.

Trc khi mt UE c th trao i d liu vi mt mng chuyn gi bn ngoi nh Internet, nphi thc hin hai vic. u tin, UE cn ni (attach) vo mng li chuyn gi UMTS v thchin th tc xc minh. iu ny thng c thc hin sau khi UE bt ln v sau khi n ng k vi mng li chuyn knh. Sau , UE c th ngay lp tc, hoc vo mt thi imno sau ny, yu cu cp pht mt a ch IP t mng li chuyn gi. Qu trnh ny c gil thit lp mt cuc gi d liu (establishing a data call) hoc thit lp mt bi cnh PDP(establishing a Packet Data Protocol). Kiu ni thit lp mt cuc gi d liu tht ng ch ,

bi v n m ch rng vic thit lp mt ng truyn vi Internet hoc mt mng chuyn gikhc cng tng t nh vic thit lp mt cuc gi thoi vy. Xt theo quan im tn hiu th haihot ng ny thc s ging nhau. Tuy nhin, hai loi ng truyn c thit lp da trnhai yu cu rt khc nhau. Trong khi cc cuc gi thoi cn mt ng truyn c tr v thng

lng khng i, gi nguyn trong khi cuc gi din ra, th cc cuc gi d liu ch yu cuc mt ng ni kt vt l trong khi cc gi c truyn i. Trong nhng khong thi giankhng c d liu no c truyn, knh dnh cho ng ni kt hoc b sa i hoc b gii

phng hon ton, nhng ng truyn lun l ca cuc gi d liu y c gi nguyn victruyn d liu c th c tip tc bt k lc no. Hn na, a ch IP ca UE c gi khngi cho d khng c ti nguyn no c cp pht trn giao tip v tuyn. Trong UMTS, victch ri chuyn ni vi mng li chuyn gi khi chuyn thit lp mt ng truyn d liu c ngha khi nhn t kha cnh lch s v thc t. i a s cc thit b di ng hin nay ch yuc dng cho truyn thoi, vn khng cn ng truyn Internet no c. V th, cc thit b ding c th thc hin bn phn chnh ca n m khng cn thit lp mt cuc gi d liu noc. Nhng tt c cc loi mng di ng khc c bn trong chng ny ch da vo mt mng

li chuyn gi thi, v mng li chuyn gi ny cng c dng cho cc cuc gi thoi. Chonn, vic ni vi mng v vic yu cu cp pht mt a ch IP u l mt phn khng th thiuca cng mt th tc, v khi nim cuc gi d liu khng cn l mt phn ring ca thit kh thng na.

2.2.2.9. Serving GPRS Support Node (SGSN)

Mng li chuyn gi ca UMTS, ging nh mng li chuyn knh, cng c phng theoGSM vi ch mt vi sa i. y l l do khin nt cng ni ca mng li chuyn gi ni vimng truy nhp v tuyn vn c gi l SGSN (Serving GPRS Support Node). GPRS l dngvit tt ca General Packet Radio Service (dch v v tuyn truyn gi tng qut), v l ci tn

ban u ca dch v chuyn gi c trnh lng trong cc mng GSM. Ging nh MSC, SGSN

chu trch nhim qun l thu bao v tnh di ng ca h. cho php ngi dng di chuyngia cc vng ph sng ca cc RNC khc nhau, SGSN theo di v tr ca ngi dng v s thayi tuyn ng m cc gi IP gi n t mng li khi h thay i v tr. Cc SGSN c nivi cc RNC thng qua cc ng truyn ATM. Bi l cc RNC nhiu khi kim sot n hngtrm cell v kh xa mt SGSN, nn ngi ta dng cc knh cp quang ni gia chng vinhau. Trong thc t, mt RNC c ni vi mt SGSN thng qua mt hoc nhiu knh quangOC-3 vi tc mi knh l 155 Mbit/s (3 x 51.8 Mbit/s) hoc mt knh quang OC-12 vi tc 622 Mbit/s (12 x 51.8 Mbit/s). Bn trn tng ATM, IP c dng lm giao thc vn chuyn.

SGSN cng c mt ng bo hiu ni vi HLR ca mng, vn ngoi nhng d liu cn thitcho mng chuyn knh cn cha thng tin thu bao dnh cho mng chuyn gi. Thng tin ny

bao gm nhng th nh: ngi dng c php s dng cc dch v chuyn gi hay khng,nhng thit nh cht lng dch v ca h chng hn nh tc truyn ti a m mng cp cho


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h v cc im truy cp Internet no h c php dng. Thng tin ny cn cho thy ngi dngc mt hp ng tr trc hay khng, trong trng hp no SGSN phi lin h vi mt SCP trtrc ri mi cp pht mt ng kt ni m h yu cu.

2.2.2.10. Gateway GPRS Support Node (GGSN)

Ti bin ca mng li chuyn gi c cc GGSN (Gateway GPRS Support Node) ni kt mngli chuyn knh ca mng khng dy UMTS vi Internet. Mc ch chnh ca chng l che dutnh di ng ca ngi dng khi cc router trn Internet. iu ny l cn thit bi v cc IProuter gi chuyn tip cc gi da trn a ch IP ch v mt routing table. C mi gi gi n,mi router trn Internet u tra cu routing table ca n ri gi chuyn tip gi y n router ktip thng qua cng xut c ch nh trong routing table. Cui cng, cc gi d liu gi ncc thu bao khng dy UMTS s c a n GGSN. y, c ch routing khc hn. Bi lcc RNC v SGSN c th thay i bt k lc no do tnh di ng ca thu bao, cho nn mt cs d liu tnh cha bc nhy (hop) k tip da trn a ch IP nh routing table ca cc IProuter trn Internet l khng thch hp. Thay v vy, GGSN c mt bng c s d liu lit k ach IP ca SGSN no hin chu trch nhim i vi mt thu bao c a ch IP bit. Nh th

th, gi IP t Internet gi n thu bao s c GGSN a vo trong mt gi IP ri gi na ch ch l a ch ca SGSN y. Nguyn tc ny c gi l tunneling (tm dch: truyn

xuyn hm), bi v mi gi IP gi n thu bao u c gi trong mt gi IP khc gi nSGSN chu trch nhim phc v thu bao . Ti SGSN, gi IP ban u c khi phc li, vli c truyn xuyn hm n RNC, ri n UE ca thu bao. Chiu truyn ngc li, t thu

bao ra Internet, cng tng t nh vy.

