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TRNGNG II HC BCH KHOA H NI
KHOA IN T VIN
BO CO THC TP
ti: Mng thng tin di ng GSM
Gio vin hng dn: TS. Phm Cng Hng
Sinh vin thc hin : Lp :
H NI, 1- 2005
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MC LC MC LC
...................................................................................................
1 LI NI U
.............................................................................................
3 CHNG 1. CU HNH MNG GSM
...................................................... 4
1.1 Gii thiu chung v mng thng tin di ng GSM
............................. 4 1.1.1. Vi nt lch s v mng GSM
..................................................... 4 1.1.2. Cc
ch tiu k thut ca mng GSM .........................................
5
1.2. Cu trc h thng GSM
.........................................................................
6 1.2.1. H thng con chuyn mch SS
....................................................... 6
1.2.1.1. Trung tm chuyn mch cc dch v di ng cng MSC ......... 7
1.2.1.2. B ghi nh v thng tr HLR
............................................... 8 1.2.1.3. B ghi nh
v tm tr VLR ..................................................... 8
1.2.1.4. Trung tm nhn thc AUC
...................................................... 8 1.2.1.5. B
ng k nhn dng thit b EIR ..........................................
8
1.2.2. Phn h trm gc BSS
....................................................................
9 1.2.2.1. Trm thu pht gc
BTS........................................................ 9
1.2.2.2. B iu khin trm gc BSC
............................................... 9 1.2.2.3. B chuyn
i m v thch ng tc TRAU ....................10
1.2.3. Trm di ng MS
..........................................................................10
1.2.4. Phn h khai thc OSS
..................................................................11
2.1. V tuyn s tng
qut.......................................................................12
2.1.1. Suy hao ng truyn v pha inh
............................................12 2.1.2. Phn tn thi
gian
......................................................................14
2.1.3. Cc phng php phng nga suy hao truyn dn do phainh ..15 2.1.4.
Phng php chng phn tn thi gian
......................................17
2.1.5. Truyn dn s v tn hiu tng t
........................................18 2.2. Nguyn tc khi chia
knh theo khe thi gian ....................................20
2.2.1. Khi nim knh
.........................................................................20
2.2.1.1. Knh vt l
.........................................................................20
2.2.1.2 Knh logic
...........................................................................21
2.2.2. Cm
..........................................................................................22
2.2.3. Chia knh logic theo khe thi gian
............................................23
CHNG 3. NGUYN TC S DNG TN S
...................................25 3.1. Nguyn tc s dng tn s theo
chia ..............................................25
3.1.1. S dng tn s
...........................................................................25
3.1.2. S ti s dng tn s trn mng
.................................................26
3.1.2.1. C s l thuyt
....................................................................26
3.1.2.2. Mu s dng li tn s
........................................................26
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3.2. Cc trng hp v th tc thng tin
.................................................29 3.2.1. Tng quan
.................................................................................29
3.2.3. Th tc nhp mng ng k ln u
..........................................30 3.2.4. Th tc ri mng
.......................................................................31
3.2.5. Tm gi
......................................................................................31
3.2.6. Gi t MS
.................................................................................31
3.2.7. Gi n thu bao MS
.................................................................31
3.2.8. Cuc gi ang tin hnh, nh v
...............................................32
CHNG 4. CC DCH V CA GSM
..................................................34 4.1. Dch v
thoi
....................................................................................34
4.2. Dch v s liu
.................................................................................34
4.3. Dch v nhn tin ngn
SMS..............................................................34
4.4. Dch v Wap
....................................................................................34
4.5. Cc dch v mi ca GSM 2,5G
.......................................................35
KT LUN
................................................................................................36
PH LC: CC T VIT TT
................................................................37
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LI NI U
Hin nay trong cuc sng hng ngy thng tin lin lc ng mt vai tr rt
quan trng khng th thiu c, n quyt nh nhiu mt hot ng ca x hi, gip con
ngi nm bt nhanh chng cc gi tr vn ho, kinh t, khoa hc k thut rt a
dng v phong ph.
Bng nhng bc pht trin thn k, cc thnh tu cng ngh in T Tin Hc Vin
Thng lm thay i cuc sng con ngi tng gi tng pht , n to ra mt tro lu
"in T Tin Hc Vin Thng " trong mi lnh vc th k 21.
