MC LC

Phn h a phng tin IMS

MC LC

1MC LC

3LI NI U

7DANH MC CC HNH V

8DANH MC CC BNG BIU

9Chng 1: Tng quan v IMS

91.1 Xu hng pht trin ca dch v v mng vin thng

91.1.1. Xu hng pht trin ca vin thng

101.1.2. Mng vin thng trn con ng tin ti NGN

161.2. Tng quan v IMS

161.2.1. Khi nim IMS

181.2.2. S cn thit ca IMS trong mng NGN

191.3. Lch s pht trin IMS

221.4. u nhc im ca IMS

221.4.1. u im ca IMS

221.4.2. Nhc im ca IMS

1.5. Kt lun chng 1......................................................................................................2425Chng 2: Kin trc phn h v cc giao thc trong IMS

252.1. Gii thiu

252.2. Kin trc v chc nng cc phn t trong IMS.

262.2.1. Lp dch v.

262.2.1.1. My ch ng dng (Appication Server - AS).

272.2.1.2. My ch qun l C s d liu (CSDL) HSS v SLF.

272.2.2. Lp li IMS.

282.2.2.1. Chc nng iu khin phin gi (CSCF - Call Session Control Function).

302.2.2.2. Chc nng iu khin cng vo ra (BGCF).

312.2.2.3. Chc nng iu khin cng truyn thng MGCF.

312.2.2.4. Chc nng ti nguyn truyn thng MRF.

322.2.3. Lp truyn ti.

322.2.3.1. NASS (Network Attachment Subsystem).

322.2.3.2. RACF (Resource & Admission Control Functionality).

332.2.3.3. PSTN/CS Gateway.

342.2.3.4. IMS GW v TrGW.

352.2.3.5. Mng truy nhp.

362.3. Cc im tham chiu IMS.

382.4. Cc giao thc chnh c s dng trong IMS.

382.4.1. Giao thc iu khin phin (SIP).

402.4.2. Giao thc h tr chng thc, cp quyn, tnh cc Diameter(AAA).

422.4.3. Mt vi v d v hot ng ca SIP va DIAMETER trong IMS

442.4.4. Cc giao thc khc.

442.5. Kt lun chng 2

45Chng 3. Cc yu cu v ng dng dch v IMS

453.1. Gii thiu

453.2. Yu cu trong h thng IMS

453.2.1. Thit lp cc phin a phng tin IP

453.2.2. Qun l m bo cht lng dch v - QoS

463.2.3. H tr lin mng

463.2.4. Chuyn vng

473.2.5. iu khin dch v

473.2.6. To dch v nhanh chng v a truy nhp

483.3. Cc loi dch v ng dng ca IMS

483.3.1. Dch v video Conferencing

493.3.2. Dch v Messaging (tin nhn)

493.3.3. Dch v Presence

503.3.4. Dch v Push to talk over cellular

513.3.5. Dch v in thoi di ng v truyn hnh

533.6. Kt lun chng 3

54KT LUN

55TI LIU THAM KHO

LI NI UTrong nhng nm qua xu hng hi t mng Internet, mng di ng v mng PSTN ang l vn c quan tm hng u trong lnh vc thng tin lin lc. Nhiu kin trc mi ra i trong qu trnh pht trin hp nht cc mng vi mc ch to ra mt mng IP duy nht. Phn h IP Multimedia Subsystem (IMS) l mt trong nhng kin trc ra i trong xu th pht trin . IMS tr thnh mt phn h trong m hnh mng th h mi (NGN) ca tt c cc hng sn xut cc thit b vin thng v cc t chc chun ha trn th gii. Vi IMS, ngi dng c th lin lc khp mi ni nh tnh di ng ca mng di ng v ng thi c th s dng nhng dch v hp dn t mng Internet. IMS thc s tr thnh cha kha hp nht mng di ng v mng Internet, l mt phn h khng th thiu trong kin trc NGN.

Trong bi cnh nh vy vic trin khai ti Phn h a phng tin IMS (IP Multimedia Subsystem)" l rt cn thit. Mc tiu ca ti ny l tm hiu tng quan v IMS, kin trc phn h - cc giao thc IMS, cc dch v c th c trin khai trong , phn tch nhng u nhc im v kh nng trin khai IMS trong NGN, qua c th hiu v thy c tm quan trng ca phn h IMS trong kin trc mng tng lai.

Ni dung ca chuyn bao gm:

Chng 1: Tng quan v IMS

Chng 2: Kin trc phn h v cc giao thc trong IMS

Chng 3: Cc yu cu v ng dng IMS Do qu trnh thc hin chuyn ch da trn l thuyt v tm hiu ti liu, cha c tip xc thc t v c cc m hnh thc tin tip cn v cn hn ch v mt thi gian nn nhiu vn cha th trnh by r v chc chn khng trnh khi nhng thiu st. Rt mong c s thng cm v ng gp kin ca thy v cc bn chuyn c hon chnh hn. Xin chn thnh cm n!

H Ni, thng 10 nm 2011.

Nhm thc hin chuyn .

CC THUT NG VIT TTT vit ttTing AnhTing Vit

3GPP3 Generation Partnership ProjectD n hp tc th h 3

AAAAuthentication, Authorization, AccountingNhn th trao quyn v thanh ton

APIApplication program interfaceGiao din lp trnh ng dng

ASApplication ServerServer ng dng

ATMAsynchronous Transfer ModePhng thc truyn ti khng ng b

BGCFBreakout gateway controll funtionChc nng iu khin cng chuyn mng

BSBearer serviceDch v mang

CAMELCustomized Application for Mobile Network services Enhanced LogicMng Logic cao cp ca nhng ng dng

CCFCall Control FunctionChc nng iu khin phin cuc gi

CDRCall Detail RecordBn ghi chi tit cuc gi

CLECCompetitive Local Exchange CarrierNh cung cp tng i ni ht cnh tranh

CNCore networkMng li

CSCircuit switchedChuyn mch knh

CSCFCall session control functionChc nng iu khin phin cuc gi

DHCPDynamic Host Configuration ProtocolGiao thc cu hnh host ng

DNS Domain Name SystemH thng tn min

ETSIEuropean Telecommunication Standard InstituteVin chun vin thng chu u

GGSN Gateway GPRS Support NodeNode h tr GPRS cng

GSMGolbal System for MobileH thng di ng ton cu

HSSHome subscriber serverServer thu bao nh

I-CSCFInterrogating CSCFCSCF truy vn

IECInter Exchange CarrierNh cung cp dch v lin tng i

IETF Internet Engineering Task ForceNhm c trch k thut Inernet

IMIP multimediaa phng tin IP

IM CN SSIP Multimedia Core Network SubsystemPhn h mng li a phng tin IP

IMSIP Multimedia subsystemPhn h a phng tin IP

IMSIInternational Mobile Subscriber IdentifierNhn dng thu bao di ng ton cu

IP Internet ProtocolGiao thc Inernet

IP-CANIP-Connectivity Access NetworkMng truy nhp kt ni IP

ISDNIntegrated Services Digital NetworkMng s dch v tch hp

ISDNIntergrated Serviec Digital NetworkMng s tch hp a dch v

ISIM IMS SIMModul nhn dng thu bao IMS

ITU-TInternational Telecommunication Union-Telecommunication Standardization BureauTiu ban chun ho vin thng trong Lin minh vin thng quc t

LECLocal Exhange CarrierVt mang trong cc tng i ni ht

MGCFMedia Gateway Control FunctionChc nng iu khin cng phng tin

MGF Media Gateway FunctionChc nng cng phng tin

MMSMultimedia Message ServiecDch v bn tin a phng tin

MRFCMultimedia Resource Function ControlB iu khin ti nguyn a phng tin

MRFPMultimedia Resource Function ProcessB x l ti nguyn a phng tin

OSAOpen services ArchitectureKin trc dc v m

PCFPolicy Control FunctionChc nng iu khin hp ng

P-CSCFProxy CSCFCSCF-th quyn

PDNPacket Data NetworkMng d liu gi

PDPPacket Data ProtocolGiao thc d liu gi

PLMNPublic Land Mobile NetworkMng di ng mt t cng cng

PSTNPublic Switch Telephone NetworkMng in thoi cng cng

RABRadio Access BearerMang truy nhp v tuyn

S CSCF Serving CSCFCSCF phc v

SBCSession Border Controliu khin phin trung gian

SCSService Capability ServerServer c kh nng phc v

SDPSession Description ProtocolGiao thc m t phin

SGSNServing GPRS Support NodeNode h tr GPRS phc v

SGWSignalling GatewayCng bo hiu

SIMSubsciber Identifier ModulKhi nhn dng thu bao

SIPSession Initiation ProtocolGiao thc khi to phin

SLFSubscriber Locator FunctionChc nng v tr thu bao

SSFService Switching FunctionChc nng chuyn mch dch v

THIGTopology Hiding Interwork Gateway Cng tng tc n giao thc

UEUser Equipment Thit b ngi dng

UMTSUniversal Mobile Telecommunication SystemH thng thng tin di ng ton cu

URLUniversal Resource LocatorV tr ti nguyn ton cu

USIM UMTS SIMModul nhn dng thu bao UMTS

ETSIEuropean Telecommunications Standards InstituteVin chun ho vin thng Chu u

DANH MC CC HNH V

Hnh 1.1: Cc xu hng pht trin mng vin thng

Hnh 1.2: Xu hng pht trin mng v dch v

Hnh 1.3: Xu hng tin ho ln mng NGN ca cc mng hin ti

Hnh 1.4: Chin lc pht trin mng NGN

Hnh 1.5: S hi t cc mng vin thng hin ti

Hnh 1.6: Pht trin mng NGN trn c s mng hin c

Hnh 1.7: Pht trin mi mng NGN

Hnh 1.8: Kh nng hi t mng ca IMS.

Hnh 1.9: V tr ca IMS trong mng NGN

Hnh 2.1: Kin trc phn lp ca IMS.

Hnh 2.2: Cc my ch ng dng IMS.

Hnh 2.3: Kin trc cc CSCF.

Hnh 2.4: Kin trc MRF.

Hnh 2.5: Kt ni IMS v mng PSTN/CS.

Hnh 2.6: IMS-ALG v TrGW.

Hinh 2.7: mang truy nhp ti IMS.

Hinh 2.8: Cac im tham chiu trong IMS.

Hnh 2.9: Cc thnh phn SIP.

Hnh 2.10: Lung bn tin bo hiu

Hnh 2.11: Lung bn tin bo hiu thit lp phin ng k

Hnh 3.1: Push to talk over Cellular

DANH MC CC BNG BIU

Bng 1.1: So snh cc cng ngh s dng trong mng truyn thng v mng NGNBng 2.1: Cc im tham chiu lin kt cc chc nng trong mng li IMS.

Bng 2.2: Ti liu v nhn thc trao quyn v thanh ton

Chng 1: Tng quan v IMS

1.1 Xu hng pht trin ca dch v v mng vin thng

1.1.1. Xu hng pht trin ca vin thng

Cng vi s pht trin khng ca khoa hc k thut, th in t - Vin thng l mt lnh vc c nhng pht trin vt bc t c nhng thnh tu to ln, cng ngh tin tin v ang c p dng vo thc t p ng c yu cu v cht lng, a dch v v kh nng dung lng cung cp

Nhng xu hng pht trin cng ngh v ang tip cn nhau, an xen ln nhau nhm cho php mng li tho mn tt hn cc nhu cu ca khch hng trong tng lai. Th trng vin thng trn th gii ang ng trong xu th cnh tranh v pht trin hng ti mng vin thng ton cu to ra kh nng kt ni a dch v trn phm vi ton th gii Xu hng pht trin cng ngh in t-vin thng-tin hc ngy nay trn th gii c ITU th hin mt cch tng qut trong hnh sau:

Hnh 1.1: Cc xu hng pht trin mng vin thng

Trong cc dch v vin thng c chia thnh hai loi:

- Hot ng hng kt ni.

