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

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    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

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    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

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    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

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    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

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    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 tn hiu ln n 100Mbps.

    802.11n :Task Group N ca IEEE 802.11 c thnh lp vo thng 7 nm 2003 chun ha cho Physical Layers (PHY) v Medium Access Control Layer (MAC) ca 802.11, cho php cc ch hot ng c th t c thng lng t nht l 100Mbps.

    y l d n u tin ca 802.11 hng ti thng lng thay v tc tn hiu. Mt mc ch khc l t c thng lng cao tm hot ng rng, tng thch vi cc thit b 802.11a v 802.11g. Ban u d kin, cng vic chun ha s hon thnh vo cui nm 2005.Sau hon li v d kin s c cng nhn chnh thc vo cui nm 2006 nhng cho ti thi im ny vn cha c mt chun chnh thc.

    802.11n s dng h thng a ng ten v cng ph ln, u l nhng vn hc ba i vi hi k s in t (IEEE). Sau nhiu tr ngi vi xut v mt

  • H Cng Ngh - HQGHN T-VT

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

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    tiu chun mng khng dy tc cao, cui cng hip hi Wi-fi cng a ra c phin bn Draft 2.0 ca 802.11n, ng thi coi y l tiu chun sn cc nh sn xut c th xy dng cc thit b hot ng tt vi nhau.

    Hin nay, IEEE vn ang nghin cu a ra chun 802.11n chnh thc v hy vng cng vic s kt thc vo thng ba nm 2009. Tuy nhin cha c g m bo cc thit b da trn Draft 2.0 s tng thch vi cc thit b ca b chun chnh thc ny.v c phin bn Draft 2.0 ln chun chnh thc u c thit k c tc truyn d liu trn 100Mb/giy, nhanh hn c mt s kt ni Ethernet qua dy dn..

    u nhc im ca cng ngh theo chun IEEE 802.11

    - Kh nng di ng - cho php kt ni bt k u trong vng ph sng.. - D lp t v trin khai,thi gian trin khai nhanh. - Tc cao,tnh linh ng v nng cp d. - Gi thit b r v nhiu trn th trng. - Nhc im ca mng khng dy c th k n nht l kh nng nhiu sng

    do thi tit,cc thit b khng dy khc, hay cc vt chn - Vng ph sng ca IEEE 802.11cao hn HIPERLAN nhng cng ch hn

    ch tm vi chc n vi trm mt. - Bo mt cn nhiu l hng.

    c/ WiMAX.

    Trong thc t cng ngh WiFi pht trin rt rng ri tuy nhin vi phm vi ph sng nh,khng p ng c nhu cu ngy cng cao ca ngi dng, WiMAX c thit k cho mng MAN nn khc phc hn c ch trn. Cng ngh ny s c ni chi tit trong mc 1.2

    Tng kt

    - xDSL ph hp cho vng c mng cp ng. Gii php ny em li li nhun ngay cho nh cung cp .

    - iPSTAR s l gii php truy nhp bng rng hiu qu cho cc vng khng th trin khai cc gii php truy nhp mt t, c bit l vng su vng xa, tuy nhin gi c v chi ph vn cao hn so vi truy nhp v tuyn.

    - HIPERLAN tt hn v u vit hn IEEE 802.11 nhng gi thnh thit b li cao v thit b t

    - Wi-Fi.cho tc d truy nhp cao .Vic trin khai kh n gin, m gi thnh li thp hn nhiu so vi cng ngh trn . Tuy nhin vng ph sng ca WiFi b hn ch.

  • H Cng Ngh - HQGHN T-VT

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

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    - WiMAX:gii php cng ngh ra i sau nn c tch hp rt nhiu cc u im v khc phc phn ln nhc im ca cc cng ngh trc,y l cng ngh hin i v c nh gi cao.

    1.2 Tng quan v WiMAX [13]

    Wi-Fi c bn knh ph sng ca mt im thu pht sng (hotspot) ch l 150 m nn cn nhiu hotspot cho mt khu vc nht nh v cng c nhiu ngi s dng Wi-Fi th tc cng gim.Mt khc,cht lng ca Wi-Fi khng c tt bng ADSL, khng m bo c ch u tin nh WiMAX.

    WiMAX l t vit tt ca Worldwide Interoperability for Microwave Access c ngha l kh nng tng tc ton cu vi truy nhp vi ba.Vi WiMAX c nh c tc tng ng vi ADSL, trong khi khng cn dng dy dn n cc thu bao. Ngi s dng cc thit b u cui ch cn mua mt thit b Indoor WiMAX (kch thc bng mt modem ADSL) l c th dng c Internet tc cao. WiMAX di ng c t ln hn WiFi nhng phm vi ph sng ln hn rt nhiu so vi Wifi

    Cng ngh WiMAX, l cng ngh khng dy bng thng rng ang pht trin rt nhanh vi kh nng trin khai trn phm vi rng v c coi l c tim nng to ln tr thnh gii php dm cui l tng nhm mang li kh nng kt ni Internet tc cao ti cc gia nh v cng s

    1.2.1 Din n WiMAX

    Din n WiMAX l mt t chc ca cc nh khai thc v cc cng ty thit b v cu kin truyn thng hng u.

    Mc tiu ca Din n WiMAX l thc y v chng nhn kh nng tng thch ca cc thit b truy cp v tuyn bng rng tun th chun 802.16 ca IEEE v cc chun HiperMAN ca ETSI.

    Din n hp tc cht ch vi cc nh cung cp v cc c quan qun l .m bo cc h thng c din n ph chun s p ng cc yu cu ca khch hng v ca cc chnh ph nhm loi b cc ro cn tin ti vic chp nhn rng ri cng ngh truy cp v tuyn bng rng BWA (Broadband Wireless Access), v ring mt chun th khng khuyn khch vic chp nhn rng ri mt cng ngh.

    1.2.2 Cc c im ca WiMAX

    WiMAX c tiu chun ho IEEE 802.16. H thng ny l h thng a truy cp khng dy s dng cng ngh OFDMA c cc c im sau :

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    - Khong cch gia trm thu v pht c th ti 50km - Tc truyn c th thay i, ti a 70Mbit/s. - Hot ng trong c hai mi trng truyn dn: ng truyn tm nhn thng

    LOS (Line of Sight) v ng truyn b che khut NLOS (Non line of sight). - Di tn lm vic 2-11GHz v t 10-66GHz hin v ang c tiu chun

    ho. - Trong WiMAX hng truyn tin c chia thnh hai ng ln v xung.

    ng ln c tn s thp hn ng xung v u s dng cng ngh OFDM

    - WiMAX s dng iu ch nhiu mc thch ng t BPSK, QPSK n 256-QAM kt hp cc phng php sa li d liu nh ngu nhin ho, vi m ho sa li Reed Solomon, m xon t l m t 1/2 n 7/8.

    - rng bng tn ca WiMAX t 5MHz n trn 20MHz c chia thnh nhiu bng con . Vi cng ngh OFDMA, cho php nhiu thu bao c th truy cp ng thi mt hay nhiu knh mt cch linh hot m bo ti u hiu qu s dng bng tn.

    - Cho php s dng c hai cng ngh TDD (time division duplexing) v FDD (frequency division duplexing) cho vic phn chia truyn dn ca hng ln (uplink) v hng xung (downlink).

    - H thng WiMAX c phn chia thnh 4 lp con : Cc lp ny tng ng vi hai lp di ca m hnh OSI v c tiu chun ho c th giao tip vi nhiu ng dng lp trn .

    1.2.3 Chun IEEE 802.16

    WiMAX da trn tiu chun 802.16 ca IEEE v HiperMAN ca ETSI.

    IEEE 802.16-2001: Chun ny c xy dng t thng 9/2000 v c IEEE thng qua vo thng 12/2001. 802.16-2001 xc nh giao din v tuyn gm lp MAC v PHY ca h thng truy nhp v tuyn c nh im a im vi nhng mc ch:

    - Cho php trin khai nhanh chng v rng ri cc h thng truy nhp v tuyn bng rng vi chi ph hiu qu.

    - m bo kh nng tng thch gia cc thit b truy nhp v tuyn bng rng ca cc hng khc nhau.

    - Tng tc qu trnh thng mi ha ,ph cp truy nhp v tuyn bng rng ,a ra cc gii php thay th cho truy nhp bng rng hu tuyn.

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    Hnh 3 : cc chun ca IEEE 802.16

    c im ca 802.16-2001: - Di tn t 10 66GHz knh vt l thng l 25/28 MHz - ng truyn LOS. - Phng php iu ch l QPSK,16/64QAM - Tm hot ng t 2-7 km

    Ta nhn thy nhc im ca truyn LOS v hu ht trn thc t l kiu NLOS hoc ng truyn thng nhng c vt cn (OLOS),trc nhng hn ch th bn 802.16.2 c a ra.

    IEEE 802.16.2-2001 cp vo thng 10/2007 tp trung vo gii quyt vn can nhiu.trong di hot ng c nh 10 66GHz nhng c bit quan tm ti di t 23.5-43.5GHz.

    IEEE802.16 Con 1-2003:[5] chun ny cng b s ph hp v thc thi giao din khng gian MAN-SC v tuyn trong di 10-66GHz. Tiu chun ny cng b s ph hp v thc thi giao thc cc ch tiu k thut ph hp ca cc trm gc v cc trm thu bao da trn giao din khng gian MAN-SC (10-66GHz) c xc nh trong tiu chun 802.16.

    IEEE 802.16 Con 2-2003: [5] Tiu chun ny gii thiu cu trc thit b o v mc ch o ,kim tra s ph hp cc ch tiu k thut ca cc trm gc v cc trm thu bao da trn giao din khng gian c xc nh trong chun 802.16.

    IEEE 802.16a . c thng qua thng 1/2003.phin bn ny b sung cho thiu st ca 802.16-2001 vi vic b xung thm di tn s 2- 11 GHz. Gip cho vic

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    truyn sng trong mi trng c vt cn v b che khut dng hn.,b sung cc k thut cho lp vt l gip ti u knh truyn theo bng tn ca ng dng

    IEEE 802.16b: Chun ny hot ng trn bng tng t 5 6 Ghz vi mc ch cung ng dnh v vi cht lng cao (QoS). C th chun u tin truyn thng tin ca nhng ng dng video, thoi, real-time thng qua nhng lp dch v khc nhau. Chun ny sau c kt hp vo chun 802.16a

    IEEE 802.16c. c chp nhn vo thng 12/2002 y l bn sa i ca chun 802.16-2001 Chun ny nh ngha thm cc profile mi cho di bng tng t 10-66GHz vi mc ch ci tin thao tc ga cc phn(interoperability).

    IEEE 802.16-2004 hay IEEE 802.16d c IEEE thng qua thng 6/2004. Chun ny s dng bng tng c bn quyn t 2 11 Ghz. y l bng tng thu ht c nhiu quan tm nht v tn hiu truyn c th vt c cc chng ngi trn ng truyn. 802.16a cn thch ng cho vic trin khai mng Mesh m trong mt thit b cui (terminal) c th lin lc vi BS thng qua mt thit b cui khc. Vi c tnh ny, vng ph sng ca 802.16a BS s c m rng.

    IEEE 802.16-2004 Tp trung vo cc ng dng c nh v lu tr trong di tn s 2 -11 GHz. Hai k thut iu ch a sng mang c h tr trong 802.16-2004:

    - OFDM vi 256 sng mang v - OFDMA vi 2048 sng mang.

    Cc h s chng nhn u tin ca .Din n WiMAX u da trn OFDM, nh c nh ngha trong phin bn ny ca tiu chun . Cc thit b WiMAX hin ti c trn th trng l da trn chun ny.

    IEEE 802.16e c thng qua thng 12/2005. Din n WiMAX s bt u qu trnh chng nhn thit b ban u trong cc bng tn 3.3 n 3.8 GHz v 5.7 n 5.8 GHz.Vi kh nng p ng c cc ng dng c nh cng nh cc dch v di ng, nn cn c gi l WiMAX di ng. Chun ny v ang c th nghim nhiu nc. Hin ti, WiMAX di ng "Wave 2" dng 2 ng-ten pht v 2 ng-ten thu cho tc ti a tm 75Mbps.

    IEEE 802.16e: H tr cho vic khai thc s kt hp gia dch v c nh v di ng ti cc tn s di 6 GHz.

    Tiu chun ny m ra s h tr SOFDMA (mt bin th ca OFDMA), n tnh n s lng cc sng mang c th bin i, ngoi cc phng thc OFDM v OFDMA c nh ngha trc y. Vic gn sng mang trong cc phng thc

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    OFDMA c thit k gim thiu tc ng ca can nhiu ti thit b ngi dng vi cc anten ton hng.

