mang thong tin di dong gsm

8/14/2019 Mang Thong Tin Di Dong GSM

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"ti: M3ng thng tin di 56ng GSM

Gio vin h!ng d$n: TS. Ph(m Cng HngSinh vin th*c hi+n :L!p :

H N-I, 1- 2005


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M3C L3C

M3C L3C................................................................................................... 1L5I NI 89U............................................................................................. 3

CH06NG 1. C:U HNH M?ng GSM ............................. 41.1.1. Vi nt lAch sCv=m(ng GSM..................................................... 41.1.2. Cc chEtiu kGthuJt cKa m(ng GSM ......................................... 5

1.2. CMu trc h+thOng GSM......................................................................... 61.2.1. H+thOng con chuyPn m(ch SS ....................................................... 6

1.2.1.1. Trung tm chuyPn m(ch cc dAch vRdi >?ng cSng MSC ......... 71.2.1.2. B?ghi >Anh vAthTng tr HLR............................................... 81.2.1.3. B?ghi >Anh vAt(m tr VLR..................................................... 81.2.1.4. Trung tm nhJn th*c AUC ...................................................... 81.2.1.5. B?>Ung k nhJn d(ng thiWt bAEIR.......................................... 8

1.2.2. Phn h+tr(m gOc BSS.................................................................... 91.2.2.1. Tr(m thu pht gOc BTS........................................................ 91.2.2.2. B?>i=u khiPn tr(m gOc BSC ............................................... 91.2.2.3. B?chuyPn >Si m v thch Xng tOc >?TRAU ....................10

1.2.3. Tr(m di >?ng MS ..........................................................................101.2.4. Phn h+khai thc OSS ..................................................................112.1. V tuyWn sOtSng qut.......................................................................12

2.1.1. Suy hao >Tng truy=n v pha >inh ............................................12

2.1.2. Phn tn thTi gian......................................................................142.1.3. Cc ph"ng php phng ngYa suy hao truy=n d$n do pha>inh ..152.1.4. Ph"ng php chOng phn tn thTi gian......................................17

2.1.5. Truy=n d$n sOv tn hi+u t"ng t* ........................................18 2.2. Nguyn tZc khi chia knh theo khe thTi gian ....................................20

2.2.1. Khi ni+m knh .........................................................................202.2.1.1. Knh vJt l .........................................................................202.2.1.2 Knh logic ...........................................................................21

2.2.2. CRm ..........................................................................................222.2.3. Chia knh logic theo khe thTi gian ............................................23

CH06NG 3. NGUYN T[C S\D3NG T9N S] ...................................25 3.1. Nguyn tZc sCdRng t^n sOtheo chia ..............................................25

3.1.1. SCdRng t^n sO ...........................................................................253.1.2. S*ti sCdRng t^n sOtrn m(ng.................................................26

3.1.2.1. C"s_l thuyWt ....................................................................263.1.2.2. M$u sCdRng l(i t^n sO........................................................26


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3.2. Cc trTng h`p v thKtRc thng tin .................................................293.2.1. TSng quan .................................................................................293.2.3. ThKtRc nhJp m(ng >Ung k l^n >^u ..........................................30 3.2.4. ThKtRc rTi m(ng .......................................................................313.2.5. Tm gai......................................................................................313.2.6. Gai tYMS .................................................................................313.2.7. Gai >Wn thu bao MS.................................................................313.2.8. Cu?c gai >ang tiWn hnh, >Anh vA ...............................................32

CH06NG 4. CC DbCH V3CdA GSM ..................................................34 4.1. DAch vRtho(i....................................................................................344.2. DAch vRsOli+u .................................................................................344.3. DAch vRnhZn tin ngZn SMS..............................................................344.4. DAch vRWap ....................................................................................344.5. Cc dAch vRm!i cKa GSM 2,5G.......................................................35

KeT LU1N ................................................................................................36PH3L3C: CC TgVIeT T[T ................................................................37


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L5I NI 89U

Hi+n nay trong cu?c sOng hng ngy thng tin lin l(c >ng m?t vai tr rMtquan trang khng thP thiWu >`c, n quyWt >Anh nhi=u mht ho(t >?ng cKa x h?i,

gip con ngTi nZm bZt nhanh chng cc gi trA vUn ho, kinh tW, khoa hac kGthuJt rMt >a d(ng v phong ph.Bing nhjng b!c pht triPn th^n kk, cc thnh t*u cng ngh+8i+n TC

Tin Hac Viln Thnglm thay >Si cu?c sOng con ngTi tYng giTtYng pht , nt(o ra m?t tro lu "8i+n TC Tin Hac Viln Thng " trong mai lmnh v*c _thWkn21.

Lmnh v*c Thng Tin Di 8?ng cong khng nim ngoi tro lu >. Cng v!inhi=u cng ngh+khc nhau Thng Tin Di 8?ng >ang khng ngYng pht triPn >pXng nhu cû thng tin ngy cng tUng cp v= sO l`ng v chMt l`ng, t(o nhi=uthuJn lì trong mi=n thTi gian cong nh khng gian. ChZc chZn trong t"ng laiThng Tin Di 8?ng sq>`c hon thi+n nhi=u h"n nja >Pthopmn nhu cû thngtin t*nhin cKa con ngTi.

Trn c" s_ nhjng kiWn thXc > tch luG>`c qua 5 nUm hac tJp chuynngnh 8i+n TC Viln Thng t(i trTng 8(i hac Bch Khoa H N?i v h"n m?tthng th*c tJp t(i phng kG thuJt cng ty thng tin di >?ng VMS, ti > honthnh bpn bo co th*c tJp tOt nghi+p ny.

8P hon thnh bpn bo co ny ti xin chn thnh cpm "n th^y gio TSPh(m Cng Hng > tJn tnh h!ng d$n ti trong suOt qu trnh th*c tJp tOtnghi+p.

Ti cong xin chn thnh cpm "n s* gip >r nhi+t tnh cKa tr_ng phng8sVoAnh cng cc cn b?phng kGthuJt trong suOt qu trnh th*c tJp .


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CH"NG 1. C9U HNH M%NG GSM

1.1 Gi;i thi>u chung v@m3ng thng tin di 56ng GSM

1.1.1. Vi nt lAch sCv@m3ng GSM

H+thOng thng tin di >?ng tYlu > l m?t !c m"l!n cKa con ngTi, v!c m"ny > tr_thnh hi+n th*c ngay khi kGthuJt cho php. S*th*c hi+n >ûtin bing sng v tuyWn >`c th*c hi+n tYcuOi thWkn19. Tuy nhin vi+c >a h+thOng thng tin di >?ng vo phRc vR chE>`c th*c hi+n sau chiWn tranh thWgi!il^n thX 2, khi m cng ngh+>i+n tC cho php. 8 l m?t dAch vR thng tin >hc

bi+t, n cho php nOi thng cc cu?c gai khng c^n dy d$n. Ngay > ngay cpkhidi chuyPn, cc thu bao di >?ng v$n trao >Si thng tin >`c v!i nhau. Do s*phttriPn ngy cng cao cKa cng ngh+>i+n tCv thng tin, m(ng thng tin ngy cng

phSbiWn, gi cpngy m?t h(v >?tin cJy ngy cng tUng ln. Qu trnh pht triPncKa m(ng thng tin > trpi qua cc giai >o(n sau:

-Giai 5o3n thFnhGt: Sau 1946, khpnUng phRc vRnht, chMt l`ng khngcao, gi cpdZt.

- Giai 5o3n thFhai:TY1970 1979, cng v!i s*pht triPn cKa cc thiWtbA>i+n tCtSh`p crl!n v cc b?vi xCl, ta c thPth*c hi+n >`c m?t h+thOngphXc t(p h"n. B_i v vng phKsng cKa anten pht cKa cc my di >?ng bAh(n chWnn h+thOng >`c chia thnh m?t vi tr(m nhJn cho m?t tr(m pht.

- Giai 5o3n thFba: TY1979 -1990, l m(ng tSong t"ng t*. Cc tr(m thupht >`c >ht theo cc tSong. M(ng ny cho php sC dRng l(i t^n sO v chophp chuyPn giao gija cc trong cu?c gai. Cc m(ng >iPn hnh l:

+ AMPS (Advanced Mobile Phone Service): >`c >a vo ho(t >?ng t(i

MGnUm 1979.+NMT ( Nordic Mobile Telephone): l h+ thOng cKa cc n!c BZc u v>`c >a vo sCdRng vo thng 12/1981.

+TACS ( Total Access Communication System): >`c >a vo phRc vRt(iV"ng quOc Anh nUm 1985.

TMt cp cc m(ng trn d*a trn m(ng truy=n >i+n tho(i t"ng t*bUng >i=uchWt^n sO. Chng sCdRng t^n sO450 hohc 900 Mhz. Vng phKsng cKa n chE_mXc quOc gia v phRc vR>`c vi trUm thu bao. H+ thOng l!n nhMt _ Anh lTACS >(t h"n m?t tri+u thu bao vo nUm 1990.

- Giai 5o3n thF tD: TY>û nhjng nUm 1980, sau khi cc h+thOng NMT

> ho(t >?ng thnh cng th n cong biPu hi+n m?t sOh(n chW. M?t l do yu cûcho dAch vR di >?ng qu l!n v`t qua con sOmong >ì cKa cc nh thiWt kW h+thOng nn h+thOng ny khng >p Xng >`c. Hai l cc h+thOng khc nhau >angho(t >?ng khng thPphRc vRcho tMt cpcc thu bao _chu u, nghma l thiWt bAcKa m(ng ny khng thP truy nhJp vo m(ng khc. Ba l nWu thiWt kWm?t m(ngl!n phRc vRcho cpchu u th khng m?t n!c no c thP>p Xng >`c v vOn>û tqu l!n. TMt cpnhjng h(n chWtrn d$n >Wn m?t nhu cû l phpi thiWt kWm?th+thOng lo(i m!i >`c lm theo kiPu chung >Pc thPdng cho nhi=u n!c. NUm


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1988, vi+n tiu chuun viln thng chu u ETSI (Europe TelecommunicationStandard Institute) > thnh lJp nhm >hc trch di >?ng GSM (Groupe SpecialMobile). GSM cn c nghma l h+thOng thng tin di >?ng ton cû (Global Systemfor Mobile Communication). GSM l tiu chuun >i+n tho(i di >?ng sOton chuu sCdRng dpi t^n sO900Mhz.

NUm 1990, V"ng quOc Anh >a ra h+ thOng DCS (Digital CellularSystem). DCS d*a trn h+thOng GSM v!i vi+c sCdRng t^n sO1800Mhz.

Hi+n nay, >P>p Xng nhu cû ngy cng tUng v= cc dAch vR viln thngm!i, cc h+ thOng thng tin di >?ng >ang tiWn t!i thWh+ thXba. v thWh+ thXbany, cc h+thOng thng tin di >?ng c xu thWho nhJp thnh m?t tiu chuun duynhMt v c khpnUng phRc vR_tOc >?ln >Wn 2Mbit/s.

v Vi+t Nam, h+ thOng thng tin di >?ng sO GSM >`c >a vo tY nUm1993, hi+n nay >ang >`c hai cng ty VMS v GPC khai thc rMt hi+u qup. TrongnUm 2004 ny cng ty Vietel cong sqcung cMp dAch vRny.

1.1.2. Cc chItiu kKthuNt cOa m3ng GSMH+thOng thng tin di >?ng GSM cho php chuyPn vng t*do cKa cc thubao trong chu u, c nghma l m?t thu bao c thP thm nhJp sang m(ng cKan!c khc khi di chuyPn qua bin gi!i. Tr(m di >?ng GSM MS (GSM MobileStation) phpi c khpnUng trao >Si thng tin t(i bMt cXn"i no trong vng phKsngquOc tW.

Q V@khRnSng phUc vU:- H+ thOng >`c thiWt kW sao cho MS c thP dng >`c trong tMt cp ccn!c

c m(ng.