- Hot ng khng kt ni

Hot ng hng kt ni: Cc cuc gi trong mng vin thng, PSTN, ISDN l cc hot ng hng kt ni, cc cuc gi c thc hin vi trnh t: thit lp cuc gi (quay s-xc nhn kt ni)-gi v nhn thng tin-kt thc. Vi cht lng mng tt, cc hot ng hng kt ni lun lun m bo cht lng dch v thng tin. Cng ngh ATM pht trin cho php pht trin cc dch v bng rng v nng cao cht lng dch v.Hot ng khng kt ni: Khc vi cc cuc gi quay s trc tip theo phng thc hng kt ni, cc hot ng thng tin da trn giao thc IP nh vic truy nhp Internet khng yu cu vic xc lp trc cc kt ni, v vy cht lng dch v c th khng c m bo. Tuy nhin do tnh n gin, tin li vi chi ph thp, cc dch v thng tin theo phng thc hot ng khng kt ni pht trin rt mnh theo xu hng nng cao cht lng dch v v tin ti cnh tranh vi cc dch v thng tin theo phng thc hng kt ni.

Hai xu hng pht trin ny dn tip cn v hi t vi nhau tin ti ra i cng ngh ATM/IP.

S pht trin mnh m ca nhu cu dch v v cc cng ngh mi tc ng trc tip n s pht trin cu trc mng.

Hnh 1.2: Xu hng pht trin mng v dch v

1.1.2.Mng vin thng trn con ng tin ti NGN

Trong nhiu nm gn y, nn cng nghip Vin thng ang ng trc mt la

chn pht trin cng ngh c bn no v s dng mng g h tr cng ngh

mng . Khi nim mng th h sau NGN ra i cng vi vic ti kin trc mng, tn dng cc u th v cng ngh tin tin ca cc cng ngh c nhm a ra nhiu dch v mi, mang li li ch cho nh khai thc v p ng nhu cu ca ngi s dng.

Mt chin lc pht trin t mng hin ti sang kin trc mng mi l rt quan trng nhm gim thiu yu cu u t trong giai on chuyn tip, sm tn dng c cc u im ca mng NGN. Tuy nhin bt k bc i no trong tin trnh chuyn tip ny cng cn to iu kin d dng hn cho bc pht trin chung ln NGN da trn nn chuyn mch gi. Bt c mt chin lc pht trin no cng cn phi tn dng li c s h tng mng truyn thng bn cnh cc thnh phn mng mi.

Cc nguyn tc c bn xy dng mng NGN nh sau:

- p ng nhu cu cung cp cc loi hnh dch v vin thng phong ph a dng, a dch v, a phng tin.

- Kin trc mng n gin.

- Hiu qu s dng mng, cht lng mng cao v gim thiu cc chi ph khai thc bo dng.

- D dng m rng dung lng, pht trin cc thnh phn, cc dch v mi.

- Tnh linh hot cao, v nng lc tn ti mnh.

Xu hng pht trin ln mng NGN t cc mng hin ti c th hin trong hnh sau:

Hnh 1.3: Xu hng tin ho ln mng NGN ca cc mng hin ti

Trong hnh, ta thy cc mng vin thng hin ti gm nhiu mng ring l kt hp li vi nhau thnh mt mng tng hp nhm mc ch p ng cc dch v ring l. Do , vic xy dng mng NGN phi m bo cc tiu ch sau:

1.Mng NGN c kh nng h tr tt c cc dch v ca cc mng hin ti trn nn

mng Internet.

2. Mng NGN phi h tr nhiu loi hnh dch v ca nhiu nh cung cp khc nhau. Mi nh cung cp hay dch v l mt thc th ring l c lp. C th s dng cc giao thc khc nhau.

3. Mng NGN phi h tr tt c cc loi kt ni cho c mng di ng v c nh.

V vy, mng NGN c xy dng t cc mng hin ti (pht trin thm chuyn mch gi) kt hp vi mng Internet (h tr thm QoS). Chin lc pht trin sang mng NGN c th hin nh trong hnh v sau:

Hnh 1.4: Chin lc pht trin mng NGN

thc hin vic chuyn dch ny mt cch thun li t mng vin thng hin c sang mng NGN th vic chuyn dch phi thc hin 3 mc.

Trc ht, vic chuyn dch phi c thc hin lp truy nhp v truyn dn. hai lp ny bao gm lp vt l, lp 2 v lp 3 nu chn cng ngh IP cho mng th h mi.

- Lp vt l s dng cng ngh truyn dn quang.

- Cng ngh truyn ti IP/MPLS lm nn cho lp 3.

- Cng ngh lp 2 phi m bo:

+ Cng n gin cng tt.

+ c bit tng hiu nng i vi truyn ti gi.

+ Kh nng gim st cht lng, gim st v s li.

Xy dng mng truy nhp bng rng (nh xDSL, LAN, Modem cable) c th cung cp phng thc truy nhp tc cao hng n phn nhm cho thu bao, cho php truy nhp chung vi tc cao hn hin nay.

Th hai, l chuyn dch mng ng di (mng truyn dn). S dng cng mng trung k tch hp hoc c lp, chuyn n mng IP hoc ATM, ri s dng chuyn mch mm iu khin lung v cung cp dch v. S dng phng thc ny c th trnh c vn tc nghn trong chuyn mch knh.

Hnh 1.5: S hi t cc mng vin thng hin ti

Cc cng ngh mng c s dng trong mng NGN bao gm cc cng ngh mng trong cc mng truyn thng v cc cng ngh mng mi vi hiu nng cao hn. So snh cc cng ngh trong mng truyn thng v mng NGN ta c bng sau:

Cc thnh phn mngCng ngh trong mng truyn thngCng ngh trong mng NGN

Mng truy nhp- Cp xon i bng hp

- Truyn hnh cp s v trng tng t

- GSM v tuyn

- Cp quang- Cp xon i bng hp

- Truy nhp v tuyn GSM

- Truyn hnh cp

- Cp quang

- Cp xon bng rng

- Modem cable

- Ethernet v Giga Ethernet

- V tinh

Chuyn mch v nh tuyn- nh tuyn IP

- Chuyn mch khe thi gian

- Chuyn mch ATM

- Chuyn mch Frame Relay- nh tuyn IP

- Chuyn mch quang

- Chuyn mch mm

- Chuyn mch ATM

Mng ng trc- Truyn dn quang PDH

- Truyn dn quang SONET SDH- Truyn dn quang SONET SDH

- H thng quang ghp knh theo bc sng WDM

Bng 1.1: So snh cc cng ngh s dng trong mng truyn thng v mng NGN

Th ba, s chuyn dch trong mng ni ht. Cc dch v trong mng NGN rt phong ph, bao gm c dch v bng hp ln dch v bng rng a phng tin. c th s dng c ti a cc dch v ny, mng ni ht phi chuyn dch t truy nhp bng hp sang truy nhp bng rng. Cc truy nhp qua cp xon i bng hp c thay th bng cc truy nhp qua ADSL, Modem cable, c bit l trin khai h thng Fiber to the Home. Hn na, cc tng i in thoi c rt nhiu gi my v lu tr c s d liu thu bao rt ln, nn vic nng cp cng gp rt nhiu kh khn. Nn khi chuyn dch yu cu phi s dng ti u c s d liu hin c.

Trn c s nguyn tc t chc nh vy, cc phng thc xy dng, pht trin mng th h sau NGN c th chia thnh hai khuynh hng nh sau:

1) Pht trin dch v mi trn c s mng hin c tin ti pht trin mng NGN. y l xu hng i vi nhng nc c.

- Mng vin thng v ang pht trin hin i ho.

- Cc dch v hin ti pht trin trn c s mng hin c.

- C cc nhu cu pht trin dch v mi.

Hnh 1.6: Pht trin mng NGN trn c s mng hin c

Nh vy theo hng ny, mng NGN c pht trin theo nhu cu dch v trn c s mng hin ti.

2) Xy dng mi mng NGN

Hnh 1.7: Pht trin mi mng NGN

- Mng NGN c xy dng vi nhim v trc mt l m bo cc nhu cu v dch v mng hin nay.

- Tin ti pht trin cc nhu cu v dch v mi.

- Cc dch v mi c trin khai trn mng NGN.

y l xu hng pht trin ca nhng nc c mng vin thng cha c hin i ho, cc nhu cu ch yu l cc dch v vin thng c bn hin ti, cha c nhiu nhu cu dch v mi. Con ng pht trin ln NGN l xy dng mi hon ton tin thng ln NGN.

1.2 Tng quan v IMS1.2.1 Khi nim IMS

IMS - thut ng vit tt ca IP Multimedia Subsystem, l mt phn ca kin trc mng th h k tip c cu thnh v pht trin bi t chc 3GPP v 3GPP2 h tr truyn thng a phng tin hi t gia thoi, video, audio vi d liu v hi t truy nhp gia 2G, 3G v 4G vi mng khng dy.

IMS l mt kin trc mng nhm to s thun tin cho vic pht trin v phn phi cc dch v a phng tin n ngi dng, bt k l h ang kt ni thng qua mng truy nhp no.

IMS h tr nhiu phng thc truy nhp nh GSM, UMTS, CDMA2000, truy nhp hu tuyn bng rng nh cp xDSL, cp quang, cp truyn hnh, cng nh truy nhp v tuyn bng rng WLAN, WiMAX. IMS to iu kin cho cc h thng mng khc nhau c th tng vn (interoperability) vi nhau, l phn mng c xy dng b sung cho cc mng hin ti nhm thc hin nhim v hi t mng v cung cp dch v a phng tin cho khch hng u cui.

IMS h tr nhiu loi hnh dch v khc nhau, bao gm cc dch v nhn tin tc thi (Instant Messaging - IM), hi ngh truyn hnh (Video Conferencing) v Video theo yu cu (Video on Demand - VoD). IMS cng c kh nng cung cp cc c ch xc thc v chuyn i gia cc mng khc nhau cho khch hng di ng. Sau , cc t chc chun ha nh ITU, ETSI chn IMS lm nn tng cho mng hi t.

Hnh 1.8. Kh nng hi t mng ca IMS.

Mt trong nhng mc ch u tin ca IMS l gip cho vic qun l mng tr nn d dng hn bng cch tch bit chc nng iu khin v chc nng vn ti thng tin. Mt cch c th, IMS l mt mng ph (overlay), phn phi dch v trn nn h tng chuyn ni gi. IMS cho php chuyn dn t mng chuyn ni mch sang chuyn ni gi trn nn IP, to thun li cho vic qun l mng thng tin di ng. Vic kt ni gia mng c nh v di ng gp phn vo tin trnh hi t mng vin thng trong tng lai. IMS cho php ngi dng c th s dng mt hay nhiu loi thit b khc nhau, di chuyn t mng ny sang mng khc m vn c th dng cng mt dch v.