Hnh 2.3: Vic truyn xuyn hm gi IP trong mt mng li chuyn gi.

Hnh 2.3 cho thy mt khu tunneling mt gi IP theo chiu t SGSN ra GGSN trong mngli truyn gi ca UMTS hot ng nh th no trong thc t. y mng ni gia SGSN vGGSN l mng Ethernet, nn chng giao thc l Ethernet tng 2 ri n IP tng 3. Ti myGGSN, khung Ethernet c tho ra, l gi IP c giao thc GPRS Tunneling Protocol

(GTP) bao bc. a ch ngun v ch ca gi IP bao bc l a ch ca my SGSN v GGSNca mng y. Tip n, phn mo u (header) ca gi IP bao bc y c tc ra ra c c


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gi IP gc. Sau , giao thc IP gi gi y ra Internet. Trong gi gc ny, a ch ngun v chl a ch ca my thu bao v mt host trn Internet (l mt Web server trong v d ny).

Ngoi vic truyn xuyn hm, GGSN cn chu trch nhim cp pht a ch IP cho cc thubao. Trong sut thi gian thit lp ng truyn, SGSN thm tra yu cu ca thu bao bngthng tin t HLR, ri yu cu cung cp mt a ch IP t qu a ch ca mng di ng, sau thit lp ng hm t SGSN sang GGSN. Trong thc t, c hai loi a ch IP. Nhiu nh cungcp dch v mng di ng s dng cc a ch IP ring t (private IP address), vn khng c gitr bn ngoi mng y. iu ny cng tng t nh vic dng cc a ch IP ring t trong ccmng ti gia, router DSL hoc cp cp pht cc a ch IP ring t cho tt c cc thit btrong mng ti gia. i vi th gii Internet bn ngoi, mng c i din bi mt a ch IPduy nht, v router DSL hoc cp phi dch (translate) cc a ch IP bn trong cng vi cc shiu cng TCP v UDP tng ng ra thnh cc a ch IP bn ngoi cng vi cc s hiu cngTCP v UDP mi. Qu trnh ny c gi l NAT (Network Address Translation _Dch a chMng). Nu cc a ch IP ring t c dng trong cc mng khng dy, qu trnh ging vycng c thc hin bi GGSN. Cc nh cung cp mng di ng p dng cch ny c hng

li l, h ch cn mt lng a ch IP cng cng (vn hin nay ngy cng cn kit) t hn slng thu bao nhiu. Nhng nh cung cp dch v mng khc th mc nh s dng cc a chIP cng cng cho cc thu bao ca mnh. i vi cc thu bao th y l mt li th, bi v h cth c cc my trn Internet tip cn trc tip, iu ny cn cho nhng ng dng nh hostingmt Web server hoc cc ng dng iu khin my tnh xa (remote desktop control). Tuynhin, cn lu rng c mt a ch IP cng cng cng c nhng bt li, c bit l i vi ccthit b di ng, bi v cc gi khng mong mun t Internet cng cng gi n c th nhanhchng lm cn pin ca n. Trong thc t, mt thu bao c th c vi bin dng(profile, tc tphp cc c im ring) ni kt, c gi l cc APN (Access Point Name). V th nh cung cpdch v mng c th chn nhng thu bao v ng dng no s dng a ch IP ring t hay cngcng.

2.2.2.11. Ni kt lin mng vi GSMGc di bn tri ca Hnh 2.1 minh ha mt mng v tuyn GSM, vn cng c ni kt

vi mng li chuyn knh v mng li chuyn gi ca UMTS. Ty theo nh cung cp dch vmng, mng v tuyn GSM c th c ni vi cng cc MSC v SGSN ca mng UMTShay vi cc MSC v SGSN ring. C th thc hin iu ny bi v chc nng ca cc thnh phnny rt tng t i vi GSM v UMTS. Tuy nhin, cc ng ni vi cc mng v tuyn 2G v3G th khc nhau. Trong ng truyn gia SGSN v mng truy nhp v tuyn 3G th ATMc dng lm giao thc vn chuyn cp thp, trong khi ng truyn gia SGSN v mng vtuyn 2G th da trn giao thc Frame Relay. Trong mt phin bn mi hn ca chun GSM,ngi ta cng ch nh dng mt ng truyn da trn IP gia SGSN v mng truy nhp v

tuyn 2G, tuy nhin n gi iu cha c p dng rng ri. Cc MSC th ni kt vi mngtruy nhp v tuyn GSM thng qua nhng ng truyn chuyn knh.

2.2.3. Giao tip v tuyn v mng truy nhp v tuyn

2.2.3.1. Nguyn l CDMA

Cc h thng v tuyn 2G nh GSM l da trn cc khe thi gian v cc knh truyn trnnhng tn s sng mang khc nhau (kt hp TDMA v FDMA), cho nn ch mt trm c s thicng c th phc v nhiu ngi dng ng thi. Tuy phng thc truyn ny rt thch hp truyn cc cuc thoi chuyn knh, nhng i vi truyn d liu chuyn gi th n khng mmdo uyn chuyn, bi v di tn ca knh GSM ch c 200 KHz, v v mi lc ch c th cp pht

c mt lng hn ch di tn cho mi ngi dng thi. V th i vi cc h thng 3G nhUMTS, ngi ta quyt nh dng mt phng thc truyn khc lm giao tip v tuyn. Mt