- Cng v!i phRc vRtho(i, h+thOng phpi cho php s*linh ho(t l!n nhMt chocc lo(i dAch vRkhc lin quan t!i m(ng sOlin kWt >a dAch vR(ISDN).- T(o m?t h+thOng c thPphRc vRcho cc MS trn cc tû viln d"ng nh

m?t m(ng m_r?ng cho cc dAch vRdi >?ng mht >Mt.Q V@chGt lDVng phUc vUv an ton bRo mNt:- ChMt l`ng cKa tho(i trong GSM phpi t nhMt c chMt l`ng nhcc h+

thOng di >?ng t"ng t*tr!c > trong >i=u ki+n vn hnh th*c tW.- H+thOng c khpnUng mJt m ho thng tin ngTi dng m khng pnh

h_ng g >Wn h+ thOng cong nhkhng pnh h_ng >Wn cc thu bao khc khngdng >Wn khpnUng ny.

Q V@sCdUng tWn sX:- H+thOng cho php mXc >?cao v=hi+u qupcKa dpi t^n m c thPphRc

vR_vng thnh thAv nng thn cong nhcc dAch vRm!i pht triPn.- Dpi t^n sOho(t >?ng l 890-915 v 935-960 Mhz.- H+thOng GSM 900Mhz phpi c thPcng twn t(i v!i cc h+thOng dng

900Mhz tr!c >y.Q V@m3ng:- KWho(ch nhJn d(ng d*a trn khuyWn nghAcKa CCITT.


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- KWho(ch >nh sOd*a trn khuyWn nghAcKa CCITT.- H+thOng phpi cho php cMu trc v tnl+tnh c!c khc nhau khi >`c

dng trong cc m(ng khc nhau.- Trung tm chuyPn m(ch v cc thanh ghi >Anh vAphpi dng h+thOng bo

hi+u >`c tiu chuun ho quOc tW.

- ChXc nUng bpo v+thng tin bo hi+u v thng tin >i=u khiPn m(ng phpi>`c cung cMp trong h+thOng.

1.2. CGu trc h>thXng GSMM?t h+thOng GSM c thP>`c chia thnh nhi=u phn h+sau >y:

- Phn h+chuyPn m(ch (SS: Switching Subsystem)- Phn h+tr(m gOc (BSS: Base Station Subsystem)- Phn h+khai thc (OSS: Operation Subsystem)- Tr(m di >?ng (MS: Mobile Station)

1.2.1. H>thXng con chuyYn m3ch SS

H+thOng con chuyPn m(ch bao gwm cc chXc nUng chuyPn m(ch chnh cKaGSM cong nhcc c"s_djli+u c^n thiWt cho sOli+u thu bao v qupn l di >?ng

BSS

MS

AUC

HLR

MSC

VLR EIR

SS

BSC

BTS

OSS

ISDN

PSPDN

CSPDN

PSTN

PLMN

Hnh 1. M hnh h+thOng GSM


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cKa thu bao. ChXc nUng chnh cKa SS l qupn l thng tin gija nhjng ngTi sCdRng m(ng GSM v!i nhau v v!i m(ng khc.

H+thOng con chuyPn m(ch SS bao gwm cc khOi chXc nUng sau:- Trung tm chuyPn m(ch cc dAch vRdi >?ng (MSC: Mobile Services

Switching Center).

- B?ghi >Anh vAt(m tr (VLR: Visitor Location Register)- B?ghi >Anh vAthTng tr (HLR: Home Location Register)- Trung tm nhJn th*c (AUC: Authentication Center)- B?nhJn d(ng thiWt bA(EIR: Equipment Identity Register)- Trung tm chuyPn m(ch cc dAch vR di >?ng cSng (GMSC: Gateway

Mobile Services Switching Center)

1.2.1.1. Trung tm chuyYn m3ch cc dAch vUdi 56ng c[ng MSCvSS, chXc nUng chuyPn m(ch chnh >`c MSC th*c hi+n. Nhi+m vRchnh

cKa MSC l >i=u phOi vi+c thiWt lJp cu?c gai >Wn nhjng ngTi sC dRng m(ng

GSM. M?t mht MSC giao tiWp v!i phn h+BSS, mht khc n giao tiWp v!i m(ngngoi. MSC lm nhi+m vRgiao tiWp v!i m(ng ngoi >`c gai l MSC cSng. Vi+cgiao tiWp v!i m(ng ngoi >P>pm bpo thng tin cho ngTi sCdRng m(ng GSM >ihti cSng thch Xng (cc chXc nUng t"ng tc IWF: Interworking Function). SScong c^n giao tiWp v!i m(ng ngoi >P sC dRng cc khp nUng truy=n tpi cKa ccm(ng ny cho vi+c truy=n tpi sO li+u cKa ngTi sC dRng hohc bo hi+u gija cc

ph^n tCcKa m(ng GSM. MSC thTng l m?t tSng >i l!n >i=u khiPn v qupn lm?t sOcc b?>i=u khiPn tr(m gOc .

8P kWt nOi MSC v!i m?t sOm(ng khc, c^n phpi thch Xng cc >hc >iPmtruy=n d$n cKa GSM v!i cc m(ng ny. Cc thch Xng ny >`c gai l cc chXc

nUng t"ng tc IWF (Interworking Function) bao gwm m?t thiWt bA>P thch Xnggiao thXc v truy=n d$n. N cho php kWt nOi v!i cc m(ng: PSPDN (PacketSwitched Public Data Network: m(ng sO li+u cng c?ng chuyPn m(ch gi), hayCSPDN (Circuit Switched Public Data Network: m(ng sO li+u cng c?ng chuyPnm(ch knh), n cong twn t(i khi cc m(ng khc chE>"n thu^n l PSTN hay ISDN.IWF c thP>`c th*c hi+n trong cng chXc nUng MSC hay c thP_thiWt bAring,_trTng h`p hai th giao tiWp gija MSC v IWF >`c >Pm_.

8PthiWt lJp m?t cu?c gai >Wn ngTi sCdRng GSM, tr!c hWt cu?c gai phpi>`c >Anh tuyWn >Wn m?t tSng >i cSng GMSC m khng c^n biWt >Wn hi+n thTithu bao >ang _>u. Cc tSng >i cSng c nhi+m vR lMy thng tin v= vA tr cKathu bao v >Anh tuyWn cu?c gai >Wn tSng >i >ang qupn l thu bao _ thTi >iPmhi+n thTi (MSC t(m tr). 8PvJy tr!c ht cc tSng >i cSng phpi d*a trn sOtho(idanh b(cKa thu bao >Ptm >ng HLR c^n thiWt v hti HLR ny. TSng >i cSngc m?t giao di+n v!i cc m(ng bn ngoi v!i m(ng GSM. V=ph"ng di+n kinh tW,khng phpi bao giT tSng >i cSng cong >Xng ring m thTng >`c kWt h`p v!iMSC.


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1.2.1.2. B6ghi 5Anh vAthD\ng tr HLR

L c"s_djli+u quan trang nhMt cKa m(ng GSM, lu trjcc sOli+u v >AachE nhJn d(ng cong nh cc thng sO nhJn th*c cKa thu bao trong m(ng. Ccthng tin lu trjtrong HLR gwm: nhJn d(ng thu bao IMSI, MSISDN, VLR hi+nthTi, tr(ng thi thu bao, kho nhJn th*c v chXc nUng nhJn th*c, sO lu >?ngtr(m di >?ng MSRN.

HLR chXa nhjng c"s_djli+u bJc cao cKa tMt cpcc thu bao trong GSM.Nhjng djli+u ny >`c truy nhJp tYxa b_i cc MSC v VLR cKa m(ng.

1.2.1.3. B6ghi 5Anh vAt3m tr VLR

VLR l c" s_dj li+u thXhai trong m(ng GSM. N >`c nOi v!i m?t haynhi=u MSC v c nhi+m vRlu gijt(m thTi sOli+u thu bao cKa cc thu bao hi+n>ang nim trong vng phRc vRcKa MSC t"ng Xng v >wng thTi lu gijsOli+u v=vAtr cKa cc thu bao ni trn _mXc >?chnh xc h"n HLR. Cc chXc nUng VLRthTng >`c lin kWt v!i cc chXc nUng MSC.

1.2.1.4. Trung tm nhNn th]c AUC

AUC qupn l cc thng tin nhJn th*c v mJt m lin quan >Wn tYng c nhnthu bao d*a trn m?t kho nhJn d(ng b mJt Ki >P>pm bpo ton sOli+u cho ccthu bao >`c php. Kho ny cong >`c lu gijvmnh cCu v b mJt trong b?nh!_MS. B? nh! ny c dang Simcard c thP rt ra v cZm l(i >`c. AUC c thP>`c >ht trong HLR hohc MSC hohc >?c lJp v!i cphai.

Khi dUng k thu bao, kho nhJn th*c Ki >`c ghi nh! vo Simcard cKathu bao cng v!i IMSI cKa n. 8wng thTi kho nhJn th*c Ki cong >`c lu gij_trung tm nhJn th*c AUC >P t(o ra b?ba thng sO c^n thiWt cho qu trnh nhJn

th*c v mJt m ho:- SOng$u nhin RAND- MJt khuu SRES >`c t(o ra tY Ki v sO ng$u nhin RAND bing thuJtton

A3- Kho mJt m Kc >`c t(o ra tYKi v sOng$u nhin RAND bing thuJt

ton A8

1.2.1.5. B65Sng k nhNn d3ng thi^t bAEIR

Qupn l thiWt bAdi >?ng >`c th*c hi+n b_i b?>Ung k nhJn d(ng thiWt bA

EIR. EIR lu gij tMt cp cc dj li+u lin quan >Wn ph^n thiWt bAdi >?ng ME cKatr(m di >?ng MS. EIR >`c nOi v!i MSC thng qua >Tng bo hi+u >PkiPm tras*>`c php cKa thiWt bAbing cch so snh tham sOnhJn d(ng thiWt bAdi >?ngquOc tW IMEI (International Mobile Equipment Identity) cKa thu bao gCi t!i khithiWt lJp thng tin v!i sOIMEI lu gijtrong EIR phng trTng h`p >y l nhjngthiWt bA>^u cuOi bA>nh cZp, nWu so snh khng >ng th thiWt bAkhng thPtruynhJp vo m(ng >`c.


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1.2.2. Phn h>tr3m gXc BSS

BSS th*c hi+n nhi+m vR gim st cc >Tng ghp nOi v tuyWn, lin kWtknh v tuyWn v!i my pht v qupn l cMu hnh cKa cc knh ny. 8 l:

- 8i=u khiPn s* thay >Si t^n sO v tuyWn cKa >Tng ghp nOi (FrequencyHopping) v s*thay >Si cng suMt pht v tuyWn.

- Th*c hi+n m ho knh v tn hi+u tho(i sO, phOi h`p tOc >?truy=n thngtin.

- Qupn l qu trnh Handover.- Th*c hi+n bpo mJt knh v tuyWn.Phn h+BSS gwm hai khOi chXc nUng: b?>i=u khiPn tr(m gOc (BSC: Base

Station Controller) v cc tr(m thu pht gOc (BTS: Base Transceiver Station). NWukhopng cch gija BSC v BTS nhth"n 10m th cc knh thng tin c thP>`ckWt nOi tr*c tiWp (chW>?Combine), ng`c l(i th phpi qua m?t giao di+n A-bis(chW>?Remote). M?t BSC c thPqupn l nhi=u BTS theo cMu hnh hsn h`p cKa 2lo(i trn.

1.2.2.1. Tr3m thu pht gXc BTS

M?t BTS bao gwm cc thiWt bApht thu, anten v xCl tn hi+u >hc th chogiao di+n v tuyWn. C thPcoi BTS l cc Modem v tuyWn phXc t(p c thm m?tsO cc chXc nUng khc. M?t b?phJn quan trang cKa BTS l TRAU (Transcoderand Rate Adapter Unit: khOi chuyPn >Si m v thch Xng tOc >?). TRAU l thiWt bAm _> qu trnh m ho v gipi m tiWng >hc th ring cho GSM >`c tiWn hnh,_>y cong th*c hi+n thch Xng tOc >? trong trTng h`p truy=n sOli+u. TRAU lm?t b?phJn cKa BTS, nhng cong c thP>ht cch xa BTS v thJm ch trong nhi=utrTng h`p >`c >ht gija BSC v MSC.