    Tng cng h tr cho MIMO (Multiple Input Multiple Output) v cc h thng anten thch nghi (AAS), cng nh chuyn v (handoff) cng v mm. N cng ci thin c cc kh nng tit kim ngun cho cc thit b di ng v cc tnh nng an ton mnh hn. C hai sn phm da trn OFDM v trn OFDMA u c th tn dng cc dung lng mi m rng.

    Trong phn sau, chng ta coi cc nh dng ca 802.16e WiMAX ch yu nh l vic chp nhn SOFDMA, cn cc nh dng 802.16-2004 nh l vic s dng OFDM vi 256 sng mang. Phin bn mi ca tiu chun 802.16 c tnh tng thch ngc, cho nn cc yu cu k thut mi ca phng thc OFDM l tng thch vi cc phin bn trc. Tuy nhin, cc hng thc OFDM v SOFDMA s khng tng thch nu chng da trn hai k thut iu ch khc nhau. Kt qu l, loi CPE ca OFDM ch n mode (single mode) s khng lm vic c trong mt mng SOFDMA v ngc li, mt CPE ca SOFDMA s khng lm vic trong mt mng OFDM.y cugnx l mt hn ch ca .

    IEEE 802.16j: By gi IEEE ang bt tay vo chun ha 802.16j phc v cho vic Relay (WiMAX Mesh network).

    Hnh 4: m hnh mng Mesh trong WiMAX

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    Li ch ca vic dng nhng relay BS c lit k trong hnh v. C th k n cc li ch sau:

    - Thay v lin lc trc tip vi BS, ngi dng c th lin lc thng qua nhiu Relay BS vi ng truyn tt hn v tc cao hn, hiu qu truyn cao hn, v.v..

    - Relay BS c th dng tng vng ph sng ca mng WiMAX (relay BS r hn lp t BS WiMAX)

    - Ngi dng s khng cn tiu tn mt nng lng ln lin lc vi BS (tit kim nng lng tiu th thit b di ng).

    802.16m: ang c nghin cu v chun ha. Chun ny hng ti tng tc truyn ca WiMAX ln 1Gbps bng cch dng MIMO trn nn cng ngh a truy nhp OFDMA vi s lng ngten pht v thu nhiu hn WiMAX di ng Wave 2 . 802.16m trang b 4 ng-ten pht v 4 ng-ten thu s c th y tc truyn ln ln hn 350Mbps,v vn tng thch vi WiMAX c nh v di ng v ang c trin khai Theo d kin, WiMAX Release 2 vi s hon thin ca 802.16m s hon thnh vo cui nm 2009 v c th bt u trin khai dch v t 2010

    Bng 4 :So snh cc chun 802.16 [4]

    802.16 802.16a 802.16d 802.16e Ph (GHz) 10 66 2 11 2 11 2 6

    Cu hnh Trc x Khng trc xa Khng trc x Khng trc x

    Tc bit 32 134 Mbps

    Knh 28 MHz

    75 Mbps

    Knh 20 MHz

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    Ngoi ra cn c nhiu chun b sung khc ang c trin khai hoc ang trong giai on chun ha nh 802.16g, 802.16f, 802.16h...

    im khc nhau gia cc phin bn 802.16 nh 802.16a,802.16-2004 v 802.16e

    - Chun 802.16a ca IEEE tp trung vo truy cp bng rng c nh. - Chun m rng 802.16-2004 ca IEEE ci tin hn nh h tr cho CPE trong

    nh. - Chun802.16e l mt m rng ca chun 802.16-2004. Mc ch ca chun

    802.16e l b sung kh nng di ng d liu cho chun hin thi, m ban u thit k ch yu dnh cho c nh.

    WiMAX 802.16-2004. Chun ny da trn phin bn 802.16-2004 ca IEEE 802.16 v ETSI - HiperMAN. N s dng Ghp knh Phn chia theo tn s trc giao (OFDM -Orthogonal Frequency Division Multiplexing), h tr truy nhp c nh v di tr trong cc mi trng Trc th (LOS - Line of Sight ) v Khng trc th (NLOS Non Line of Sight). Cc hng sn xut ang trin khai Thit b khch hng (CPE) trong nh v ngoi tri v th PCMCIA cho laptop. Cc nh dng (profile) ban u ca Din n WiMAX trong bng tn 3,5 GHz v 5,8 GHz. Cc sn phm c chng nhn u tin xut hin vo cui nm 2005.

    WiMAX 802.16e. Ti u ho cho cc knh v tuyn di ng, phin bn ny da trn s hiu chnh 802.16e v h tr chuyn v (handoff) v chuyn vng (roaming). N s dng Truy nhp ghp knh phn chia theo tn s trc giao c th m rng thang (SOFDMA Scalable Orthogonal Frequency Division Multiplexing Access), mt k thut iu ch a sng mang c s dng to knh ph (sub-channelization). Cc nh cung cp dch v ang trin khai 802.16e cng c th s dng mng ny cung cp dch v c nh. Vic cp chng ch d kin s c bt u vo gia nm 2006, khi khai trng cc phng th nghim chng nhn WiMAX di ng, vi cc sn phm c cp chng ch u tin c mt nm 2007

    im khc nhau gia IEEE 802.16 v cng ngh WiMAX

    Mc tiu chnh ca Din n WiMAX l to ra mt chun tng thch t chun 802.16 ca IEEE v cc chun HiperMAN ca ETSI. iu ny s thc hin c nh vic hnh thnh cc m t h thng. Da trn nhng g m Din n WiMAX xem xt v cc iu khon ca nh cung cp dch v v cc k hoch thit b ca cc nh cung cp, Din n WiMAX quyt nh tp trung trc tin vo cc m t cho phng thc PHY OFDM 256 ca chun 802.16 nm 2004, c IEEE thng qua vo thng 6/2004. Lp vt l (PHY) s c kt hp vi mt b iu khin truy nhp phng tin (MAC) c lp m bo mt nn tng thng nht cho tt c nhng trin khai WiMAX.

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    Tun th theo chun 802.16 khng c ngha l thit b c Din n WiMAX chng nhn hoc c th tng thch vi cc thit b ca cc nh cung cp khc. Tuy nhin nu mt thit b tun th thit k c Din n WiMAX chng nhn th va tun th chun 802.16 v tng thch vi c thit b ca cc nh khai cp khc.

    1.2.4 Cc nh dng ca din dn WiMAX [5]

    Vic la chn cc nh dng c thc y bi nhu cu th trng, kh dng ca ph tn, nhng rng buc v chnh sch, cc dch v cn cung cp v u t ca cng ty.

    V d nh, tnh kh dng ph tn cho cc dch v v tuyn bng rng mt s nc l ng lc thc y vic to ra cc nh dng ban u trong bng tn 3,5 GHz. Tnh kh dng ca cc ph min php v nhu cu v cc dch v c nh quyt nh vic to ra mt nh dng trong bng tn 5,8 GHz. Nhu cu v cc dch v di ng v tnh kh dng ph lm cho cc bng tn 2,3 GHz v 2,5 GHz chc chn tr thnh mc tiu cho cc nh dng ca 802.16e. Cc nh dng ca Din n WiMAX c xc nh bi cc tham s sau y:

    - Di ph : bng tn c dng cho dch v WiMAX do cc t chc qun l cung cp .Hin ti c 2 loi bng tn dnh cho WiMAX l:

    o Bng tn cp php :2.3 2.6 GHz v 3.3 3.6 GHz o Bng tn khng cp php 5.7 -5.8 GHz

    - Song cng. Hai tu chn sn c: Song cng phn chia theo thi gian (TDD) cho cc nh khai thc c ph khng cp i hoc ph min php, v Song cng Chia theo Tn s (FDD). FDD i hi hai knh, mt cho lu lng tuyn ln v knh kia cho lu lng tuyn xung. Trong mt mng TDD, lu lng ch chim mt knh duy nht vi lu lng tuyn ln v tuyn xung c gn cc khe thi gian khc nhau.

    - rng (Bng thng) knh. Bng thng ca knh ph thuc rt cao vo ph do cc nh chnh sch phn b. Nhng nh dng ban u c hn ch cho 3,5 MHz v 7 MHz trong phtn c cp php khi chng l cc knh c ph thng dng c phn b trong bng tn 3,5 GHz. Khi cc nh khai thc c kh nng s dng cc knh rng hn, th cc thnh vin ca Din n WiMAX s b sung cc nh dng chng nhn vi cc bng thng ca knh rng hn.

    - Tiu chun IEEE. Cc nh dng ca 802.16-2004 s dng OFDM vi 256 sng mang. Cc nh dng ca 802.16e hu nh chc chn da trn SOFDMA. Ch tiu chun ny mi h tr tnh di ng.

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    Tt c cc nh dng chng nhn da trn 802.16-2004 u theo mt nh dng h thng chung. nh dng ny bao gm cc yu cu k thut ca WiMAX, duy tr bt k tham s no d l tn s, kch thc knh hay phng php to song cng. Mt nh dng h thng mi va c pht trin gn y cho cc nh dng chng nhn 802.16e. Nu c mi quan tm t cng ng cc nh sn xut, mt nh dng h thng th ba c th c gii thiu cho cc sn phm 802.16-2004 h tr kh nng xch tay v di ng gii hn. Cc nh dng ban u c Din n WiMAX xc nh h tr truy nhp c nh v lu tr trong cc bng tn 3,5 GHz v 5,8 GHz.

    Tn s (MHz)

    Song cng

    Bng thng knh (MHz)

    K hiu nh dng

    Ghi ch

    3400-3600 TDD 3.5 3.5T1 Hin ti

    3400-3600 FDD 3.5 3.5 F1 Hin ti

    3400-3600 TDD 7 3.5T2 Hin ti

    3400-3600 FDD 7 3.5 F2 Hin ti

    5725-5850 TDD 10 5.8T Hin ti

    2300-2600 TDD 5.0/5.5 2.5 T1 Tng lai

    2300-2600 FDD 5.0/5.5 2.5 F1 Tng lai

    Bng 5 :cc nh dng chng nhn ca in n WiMAX

    1.3 Cc m hnh ng dng [2]

    WiMAX c xut 2 m hnh ng dng l c nh vdi ng.

    1.3.1 M hnh ng dng c nh (Fixed WiMAX)

    M hnh c nh s dng cc thit b theo tiu chun IEEE.802.16-2004. Tiu chun ny gi l khng dy c nh v thit b thng tin lm vic vi cc anten t c nh ti nh cc thu bao. Anten t trn nc nh hoc trn ct thp tng t nh cho thng tin v tinh

    Tiu chun IEEE 802.16-2004 cng cho php t anten trong nh nhng tt nhin tn hiu thu khng tt bng anten ngoi tri. Bng tn cng tc (theo quy nh v phn b ca quc gia) trong bng 2,5GHz hoc 3,5GHz. rng bng tng l 3,5MHz. Trong mng c nh, WiMAX thc hin cch tip ni khng dy n cc modem cp, n cc i dy thu bao ca mch xDSL hoc mch Tx/Ex (truyn pht/chuyn mch) v mch OC-x (truyn ti qua sng quang).

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    Hnh 5 :M hnh ng dng WiMAX c nh

    WiMAX c nh c th phc v cho cc loi ngi dng nh: cc x nghip, cc khu dn c nh l, mng cp truy nhp WLAN cng cng ni ti mng th, cc trm gc BS ca mng thng tin di ng v cc mch iu khin trm BS. V cch phn b theo a l, ngi dng c th phn tn ti cc a phng nh nng thn v cc vng su vng xa kh a mng cp hu tuyn n .

    1.3.2 M hnh ng dng WiMAX di ng

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    Hnh 6 :M hnh ng dng WiMAX di ng

    M hnh WiMAX di ng s dng cc thit b ph hp vi tiu chun IEEE 802.16e c thng qua trong nm 2005.Tiu chun 802.16e b sung cho tiu chun 802.16-2004 hng ti cc ngi dng c nhn di ng, lm vic trong bng tn thp hn 6GHz. Mng li ny phi hp cng WLAN, mng di ng cellular 3G c th to thnh mng di ng c vng ph sng rng. Hy vng cc nh cung cp vin thng hip ng cng tc thc hin c mng vin thng s truy nhp khng dy c phm vi ph sng rng tha mn c cc nhu cu a dng ca thu bao.