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cng ngh truyn thay th khc phc nhng hn ch ca mt di tn hp v c hiu rvo cui nhng nm 1990, khi cng trnh xy dng chun UMTS bt u, l CDMA (CodeDivision Multiple Access). Thay v dng di tn knh hp 200 KHz nh trong GSM, cc knhW-CDMA (Wideband CDMA) c dng trong UMTS c di tn n 5 MHz. Hn na, thay vcp pht cc khe thi gian, tt c ngi dng lin lc vi trm thu pht cng mt lc nhng s

dng mt m khc nhau. Cc m ny cn c gi l m tri (spreading code), bi v mi bitc biu din trn giao tip v tuyn bi mt t m(codeword). Mi n v nh phn ca t mc gi l mt chip ( phn bit r vi bit). c c tc truyn 384 kbit/s, mi bit cm ha thnh tm chip, nh vy di ca m tri l 8. Cc m c dng bi nhng ngidng khc nhau truyn ng thi phi trc giao v mt ton hc vi nhau. Trm c s c th

phn bit cc cuc truyn ng thi t cc UE bng cch p dng gii thut ngc li vi giithut c dng trong cc UE, nh c minh ha trong Hnh 2.4, v nh bit cc m cdng bi mi UE.

thch nghi c vi nhng yu cu thng lng khc bit ca nhng ngi dng khcnhau, h thng c th dng vi di m tri khc nhau cng mt lc. i vi cc cuc gi

thoi, vn ch cn tc truyn 12.2 Kbit/s, UMTS s dng di m tri l 128. Th c nghal mi bit c biu din trn giao tip v tuyn bi 128 chip, v n 128 ngi dng c th gicc dng d liu thoi ca h ng thi trong iu kin l tng. Trong thc t, s lng cucgi thoi ng thi cho mi cell nh hn do s can nhiu t cc cell k cn v nhng li truyndo nhng iu kin truyn tn hiu khng l tng. V th, nu mun 128 cuc truyn ng thi,cn c mt t l tn hiu trn nhiu (signal-to-noise _ S/N) cao hn. Hn na, mt s m c dnh cho cc knh thng tin h thng qung b gi n tt c cc thit b trong cell, nh s c

bn chi tit hn bn di. Trong thc t, ngi ta c lng rng mi cell UMTS c th dungcha n 60 cuc gi ng thi, loi tr s thu bao ang s dng cell truy cp Internetchuyn gi.

Hnh 2.4: Cc dng d liu truyn ng thi ca hai ngi dng n cng mt trm c s.

tng tc truyn d liu ca UMTS vt qu 384 kbit/s, ngi ta xy dng cc chunHSPA v HSPA+. Cc chun ny cho php mi UE s dng ng thi nhiu m tri, ngoi

nhng im tng cng khc. iu ny s c bn chi tit hn trong cc mc bn di.


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2.2.3.2. Kin trc knh v tuyn UMTS

Trong cc mng Ethernet c dy thng c dng trong cc mi trng ti gia v doanhnghip hin nay, vic nhn ra mng ri gi cc gi qua n l iu n gin i vi cc thit b.

Ngay khi cp mng c cm vo, card mng hiu ngay cch thc truyn cc gi qua ng cp,v cng bt u truyn ngay khi n nhn ra khng c thit b no khc ang gi d liu i c.

Nhng trong cc mng khng dy, mi chuyn phc tp hn. Trc ht, mi ni thng c vimng cng hin din mt lc, cho nn thit b cn ly thng tin v vic mng no thuc nh cungcp dch v mng no. Ngoi ra, cc thit b cn nhn ra cc cell k cn c th nhanh chng

phn ng vi vic thay i mc tn hiu khi ngi dng di chuyn. Bi v vic gi cho b thum ln sut ngy sut m rt khng hiu qu v mt tiu th in nng, cho nn cng cn csn mt c ch cho php thit b ngt in i trong nhng lc c rt t hoc khng c d liu noc truyn i, v ch nh k thc dy kim tra xem c d liu mi hay khng. i vi cccuc gi thoi, cn mt iu quan trng hn na l bo m mt mc cht lng dch v no ngn khng cho mng b rt trong nhng trng hp qu ti. V nhng l do ny, ngtruyn v tuyn ca UMTS c phn ra thnh mt s knh tn s ring. Vic truy cp v cc

knh tn s ny c kim sot bi mng, v thu bao c th b mng t chi cung cp knh tns trong trng hp qu ti.

2.2.3.2.1. Mt phng ngi dng v mt phng iu khin

GSM, UMTS, v nhng h thng truyn thng khng dy khc phn bit hai loi dng d liutruyn trong mng. Trong UMTS, cc dng d liu ny c phn chia thnh hai mt phng(plane) khc nhau: mt phng ngi dng (user plane) v mt phng iu khin (control plane).D liu chy trong mt phng ngi dng l loi d liu c trao i trc tip v d hiu giangi dng v mng, nh d liu thoi v cc gi IP chng hn. Mt phng iu khin th chutrch nhim v tt c d liu bo hiu trao i gia ngi dng v mng. Nh vy, mt phngiu khin c dng cho d liu bo hiu v trao i cc thng ip thit lp cuc gi

hoc cc thng ip cp nht v tr chng hn. Hnh 2.5 cho thy vic phn chia mt phng ngidng vi mt phng iu khin, cng nh mt s v d v cc giao thc c dng trong cc mtphng .

Hnh 2.5: Mt phng ngi dng v mt phng iu khin.


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2.2.3.2.2. Knh lun l, knh vn chuyn, v knh vt l

phn bit cc c tnh vt l ca giao tip v tuyn vi ng truyn lun l, thit kUMTS a ra ba tng knh truyn khc nhau. Hnh 2.6 cho thy cc knh nhng tng khcnhau hng xung, cn trong Hnh 2.7 l cc knh nhng tng khc nhau hng ln.