BTS c cc chXc nUng sau:- Qupn l l!p vJt l truy=n d$n v tuyWn- Qupn l giao thXc cho lin kWt sOli+u gija MS v BSC- VJn hnh v bpo drng tr(m BTS- Cung cMp cc thiWt bAtruy=n d$n v ghp knh nOi trn giao tiWp A-bis

1.2.2.2. B65i@u khiYn tr3m gXc BSC

BSC c nhi+m vRqupn l tMt cpgiao di+n v tuyWn qua cc l+nh >i=u khiPntYxa BTS v MS. Cc l+nh ny chKyWu l cc l+nh Mn >Anh, gipi phng knh vtuyWn v qupn l chuyPn giao (Handover). M?t pha BSC >`c nOi v!i BTS cn

pha kia nOi v!i MSC cKa SS. Trong th*c tW, BSC l m?t tSng >i nhtc khpnUngtnh ton >ng kP. M?t BSC c thPqupn l vi chRc BTS tuktheo lu l`ng ccBTS ny. Giao di+n gija BSC v MSC l giao di+n A, cn giao di+n gija n v!iBTS l giao di+n A-bis.

Nhn vin khai thc c thPtYtrung tm khai thc v bpo drng OMC n(pph^n m=m m!i v dj li+u xuOng BSC, th*c hi+n m?t sOchXc nUng khai thc vbpo drng, hiPn thAcMu hnh cKa BSC.


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BSC c thP thu thJp sO li+u >o tY BTS v BIE (Base Station InterfaceEquipment: ThiWt bAgiao di+n tr(m gOc), lu trjchng trong b?nh!v cung cMpchng cho OMC theo yu cû.

1.2.2.3. B6chuyYn 5[i m v thch Fng tXc 56TRAU

Trong GSM, tn hi+u tho(i trn giao di+n v tuyWn >`c m ho _ tOc >?13Kbps sCdRng m ho ti=n >Anh tuyWn LPC. 8Pthch Xng tOc >?ny cc tOc >?m(ng h?i tho(i cO>Anh PSTN c^n c b?chuyPn >Si m TRAU >PchuyPn >Si gija13Kbps PCM gija MS v MSC. TRAU c thP>`c >ht t(i BTS, BSC hohc t(iMSC. 8P gipm thiPu chi ph truy=n d$n, thTng TRAU >ht _MSC. Khi > c^nthm bo hi+u bSxung vo tiWng tho(i 13Kbps >Ptruy=n thng tin >i=u khiPn tY

b?chuyPn >Si m tYxa dht _BTS >Wn TRAU.

1.2.3. Tr3m di 56ng MSTr(m di >?ng l thiWt bAduy nhMt m ngTi sCdRng c thP thTng xuyn

nhn thMy cKa h+thOng. MS c thPl: my c^m tay, my xch tay hay my >ht trn t. Ngoi vi+c chXa cc chXc nUng v tuyWn chung v xC l cho giao di+n vtuyWn MS cn phpi cung cMp cc giao di+n v!i ngTi sCdRng (nhmicr, loa, mnhiPn thA, bn phm >Pqupn l cu?c gai) hohc giao di+n v!i mt sOcc thiWt bAkhc(nhgiao di+n v!i my tnh c nhn, Fax). Hi+n nay, ngTi ta >ang cOgZng spnxuMt cc thiWt bA >û cuOi gan nhx >P >Mu nOi v!i tr(m di >?ng. Ba chXc nUngchnh cKa MS:

- ThiWt bA >û cuOi th*c hi+n cc chXc nUng khng lin quan >Wn m(ngGSM.

- KWt cuOi tr(m di >?ng th*c hi+n cc chXc nUng lin quan >Wn truy=n >$n _

giao di+n v tuyWn.- B? thch Xng >û cuOi lm vi+c nhm?t cCa nOi thng thit bA>û cuOiv!i kWt cuOi di >?ng. C^n sCdRng b?thch Xng >û cuOi khi giao di+n ngoi tr(mdi >?ng tun theo tiu chuun ISDN >P>Mu nOi >û cuOi, cn thiWt bA>û cuOi l(i cthPgiao di+n >û cuOi modem.

My di >?ng MS gwm hai ph^n: Module nhJn d(ng thu bao SIM( Subscriber Identity Module) v thiWt bAdi >?ng ME (Mobile Equipment).

8P>Ung k v qupn l thu bao, msi thu bao phpi c m?t b?phJn gai lSIM. SIM l m?t module ring >`c tiu chuun ho trong GSM. TMt cp cc b?

phJn thu, pht, bo hi+u t(o thnh thiWt bAME. ME khng chXa cc tham sOlinquan >Wn khch hng, m tMt cpcc thng tin ny >`c lu trj trong SIM. SIMthTng >`c chW t(o bing m?t vi m(ch chuyn dRng gZn trn thygai l Simcard.Simcard c thPrt ra hohc cZm vo MS.

Sim >pm nhi+m cc chXc nUng sau:- Lu gijkho nhJn th*c thu bao Ki cng v!i sOnhJn d(ng tr(m di >?ng

quOc tWIMSI nhim th*c hi+n cc thKtRc nhJn th*c v mJt m ho thng tin.- Khai thc v qupn l sOnhJn d(ng c nhn PIN(Personal Identity


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Number) >Pbpo v+quy=n sCdRng cKa ngTi s_hju h`p php. PIN l m?t sOgwmtY4 >Wn 8 chjsO, >`c n(p b_i nh khai thc khi >Ung k l^n >^u.

1.2.4. Phn h>khai thc OSSPhn h+khai thc OSS th*c hi+n ba chXc nUng chnh sau:

z Khai thc v b%o d()ng m,ng:Khai thc l cc ho(t >?ng cho php nh khai thc m(ng theo di hnh vi

cKa m(ng nh: tpi cKa h+thOng, mXc >?chhn, sOl`ng chuyPn giao gija hai ,nhTvJy nh khai thc c thPgim st >`c ton b?chMt l`ng cKa dAch vRm hacung cMp cho khch hng v kAp thTi xCl cc s*cO. Khai thc cong bao gwm vi+cthay >Si cMu hnh >Pgipm nhjng vMn >=xuMt hi+n _thTi >iPm hi+n t(i, >Pchuun

bAlu l`ng cho t"ng lai, >PtUng vng phK. vh+thOng viln thng hi+n >(i, khaithc >`c th*c hi+n bing my tnh v >`c tJp trung _m?t tr(m.

Bpo drng c nhi+m vRpht hi+n, >Anh vAv sCa chja cc s*cOhtng hc.N c m?t sOquan h+v!i khai thc. Bpo drng cong bao gwm cpcc ho(t >?ng t(i

hi+n trTng nhim thay thWthiWt bAc s*cO.H+ thOng khai thc v bpo drng c thP >`c xy d*ng trn nguyn lTMN (Telecommunication Management Network: M(ng qupn l viln thng). Lcny, m?t mht h+thOng khai thc v bpo drng >`c nOi >Wn cc ph^n tCcKa m(ngviln thng ( cc MSC, BSC, HLR v cc ph^n tC m(ng khc trY BTS, v thmnhJp >Wn BTS >`c th*c hi+n qua BSC). Mht khc, h+ thOng khai thc v bpodrng l(i >`c nOi >Wn m?t my tnh chK>ng vai tr giao tiWp ngTi my. Theotiu chuun GSM, h+thOng >`c gai l OMC (Operation and Maintenance Center:Trung tm khai thc v bpo drng).

z Qu%n l thu bao:

Bao gwm cc ho(t >?ng qupn l >Ung k thu bao. Nhi+m vR>^u tin lnhJp v xa thu bao khti m(ng. 8Ung k thu bao cong c thPrMt phXc t(p, baogwm nhi=u dAch vRv cc tnh nUng bSsung. Nh khai thc phpi c thPthm nhJp>`c tMt cpcc thng sOni trn. M?t nhi+m vRquan trang khc cKa khai thc ltnh c!c cc cu?c gai. C!c ph phpi >`c tnh v gCi >Wn thu bao. Qupn l thu

bao _GSM chElin quan >Wn HLR v m?t sOthiWt bAOSS ring ch{ng h(n m(ngnOi HLR v!i cc thiWt bAgiao tiWp ngTi my _cc trung tm giao dAch v!i thu

bao. Simcard cong >ng vai tr nhm?t b?phJn cKa h+thOng qupn l thu bao.z Qu%n l thi.t b0di 23ng:Qupn l thiWt bAdi >?ng >`c b?>Ung k nhJn d(ng thiWt bAEIR th*c

hi+n. EIR lu gijtMt cpcc djli+u lin quan >Wn tr(m di >?ng MS. EIR >`c nOi>Wn MSC qua >Tng bo hi+u >PkiPm tra s*>`c php cKa thiWt bA. M?t thiWt bAkhng >`c php sqbAcMm. Trong h+thOng GSM, EIR >`c coi l h+thOng conSS.


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CH"NG 2. V TUY_N S` GIAO TI_P V TUY_N S`

2.1. V tuy^n sXt[ng qutvph^n ny >=cJp >Wn vi+c sCdRng thiWt bAv tuyWn >Ptruy=n thng tin

gija tr(m di >?ng v m(ng PLMN GMS thay v dng dy. M?t sO vMn >=quantrang khi quy ho(ch t^n sOl s*h(n chWb_i >(i l`ng nhilu cKa h+thOng tSong.

2.1.1. Suy hao 5D\ng truy@n v pha 5inh

Suy hao >Tng truy=n l qu trnh m _> tn hi+u thu yWu d^n >o khopngcch gija tr(m di >?ng v tr(m gOc tUng m khng c mht cpn gija anten pht v

thu. Suy hao trong khng gian t*do:Ls d2.f2Ls (dB) = 33,4 (dB) + 20logF(MHz) + 20logd(km)

d: l kho%ng cch gi5a anten pht Tx v thu Rx.f: t6n s7pht(Cng th8c trn ch:2ng v?tn hi+u thu. Khi di >?ng cng v!i >i di >?ng cTng >?tnhi+u gipm v tUng d gija Tx v Rx c hay khng c ch!ng ng(i. Hi+u Xng nygai l pha >inh chuun log. ThTi gian gija 2 chs trong pha >inh khopng vi giy

khi my di >?ng MS l lo(i lZp trn xe v chuyPn >?ng.

MS


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Pha>inh chuun logarit

Trong trTng h`p mi trTng thng tin c mJt >? thu bao dy v nhi=uch!ng ng(i ta c pha >inh nhi=u tia hay raile, xpy ra khi tn hi+u truy=n nhi=u

>Tng tY anten Tx >Wn Rx.vhi+n t`ng pha >inh raile, tn hi+u thu >`c l tSng cc tn hi+u phpn x(

khc pha, khc bin >?. Nhjng tn hi+u ny khi c?ng l(i nhcc vct"t(o nn m?tvct"tSng g^n bing khng c nghi l cTng >?tn hi+u bing 0. 8y l chstrong

pha nghim trang. Khopng thTi gian gija hai chstrong pha>inh phRthu?c vo tOc>?chuyPn >?ng v t^n sOpht.

Pha>inh Raile

vm?t khopng cch nhMt >Anh (x mt) so v!i anten pht Tx, tn hi+u thu >`c minh

ho(nhsau:

8?nh(y my thu l mXc tn hi+u vo yWu nhMt c^n thiWt cho m?t tn hi+u raqui >Anh. Khi quy ho(ch h+ thOng, >P chOng l(i pha >inh th gi trA trung bnhchung >`c lMy l!n h"n >?nh(y my thu l`ng Y(dB) bUng chstrong pha pha>inhm(nh nhMt, Y(dB) >`c gai l d*trjpha>inh.

MS

8?nh(y my thu

mX + 15X + 10X

D*trjpadinh

Gi trAtrung bnh cRc b?