    Vic la chn trin khai trn din rng vi WIMAX di ng hay c nh l cu hi ca nhiu nc.S so snh di y s lm r s khc bit gia 2 chn ny

    1.4 So snh WiMAX 802.16-2004 v 802.16e [ 4]

    Cc trin khai di ng v c nh c cc nhu cu rt khc nhau v cc mc tiu phn on th trng khc nhau v c bn, vi cc v tr v m hnh s dng, cc nhu cu v thng lng, cc dng thit b ngi dng v cc SLA khc nhau. C hai s b sung ca WiMAX c nh ngha p ng cc nhu cu khc nhau ca hai phn on th trng v cc yu cu khc nhau ca cc ng dng khc nhau.

    Trong mt trin khai c nh vi cc chc nng c bn, 802.16-2004 v 902.16e ngh hiu nng tng ng. Thng lng cc ai mt sector cho c hai phin bn ca WiMAX l 15Mbps cho knh 5MHz, hoc 35Mbps cho knh 10MHz. Phm vi trm gc trong cc vng dn c ng c c th khong vi km ty thuc vo cc thuc tnh nh l loi CPE, bng tn, tnh di ng ..vv. Trong cc mng m dung lng b chi phi, s lng trm gc c lp t ty thuc vo nhu cu thng lng v phm vi.

    Tuy nhin, hiu nng ca hai phin bn WiMAX c th thay i v c bn cho cc ng dng c th bi v 802.16-2004 l ti u cho truy nhp c nh v 802.16 l cho truy nhp di ng mc d WiMAX cng c th c s dng cho truy nhp c nh.

    Cc mng c nh c th thu li nhun t nhiu thun li c a ra bi cc sn phm c chng nhn ca WiMAX Forum theo 802.16-2004.

    iu ch t phc tp: OFDM l mt cng ngh iu ch n gin hn v ph hp hn trin khai m khng yu cu h tr tnh di ng.

    Cc bng tn khng cp php: Cc dch v di ng yu cu ph cp php cung cp s bao ph trong cc vng rng ln. Tuy nhin cc trin khai c nh thng s dng thnh cng cc bng tn khng cp php trong cc vng m cc

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    mc nhiu l c th chp nhn c. V l do ny m hu ht cc Profile nhm vo cc bng tn khng cp php l ph hp khi da trn c s 802.16-2004.

    Thng lng cao hn: Cc bng ph cao hn c la chn cho cc Profile 802.16-2004 dn n kt qu thng lng cap hn. iu ny l mt thun li d thy, c bit khi nhm vo cc ngi dng kinh doanh vi mc lu lng cao hn v vi cc CPE c cc anten t ngoi tri.

    Thi im a vo th trng ph hp hn: Tnh sn sng v thng mi sm hn ca cc sn phm 802-16-2004 cho php cc nh khai thc p ng nhu cu dn nn cho cc kt ni bng rng trong cc vng di mc phc v, v bt u t ti s chia s th trng gia cc nh cnh tranh hng u.

    Mt mt khc, mt s nh khai thc c th quyt nh i cc Profile 802.16e v nhiu l do:

    H tr tnh di ng: Cc sn phm 802.16e l ti u cho tnh di ng v s c h tr chuyn giao ln n 120km/h.

    H tr cho cc kiu cng sut sleep v saving tng thi gian sng ca cc thit b ngi dng di ng

    Bao ph trong nh tt hn: Bao ph trong nh tt hn t ng thng qua knh con ha v cc li ch ca ty chn AAS c cc ng dng c nh v di ng, bi v cc ngi dng thng l trong nh hay khng trong tm nhn thng. Tuy nhin, trong khi cc anten ngoi tri c th b li v hn ch bao ph trong nh cc trin khai c nh th iu ny r rng khng phi l mt ty chn cho cc ngi dng di ng vi mt laptop hay mt PDA.

    mm do tt hn trong vic qun l cc ti nguyn ph: knh con ha cng mang li kh nng s dng s thng minh ca mng cp pht ti nguyn cho cc thit b ngi dng khi c nhu cu. Thc t iu ny dn n kt qu tng hiu nng s dng ph, iu khin thng lng cao hn v bao ph trong nh tt hn v trong mt vi trng hp lm cho chi ph trin khai thp hn. Iu ny c bit hiu qu vi cc nh khai thc vi ph hn ch.

    Phm vi rng ln ca cc dng nhn t cho cc thit b ngi dng: trong khi cc CPE trong nh v ngoi nh, v cc card PCMCIA my tnh xch tay c mong i thng tr th trng 802.16-2004 th cc card PCMCIA my tnh xch tay, cc card mini, cc modem trong nh, cc PDA v cc in thoi s sn sng gia cc thit b ngi dng 802.16e. S a dng ny cho php cc nh khai thc m rng cc dch v ca h n cc phn on th trng mi v tng thm s t do cho cc thu bao ca h. Mc d cc sn phm 802.16e c gii thiu mun hn

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    nhng c th hi vng rng gi c CPE ca chng s nhanh chng gim thp hn cc CPE theo 802.16-2004 khi cc sn phm 802.16e c nhm vo mt th trng rng ln hn. Vi chi ph CPE in hnh l thay i quan trong nht trong bt k k hoch kinh doanh ca nh khai thc, tnh sn c ca cc Chip CPE s l mt trong cc nhn t hng dn cho vic quyt nh phin bn no ca WiMAX c thng qua.

    La chn gia 802.16-2004 v cc sn phm 802.16e ty thuc phn ln vo cc loi dch v c cung cp v cc kiu kinh doanh ca cc nh khai thc. Trong mt vi trng hp, la chn s l hin nhin. Mt nh khai thc di ng xy dng mt mng bao ph b sung cho mng 3G s tin thng n 802.16e. Mt nh cung cp dch v Internet khng dy cung cp truy nhp khng dy cho lin lc vng nng thn s chn cc sn phm WiMAX 802.16-2004 da trn OFDM t phc tp hn.

    Thm vo cc nh khai thc cn tnh n nhiu nhn t khc m c th nh hng n la chn gia cc sn phm 802.16-2004 v 802.16e.

    Mc tiu th trng: nu nh khai thc nhm vo cc ngi dng kinh doanh v cc ngi dng vng dn c trong mt mi trng hu nh l tm nhn thng, cc CPE vi mt anten ngoi tri s c thng lng tt hn v hiu nng LOS c th ph hp hn. iu ny c th lm cho nh khai thc hng ti mt trin khai 802.16-2004. Nu thay th nh khai thc nhm vo th trng di ng, cc CPE 802.16e chi ph thp c th c yu cu cho k hoch kinh doanh c th pht trin.

    Ph: Trong khi WiMAX Forum s tip tc thm vo cc Profile mi ph hp vi nhu cu th trng, iu ch ph hp vi cc Profile 802.16-2004 hoc 802.16e trong mt s bng tn. Trong hu ht cc trng hp nh khai thc s c mt vi la chn qua cc bng ph sn c v la chn ca WiMAX c th ty thuc vo tnh sn c ca sn phm. N c th l cc Prpfile 802.16e s c thm vo cc bng tn in hnh dnh cho cc ng dng c nh v mang xch, bi v 802.16e c t c kh nng xy ra nhiu a ng.

    iu tit: Mt s nh iu tit y quyn cc loi dch v c th m c th c ngh trong mt bng ph. Chng hn, mt s nh iu tit Chu u gii hn ph 3.5GHz cho cc dch v c nh v mang xch, iu ny c th ngn cn s thng qua ca 802.16e khi WiMAX h tr cc dch v di ng, thm ch cc giy php ph in hnh khng y quyn s dng mt cng ngh c th.

    Tnh hp thi: Tnh c sn sm hn ca cc sn phm 802.16-2004 trong cc bng tn 3.5GHz s l mt nhn t quan trng cho cc nh cung cp dch v mun trin khai mt mng WiMAX nhanh chng.

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    1.5 Bng tn cho WiMAX[4]

    Cc bng c WiMAX Forum tp trung xem xt v vn ng c quan qun l tn s cc nc phn b cho WiMAX l:

    1. 3600-3800MHz 2. 3400-3600MHz (bng 3.5GHz) 3. 3300-3400MHz (bng 3.3GHz) 4. 2500-2690MHz (bng 2.5GHz) 5. 2300-2400MHz (bng 2.3GHz) 6. 5725-5850MHz (bng 5.8GHz) 7. 700-800MHz (di 1GHz).

    Bng 3400-3600MHz (bng 3.5GHz)

    Bng 3.5Ghz l bng tn c nhiu nc phn b cho h thng truy cp khng dy c nh (Fixed Wireless Access FWA) hoc cho h thng truy cp khng dy bng rng (WBA). WiMAX cng c xem l mt cng ngh WBA nn c th s dng bng tn ny cho WiMAX. V vy, WiMAX Forum thng nht la chn bng tn ny cho WiMAX.

    Bng tn ny s dng cho chun 802.16-2004 cung cp cc ng dng c nh v nomadic, rng phn knh l 3.5MHz hoc 7MHz, ch song cng TDD hoc FDD.

    Mt s nc quy nh bng tn ny ch dnh cho cc h thng cung cp cc dch v c nh, khng c ng dng nomadic, nn trin khai c WiMAX cn thit phi sa i li quy nh ny.

    i vi Vit Nam, do bng tn ny c u tin dnh cho h thng v tinh Vinasat nn hin ti khng th trin khai cho WiMAX.

    Bng 3600-3800MHz:

    c mt s nc chu u xem xt cp cho WBA. Tuy nhin, do mt phn bng tn ny (t 3.7-3.8GHz) ang c nhiu h thng v tinh vin thng s dng (ng xung bng C), c bit l khu vc chu , nn t kh nng bng tn ny s c chp nhn cho WiMAX chu .

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    Bng 3300-3400MHz (bng 3.3 GHz):

    Bng tn ny c phn b n , Trung Quc v Vit Nam ang xem xt phn b chnh thc. Do n v Trung Quc l hai th trng ln, nn d cha c nhiu nc cp bng tn ny cho WBA, nhng thit b WiMAX cng c sn xut.

    Chun WiMAX p dng bng tn ny tng t nh vi bng 3.5GHz, l WiMAX c nh, ch song cng FDD hoc TDD, rng knh 3.5MHz hoc 7MHz.

    Do n ch cho php s dng on bng tn 3316-3400MHz, nn cc thit b WiMAX hin ti cng ch lm vic trong on ny vi ti a 2x9 knh 3.5MHz. V vy, nu c 4 nh khai thc s dng bng tn ny th thng mi nh khai thc ch c cp s dng 2x2 knh 3.5MHz. Trong khi , theo kin ca cc chuyn gia Alvarion, mt trong nhng hng cung cp thit b WiMAX, th khai thc hiu qu, mi nh khai thc nn c cp t nht 2x3 knh 3.5MHz.

    Bng 2500-2690MHz (bng 2.5 GHz)

    Bng tn ny l bng tn c WiMAX Forum u tin la chn cho WiMAX di ng theo chun 802.16-2005. C hai l do cho s la chn ny.

    - Th nht, so vi cc bng trn 3GHz iu kin truyn sng ca bng tn ny thch hp cho cc ng dng di ng.

    - Th hai l kh nng bng tn ny s c nhiu nc cho php s dng WBA bao gm c WiMAX. WiMAX bng tn ny c rng knh l 5MHz, ch song cng TDD, FDD.

    Bng tn ny trc y c s dng ph bin cho cc h thng truyn hnh MMDS trn th gii, nhng do MMDS khng pht trin nn Hi ngh Thng tin V tuyn th gii nm 2000 (WRC-2000) xc nh c th s dng bng tn ny cho h thng di ng th h 3 (3G hay IMT-2000 theo cch t tn ca ITU). Do cha c cu tr li r nn hin c mt s nc nh M, Brazil, Mexico, Singapore, Canada, Lin hip Anh (UK), Australia cho php s dng mt phn bng tn tn ny cho WBA. Trung Quc v n cng ang xem xt.

    V d, Singapore chia bng 2.5GHz thnh 15 khi 6 MHz cho WBA u thu, theo nh khai thc c cung cp cc dch v c nh, nomadic v di ng, khng yu cu phi s dng mt cng ngh c th no. Cc nh khai thc trng thu c trch nhim t phi hp vi nhau v vi cc nh khai thc ca cc nc lng ging trnh can nhiu. Ti M, y ban Truyn thng Lin bang (FCC) chia bng

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    2.5GHz thnh 8 khi, mi nh khai thc c th c cp 22.5MHz, gm mt khi ph c rng 16.5MHz kt hp vi khi 6MHz.

