Tong Quan Ve Mang Truy Nhap Bang Rong Wimax 0017

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Tong Quan Ve Mang Truy Nhap Bang Rong Wimax 0017

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  • TRNG . KHOA.

    -----[\[\-----

    Tng Quan V Mng Truy Nhp Bng Rng-WiMAX

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    1

    Chng 1

    Tng Quan V Mng Truy Nhp Bng Rng-WiMAX

    1.1 Mng Truy Nhp bng rng

    nh ngha mng truy nhp:Theo cc khuyn ngh ca ITU-T(Lin minh vin thng quc t pht trin cc tiu chun quc t),mng truy nhp l mt chui cc thc th truyn dn gia SNI (Service Node Interface Giao din nt dch v) v UNI (User Network Interface Giao din ngi s dng - mng). Mng truy nhp chu trch nhim truyn ti cc dch v vin thng. Giao din iu khin v qun l mng l Q.

    Hnh 1 :Kt ni mng truy nhp vi cc thc th mng khc

    Thit b u cui ca khch hng c kt ni vi mng truy nhp qua UNI, cn mng truy nhp kt ni vi nt dch v (SN Service Node) thng qua SNI. V nguyn tc khng c gii hn no v loi v dung lng ca UNI hay SNI. Mng truy nhp v nt dch v u c kt ni vi h thng qun l mng TMN (telecom management network) qua giao din Q.

    S thay i ca c cu dch v l yu t then cht nh hng n s pht trin ca mng truy nhp. Khch hng yu cu khng ch l cc dch v thoi/ fax truyn thng, m c cc dch v s tch hp, truyn hnh k thut s phn gii cao,..vv. Mng truy nhp truyn thng r rng cha sn sng p ng cc nhu cu dch v ny..

    Trong nhng nm gn y mng truy nhp v tuyn bng rng tc cao khng ngng c nghin cu v pht trin ,cung cp cc dch v Multimedia nh:

    Mng truy nhp

    Thu bao

    Cc thc th mng (PSTN ,ISDN..)

    Q

    SNI- Giao din nt dch v

    UNI- Giao din ngi

    s dng mng

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    2

    truy cp Internet, VoIP, in thoi truyn hnh (Video Telephony), hi ngh truyn hnh (Video conferencing), truyn hnh qung b (Broadcast TV), xem phim theo yu cu (Video on Demand), tr chi trn mng (Game online) .vv

    C th ni mng bng rng l xu hng pht trin tt yu.Sau y chng ta s cp ti mt s cng ngh truy cp bng rng in hnh l :xDSL, Modem cp ,iPSTAR v mt s k thut truy nhp v tuyn nh WiFi v WiMAX.

    1.1.1 Mng xDSL [9]

    Truy nhp xDSL ( x Digital Subscriber Line ):ng dy thu bao s (xDSL ) l phng thc truyn thng tin s tc cao qua ng in thoi truyn thng v s l nn tng cho vic phn b dch v bng rng ny n cc thu bao. S d iu ny thc hin c l nh ng dng cc k thut truyn s phc tp, l s b tr cc suy gim truyn dn trn ng dy in thoi v cc b x l s c nng lc rt ln.Cng ngh ny tn dng c s h tng ng dy thu bao cp ng c sn

    Khi nng lc x l ca b x l tn hiu s tng ln, th tc ca xDSL cng tng ln. Cng ngh DSL bt u t 144 kbit/s, pht trin ti 1,5 n 2 Mbit/s HDSL, 7 Mbit/s vi ADSL, v by gi vi VDSL l 52 Mbit/s

    ng dy thu bao s bt i xng ADSL (Asymmetric DSL)

    - S dng mt i dy cp xon - Tc lung xung ln (1,5Mbps khong cch 6 km n 8Mbps vi

    khong cch 3 km).Tc hng ln t 16kbps n 640kbps

    ng dy thu bao s tc thch nghi RADSL (Rate Adaptive DSL)

    - S dng mt i dy cp xon - Tc lung xung ln (1 Mbps n 12 Mbps vi).tc hng ln t 128

    kbps n 1Mbps tc truyn i xng trong khong t 1 n 2 Mbps - Cc modem RADSL c kh nng nh gi cht lng ng y v t ng

    iu chnh mc iu ch hoc s dng cc bc sng (ty thuc vo phng php m ha ng y)

    ng dy thu bao s tc rt cao VDSL(very high bit rate DSL)

    Tc lung xung ln (30Mbps n 50 Mbps vi c ly ngn thng nh hn 300m . Tc truyn i xng trong khong t 2 n 4 Mbps v khong cch xa hn.