Cc knh lun l: tng knh trn cng c hnh thnh bi cc knh lun l. Cc knh nyc dng phn bit nhng loi dng d liu no phi c truyn qua giao tip v tuyn,chng khng cha thng tin g v cch truyn d liu c. Chun UMTS qui nh cc knh lun lsau:

Knh iu khin qung b BCCH (Broadcast Control CHannel): knh ny c tt c ccUE trng thi Idle theo di nhm nhn c thng tin h thng tng qut t mng. Thngtin c phn phi qua knh ny bao gm nhng th nh cch thc truy nhp mng, nhngm no c dng bi cc cell k cn, LAC (Location Area Code), m nhn din cell, vnhiu thng s khc. Cc thng s ny c nhm vo cc thng ip khi thng tin h thng(System Information Block _ SIB) gip UE gii m nhng thng tin y v tit kimthng lng ca giao tip v tuyn.

Hnh 2.6: Cc knh lun l, vn chuyn, v vt l hng xung.

Hnh 2.7: Cc knh lun l, vn chuyn, v vt l hng ln.

Knh iu khin nhn tin PCCH (Paging Control CHannel): knh ny c dng thngbo vi ngi dng l c cc cuc gi hoc thng ip SMS gi ti hay khng. Cc thngip nhn tin cng c dng cho cc cuc gi chuyn gi l c d liu n t mng haykhng sau khi tt c cc knh vt l dnh cho mt UE c gii phng do thi gian thng (inactive) ca n di. Nu UE nhn c mt thng ip nhn tin, trc ht n phi

bo co thng tin ca cell no ang phc v n v cho mng. Sau mng s thit lp li mtng truyn RRC lun l (s gii thch mc 2.2.3.3. bn di) vi UE, ri nhng d liui trong mng mi c phn phi n UE.

Knh iu khin chung CCCH (Common Control CHannel): knh ny c dng cho ttc cc thng ip gi t v n tng UE (hai chiu) no mun thit lp mt ng truyn mi

CCCH DTCH DCCH

RACH DCH

PRACH DPDCH DPCCH


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vi mng. iu ny l cn thit nhng lc nh ngi dng mun thc hin mt cuc githoi, gi mt thng ip SMS, hoc thit lp mt knh truyn d liu chuyn gi.

Knh iu khin dnh ring DCCH (Dedicated Control CHannel): trong khi ba loi knhni trn l cc knh chung, c nhiu UE trong cell quan st cng lc, th knh DCCH chvn chuyn d liu cho mt UE duy nht thi. Mi knh DCCH c dng cho nhng vicchng hn nh vn chuyn cc thng tin qun l tnh di ng (Mobility Management _MM) v cc giao thc iu khin cuc gi (Call Control _ CC) i vi cc dch v chuynknh, cc thng ip qun l tnh di ng gi (Packet Mobility Management _ PMM) v qunl phin (Session Management _ SM) i vi cc dch v chuyn gi gi t v n MSC vSGSN.

Knh vn chuyn d liu dnh ring DTCH (Dedicated Traffic CHannel): knh ny cdng truyn d liu ngi dng gia mng v mt ngi dng duy nht. D liu ngidng c th l nhng th nh mt tn hiu thoi s ha hoc cc gi IP ca mt ng truynchuyn gi. Nu mt knh DTCH truyn mt cuc gi thoi, n bt buc phi nh x (map)knh ny ln mt knh vt l dnh ring no . Nhng nu knh DTCH truyn d liu

ca mt ng truyn chuyn gi th n cng c th c nh x ln mt knh vt l chung(common) hoc dng chung (shared). V vy, nh c th thy trong Hnh 2.6, mt DTCH cth c nh x khng ch ln mt knh vn chuyn v vt l dnh ring m cn ln mt knhvt l chung hoc dng chung na.

Ghi ch: Trong UMTS Release 99, hu ht cc ng truyn chuyn gi IP s lun lunc vn chuyn qua mt knh vt l dnh ring. Bng cch ny, tc truyn d liu dnhcho tng ngi dng c th t n 384 Kbit/s hng xung. Cc knh vt l chung/dngchung (v d nh knh FACH c gii thiu bn di) ch c dng nu ngi dng thng mt thi gian di, hoc nu ngi dng ch thnh thong mi gi hoc nhn nhnglng d liu nh.

Knh vn chuyn d liu chung CTCH (Common Traffic CHannel): knh ny c dngcho thng tin qung b trong cell. Trong GSM, c ch nhu vy cng c dng, v d nh

bi Vodafone c, thng bo cho nhng thu bao ca cc mng ng dy in thoi cnh v cc m khu vc no c dng trong phm vi cell hin ti c th c gi t inthoi di ng c bng gi cc r hn.

Cc knh vn chuyn: cc knh tng gia ny chun b cc khung d liu (frame) hngxung truyn qua giao tip v tuyn bng cch phn chia chng ra thnh cc phn nh hn,c bao bc vo trong cc khung RLC/MAC thch hp hn truyn qua giao tip v tuyn.Phn mo u RLC/MAC, vn c t trc mi khung, cha nhng thng tin quan trngsau y (ngoi nhng th khc ra):

Chiu di ca khung (10, 20, 40, hoc 80 ms);

Kiu c ch kim tra tnh ton vn (CRC checksum);

Dng thc m ha knh pht hin li (error detection) v sa li (error correction);

Cch iu chnh tc cho khp (rate matching) nu tc ca knh vt l v cc tngbn trn khng khp;

Thng tin iu khin pht hin truyn khng lin tc (Discontinuous Transmission _DTX) nu u bn kia khng c d liu no gi trong mt thi gian nht nh.

Tt c cc c tnh ny c kt hp vo trong ci gi l dng thc vn chuyn (transport

format). Tuy nhin vic m ha knh trong thc t ch c thc hin trn tng vt l ca Node-


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B. iu ny rt quan trng, bi v vic m ha knh bao gm c vic b sung cc bit pht hinli v sa li vo dng d liu, vn c th l mt lng ph ph (overhead) khng l.