    Do ITU xc nh bng tn ny cho IMT-2000, nn WiMAX Forum ang c k hoch tham gia vo cc nhm nghin cu ca ITU thc y vic a chun 802.16 thnh mt nhnh ca h tiu chun IMT-2000

    Vi Vit Nam, Quy hoch ph v tuyn in quc gia c Th tng Chnh ph ph duyt cui nm 2005 quy nh bng tn 2500-2690 MHz s c s dng cho cc h thng thng tin di ng th h mi, khng trin khai thm cc thit b khc trong bng tn ny. V vy, c th hiu cng ngh WiMAX di ng cng l mt i tng ca quy nh ny, nhng bng tn ny s c s dng cho loi hnh cng ngh c th no vn cn m.

    Bng 2300-2400MHz (bng 2.3 GHz):

    Bng 2.3GHz cng c c tnh truyn sng tng t nh bng 2.5GHz nn l bng tn c WiMAX Forum xem xt cho WiMAX di ng.

    Hin c mt s nc phn b bng tn ny cho WBA nh Hn Quc (trin khai WiBro), c, M, Canada, Singapore. Singapore cho u thu 10 khi 5MHz trong di 2300-2350MHz s dng cho WBA vi cc iu kin tng t nh vi bng 2.5GHz. c chia bng tn ny thnh cc khi 7MHz, khng qui nh c th v cng ngh hay rng knh, u tin cho ng dng c nh. M chia thnh 5 khi 10MHz, khng qui nh c th v rng knh, cho php trin khai c TDD v FDD.

    i vi Vit Nam, y cng l mt bng tn c kh nng s c s dng trin khai WBA/WiMAX.

    Bng 5725-5850MHz (bng 5.8 GHz):

    WiMAX Forum quan tm bng tn ny v c nhiu nc cho php s dng khng cn cp php v vi cng sut ti cao hn so vi cc on bng tn khc trong di 5GHz (5125-5250MHz, 5250-5350MHz), vn thng c s dng cho cc ng dng trong nh.Nn bng tn ny thch hp trin khai WiMAX c nh, rng phn knh l 10MHz, phng thc song cng c s dng l TDD, khng c FDD.

    Bng di 1GHz:

    Vi cc tn s cng thp, sng v tuyn truyn lan cng xa, s trm gc cn s dng cng t, tc mc u t cho h thng thp i. V vy, WiMAX Forum cng

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    ang xem xt kh nng s dng cc bng tn di 1GHz, c bit l bng 700-800MHz.

    Hin nay, mt s nc ang thc hin vic chuyn i t truyn hnh tng t sang truyn hnh s, nn s gii phng c mt phn ph tn s dng cho WBA/WiMAX. V d, M cp on bng tn 699-741MHz trc y dng cho knh 52-59 UHF truyn hnh v xem xt cp tip bng 747-801MHz (knh 60-69 UHF truyn hnh).

    Vi Vit Nam, do c im c rt nhiu i truyn hnh a phng nn cc knh trong gii 470-806MHz dnh cho truyn hnh c s dng dy c cho cc h thng truyn hnh tng t. Hin cha c l trnh c th no chuyn i cc h thng truyn hnh tng t ny sang truyn hnh s, nn cha thy c kh nng c bng tn cp cho WBA/WiMAX y

    Tng kt

    Ton chng mt a ra ci nhn tng quan nht v mt s cng ngh mng truy nhp bng rng, nhng c th ca cc loi cng ngh truy nhp ny nhm to c s khch quan nh gi v la chn cng ngh ph hp trong chng 3.

    Chng ny cng trnh by r s khc bit ga hai m hnh ng dng WiMAX c nh v WiMAX di ng. Da vo nhng dc im khc nhau ca cc nh dng ny gip cc nh cung cp dch v trong tng hon cnh c th s la chn m hnh ph hp trong trin khai thc t .

    Vi nhng tm hiu s lc ta cng thy cng ngh WiMAX t ra c rt nhiu c tnh u vit trong vic trin khai dch v bng thng rng cho c thit b c nh, xch tay v di ng, thm ch n cc vng m vi cc cng ngh trc y l kh khn hoc khng th.

    Trong chng tip theo ta s tm hiu su hn v kin trc mng v cc k thut c s dng trong cng ngh WiMAX.

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    Chng 2

    Mng WiMAX

    2.1 M hnh cu trc h thng WiMAX [12]

    WiMAX gm 2 mt phng tham chiu l:

    - Mt phng qun l: l mt phng cha cc thc th qun tr mng nh qun l v tnh cc.

    - Mt phng truyn tin :Mt phng ny tng ng vi hai lp di ca m hnh OSI m bo cho vic truyn tin ga 2 trm trong 1 cuc kt ni v c tiu chun ho c th giao tip vi nhiu ng dng lp trn

    Hnh 7: M hnh cu trc ca WiMAX

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    2.2 Mt phng truyn tin:

    Mt phng ny gm 2 lp v c phn chia thnh 4 lp nh hn:

    - MAC o Lp con tip ng CS (Convergence

    Sublayer) o Lp con phn chung CPS (Common

    Part Sublayer) o Lp con bo mt PS (Privaci Sublayer)

    - PHY (physical)

    2.2.1 Lp con tip ng (hay lp con hi t dch v chuyn bit MAC_CS) [2]

    MAC CS nm trn MAC CPS v s dng thng qua MAC SAP, cc dch v c cung cp bi MAC CPS. Lp ny thc hin cc chc nng sau:

    - Nhn cc n v d liu giao thc (PDU) t lp cao hn - Thc hin phn loi cc PDU lp cao hn. - X l (nu cn) cc PDU lp cao hn trn c s phn loi. - Pht cc CS PDU n cc MAC SAP thch hp. - Nhn CS PDU t thc th cng cp.

    Hin nay, c hai chi tit k thut CS c cung cp l:ATM CS v Packet CS.

    Lp con hi t ATM, hay ATM CS l mt giao din logic kt hp cc dch v ATM khc nhau vi MAC CPS SAP. ATM CS nhn cc t bo ATM t lp ATM, thc hin phn loi v nu c cung cp PHS (nn tiu ti trng), sau pht cc CS PDU n MAC SAP ph hp.

    Lp con hi t gi hay Packet CS dnh cho cc dch v d liu dng gi v d nh Ethernet, PPP, IP v VLAN. Cc CS khc c th c h tr trong tng lai.

    Trong qu trnh gi thng tin.D liu t lp cao hn chuyn xung,lp CS c trch nhim pht cc MAC SDU n MAC SAP. MAC c trch nhim pht cc MAC SDU n cc MAC SAP ngang cp ph hp vi QoS, vic phn on, ghp ni, v cc chc nng truyn ti khc, kt hp vi cc c im lung dch v ca mt kt ni c th.

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    Vi qu trnh nhn tin.CS c trch nhim nhn MAC SDU t cc MAC SAP.sau khi s l nh phn loi,gii nn tiu v gi n thc th lp cao hn.

    2.2.2 Lp con phn chung (MAC CPS- common part sublayer)

    Phn li ca lp MAC IEEE 802.16 l MAC CPS, c nhim v l :

    - nh ngha tt c cc qun l kt ni, - Phn phi bng thng, yu cu v cp pht, th tc truy nhp h thng, - Lp lch ng ln, iu khin kt ni v ARQ. - Truyn thng gia CS v CPS c cc im truy nhp dch v MAC (MAC

    SAP) duy tr. Thit lp, thay i, xa kt ni v truyn ti d liu trn cc knh l bn chc nng c bn trong qu trnh truyn thng ti lp ny.

    a/ nh dng v phn loi MAC PDU

    Phn loi MAC PDU

    MAC PDU d liu

    - Tiu l tiu MAC chung vi HT=0. - Ti trng l cc MAC SDU, hay cc phn on l d liu t lp pha trn

    (cc CSPDU). c pht trn cc kt ni truyn ti.

    Cc MAC PDU qun l

    - Tiu l tiu MAC chung vi HT=0 - Ti trng l cc bn tin qun l MAC. c pht trn cc kt ni qun l.

    Cc MAC PDU yu cu bng thng (BW)

    - Tiu l tiu yu cu bng thng vi HT=1 - khng c ti trng.

    Tiu MAC chung

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    Cc trng trong tiu MAC chung c ngha nh sau:

    - CI (1 bit) CRC Indicator: Nu CI c gi tr l 1 c ngha CRC c tnh n trong PDU bng cch gn vo ti trng PDU sau khi mt m ha, nu c gi tr 0 ngha l khng c CRC.

    - CID (16 bit) Connection Identifier - EC (1 bit) Encryption Control: EC c gi tr bng 0 ngha l ti trng khng

    c mt m ha.EC c gi tr 1 ngha l ti trng c mt m ha. - EKS (2 bit) Encryption Key Sequence Ch mc ca kha mt m ha lu

    lng (TEK) v vector khi to c s dng mt m ha ti trng. Trng ny ch c ngha nu trng EC c thit lp l 1.

    - HCS (8 bit) Header Check Sequence: Mt trng 8 bit c s dng pht hin li trong tiu . My pht s tnh ton gi tr HCS cho cc byte u tin ca tiu t bo v chn kt qu vo trng HCS (byte cui cng ca tiu ). N s l s d ca php chia (modulo 2) bi a thc c trng g (D=D8+D2+D+1) ca a thc D8 nhn vi ni dung ca tiu tr trng HCS.

    - HT (1bit) Header Type: HT c thit lp l 0. - LEN (11bit) Length- Trng di theo byte ca MAC PDU bao gm tiu

    MAC v CRC (nu c). - Type (6 bit) - Trng ny cho bit cc tiu con v cc loi ti trng c

    bit trong ti trng ca bn tin.

    Tiu yu cu bng thng

    PDU yu cu bng thng s ch c tiu yu cu bng thng v khng cha ti trng.Yu cu bng thng s c cc c tnh sau:

    - di ca tiu s lun l 6 byte. - Trng EC s c thit lp l 0, ch th khng mt m ha. - CID s cho bit kt ni cho SS yu cu bng thng ng ln. - Trng BR (Bandwidth Request) s cho bit s cc byte c yu cu.

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    - Cc loi yu cu bng thng c cho php l 000 cho tng dn v 001 cho ton b.

    Mt SS nhn mt tiu yu cu bng thng trn ng xung s hy b PDU.Mi tiu c m ha, bt u vi cc trng HT v EC. M ha cc trng ny l byte u tin ca tiu MAC s khng bao gi c gi tr 0xFF. iu ny ngn chn li pht hin cc byte m.

    Cc trng tiu yu cu bng thng:

    - BR (19 bit)- S lng cc byte ca bng thng ng ln c yu cu bi SS. Yu cu bng thng l cho CID. Yu cu s khng bao gm bt k mo u PHY no.

    - CID (16 bit) nhn dng kt ni - HT c gi tr l 1 - Type ( 3 bit) - Ch th loi tiu yu cu bng thng.

    Cc kt ni qun l MAC

    C 4 loi kt ni qun l.:

    Kt ni c bn: Cc bn tin qun l MAC khn cp v thi gian v ngn.Cc bn tin qun l MAC nh yu cu hy, thit lp ARQ...

    Kt ni qun l s cp :Cc bn tin qun l dung sai tr ln hn v di hn.Cc bn tin qun l MAC nh qun l kha bo mt, yu cu thay i dch v...

    Kt ni qung b : Cc bn tin qun l MAC nh miu t knh, DL-MAP, UL-MAP...

    Kt ni qun l Initial Ranging :Cc bn tin qun l yu cu Ranging.

    nh dng bn tin qun l MAC

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    Bn tin qun l MAC c th c gi trn cc kt ni c bn, cc kt ni s cp, kt ni qung b v cc kt ni Initial Ranging.

    Lc m ha TLV (type/ length/ value) c s dng trong bn tin qun l MAC v d nh trong bn tin UCD (miu t knh ng ln) cho trng thi burst ng ln.

    ( type=1, length=1, value=1)-> iu ch QPSK. ( type=1, length=1, value=2)-> iu ch 16-QAM. ( type=1, length=1, value=3)-> iu ch 64-QAM.

    b\Truyn cc MAC PDU

    Cc MAC PDU c truyn trong cc burst. Cc burst PHY c th cha nhiu khi FEC. Cc MAC PDU c th ko di qua cc ng bin khi. Qu trnh truyn gm cc bc sau:

    - Ghp ni - Phn on - ng gi - Tnh CRC - m

    Quy c Cc trng ca bn tin MAC s c pht theo th t nh xut hin trong cc

    bng trn.Cc trng ca bn tin MAC v cc trng ca TLV, c ch ra l cc s nh phn (bao gm CRC v HSC) s c pht nh mt chui cc digit nh phn ca chng, bt u t MSB.