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    3

    Cc cng ngh xDSL i xng nh HDSL, SDSL, HDSL2

    - High bit rate DSL (HDSL)l mt trong nhng cng ngh u tin c khai thc . Tc truyn i xng 1.54 Mbps trn 2 i dy cp xon hoc 2Mbps trn 3 i cp xon.,HDSLversion 2 ging HDSL nhng ch s dng 1 i cp xon.Khong cch truyn l 4 Km

    - SDSL (Symmetric DSL) s dng 1 i cp xon, vi tc h tr ln ti 2Mbps cho frame-relay hay truyn hnh hi ngh.,khong cch truyn khong 3 Km.

    Tn Tc d

    liu C

    ly(km) c im ng dng

    HDSL

    1.544 (kbps) 2.048 (kbps)

    3.6 Khng s dng truyn dn c c d liu v tn hiu thoi

    Mng cung cp T1/E1 , truy sut WAN, LAN

    SDSL 1.5447(kbps) 2.048(kbps)

    3.6 Ghp c tn hiu thoi v d liu trn cng mt i dy Tc ti d liu cng vi tn hiu thoi khng cao Thch hp cho cc doanh nghip va v ln

    Ni ht, thay th trung k T1/E1c dng b lp,Kt ni cc PBX vi nhau, Kt ni mng LAN

    ADSL 1.5-9 Mbps 16-640 (kbps)

    5 D trin khai do s dng c s mng in thoi sn c.Chi ph hp l. S dng ng thi fax, voice m khng cn ngt mng. Hot ng Fulltime. Ph hp vi cc doanh nghip va v ln

    Truy nhp internet,/intranet video theo yu cu,VPN,VoIP ,truy nhp LAN t xa

    VDSL 13-52 Mbps 1.5-2.3 Mbps

    1.4 S dng ng thi fax, voice tch hp Splitter Cha c h tr bi cc ISP ch dng cho mng LAN m rng

    Truy nhp Mutimedia intern et.cc trng trnh broadcard TV

    Bng 1 :Cc cng ngh xDSL

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    4

    Nhng u im v hn ch ca cng ngh xDSL:

    - Gim gi thnh v tc trn khai nhanh nhng khu vc m mng cp ng c sn

    - C th trin khai trn din rng vi nhiu loi m hnh khc nhau - sn sng ca mng cp ng mt s ni nh vng nng thn ,vng su

    vng xa , hoc hi o hu nh khng c ,v nu c th cht lng ca mng cp ng cha t yu cu nn m bo tc truy nhp cao DSL l rt kh.

    - Vng ph nh, bn knh phc v t l nghch vi tc truy nhp nn mc u t s cao vng phn tn rng.

    - Khng c tnh di ng.

    1.1.2 Modem cp [5]

    Modem cp l thit b c dng chuyn d liu trn cc ng truyn cho truyn hnh cp. Loi ng truyn ny, l cp ng trc, mang li bng thng ln hn nhiu so vi ng in thoi thng thng. Ni modem ny vi cp truyn v vi PC s mang li kh nng truy cp Internet tc cao.Trn l thuyt, tc ti xung ca cc thit b ny c th t 35M bit/s, nhng thc t thng ch t 1,5M bit/s, ty thuc vo nh cung cp dch v cp. Tc gi thng ip i t PC, cn c gi l tc ti ln vo khong 128K bit/s,

    u nhc im ca Modem cp l: - Vic dng chung lm nh hng n tc . truy cp mng s t l nghch

    vi s ngi truy cp trn cng mt nt mng - Mt vn khc cng c quan tm l tnh bo mt, - Kh trin khai trn nhng vng n c phn tn . - Khng c tnh di ng - Chi ph cao,v do phi lp t ng cp truyn hnh

    l nhng nguyn nhn m dch v ny khng c pht trin ph bin. 1.1.3 Truy nhp dch v bng rng qua v tinh (iPSTAR) [12]:

    H thng v tinh c nh:VSAT(Very Small Aperture terminal) c trin khai ch yu cc tnh min ni ca Vit Nam. Cc h thng ny c th cung cp tc t 9.6Kbps dn 8Mbps. Vit Nam hin ang s dng hai h thng VSAT DAMA/SCPC ch y phc v cho vng su vng xa v VSAT TDM/TDMA phc v cho nhu cu internet .[5]

    Nhc im chnh ca cc h thng ny l gi thnh cao,tr hnh trnh ln v chu nh hng ca thi tit.

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    5

    gim thiu nhng hn ch trn cng ty SSA-nh khai thc v tinh hng u chu pht trin h thng VSAT IP hay iPSTAR.i

    iPSTAR c nh gi l h thng v tinh bng rng a dch v em li nhiu tin ch.H thng thng tin v tinh bng rng iPSTAR h tr truyn s liu theo hng xung tc 4Mbps v 2Mbps hng ln..Cung cp cc dch v vin thng trn nn giao thc IP. c im ca VSAT-IP l thit b gn nh, d lp t, gi thnh thp hn nhiu so vi VSAT DAMA. V tin ch, VSAT-IP ngoi cung cp dch v in thoi, cn c kh nng cung cp cc ng dng m ch c dch v bng rng nh: thoi VoIP, Internet tc cao, truyn hnh hi ngh, mng ring o (VPN), knh thu ring, trung k mobile, truyn hnh qung b, truyn hnh theo yu cu. Vi dung lng h thng 35 Gbit/s. Dch v truy nhp bng rng cho vng nng thn c th thc hin qua truy nhp v tinh bng rng 2 ng.

    Hnh 2 h thng truy nhp v tinh iPTSAT

    Nhng u im v nhc im: - Cc h thng thng tin v tinh c phm vi trin khai dch v ln, khng ph

    thuc vo a bn, c th trin khai vng su vng xa ,nhng ni c a hnh phc tp m khng th trin khai c cc h thng nh xDSL .

    - Hn ch ca truy nhp bng rng qua v tinh l s ph thuc ca nh cung cp dch v vo nh qun l h thng v tinh. Hin nay, VNPT mua dung lng 2,5 Gbit/s trin khai dch v VSAT bng rng Vit Nam. Vic mua dung lng s ph thuc vo chnh sch ca nh qun l h thng iPSTAR. Bi vy, gii php ny khng th trin khai c lp trong vng nng thn khi lng khch hng ln, n cn phi kt hp vi cc gii php truy nhp mt t khc.

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    6

    - Ngoi ra, chi ph trin khai dch v cao, tui th ca h thng iPSTAR theo thit k l 12 nm v th gi thnh bng tn s khng gim d nhu cu s dng tng.

    1.1.4 Mng truy nhp v tyn

    Hin nay mng truy nhp v tuyn bng rng c xu hng pht trin nhanh hn so vi cc cng ngh truy nhp bng rng khc. L do l cng ngh ny c nhiu u im khi trin khai trn a hnh him tr m mng cp kh c th trin khai. So vi s dng v tinh th phng n ny c chi ph thp hn rt nhiu.

    n nay c rt nhiu cng ngh v tuyn kt ni bng rng mi, Trong lun vn ny ch cp n mt s cng ngh v tuyn bng rng sau.

    a/ HIPERLAN [14]

    HIPERLAN- L h thng cc chun cho WLAN ca vin tiu chun vin thng chu u ETSI- European Telecommunications Standards Institute. Nm 1991, ETSI thnh lp nhm RES10 .Nhm RES10 xy dng tiu chun HIPERLAN l chun thng tin lin lc s khng dy tc cao bng tn 5,1-5,3GHz v bng tn 17,2-17,3 GHz. C 4 loi HIPERLAN c a ra:HIPERLAN/1, HIPERLAN/2, HIPERCESS v HIPERLINK.vo nm 1996.