Lnh vc Thng Tin Di ng cng khng nm ngoi tro lu . Cng vi nhiu cng
ngh khc nhau Thng Tin Di ng ang khng ngng pht trin p ng nhu cu thng
tin ngy cng tng c v s lng v cht lng, to nhiu thun li trong min thi
gian cng nh khng gian. Chc chn trong tng lai Thng Tin Di ng s c hon
thin nhiu hn na tho mn nhu cu thng tin t nhin ca con ngi.
Trn c s nhng kin thc tch lu c qua 5 nm hc tp chuyn ngnh in T Vin
Thng ti trng i hc Bch Khoa H Ni v hn mt thng thc tp ti phng k thut
cng ty thng tin di ng VMS, ti hon thnh bn bo co thc tp tt nghip
ny.
hon thnh bn bo co ny ti xin chn thnh cm n thy gio TS Phm Cng Hng
tn tnh hng dn ti trong sut qu trnh thc tp tt nghip.
Ti cng xin chn thnh cm n s gip nhit tnh ca trng phng V Anh cng
cc cn b phng k thut trong sut qu trnh thc tp .
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CHNG 1. CU HNH MNG GSM
1.1 Gii thiu chung v mng thng tin di ng GSM
1.1.1. Vi nt lch s v mng GSM H thng thng tin di ng t lu l mt c m
ln ca con ngi, v c m ny tr thnh hin thc ngay khi k thut cho php. S
thc hin u tin bng sng v tuyn c thc hin t cui th k 19. Tuy nhin vic
a h thng thng tin di ng vo phc v ch c thc hin sau chin tranh th gii
ln th 2, khi m cng ngh in t cho php. l mt dch v thng tin c bit, n
cho php ni thng cc cuc gi khng cn dy dn. Ngay ngay c khi di chuyn,
cc thu bao di ng vn trao i thng tin c vi nhau. Do s pht trin ngy
cng cao ca cng ngh in t v thng tin, mng thng tin ngy cng ph bin, gi
c ngy mt h v tin cy ngy cng tng ln. Qu trnh pht trin ca mng thng
tin tri qua cc giai on sau: - Giai on th nht: Sau 1946, kh nng phc
v nh, cht lng khng cao, gi c dt. - Giai on th hai: T 1970 1979, cng
vi s pht trin ca cc thit b in t t hp c ln v cc b vi x l, ta c th
thc hin c mt h thng phc tp hn. Bi v vng ph sng ca anten pht ca cc
my di ng b hn ch nn h thng c chia thnh mt vi trm nhn cho mt trm
pht. - Giai on th ba: T1979 -1990, l mng t ong tng t. Cc trm thu
pht c t theo cc t ong. Mng ny cho php s dng li tn s v cho php chuyn
giao gia cc trong cuc gi. Cc mng in hnh l: + AMPS (Advanced Mobile
Phone Service): c a vo hot ng ti M nm 1979. +NMT ( Nordic Mobile
Telephone): l h thng ca cc nc Bc u v c a vo s dng vo thng 12/1981.