Cc knh lun l c nh x ln nhng knh vn chuyn sau y:

Knh qung b BCH (Broadcast CHannel): l phin bn knh vn chuyn ca knh lun l

BCCH. Knh dnh ring DCH (Dedicated CHannel): knh vn chuyn ny kt hp d liu t ccknh lun l DTCH v DCCH. Knh ny c mt trong c hng ln ln hng xung, bi vd liu c trao i theo c hai chiu.

Knh nhn tin PCH (Paging CHannel): l phin bn knh vn chuyn ca knh lun lPCCH.

Knh truy cp ty RACH (Random Access CHannel): l phin bn knh vn chuyn caknh lun l hai chiu CCCH theo hng ln. Knh ny c cc UE dng gi cc thngip yu cu ng truyn RRC n mng nu chng mun thit lp mt ng truyn dnhring vi mng (v d nh thit lp mt cuc gi thoi). Ngoi ra, knh ny cn c cc UEdng gi d liu gi ca ngi dng ( trng thi Cell-FACH, xem mc 2.2.3.3. bn di)nu khng c knh dnh ring DCH no c thit lp gia UE v mng. Tuy nhin, cn lu rng knh ny ch thch hp cho nhng lng d liu nh m thi.

Knh truy cp chuyn tip FACH (Forward Access CHannel): knh ny c mng dng gi cc thng ip thit lp ng truyn RRC n cc UE no bo qua knh RACHrng chng mun thit lp mt ng truyn vi mng. Thng ip ny cha nhng thng tin

bo cho UE v cch truy nhp mng. Nu mng va cp pht mt knh dnh ring, thng ipny s cha nhng thng tin nh m tri no s c dng hng ln v hng xung.Knh FACH ny cng c th c mng dng gi d liu ngi dng cho UE nu khngc knh dnh ring DCH no c cp pht cho mt cuc truyn d liu. Khi UE trong

trng thi Cell-FACH, nh c m t trong mc 2.2.3.3. bn di. hng ln, d liuc truyn qua knh RACH.

Cc knh vt l: cc knh tng di cng ny chu trch nhim cung cp mt phng tintruyn vt l cho mt hoc nhiu knh vn chuyn. Chng cng chu trch nhim m ha knh,tc b sung cc bit d phng v pht hin li vo dng d liu.

Chun cng xut nhng sn phm trung gian gia knh vn chuyn v knh vt l, gi lknh vn chuyn m ha hn hp (Composite Coded Transport CHannel _ CCTrCH), v l skt hp ca vi knh vn chuyn vi mt hoc nhiu knh vt l. Bc trung gian ny c xut bi v khng ch c th nh x vi knh vn chuyn ln mt knh vt l duy nht (v d nhknh PCH v FACH ln knh S-CCPCH) m cn c th nh x vi knh vt l ln mt knh vnchuyn duy nht (v d nh knh DPDCH v DPCCH ln knh DCH).

Trong cc mng UMTS, mt knh vt l c biu din bi mt m tri nht nh. Danh schsau y cung cp mt ci nhn tng th v nhng knh vt l quan trng nht theo hng tixung (downlink, tc t mng n UE) v hng ti ln (uplink, tc t UE n mng). Tt ccc knh vt l ny u c truyn ng thi:

P-CCPCH (Primary Common Control Physical CHannel): knh vt l iu khin chungchnh, truyn ti knh iu khin qung b lun l, vn c gim st bi tt c cc UE trongkhi chng khng c mt mi ni kt tch cc no c thit lp vi mng. Thng tin c

pht tn thng qua knh ny bao gm m s nhn din cell, cch thc truy cp mng, nhngm tri no c dng cho cc knh khc trong cell, nhng m no c dng cho cc cell kcn, cc b nh thi truy cp mng, v.v....


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S-CCPCH (Secondary Common Control Physical CHannel): knh vt l iu khin chungph, phc v vi mc ch, v v vy mang mt s knh lun l khc nhau. Trc ht, ntruyn ti cc thng ip nhn tin m mng bo cho cc UE gi cc cuc gi ti, cc tinnhn SMS, hoc khi cc gi d liu tip tc n sau mt thi gian di trm lng (th ng).Knh ny cng c dng phn phi cc gi IP v cc thng ip iu khin n cc thit

b, tc ch giao nhn nhng lng d liu nh vo mt thi im c bit, v v vy khngcn phi t thit b vo mt trng thi tch cc hn.

PRACH (Physical Random Access CHannel): knh vt l truy cp ty , ch c hngln v l knh duy nht m cc UE c php dng truyn m khng cn s cho phptrc ca mng. Mc ch ca n l cho php UE yu cu thit lp mt ng truyn thchin mt cuc gi thoi, phn ng li mt thng ip nhn tin, hoc gi i mt thngip SMS. Nu mt cuc gi thoi c thit lp ri v UE ch gi hoc nhn mt lngd liu nh thi, knh ny cng c th c dng kt hp vi knh S-CCPCH gi cc giIP hng xung. Tuy nhin, tc truyn theo c hai chiu ca n rt thp v thi gian khhi (round trip delay time) ln (khong chng 200 ms). V vy mng thng cp pht nhng

knh vt l khc, chuyn dnh cho nhng cuc truyn d liu chuyn gi ngay khi n nhn rahot ng mng c hi phc t mt UE no .