IMS s dng cc giao thc c chun ha nh SIP (iu khin, thit lp phin), COPS ( m bo QoS) v Diameter (cung cp cc c ch nhn thc, xc thc v truy nhp CSDL thu bao). IMS c kh nng bo mt tt vi nhiu c ch bo v khc nhau ngn chn s tn cng t bn ngoi v kim sot ngi dng truy nhp t cc mng khc.

cc u cui ng dy c th truy nhp c lp vi vn hnh v bo dng qua mng Internet, phn h a phng tin IP c gng tng thch vi cc chun IETF (chun Internet). Trong mt s trng hp l ly chun giao thc ca IETF, do cc giao din ny tng thch hp l vi cc chun Internet v d nh giao thc SIP. . . .

Cc nh cung cp dch v vin thng ang chuyn dch v thoi truyn thng sang VoIP ti u cho gi thnh u t v gi thnh dch v. Tuy nhin nu ch chuyn sang mi mng VoIP th vn khng gii quyt ht nhng lo u v gi thnh u t, gi cc thu nhp v cn phi tng nhiu chi ph mi. Khi dch v thoi chuyn sang mng IP, n s tr thnh mt phn ca b cc dch v truyn thng hng kt ni a phng tin thi gian thc chy trn mng IP v cng chia s mt s sp xp client-server chung nh dch v tin khn, cuc gi khn, hi ngh mng v cc dch v VoIP, 3G Thm vo VoIP c th h tr lp cc dch v mi nh dch v a phng tin, dch v tch hp th cn c mt nn tng chuyn tip dch v mi. Nn tng y c chn chnh l IMS (IP Multimedia Subsystem) do 3GPP nh ngha v pht trin. Gii php ca h l thoi th h k tip vi h thng d liu, phn mm v cc dch v chuyn nghip, p ng mng cn hot ng c mng ng dy v mng khng dy.

1.2.2 S cn thit ca IMS trong mng NGN IMS (IP Multimedia Subsystem )l mt phn trong kin trc ca mng th h k tip NGN.V tr ca IMS trong mng th h sau NGN c th hin trong hnh v sau :

Hnh 1.9.V tr ca IMS trong mng NGN

IMS l mt kin trc mng m nh ngha tng phn t chc nng. Mi phn t chc nng khng bao gm mi lin kt mt mt vi phn t vt l. Mt s phn t chc nng c th hp nht trong mt phn t vt l. Kin trc dch v nh ngha phng php chun cho dch v c gii thiu trong khi mng li nh ngha s tng tc gia cc phn t chc nng.

+ IMS l phn h a phng tin IP. Tuy nhin chng ta cn n cung cp dch v ngoi dch v thoi c bn. C th l thoi, video, hoc hnh nh hoc mt s kt hp tng quan gia hai hoc nhiu loi.

+ IMS bt u vi 3GPP v ETSI, c hai u c ngun gc t Chu u. gii thiu IMS M c mt vi iu thng phi thng qua m s iu chnh cho thch hp vi c trng ca M.

+ IMS da vo cc chun ha hin nay c pht trin ca IETF. T chc trnh by IMS cng tc ng ti IETF tc ng tch cc, lm pht trin cc chun mi

cn tin cho hon thin IMS.

+ Hi t C nh Di ng l mt t mi lan truyn trong cng nghip. ng dng ca IMS c mong i ca cc mng khng dy, ng dy, cable, cc cng trnh v cc mng khc.

+ Mt trong cc thuc tnh ch yu, m c th phi tr nhiu hn trong mng khng dy l tng

+ C mt s tha nhn m IMS phi tin ha n mng v iu cn thit kt ni gia cc chc nng hin ti v cc kh nng mi trong tng lai.

Tm li : IMS trong NGN thc hin 3 chc nng chnh trong mng NGN:

+ Hi t mng di ng v mng c nh

+ Hi t dch v. Cung cp dch v truyn thng a phng tin trn nn gi IP

+ Hi t u cui.

1.3. Lch s pht trin IMS

IMS l mt kin trc xut hin u tin trong gii php pht trin cc mng 2G ln mng 3G. H thng ton cu cho thng tin di ng (GSM) c chun ho hon ton bi Vin cc chun vin thng Chu u (ETSI) vo nm 1998. ETSI cng nh ngha kin trc mng GPRS. Cng nm , 3GPP cng a ra h thng thng tin di ng th h th ba bao gm: cc mng a truy nhp phn chia theo m bng rng (WCDMA), a truy nhp v tuyn phn chia theo m/phn chia theo thi gian (TD-CDMA) v gii php mng li GSM. Hu ht cng vic v l thuyt nn tng ca 3GPP a ra c k tha t cc nhm di ng ca ETSI. Release IMS u tin m 3GPP a ra l Release 99 [3GPP R99].3GPP Release 99 (3GPP R99)

Release IMS u tin c a ra vo thng 12 nm 1999, nhng mi n thng 3 nm 2001 mi c hon thin hon ton v c chc nng cng nh nhng l thuyt c bn. S d Release 99 c hon thin nhanh chng nh vy l v vic chun ho c phn chia gia hai t chc: 3GPP v ETSI SMG. Trong , 3GPP chu trch nhim pht trin cc dch v, kin trc h thng, truy nhp v tuyn WCDMA, TD-CDMA v mng li chung cn ETSI SMG chu trch nhim pht trin truy nhp v tuyn vi tc d liu tng cng cho tin trnh ton cu (EDGE)/GSM.

Truy nhp v tuyn WCDMA l s tng cng c ngha quan trng nht cho h thng 3G da trn GSM trong R99. Ngoi WCDMA th UTRAN (mng truy nhp v tuyn mt t UMTS) cng a ra giao din Iu. Giao din ny so vi cc giao din Gb v A c hai s khc nhau l: tc chuyn m cho Iu c thc hin trong mng li cn trong GSM c thc hin chc nng logic BTS (trm thu pht gc); qu trnh mt m v qun l tnh di ng mc t bo cho giao din Iu c thc hin trong b iu khin mng v tuyn (RNC) cn trong GSM chng c thc hin trong nt h tr GPRS phc v (SGSN) cho cc dch v GPRS.

Kin trc dch v m (OSA) c a ra to dch v. Mc tiu ca kha cnh dch v l dng chun ho cc dch v mi v tp trung vo pht trin kh nng dch v hin ti.

3GPP Release 4

Sau Release 1999, 3GPP bt u a ra Release 2000 vi khi nim ton IP, sau i li thnh IMS. IMS khng th c hon thnh trong nm 2000. Do , Release 2000 c chia thnh Release 4 v Release 5.

Release 4 c a ra vo thng 3 nm 2001 v c hon thnh m cha c IMS. Cc chc nng mi c ngha quan trng trong Release 4 ca 3GPP l: khi nim MSC Server-MGW, cc giao thc mng li truyn ti IP, phn t tng cng cc tn hiu quyt nh ng truyn - LCS (Line Conditioning Signals) cho UTRAN v truyn tin a phng tin v mt bng ngi dng Gb truyn ti IP.

3GPP Release 5 v Release 6

Cui cng R5 a IMS vo nh mt trong cc chun ca 3GPP. IMS h tr kin trc da trn truy cp IP c lp m tng tc vi cc mng thoi v d liu hin ti cho c ngi dng c nh (v d nh PSTN, ISDN, Internet) v di ng (v d nh GSM, CDMA). Kin trc IMS thit lp truyn thng IP peer-to-peer cho tt c cc loi client vi QoS yu cu. Ngoi s qun l phin, kin trc IMS b sung cc chc nng cn thit cho vic hon thnh phn phi dch v (v d nh ng k, an ninh, cc ph, iu khin knh mang, chuyn vng). Ni chung, IMS s hnh thnh tri tim ca mng li IP.

R5 c hon thnh bi 3GPP vo thng 3 nm 2002 nhng nhiu c tnh cha c hon thin v b tr hon sang Release tip theo R6. Ni dung cng vic tip tc c hon thin v 21 thng sau c mt s thay i th hin trong R5 IMS.

R6 IMS s b sung thit st trong R5 IMS v a ra cc c tnh mi. R6 c hon thnh vo nm 2004. ch ra mt s c tnh quan trng ca R5 v cc thut ng tr hon trong R6 cho thy 3GPP nh ngha mt kin trc cho cc dch v a phng tin IP da trn SIP. N bao gm chc nng ca cc phn t logic, cc phn t kt ni, giao thc la chn v cc th tc.

iu quan trng thc s chnh l ti u cho vic thit k mi trng truyn thng di ng theo mu nhn thc v trao quyn ngi dng da trn cc quy tc xc nh, nhn dng tnh di ng ti giao din mng-ngi dng cho vic nn cc bn tin, an ninh v cc c ch iu khin chnh sch SIP cho php pht hin tn tht v khi phc v tuyn. Hn na, cc kha cnh quan trng t ci nhn ca nh khai thc l vic nh a ch trong khi trin khai kin trc, nh khung tnh cc v iu khin dch v v chnh sch. 1.4. u nhc im ca IMS

1.4.1 u im ca IMS

IMS cho php ngi dng c th s dng s dng mt hay nhiu loi thit b khc nhau, di chuyn t mng ny sang mng khc m vn c th dng cng mt dch v.

Kin trc IMS cung cp nhiu gi tr gia tng cho nh cung cp mng, ngi pht trin ng dng, ngi cung cp dch v cng nh ngi s dng cc thit b u cui. Kin trc IMS gip cc dch v mi c trin khai mt cch nhanh chng vi chi ph thp. IMS cung cp kh nng tnh cc phc tp hn nhiu so vi h thng ti khon tr trc hay tr sau, v d nh vic tnh cc theo tng dch v s dng hay phn chia cc gia cc nh cung cp dch v v nh cung cp mng. Khch hng s ch nhn mt bng tnh cc ph duy nht t mt nh cung cp mng thng tr. IMS ha hn mang n nhiu dch v a phng tin, giu bn sc theo yu cu v s thch ca tng khch hng, do tng s tri nghim ca khch hng (customer experience).

Vi IMS, nh cung cp mng s khng ch lm cng tc vn ti thng tin mt cch n thun m tr thnh tm im trong vic phn phi dung lng thng tin trong mng, ng vai tr quan trng trong vic m bo cht lng dch v cng nh kp thi thay i p ng cc tnh hung khc nhau ca khch hng.

Tm li: IMS to thun li cho cc nh cung cp dch v trong vic xy dng v trin khai cc ng dng mi, gip nh cung cp mng gim chi ph trin khai, vn hnh v qun l, ng thi tng li nhun nh cc dch v mi. V cui cng IMS mang li nhng dch v mi hng n s tin nghi cho khch hng.

1.4.2 Nhc im ca IMS

IMS ang thiu mt m hnh kinh doanh c sc thuyt phc cc nh cung cp mng chp nhn trin khai IMS. im ni bt ca IMS l hng n mt m hnh mng hi t. Tuy nhin, iu ny khng d dng thuyt phc mt nh cung cp mng trin khai IMS. Vi IMS, khch hng ng k vi mt nh cung cp mng (network operator) c th dng dch v ca nhiu nh cung cp dch v (service providers) khc nhau. Do vy, IMS s dn n s cnh tranh gia nh cung cp mng v nhng nh cung cp dch v ni dung ca th gii Internet (Microsoft, Google). Thay v tng thm li nhun nh cc dch v gi tr gia tng, nh cung cp mng c th s phi chu tht bi trong vic cnh tranh vi cc nh cung cp dch v. Do vy, nhiu nh cung cp mng ang cn rt d dt khi quyt nh trin khai IMS. y l mt vn mang tnh chin lc ch khng phi l mt vn v cng ngh.