    HYPERLAN 1

    HYPERLAN 2

    HYPERLAN 3

    HYPERLAN 4

    ng dng Wireless LAN

    Truy nhp WATM

    Truy nhp WATM c nh t xa

    Kt ni PTP WATM

    Bng tn 2.4 GHz 5 GHz 5 GHz 17 GHz

    Tc t c

    23.5 Mbps 54 Mbps 54 Mbps 155Mbps

    Bng 2 Cc tiu chun ca ETSI HYPERLAN

    Cc chun m ETSI thit lp nh HiPerLAN/2 l mt chun cnh tranh trc tip vi chun 802.11 ca IEEE. Sau IEEE a ra chun 802.11h c th tng tc c vi chun HiPerLAN/2 ca ETSI.

    Trc , chun HiPerLAN/1 h tr tc ln n 24 Mbps s dng cng ngh DSSS trong phm vi 50m.HiPerLAN/1 s dng bng tn UNII thp v trung bnh ging nh HiPerLAN/2, 802.11a v 802.11h.

    HiperLAN2 [5].

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    7

    Trong cc chun ca HiperLAN, HiperLAN2 l chun c s dng rng ri nht bi nhng c tnh k thut ca n. Tc truyn d liu ca HiperLAN2 c th t ti 54 Mbps.C- th t c tc v HiperLAN2 s dng phng php gi l OFDM (Orthogonal Frequence Digital Multiplexing dn knh phn chia tn s). OFDM c hiu qu trong c cc mi trng m sng radio b phn x t nhiu im.

    HiperLAN Access Point c kh nng h tr vic cp pht tn s t ng trong vng ph sng ca n. iu ny c thc hin da vo chc nng DFS(Dynamic Frequence Selection) Kin trc HiperLAN2 thch hp vi nhiu loi mng khc nhau. Tt c cc ng dng chy c trn mt mng thng thng th c th chy c trn h thng mng HiperLAN2.

    u nhc im ca HIPERLAN

    - HIPERLAN bo mt tt hn IEEE802.11 - HIPERLAN2 c h tr QoS ,v cc HIPERLAN cn h tr cc loi mng li

    khc nh ATM,kt ni Ethernet trong khi 802.11 ch h tr kt ni Ethernet - HIPERLAN 2 cn c c tnh u vit nh c kh nng chn tn ng ,iu

    khin cng sut. - Hn ch ca HIPERLAN l pham vi ph sng gii hn 50m - Gi thnh thit b cao.

    b/ WiFi

    WiFi l mt nhn hiu cho dng sn phm tun th theo cc chun cho WLAN ca Vin k thut in t IEEE(Institute of Electrical and Electronics Engineers) vi cc chun sau:

    Chun IEEE

    Tc max:

    Mbit/s

    Phm vi (m)

    Di tn (GHz)

    Phm vi(Trong

    nh)

    Phm vi(ngoi

    tri)

    K thut v tuyn

    802.11 2 2,4 FHSS DSSS

    802.11b 11

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    8

    802.11 : y l chun u tin ca h thng mng khng dy. Chun ny cha tt c cng ngh truyn hin hnh bao gm Direct Sequence Spectrum (DSSS), Frequence Hopping Spread Spectrum (FHSS) v tia hng ngoi. 802.11 l mt trong hai chun miu t nhng thao tc ca sng truyn (FHSS) trong h thng mng khng dy. Nu ngi qun tr mng khng dy s dng h thng sng truyn ny, phi chn ng phn cng thch hp cho cc chun 802.11.

    802.11b Hu ht mng WLAN ngy nay tng thch vi chun 802.11b ca IEEE, cc sn phm bt u c xut xng vo cui nm 1999 v khong 40 triu thit b 802.11b ang c s dng trn ton cu

    802.11b c tc tn hiu ti a 11Mbps, vi thng lng trung bnh khong t 4 n 6 Mbps. Tc ny vn nhanh hn mt kt ni bng rng DSL hoc cp v cho m thanh lin tc (streaming audio), 802.11b li khng nhanh truyn nhng hnh nh c nt cao. Li th chnh ca 802.11b l ch ph phn cng thp.Do hot ng tn s 2.4GHz Ph ny b chia s bi cc thit b khng c cp php, chng hn nh cc thit b Bluetooth, in thoi khng dy v sng viba l ngun gc gy nhiu (v lm gim hiu sut hot ng) mng dng chun 802.11b. Cc mng dng chun 802.11b cng c th gy nhiu cho nhau, 14 knh ca chun 802.11b c chia thnh tng phn v ch c th dng 3 knh cng mt phm vi trnh chng cho. Cc knh thng c s dng trnh chng cho l 1, 6 v 11.