Chstrong padinh

Gi trAtrung bnh chung

CTng >?tn hi+u thu (Rx), Fc = 900MHz


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2.1.2. Phn tn th\i gian

Hi+n t`ng ny c nguwn gOc tYphpn x(tYm?t vJt _xa anten thu Rx vikm. N d^n >Wn giao thoa gija cc k hi+u ISI tXc l giao thoa gija cc k hi+uln cJn v!i nhau.

vGMS tOc >?bit l 270kB/s, msi bit t"ng Xng v!i 3,7s v t"ng Xng v!ikhopng cch l 1,1km. Khi c phpn x( tY1km pha sau tr(m di >?ng th tn hi+u

phpn x(phpi qua g"ng >Tng di trltn hi+u >i th{ng 2km. Tn hi+u mong muOnsq>`c tr?n v!i tn hi+u 2bit.

H+thOng GSM >`c thiWt kWc thPh(n chWphn tn thTi gian nhTsCdRngm?t b?cn bing m c thPth*c hi+n cn bing m?t sOnhMt >Anh tn hi+u phpn x(nhng khng phpi l tMt cp. B?cn bing cKa GSM c thP>(t >`c s*cn bingcho cc tn hi+u phpn x( chJm khopng 4 bt so v" tn hi+u >Wn tr*c tiWp, t"ngXng v!i 15 s. Tuy nhin nWu tn hi+u phpn x(m >Wn trlh"n thWth b?cn bingkhng thP>p Xng >`c. Giai >o(n m b?cn bing c thP>p Xng >`c gai l msO thTi gian. Trong cCa sS thTi gian > sq tUng cTng >? tn hi+u >Wn tr*c tiWp.

TSng cc tn hi+u phpn x(c thPnhth"n 15s phpi t nhMt nhth"n 9 l^n tSng cctn hi+u trong cCa sS. TE sOny gai l tE sO sng mang trn sng phpn x( (C/R).C/R >`c tnh bing tEsOgija nUng l`ng trong cCa sSv nUng l`ng ngoi cCa sScKa b?cn bing. C/R cng nhtth chMt l`ng cng km. VAtr >ht BTS pnh h_ngrMt l!n >Wn tEsOny nn >ht khng h`p l sqgy nn phn tn thTi gian l!n. Ccvng c >Aa hnh nhmi=n ni, thnh phOnhi=u nh cao t^ng, vng hwxy d*ngnhi=u th=m, bJc thTng c tEsOC/R nht.

Thng thTng tn hi+u phpn x(phpi >i qua qung >Tng l!n h"n 4,5 Km sov!i tn hi+u tr*c tiWp th m!i c trlh"n 1,5s tuy nhin nWu tn hi+u phpn x(>khng m(nh tXc l tEsOC/R l!n h"n 1 sOcho php th khng pnh h_ng >Wn vng

sng phRc vR.Ng`c l(i nWu tn hi+u phpn x(m(nh nhng trlv$n thu?c cCa sSth sqtUng

>?m(nh cKa tn hi+u >i th{ng. ChEkhi C/R nhtphn tn thTi gian l!n th m!i cyu c^u thay >Si vi tr BTS, hohc dng ph"ng php >ht thm BTS phR tr . Khist vMn >=ny cn phpi cUn cXvo cc vAtr cn >Oi gija MS v BTS b_i v msi vAtr d l cch nhau khng l!n th c thPC/R cch nhau rMt l!n.

* Nhilu >wng knh:Nhilu giao thoa >wng knh l nhilu do tn hi+u thu khng mong muOn c

cng t^n sOv tn hi+u thu mong muOn. TE sOgija mXc sng mang khng mongmuOn l tEsOnhilu giao thoa >wng knh (C/I). TEsOny phRthu?c vo nhjng yWu

tOnh:+ M$u sCdRng l(i t^n sO: khopng cch gija hai Cell cng t^n sOpnh h_ng

l$n nhau.+ VAtr >Aa hnh.+ Cc vng phpn x(>Aa ph"ng.+ KiPu Angten, tnh >Anh h!ng, chi=u cao Angten.+ Cc sng gy nhilu >Aa ph"ng c cng t^n sO.


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TEsOny gy pnh h_ng rMt m(nh >Wn chMt l`ng tn hi+u, d$n >Wn sai tnhi+u, gipi m sai gy nn st cu?c gai hohc thMt b(i trn >Tng nOi v tuyWn. Tiuchuun GSM cho php C/I nht nhMt l 10. Ngoi ra trong thng tin v tuyWn tnhi+u cn bApnh h_ng cc knh ln cJn l cc knh g^n t^n sOv!i tn hi+u thu, dpit^n cKa chng trng ln nhau _mXc l!n. Trong trTng h`p ny cong gy nhiWu gai

l nhilu giao thoa knh ln cJn (C/A) trong th*c tWcc t^n sOcKa cc BTS cng vAtr thTng gy pnh h_ng cho nhau.

Tn hi+u thu >`c khi >o >(c thTng gwm rMt nhi=u lo(i tn hi+u v nhilunh> kPtrn. Khi >o >(c ta c thPxc >Anh tEsOC/(I+R+A), >nh gi mXc >?hohc lsi c thPxc >Anh >`c tEsOny phpi nhT>Wn cc my >o chuyn dRng

2.1.3. Cc phDinh su cng m?t lc, nn ta

sCdRng 2 anten Rx >?c lJp thu cng tn hi+u rwi kWt h`p cc tn hi+u ny l(i ta sqc m?t tn hi+u ra khti b?kWt h`p t bApha>inh h"n. Khopng cch gija hai anten

phpi >Kl!n >Pt"ng quan gija cc tn hi+u _hai anten nht.

BTS

0

0

1

1

Phn tn thTi gian

21

Tn hi+u 1 Tn hi+u 2C8TH

SSAnten


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Nh$y t&n:V!i pha >inh raile, m$u pha>inh phR thu?c vo t^n sOnghma l chs trong

pha>inh xpy ra _cc vAtr khc nhau >Oi v!i cc t^n sOkhc nhau. NhvJy ta cthPthay >Si t^n sOsng mang trong m?t sOt^n sOkhi cu?c gai >ang tiWn hnh, khighp chstrong pha>inh chEm?t ph^n thng tin bAmMt.

M ho knh:vtruy=n d$n sOngTi ta >o chMt l`ng cKa tn hi+u >`c chKyWu bing sO

l`ng cc bit thu >`c chnh xc, d$n >Wn biPu diln tnsObit lsi BER. BER khngthPbing khng do >Tng truy=n d$n lun lun thay >Si. Nghma l ta phpi cho phpm?t lang lsi nhMt >Anh v c khpnUng khi phRc thng tin ny hohc c thPphthi+n trnh sCdRng thng tin lsi. BER quan trang v!i pht sOli+u h"n Voice.

vph"ng php m ho knh ta phpi pht >i m?t l`ng thng tin c sObitl!n h"n nhng sq>(t >?an ton chOng lsi cao h"n. M ho knh c thPpht hi+nv sCa lsi _tYng bit thu.V d>:Khi muOn gCi m?t bit 0 hay 1 >P>`c bpo v+ta bSxung thm ba bitnhsau:Thng tin

01

BSxung000111

GCi >i00001111

KhOi m 0000 sq>ng v!i 0 v 1111 sq>ng v!i 1. Tnl+l 1:4, bpo v+sq

xpy ra nhsau:Thu >`c : 0000 0010 0110 0111 1110QuyWt >Anh: 0 1 0 x 1

Ring cRm 0110 khng xc >Anh >`c cRthP, tr(m 0111 v 1110 >`c phthi+n l lsi.

Msi knh kiPm tra lsi >`c chia thnh m khOi v m xoZn. vm khOi,m?t sObit kiPm tra >`c bSxung vo m?t sObit thng tin nhMt >Anh. Cc bit kiPmtra chEphRthu?c vo cc bit thng tin _khOi bpn tin. vm ho xoZn, b?m hot(o ra khOi cc bit m khng chEphRthu?c vo cc bit cKa khOi bpn tin hi+n thTi>`c dAch vo b?m ho m cn phRthu?c vo cc bit cKa khOi tr!c.

M ho khOi thTng >`c sCdRng khi c bo hi+u >Anh h!ng theo khOi vsCdRng >Ppht hi+n lsi khi th*c hi+n Yu c^u t*>?ng pht ARQ. M ho xoZnlin quan nhi=u h"n >Wn sCa sai lsi. Cp hai m ny >`c sC dRng _GSM. Hai

b!c m ho >`c dng cho cptiWng v sOli+u.

Ghp xen:


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Cc lsi bit thTng xpy ra theo tYng cRm do cc chstrong pha>inh lu lmpnh h_ng nhi=u bit lin tiWp. 8P gipi quyWt hi+n t`ng lsi bit qu di ta dng

ph"ng php ghp knh xen >P tch cc bit lin tiWp cKa m?t bpn tin sao cho ccbit ny gCi >i khng lin tiWp.

Khi truy=n d$n khung 2 c thPmMt nWu khng ghp xen ton b?khOi bpntin sqmMt nhng ghp xen sq>pm bpo chEthAthXhai _tYng khOi l bAmZc lsi:

1 x 3 4 1 x 3 4 1 x 3 4 1 x 3 4

M ho knh c thPkhi phRc l(i thng tin cKa tMt cpcc khOi. vGMS b?m ho knh cung cMp 456 bit cho tYng 20ms tiWng v >*oc ghp xen >Pt(o ra cckhOi 57bit.

2.1.4. PhDi=u chEnh my thu >Wn m hnh. Knh >`c xt nhm?t b?lac v >`c kchthch b_i m?t tn hi+u biWt tr!c. So snh >^u ra v!i >^u vo ta c >p Xng xungcKa b? lac. 8p Xng xung cKa b?lac cho ta biWt >`c tn hi+u ra >Oi v!i tn hi+uvo, nhvJy ta c thPtm >`c >p Xng xung cKa knh v lJp m hnh knh khi

phn tch m?t tn hi+u thu >`c. 8p Xng xung khi khng c phpn x((a) v c m?tphpn x((b).

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4

Cc khOi bn tinghp xen

Cc khOi bn tin>`c ghp xen

M?t khung

My pht My thutOi u

Knh

(t)


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Xt nguyn l lm vi=c c@a m3t b3cn bAng: Sau khi lJp m hnh knh tasqphpi t(o ra tMt cpcc chusi bit c thPc rwi >a chng qua m hnh knh chusi>û vo m tY> nhJn >`c chusi >û ra giOng n nhMt gai l chusi nguyn thunhay chusi pht. Theo quy >Anh cKa GMS, m?t b?cn bing c^n c khpnUng xClm?t tn hi+u phpn x(trl>Wn 14,8s t"ng Xngv!i thTi gian cKa 4bit. Lc ny ngaycptn hi+u phpn x(cong bApnh h_ng b_i pha>inh raile, nhng do tn hi+u ny cm$u pha>inh >?c lJp so v!i tn hi+u >i th{ng nn n >`c lì dRng >P>(t hi+u qupcao h"n. VJy v!i cc tn hi+u phpn x(trld!i 15s n cho ta thm nUng l`ng >Pcpi t(o tn hi+u thu.

Trn th*c tW>?di chusi N thTng l!n ln phpi >`c th*c hi+n nhi=u sosnh v mMt nhi=u thTi gian tnh ton gy m?t s* chJm trl khng cho php. 8PkhZc phRc kh khUn ny ngTi ta phpi sC dRng >Wn thuJt ton Viterbi m _>khng c^n phpi thC tMt cp cc chusi. Nguyn l l khi tnh ton ta lo(i btcc tSh`p khng c khpnUng l tn hi+u vo nhT> gipm >`c sO l`ng tnh ton c^nthiWt.