V mt k thut, mt trong nhng im yu m nhiu ngi nhc n nhiu nht l tnh bo mt ca IMS. Trong cc yu t v bo mt c th k n cc vn lin quan n qun l nhn dng ngi dng bao gm cc li nh Call ID spoofing, n cp ID, tn cng DoS/DDoS, spam. im yu bo mt nm thit b SIP v n cha c mt c ch chng nhn thc tt nh trong mng thng tin di ng t bo (v d bo mt qua SIM). Thm vo l s hi t gia nhiu loi hnh mng cng gy khng t kh khn trong vic qun l bo mt. Hin ti, Release 8 ca 3GPP ang xem xt mt cch nghim tc vn bo mt ny.

IMS hng n hi t, hng n vic nhiu h thng, nhiu mng c th tng vn vi nhau. Tuy nhin, y cng chnh l mt kh khn m IMS ang gp phi. Vic cc thit b c ngun gc t nhiu nh sn xut khc nhau c th tng vn c vi nhau khng phi l mt iu d dng. Bn cnh , nhiu giao thc cng cha c chp nhn v trin khai rng ri, v d nh trng hp ca giao thc DIAMETER.

IMS ch tp trung n qun l dch v, do thiu cc ng dng hp dn mang c th ring ca IMS. a phn cc dch v m IMS hin ang h tr u c th thc hin c khng cn n IMS (v d s dng SIP). H thng IMS kh phc tp v chi ph trin khai mt h thng nh th l khng nh. Bn cnh , hin cha c gii php cho vic chuyn tip dn t mng hin ti ln IMS. V mt cu hi t ra l liu cc nh cung cp mng c th s dng li nhng dch v tn ti m khng cn phi thay i qu nhiu. IMS hng n dch v a phng tin, tuy nhin tnh n thi im ny cc dch v nh P2P, IPTV, VPN cn cha c tch hp v chun ha trn nn IMS.

Mc d IMS nhm n vic m bo cht lng dch v nhng vic m bo cht lng dch v khi chuyn i t loi hnh mng ny sang loi hnh mng khc (trong mi trng mng hi t), hay t mng ca nh cung cp mng ny sang mng ca nh cung cp mng khc vn cn l mt vn cha c gii quyt. Kin trc IMS thiu mt thc th trung tm qun l ti nguyn chung. Bi ton qun l di ng, chuyn giao gia nhiu loi hnh mng khc nhau, cng t ra nhng kh khn nht nh cho vic cung cp qun l dch v IMS.

Bn cnh cc chc nng k trn, mun vn hnh tt IMS cn phi c cc chc nng theo di, qun l v sa li ca h thng. Trong mi trng mng hi t, nu mt cuc gi b rt, cha c mt c ch no c th xc nh v tr din ra li (debugging).

IMS l mt gii php ha hn cho vic qun l dch v trong th h mng tip theo. IMS l mt bc i mang tnh chin lc lu di ca nhiu cng ty v tp on vin thng. Trong thi gian ngn sp ti, s cn nhiu thay i xoay quanh gii php IMS nhm hon thin nhng im yu ca n. Tt c nhng gii php IMS hin ti ch l mt gii php sm (early IMS), gii php IMS y (full IMS) vn cn ang trong giai on nghin cu v chun ha.1.5. Kt lun chng 1.

Chng 1 gii thiu tng quan v IMS, nhng khi nim c bn lin quan n IMS, trnh by v xu hng pht trin ca IMS trong lnh vc dch v ca vin thng, nhng u im v nhng hn ch khi s dng IMSChng 2: Kin trc phn h v cc giao thc trong IMS2.1. Gii thiu

IMS l mt chun da trn mng vin thng ton IP m n s dng c mng c dy v khng dy hin ti vi s a dng cc dch v a phng tin bao gm: audio, video, thoi , vn bn, v d liu.

2.2. Kin trc v chc nng cc phn t trong IMS.

IMS chng ta cn ch mt iu rng 3GPP khng chun ha cc node m l cc chc nng. iu ny c ngha rng kin trc ca IMS l s t hp ca cc chc nng c gn kt vi nhau thng qua cc giao tip c chun ha.

Kin trc IMS c phn thnh 3 lp : lp dch v (lp ng dng), lp iu khin (hay cn gi l lp IMS hay IMS li) v lp truyn ti (hay lp ngi dng).

Hnh 2.1. Kin trc phn lp ca IMS.

a. Lp dch v bao gm cc my ch ng dng AS (Application Server) v cc my ch thu bao thng tr HSS (Home Subscriber Server).

b. Lp iu khin bao gm nhiu h thng con trong c h thng IMS li.

c. Lp truyn ti bao gm thit b ngi dng UE (User Equipment), cc mng truy nhp kt ni vo mng li IP. Hai thc th chc nng NASS v RACS nh ngha bi TISPAN c th c xem nh thuc lp vn ti hay thuc lp iu khin trn.

2.2.1. Lp dch v.2.2.1.1. My ch ng dng (Appication Server - AS).

AS l mt thnh phn SIP, thc hin chc nng tip nhn v x l dch v. Ty thuc vo dch v thc t m AS hot ng trong ch SIP Proxy, SIP UA hay SIP B2BUA. Cc AS kt ni vi S-CFCS thng qua giao tip SIP. C 3 loi AS: SIP AS, OSA-SCS, IM-SSF. Cc my ch OSA-SCS, IM-SSF ng vai tr lm cu ni IMS giao tip vi OSA v gsmSCF. Ngoi ra cc my ch c th c kt ni ti HSS ti v hoc gi ln cc thng tin d liu ca khch hng. SIP AS, OSA-SCS giao tip vi HSS thng qua giao thc Diameter trong khi IM-SSF s dng giao tip MAP (Mobile Application Part).

AS c th t mng nh hoc mng ngoi m nh iu hnh mng nh xc nhn s ng dch v. Nu AS t ngoi mng nh, n khng tng tc vi HSS.Cc AS c m t theo Hnh 2.2:

Hnh 2.2. Cc my ch ng dng IMS.

SIP AS: y l AS th ng thc hin chc nng tip nhn v x l cc dich v a phng tin IP da trn nn SIP. My ch tim tr phc v OSA: OSA-SCS (Open Service Access Service capability Server): AS ny cung cp mt giao tip n my ch ng dng truy nhp dch v m (OSA), tha hng tt c cc tnh nng ca OAS c bit l kh nng truynhp bo mt t cc mng bn ngoi. OSA-SCS giao tip vi my ch ng dng OSA thng qua giao din lp trnh ng dng API (Application Programming Interface). Chc nng chuyn mch a dch v IP: IM-SSF (IP Multimedia Service Switching Function): y l my ch ng dng c bit cho php IMS ti s dng li dch v logic cao cp ca nhng ng dng theo yu cu khch hng mng di ng (CAMEL - Customized Applications for Mobile network Enhanced Logic) m c pht trin trong h thng GSM. IM-SSF cho php chc nng iu khin dch v GSM (GMSSCF GSM Service Control Function) thc hin iu khin cc phin IMS. IM-SSF giao tip vi GMSCSF thng qua giao tip CAP (CAMEL Application Part).2.2.1.2. My ch qun l C s d liu (CSDL) HSS v SLF.

May chu quan ly thu bao thng tr HSS (Home Subscriber Server) l trung tm lu tr cho thng tin ngi dng, n c pht trin t HLR (Home Location Register) trong h thng GSM. HSS l mt c s d liu lu tr thng tin ca tt cc cc thu bao khch hng. D liu ny bao gm thng tin v tr, thng tin bo mt (bao gm c thng tin nhn thc v cho php), thng tin h s thu bao (bao gm cc dch v m ngi dng ng k) v S-CSCF c phn b cho thu bao Trong mt mng IMS c th c nhiu hn mt HSS, thng thng HSS c xy dng theo c ch c d phng trnh b mt thng tin khi c li xy ra.

Chc nng nh v thu bao SLF (Subscriber location Function) l mt CSDL nhm xc nh thng tin ca khch hng ang c lu trn HSS no. Chnh v vy vi nhng mng m ch c 1 HSS th khng yu cu phi c SLF, tuy nhin trong trng hp c nhiu HSS trong cng mt mng, chc nng nh v ngi dng SLF s c thit lp nhm xc nh HSS no ang cha h s ca ngi dng tng ng. C HSS v SLF u hot ng theo giao thc Diameter vi ng dng dnh ring cho IMS.

2.2.2. Lp li IMS.

Chc nng ca li IMS l qun l vic to lp phin lin lc v dch v a phng tin. Cc chc nng ca n bao gm:

2.2.2.1. Chc nng iu khin phin gi (CSCF - Call Session Control Function).

Chc nng ny l c bit cn thit cho IMS, lm nhim v x l cc bn tin bo hiu SIP trong h thng IMS. CSCF c nhim v thit lp, theo di, h tr v gii phng cc phin a phng tin cng nh qun l nhng tng tc dch v ca ngi dng. Ty thuc vo chc nng m nh khai thc cung cp CSCF c 3 loi:

- P-CSCF (Proxy-CSCF).

- I-CSCF (Interrogating-CSCF).

- S-CSCF (Serving-CSCF).

Hnh 2.3. Kin trc cc CSCF

Proxy-CSCF (P-CSCF) l mt proxy SIP. S d gi l proxy v n c th nhn cc yu cu dch v, x l ni b hoc chuyn tip yu cu n cc b phn khc trong h thng IMS. P-CSCF l im kt ni u tin (chc nng bo hiu) gia cc u cui IMS v mng IMS - l im kt ni u tin gia h tng IMS v ngi dng IMS/SIP. Theo quan im t SIP th P-CSCF ng vai tr l mt my ch outbound/inbound SIP Proxy, iu ny c ngha rng tt c cc yu cu khi to phin c xut pht hoc gi n mt u cui IMS u phi chuyn giao qua P-CSCF sau n thc hin chuyn tip cc bn tin SIP yu cu v p ng ti hng tng ng.

kt ni vi h thng IMS, ngi dng trc tin phi ng k vi P-CSCF trong mng m n ang kt ni. Mt P-CSCF c ch nh cho mt u cui IMS trong sut qu trnh ng k v khng thay i trong khong thi gian ny. Chc nng ca P-CSCF bao gm:

- P-CSCF nm trn ng truyn ca tt c cc thng ip bo hiu trong h thng IMS. N c kh nng kim tra bt k thng ip no. P-CSCF c nhim v m bo chuyn ti cc yu cu t UE n my ch SIP ( y l S-CSCF) cng nh nhng thng ip phn hi t my ch SIP v UE, iu ny ngn chn qu trnh khi to cc bn tin khng ng theo khun dng ca SIP t cc u cui IMS.

- P-CSCF xc thc ngi dng v thit lp kt ni bo mt IPSec vi thit b IMS ca ngi dng. N cn c vai tr ngn cn cc tn cng nh spoofing, replay m bo s bo mt v an ton cho ngi dng. - P-CSCF cng bao gm cc chc nng nn v gii nn cc bn tin SIP. C ch ny gip gim c thi gian tr khi truyn lan cc bn tin SIP trong mng, gim thiu khi lng thng tin bo hiu truyn trn nhng ng truyn tc thp.