    802.11b+ PBCC (Packet Binary Convolutional Code) do Texas Instruments (TI) pht trin c th cung cp tc 22 v 33 Mbps. TI sn xut chipset da trn chun 802.11b v h tr PBCC 22 Mbps. Nhng thit b tch hp chipset ny c gi l thit b 802.11b+. Nhng thit b ny hon ton tng thch vi 802.11b, khi hai thit b 802.11b+ giao tip vi nhau c th t ng dng tc 22 Mbps. im ni bt khc ca TI khi giao tip gia cc thit b 802.11b+ l hot ng ch 4x, c ngha l dng cc gi tin c kch thc ln hn - 4000 byte - gim ti v tng thng lng ln n ba ln.

    802.11a : Vo cui nm 2001, cc sn phm da trn mt chun th hai, 802.11a, bt u c xut xng ,hot ng tn s 5GHz Thng lng l thuyt ti a ca n l 54 Mbit/s, vi tc ti a thc t t 21 n 22 Mbit/s. Mc d tc ti a ny vn cao hn ng k so vi thng lng ca chun 802.11b, phm vi pht huy hiu lc trong nh t 25 n 75 feet ca n li ngn hn phm vi ca cc sn phm theo chun 802.11b. Nhng chun 802.11a hot ng tt trong nhng khu vc ng c:

    Vi mt s lng cc knh khng gi ln nhau tng ln trong di 5 GHz,Trong mi trng vn phng thng thng, tm hot ng ca 802.11a c th ln n ti a 46m tc thp nht, v khong 23m tc cao nht.

  • H Cng Ngh - HQGHN T-VT

    ______________________________________________________________________ Lun vn:Tm hiu kh nng ng dng WiMAX ti Vit Nam

    9

    Khng ging dy tn s 2.4GHz, dy tn s 5GHz gn nh khng b nhiu. Vi u th v kch thc ca dy tn s, cc knh ca 802.11a khng b chng cho. Mt s nc nh ngha 4 knh, 8 knh hoc nhiu hn. Mt li ch khc m chun 802.11a mang li l bng thng cao hn ca n gip cho vic truyn nhiu lung hnh nh v truyn nhng tp tin ln tr nn l tng.

    802.11g : l chun ni mng khng dy c IEEE ph duyt thng 6 nm 2003. c tc ca 802.11a v tm hot ng ca 802.11b v tng thch ngc vi 802.11b.

    Tc ti a l thuyt ca cc sn phm theo chun 802.11a, 54 Mbit/s, vi mt thng lng thc t t 15 n 20 Mbit/s. Ging 802.11b, 802.11g c 14 knh v ch c th dng 3 knh cng mt phm vi trnh chng cho.Tc cao hn ca chun 802.11g cng gip cho vic truyn hnh nh v m thanh, li Web tr nn l tng. 802.11g thit k tng thch ngc vi 802.11b v chng chia s cng ph 2,4GHz. Vic ny lm cho cc sn phm ca 2 chun 802.11b v 802.11g c th hot ng tng thch vi nhau. 802.11g t tc ny bng cch dng OFDM (Orthogonal Frequency-Division Multiplexing), cng c ch vi 802.11a, v phi s dng thit b cng chn 802.11g. c th kt ni vi cc thit b 802.11b phi dng c ch iu bin CCK (Complimentary Code Keying). 802.11g cng tng thch vi cc thit b 802.11b+ hot ng tc 22 v 33Mbps s dng PBCC (Packet Binary Convolutional Code) ca Texas Instrumnets.

    802.11g+ :Ging 802.11b+, 802.11g+ do Texas Instruments (TI) pht trin da trn 802.11g ca IEEE vi cc tnh nng khc c thm vo. Cc thit b 802.11g+ tng thch vi cc thit b 802.11b v 802.11g. Khi kt ni vi thit b 802.11b+, cc u im ca TI s c pht huy. Khi kt ni cc thit b 802.11g+ vi nhau, c th t tc t...