+TACS ( Total Access Communication System): c a vo phc v ti Vng quc
Anh nm 1985. Tt c cc mng trn da trn mng truyn in thoi tng t bng iu
ch tn s. Chng s dng tn s 450 hoc 900 Mhz. Vng ph sng ca n ch mc quc
gia v phc v c vi trm thu bao. H thng ln nht Anh l TACS t hn mt triu
thu bao vo nm 1990. - Giai on th t: T u nhng nm 1980, sau khi cc h
thng NMT hot ng thnh cng th n cng biu hin mt s hn ch. Mt l do yu cu
cho dch v di ng qu ln vt qua con s mong i ca cc nh thit k h thng nn
h thng ny khng p ng c. Hai l cc h thng khc nhau ang hot ng khng th
phc v cho tt c cc thu bao chu u, ngha l thit b ca mng ny khng th
truy nhp vo mng khc. Ba l nu thit k mt mng ln phc v cho c chu u th
khng mt nc no c th p ng c v vn u t qu ln. Tt c nhng hn ch trn dn n
mt nhu cu l phi thit k mt h thng loi mi c lm theo kiu chung c th
dng cho nhiu nc. Nm
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1988, vin tiu chun vin thng chu u ETSI (Europe Telecommunication
Standard Institute) thnh lp nhm c trch di ng GSM (Groupe Special
Mobile). GSM cn c ngha l h thng thng tin di ng ton cu (Global
System for Mobile Communication). GSM l tiu chun in thoi di ng s
ton chu u s dng di tn s 900Mhz. Nm 1990, Vng quc Anh a ra h thng
DCS (Digital Cellular System). DCS da trn h thng GSM vi vic s dng
tn s 1800Mhz. Hin nay, p ng nhu cu ngy cng tng v cc dch v vin thng
mi, cc h thng thng tin di ng ang tin ti th h th ba. th h th ba ny,
cc h thng thng tin di ng c xu th ho nhp thnh mt tiu chun duy nht v
c kh nng phc v tc ln n 2Mbit/s. Vit Nam, h thng thng tin di ng s
GSM c a vo t nm 1993, hin nay ang c hai cng ty VMS v GPC khai thc
rt hiu qu. Trong nm 2004 ny cng ty Vietel cng s cung cp dch v
ny.
1.1.2. Cc ch tiu k thut ca mng GSM H thng thng tin di ng GSM cho
php chuyn vng t do ca cc thu bao trong chu u, c ngha l mt thu bao c
th thm nhp sang mng ca nc khc khi di chuyn qua bin gii. Trm di ng
GSM MS (GSM Mobile Station) phi c kh nng trao i thng tin ti bt c ni
no trong vng ph sng quc t.
V kh nng phc v : - H thng c thit k sao cho MS c th dng c trong
tt c cc nc
c mng. - Cng vi phc v thoi, h thng phi cho php s linh hot ln nht
cho
cc loi dch v khc lin quan ti mng s lin kt a dch v (ISDN). - To
mt h thng c th phc v cho cc MS trn cc tu vin dng nh
mt mng m rng cho cc dch v di ng mt t. V cht lng phc v v an ton
bo mt: - Cht lng ca thoi trong GSM phi t nht c cht lng nh cc h
thng di ng tng t trc trong iu kin vn hnh thc t. - H thng c kh
nng mt m ho thng tin ngi dng m khng nh
hng g n h thng cng nh khng nh hng n cc thu bao khc khng dng n kh
nng ny.
V s dng tn s: - H thng cho php mc cao v hiu qu ca di tn m c th
phc
v vng thnh th v nng thn cng nh cc dch v mi pht trin. - Di tn s
hot ng l 890-915 v 935-960 Mhz. - H thng GSM 900Mhz phi c th cng tn
ti vi cc h thng dng
900Mhz trc y. V mng: - K hoch nhn dng da trn khuyn ngh ca
CCITT.
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- K hoch nh s da trn khuyn ngh ca CCITT. - H thng phi cho php cu
trc v t l tnh cc khc nhau khi c
dng trong cc mng khc nhau. - Trung tm chuyn mch v cc thanh ghi
nh v phi dng h thng bo
hiu c tiu chun ho quc t. - Chc nng bo v thng tin bo hiu v thng
tin iu khin mng phi
c cung cp trong h thng.
1.2. Cu trc h thng GSM Mt h thng GSM c th c chia thnh nhiu phn h
sau y:
- Phn h chuyn mch (SS: Switching Subsystem) - Phn h trm gc (BSS:
Base Station Subsystem) - Phn h khai thc (OSS: Operation Subsystem)
- Trm di ng (MS: Mobile Station)
1.2.1. H thng con chuyn mch SS H thng con chuyn mch bao gm cc
chc nng chuyn mch chnh ca GSM cng nh cc c s d liu cn thit cho s liu
thu bao v qun l di ng
BSS
MS
AUC
HLR
MSC
VLR EIR
SS
BSC
BTS
OSS
ISDN
PSPDN
CSPDN
PSTN
PLMN
Hnh 1. M hnh h thng GSM
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ca thu bao. Chc nng chnh ca SS l qun l thng tin gia nhng ngi s
dng mng GSM vi nhau v vi mng khc. H thng con chuyn mch SS bao gm cc
khi chc nng sau:
- Trung tm chuyn mch cc dch v di ng (MSC: Mobile Services
Switching Center).