2.1.5. Truy@n dbn sXv tn hi>u tD`c trnh by bing m?t tJp h`p hju h(ncc mXc >`c xc >Anh b_i sOcc bit ta c^n sCdRng >Ptrnh by m?t m$u.

vh+thOng viln thng sOchan sOmXc rTi r(c ho =256 mXc (8bit) v!i msim$u ta trnh by gi trAt"ng t*bing m?t gi trA> >`c l`ng tCho _8bit. V!itOc >? lMy m$u 8kHz ta c tOc >?bit: 8000mCu/s x 8bit = 64kb/s. Qu trnh ny>`c gai l >i=u chWxung m PCM gwm 3 b!c:

Ta >ht nhi=u knh trn cng m?t >Tng truy=n PCM (ghp knh) >Ptrnhlng ph. NWu ghp 32 knh trn m?t >Tng truy=n PCM th tOc >?bit cKa n l32x64kb/s=2,048Mb/s. ThiWt bAghp knh >i=u khiPn vi+c gn cc khe thTi gian

L`ng tC LMy m$u M ho8Tng truy=nPCM 64 kb/s


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0,1 gCi >i _khe 1,...Trong 32 knh truy=n th knh 0 dng cho >wng b?, knh 16dng cho bo hi+u cn 30 knh cn l(i dng cho tiWng tho(i. Ph^n trnh by trn lv dRv=>a thm nhJp phn chia theo thTi gian TDMA.

M?t ph"ng php khc v!i TDMA l FDMA (2a thm nhEp phn chia t6ns7)>`c dng _qupng b v tuyWn, msi knh >`c dnh cho m?t bUng t^n ring.

KG thuJt ny >`c sCdRng _h+ thOng di >?ng tSong t"ng t*, msi cu?c gai _m?t sCdRng m?t bUng t^n (hai bUng khi truy=n song cng). Sau >y l so snhgija TDMA v FDMA:

'(ng b*th+i gian:Khi sCdRng TDMA _v tuyWn, msi tr(m di >?ng sCdRng khe thTi gian Ts

cKa mnh nhng khi khopng cch gija MS v BS tUng ln gy trlthTi gian truy=ntn hi+u v trlny l!n qu th thng tin pht >i tYMS _khe Ts n sqtrng v!i tnhi+u thu >`c cKa BS t(i khe Ts n+1 cKa MS khc. 8PkiPm tra thTi gian >Wn vcc l+nh >`c gCi >Wn MS ta c qu trnh >Anh tr!c thTi gian msi khi MS dichuyPn ra xa.

M ho ti.ng:v m?t sO h+ thOng di >?ng tS ong FDMA khopng cch gija cc knh l

25kHz (NMT, TACS) v _GMS khopng cch ny bing 200kHz. So snh TDMA200kHz v FDMA 25kHz ta c hi+u qup sCdRng t^n sOnhnhau. Khi sCdRng

ph"ng php >i=u chWpha tOi thiPu Gauss (GMSK) >?r?ng bUng thng bAchiWmsq rMt l!n. 8P>pm bpo bUng t^n cho php ta gipm tOi thiPu tOc >?bit cho tYng

knh tiWng bing cch m ho tiWng (Vocodes) v m ho theo d(ng sng.M ho theo kiPu pht m Vocodes gip ta nhJn biWt >`c tiWng ni nhng

rMt tSng h`p v ta kh nhJn ra ai pht m.SC dRng m ho sng (m ho PCM 2Fng 2"u) thng tin tr*c tiWp chnh

th*c d(ng sng >`c pht >i v!i tOc >?>i hti cao v cho ta m?t chMt l`ng congrMt cao. TOc >?bit _b?m ho d(ng sng thay >Si g^n tY16kb/s >Wn 64kb/s >Oiv!i b?m ho PCM >wng >=u.

FDMA

0 1 2 3 4 5 6 7MS1

MS2 MS2 MS5

TDMA


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Hnh 2. TSchXc khung, >a khung

Ngoi ra ta cn c cc b?m ho cho php >`c m tpnhm?t s*pha tr?ngija Vocodes v m ho d(ng sng. Cc b?m ho lai ghp lMp kn chstrOng gijacc b?m ho Vecodes v d(ng sng v!i tOc >?bit tY5kb/s, chMt l`ng theo tOc>?bit. GMS sCdRng b?m ho ghp lai gai l m ho ti=n >Anh tuyWn tnh-Ti=n>Anh thTi gian di-kch thch xung >=u: b?LPC-LPT-RPE.

2.2. Nguyn t1c khi chia knh theo khe th+i gian

2.2.1. Khi ni>m knhM(ng GSM/PLMN dnh 124 sng mang song cng _dpi t^n:- 8Tng ln (MS BTS): 890 915Mhz- 8Tng xuOng (BTS MS): 935 960MhzKhopng cch gija sng mang 200Khz, trn msi sng mang th*c hi+n ghp

knh theo thTi gian Xng v!i msi khung TDMA, msi khung gwm 8 khe thTi gian(Time Slot). SOknh _GSM l 124x8(khe) =922knh.

2.2.1.1. Knh vNt lM?t khe thTi gian _ m?t t^n sO v tuyWn dnh >P truy=n tpi thng tin _

>Tng v tuyWn cKa GSM. Msi m?t knh t^n sOv tuyWn >`c tSchXc thnh cckhung TDMA di 4,62ms gwm c 8 khe thTi gian (msi khe di 577s). T(i BTS,cc khung TDMA _ cc knh t^n sO_ cp>Tng ln v >Tng xuOng >=u >`c>wng b?, tuy nhin khung >Tng ln trl3 khe so v!i khung >Tng xuOng. NhTctrlny m c thPsCdRng m?t khe thTi gian c cng sOthXt*_cp>Tng ln l$n>Tng xuOng >Ptruy=n tin bn song cng.

V=mht thTi gian, cc knh vJt l _m?t knh t^n sO>`c tSchXc theo cMu

trc khung, >a khung, siu >a khung, siu siu khung nhsau:M?t siu siu khung = 2048 siu khung = 2715648 khung (3h28 53760ms)

0 1 2 3 4 5 2042 2043 2045 2046 2047

1 siu khung = 1326 khung TDMA (6,12s)

1>a khung = 26 khung(120ms) 1 >a khung = 51 khung(235ms)

0 1 2 3 47 48 49 500 1 24 25

0 1 24 25 0 1 49 50

0 1 2 3 4 5 6 7


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1 khung = 8 khe

M?t siu siu khung >`c chia thnh 2048 siu khung v!i thTi gian l 6,12s. Siukhung l(i >`c chia thnh cc >a khung, c hai lo(i >a khung:

- 8a khung 26 khung chXa 26 khung TDMA. 8a khung ny >`c sCdRng>Pmang TCH (v SACCH c?ng FACCH). 51 >a khung ny t(o nn m?t siukhung.

- 8a khung 51 khung chXa 51 khung TDMA. 8a khung ny sCdRng >Pmang BCH v CCH. 26 >a khung ny t(o nn m?t siu khung.

2.2.1.2 Knh logicCc knh logic >`c >hc trng b_i thng tin truy=n gija BTS v MS. Knhlogic >`c chia lm hai lo(i:Knh lDu thng (TCH):mang tiWng >`c m ho hohc sOli+u cKa ngTisCdRng, gwm hai d(ng knh:- Bm hay knh ton tOc TCH mang thng tin _tOc >?22,8Kbps.- Lm hay knh bn tOc TCH mang thng tin _tOc >?11,4Kbps.

Cc knh 5i@u khiYn:mang tn hi+u bo hi+u hay sOli+u >wng b?, gwm balo(i sau:

- Cc knh qu%ng b (BCH):+ Knh hi+u chEnh t^n sO(FCCH): mang thng tin >Phi+u chEnh t^nsOcKa MS.

+ Knh >wng b?(SCH): mang thng tin >P>wng b?khung (sOkhungTDMA) cKa MS v nhJn d(ng BTS (BSIC).

+ Knh >i=u khiPn qupng b (BCCH): pht qupng b thng tin chungtrn c"s_m?t knh cho m?t BTS.

- Cc knh 2i"u khiGn ring (DCCH):+ Knh >i=u khiPn ring >Xng m?t mnh (SDCCH): >`c sCdRng >P

bo hi+u h+thOng khi thiWt lJp m?t cu?c gai tr!c khi Mn >Anh m?t TCH. Knh>Tng ln/xuOng, >iPm >Wn >iPm.

+ Knh >i=u khiPn lin kWt chJm (SACCH): lin kWt v!i m?t TCHhay m?t SDCCH, l knh sOli+u lin tRc mang thng tin lin tRc nhcc thng

bo >o >(c tYtr(m di >?ng v=cTng >?tn hi+u thu tY hi+n thTi v cc lncJn. Thng tin ny c^n cho chXc nUng chuyPn giao. Knh ny cong >`c sCdRng>P>i=u chEnh cng suMt cKa MS v >P>wng b?thTi gian. Knh >Tng ln/xuOng,>iPm >Wn >iPm.


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+ Knh >i=u khiPn lin kWt nhanh (FACCH): l knh lin kWt v!iTCH. FACCH lm vi+c _chW>?lMy cZp bing cch thay >Si lu l`ng tiWng haysOli+u bing bo hi+u.

- Cc knh 2i"u khiGn chung (CCCH):+ Knh tm gai (PCH): >`c sCdRng >Ptm gai MS.

+ Knh thm nhJp ng$u nhin (RACH): MS sCdRng knh ny >Pyu cû dnh SDCCH hohc >PtrplTi tm gai, hohc >Pthm nhJp khi kh_i >û,hohc >Ung k cu?c gai MS.

+ Knh cho php thm nhJp (AGCH): >`c sCdRng >Pdnh m?tSDCCH hay tr*c tiWp m?t TCH cho m?t MS.

2.2.2. CUm

CRm l m$u thng tin _m?t khe thTi gian trn knh TDMA, cX8 khe thTigian m?t l^n _knh TDMA >`c pht >i th c 1 cRm cKa m?t lo(i thng tin. - C>m bnh th(Ing ( NB):mang thng tin _TCH v cc knh >i=u khiPn

trYRACH, SCH v FCCH.

+ Cc bit >`c mJt m gwm 57bit sOli+u hay tiWng v m?t cTlMy cZp.+ Chusi h!ng d$n l m$u bit biWt tr!c >Pb?cn bing c thPthnh lJp

m?t m hnh knh.

+ Cc bit >ui TB lun l 0,0,0 gip b?cn bing xc >Anh >û v cuOim$u bit.

+ Khopng bpo v+GP l m?t khopng trOng cho php my pht dAch ln haydAch xuOng trong gi!i h(n do khuyWn nghAGMS qui >Anh.

- C>m hi=u ch:nh t6n s7(FB):8i=u chEnh t^n sOcKa MS, n t"ng >"ngsng mang cha bA>i=u chW. Lhp l(i cKa m?t cRm gai l FCCH.

- C>m 2Fng b3(SB): Dng >P>wng b?thTi gian cKa MS

TB3

Cc bit >`c mJt m58

Chusi h!ng d$n26

Cc bit >`c mJt m58

TB3

GP8,25

0,577 ms156,25 bit

TB3

TB3

GP8,25

0,577 ms156,25 bit

Cc bit cO>Anh 0142

TB3

Cc bit >`c mJt m39

Chusi >wng b?64

Cc bit >`c mJt m39

TB3

GP8,25


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+ KhOi >wng b?di dldng nhJn biWt v mang thng tin sOkhungTDMA cng m nhJn d(ng tr(m c"s_BS. Lhp l(i cKa cRm gai l SHC.

SOkhung TDMA gip MS biWt lo(i knh lgc no >ang >`c truy=n _knh >i=u khiPn. M?t chu trnh >nh sOkhung l 3,5 giTv!i msi khung TDMA

thTi gian l 6,615ms.

- C>m thm nhEp (AB):SCdRng >Pthm nhJp ng$u nhin v c GP >Pdnh cho pht cRm tYtr(m di >?ng.

- C>m gi%: 8`c pht >i tYBTS v khng chXa thng tin khun m$u giOng

nhcRm bnh thTng v!i cc bit mJt m >`c thay b_i cc bit hsn h`p c m$u bitxc >Anh.

2.2.3. Chia knh logic theo khe th\i gian

Xt m?t BTS v!i n sng mang (song cng) k hi+u l C0, C1,, Cn, msisng mang c 8 khe thTi gian l^n l`t l Ts0, Ts1,, Ts7.

Cc knh logic 2(Kc sLp x.p MC0nh(sau:- Cc knh >i=u khiPn BCCH, FCCH, SCH, PCH, AGCH >`c sZp xWp

trn Ts0>Tng xuOng, cn knh RACH _Ts0>Tng ln. Chu kklhp 51 Ts.