DPDCH v DPCCH (Dedicated Physical Data CHannel v Dedicated Physical ControlCHannel): sau khi mt UE lin lc c vi mng thng qua knh truy cp ty PRACH,mng thng quyt nh thit lp mt ng lin lc y vi UE . Trong trng hpmt cuc gi thoi, mng s cp pht mt knh dnh ring. Trn giao tip v tuyn, knh s dng mt m tri dnh ring, c cp pht bi mng. Lc trc, cc mng UMTS cngdng cc knh dnh ring truyn d liu chuyn gi, nhng hin nay tc ca nhngknh nh vy (cn c gi l knh truyn ti _ bearer) b gii hn mc 384 Kbit/s. Chmt s t ngi dng c th nhn cng lc mt knh nh vy trong mt cell. Mt nhc imkhc ca vic dng mt knh dnh ring cho cc ng truyn chuyn gi l, mng phithng xuyn cp pht li cc m tri cho nhng ngi dng khc nhau. iu ny l cn thit,

bi v hu ht cc cuc truyn chuyn gi thng truyn d liu dn dp, v v th ch yucu mt knh truyn thng lng cao trong mt thi gian gii hn thi. dng li m tricho nhng ngi dng khc, mng cn thay i di m tri ca mt knh d liu dnhring ngay khi n khng c dng y na, hay thm ch nh x ng truyn ang sdng knh ring y vo mt knh iu khin chung (P-CCPCH hoc S-CCPCH) cp phtti nguyn ca knh ring y cho nhng ngi dng khc. Trong thc t, iu ny to ra mt

ph ph bo hiu (signaling overhead) cao m ngi dng li thy tc truyn khng cao. Vvy, ngi ta quyt nh rng cn mt phng thc ci tin, cung cp nhng tc truyncao hn v mm do uyn chuyn hn cho nhng cuc truyn d liu dn dp. Kt qu ca

qu trnh ci tin ny ngy nay c gi l HSPA (High-Speed Packet Access), m nhiungi cn gi l 3.5G. Chun ny s c bn trong mc 2.3.

2.2.3.3. Cc trng thi RRC (Radio Resource Control)

tit kim in v ch cp pht ti nguyn cho cc UE khi cn thit, mt knh vt l nin vi RNC ca mng c th i vo mt trong cc trng thi kim sot ti nguyn v tuyn(Radio Resource Control _ RRC) nh sau:

Trng thi ri (Idle): trong trng thi ny, cc thit b khng truyn thng tch cc vimng. y, chng ch nh k lng nghe knh nhn tin bit c cc cuc gi thoi hochnh v cc tin nhn SMS gi ti hay khng.

Trng thi Cell-FACH: nu mt UE no mun lin h vi mng, n chuyn t trngthi Idle sang trng thi Cell-FACH (Cell-Forward Access Channel). trng thi ny, UE


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gi cc thng ip iu khin ca n qua knh truy cp ty PRACH v mng, v mng trli bng knh truy cp chuyn tip FACH, vn c gi qua knh vt l S-CCPCH m t trn. Yu cu v in nng cng tng ln, bi v gi y UE cn gim st hng xung xem c thng ip iu khin no gi n hay khng.

Trng thi Cell-DCH: sau khi mng quyt nh thit lp mt ng truyn thoi hoc dliu, UE c hng dn s dng mt knh dnh ring, v v th n chuyn sang trng thiCell-DCH (Cell Dedicated CHannel). Nu thit b c kh nng HSPA, th mng s chnmt knh dng chung(shared channel) cho n thay v knh dnh ring, nh s c bn chitit hn bn di. Tuy nhin, xt theo quan im kim sot ti nguyn v tuyn th thit b vn c xem l ang trng thi Cell-DCH. Thi gian tr kh hi trng thi Cell-DCH lt 160 ms vi mt knh truyn dnh ring UMTS cho n 120 ms vi mt knh truynHSPA. Trong trng hp mt knh d liu chuyn gi, mng c th quyt nh chuyn thit

b tr li trng thi Cell-FACH nu tnh tch cc ca n, tc lng d liu c truyn i,gim thiu. Sau khi tnh tnh cc li tng ln, mng s chuyn knh truyn v li trng thiCell-DCH. i vi nhng khong thi gian th ng di hn trong phin truyn d liu ,

mng thm ch c th quyt nh t UE v li trng thi Idle gim tiu th in nngca UE gim ti x l qun l cho mng. Cho d trng thi Idle, UE vn c th tip tcli vic gi cc gi IP vo bt k lc no thng qua knh PRACH. Tuy nhin, c mt trng ch khi chuyn n mt trng thi tch cc hn. Ty theo nh sn xut mng v tuyn,thi gian kh hi ban u c th t 2 n 4 giy.

Cc trng thi Cell-PCH v URA-PCH: ngay c khi trng thi Cell-FACH, UE vn ihi mt lng in nng ng k lng nghe knh truy cp chuyn tip RACH mc cho tnhtch cc ti tiu ca n. Do tr ng k khi t trng thi Idle chuyn sang tip tc truyn dliu, nn c hai trng thi na c ch nh, nm gia trng thi Idle v trng thi Cell-FACH, l Cell-PCH v URA-PCH. Trong cc trng thi ny, UE ch cn nh k lngnghe knh thng ip nhn tin thi, trong khi knh lun l gia mng v tuyn v UE vnc gi nguyn. Nu knh tch cc tr li, ng truyn c th nhanh chng c tiptc. S khc bit gia hai trng thi ny l, trng thi Cell-PCH UE phi bo co nhngthay i ca cell cho mng, bi v thng ip nhn tin ch c gi ti mt cell m thi, cnkhi trng thi URA-PCH th UE c th di chuyn (roam) gia vi cell thuc cng mt khuvc routing m khng cn bo co s thay i cell cho mng, bi v thng ip nhn tin cgi n tt c cc cell thuc khu vc routing . Tuy nhin, trong thc t ch c mt t nhcung cp dch v mng tn dng hai trng thi b sung ny.

