TỔNG QUAN GSM.docx

8/14/2019 TNG QUAN GSM.docx

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TNG QUAN GSM1. Cu Trc C Bn Mng GSM

Sau nhu chn la th y l hnh mnh ng nht vcu trc mng GSM, rt trc quan v thc t,chc nng tng quan ca cc thnh phn nh sau:

1.1. in thoi (Mobile Station-MS) c cha SIM : l thit bm ngi dng tng tc mt cctrc tip nhiu nht

- SIM :Gip nh mng phn bit cc thu bao vi nhau, Mobile Station = Sim + Mobile Equipment.Sim c xem nh l 1 database, n ko chcha thng tin lin quan n thu bao m cn nhu thng tkhc na.


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Administrative data (phn ny dhiu roi nha ace)PIN/PIN2 (m/v) Personal identification number; requested at every powerup (PIN or PIN2)

PUK/PUK2 (m/f) PIN unblocking key; required to unlock a SIM

SIM service table (m/f) List of the optional functionality of the SIM

Last dialed number) (o/v) Redial

Charging meter (o/v) Charges and time increments can be set

Language (m/v) Determines the language for prompts by the mobile station

Secur ity related data

Algorithm A3 and A8 Required for authentication and to determine Kc

Key Ki (m/f) Individual value; known only on SIM and the HLR

Key Kc (m/v) Result of A8, Ki, and random number (RAND)

CKSN (m/v) Ciphering key sequence number

Phn ny lin quan n bo mt. Trn thc tkhi mt MS mun attach vo mng lc ban u cng nhkhi mn thc hin cuc gi th phi tri qua cc phase kim tra: Authentication, Ciphering v check

IMEI.

Check IMEI th c thhiu l kim tra tnh hp php ca thit b(MS ca mnh) nhng chc nng nyVN cc operator ko sdung.

Authentication th kim tra tnh hp php ca user trn c sdliu ca n.Ciphering l bc m ha dliu khi truyn v tt nhin cn phi thng nht loi thut ton gia MSv mng.Cc parameter ny nhm phc vcho cc phase ny. Sau ny khi i vo tng phase kt ni th mnh s

gii thch khn nu c c hi

Subscri ber data

IMSI (m/f) International mobile subscriber identity

MSISDN (o/f) Mobile subscriber ISDN; directory number of a subscriber

Access control class(es) For control of network access

MSISDN: l ci sin thoi ca mnh , c dng rng ri cho cc mng khc mn tm kim giIMSI th nh danh ca thu bao chring trong mng ca mnh, cc i tn nhu ln cng bo mt

Access control class: ci ni potay hehe

Roaming data

TMSI (m/v) Temporary mobile subscriber identity

Value of T3212 (m/v) For location updating

Location updating status Is a location update required?LAI (m/v) Location area information

Network color codes(NCCs) of restricted PLMNs (m/v)

TMSI th 1 nh danh ring trong mng nhng n khc IMSI chn c thay i lin tc v cp pht

lin tc mi khi c pht sinh dch vtthu bao nh cp nht vtr, gi. V thng trao i thTMSI c dng thng xuyn trn mng, hn chdng IMSI tng thm bo mt.

Cc gi trvcp nht vtr: th nh chng ta bt, mng GSM l mng tbo, c chia thnh nhu cellv nh mng qun l theo tng khu vc. Gi trtimer cp nht nh thi vtr, m vtr, m mng.

PLMN data


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NCC, mobile country code (MCC), and mobile network code (MNC) of the home PLMN (m/f)

Absolute radio frequency channel numbers (ARFCNs)

Ci ny th cc parameter lin quan ti mng di ng m mnh ang dng, ngoi ra cn c tp tn sca mng ny sdng naT ra sim cng lm thlinh tinh phi ko ace, sau ny khi i vo tng phase cthth sthy r hn.

-in thoi :ci ny mnh ko quan tm lm nn ace thng cm

2. BSS ( Basic Station Subsystem )

u tin trc khi i vo phn BTS th mnh sgii thiu s qua vcc thnh phn cbn trong mng.