- B ghi nh v tm tr (VLR: Visitor Location Register) - B ghi nh v
thng tr (HLR: Home Location Register)
- Trung tm nhn thc (AUC: Authentication Center) - B nhn dng thit
b (EIR: Equipment Identity Register) - Trung tm chuyn mch cc dch v
di ng cng (GMSC: Gateway Mobile Services Switching Center)
1.2.1.1. Trung tm chuyn mch cc dch v di ng cng MSC SS, chc nng
chuyn mch chnh c MSC thc hin. Nhim v chnh ca MSC l iu phi vic thit
lp cuc gi n nhng ngi s dng mng GSM. Mt mt MSC giao tip vi phn h
BSS, mt khc n giao tip vi mng ngoi. MSC lm nhim v giao tip vi mng
ngoi c gi l MSC cng. Vic giao tip vi mng ngoi m bo thng tin cho ngi
s dng mng GSM i hi cng thch ng (cc chc nng tng tc IWF: Interworking
Function). SS cng cn giao tip vi mng ngoi s dng cc kh nng truyn ti
ca cc mng ny cho vic truyn ti s liu ca ngi s dng hoc bo hiu gia cc
phn t ca mng GSM. MSC thng l mt tng i ln iu khin v qun l mt s cc b
iu khin trm gc . kt ni MSC vi mt s mng khc, cn phi thch ng cc c im
truyn dn ca GSM vi cc mng ny. Cc thch ng ny c gi l cc chc nng tng
tc IWF (Interworking Function) bao gm mt thit b thch ng giao thc v
truyn dn. N cho php kt ni vi cc mng: PSPDN (Packet Switched Public
Data Network: mng s liu cng cng chuyn mch gi), hay CSPDN (Circuit
Switched Public Data Network: mng s liu cng cng chuyn mch knh), n
cng tn ti khi cc mng khc ch n thun l PSTN hay ISDN. IWF c th c thc
hin trong cng chc nng MSC hay c th thit b ring, trng hp hai th giao
tip gia MSC v IWF c m. thit lp mt cuc gi n ngi s dng GSM, trc ht
cuc gi phi c nh tuyn n mt tng i cng GMSC m khng cn bit n hin thi
thu bao ang u. Cc tng i cng c nhim v ly thng tin v v tr ca thu bao
v nh tuyn cuc gi n tng i ang qun l thu bao thi im hin thi (MSC tm
tr). vy trc ht cc tng i cng phi da trn s thoi danh b ca thu bao tm
ng HLR cn thit v hi HLR ny. Tng i cng c mt giao din vi cc mng bn
ngoi vi mng GSM. V phng din kinh t, khng phi bao gi tng i cng cng
ng ring m thng c kt hp vi MSC.
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1.2.1.2. B ghi nh v thng tr HLR L c s d liu quan trng nht ca mng
GSM, lu tr cc s liu v a ch nhn dng cng nh cc thng s nhn thc ca thu
bao trong mng. Cc thng tin lu tr trong HLR gm: nhn dng thu bao
IMSI, MSISDN, VLR hin thi, trng thi thu bao, kho nhn thc v chc nng
nhn thc, s lu ng trm di ng MSRN. HLR cha nhng c s d liu bc cao ca
tt c cc thu bao trong GSM. Nhng d liu ny c truy nhp t xa bi cc MSC
v VLR ca mng.
1.2.1.3. B ghi nh v tm tr VLR VLR l c s d liu th hai trong mng
GSM. N c ni vi mt hay nhiu MSC v c nhim v lu gi tm thi s liu thu
bao ca cc thu bao hin ang nm trong vng phc v ca MSC tng ng v ng thi
lu gi s liu v v tr ca cc thu bao ni trn mc chnh xc hn HLR. Cc chc
nng VLR thng c lin kt vi cc chc nng MSC.