    Cc mt n bit (v d nh trong ARQ) c xem nh cc trng s. Cc s MSB nh du c nh v lm du.

    Trng di trong dng xc nh ca ITU-T X.690 cng c xem nh mt trng s. Cc trng c ch th nh cc SDU hay phn on SDU (v d ti trng MAC PDU) c pht theo th t cc byteb nh nhn c t lp trn.

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    Cc trng ch th nh cc chui cng c pht theo th t cc symbol trong chui.Trong trng hp 3 v 4, cc bit trong mt byte c pht theo nguyn tc MSB trc.

    Bc 1:Ghp ni MAC PDU

    C nhiu MAC PDU c ghp ni trong cng mt burst PHY. Cc MAC PDU c th c ghp trong mt lung truyn dn n ng ln hoc ng xung. Do mi MAC PDU c nhn dng bi mt CID, thc th MAC nhn c th to ra MAC SDU (sau khi lp rp MAC SDU t mt hay nhiu MAC PDU nhn) n trng hp chnh xc ca MAC SAP. Cc bn tin qun l MAC, d liu ngi dng, v cc MAC PDU yu cu bng tn c th c ghp vo cng mt lung truyn dn.

    Hnh 8 :Ghp ni MAC_PDU

    Bc 2:Phn on MAC PDU

    Mi MAC SDU c th c phn on thnh nhiu phn on, mi phn on c ng gi thnh mt MAC PDU. Qu trnh ny c m bo cho php s dng bng tn c sn hiu qu lin quan n cc yu cu QoS ca mi lung dch v ca mt kt ni. Kh nng phn on v lp rp l bt buc.

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    tin cy ca lu lng phn on trn mt kt ni c nh ngha khi kt ni c to ra bi MAC SAP. Vic phn on c th c khi to bi BS cho cc kt ni ng xung v bi SS cho cc kt ni ng ln.

    Cc kt ni khng ARQ: vi cc kt ni khng ARQ, cc phn on c pht ch mt ln v theo tun t. S tun t c gn cho mi phn on cho php u thu ti to li ti trng ban u v pht hin mt bt k gi no ngay lp tc. Mt kt ni c th ch c mt trng thi phn on mt thi gian bt k cho trc

    Cc kt ni ARQ: vi cc kt ni ARQ, phn on c nh dng cho mi lung truyn dn bng cch ghp mt tp hp cc khi ARQ vi cc s tun t lin nhau.Gi tr BSN trong tiu con phn on l BSN cho khi ARQ u tin xut hin trong phn on. FSH l tiu con phn on c di 8 bit.

    Hnh 9: Phn on MAC_PDU Bc 3 :ng gi cc MAC PDU

    ng gi c thc hin trn mi kt ni, MAC c th gi nhiu MAC SDU vo mt MAC PDU n. ng gi to ra vic s dng ch s thuc tnh kt ni l kt ni mang cc gi c di thay i hay di c nh. Pha pht hon ton ch ng trong vic ng gi hay khng mt nhm cc MAC SDU trong mt MAC PDU n. Kh nng khng ng gi l bt buc.

    Cu trc ca cc PDU thay i vi cc kt ni ARQ v khng ARQ vi cc c php phn on v ng gi c th.

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    Vi cc kt ni khng s dng ARQ: ng gi cc khi c di c nh, iu khon Request/ Transmission c thit lp cho php ng gi v cm phn oan,v kch c SDU s c bao gm trong bn tin DSA-REQ khi thit lp kt ni. Trng di tiu MAC biu th s cc MAC SDU c gi trong mt MAC PDU n. Nu kch c MAC SDU l n byte, pha thu c th m gi bi bit rng trng di trong tiu MAC s l (nk+j) vi k l s MAC SDU c ng gi trong MAC PDU v j l kch c tiu MAC. Mt MAC PDU cha mt chui cc MAC SDU c gi. Khng c thm tiu do ng gi trong trng hp MAC SDU di c nh v mt MAC SDU n th n gin l mt chui c gi c di l 1.

    Khi ng gi cc kt ni MAC SDU di thay i, MAC gn mt tiu con gi (PSH) cho mi MAC SDU. Mt MAC PDU bao gm mt chui cc MAC SDU di thay i c ng gi. Nu c hn mt MAC SDU c ng gi, trng Type trong tiu MAC ch th s c mt ca cc PSH. Khi mt PSH c mt, thng tin phn on cho cc MAC SDU c th hay cc phn on MAC SDU c cha trong PSH tng ng. Nu khng c PSH, thng tin phn on cho cc phn on MAC SDU c th c cha trong tiu con phn on (FSH) tng ng.

    Vi cc kt ni cho php ARQ: S dng PSH cho mi kt ni tng t nh trn, ngoi tr cc kt ni ARQ s thit lp bit Extended Type trong tiu MAC chung. Nu ng gi c thc hin cho mt kt ni, MAC c th gi nhiu MAC SDU vo trong mt MAC PDU n. Gi cc MAC SDU c di thay i cho cc kt ni cho php ARQ tng t cc kt ni khng ARQ khi phn on c cho php. BSSN ca PSH s c dng bi giao thc ARQ nhn dng v pht li cc phn on mt. Khi trng Type ch th rng PSH c dng, thng tin phn on cho mi MAC SDU c th hay phn on MAC SDU c cha trong PSH kt hp. Khi PSH khng c dng, thng tin phn on cho mi ti trng ca MAC PDU (MAC SDU hay phn on MAC SDU) c cha trong FSH.

    Mt MAC SDU c th c chia thnh nhiu phn on v sau c gi trong cng mt MAC PDU cho ln truyn u tin. Cc MAC PDU c th c cc phn on t cng mt SDU hay cc SDU khc nhau, bao gm s trn ln gia ln truyn u tin v ln truyn li. Cc trng BSN (11 bit) v FC (2 bit) nhn dng mi SDU phn on hay SDU khng c phn on.

    Khi ng gi cc MAC SDU kch c c nh th khng cn thit cc tiu con gi. Cc MAC SDU loi ny v d nh cc t bo ATM trn cng mt kt ni.

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    Cc MAC SDU kch c thay i v d nh cc gi IP trn cng mt kt ni. Khi ng gi chng cn phi c tiu con gi PSH c di 16 bt.

    Bc 4:Tnh CRC

    Mt lung dch v c th yu cu CRC thm vo mi MAC PDU mang d liu cho lung dch v . Trong trng hp ny vi HT=0, mt CRC s c gn vo ti trng MAC PDU. CRC s kim sot tiu MAC chung v ti trng MAC PDU. CRC s uc tnh ton sau khi mt m ha chng hn CRC bo v tiu chung v mt m ha ti trng.

    Mt m ha cc MAC PDU

    Khi pht mt MAC PDU trn mt kt ni c nh x n mt SA, pha gi s thc hin mt m ha v nhn thc d liu ca ti trng MAC PDU khi c ch th bi SA. Khi nhn mt MAC PDU trn mt kt ni c nh x n mt SA, u thu s thc hin gii mt m v nhn thc d liu ca ti trng MAC khi c ch th bi SA.

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    Tiu MAC chung s khng c mt m ha. Tiu cha tt c thng tin mt m ha (trng EC, trng s tun t kha mt m EKS v CID) cn gii mt m mt ti trng trm thu.

    Hai bit ca tiu MAC cha mt s tun t kha. Kha kt hp vi mt SA c thi gian sng hn ch v BS theo nh k lm mi kha ca SA. BS qun l 2 bit s tun t kha c lp vi mi SA v phn phi s tun t kha ny cho mi ln to ra kha mi. Tiu MAC bao gm s tun t nhn dng vic to c th mt kha SA c s dng mt m ha ti trng c gn. L mt con s 2 bit, s tun t t 0 n 3.

    So snh s tun t kha ca MAC PDU nhn vi ci m n tin tng l s tun t kha hin hnh, BS hay SS c th d dng nhn ra mt ng b kha. Mt SS s duy tr hai kha mi nht cho mi SA. Gi hai kha ny l cn thit duy tr cho dch v khng ngt qung trong khi chuyn tip kha ca SA.

    Mt m ha ti trng c ch th bi trng bit EC. Gi tr 1 cho bit ti trng c mt m ha v trng EKS cha d liu c ngha. Gi tr 0 cho bit ti trng khng c mt m ha. Bt k MAC PDU no cha m ha c nhn trn mt kt ni nh x n mt SA yu cu mt m ha th d liu s b loi b.

    Bc 5 :m

    Khng gian c n nh trong mt burst d liu m cha c s dng s c khi to cho mt trng thi c nhn bit. iu ny c th c hon thnh bng cch thit lp mi byte cha dng thnh mt gi tr byte m (0xFF). Nu kch c vng cha s dng t nht l kch c ca tiu MAC, vng ny cng c th c khi to bng cch nh dng khng gian cha s dng mt MAC PDU. Khi lm vic , trng CID tiu MAC s c thit lp gi tr ca CID m, cc trng Type, CI, EC, HT s c thit lp l 0, trng di s c thit lp s byte cha s dng (bao gm c kch c tiu MAC to ra cho MAC PDU m) trong burst d liu v HCS s c tnh ton theo cch thng thng.

    c\ Mt s k thut trong lp MAC_SAP

    K thut ARQ:

    K thut ARQ dng truyn li cc khung b li khng sa c bi FEC. Khi c b sung, ARQ c th c cho php trn mi kt ni. Mi kt ni ARQ s c nh r v thng lng trong khi to kt ni. Mt kt ni khng th c s pha trn gia lu lng ARQ v khng ARQ.

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    Vi cc kt ni ARQ, cho php phn on l ty chn. Khi phn on c cho php, u pht c th phn chia mi SDU thnh nhiu phn on truyn dn ring bit da trn gi tr ca tham s ARQ_BLOCK_SIZE. Khi vic phn on khng c php, kt ni s c qun l ging nh khi c php. Trong trng hp ny, lin quan n kch c khi tha thun, mi phn on c nh dng truyn dn s cha tt c cc khi d liu kt hp vi SDU gc.

    K thut ny cho php tng tin cyh ca dch v nhng ng thi gim dung lng ng truyn v tng thi gian tr

    K thut yu cu v cp pht bng tn

    thc hin qu trnh yu cu v cp pht bng tn s c cc qu trnh nh polling yu cu v cp pht:

    Phn Polling:

    Polling l qu trnh c s dng bi BS cp pht cc c hi yu cu bng tn cho cc SS. Khi BS mun thng bo cho mt SS mt c hi yu cu bng tn ang n, n s s dng mt phn t thng tin IE bn tin UL-MAP lm vic . UL- MAP IE s chp nhn bng tn cho SS hay cc SS xem xt cc yu cu bng tn ca chng trong chu k yu cu theo l thuyt. Cp pht c hi yu cu bng tn s c thc hin trn c s n im, a im, hay qung b.

    Polling n im :Trong trng hp ny, mt SS c kim sot vng mt cch ring bit bi BS. SS s tr li vi cc byte trn nu bng tn c cp l khng cn thit.

    Polling a im v qung b: BS s s dng n kim sot vng a im hay qung b n cc SS nu bng tn ang sn c khng kim sot nhiu SS mt cch ring bit. Cc CID bt k c d tr cho cc nhm a im v cho cc bn tin qung b. Kim sot vng a im hay qung b cng c thc hin qua bn tin UL-MAP trong cng mt kiu vi polling n im. S khc bit c bn y l bn tin polling c nh hng n mt CID a im hay qung b thay v CID c th hoc SS.

    Poll-me bit: Poll-me bit c s dng bi cc SS s dng dch v UGS thng bo cho BS rng chng cn c kim sot vng. Poll-me bit l mt phn ca tiu con qun l cp pht. Khi poll-me bit c pht hin, BS s s dng mt polling n im n SS yu cu n. gim thiu nguy c BS lm mt Poll-me bit, SS c th thit lp bit trong tt c tiu con qun l cp pht MAC UGS khong thi gian lp lch ng ln.

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    Phn Yu cu:

    l k thut m cc SS s dng thng bo cho BS rng n cn c cp pht bng tn ng ln. Mt yu cu c th n nh mt tiu yu cu bng tn ng mt mnh hoc c th n nh mt PiggyBack Request.

    Bi v profile burst ng ln c th thay i linh ng, nn tt c cc yu cu bng tn s c to thnh s hng ca s cc byte cn mang tiu v ti trng MAC, nhng khng tnh lp vt l. Bn tin yu cu bng tn c th c pht trong bt k thi im no ng ln ngoi tr trong khong thi gian Initial Ranging.