- BTS :dhiu l cc "anten" bbnm trn sn thng cc ta nh m ta ddng thy c khi iln. Nhim vchnh ca n l lin quan n giao din v tuyn, cung cp kt ni gia MS v nh

mng.

- BSC :BTS c kt ni ti BSC qua giao din Abis, c xem nh 1 tng i chuyn mch trong khu v

nh. Qun l ti nguyn, iu khin BTS trong vng n qun l.- MSC :Theo cch qun l phn cp nn cc tng i con BSC sc qun l bi tng i cp cao hnl MSC qua giao din A, nhim vchuyn mch, qun l ti nguyn, tnh cc, ...

- HLR/AUC :l c sdliu lu ton bthng tin ca thu bao, AUC l module xc thc thu baotrn HLR

- VLR :trn thc tl 1 module trn MSC, l 1 c sdliu tm thi, chlu trcc thng tin cathu bao trong khu vc ca MSC qun l. Khi 1 MS di chuyn qua vng MSC khc th dliu cn

c thay i qua VLR khc --> ngi ta thng vit l MSC/VLR l nh vy

- EIR :l thnh phn ko bt buc, dng check IMEI ca in thoi. Nh mng VN ko sdng tnh

nng ny.- PCU :l 1 card trn BSC, n thc hin chc nng xl, chuyn mch gi cho mng GPRS, giao tip

vi SGSN- SGSN :c thxem tng tnh MSC nhng n dng cho mng chuyn mch gi GPRS

- GSGSN :l gateway ca mng GPRS, cng giao tip vi mng gi khc nh internet

- GMSC :ko c trn hnh nhng mnh mn nhc qua l c chc nng gateway ca mng GSM i ramng ngoi nh mng PLMN ca nh mng khc hoc mng in thoi cnh. C thxem GMSC vGSGSN c chc nng chung tng tnhau.

2.1. BTS ( Base Transceiver Station )

S khi chung ca nhu loi BTS khc nhau:


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y mnh scng mxcon BTS Ultrasite ca Nokia lm r hn

BTS l thit btruyn tn hiu qua 2 giao din:- V tuyn: ti MS

- Abis: ti BSC qua ng dy E1 = 2M hoc T1 = 1.5M


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- Mi uplink/downlink nh vy chi lm 124 knh tn s, cc knh ny cch nhau 200Khz.

- Vy th ngi ta sdng cc tn sny nh thno kt ni ti hng ngn thu bao ?????GSM sdng phng php truy nhp TDMA/FDMA

- Cc thu bao struyn trn cc tn skhc nhau, v trong mi tn sny sc phn chia theo thigian nhm tng sthu bao c thln. Mi carrier = 8 Timeslot nh hnh v. Nh vy ni n knh

thoi cho 1 thu bao = f? + TS?.- Trn thc tth cc nh mng phi chia snhau di tn ny, c ngha l mi operator nh viettel, vinhay mobi squn l 1 slng tn shn chno chko dng mt mnh ht ton b.Vi slng tn shn chnh vy, gis1 mng shu 10 tn s, m 1 tn sc bn htr8 thu

bao --> max user = 10 x 8 = 80 thu bao


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GSM hay tt ccc mng di ng ni chung c phn chia theo t bo (cell) v sdng bin php ti sdng tn snh sau.