- P-CSCF c th tch hp chc nng quyt nh chnh sch PDF (Policy Decision Function) nhm qun l v m bo QoS cho cc dch v a phng tin. - P-CSCF cng tham gia vo qu trnh tnh cc dch v.

- P-CSCF c th c t trong mng ch hoc mng khch, i vi mng di ng da trn nn GPRS, P-CSCF lun c t cng v tr vi nt h tr cng vo ra GPRS (GGSN - Gateway GPRS Support Node).

Serving-CSCF (S-CSCF) l mt nt trung tm ca h thng bo tn hiu IMS. S-CSCF vn hnh ging nh mt my ch SIP nhng n bao hm c chc nng qun l phin dch v. Cc chc nng chnh ca S-CSCF bao gm:

- Tin hnh cc ng k SIP nhm thit lp mi lin h gia a ch ngi dng (a ch IP ca thit b) vi a ch SIP. S-CSCF ng vai tr nh mt my ch Registar trong h thng SIP, c ngha l S-CSCF duy tr mt lin kt gia v tr ngi dng (nh a ch IP m ngi dng log vo h thng) v bn ghi a ch SIP ca ngi dng.

- S-CSCF tham gia trong tt c cc qu trnh bo hiu t h thng IMS v ngi dng.N c th kim tra bt k thng ip no nu mun. - S-CSCF gi vai tr quyt nh chn la AS no s cung cp dch v cho ngidng.N gi vai tr nh tuyn dch v thng qua vic s dng gii php DNS/ENUM (Electronic Numbering).

- S-CSCF thc hin cc chnh sch ca nh cung cp dch v.S-CSCF tng tc vi my ch AS yu cu cc h tr dch v cho khch hng. S-CSCF lin lc vi HSS ly thng tin, cp nht thng tin v h s ngi dng v tham gia vo qu trnh tnh cc dch v.

- S-CSCF lun c t trong mng ch. Interrogating-CSCF (I-CSCF) trong h thng mng ca mt nh cung cp dch v l im lin lc cho tt c cc kt ni hng n mt UE nm trong mng . a ch IP ca I-CSCF c cha trong my ch DNS ca h thng. Chc nng ca I-CSCF bao gm:

- nh tuyn thng ip yu cu SIP nhn c t mt mng khc n S-CSCF tng ng. lm c iu ny, I-CSCF s lin lc vi HSS (thng qua DIAMETER) cp nht a ch S-CSCF tng ng ca ngi dng. Nu nh cha c S-CSCF no c gn cho UE, I-CSCF s tin hnh gn mt S-CSCF cho ngi dng n x l yu cu SIP.

- Ngc li, I-CSCF s nh tuyn thng ip yu cu SIP hoc thng ip tr li SIP n mt S-CSCF/I-CSCF nm trong mng ca mt nh cung cp dch v khc.

- I-CSCF cn m ho cc phn ca cc thng ip SIP m cha cc thng tin nhy cm v vng nh: s lng server trong vng, tn DNS hay dung lng ca chng. Chc nng ny cn c gi l THIG, n thng khng c trin khai bi hu ht cc mng.- I-CSCF thng t trong mng ch.Trong mt vi trng hp c bit (I-CSCF c tnh nng THIG) n c th c t mt mng khch.

2.2.2.2.Chc nng iu khin cng vo ra (BGCF).

MGCF ( Media Gateway Control Function) c nhim v qun l cng phng tin, bao hm cc chc nng nh: lin lc vi S-CSCF qun l cc cuc gi trn knh phng tin, lm trung gian chuyn i (conversion) gia giao thc bo hiu ISUP v SIP. MGCF qun l mt hay nhiu IM-MGW (IP Multimedia-Media Gateway). IM-MGW s tng tc vi MGCF qun l ti nguyn. IM-MGW ng vai tr l im chuyn i ni dung a phng tin gia mng chuyn ni gi v chuyn ni mch khi thng tin truyn t mng ny sang mng khc.

2.2.2.3. Chc nng iu khin cng truyn thng MGCF.

MGCF ( Media Gateway Control Function) c nhim v qun l cng phng tin, bao hm cc chc nng nh: lin lc vi S-CSCF qun l cc cuc gi trn knh phng tin, lm trung gian chuyn i (conversion) gia giao thc bo hiu ISUP v SIP. MGCF qun l mt hay nhiu IM-MGW (IP Multimedia-Media Gateway). IM-MGW s tng tc vi MGCF qun l ti nguyn. IM-MGW ng vai tr l im chuyn i ni dung a phng tin gia mng chuyn ni gi v chuyn ni mch khi thng tin truyn t mng ny sang mng khc.2.2.2.4. Chc nng ti nguyn truyn thng MRF.

Kin trc lin quan n chc nng ti nguyn a phng tin (MRF) c th hin trong hnh 2.4 nh sau:

Hnh 2.4. Kin trc MRF.

Chc nng ny cung cp ti nguyn truyn thng trong mng ch vi kh nng vn hnh thng bo, pha trn lung d liu, chuyn i cc loi m khc nhau v sp xp d liu c phn tch trong h thng IMS. MRF lun c t trong mng ch IMS.

Chc nng qun l ti nguyn a phng tin MRF (Media Resource Function) c th phn ra thnh 2 thnh phn: MRFC (Media Resource Function Controller) v MRFP (Media Resource Function Processor).

- MRFC c vai tr qun l ti nguyn cho cc dng d liu a phng tin trong MRFP (Media Resource Function Processor), gii m thng ip n t my ch ng dng AS truyn qua S-CSCF, iu khin MRFP tng ng cng nh tham gia vo qu trnh tnh cc.

- MRFP ng vai tr quan trng trong vic thch ng ni dng dch v, chuyn i nh dng (transcoding) ni dung.2.2.3. Lp truyn ti.

Chng ta xem NASS v RACF l 2 thnh phn thuc lp vn ti. Vi tr ca 2 thnh phn ny c miu t di y:

2.2.3.1. NASS (Network Attachment Subsystem).

Chc nng chnh ca NASS bao gm:

- Cung cp mt cch linh hot a ch IP cng nh cc thng s cu hnh khc cho UE (s dng DHCP).

Nhn thc ngi dng trc v trong qu trnh cp pht a ch IP.

Cp php cho mng truy nhp da trn h s mng.

Qun l nh v ngi dng.

H tr qu trnh di ng v roaming ca ngi dng.

2.2.3.2. RACF (Resource & Admission Control Functionality).

RACF bao gm 2 chc nng chnh l: chc nng quyt nh chnh sch dch v (S-PDF) v chc nng iu khin chp nhn kt ni v ti nguyn truy nhp (A-RACF).

S-PDF (Serving Policy Decision Function), di yu cu ca cc ng dng, s to ra cc quyt nh v chnh sch (policy) bng vic s dng cc lut chnh sch v chuyn nhng quyt nh ny ti A-RACF. S-DPF cung cp mt cch nhn tru tng v cc chc nng truyn ti vi ni dung hay cc dch v ng dng. Bng cch s dng S-DPF, vic x l ti nguyn s tr nn c lp vi vic x l dch v.

A-RACF (Access Resource and admission Control Function) nhn cc yu cu v ti nguyn QoS t S-PDF. A-RACF s s dng thng tin QoS nhn c t S-PDF quyt nh chp nhn hay khng chp nhn kt ni. A-RACF cng thc hin chc nng t trc ti nguyn v iu khin cc thc th NAT/Firewall.

2.2.3.3. PSTN/CS Gateway. PSTN gateway cung cp giao din n mng chuyn mch knh, cho php cc u cui IMS c th thc hin v nhn cc cuc gi n v t PSTN (hoc bt c mng chuyn mch knh no).

IMS kt ni ti mng PSTN/CS thng qua cng giao tip PSTN chc nng ny c phn chia thnh 3 chc nng nh: SGW, MGCF, MGW nh trong Hnh 2.5.

Hnh 2.5. Kt ni IMS v mng PSTN/CS.

Signalling Gateway (SGW) SGW giao din vi mt bng bo hiu ca mng chuyn mch knh. SGW chuyn i giao thc lp thp, v d, mt SGW chuyn MTP sang SCTP trn nn IP. Nhu vy, SGW chuyn i ISUP hay BICC trn MTP thnh ISUP/BICC trn SCTP/IP, SS7 chy trn nn IP. Media Gateway (MGW) MGW giao din vi mt bng phng tin ca mng chuyn mch knh. Mt mt n c th gi v nhn vi IMS qua RTP. Mt khc n s dng mt hay nhiu khe PCM kt ni vi mng chuyn mch knh. Hn na MGW thc hin chuyn m khi cc u cui IMS khng h tr cc kiu m ho c s dng bi CS (iu ny xy ra khi u cui IMS s dng m AMR cn u cui PSTN s dng kiu m ho G.711).

2.2.3.4. IMS GW v TrGW.

Nh ni, IMS h tr hai phin bn IP l IPv4 v IPv6. Ti mt s im ca mt phin, s lin mng gia hai phin bn ny c th xy ra. c th chuyn i gia IPv4 v IPv6 m khng cn mt thit b h tr no, IMS c thm hai thc th chc nng cung cp qu trnh chuyn i, l: IMS Application Layer Gateway(IMS- ALG) v Transition Gateway (TrGW). Hnh 1.6 th hin mi quan v gia IMS-ALG, TrGW v cc phn ca IMS. IMS-ALG ng vai tr nh mt SIP B2BUA duy tr 2 phn bo hiu c lp, mt hng n mng IMS v mt hng n mng khc. Mi phn ny chy trn 2 phin bn IP khc nhau.

Hnh 2.6. IMS-ALG v TrGW. Thm na, IMS-ALG s vit li SDP bng cch thay i a ch IP v s port c to bi u cui vi mt hay nhiu a ch IP v port c cp pht bi TrGW. IMS- ALG tng tc vi I-CSCF cho lu lng vo v vi S-CSCF cho lu lng ra qua giao din Mx. TrGW thc s l mt NAT-PT/NAPT-PT (Network Address Port Translator- Protocol Translator). N c cu hnh vi mt pool ca IPv4 c t ng cp pht cho mt phin. TrGW thc hin vic chuyn i ti mt bng phng tin (nh RTP, RTCP).2.2.3.5. Mng truy nhp.

Truy nhp n mng li thng qua cc border Gateway (GGSN/PDG/BAS):

+ Vi GPRS/UMTS, GGSN nhn thc UE v iu khin vic thit lp cc knh phng tin bng cch s dng PDP.SGSN kt ni RAN n mng li. N c nhim v thc hin c chc nng iu khin v x l lu lng cho mng PS. Phn iu khin gm hai chc nng chnh: qun l s thay i v qun l phin.

Hinh 2.7. mang truy nhp ti IMS.

Qun l thay i gim st v tr v trng thi ca UE v nhn thc c thu bao v UE. Qun l phin x l iu khin cho php kt ni v bt c thay i no trong nhng kt ni d liu hin c. X l lu lng l mt phn ca qun l phin.GGSN cung cp lin kt vi mng d liu gi bn ngoi (IMS hay Internet). Ni cch khch GGSN nh tuyn cc gi IP cha bo hiu SIP t UE n P-CSCF.+ Vi WLAN, PDG iu khin vic thit lp tunnel thng qua mng truy nhp n UE. Nhng tunnel ny c bo mt nhng khng c QoS.+ Vi 3GPP Release 7 h tr kt ni IP trn mng truy nhp hu tuyn qua DSL hay Cable.2.3. Cc im tham chiu IMS.