    Bandwidth Request Header: SS c th yu cu cp pht bng tn vo bt k thi im no bng cch gi mt MAC PDU yu cu bng tn vi mt tiu yu cu bng tn v khng c ti trng. Tiu yu cu bng tn c s dng yu cu thm bng tn.

    Piggyback Request : Phng php thng dng yu cu bng tn s dng mt tiu con qun l cp pht mang mt yu cu cho bng tn thm vo cho cng mt kt ni trong MAC PDU. Mang mt bn tin BW Request trn mt gi d liu.

    Yu cu bng tn c th l tng dn hoc ton b. Khi BS nhn mt yu cu bng tn tng dn, n s ghi nh s lng bng tn c yu cu hin thi ca kt ni. Trng Type trong tiu yu cu bng tn cho bit yu cu l tng dn hay ton b. Do PiggyBack Request khng c trng Type, nn n s lun l tng dn.

    Phn Cp pht

    Cp pht trn mi kt ni (GPC): SS ch nhn cc cp pht cho cc kt ni c th (bao gm c cc kt ni qun l) v kt qu phi yu cu bng tn cho mi kt ni c th khi c nhu cu. Hn na, SS phi yu cu thm bng tn p ng cc yu cu ca RLC khng c mong i. V th, cc h thng GPC l n gin nhng khng hiu qu. Vic cp pht c quyt nh da trn bng tn yu cu v cc yu cu QoS v ti nguyn sn c.

    Cp pht trn mi trm thu bao (GPSS): SS nhn mt cp pht bng tn c s dng p ng cc nhu cu ca tt c cc kt ni ca n. T SS phi qun l bao nhiu bng tn c cp pht cho mi kt ni. Nu mt kt ni yu cu nhiu hn bng tn c th phc v, SS c th ly cp bng tn t mt kt ni khc lp y lng bng tn cn thiu. BS cng m nhn hng i u tin trn c s cc loi lu lng. SS sau c th gi mt yu cu n BS yu cu tng thm bng tn nhm p ng cc nhu cu mi ca n.

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    Cc cp pht bng tn c cung cp trn c s giao thc t hiu chnh tri ngc vi giao thc bit trn. Trong giao thc ny, nu SS khng nhn mt cp pht bng tn tr li yu cu bng tn ca n, SS s tha nhn rng yu cu b mt hay tr li khng c tha mn, v n gin s gi mt yu cu khc n BS m khng i mt s xc nhn ca yu cu ban u. Giao thc ny b qua tiu kt hp vi cc bn tin xc nhn.

    K thut dch v lp lch ng ln

    Cht lng dch v ni n kh nng cung cp u tin cho cc dch v khc nhau ca mng. Cc tham s chnh ca QoS trong mng bao gm rng bng tn chuyn dng, gc tr, jitter v t l mt. C nhiu dch v vi QoS khc nhau, iu ny c ngha l cc dch v khc nhau c cp pht cc ti nguyn khc nhau v cht lng dch v m bo. Phn loi dch v ng ln da trn cc yu cu khc nhau v bng tn, gc tr v jitter.

    Dch v cp pht khng yu cu (UGS) :Ti nguyn v tuyn ng ln c cp pht mt khong thi gian nh k. B lp lch BS a ra bng tn ng ln kch c c nh chp nhn c s thi gian thc theo chu k.Dch v UGS c thit k cho cc lung lu lng thi gian thc m pht cc gi d liu kch c c nh trn nn tng nh k nh T1/E1 v VoIP. Dch v kim sot vng thi gian thc (rtPS)

    Dch v ny cung cp cc c hi yu cu truyn dn ng ln cc khong thi gian c nh. Theo cch ny, ti nguyn trc ht phi c yu cu v sau c cp pht bi im truy nhp. Thng tin v cc ngun ti nguyn c cp pht trong ng ln l qung b thng qua ng xung n tt c cc u cui ngi dng. Dch v rtPS c dnh cho cc lung lu lng thi gian thc m pht cc gi d liu kch c thay i trn nn tng nh k nh l video MPEG. B lp lch BS a ra cc c hi yu cu bng tn ng ln theo nh k, thi gian thc. SS s dng c hi yu cu UL-BW a ra ch nh vic chp nhn UL-BW c mong mun. SS khng th s dng yu cu BW trn c s tranh chp.

    Dch v kim sot vng phi thi gian thc (nrtPS):Dch v ny cung cp k thut lp lch ng ln ging nh rtPS m khng thm d gc tr thp. Ph hp nht vi cc lung lu lng phi thi gian thc yu cu d liu kch c thay i chp nhn trn nn tng cch u nhau nh l FTP rng di tn cao. Cho cc dch v nrt-VBR nh truyn tp, cn nhiu rng di tn. B lp lch BS s cung cp cc c hi yu cu UL-BW theo thi gian (khong 1s hay t hn). SS c th s dng cc c hi yu cu BW trn c s tranh chp gi yu cu BW.

    Dch v Best Effort (BE):Vi dch v ny, cc khong thi gian yu cu tranh chp, cc c hi yu cu n im hay cc loi burst chp nhn d liu c th

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    c cp pht. Trong cch ny, cc yu cu ti nguyn c th tranh chp ch trong khi kt ni ang xy ra. Cc gi d liu c pht qua cc ti nguyn c dnh ring theo cc yu cu ti nguyn bi b lp lch ng ln trong im truy nhp. Cho lu lng best-effort v d nh HTTP, SMTP. SS s dng cc c hi yu cu BW trn c s tranh chp.

    2.2.3 Lp MAC_PS [2]

    Hai chc nng chnh: - Bo mt qua cc khng gian truyn dn. - Bo v khi cc nh cp dch v.

    Lp con bo mt thc hin m ha d liu trc khi truyn i v gii m d liu nhn c t lp vt l. N cng thc hin nhn thc v trao i kha bo mt.

    Chun IEEE 802.16 ban u s dng phng php DES 56 bit cho m ha lu lng d liu v phng php m ha 3-DES cho qu trnh trao i kha. Trong mng IEEE 802.16, trm gc cha 48 bit ID nhn dng trm gc (ch rng y khng phi l mt a ch MAC), cn SS c 48 bit a ch MAC 802.3.

    C 2 giao thc chnh hot ng trong lp con bo mt: giao thc m ha d liu thng qua mng bng rng khng dy, v giao thc qun l kha bo v bo mt (PKM- Privacy and Key Management Protocol) m bo an ton cho qu trnh phn phi kha t BS ti SS. N cng cho php BS t iu kin truy nhp cho cc dch v mng. Giao thc PKM s dng thut ton kha cng khai RSA, chng thc s X.509 v thut ton m ha mnh thc hin trao i kha gia SS v BS. Giao thc bo mt ny da trn giao thc PKM ca DOCSIS BPI+ c ci tin cung cp mt lc m ha mnh hn nh chun m ha ci tin AES.

    MAC trong IEEE 802.16 l phn lp hng kt ni, c thit k cho cc ng dng truy nhp khng dy bng rng theo cu hnh im a im (PMP), hay dng mesh. C hai loi kt ni MAC c xc nh bi 16 bit nhn dng kt ni CID l: Cc kt ni qun l v Cc kt ni vn chuyn d liu. Cc kt ni qun l li gm 3 loi:

    - c s, - s cp - th cp

    Trong c s s dng cho truyn ti, iu khin lin kt v tuyn...,cn s cp lin quan n thit lp nhn thc v kt ni, v kt ni qun l th cp l cc bn tin qun l da trn chun truyn ti nh DHCP, TFTP, SNMP. Kt ni qun l s cp v kt ni c s c to ra khi mt MS/SS ra nhp vo mt BS phc v ca

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    mng. Kt ni vn chuyn d liu c th c thit lp da trn nhu cu. Chng c s dng cho cc lung lu lng ngi s dng, cc dch v n hng (Unicast) v a hng (Multicast). Cc knh b sung cng c MAC d tr gi ra ngoi cc thng tin lp lch ng xung v ng ln.

    Cc thnh phn c bn ca mng l trm gc BS v trm thu bao SS (Subscriber Station), trm gc BS ging nh cc im truy nhp (AP) trong mng WiFi. BS c ni vi phn hu tuyn, n pht qung b cc thng tin ti SS. Khc vi phng php CSMA/CA trong 802.11, 802.16 s dng cc nh x ng xung v ng ln khc phc xung t trong mi trng truy nhp. SS s dng phng thc truy nhp TDMA chia s ng ln trong khi BS s dng phng thc TDM. Tt c cc chc nng ny c thc hin thng qua bn tin DL_MAP v UL_MAP.

    2.2.4 c im lp MAC ca WiMAX

    a/ QoS

    im ni bt trong kin trc MAC trong IEEE 802.16 l QoS.Ging nh mi h thng h tr QoS khc, vic phn loi dch v cng l im ct li trong vic m bo QoS. Xem cc loi hnh dch v QoS trong bng di y:

    QoS ph thuc vo 3 yu t sau:

    - Giao thc MAC hot ng hng kt ni (connection oriented). Mi mt gi tin u c a vo mt kt ni c th, kt ni ny l kt ni o, c xc nh bi tham s CID. Vic to nn cc kt ni o ny khin cc gi tin c gi i mt cch hiu qu v nhanh chng.

    - C ch cp pht bng thng Request/Grant: C ch ny lm tng hiu qu s dng bng thng ca h thng, c bit l cc h thng m c nhiu thu bao. Trong c ch ny, MS yu cu thng lng bng thng cp pht t BS thng qua mt s cc phng thc khc nhau. BS s cp pht bng thng bng cch cp pht cc timeslot ti cc MS c yu cu.

    - C ch lp lch (scheduling) trong WiMAX khng c qui nh c th trong chun. C nhiu hnh thc lp lch khc nhau, mc ch l lm th no s dng ti nguyn UL va DL mt cch c hiu qu nht trong khi lun m bo c QoS yu cu.

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    Bng 6: Dch v QoS

    Yu cu QoS ng dng c tnh k thut Dch v cho php t nguyn (Unsolicited Grant Service-UGS)

    VoIP

    - Tc duy tr ti a - Dung sai tr ti a - Dung sai jitter

    Dch v thi gian thc(Real time Polling service-rtPS)

    Lung audio hoc video

    - Tc knh dnh ring ti thiu

    - Tc duy tr ti a - Dung sai tr ti a - u tin lu lng

    Dch v thi gian m rng (Extnded Real time Polling service-ErtPS)

    Thoi vi d tm hot ng

    - Tc knh dnh ring ti thiu

    - Tc duy tr ti a - Dung sai tr ti a - Dung sai jitter - u tin lu lng

    Dch v khng theo thi gian thc (Non Real time Polling service-nrtPS)

    Giao thc truyn file (FTP)

    - Tc dnh ring ti thiu - Tc Tc duy tr ti a - u tin lu lng

    Dch v tt nht(Best Effort Service -BE)

    Truyn d liu, duyt Web

    - Tc duy tr ti a - u tin lu lng

    b/ iu khin cng sut

    WiMAX di ng h tr hai ch vn hnh l: Sleep Mode v Idle Mode tit kim nng lng tiu th.

    Sleep Mode l trng thi m MS trong giai on trc khi c bt c trao i thng tin g vi trm gc qua giao din v tuyn. Sleep Mode cho php MS ti thiu nng lng tiu th v ti thiu ti nguyn v tuyn ca trm gc. Sleep Mode cng cung cp kh nng linh hot cho MS d cc trm gc khc thu thp thng tin h tr chuyn giao trong Sleep Mode.

    Idle Mode cung cp mt c ch cho MS sn sng mt cch nh k nhn cc bn tin qung b DL m khng cn ng k vi mt trm gc xc nh no khi

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    MS di chuyn trong mt mi trng c ng truyn v tuyn c ph sng bi nhiu trm gc.

    c/ Qun l di ng

    C ba phng php chuyn giao c chun IEEE 802.16 h tr l :

    - Chuyn giao cng (Hard Handoff HHO), - Chuyn trm gc nhanh (Fast Base Station Switching FBSS) - Chuyn giao phn tp v m (Macro Diversity Handover MDHO)

    Trong , chuyn giao HHO l bt buc cn FBSS v MDHO l hai ch ty chn.