-Ngi ta chia mi khu vc a l l 1 cell v c thxem nh 1 cell ny sgn 1 thng BTS, thngBTS ny schnhn nhim vvgiao din v tuyn trong cell ny m thi. V vy i ngoi ng s

thy slng BTS xut hin rt nhiu trn cc ngi nh.- Ty theo khu vc ng dn c hay ko m ngi ta plan l cell ny rng hay nhnh hnh trn. Tathy khu vc thnh thvi mt thu bao ln th cell nh, cn nng thn th cell ln. Nu tng

tng 1 nh mng vi phm vi ct nc VN ch1 cell (ngha l ko chia cell) th nh v dpha tranta thy chphc vc 80 thu bao. Nhng nu cng chia nhcng nhu cell v mi cell ny sdngton b10 tn s(ti sdng tn s) th ta c ththy c slng thu bao stng ln ng k. 80thu bao by gic thhiu l trong 1 cell phm vi rt nh. Bn cnh cn vn cng sut ri cht

lng tn hiu th mng di ng 1 cell l hon ton ko khthi.- Khi sdng bin php chia cell v ti sdng tn sth trnh nhiu ngi ta phi chia 1 nhm cethnh cc cluster sao cho cc cell ln cn ko trng tn sca nhau.


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V dvli ch ti sdng tn s:Nh mng c cp 7.2 Mhz = 35 carrier x 200 Khz + 1 carrier bo vbn ngoi ---> c c 35 tn s1 tn s= 8 TS = 8 thu bao

Nu mng chphn chia theo 1 cell -> Max user = 35 x 8 = 280 thu baoNu mng phn chia 70 cell vi hs cluster l 7 --> (70/7) x 35 x 8 = 10 x 280 = 2800 thu bao ( gp10 ln)

Nu 700 cell --> 28000 thu bao

Tm li:- u im:

+ Tng sthu bao phc v+ Vn cng sut

-Nhc:+ Trin khai mng li tn km+ Nhiu cell ln cn

+ Cng nhu cell th handover cng xy ra nhu -> tng xc sut rt cuc gi (HANDOVER nn c 1thread ring qu)

Nh ni trn l 1 cell sl 1 BTS, v thc tta c thquan st c khi i rng rng l 1 BTS nschia lm 3 sector nh.


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Cu hnh cho 1 BTS hot ng trn thc tsc tn dng nh sau: 2+2+2, 4+4+4 hoc ommi2, ommi...

2+2+2 ngha l 3 sector v 1 sector sc 2 TRX cards ( 1 TRX = 1 freq = 8 ts = 8 thu bao


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- Sau khi cc hardware trn BTS sn sng (y cc card v c cu hnh, ngi ta thng dngthut ngl commisionning) th sc ni ti BSC qua dy E1/T1. Chng ta sdng 1 phn mm ktni ti BSC v khai bo stn ti BTS ny trn BSC.

- Lu y, mnh cha ra nhng cu hnh c bn v chthuc vthit bNokia m mnh bt. Trnthc tc nhu loi cu hnh v c thc skhc nhau gia nokia, huwai, sony erricson...- Trli vic cu hnh BTS trn BSC, ng trn BSC chng ta sdng cc lnh khai bo cho BTS ny1 ID, Name v cc thng skhc. Lc ny BTS sc gi l BCF (mnh cng chhu v sao m ti

Nokia n i cch gi nh vy na) cn cc sector th ti n gi l cell (!). Nh vy y ta sthyxut hin 2 khi nim vCell. Cell vt l = ci BTS thc sca mnh. Cell logic = 1 sector trong 1

BCF.

- Trong 1 sector ngi ta thng dng timeslot u tin TS0 ca TRX u tin dng truyn cc bohiu gia MS v BTS. Th bo hiu l g?- to 1 cuc gi tMS1 ti MS2 th ban u cc MS v netwokr phi thit lp kt ni bng cch gcc thng tin qua li vi nhau, nhng thng tin ny c gi l bo hiu. Cn sau khi thit lp c kt nitc l in thoi bn kia chung v ta bt u bm phm nghe th lc ny bo hiu stm thi kt

thc nhng cho dliu thoi. Th ta c thhiu l nhng thng tin khng phi l tn hiu thoi vgip nh mng vi MS thit lp kt ni cng nh trao i thng tin iu khin gi l bo hiu.

- Timeslot c thmang 2 loi thng tin:+ Signal (bo hiu) --> thng nm Timeslot 0 ca TRX u tin+ Thoi -> Timeslot cn li.Mi cuc gi struyn dliu thoi trn 1 TS c sging nhau trn cuplink v downlink.