Hinh 2.8. Cac im tham chiu trong IMS.

im tham chiu IMS c nhim v l im ni gia cc thc th trong v ngoi mng IMS, trao i cc thng tin v bo hiu, tnh nng ca cc im tham chiu c m t trong Bng 2.1.imThc th

lin quanMc chGiao thc

CrMRFC, ASMRFC nhn t liu (cc kch bn v ti nguyn ) t mt ASHTTP

CxI-CSCF, S-CSCF, HSSThng tin gia HSS v I-CSCF/S-CSCFDiameter

DhSIP AS, OSA, SCF, IM-SSF, HSSAS s dng tm chnh xc HSS cn thit trong mi trng nhiu HSSDiameter

DxI-CSCF, S-CSCF, SLFI-CSCF/S-CSCF s dng tm chnh xc HSS cn thit trong mi trng nhiu HSSDiameter

GmUE, P-CSCFTruyn ti tt c cc bn tin bo hiu SIP gia UE v IMSSIP

GoPDF, GGSN

Cho php nh khai thc iu khin QoS trong mt phng ngi dng v chuyn i thng tin lin quan n tnh cc gia IMS v mng GPRSCOPS

GqP-CSCF, PDF

Truyn ti thng tin lin quan n quyt nh chnh sch gia P-CSCF v PDFDiameter

ISCS-CSCF, I-CSCF, ASTruyn ti tt c cc bn tin gia AS v CSCFSIP

MgMGCF - I-CSCFMGCF chuyn i bn tin bo hiu ISUP thnh bn tin bo hiu SIP v chuyn tip ti I CSCFSIP

MiS-CSCF - BGCFTruyn ti thng tin qua li gia S-CSCF v BGCFSIP

MjBGCF -> MGCF

Truyn ti thng tin qua li gia BGCF v MGCF trong cng mt mng li IMSSIP

MkBGCF -> BGCFTruyn ti thng tin qua li gia BGCF v MGCF thuc cc mng IMS khc nhau.SIP

MmI-CSCF, S-CSCF, mng IP ngoiTruyn ti thng tin qua li gia cc mng IP v IMSSIP

MnMGCF, IM-MGWiu khin ti nguyn trong mt phng ngi dngH.248

MpMRFC, MRFPTruyn ti thng tin qua li gia MRFP v MRFCH.248

MrS-CSCF, MRFCTruyn ti thng tin qua li gia S-CSCF v MRFCSIP

MwP-CSCF, I-CSCF, S-CSCFTruyn ti tt c cc bn tin bo hiu gia cc CSCFSIP

RfCc CSCF, BGCF, MGCF, AS, MRFC,CDFCc thc th IMS s dng trong tnh cc offline n OCS.Diameter

RoAS, MRCF, OCS, S-CSCFAS, MRCF, S-CSCF s dng cho tnh cc trc tuyn ti OCSDiameter

RxP-CSCF, AS, CRFThng tin dch v lin quan tnh cc ng c chuyn gia CRF v cc thc th IMSDiameter

ShSIP AS, OSA SCS, HSSTruyn ti thng tin gia SIP AS/OSA SCS v HSS

Diameter

SiIM-SSF, HSSTruyn ti tt c cc bn tin gia IM-SSF v HSSMAP

UtUE, AS (SIP AS, OSA SCS, IM-SSF)Cho php UE qun l cc thng tin lin qua n dch v ca mnhHTTP

Bng 2.1: Cc im tham chiu lin kt cc chc nng trong mng li IMS.

2.4. Cc giao thc chnh c s dng trong IMS.

Kin trc IMS do 3GPP pht trin da trn cc giao thc IP c chun ha bi IETF. Giao thc IP bao gm cc giao thc v iu khin phin, cc giao thc v chng thc, cp quyn v tnh ton (AAA) v mt s cc giao thc khc.

Phn ny m t cc giao thc chnh c s dng gia cc im kt ni trong IMS. S khng nu r chi tit cc giao thc, m ch gii thiu tng quan cc giao thc.

2.4.1. Giao thc khi to phin (SIP). SIP (Session Initiation Protocol) c chn l giao thc khi to phin cho IMS, SIP c IETF chun ha trong RFC 3261 (Request for Command).

SIP tun theo m hnh khch - ch (client-server). c thit k da trn cc nguyn l c bn t hai giao thc HTTP, SMTP, nn SIP tha k hu ht cc c tnh quan trng ca hai giao thc ny. iu ny to ra sc mnh cho n bi HTTP v SMTP l cc giao thc rt thnh cng trong mng Internet. Khng ging nh H323 v BICC, SIP khng phn bit giao din ngi dng ti mng (User-to-Network) vi giao din mng vi mng (Network-to-Network). Trong m hnh SIP ch c mt giao thc duy nht hot ng thng sut. Ngoi ra SIP l mt giao thc di dng vn bn do n d dng m rng, g ri v pht trin cc dch v.

SIP l mt giao thc thuc lp ng dng c s dng cho vic thit lp, iu chnh v kt cui cc phin a phng tin trong mt mng IP. N l mt phn ca kin trc a phng tin m nhng giao thc vn ang c chun ho bi IETF. Cc ng dng ca n bao gm: voice, video, gaming, messagging, iu khin cuc gi v presence. Cc thnh phn trong SIP c th phn loi thnh cc User Agent (UA) v cc thnh phn trung gian (l cc servers). Mt UA l mt im cui ca mt cuc gi, n gi v nhn cc yu cu v p ng SIP, n l im kt thc ca cc dng ang phng tin nn thng n cn c gi l UE. UA bao gm 2 phn:- User Agent Client (UAC): cn c gi l Calling Agent User l mt ng dng c chc nng khi to yu cu SIP.- User Agent Server (UAS): cn gi l Called Agent User tip nhn, gi tr li, t chi yu cu v gi p ng v cho user gi yu cu.

Hnh 2.9: Cc thnh phn SIP.Cc thnh phn trung gian l cc thc th chuyn cc bn tin SIP n ch, chng c s dng nh tuyn v gi li cc yu cu. Nhng server ny bao gm: Proxy server: nhn v chuyn tip cc yu cu. N c th bin dch v vit li bn tin m khng nh hng n trng thi yu cu. Mt proxy server c th gi mt yu cu n mt s a im ti cng mt thi im c im ny gi l

forking proxy. C 3 loi proxy server:- dialog-statefull proxy: mt proxy l dialog-statefull nu n duy tr trng thi cuc gi t yu cu khi to (INVITE) n yu cu kt thc (BYE)- transaction-statefull proxy: l mt proxy nu n c c cu chuyn dch trng thi client v server trong qu trnh yu cu- stateless proxy: l mt proxy m chuyn tip mi yu cu v p ng m n nhn c. Redirect server: nh x a ch yu cu thnh i ch mi v tr li a ch ny v client. N khng khi to mt yu cu SIP v khng chuyn cc yu cu ti cc server khc, khng ging nh proxy server. Location server: l server gi v tr ca user. Registrar server: l server chp nhn cc yu cu REGISTER. N c s dng tip nhn cc ng k t UA cp nht thng tin v v tr ca chng.Ngoi ra, cn c thm 2 server c s dng cung cp dch v cho cc SIP user: Application server v Back-to-back-user-agent (B2BUA)2.4.2. Giao thc h tr chng thc, cp quyn, tnh cc Diameter(AAA). Diameter da trn RFC 3588 c chn l giao thc AAA trong mng IMS. Diameter l mt giao thc cho vic nhn thc, cp php, v tnh cc (Authentication,Authorization and Accounting) (AAA), c xy dng da trn giao thc RADIUS - ban u c s dng cung cp AAA, cho mi trng dial-up v truy nhp server u cui. V khi cc mng mi ra i, AAA Working Group a ra thm mt s yu cu cho AAA c th p dng v mng truy nhp ca nhu nhm khc nhau: - IP Routing for Wireless/Mobile Hosts WG (MPBILEIP) [RFC2977]- Network Access Server Requirements WG (NASREG) [RFC3169]- Roaming Operations WG (ROAMOPS) [RFC2477]- Telecommunications Industry Association (TIA)Giao thc Diameter thc ra c chia lm 2 phn: giao thc c s Diameter v cc ng dng Diameter. Giao thc c s cung cp cc yu cu ti thiu ca mt giao thc AAA, pht cc n v d liu Diameter, kh nng thng tho, x l li, ng dng Diameter da trn giao thc c s, nh ngha cc chc nng ng dng ring. Hin nay, mt s ng dng Diameter c a ra: Mobile IP, NASREQ, Extexsible Authentication Protocol (EAP) , Diameter credit control v Diameter SIP application.

TnChc nng

Giao thc c bn DIAMETERQun l phin, peer to peer, tnh cc v i din

Xc nh cc h tr cho TLS v phin IP

ng dng server truy nhp dch v AAA cho NAS

mng DIAMETERDch v AAA cho NAS

H tr cho PPP CHAP v kt ni mng

RADIUS/DIAMETER

ng dng IPv4 Mobile DiameterDch v AAA cho Mobile IPv4

L lch truyn ti AAAS dung TCP v SCTP cho AAA

ng dng EAP DiameterS dng DIAMETER cho cung cp giao thc nhn thc m rng (EAP) ti nhng ngi s dng PPP.

ng dng quy tc bn tin gc DIAMETERTruyn ti cc xc nhn X 509 gia cc im ca DIAMETER

Bng 2.2:Ti liu v nhn thc trao quyn v thanh tonGiao thc c s Diameter s dng c hai giao thc truyn ti TCP v SCTP. Tuy nhin SCTP c chn nhiu hn, n th chia nhiu lung c lp vo trong mt kt ni SCTP, thay v gi tt c cc lung ring nh trong TCP.

2.4.3 Mt vi v d v hot ng ca SIP v DIAMETER trong IMSSIP c la chn lm bo hiu trong mng li IMS v giao thc Diameter c s dng cho nhn thc trao quyn v thanh ton m t giao thc SIP v Diameter da trn cc th tc bo hiu trong li IMS trong hai v d di y. Trong v d th nht ch ra mt th tc khi to ng k, cho rng ngi dng chuyn mng sang mng khch. Th tc ny bt u vi yu cu ng k SIP ngi dng c gi t P-CSCF ca mng khch. V bng thng v tuyn hn ch, bn tin c nn trc khi gi i bi ngi dng v c gii nn P-CSCF. Nu c nhiu S-CSCF tn ti trong mng nh ca ngi s dng, mt I-CSCF cn thit trin khai la chn mt S-CSCF phc v phin ca ngi dng . Trong trng hp ny P-CSCF quyt nh mt a ch ca I-CSCF mng nh ca ngi dng bng cch s dng tn min mng nh ngi dng v chuyn bn tin REGISTER ti I-CSCF. Sau khi I-CSCF gi p ng nhn thc ngi dng (UAR) ti HSS, HSS tr li a ch ca kh thi ca S-CSCF. I-CSCF la chn mt S-CSCF v chuyn bn tin ng k.

Hnh 2.10: Lung bn tin bo hiu ng k

Trong lc xc nhn ng k, S-CSCF ly li vector nhn dng t HSS qua giao thc Diameter p ng nhn thc a phng tin MAR v tr li ngi dng bn tin SIP 401 khng c nhn thc m c th mang s liu hi p nhn thc. Sau khi tnh ton p ng nhn thc, ngi dng gi n S-CSCF mt bn tin ng k khc c mang bi p ng hi p. S-CSCF xc nhn li p ng v nu p ng ng, n ti xung thuc tnh thu bao t HSS qua mt p ng yu cu ch nh my ch SAR Diameter. S-CSCF c th lin lc vi mt Server ng dng iu khin dch v nh trong thuc tnh ca thu bao. trc khi tr li bn tin 200 OK ti ngi s dng.