1.2.1.4. Trung tm nhn thc AUC AUC qun l cc thng tin nhn thc v mt
m lin quan n tng c nhn thu bao da trn mt kho nhn dng b mt Ki m bo
ton s liu cho cc thu bao c php. Kho ny cng c lu gi vnh cu v b mt
trong b nh MS. B nh ny c dang Simcard c th rt ra v cm li c. AUC c
th c t trong HLR hoc MSC hoc c lp vi c hai. Khi dng k thu bao, kho
nhn thc Ki c ghi nh vo Simcard ca thu bao cng vi IMSI ca n. ng thi
kho nhn thc Ki cng c lu gi trung tm nhn thc AUC to ra b ba thng s
cn thit cho qu trnh nhn thc v mt m ho:
- S ngu nhin RAND - Mt khu SRES c to ra t Ki v s ngu nhin RAND
bng thut ton
A3 - Kho mt m Kc c to ra t Ki v s ngu nhin RAND bng thut
ton A8
1.2.1.5. B ng k nhn dng thit b EIR Qun l thit b di ng c thc hin
bi b ng k nhn dng thit b EIR. EIR lu gi tt c cc d liu lin quan n
phn thit b di ng ME ca trm di ng MS. EIR c ni vi MSC thng qua ng bo
hiu kim tra s c php ca thit b bng cch so snh tham s nhn dng thit b
di ng quc t IMEI (International Mobile Equipment Identity) ca thu
bao gi ti khi thit lp thng tin vi s IMEI lu gi trong EIR phng trng
hp y l nhng thit b u cui b nh cp, nu so snh khng ng th thit b khng
th truy nhp vo mng c.
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1.2.2. Phn h trm gc BSS BSS thc hin nhim v gim st cc ng ghp ni v
tuyn, lin kt knh v tuyn vi my pht v qun l cu hnh ca cc knh ny. l: -
iu khin s thay i tn s v tuyn ca ng ghp ni (Frequency Hopping) v s
thay i cng sut pht v tuyn. - Thc hin m ho knh v tn hiu thoi s, phi
hp tc truyn thng tin. - Qun l qu trnh Handover. - Thc hin bo mt knh
v tuyn. Phn h BSS gm hai khi chc nng: b iu khin trm gc (BSC: Base
Station Controller) v cc trm thu pht gc (BTS: Base Transceiver
Station). Nu khong cch gia BSC v BTS nh hn 10m th cc knh thng tin c
th c kt ni trc tip (ch Combine), ngc li th phi qua mt giao din
A-bis (ch Remote). Mt BSC c th qun l nhiu BTS theo cu hnh hn hp ca
2 loi trn.
1.2.2.1. Trm thu pht gc BTS Mt BTS bao gm cc thit b pht thu,
anten v x l tn hiu c th cho giao din v tuyn. C th coi BTS l cc
Modem v tuyn phc tp c thm mt s cc chc nng khc. Mt b phn quan trng
ca BTS l TRAU (Transcoder and Rate Adapter Unit: khi chuyn i m v
thch ng tc ). TRAU l thit b m qu trnh m ho v gii m ting c th ring
cho GSM c tin hnh, y cng thc hin thch ng tc trong trng hp truyn s
liu. TRAU l mt b phn ca BTS, nhng cng c th t cch xa BTS v thm ch
trong nhiu trng hp c t gia BSC v MSC. BTS c cc chc nng sau:
- Qun l lp vt l truyn dn v tuyn - Qun l giao thc cho lin kt s
liu gia MS v BSC
- Vn hnh v bo dng trm BTS - Cung cp cc thit b truyn dn v ghp knh
ni trn giao tip A-bis
1.2.2.2. B iu khin trm gc BSC BSC c nhim v qun l tt c giao din v
tuyn qua cc lnh iu khin t xa BTS v MS. Cc lnh ny ch yu l cc lnh n
nh, gii phng knh v tuyn v qun l chuyn giao (Handover). Mt pha BSC c
ni vi BTS cn pha kia ni vi MSC ca SS. Trong thc t, BSC l mt tng i
nh c kh nng tnh ton ng k. Mt BSC c th qun l vi chc BTS tu theo lu
lng cc BTS ny. Giao din gia BSC v MSC l giao din A, cn giao din gia
n vi BTS l giao din A-bis.
Nhn vin khai thc c th t trung tm khai thc v bo dng OMC np phn mm
mi v d liu xung BSC, thc hin mt s chc nng khai thc v bo dng, hin th
cu hnh ca BSC.