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Nh hnh trn, ta thy khung uplink v khung downlink truyn khng ng thi v thi gian cch nhauny bng thi gian truyn 3 timeslot. L do trnh vic MS va nhn thng tin v truyn thng tin imt cch ng thi. Thi gian nghny MS dng tnh ton, xl, o cht lng sng trong cell

cng nh cell ln cn.- Mt timeslot trong 1 tn sngi ta gi l 1 knh vt l, v da vo chc nng ca timeslot ny ltruyn bo hiu hay dliu thoi th ngi ta gi bng cc tn khc nhau gi l knh logic. V dnhta xy 1 con ng mi trong thnh phth con ng hin hu ny gi l knh vt l, trong nm u

tin ta sdng ng ny chdnh ring cho xe gn my th con ng lc ny gi l ng dnhring cho xe gn my, nm tip theo ta mn ng ny chcho ngi i bth vn l con ng nha

nhng lc ny li gi l ng dnh ring cho ngi i b. Nh vy tn gi con ng ty theochc nng v mc chth gi l knh logic.

Cc knh logic trong GSM nh sau


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- Traffic channel (TCH)knh truyn dliu thoi, chia ra 2 loi theo tc l fullrate v halfrate. Thalfrate c sdng tng slng thu bao ln v tt nhin cht lng thoi sgim xung.Lc ny 1TS sc dnh cho 2 thu bao. Ch cc timeslot ny phn chia theo thi gian v truyn the

khung = 8 TS nn 2 user phi ln lt sdng so le cc khung nn tc bit sgim cn 1 na -> chlng thp.

- Signal channel:bo hiu iu khin gia MS v mng. Cc bn lu l cc khi nim ny chng taang ni trngiao din v tuyn hey. Khng vi ba nhy qua giao din dy Abis th li nhm lung

tung cln.Nh trn c ni th tt ccc knh bo hiu ny thng c cu hnh trn duy nht 1 knh vt l l

TS0 ca TRX u tin trong sector v tt nhin chng cng phi c truyn ln lt tng tnh thngknh thoi (TCH) truyn halfrate. my TS cn li nhng cho knh thoi (TCH).

+ Nhm knh BROADCAST--> thng tin qung b tnh mngFCCH: Chdng downlink. Truyn thng tin gip MS ng btn s

SCH: downlink. Gip MS ng bkhung, thng tin vtrm BTSBCCH: downlink. Cung cp cc thng tin chung vmng, v cell m MS ang ng

+ Nhm knh COMMON CONTROL--> dng chung cho tt ccc thu baoPCH: downlink. Tm gi MS2

RACH: uplink. MS gi thng tin yu cu dch vln cho mng (yu cu thit lp cuc gi chng hn)AGCH: downlink. Trli cho knh RACH, cp cho MS thng tin knh SDCCH hoc TCH m n cquyn sdng

+ Nhm knh DEDICATED CONTROL--> c sdng ring cho mi thu baoSDCCH: uplink & downlink. Thit lp kt ni gia MS v mng: IMSI attach, check IMEI,

authentication, ciphering, location update ...

SACCH: uplink & downlink. Dng truyn bo hiu khi ang trong cuc gi v lc ny SDCCH c gii phng nn SACCH c dng nh 1 knh kt hp vi TCH. Thng tin trn knh ny thng l tinhn, o cng sut.FACCH: uplink & downlink. Ging nh knhSACCH nhng thng tin FACCH thng mang tnh chcp bch nh handover chng hn. Handover mnh xin ni qua l qu trnh chuyn tcell phc vny

sang cell phc vkhc m ko lm drop cuc gi. Khi cn handover th phi truyn bo hiu nn TCHlc ny trthnh FACCH ngay tc th p ng nhu cu v sau trli lm TCH. Cn SACCHth ko cn gp nn n i tTCH theo chu k.

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TỔNG QUAN GSM.docx