Hnh 2.11: Lung bn tin bo hiu thit lp phin

Trong v d th hai ch ra lung bo hiu mt thit lp phin gia hai ngi dng IMS, cho rng c nhiu S-CSCF c trin khai. Mt th tc thit lp phin l mt qu trnh ca vic tm ra cc phn t mng v cc thnh phn bo hiu. Khi nh tuyn bn tin ng k, I-CSCF ca ngi b gi truy vn HSS ca ngi b gi tm a ch ca mt S-CSCF c ch nh qua bn tin Diameter yu cu thng tin v tr LIR. HSS p ng li bng bn tin Diameter tr li thng tin v tr LIA. Trc khi gi bn tin ng k, S-CSCF ca ch gi v ngi b gi c th lin lc vi Server ng dng iu khin dch v v tnh cc cho dch v ti xung trong khi ng k ngi dng. K thut phn gii a ch v nh tuyn bn tin SIP chun c s dng nh tuyn bn tin ng k t ch gi ti UE b gi trn tt cc cc con ng. Cc con ng nhn c l UE ch gi, P-CSCF mng khch ch gi, S-CSCF mng khch ch gi, I-CSCF b gi, S-CSCF b gi, P-CSCF mng khch b gi v UE b gi. Bn tin tr li t UE b gi i theo ng ngc li. Th tc tho thun mt phin cung cp tr li c bn cng c kim sot trong thi im ny. iu ny c hon thnh qua giao thc m t phin SDP c mang bi thn ca bn tin SIP (v d bn tin ng k vi mt mi gi v bn tin 200 OK vi mt tr li). 2.4.4. Cc giao thc khc.

Bn cnh SIP v Diameter, IMS cn s dng nhiu giao thc khc nh:

Giao thc dch v chnh sch m thng thng COPS (Common Open Policy Service) c dng truyn ti chnh sch gia cc im quyt nh dch v PDPs (Policy Decision Points) v cc im thc hin chnh sch ( Policy Enforcement Points).

H.248 (ITU-T khuyn ngh H.248) c s dng bi cc nt bo hiu iu khin cc nt trong mt phng media.

RTP (Real-Time Transport Protocol, RFC 3550) v RCTP (RTP Control Protocol, RFC 3550) dng truyn ti media nh video v audio

2.5. Kt lun chng 2

Chng 2 gii thiu khi qut nht v kin trc ca IMS, cho ta thy kin trc ca IMS l s t hp ca cc chc nng c gn kt vi nhau thng qua cc giao tip c chun ha. Ngoi ra chng ny cng ch ra cc chc nng v cc giao thc trong IMS.

Chng 3. Cc yu cu v ng dng dch v IMS3.1. Gii thiu

IMS l kin trc mng c 3GPP pht minh chun ha. Khi u IMS a ra vi mc ch ng dng cho kin trc mng s dng ton IP cho cc mng di ng theo kin trc ca 3GPP. Vi nhng u im v kin trc phn lp, tnh kt ni IP, kh nng iu khin phin cho cc ng dng ngang hng, IMS khng nh hng i ng cho vic pht trin mng di ng da trn nn IP.

3GPP2 v ETSI nhn thy u im v k tha, p dng vo kin trc mng ca mnh. Trong TISPAN a IMS lm mt trong phn h trong kin trc NGN ca mnh, hin c chun ha. Trong kin trc mng ca TISPAN, hai mng c nh v di ng c hi t y v r nt. Nh vy, IMS c ng dng trong cc kin trc mng ca cc t chc chun ha, thc y qu trnh hi t gia mng di ng v c nh.3.2. Yu cu trong h thng IMSC th thy rng mc tiu xy dng mng IMS nhm: T hp cc xu hng cng ngh mi nht; Hin thc Internet di ng; To c s h tng chung trin khai nhiu dch v a phng tin; To mt c ch tng li nhun nh vic b sung dch v trn mng di ng. t c mc tiu 3GPP a ra 6 yu cu c bn cho mng li IMS nh sau: H tr thit lp cc phin a phng tin IP; H tr c ch tho thun cht lng dch v QoS; H tr tnh nng lin mng vi cc mng Internet v mng chuyn mch knh; H tr chuyn vng (roaming); H tr iu khin dch v phn phi n khch hng; H tr nhanh chng khi to dch v m khng yu cu phi hp chun.

3.2.1. Thit lp cc phin a phng tin IP

IMS c th phn pht nhiu dch v trong c c dch v truyn thng audio v video. Yu cu l cn thit IMS h tr cung cp cc phin a phng tin trn cc mng chuyn mch gi. Cc truyn thng a phng tin trc y cng c 3GPP chun ha trong cc phin bn trc, tuy nhin n c thin hng cho mng chuyn mch knh ch khng phi dnh cho mng chuyn mch gi.

3.2.2. Qun l m bo cht lng dch v - QoSMt yu cu c bit quan trng ca IMS l phi c kh nng cho php u cui ngi dng (UE) tha thun mt mc QoS xc nh.QoS ca mt phin giao dch c xc nh bi tp cc h s, nh l tc bt, c gi, kiu d liu, bng thng ln nht m h thng c th phn b ti ngi dng da trn thng tin khch hng

hay nng lc hin ti ca mng. Sau khi tha thun cc thng s ti mc ng dng nht nh, UE thc hin chim dng ti nguyn tng ng trong mi trng mng. Khi kt ni end-to-end QoS c thit lp, UE m ha v ng gi cc kiu d liu vi giao thc tng ng v gi chng ti mng truyn ti v truy nhp thng qua giao thc lp truyn ti da trn nn IP.

IMS cng cho php cc nh khai thc iu khin mc QoS n ngi dng chnh v l cc nh khai thc c th phn loi khch hng ca mnh thnh cc nhm khc nhau.

3.2.3. H tr lin mngYu cu lin kt vi Internet l bt buc trong xy dng cu trc khung lm vic ca IMS, vi vic lin kt vi Internet, s lng tim nng ngun v ch cho cc phin a phng tin s tng t ngt.

IMS cng c yu cu lin kt ti cc mng chuyn mch knh nh l PSTN hoc cc mng di ng t bo. Cc u cui IMS h tr audio/video s c ra mt u tin trn th trng, cc u cui ny c th kt ni ti c cc mng chuyn mch knh v mng chuyn mch gi. Khi ngi dng mun thc hin mt cuc gi ti mt thu bao PSTN hoc thu bao di ng, cc u cui IMS la chn trong min chuyn mch knh.

Chnh v vy, vn lin mng vi mt mng chuyn mch knh khng c yu cu nghim ngt lm mc d phn ln cc cu cui IMS cng s h tr min chuyn mch knh. Vn lin kt vi cc mng chuyn mch knh c th xem nh l mt yu cu v lu v di. Thng thng vn lin mng vi mng chuyn mch knh ch i hi khi m cc u cui IMS ch thch ng vi mng chuyn mch gi.

3.2.4. Chuyn vngChuyn vng l nhu cu chung t cc mng di ng t ong th h 2 khi m thu bao phi chuyn vng sang cc mng khc (v d nh khi thu bao i du lch ra nc ngoi). y l yu cu thit yu v ng nhin h thng IMS c tha hng yu cu ny, cho php khch hng chuyn vng khi di chuyn n cc quc gia khc tt nhin iu ny ch c thc hin khi c s tha thun gia cc nh khai thc ti mng ch v khch.3.2.5. iu khin dch v Thng thng cc nh khai thc mun p t cc chnh sch phn phi dch v ti khch hng. V c bn c 2 loi chnh sch nh sau:

-Chnh sch chung p dng cho tt ckhch hng.

-Chnh sch ring cho tng khc hng c bit.

Chnh sch u tin bao gm mt tp nhng hn ch m p dng ti tt c ngi dng trong mng. V d nh khai thc mun hn ch bng thng tn hiu thoi thng qua s dng m ha thoi c bng thng thp nh AMR (Quy nh trong chun 3GPP TS 26.071) ch khng dng chun m ha thoi bng rng G.711 (Chun m ha ca ITU-T 64 Kbps) trong mng ca h.

Chnh sch th 2 bao gm mt tp cc chnh sch m ch b buc trong tng ngi dng nht nh. V d nh mt khch hng no m trong bng ng k s dng dch v IMS nhng khng s dng dch v video. Trong trng hp h c gng khi to mt phin a phng tin m c dch v video th nh khai thc thc hin ngn cn qu trnh thit lp phin mc d phn ln cc u cui IMS u h tr tnh nng cung cp dch v video. Chnh sch ny l tun theo c s bn ng k s dng dch v ca ngi dng vi nh cung cp.

3.2.6. To dch v nhanh chng v a truy nhp

Yu cu ny c tc ng ln trong vic thit k cu trc ca h thng IMS, n ch ra rng cc dch v IMS khng cn thit phi c chun ha. iu ny nh du mt mc quan trng trong vic thit k mng di ng t ong bi v trc y mi mt dch v n l hoc l cn chun ha hoc c ng k c quyn. Ngay c khi dch v c chun ha th khng c g c th m bo rng dch v vn tip tc duy tr khi m ngi dng chuyn vng sang mng khc. Mt v d in hnh mi ngi thng thy trong mng GSM l cc cuc gi c th b chuyn ti hp th thoi khi m ngi dng di chuyn ti mt quc gia khc.

Mc ch ca IMS gim thi gian a ra mt dch v mi. Trc y vic

chun ha dch v v thc hin kim tra nng lc dch v l nguyn nhn gy tr ng k. Vi IMS gim thi gian ny, ngi ta chun ha cc nng lc dch v thay cho vic chun ha dch v nh trc y. IMS cng ch l mt mng IP v n ging vi bt k mng IP no khc. N lm vic lp thp v c truy nhp c lp. Bt k mng truy nhp no cng c th kt ni ti IMS. V d nh l kt ni t mng truy nhp v tuyn ni ht WLAN, t ADSL, HFC hoc truy nhp t modem.

3.3. Cc loi dch v ng dng ca IMS

3.3.1. Dch v video Conferencing

H thng Video Conferencing ngy nay l mt dch v m rng trn nn h tng IP. Mc tiu ca vic trin khai h thng ny l nhm trin khai dch v thng dng v ph bin hin nay cho php cc cng ty tr s chnh v cc cng ty thnh vin ti ch hoc xa c th trao i vi nhau khng ch bng li ni v m bng hnh nh v khng ch vi mt vi cng ty m c th tham gia nhiu cng ty cng lc, t hnh thnh mt mng thng nht trn ton h thng mng.

Dch v "Video conferencing (hi ngh truyn hnh) qu thc khng cn l khi nim xa l g i vi tt c chng ta. V trong thc t th nhu cu s dng hi ngh truyn hnh l rt ln bi v rt nhiu li ch m n mang li. Hi ngh truyn hnh c th ng dng vo rt nhiu lnh vc quan trng gp phn lm pht trin t nc nh : gio dc, y t, chnh ph, doanh nghip,....

Cc chc nng c bn ca dch v Hi ngh truyn hnh:

+ Ghi hnh cuc hp v lu xung my tnh ci phn mm hi ngh truyn hnh.