2.2.3.4. Qun l tnh di ng trong mng v tuyn i vi cc knh dnhring

Mt tc v quan trng trong cc mng di ng l x l tnh di ng ca ngi dng. trngthi Cell-DCH, trm c s ch ng gim st ng truyn giao tip v tuyn t v n cc UE,v iu chnh cng sut pht ca trm c s v cng sut pht ca UE mi giy 1500 ln. Trongcc h thng CDMA, nhng s iu chnh cng sut rt nhanh nh vy l cn thit, bi v trmc s phi nhn c cc cuc truyn ca tt c cc UE cng mc cng sut, bt k chng rt gn hay rt xa trm. chiu t mng v UE nu dng c cng t cng sut pht th cngtt, bi v cng sut pht ca trm c s b gii hn. Trong thc t, cc cuc truyn n v ikhi cc UE gn trm c s ch cn mt lng cng sut pht nh, cn cc UE xa hoc bntrong cc ta nh cn nhiu cng sut pht hn. Vic iu chnh cng sut pht thng xuynnh vy cng c ngha l, cng vi d liu ngi dng, UE phi khng ngng bo co cho mngthng tin v mc tt m n nhn c d liu ngi dng. Sau mng x l thng tin ny

v ra lnh cho UE, theo cng nhp khn trng , l n nn tng, gi nguyn, hay gim cngsut pht hin ti. V mc ch ny, lun c mt knh iu khin dnh ring c thit lp bn


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cnh mt knh truyn d liu dnh ring. Trong khi ni dung ca knh truyn d liu dnh ringc ch nh cc tng cao hn ca chng giao thc, l cc tng m cui cng s trch xut ramt gi thoi hoc mt gi IP, th thng tin c vn chuyn trong knh iu khin ny nmtrong chng phn mm v tuyn v khng l ra vi cc ng dng tng cao hn.

Khi mt ngi dng di chuyn, n mt lc no h s ri khi vng ph sng ca mttrm c s. Trong khi mt knh d liu (DCH) c thit lp, RNC chu trch nhim iu chnhsao cho d liu gi n UE c truyn n mt cell thch hp hn. Quyt nh chuyn cell nyda trn cht lng nhn sng ca cell hin thi v cc cell k cn, vn c o bi UE v gin mng. Trong cc mng da trn CDMA nh UMTS chng hn, c hai loi chuyn giao(handover) khc nhau. Loi th nht c gi l chuyn giao cng(hard handover). Khi mng

pht hin rng c mt cell thch hp hn cho mt UE no , n chun b cell mi cho thu baoc UE y, ri sau ra lnh cho UE y chuyn i sang cell mi. K tip UE s ngt ngtruyn vi cell hin ti ri dng nhng thng s chuyn giao m mng gi cho, bao gm thngtin v tn s v cc m tri ca cell mi, thit lp mt ng truyn. Do chuyn giao cngcn c gi l chuyn giao ngt-trc-khi-lm (break-before-make handover), tc ng

truyn c b ct i trc khi ng truyn mi c thit lp.Loi chuyn giao th hai l chuyn giao mm (soft handover), vn l loi chuyn giao thngc s dng nht trong cc mng CDMA. Chuyn giao mm tn dng s kin l cc cell k cnnhau truyn trn cng tn s vi cell hin ti. V vy, c th thc hin mt cuc chuyn giaolm-trc-khi-ngt (make-before-break handover), tc l UE lin lc vi nhiu cell cng mtlc. UE s i vo trng thi chuyn giao mm khi mng gi thng tin iu khin ra lnh chon lng nghe nhiu m tri hng xung. Mi m tri i din cho mt ng truyn ca mtcell khc bit, v UE kt hp cc tn hiu n nhn t cc cell khc bit y. hng ln, UE tiptc s dng ch mt m tri duy nht cho mt knh dnh ring. Tt c cc cell tham gia vo cucchuyn giao mm u c RNC ch th phi m ha d liu gi bng m ny ri gi n nRNC. V vy trong sut qu trnh chuyn giao mm, RNC tip nhn n vi phin bn ca dng

d liu ti ln ca ngi dng. iu ny gip bo m rng cc gi c tip nhn ng n vkhng cn truyn li. Nhng cell c lin quan trong mt chuyn giao mm i vi mt knhdnh ring c gi l nhm tch cc (active set). Mi nhm tch cc c th c n ti a l sucell tham gia. Tuy nhin trong thc t, hu ht cc mng u hn ch s lng cell trong nhmtch cc l hai hoc ba thi. Nu khng lm vy, li ch ca nhiu ng truyn m c th kthp vi c mng ln UE s b e da bi dung lng b sung cn c trong c mng v tuyn lntrn giao tip v tuyn. ci thin dung lng ca mng, khong 3040% ca tt cc knhdnh ring trong mt mng v tuyn c t trng thi chuyn giao mm, cho d ngi dngkhng di chuyn.

Hnh 2.8 cho thy chuyn giao mm v chuyn giao cng c thc hin nh th no trong

trng hp khng phi tt c cc cell u c ni kt vi cng mt RNC. Trong v d ny, dliu ti ln v ti xung c thu thp v phn phi bi hai RNC, nhng ch mt trong hai RNC, gi l Serving-RNC (S-RNC, tcRNC phc v), lin lc vi mng li thi. RNC cn li, gil Drift-RNC (D-RNC, tm dch:RNC tri git), th lin lc vi S-RNC.

Nu ngi dng di chuyn su hn vo trong khu vc c ph sng bi NodeB 2 v NodeB3, UE ca ngi dng vo mt thi im no s mt lin lc vi NodeB 1. Lc , khngcn cn c s dnh lu ca RNC ang iu khin NodeB 1 na, v th S-RNC hin ti lin yucu SGSN thng cp Drift-RNC hin ti thnh S-RNC mi.

Nu ng giao tip (ty chn) gia cc RNC khng hin din th mt cuc chuyn giaomm nh minh ha trong Hnh 2.8 khng th xy ra. Trong trng hp ny, cn c mt cuc

chuyn giao cng khi UE di chuyn ra khi vng ph sng ca NodeB 1 v vo vng ph sngca hai NodeB cn li. Hn na, vic chuyn i RNC phc v phi c thc hin cng lc ,


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iu ny lm phc tp thm th tc chuyn giao v c kh nng lm tng khong thi gian mkhng c d liu no c trao i gia UE v mng.