    Cng ging ging nh chuyn giao nhanh (FBSS hay MDHO) trong h thng CDMA, chuyn giao nhanh trong WiMAX cng ch c th thc hin gia cc BS nm trong ci gi l Diversity Set (tp hp cc BS hot ng trong cng tn s, c SINR ln MS c th kt ni c v c bit l chng phi ng b (synchronisation)). Trong Diversity Set ny th ch c 1 ci BS c gi l anchor (ci BS ch lc, hay cn gi l im kt ni, khp ). S khc nhau gia MDHO v FBSS l ch: i vi FBSS, MS ch communicate thng tin data thng qua BS anchor thi, cn MDHO th MS communicate thng tin data traffic qua tt c cc BS nm trong Diversity Set.

    d/ Bo mt

    WiMAX h tr tt nht cc c tnh bo mt lp nh p dng cc cng ngh tt nht ang sn c hin nay. N h tr nhn thc gia thit b/ngi dng, giao thc qun l kha linh ng, m ha lu lng, bo v bn tin iu khin v ti u ha giao thc bo mt cho cc chuyn giao nhanh.

    Giao thc qun l kha: Giao thc qun l kha v bo mt phin bn 2 (Privacy and Key Management Protocol Version 2 PKMv2) l mt trong nhng khi nim bo mt c bn ca WiMAX di ng. Giao thc ny qun l bo mt MAC s dng bn tin PKM REQ/RSP. Nhn thc PKM EAP, iu khin m ha lu lng, trao i kha chuyn giao v cc bn tin bo mt Mutilcast/Broadcast u da trn giao thc ny.

    Nhn thc thit b/ngi dng: WiMAX di ng h tr nhn thc thit b v ngi dng s dng giao thc IETF EAP bng cch cung cp h tr credentials c da trn SIM, hoc da trn USIM hoc chng nhn s hoc da trn tn ngi s dng/mt khu.

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    M ha lu lng: AES-CCM l mt m ho c s dng bo v tt c s liu ngi s dng qua giao din WiMAX MAC di ng.

    Bo v cc bn tin iu khin: D liu iu khin c bo v bi AES da trn CMAC, hoc s HMAC da trn MD5.

    H tr chuyn giao nhanh: Mt s bt tay 3 bc c h tr bi WiMAX di ng ti u c ch nhn thc li cho h tr chuyn vng nhanh. C ch ny cng hu ch trong vic chng li vic tn cng gia chng ca hacker.

    e/ Dch v Muticast v Broadcast MBS

    Dch v MBS trong WiMAX di ng kt hp cc c tnh tt nht ca DVB H, MediaFLO v 3GPP E UTRA, tha mn nhng yu cu sau:

    - Tc d liu cao v kh nng ph sng s dng mng mt tn s (SFN Single Frequency Network)

    - Cp pht ti nguyn v tuyn linh ng. - MS tiu th nng lng thp. - H tr d liu ngang hng bao gm cc lung audio v video. - Thi gian chuyn mch knh nh.

    2.2.5 Lp vt l (PHY, physical layer)

    Ban u c t PHY c nh ngha cho 1066 GHz l :Truyn lan LOS (line-of-sight -tm nhn khng b vt cn),Kin trc im- a im,v S dng iu bin sng n mang. khc phc hn ch truyn LOS trong di 10-66 GHz,Lp vt l 211 GHz c thit k do nhu cu theo hng hot ng NLOS (non-line-of-sight) v mi c t u a ra tnh hot ng cng nhau.

    V c bn, BS truyn mt tn hiu TDM vi nhng trm thu bao ring l c nh v nhng khe thi gian theo chu k. S truy cp theo hng ng ln cho bi TDMA. Tip theo nhng tho lun m rng v duplexing, mt thit k burst c chn cho php c TDD (timedivision duplexing), ti ng ln v ng xung dng chung mt knh nhng khng truyn cng lc v FDD (frequency-division duplexing), ti ng ln v ng xung hot ng trong nhng knh ring bit. Thit k burst ny cho php c TDD ln FDD c x l theo cch tng t. Nhng la chn mt trong hai TDD v FDD h tr nhng burst thch ng, trong nhng ty chn iu bin v m ha c th c gn ng trn c s tng burst mt.

    a\ nh dng khung

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    c t PHY c nh ngha cho 1066 GHz s dng iu bin sng mng n dng burst vi burst-profiling thch ng, nhng tham s truyn, bao gm cc k hoch iu bin v m ha, c th c iu chnh ring cho mi trm thu bao (subscriber station, SS) trn c s tng khung (frame) mt.

    H thng s dng mt khung 0.5, 1 hoc 2 ms. Khung ny c chia ra thnh nhng khe vt l cho mc ch cp pht v nhn bit di thng thuc cc chuyn tip PHY.

    Mt khe vt l c nh ngha cho 4 k hiu QAM (quadrature amplitude modulation). Trong phng n TDD ca PHY, khung con ca ng ln k tip theo khung con ca ng xung trong cng mt tn s sng mang. Trong phng n FDD, cc khung con ca ng ln v ng xung cui cng cng trng khp nhng chng c mang trn nhng tn s ring bit.

    Khung con ca ng xung bt u vi mt on iu khin khung c cha DL-MAP cho khung ng xung hin hnh cng nh UL-MAP cho thi gian nh r trong tng lai. Khung con ng xung c cha mt TDM-portion (on TDM) ngay tip theo on iu khin khung. D liu ng xung c truyn ti mi SS khi s dng mt burst-profile tha thun.

    Mo u khi u khung l dy 32 k hiu c to ra bng lp mt dy 16 k hiu .Khung iu khin chc nng c s dng chuyn thong tin iu kim cho knh ti tt c cc SS,v d liu ny khng c bo mt.

    Trong cc h thng, sau on TDM l mt on TDMA c cha mt on m du (preamble) ph ti im xut pht ca mi burst-profile mi. c tnh ny cho php h tr tt hn cc SS bn song cng.

    Trong mt h thng FDD c hoch nh hiu qu vi nhiu SS bn song cng, mt s c th truyn sm hn trong khung hn l chng nhn. V bn cht bn song cng, cc SS ny mt s ng b ha vi ng xung. TDMA-preamble cho php chng ly li s ng b ha .

    Type PHY Synchronization

    DCD Count

    BS_ID low BS_ID high Element count

    Khun dng thng ip DL_MAP

    - Type(8 bit) :kiu thng ip qun tr.c gi tr mc nh l 2. - PHY Synchronization (32 bit):trng ng b vt l - DCD Count (8 bit) :b m DCD - Base station _ID low (32bit) :m nhn dng BS thp

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    - Base station _ID high (16bit) :m nhn dng BS cao - Element count (16 bit) s lng phn t DL_MAP

    DL-MAP ca on iu khin khung cung cp ti cc SS cc c tuyn cu ng xung. lun c th ng dng cho khung hin thi v lun c di ti thiu l hai block FEC. S chuyn tip PHY u tin c biu th trong block FEC u tin, cho php thi gian x l thch ng. Trong c hai h thng TDD v FDD, UL-MAP cung cp cc nh v bt u khng mun hn khung ng xung tip theo. Tuy vy, UL-MAP c th nh v s khi u khung hin thi min l nhng thi gian x l v nhng tr ton phn (round-trip delay) phi c gim st.

    Type DL Ch_ID CCC PTR

    Khun dng thng ip DCD

    - Type: (8 bit) kiu thng ip qun tr c gi tr =1 - DL Ch_ID : Downlink Channel ID (8 bit) ch th knh ng xung - CCC (8 bit) :b m thay i cu hnh - PTR (16 bt):trng con tr nh dng cu trc c trng vt l cho knh

    ng xung.

    DCD l thng ip m t knh ng xung .mt b nhn dng BS 48 bit c th lp trnh trong DL_MAP. B nhn dng ny v DCD dng nhn dng knh ,c s dng trong trng hp khi SS nm trn ng bao vng ph sng.

    Type UL Ch_ID UCD count

    Element count

    Allocation start time

    Khun dng thng ip DL_MAP

    - Type: (8 bit) kiu thng ip qun tr c gi tr =3 - UL Ch_ID : Uplink Channel ID (8 bit) ch th knh ng ln - UCD count: (8 bit) b m UDC - Element count: (16 bit) s lng phn t UL_MAP - Allocation start time(32 bit) :thi im bt u phn phi

    Khun dng thng ip UCD Type UL Ch_ID CCC RngBS RngBE ReqBS ReqBE PHY_Ptr List_Ptr

    - Type: (8 bit) kiu thng ip qun tr c gi tr =0

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    - UL Ch_ID : Uplink Channel ID (8 bit) ch th knh ng ln - CCC (8 bit) :b m thay i cu hnh - RngBS (8bit) im bt u sp xp - RngBE (8bit) im kt thc sp xp - ReqBS (8bit) im bt u gi yu cu - ReqBE (8bit) im kt thcgi yu cu - PHY_Ptr (16 bt):trng con tr nh dng cu trc c trng vt l cho knh

    ng xung. - List_Ptr (16 bt):trng m t kiu con tr nh dng cc loi burst.

    UDC c s dng cung cp cho cc SS thng tin v yu cu c ch cum ng ln.Thng tin UL_MAP nhn c bng vic s dng b nhn dng kt ni CID. Thng ip ny cung cp mt m s dng xung nhp ng ln UIUC c SS s dng truyn ln. Thng ip UL_MAP v UCD c m t nh hnh trn.

    Khung con ng ln

    Khng ging nh ng xung, UL-MAP cp gii thng cho cc SS c th. Cc SS truyn trong vng cp pht c n nh c s dng burst-profile ch r bi UIUC (Uplink Interval Usage Code) trong mc vo (entry) UL-MAP cp di thng cho chng. Khung con ng ln c th cng cha nhng nh v trn c s cnh tranh cho truy nhp h thng lc ban u v broadcast hay multicast cc yu cu di thng. Nhng c hi truy cp cho truy nhp h thng lc ban u c xc nh ln cho php thm thi gian bo v cc SS m chng khng c gii quyt thi gian truyn cn thit b li tr ton phn (round-trip delay) cho BS.

    C 3 loi cm c th hin din trong bt k khung con ng ln no :

    - Cm tranh chp :da trn duy tr ban u hoc cc c hi truy nhp ban u - Cm tranh chp da trn c hi mc dnh bng khong thi gian yu cu

    p ng truyn a hng hoc vng qung b - Khng tranh chp da trn nh v khong thi gian c sp xp ti SS c

    bit trong UL_MAP m bo bng thng t BS

    Cc cm trn u c th c trong bt k khung no.Khng ging nh UL_MAP cp bng thng cho cc SS c th. Khung con ng ln c th cha cc nh v trn c s tranh chp cho truy nhp h thng lc ban u.

    b\Lp con hi t truyn TC (transmission convergence). Gia PHY v MAC l mt lp con hi t truyn TC (transmission

    convergence). Lp ny thc hin s bin i cc PDU (protocol data units) MAC di c th thay i vo trong cc block FEC di c nh (cng thm c th l mt

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    block c rt ngn vo on cui) ca mi burst. Lp TC c mt PDU c kch thc khp vi block FEC hin thi b y. N bt u vi mt con tr ch ra v tr u mc PDU MAC tip theo bt u bn trong block FEC.

    Khun dng PDU_TC

    Khun dng PDU TC cho php ng b ha li PDU MAC tip sau trong trng hp block FEC trc c nhng li khng th phc hi c. Khng c lp TC, mt SS hay BS nhn s mt ton b phn cn li ca mt burst khi mt li khng th sa cha xut hin.

    2.2.6 Cc k thut truyn thng s trn lp PHY

    a/ OFDM (Orthogonal Frequency Division Multiplexing) hay ghp knh phn chia theo tn s trc giao l mt k thut iu ch a sng mang.

    K thut ny c th t c tc d liu rt cao, chng nhiu giao thoa k t - ISI (Inter symbol Interference) v gii quyt c vn tn hiu a ng.

    Cng ngh OFDM chia lung d liu thnh nhiu ng truyn bng hp trong vng tn s s dng cc sng mang con trc giao vi mt sng mang con khc. Nhng sng mang con ny sau ghp thnh cc knh tn s truyn v tuyn.

    OFDM khai thc s phn tp tn s ca knh a ng bng cch m ho v chn thng tin trn cc sng mang con trc khi truyn i. iu ch OFDM c th thc hin c vi bin i ngc Fourier nhanh - IFFT, php bin i ny cho php mt s lng ln cc sng mang con (ln ti 2048) vi phc tp thp. Trong mt h thng OFDM, ti nguyn sn c trong min thi gian chnh l cc symbol OFDM v trong min tn s chnh l cc sng mang con. Ti nguyn v thi gian v tn s c th c t chc thnh cc knh con (sub-channel) cp pht cho ngi dng.

    b/OFDMA (Orthogonal Frequency Division Multiple Access)- a truy nhp phn chia theo tn s trc giao l cng ngh a truy cp phn chia theo sng mang , v c pht trin da trn cng ngh OFDM.