+ Chia s mn hnh my tnh v chia s cc phn mm trn my tnh.

+ Trao i tp tin trc tip.

+ Tng tc trc tuyn trong cuc hp.

+ H tr nhiu camera/webcam kt ni vo my tnh ci phn mm hi ngh truyn hnh.

+ Hn v ln k hoch cuc hp.

+ Mi nhiu ngi tham gia vo cuc hp.

+ Bng trao i thng tin.

+ Trnh by ni dung cc tp tin: powerpoint, excel, pdf, doc, hnh nh,...

+ C nhiu giao din hin th mn hnh cuc hp.

3.3.2. Dch v Messaging (tin nhn)

H thng cung cp dch v tin nhn l h thng cung cp ni dung, thng tin da trn cng ngh truyn ti tin nhn. Do c th ca cng ngh v thit b u cui, mi tin nhn c chiu di ti a 160k t (hoc 132 byte nu l d liu binary).

Tin nhn c s dng ph bin do c tnh c th s dng bt c u, bt c khi no. Vit Nam hin nay, tc tng trng thu bao rt ln (~30 triu thu bao online, tnh n thng 10/2010), mt phn cng nh s bng n cc dch v gia tng da trn cng ngh SMS. Mt s dch v cng dngnhiu, nh:

+ Cung cp thng tin vn: x s, bng , thi tit, t gi,..

+ Tin nhn cnh bo:dng trong cc h thng cn n nh cao, hot ng 24/24,..

+ ng k nhn tin: thay i s d ti khon, kt qu khp lnh chng khon,..

+ Thanh ton in t: SMS banking, Mobile banking, Mobile wallet (v in t, hay m-wallet).

+Mua bn chng khon, t hng online,..

3.3.3. Dch v Presence

S hin din (presence) v thng ip tc thi v ang thay i vin cnh ca th gii truyn thng. Presence s l tri tim ca mi lin lc v l mt chc nng mi khng th thiu cho chic in thoi. Presence cng s l mt c hi kinh doanh cho cc nh iu hnh v cung cp dch v.

Dch v Presence cung cp cc thng tin cho ngi s dng bao gm trng thi ca cc ngi khc trn mng. Trang thi ca mt ngi dng cung cp thng tin cho nhng ngi khc quyt nh c nn lin h th vi ngi ny hay khng v c nn dng tnh nng chat hay gi in hoc email lin lc.

Dch v Presence khuyn khch kh nng giao tip ca mi ngi v c im ca tnh ny l gip ngi dng xc nh r v trng thi ca i phng nu nh h ang trong cuc hp hay bn ngoi vn phng, trong trng hp thc hin mt phin chat l khng cn thit lc . Cc trng thi ca i phng khng ch xut hin di dng icon n gin trong Lync 2010 m cn trong cc ng dng truyn thng khc nh Microsoft Outlook v cc phin bn Lync khc, v xut hin ngay c trong Sharepoint, Microsoft Word hoc portal ca my ch hoc dch v v c Microsoft Excel. Dch v Presence i din cho trng thi sn sng ca i tng xc nhn xem c nn thc hin mt lin lc

Presence c th ng gp cho nhng vic kinh doanh, cc dch v Presence v Presence-enhanced u s c s dng. Cc nh iu hnh v cung cp dch v ng vai tr chnh trong vic duy tr cc dch v ny. Dch v Presence di ng l mt phn trong danh mc dch v ca nh iu hnh. Thu bao di ng ngy nay t n con s hng t trn th gii, l mt kho li nhun cho cc dch v mi.

Presence to ra nhiu dch v mi nh instant message. Presence cng lm gim ng k cc cuc gi khng thnh cng hay b t chi, iu ny c c do bit c trng thi ca user hin thi (busy hay available, online hay offline).

3.3.4. Dch v Push to talk over cellular

Push to talk over cellular (PoC) cung cp dch v truyn thoi im-im v im- a im. tng l user chn mt vi c nhn hoc mt nhm ngi m user mun lin lc, v sau nhn nt bt u ni chuyn.

Hnh 3.1. Push to talk over Cellular

Phin kt ni trong thi gian thc, l mt chiu, khi mt ngi ni th ngi khc ch vic nghe. Vic chuyn sang ni c yu cu bng cch nhn nt ni v c cng nhn trn c s first come first served yu cu no n trc s c p ng trc. Kt ni khng cn cc bn nhn chp nhn v c nghe thng qua loa ngoi ca in thoi. User cng c th chn nhn mt phin m thoi sau khi chp nhn mt li mi. Nu cn thit c s ring t, user c th nghe bng tai nghe. Dch v ny da trn multi-unicasting. Mi client gi cc gi d liu n mt PoC server v trong trng hp lin lc theo nhm, server s gi cc gi ny n tt c cc my thu (hnh 3.1). Khng mt qu trnh multicast no c thc hin trong mng truy nhp cng nh mng li, s qun l tnh di ng c thc hin bi mng v tuyn. iu ny gii thch tnh trong sut ca dch v PoC i vi mng t bo v mng c nh.

Dch v push to talk s dng mng li NGN c th phc v nhiu loi chc nng truyn ti truy nhp.

3.3.5. Dch v in thoi di ng v truyn hnh * Dch v in thoi di ngTrong vi nm ti, cc mng in thoi di ng s truyn d liu vi tc c vi Mbps (megabits per second) v s cng tn ti vi WiMax, Wi-Fi, v cc chun DVB-H hoc MediaFLO cho TV. Cng ngh mng IMS (IP Multimedia Subsystem) s cho php h lm vic vi nhau. Truy cp Internet thng sut: Ngoi cc cng ngh GSM, CDMA, Wi-Fi, WiMax, cng ngh IMS s cho php chuyn thng sut bt k loi gi tin no (d liu thoi, video, nhc, HTML,). Vi IMS, c th bt u cuc gi bng TD v kt thc l VoIP, xem TV c ph trn TD hoc mn hnh ln (nh cng ngh th thng minh), Nhng nhng li ch ny ch c c khi cng ngh IMS c trin khai rng ri trong vi nm ti.

* Dch v truyn hnh

Mt gii php truyn hnh da trn IMS s em li cho ngi dng c hi thng thc cc dch v TV i mi nhng dch v p ng v vt qu cc k vng m ngi dng ngy nay mong i TV tng lai.

Do cc dch v IMS c phn pht ti cc thu bao ring bit ch khng phi ti cc thit b ring bit, cho nn TV da trn IMS c th c t hng ring v c nh du ring cho cc a thch c nhn. TV da trn IMS cng cho php tnh tng tc v tnh ha trn cc dch v truyn thng v gii tr. Vic tiu chun ho v cc giao din m m trn xy dng nn TV da trn IMS s h tr s xut hin mt th trng i chng, n lt mnh, th trng ny em li s cnh tranh cng ngy cng gia tng nh gi c cng ngy cng h xung v cht lng dch v tng ln.

Mt nn tng khch hng gia tng vi cc dch v c tiu chun ho v tnh tng tc gia cc nh khai thc cng s em li cho khch hng kh nng truyn thng v chia s cc ni dung nh s dng nhiu dch v truyn thng da trn IMS khc nhau Tm li, cc khch hng TV da trn IMS s c c:

- Truyn thng kt hp vi tri nghim TV, ngha l:

+ Xem ni dung v truyn thng cng mt lc

+ X l cc cuc gi n v cc tin nhn qua my thu hnh

+ Duy tr mt cun s a ch tin li c th hin th.

- Tnh tng tc, c ngha l: mt tnh nng thm d v bu c, chng hn nh b phiu cho cu th hay nht khi xem mt trn bng trn TV.

- em TV theo h, cho php:

+ Tnh di ng ca phin vi vic chuyn mt phin TV sang mt thit b khc (chuyn ch)

+ Chn khi no, u, v trn thit b no (my thu hnh, chic my tnh hay ci TD) h mun thng thc ni dung

- iu khin t xa cc dch v TV ca h qua cc thit b di ng c nhn (cc my TD, cc PDA v.v):

+ thit lp cc b ghi nh chng trnh v cc ghi chp cng vic hng ngy

+ quyt nh s qun l t xa ca cha m

+ kim tra ai ang xem ni dung g. 3.6. Kt lun chng 3

chng 3 ny ta c th thy IMS cung cp tt c cc dch v s dng cng ngh chuyn mch gi, nhn chung n hiu qu hn cng ngh chuyn mch knh. Tuy nhin sc mnh thc s ca IMS khi so snh vi cc trng hp nu trn l IMS to ra mi trng m dch v no cng c th truy nhp bt k mt kha cnh no ca phin. iu ny cho php cc nh cung cp dch v to ra nhiu dch v hn trong mt mi trng m tt c cc dch v u c lp vi nhau.KT LUN

IMS ang l tiu im tho lun ca cc t chc chun ha vin thng v cc cng ty in t tin hc, vi phm vi ti khng th trnh by ht cc kha cnh ca IMS, ti ch a ra ci nhn tng quan nht v IMS, qua thy c vai tr v chc nng ca n trong kin trc mng NGN. Vic xy dng mng li IMS trong kin trc NGN l mt nhu cu tt yu, ph hp vi xu th pht trin ca ngnh vin thng, m ra cnh ca cho s hi t di ng c nh vi kh nng a truy nhp v cung cp nhiu loi hnh dch v khc nhau trn mt nn tng mng duy nht, p ng nhu cu ngy cng cao ca ngi s dng. Trong tin trnh pht trin v chun ha IMS, cn rt nhiu vn cn c tm hiu. Hng pht trin ca ti c th i su vo tm hiu cc th tc trn cc giao din IMS n c th h tr cc ng dng a phng tin IP, nghin cu v a ra gii php cho vn bo mt trong IMS

Do qu trnh thc hin chuyn ch da trn l thuyt v tm hiu ti liu, cha c tip xc thc t v c cc m hnh thc tin tip cn v cn hn ch v mt thi gian nn nhiu vn cha th trnh by r v chc chn khng trnh khi nhng thiu st. Rt mong c s thng cm v ng gp kin ca thy v cc bn chuyn c hon chnh hn. Chn thnh cm n!

H Ni, thng 10 nm 2011

Nhm thc hin chuyn .

TI LIU THAM KHO[1]. Nguyn Vit Anh, (2004), Nghin cu, xut nh hng pht trin cc dch v mi trn mng NGN ca TCT n nm 2010, Vin KHKT Bu in.

[2]. o Anh H, (2008), n: Nghin cu v pht trin chc nng HSS v SLF cho kin trc IMS.

[3]. L Th Hiu, (2010), n: Phn h IMS trong kin trc NGN

[4]. Gonzalo Camarillo, Miguel A . Garcia- Martin, (2006), The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds, Second Edition, John Wiley & Sons.

[5]. Technical Specification Group Services and System Aspects (2006),IP Multimedia Subsystem (IMS), Stage 2, TS 23.228, 3rd Generation Partnership Project[6]. Alexander Harrowell, Staff Writer (October 2006),A Pointless Multimedia Subsystem?, Mobile Communications International[7]. Miikka Poikselk, Georg Mayer, Hisham Khartabil and Aki Niemi,The IMS: IP Multimedia Concepts and Services,Second Edition2006 John Wiley & Sons, Ltd.

[8].Antonio Cuevas,IMS tutorial,The Second International Conference on Digital Telecommunications ICDT 2007.

[9]. Travis Russell,IMS: Session Control and Other Network Operations,2008 by The McGraw-Hill Companies.

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