- Ts1>`c sCdRng >PsZp xWp cc knh >i=u khiPn ring SDCCH vSACCH, chu kklhp 102 Ts.- TYTs2>Wn Ts7l cc knh lu thng TCH, chu kklhp 26Ts.Cc sng mang khc (C1 Cn):chE>`c sCdRng cho knh lu l`ng TCH,

nghma l Ts0>Wn Ts7>=u l TCH.

0 1 2 .. 7 0 1 2 .. 7 0 1 2 ..

F S B C F S C C F S C C F S C CBCH CCCH >Tng xuOng

Hnh 3. Ghp cc BCH v CCCH _Ts0

F (FCCH): t(i >y tr(m di >?ng >wng b?t^n sOcKa mnhS (SCH): tr(m di >?ng >ac sOkhung TDMA v BSICB (BCCH): tr(m di >?ng >ac cc thng tin chung v= ny

Cc khungTDMA

TB3

Chusi >wng b?41

Cc bit >`c mJt m36

TB3

GP8,25


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C (CCCH): c thPtm gai m?t tr(m di >?ng v dnh m?t SDCCH

0 1 2 .. 7 0 1 2 .. 7 0 1 2 ..

R R R R R R R R R ..RACH >Tng ln

Hnh 4. Ghp RACH _Ts0

Cc Ts 2-7 cKa C0sCdRng cho cc knh lu thng TCH >`c sZp xWp _ccknh vJt l nhhnh 5. Hnh vqTS2, >Tng xuOng _C0. Thng tin _Ts 2 t(othnh m?t TCH.

TMt cpc 26 Ts. Sau Ts >PtrOng l(i bZt >^u l(i.T (TCH): chXa tiWng hay sOli+u >`c m ho.

A (SACCH): nim _Ts 13, l bo hi+u >i=u khiPn.

0 1 2 . 7 0 1 2 . 7 0 1 2 .

T T T T T A T T . . .

Hnh 5. Ghp TCH

CMu trc >Tng ln cong t"ng t*nh>Tng xuOng. 8iPm khc nhau duynhMt l s*dAch v=mht thTi gian, Ts2 _>Tng xuOng khng xpy ra _cng thTi giannhTs2 _>Tng ln. ThTi gian dAch l ba khe thTi gian.

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0 1 45Mhz

0 10 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

>TngxuOn

>Tngln

SOkhung TDMA

51 khung lin tiWp

Cc khungTDMA

26 TSTCH >TngxuOng


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Hnh 6. DAch gija TCH >Tng ln v xuOng.

CH"NG 3. NGUYN TdC S-DeNG TgN S`CC TR!NG HhP V THiTeC THNG TIN

3.1. Nguyn tjc sCdUng tWn sXtheo chia

3.1.1. SCdUng tWn sXThng tin di >?ng bAh(n chWv= t^n sO, v vJy sCdRng hi+u qupt^n sOvtuyWn l yWu tOquan trang nhMt >PphRc vRcng nhi=u thu bao cng tOt. NgTi ta> >a ra cc ph"ng php sau >PsCdRng hi+u qupt^n sO:

- Gipm >?r?ng bUng t^n cKa m?t knh cng nhi=u cng tOt.- SCdRng hi+u qupcc knh v tuyWn bing cch t(o ra khpnUng cho nhi=u

>^u cuOi sCdRng chung nhi=u knh v tuyWn trong m?t v tuyWn.


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- SCdRng l(i t^n sO> dng trong m?t vo m?t v tuyWn bing cch gijcc ny cch nhau l!n h"n m?t khopng cch nhMt >Anh.

- C*c tiPu ho kch th!c .

3.1.2. S]ti sCdUng tWn sXtrn m3ng

3.1.2.1. C`c gi!i h(n b_i >i=u ny nhi=u h"n

nhi=u tYtn hi+u trTng ngoi. M?t vMn >=trong thiWt kWh+thOng Cellular l >i=ukhiPn nhilu ny >Wn mXc >? chMp nhJn >`c. N c thP lm >`c bing s*>i=ukhiPn khopng cch ti sCdRng knh. Khi khopng cch ny cng l!n suy ra mXc >?nhilu cng t.

MXc >?tn hi+u thu >`c C cKa sng mang mong muOn sqcao h"n mXc >?nhilu I cKa tMt cpcc knh v mXc >?nhilu A cKa cc knh ln cJn. S*ho(t >?ngcKa tn hi+u thu mong muOn sqcao h"n s*ho(t >?ng cKa tn hi+u phpn x(R.

Nhjng gi trA>`c tiWn cCh+thOng GSM l : C/A> -9 dB ; C/I10dB.C/A: Khi 1 t^n sO>`c ti sCdRng nhm hnh 3/9 th m?t sOnUng l`ng

cKa t^n sO ln cJn sq lat ra ngoi phRc vRv l nguyn nhn nhilu. S*lin h+gija tn hi+u nhilu v tn hi+u hju ch l tEsOC/A.

3.1.2.2. Mbu sCdUng l3i tWn sX

SCdRng l(i t^n sOl sCdRng cc knh v tuyWn _cng m?t t^n sOmang >PphKcho cc vng >Aa l khc nhau. Cc vng ny phpi >`c cch nhau _c*ly >Kl!n >Pmai nhilu giao thoa >wng knh chMp nhJn >`c.

NWu ton b?sOknh quy >Anh N >`c chia thnh F nhm th msi nhm sqchXa N/F knh. V tSng sOknh N l cO>Anh nn sOnhm t^n sOF nhth"n sqd$n>Wn nhi=u knh h"n _m?t nhm v _m?t >i tr(m. V vJy vi+c gipm sOl`ngcc nhm t^n sOsqcho php msi >i tr(m tUng lu l`ng nhTvJy gipm tSng sOcc >i tr(m c^n thiWt cho tpi lu l`ng >Anh tr!c. Tuy nhin gipm sOl`ng ccnhm t^n sOv gipm c*ly >wng knh sqd$n >Wn phn bOC/I trung bnh thMp h"n_h+thOng.

C ba kiPu m$u sCdRng l(i t^n sOphSbiWn l: 7/21, 4/12 v 3/9 sCdRngcho cc tr(m gOc c anten pht 3 h!ng, msi h!ng dnh cho m?t v gc


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ph"ng vAphn cch nhau 1200. Msi sCdRng cc anten pht 600v hai anten thuphn tJp 600cho m?t gc ph"ng vA. Msi >`c xMp xEho l hnh lRc gic, cbn knh R (bing c(nh hnh lRc gic v bing 1/3 khopng cch gija cc tr(m).

Ta coi lu l`ng phn bO >wng nhMt _ cc . Bnh thTng kch th!c >`c xc >Anh nhl khopng cch gija hai > tr(m ln cJn.

S">w3/9 sCdRng cc nhm 9 t^n sO, trong m?t m$u sCdRng l(i t^n sO3>i tr(m:

Hnh 6. M$u 3/9

S">w4/12 sCdRng cc nhm 12 t^n sO, trong m?t m$u sCdRng l(i t^n sO4 >i:


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Hnh 8. M$u 4/12S">w7/21 sCdRng cc nhm 21 t n sO, trong m?t m$u sCdRng l(i t^n sO

7 >i nhsau:

Hnh 7. M$u 7/21

Trong th*c tW, do s*tUng tr_ng dung l`ng khng ngYng trong m?t no> t!i mXc chMt l`ng phRc vR gipm st qu mXc, ngTi ta phpi th*c hi+n vi+cchia tch thnh cc nhth"n. V!i chng, ngTi ta dng cng suMt nhth"n vm$u sCdRng l(i t^n sO>`c dng _tnl+xch nhth"n.


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Thng thTng cc cu?c gai c thPkhng xong trong m?t (1 cell), v vJyh+ thOng thng tin di >?ng tWbo phpI c khpnUng >i=u khiPn, chuyPn m(ch >PchuyPn giao cu?c gai tY ny sang khc m cu?c gai >`c chuyPn giao khng

bApnh h_ng g. Yu c^u > lm cho m(ng di >?ng c cMu trc khc bi+t v!i ccm(ng cO>Anh.

3.2. Cc trD\ng hVp v thOtUc thng tin

3.2.1. T[ng quanTr!c khi khpo st cc thK tRc thng tin khc nhau, hy khpo st cc tnh

huOng >hc bi+t cKa 1 PLMN c tMt cpcc thu bao di >?ng, v thWta quan st MS _m?t sOtnh huOng sau:

-TLt my:M(ng sqkhng thPtiWp cJn >Wn my v MS khng trplTi thng bo tm gai.

N sqkhng bo cho h+thOng v=vng >Anh vA(n.u c) v MS sq>`c coi l rTi

m(ng. - MS bEt my, tr,ng thi rNi:H+thOng c thPtm gai MS thnh cng, MS >`c coi l nhJp m(ng. Trong

khi chuyPn >?ng, MS lun kiPm tra ring n >`c nOi >Wn m?t knh qupng b >`cthu pht tOt nhMt. Qu trnh ny >`c gai l lu >?ng(Roaming). MS c^n thng

bo cho h+thOng v=cc thay >Si vng >Anh vA, qu trnh ny >`c gai l cJp nhJtvAtr.

- MS bEn:M(ng v tuyWn c m?t knh thng tin (knh ti.ng) dnh cho luwng sO li+u

t!i v tYMS trong qu trnh chuyPn >?ng MS phpi c khpnUng chuyPn >Wn m?t

knh thng tin khc. Qu trnh ny >`c gai l chuyPn giao (Handover). 8PquyWt>Anh chuyPn giao h+thOng phpi diln gipi thng tin nhJn >u`c tYMS v BTS. Qutrnh ny >`c gai l >Anh vA.

3.2.2. LDu 56ng v cNp nhNt vAtr:Coi ring MS _ tr(ng thi tch c*c, rsi v >ang chuyPn >?ng theo m?t

ph"ng lin tRc MS >`c kho >Wn m?t t^n sOv tuyWn nhMt >Anh c CCCH vBCH _TSo. Khi MS rTi xa BTS nOi v!i n cTng >?tn hi+u sqgipm. _m?t thTi>iPm no > khng xa bin gi!i l thuyWt gija hai ln cJn nhau cTng >? t!imXc m MS quyWt >Anh chuyPn >Wn m?t t^n sOm!i thu?c m?t trong cc ln cJnn. 8Pchan t^n sOtOt nhMt n lin tRc >o cTng >?tn hi+u cKa tYng t^n sOtrong

sOt^n sOnhMt >Anh cKa ln cJn. ThTng MS phpi tm >`c t^n sOBCH/CCCHtYBTS c cTng >?tn hi+u tOt h"n t^n sOco. Sau khi t*kho >Wn t^n sOm!i ny,MS tiWp tRc nhJn thng bao tm gai cc thng bo qupng b chYng no tn hi+u cKat^n sOm!i v$n >K tOt. QuyWt >Anh vi+c thay >Si t^n sOBCH/CCCH sq>`c th*chi+n m khng c^n thng bo cho m(ng. Nghma l m(ng mht >Mt khng tham giav qu trnh ny.


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KhpnUng chuyPn >?ng v >Anh >wng thTi v!i vi+c thay >Si nOi thng MS _giao tiWp v tuyWn t(i thoYi >iPm c^n thiWt >P>pm bpo chMt l`ng thu >`c gai llu >?ng Roaming.

- Khi MS chuyGn 23ng 2.n gi5a hai cell thu3c 2 BTS khc nhau:Ta biWt ring MS khng h=biWt cMu hnh cKa m(ng chXa n. 8PgCi cho MS

thng tin v=vAtr chnh xc cKa n h+thOng gCi >i nhJn d(ng vng >Anh vA(LAI)lin tRc _giao tiWp v tuyWn bing BCCH.

Khi >i vo cell thu?c BSC khc MS sqnhJn thMy vng m!i bing cch thuBCCH. V thng tin v=vAtr c t^m quan trang l!n nn m(ng phpi thng bo v=s*thay >Si ny, _>i+n tho(i di >?ng qu trnh ny >`c gai l >Ung k crng bXc.MS khng cn cch no khc l phpi cOgZng thm nhJp vo m(ng >PcJp nJt vAtrcKa mnh _MSC/VLR. Qu trnh ny >`c gai l cJp nhJt vAtr.