Hnh 2.8: Chuyn giao mm vi vi RNC.

Nu ngi dng di chuyn gia cc vng c iu khin bi hai SGSN khc nhau th cnthay i lun SGSN phc v. Phc tp hn na, cc cuc chuyn giao cng c th din ra khi chai ng truyn chuyn knh v chuyn gi u tch cc. Trong trng hp nh vy, khng chcn thay i cc RNC m cn phi thay i c SGSN v MSC na. iu ny i hi cc mngli chuyn knh v chuyn gi cn cng tc cht ch hn. Tuy thng th cc tnh hung chuyngiao trong thc t ch dnh dng n cc cell c kim sot bi cng mt RNC thi, nhngngi ta cng thc hin tt c cc phng n chuyn giao khc.

Bi v cc mng 3G/3.5G lc trc khng c vng ph sng rng bng cc mng GSM 2Ghin c, v ngy nay thng th vng ph sng ca n cng khng rng bng v kh nng xuyntng cng yu hn GSM, cho nn kh nng chuyn vng cc ng truyn ang tch cc tchng sang cc mng GSM rt quan trng. iu ny , v nay vn, c bit quan trng i vicc cuc gi thoi. V th, cc UE c kh nng UMTS hin nay khng ch tm kim cc cell3G/3.5G k cn, m c th cn c mng ra lnh tm kim cc cell GSM na. Trong khi mtknh dnh ring ang c thit lp, iu ny rt kh thc hin, bi v trong ch truyn chunmc th UE gi v nhn lin tc. i vi cc cell nm ti ra ca vng ph sng, RNC c thkch hot mt ch truyn nn (compressed transmission mode). Ch truyn nn ny khc

phc nhng chnh lnh v thng lng trong giao tip v tuyn gia 2G v 3G/3.5G, cho php

b thu sng ca UE iu chnh li ph hp vi tn s ca cc cell GSM k cn, nhn tn hiuca chng, ng b ha vi chng, ri quay tr li cell UMTS tip tc truyn v bo co ktqu ca vic o c tn hiu ca cc cell GSM k cn v cho mng. Sau , da vo cc s liuo c ny, mng c th ra lnh cho UE thc hin mt cuc chuyn giao cng Inter-RAT (Inter-Radio Access Technology) vi GSM. Trong sut mt cuc gi thoi n, ngi dng thngkhng hay bit g v mt s chuyn giao cng nh vy. Tuy nhin, mt ng truyn d liuUMTS khi c chuyn giao qua mng GSM/GPRS/EDGE s chm hn ng k so vi bnhthng.

2.2.3.5. Qun l tnh di ng ca mng v tuyn trong cc trng thi Idle,Cell-FACH v Cell/URA-PCH

Khi ngi dng di chuyn v UE ca h ang trong trng thi Idle hoc Cell/URA-PCH, tcl khng c cuc gi thoi no c thit lp v knh truyn vt l ca mt cuc gi d liu


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c g b sau mt giai on th ng, UE c th t quyt nh chuyn sang mt cell c tnhiu tt hn. Vng ph sng ca cc cell c nhm li thnh cc vng v tr(location area), vcc UE chuyn sang cell khc ch cn lin h vi mng bo co v tr mi ca chng khi chnla mt cell no vng v tr mi ca chng. Th c ngha l cc thng ip nhn tin phic qung b tt c cc cell thuc mt vng v tr. Trong thc t, mt vng v tr cha khong

20 n 30 trm c s, l mt s cn bng tha ng gia vic gim lng thng ip cp nhtv tr v vic tng ph ph ca vic gi i cc thng ip nhn tin vo tt c cc cell ca mtvng v tr.

trng thi Cell-FACH, vn c dng nu UE i vo mt giai on tch cc thp hn (v dnh, n ch gi hoc nhn vi gi IP ri rc), th nhng thay i v cell cng c kim sot biUE ch khng phi bi mng. y, mt s chuyn dch hiu qu t cell ny sang cell khcc cho l khng quan trng bin minh cho vic gia tng cng sut x l ca mng vmc tiu th in nng cao hn trong UE.

2.2.3.6. Qun l tnh di ng trong mng li chuyn gi

Trong mng li chuyn gi, SGSN chu trch nhim theo di v tr v tnh kh tip cn(reachability) ca cc UE. ng truyn gia SGSN v RNC trng thi PMM-Detached(PMM l dng vit tt ca Packet Mobility Management) ngha l UE khng c ng k vimng, v v vy khng c cp a ch IP no. ng truyn trng thi PMM-Connectednu UE c mt ng truyn bo hiu ni vi SGSN (v d nh trong thi gian cp nht v tr, bo co v tr mi ca n), v UE cng c cp pht mt ng truyn IP, tuy nhin SGSNch bit RNC no hin ang chu trch nhim gi chuyn tip gi cho UE ch khng cn bitm nhn din ca cell c UE . Kin thc ny khng cn thit, bi v SGSN ch gi chuyn tipgi d liu n RNC thi, ri RNC chu trch nhim gi chuyn tip n n cell hin c UE .

Ngoi ra, SGSN khng bit l knh truyn v tuyn n UE ang trng thi Cell-FACH,Cell-DCH, Cell-PCH hay URA-PCH. Thng tin ny khng cn thit, bi v chnh RNC mi chu

trch nhim quyt nh gi UE nhng mc yu cu cht lng dch v no ca mt ngtruyn v lng d liu c truyn ti vi UE . Ch rng, ng truyn gia SGSN vRNC cng i vo trng thi PMM-Connected trong nhng khong thi gian ngn trong khi thitlp nhng cuc trao i thng tin bo hiu, nh thng tin cp nht v tr chng hn, cho d khngc ng truyn IP no c thit lp.

Nu RNC t knh v tuyn trng thi Idle, n cng thng bo vi SGSN rng n khngcn tip cn trc tip vi UE n

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