Sau khi > pht vAtr m!i cKa mnh ln m(ng, MS tiWp tRc chuyPn >?ng _trong vng m!i nh> m tp_trn.

- Khi MS chuyGn 23ng gi5a hai vng ph>c v>khc nhau:

Trong trTng h`p c m?t cu?c gai vo cho MS, vi+c chuyPn tYm?t vngphRc vRMSC/VLR ny sang m?t vng phRc vRMSC/VLR khc c nghma l tuyWnthng tin >i qua m(ng cong sqkhc. 8Ptm >`c >Anh tuyWn >ng, h+thOng phpitham khpo b?ghi >Anh vAthTng tr HLR v thWMSC/VLR sqphpi cJp nhJt HLRv=vAtr cKa MSC/VLR cho MS cKa chng ta.

Qu trnh cJp nhJt vAtr nhsau:

Sau khi cJp nhJt vAtr thnh cng _HLR h+thOng sqhunbtvAtr co, HLRthng bo hunbtvAtr cho tSng >i MSC/VLR co>Pxo vAtr cocKa MS c linquan.

3.2.3. ThOtUc nhNp m3ng 5Sng k lWn 5WuKhi MS bJt my n sqqut giao tiWp v tuyWn >Ptm ra t^n sO>ng, t^n sO

m MS tm kiWm sq chXa thng tin qupng b cong nh thng tin tm gai

MSCHLRVLR

MSCVLR

(5) xo vAtr

(6) tiWp nhJn xo

(2) Yu c^u cJpnhJt vAtr

(3) tiWp nhJn vAtr(1) Yu c^u nhJt vA

tr

(4) Cng nhJn cJpnhJt vAtr


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BCH/CCCH c thPc. MS t*kho >Wn t^n sO>ng nhTvi+c hi+u chEnh t^n sOthuv thng tin >wng b?

V >y l l^n >û MS sCdRng nn ph^n m(ng chAu trch nhi+m xCl thngtin t!i / tYMS hon ton khng c thng tin v=MS ny, MS khng c chEthAnov= nhJn d(ng vng >Anh vAm!i . Khi MS cOgZng thm nhJp t!i m(ng v thng

bo v!i h+ thOng ring n l MS m!i _ vng >Anh vA ny bing cch gCi >i m?tthng bo CJp nhJt vAtr m(ng >Wn MSC/VLR.

TYgiT tr_>i MSC/VLR sqcoi ring MS ho(t >?ng v >nh dMu trTng djli+u cKa MS ny bing 1 cTnhJp m(ng cTny lin quan >Wn IMSI.

3.2.4. ThOtUc r\i m3ngThKtRc rTi m(ng lin quan >Wn IMSI. ThKtRc rTi m(ng cKa IMSI cho php

thng bo v!i m(ng ring thu bao di >?ng sqtZt nguwn , lc ny tm gai MS bingthng bo tm gai sqkhng xpy ra.

M?t MS _ tr(ng thi ho(t >?ng >`c >nh dMu l > nhJp m(ng. Khi tZt

nguwn MS gCi thng bo cuOi cng >Wn m(ng, thng bo ny chXa yu cû thKtRcrTi m(ng. Khi thu >`c thng bo rTi m(ng MSC/VLR >nh dMu cTIMSI > rTim(ng t"ng Xng.

3.2.5. Tm gliCu?c gai >Wn MS >*oc >Anh tuyWn >Wn MSC/VLR n"i MS >Ung k. Khi >

MSC/VLR sq gCi >i m?t thng bo tm gai >Wn MS, thng bo ny >`c phtqupng b trn ton b?vng >Anh vALA nghma l tMt cpcc BTS trong LA sqgCithng bo tm gai MS. Khi chuyPn >?ng _LA v nghe thng tin CCCH MS sqnghe thMy thng bo tm gai v trplTi ngay lJp tXc.

3.2.6. Gli taMS

GipsCMS rsi v muOn thiWt lJp m?t cu?c gai, thu bao ny sqquay tMt cpcc chjsOcKa thu bao bAgai v bZt >û thKtRc ny bing cch Mn phm pht .Khi ny MS gCi >i m?t thng bo >û tin >Wn m(ng bing CCCH >Pyu cû thmnhJp . Tr!c hWt MSC/VLR sqginh ring cho MS m?t knh ring , kiPm tra thPlo(i cKa thu bao bAgai v >nh dMu thu bao ny _tr(ng thi bJn . NWu thu baogai >`c php sCdRng m(ng MSC/VLR sq cng nhJn yu cû thm nhJp . BygiTMS sqgCi >i m?t thng bo >PthiWt lJp cu?c gai, tuktheo thu bao bAgai l cO>Anh hay di >?ng sOcKa n sq>`c phn tch tr*c tiWp _MSC/VLR hohc gCi >Wnm?t tSng >i chuyPn tiWp cKa m(ng PSTN cO>Anh . Ngay khi >Tng nOi >Wn thu

bao bAgai > s|n sng thng bo thiWt lJp cu?c gai sq>`c cng nhJn, MS cong sq>`c chuyPn >Wn m?t knh thng tin ring. By giT tn hi+u cuOi cng sq l s*kh{ng >Anh thu bao.

3.2.7. Gli 5^n thu bao MSGipsCc m?t thu bao A thu?c m(ng cO>Anh PSTN yu cû thiWt lJp cu?c

gai v!i thu bao B thu?c m(ng di >?ng.


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- Thu bao A quay m n"i nhJn trong n!c >P>(t t!i vng GSM/PLMN.NOi thng >`c thiWt lJp tYtSng >i n?i h(t cKa thu bao A >Wn GMSC cKa m(ngGSM/PLMN.

- Thu bao A quay sOcKa thu bao B, sOthu bao >`c phn tch _GMSC.Bing chXc nUng hti >p GMSC gCi MSISDN cng v!i yu c^u v= sO lu >?ng

(MSRN) >Wn b?ghi >Anh vAthTng tr (HLR)- HLR dAch sO thu bao cKa MS >`c quay vo nhJn d(ng GSM/PLMN:

MSISDN IMSI- HLR chEcho MS vng phRc vR v gCi IMSI cKa MS >Wn VLR cKa vng

phRc vR>wng thTi yu c^u v=MSRN.- VLR sq t(m thTi gn sO lu >?ng MSRN cho thu bao bAgai v gCi n

ng`c tr_v=HLR, HLR sqgCi n v=tSng >i cSng GSMC.- Khi nhJn >`c MSRN >ng tSng >i GMSC sqc khpnUng thiWt lJp cu?c

gai >Wn vng phRc vRMSC/VLR n"i thu bao B hi+n >ang c mht.- VLR sq chE cho thu bao ny vng >Anh vA (LAI) _ giai >o(n qu trnh

thiWt lJp cu?c gai h+thOng muOn ring thng bo tm gai thu bao bAgai >ac phtqupng b trn vng phK sng cKa tMt cp cc cKa vng >Anh vA ny. V vJyMSC/VLR gCi thng bo tm gai >Wn tMt cpcc BTS trong vng >Anh vA.

- Khi nhJn >`c thng tin tm gai, BTS sqpht n ln >ng v tuyWn _knh tm gai PCH. Khi MS _tr(ng thi rsi v nghe _knh PCH cKa m?t trongsO cc thu?c vng >Anh vA LA, n sq nhJn thng tin tm gai , nhJn biWt d(ngIMSI v gCi trplTi v=thng bo tm gai.

- Sau cc thKtRc v=thiWt lJp cu?c gai v sau khi > gn cho m?t knh thngtin cu?c gai ni trn dd`c nOi thng >Wn MS _knh v tuyWn.

3.2.8.

Cu6c gli 5ang ti^n hnh, 5Anh vABy giTta xem xt >i=u g sqxpy ra khi m?t tr(m di >?ng _tr(ng thi bJn

chuyPn >?ng xa d^n BTS m n nOi >Wn _>Tng v tuyWn. Nhta vYa thMy MS sCdRng m?t knh TCH ring >Ptrao >Si sOli+u/tn hi+u cKa mnh v!i m(ng khi cngrTi xa BTS, suy hao >Tng truy=n cong nhpnh h_ng cKa phadinh sqlm htngchMt l`ng truy=n d$n v tuyWn sO. Tuy nhin h+ thOng c khp nUng >pm bpochuyPn sang BTS bn c(nh.

Qu trnh thay >Si >Wn m?t knh thng tin m!i trong qu trnh thiWt lJpcu?c gai hay _tr(ng thi bJn >`c gai l chuyPn giao. M(ng sqquyWt >Anh v=s*thay >Si ny. MS gCi cc thng tin lin quan >Wn cTng >?tn hi+u v chMt l`ngtruy=n d$n >Wn BTS qu trnh ny >`c gai l cJp nhJt. MS v m(ng c khpnUngtrao >Si thng tin v=bo hi+u trong qu trnh cu?c gai >Pc thP>wng b?chuyPnvng. Trong qu trnh h?i tho(i _knh TCH dnh ring, MS phpi tJp trung lnTCH ny v thWkhng thPm?t knh khc dnh ring cho bo hi+u. M?t l do khcnja l sO l`ng knh c h(n nn h+ thOng khng sC dRng 2 knh cho cng m?th!ng, vi+c tS chXc truy=n d$n sO li+u trn knh TCH sao cho cu?c ni chuy+ncong nh thng tin v=bo hi+u >`c gCi >i trn 1 knh. Luwng sO li+u sq>`c


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pht >i theo m?t trnh t*chnh xc>PcpMS l$n BTS c thPphn bi+t gija cu?cni chuy+n v cc thng tin bo hi+u.

By giTta quay l(i vi+c >Anh vA, tr!c hWt BTS sqthng bo cho MS v=ccBTS ln cJn v cc t^n sOBCH/CCCH. nhTthng tin ny MS c thP>o cTng >?tn hi+u _ cc t^n sOBCH/CCCH cKa tr(m gOc ln cJn, MS >o cp cTng >? tn

hi+u l$n chMt l`ng truy=n d$n _TCH bJn cKa mnh. TMt cpcc kWt qup>o ny>`c gCi >Wn m(ng >Pphn tch su h"n. CuOi cng BTS sqquyWt >Anh chuyPnvng. BSC sqphn tch cc kWt qup>o do BTS th*c hi+n _TCH bJn . Tm l(iBSC sqgipi quyWt 2 vMn >=:

+ Khi no c^n th*c hi+n chuyPn vng+ Phpi th*c hi+n chuyPn vng t!i BTS noSau khi >nh gi chnh xc tnh huOng v bZt >û qu trnh chuyPn vng,

BSC sq chAu trch nhi+m thiWt lJp m?t >Tng nOi thng >Wn BTS m!i. C cctrTng h`p chuyPn vng sau:

- ChuyGn giao trong vng 1 BSC:v trTng h`p ny BSC phpi thiWt lJp m?t >Tng nOi >Wn BTS m!i, dnhring m?t TCH cKa mnh v ra l+nh cho MS phpi chuyPn >Wn 1 t^n sOm!i >wngthTi cong chE ra m?t TCH m!i. Tnh huOng ny khng >i hti thng tin gCi >Wn

ph^n cn l(i cKa m(ng. Sau khi chuyPn giao MS phpi nhJn >`c cc thng tin m!iv cc ln cJn. NWu nhvi+c thay >Si >Wn BTS m!i cong l thay >Si vng >AnhvAth MS sqthng bo cho m(ng v=LAI m!i cKa mnh v yu cû cJp nhJt vAtr.

- ChuyGn giao gi5a hai BSC khc nhau nh(ng cng m3t MSC/VLR:TrTng h`p ny cho thMy s* chuyPn giao trong cng m?t vng phRc vR

nhng gija hai BSC khc nhau. M(ng can thi+p nhi=u h"n khi quyWt >Anh chuyPngiao. BSC phpi yu cû chuyPn giao tY MSC/VLR. Sau > c m?t >Tng nOithng m!i (MSC/VLR BSC m!i BSC m!i) phpi >`c thiWt lJp v nWu cTCH rsi, TCH ny phpi >`c dnh cho chuyPn giao. Sau > khi MS nhJn >`clnh chuyPn >Wn t^n sOm!i v TCH m!i. Ngoi ra sau khi chuyPn giao MS >`cthng bo v=cc ln cJn m!i. NWu vi+c ny thay >Si BTS >i cng v!i vi+c thay>Si vng >Anh vAMS sqgCi >i yu cû cJp nhJt vAtr trong qu trnh cu?c gai haysau cu?c gai.

- ChuyGn giao gi5a hai vng ph>c v>MSC/VLR:

8y l trTng h`p chuyPn giao phXc t(p nhMt nhi=u tn hi+u >`c trao >SinhMt tr!c khi th*c hi+n chuyPn giao.Ta sq xt 2 MSC/VLR. Gai MSC/VLR co (tham gia cu?c gai tr!c khi

chuyPn giao) l tSng >i phRc vRv MSC/VLR m!i l tSng >i >ch. TSng >i cosq gCi yu cû chuyPn giao >Wn tSng >i >ch sau > tSng >i >ch sq>pm nhJnvi+c chuun bAnOi ghp t!i BTS m!i. Sau khi thiWt lJp >Tng nOi gija hai tSng >itSng >i cosqgCi >i l+nh chuyPn giao >Wn MS.


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CH"NG 4. CC DmCH VeCiA GSM4.1. DAch vUtho3i

L dAch vRquan trang nhMt cKa GSM. N cho php cc cu?c gai hai h!ngdiln ra gija ngTi sCdRng GSM v!i thu bao bMt kk_m?t m(ng >i+n tho(i nichung no. TOc >?truy=n tho(i trong GSM l 13kbps.

DAch vRcu?c gai khun l m?t lo(i dAch vRkhc bZt nguwn tYdAch vRtho(i.N cho php ngTi dng c thPlin l(c v!i cc dAch vRkhun cMp nhcpnh st haycXu hopm c thPc hay khng c SIM card trong my di >?ng.

4.2. DAch vUsXli>u

GSM >`c thiWt kW>P>a ra rMt nhi=u dAch vRsOli+u. Cc dAch vRsOli+u>`c phn bi+t v!i nhau b_i ngTi sCdRng ph"ng ti+n (ngTi sCdRng cc m(ng>i+n tho(i PSTN, ISDN,), b_i bpn chMt cc luwng thng tin >û cuOi (dj li+uth, fax, videotex, teletex), b_i ph"ng ti+n truy=n d$n (gi hay m(ch, >wng b?hay khng >wng b?) v b_i bpn chMt thiWt bA>û cuOi.

TOc >?truy=n sOli+u trn m(ng GSM l 9,6kbps.

4.3. DAch vUnhjn tin ngjn SMSL m?t lo(i dAch vRsOli+u. DAch vRnhZn tin ngZn SMS cho php cc thu

bao GSM gCi cho nhau cc bpn tin chjdi khng qu 160 k t*.C thPsCdRng m?t trung tm dAch vR>Pm?t thu bao >ac bpn tin >Wn >.

Sau > bpn tin sq>`c pht >Wn thu bao. NWu thu bao _ngoi vng phKcKa h+thOng hay tZt nguwn, bpn tin sq>`c lu gijv gCi >I khi thu bao l(i s|n sng.C thPthu hay gCi >i cc thng bo ngZn _tr(ng thI rsi hay trong qu trnh cu?cgai.

4.4. DAch vUWap

DAch vRWap >`c bZt >û xy d*ng v triPn khai l^n >û tin cch >y banUm ( vo gija nUm 1997). DAch vR giao thXc Xng dRng khng >y (Wap) ngynay > tr_ nn phS biWn. Tiu ch cKa dAch vR rMt >"n gipn: cho php thu bao

dng >i+n tho(i di >?ng, my nhZn tin hohc nhjng thiWt bAviln thng khc c hstr Wap c thPtruy cJp m?t cch c gi!i h(n vo cc trang wed >Pxem thng tinv=thAtrTng chXng khon, xem tin tXc, gCi v nhJn email v.v

Mhc d Wap sC dRng cc cng ngh+ v khi ni+m tY thW gi!i wed vInternet nhng cc thiWt bAWap khng thP truy cJp tr*c tiWp vo cc nguwn tinguyn wed trn Internet m phpi nhTqua Wap gateway.


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4.5. Cc dAch vUm;i cOa GSM 2,5G

CuOi nUm 2003 cc nh cung cMp dAch vR>i+n tho(i di >?ng _Vi+t Nam >>a ra hai dAch vRm!i trn n=n GSM 2,5G l dAch vRv tuyWn gi chung (GPRS)v nhZn tin >a ph"ng ti+n (MMS).

D0ch v>v tuy.n gi chung (GPRS: General Packet Radio Service):

GPRS l dAch vRtruy=n dj li+u chuyPn m(ch gi >`c pht triPn trn n=ntpng cng ngh+GSM, cho php ngTi dng c thPchuyPn cc gi djli+u tOc >?cao qua my di >?ng. Do vJy GPRS sq l n=n tpng cho vi+c pht triPn cc XngdRng th"ng m(i di >?ng v dAch vR MMS, truy cJp WAP-Internet tOc >? cao.GPRS cho php truy=n djli+u c thP>(t t!i 171,2kbps.

D0ch v>nhLn tin 2a ph(*ng ti=n (MMS: Multimedia Messaging Service):DAch vR nhZn tin >a ph"ng ti+n MMS cho php nhjng ngTi dng >i+n

tho(i di >?ng c thPtrao >Si nhjng bXc pnh tmnh (JPG) hohc cc hnh >?ng (GIF),m thanh hohc giang ni, nhjng >o(n video (Streaming video) v vUn bpn ln >Wn1000 k t*. V!i dAch vRMMS, cc tin nhZn khng chE>`c gCi gija cc my >i+n

tho(i di >?ng m cn tYmy >i+n tho(i di >?ng gCi >Wn email v ng`c l(i.


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K_T LU2N

M(ng thng tin di >?ng sO> v >ang pht triPn hWt sXc nhanh chng. Ncng cc dAch vRkhc > gp m?t ph^n khng nhttrong cng cu?c hi+n >(i m(ngviln thng Vi+t Nam. V vJy vi+c nghin cXu m(ng thng tin di >?ng l hWt sXcc^n tht.

Tuy nhin >y l m?t mpng >= tI l!n v v!i thTi gian th*c tJp h"n m?tthng nn ti chEm!i dYng _mXc >=cJp tSng quan. Ti hy vang sqpht triPn >=ti ny r?ng h"n trong >w n tOt nghi+p v!i trang tm vo cc dAch vRm!i cKaGSM 2,5G.

M?t l^n nja ti xin by ttlng biWt "n su sZc t!i TS. Ph(m Cng Hng vton thPcc kGst(i phng kGthuJt cng ty VMS > gip >rti hon thnh bpn

bo co ny.


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PHeLeC: CC ToVI_T TdT

AB Access Burst CRm truy nhJpAGCH Access Grant Channel Knh cho php truy nhJpAMPS Advanced Mobile Phone

SystemH+thOng >i+n tho(i di >?ngtin tiWn

ARQ Automatic Repeat Request Yu c^u lhp l(i t*>?ngAUC Authentication Center Trung tm nhJn th*cBCCH Broadcast Control Channel Knh >i=u khiPn qupng bBCH Broadcast Channel Knh qupng bBER Bit Error Rate TnsObit lsiBIEBSC Base Station Controller B?>i=u khiPn tr(m gOcBSIC Base Station Identity Code M nhJn d(ng tr(m gOcBSS Base Station System H+thOng tr(m gOcBTS Base Transceiver Station Tr(m thu pht gOcC/A Carrier to adjacent ratio TnsOsng mang trn sng

ln cJn

C/I Carrier to interference ratio TnsOsng mang trn nhiluC/R Carrier to reflection ratio TnsOsng mang trn sng

phpn x(

CCCH Common Control Channel Knh >i=u khiPn chungCCITT International Telegraph &

Telephone ConsultativeCommittee

Unban t vMn quOc tWv=>i+ntho(i v >i+n bo

CSPDN Circuit Switched PublicData Network

M(ng sOli+u cng c?ngchuyPn m(ch knh

DCCH Dedicated Control Channel Knh >i=u khiPn ringDCS

Data CommunicationSubsystem Phn h+thng tin sOli+u

EIR Equipment Identity Register Thanh ghi nhJn d(ng thiWt bAETSI European Telecommunication

Standards InstitudeVi+n tiu chuun viln thngchu u

FACCH Fast Associated Control Knh >i=u khiPn lin kWt


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Channel nhanh

FB Frequency Correction Burst CRm hi+u chEnh t^n sOFCCH Frequency Correction Channel Knh hi+u chEnh t^n sOFDMA Frequency Division Multiple

Access8a truy nhJp phn chia theot^n sO

GMSC Gateway MSC MSC cSngGPRS General Packet Radio Service DAch vRv tuyWn gi chungGSM Global System for

Mobile CommunicationThng tin di >?ng ton c^u

HLR Home Location Register Thanh ghi >Anh vAthTng trIMEI International Mobile Equipment

IdentityNhJn d(ng thiWt bAdi >?ngquOc tW

IMSI International Mobile SubscriberIdentity

NhJn d(ng thu bao di >?ngquOc tW

ISDNIntegrated Service Digital

Network M(ng sO>a dAch vR

ISI Intersymbol InterferenceNhilu giao thoa gija cc khi+u

IWF Inter Working Function ChXc nUng t"ng tcLA Location Area Vng >Anh vALAC Location Area Code M vng >Anh vALAI Location Area Identity NhJn d(ng vng >Anh vAME Mobile Equipment ThiWt bAdi >?ng

MMS Multimedia Messaging Service DAch vRnhZn tin >a ph"ng ti+nMS Mobile Station Tr(m di >?ngMSC Mobile services Switching

CenterTrung tm chuyPn m(ch ccdAch vRdi >?ng

MSISDN Mobile Station ISDN Number SOISDN tr(m di >?ng

MSRNMobile Station Roaming

Number SOlu >?ng tr(m di >?ng

NB Normal Burst CRm bnh thTngNMT Nordic Mobile Telephone 8i+n tho(i di >?ng BZc uOMC Operation and Maintenance

CenterTrung tm bpo drng vvJn hnh

OSS Operation and Support System H+thOng khai thc v hstr PCH Paging Channel Knh tm gaiPCM Pulse Code Modulation 8i=u chWxung mPIN Personal Identification Number SOnhJn d(ng c nhn


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PLMN Public Land Mobile Network M(ng di >?ng mht >Mtcng c?ng

PSPDN Packet Switch Public DataNetwork

M(ng sOli+u cng c?ngchuyPn m(ch gi

PSTN Public Switched TelephoneNetwork

M(ng >i+n tho(i chuyPn m(chcng c?ng

RACH Random Access Channel Knh truy nhJp ng$u nhin

RAND Random number SOng$u nhin

SACCHSlow Associated ControlChannel Knh >i=u khiPn lin kWt chJm

SB Synchronization Burst CRm >wng b?SCH Synchronization Channel Knh >wng b?SDCCH Stand alone Dedicated Control

Channel

Knh >i=u khiPn ring >Xng

m?t mnhSIM Subscriber Identity Module M>un nhJn d(ng thu baoSMS Short Message Service DAch vRnhZn tin ngZnSRES Signed Response MJt khuuSS Switching System H+thOng chuyPn m(chTACS Total Access Communication

SystemH+thOng thng tin truy nhJpton b?

TCH Traffic Channel Knh lu l`ngTDMA Time Division Multiple Access 8a truy nhJp phn chia theo

thTi gianTMN Telecommunication

Management NetworkM(ng qupn l viln thng

TRAU Transcoder/Rate AdaptationUnit

KhOi chuyPn >Si m v thchXng tOc >?

VLR Visitor Location Register Thanh ghi >Anh vAt(m trWAP Wireless Application Protocol Giao thXc Xng dRng khng dy


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