    OFDMA cho php nhiu ngi dng cng truy cp vo mt knh truyn bng cch phn chia mt nhm cc sng mang con (subcarrier) cho mt ngi dng ti mt thi im. cc thi im khc nhau, nhm sng mang con cho 1 ngi dng

    P(con tr 1byte)

    Khi PDU u tin khi u trong TC ngay trc

    Khi PDU u tin khi u trong TC hin ti

    Khi PDU th 2 khi u trong TC hin ti

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    cng khc nhau. OFDMA c dng trong cng ngh mng 802.16e (WiMAX di ng),

    OFDMA h tr cc nhim v ca cc sng mang con i vi cc thu bao nht nh. Mi mt nhm sng mang con c biu th nh mt knh con (subchannel) v mi thu bao c ch nh mt hoc nhiu knh con truyn pht da trn mi yu cu c th lu lng ca mi thu bao

    OFDMA c mt s u im nh kh nng linh hot tng, thng lng v tnh n nh c ci tin. Bng vic n nh cc knh con cho cc thu bao c th, vic truyn pht t mt s thu bao c th xy ra ng thi m khng cn s can thip no, do s gim thiu tc ng nh nh hng a truy nhp.

    c/ Cc h thng anten thch ghi AAS (Adaptive Antena System)

    Cc h thng anten thch ghi AAS (Adaptive Antena System) l mt phn ca la chn tiu chun IEEE 802.16. AAS c kh nng iu chnh bp sng ch tp trung vo mt hng nht nh hoc cng c th tp trung vo nhiu hng. iu ny c ngha l trong khi pht tn hiu c gii hn theo mt hng nht nh ca pha thu, ging nh mt im sng. Cn khi thu, h thng AAS cng c kh nng gim nhiu ng knh t cc v tr khc. AAS c coi l s pht trin ca tng lai, c kh nng ci thin t l ti s dng ph tn v kh nng ca mt mng WiMAX

    d/MIMO- Multiple-Input and Multiple-Output

    La chn phn tp pht WiMAX s dng m ha thi gian khng gian, lm gim qu d tr yu cu v trnh nhiu. i vi phn tp pht, rt nhiu cc phng php kt hp ci thin kh nng ca h thng.

    M khng gian thi gian (Space Time Code STC): H tr phn tp truyn nh m Alamouti cung cp kh nng phn tp khng gian v gim d tr suy hao tn hiu.

    Ghp knh khng gian (SM): H tr ghp knh khng gian tn dng tc nh cao hn v gim thng lng. Nh ghp knh khng gian, nhiu lung s c truyn trn h thng nhiu anten. Nu pha thu cng c h thng nhiu anten, n c th phn tch cc lung khc nhau t c thng lng cao hn so vi cc h thng n anten.

    e/iu ch thch nghi v m ha(AMC- Adaptive Modulation and Coding)

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    iu ch thch nghi cho php h thng WiMAX iu chnh c phng php iu ch tn hiu da trn iu kin SNR ca tuyn. Khi tuyn truyn dn c cht lng tt, kiu iu ch cao nht c s dng, lm tng dung lng ca h thng. Khi tuyn mc cht lng thp hn, h thng WiMAX c th chuyn sang mt kiu iu ch thp hn m bo cht lng kt ni v n nh ca tuyn.

    Ngoi ra iu ch BPSK cng c dng gi cc thng bo tn hiu (signalling), broadcast...trong h thng WiMAX v n cho 1 vng ph ln nht.

    f/ K thut sa li trc (FEC-forward error correction)

    Cc k thut sa li trc c p dng trong h thng WiMAX gim t s tn hiu trn tp m yu cu. M ha sa li trc (FEC) Reed Solomon, m ha xon cc thut ton chn k t c s dng pht hin v sa li nhm ci thin thng lng ca h thng.

    g/ S dng li tn s

    c bit trong WiMAX, l dy tn s dng trn 2 cells k nhau l nh nhau. V trong WiMAX s dng OFDMA, v mi mt user s c phn b mt s tn s v symbol time nht nh (gi l zone/chunk). Nh th trnh nhiu th cc user ba ca nhng cell gn nhau s c phn b cc tn s khc nhau. chnh l khi nim chia nh tn s (fractional freq reuse).

    Hnh 10: Minh ha cc loi iu ch dng trong WiMAX

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    h/. T ng yu cu lp li kiu kt hp(HARQ- Hybrid automatic repeat request)

    WiMAX di ng cng h tr HARQ. HARQ c php s dng giao thc Dng v i N knh cung cp kh nng p ng nhanh ng gi li v ci tin kh nng ph sng ng bin cell. Ngoi ra ci thin hn na s n nh ca ng truyn. Mt knh dnh ring ACK cng c cung cp ng ln bo hiu ACK/NACK ca HARQ. Hot ng a knh HARQ cng c h tr.

    2.3 Cu hnh mng

    WiMAX h tr cu hnh mng a im v cu hnh mng li MESH

    2.3.1Cu hnh im-a im PMP

    PMP l mt mng truy nhp vi mt hoc nhiu BS c cng sut ln v nhiu SS nh hn. Ngi dng c th ngay lp tc truy nhp mng ch sau khi lp t thit b ngi dng. SS c th s dng cc anten tnh hng n cc BS, cc BS c th c nhiu anten c hng tc dng theo mi hng hay mt cung.

    Vi cu hnh ny trm gc BS l im trung tm cho cc trm thu bao SS. hng DL c th l qung b, a im hay n im. Kt ni ca mt SS n BS c c trng qua nhn dng kt ni CID.

    Hnh 11 Cu hnh PMP

    2.3.2 Cu hnh mt li MESH

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    Vi cu hnh ny SS c th lin lc trc tip vi nhau. Trm gc Mesh BS kt ni vi mt mng bn ngoi mng MESH. Mt s im phn bit nh sau:

    - Neighbor: Kt ni trc tip n mt node mng - Neighborhood : Tt c cc neighbor ca mt node to ra neighorhood. - Extended neighborhood: Tt c cc neighbor ca mt neighborhood.

    MESH khc PMP l trong kiu PMP cc SS ch lin h vi BS v tt c lu lng i qua BS.Vi kiu MESH tt c cc node c th lin lc vi mi node khc mt cch trc tip hoc bng nh tuyn nhiu bc thng qua cc SS khc.

    Mt h thng vi truy nhp n mt kt ni backhaul c gi l Mesh BS, trong khi cc h thng cn li c gi l Mesh SS. D cho MESH c mt h thng c gi l Mesh BS, h thng ny cng phi phi hp qung b vi cc node khc. Backhaul l cc anten im-im c dng kt ni cc BS c nh v qua khong cch xa.

    Hnh 12 Cu hnh mesh

    Mt mng MESH c th s dng hai loi lp lch qung b. Vi kiu lp lch phn tn, cc h thng trong phm vi hai bc ca mi node khc nhau chia s cc danh mc v hp tc m bo trnh xung t v chp nhn ti nguyn.

    MESH lp lch tp trung da vo Mesh BS tp hp cc yu cu ti nguyn t cc Mesh SS trong mt di bt k v phn phi cc yu cu ny vi kh nng c th.

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    Kh nng ny c chia s vi cc Mesh SS khc m d liu ca ngi dng c chuyn tip thng qua cc Mesh SS trao i vi Mesh BS.

    Trong kiu MESH, phn loi QoS c thc hin trn nn tng tng gi hn l c kt hp vi cc lin kt nh trong kiu PMP. Do ch c mt lin kt gia gia hai node Mesh lin lc vi nhau.

    2.4 Kin trc mng WIMAX

    Hnh 13 M hnh truyn thng ca WiMAX

    WiMAX hot ng tng t WiFi nhng tc cao v khong cch ln hn rt nhiu cng vi mt s lng ln ngi dng. Mt h thng WiMAX gm 2 phn:

    - Trm pht: ging nh cc trm BTS trong mng thng tin di ng vi cng sut ln c th ph sng mt vng rng ti 8000km2

    - Trm thu: c th l cc anten nh nh cc Card mng cm vo hoc c thit lp sn trn Mainboard bn trong cc my tnh, theo cch m WiFi vn dngCc trm pht BTS c kt ni ti mng Internet thng qua cc ng

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    truyn tc cao dnh ring hoc c th c ni ti mt BTS khc nh mt trn trung chuyn bng ng truyn thng (line of sight), v chnh v vy WiMAX c th ph sng n nhng vng rt xa.

    Cc anten thu/pht c th trao i thng tin vi nhau qua cc tia sng truyn thng hoc cc tia phn x. Trong trng hp truyn thng, cc anten c t c nh trn cc im cao, tn hiu trong trng hp ny n nh v tc truyn c th t ti a. Bng tn s dng c th dng tn s cao n 66GHz v tn s ny tn hiu t b giao thoa vi cc knh tn hiu khc v bng thng s dng cng ln hn. i vi trng hp tia phn x, WiMAX s dng bng tn thp hn, 2-11GHz, tng t nh WiFi, tn s thp tn hiu d dng vt qua cc vt cn, c th phn x, nhiu x, un cong, vng qua cc vt th n ch.

    WiMAX Forum nh ngha mt modul tham chiu mng WiMAX (NRM). NRM nhn dng cc thc th chc nng v cc im tham chiu qua tnh tng tc t c gia cc thc th chc nng

    Nhiu ASN ca cng mt operator to thnh mt NAP (Network Access Provider). Nhiu nh cung cp khc nhau s c th trin khai nhiu mng truy nhp khc nhau, ri chng s cng kt ni vi mt hoc nhiu CSN (Core Service Network).

    Hnh 14:Cc im tham chiu trong mng WiMAX

    Hnh v sau cung cp mt ci nhn c th hn v nhiu thc th trong cc nhm chc nng ca ASN v CSN.

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    Hnh 15 :Cc thc th v nhm chc nng trong mng

    CSN c nh ngha l mt tp cc chc nng mng cung cp cc dch v kt ni IP cho cc thu bao WiMAX. Mt CSN c th gm cc phn t mng nh router (b nh tuyn), my ch/proxy nhn thc AAA, c s d liu ngi dng v thit b cng lin mng. Mt CSN c th c trin khai nh mt phn ca nh cung cp dch v mng WiMAX.

    MS, ASN, CSN v cc im tham chiu c nhn dng mt cch r rng cho lin kt ca cc thc th logic. Cc im tham chiu miu t mt nhm cc chc nng.. Vic to nhm v phn phi cc chc nng trong cc thit b vt l, trong mt thc th chc nng (nh ASN) l mt la chn b sung. Mt nh sn xut c th chn bt k b sung cc chc nng vt l no, ring bit hoc kt hp, vi iu kin vic b sung p ng cc yu cu v tnh tng tc v v chc nng.

    Mc tiu ca NRM l cho php nhiu ty chn b sung cc chc nng xc nh, v phi c tnh tng tc gia cc thc th chc nng khc nhau. Tnh tng tc da trn nh ngha cc giao thc truyn thng v cch x l mt bng d liu gia cc thc th chc nng t c mt chc nng u cui-u cui hon thin, v d, bo mt hay qun l tnh di ng. Do , cc thc th chc nng pha ny hay pha kia ca mt im tham chiu miu t mt tp hp cc im cui mt bng iu khin v truyn ti.

    Cc giao din ny nh ngha cc th tc v cc giao thc v cc lin kt logic, lin kt vt l truy nhp cc thc th.Cc chi tit k thut ca mng cho h thng WiMAX da trn c s nhiu nguyn l kin trc mng c bn, c lit k di

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    y. Mt s cc nguyn l chung c hng dn trin khai kin trc mng WiMAX di ng bao gm:

    - Cung cp s tch bit v mt logic gia cc th tc ni trn v nh a ch IP, nh tuyn v th tc qun l kt ni v cc giao thc cho php s dng kin trc truy nhp c bn trong cc trng hp trin khai tng thch v mt mnh.

    - H tr chia s mt hay nhiu ASN ca mt NAP gia nhiu NSP. - H tr dch v cung cp NSP n l qua nhiu ASN c qun l bi mt hay

    nhiu NAP. - H tr vic pht hin v la chn cc NSP c th truy nhp bi mt MS hay

    SS. - H tr cc NAP m s dng mt hay nhiu cu hnh ASN. - H tr truy nhp n cc dch v ca nh khai thc hin thi thng qua tng

    thch cc chc nng khi cn thit. - Chi tit k thut ca cc im tham chiu khng hn ch v hon ton xc nh

    gia mt nhm cc thc th chc nng mng (trong mt ASN, gia cc ASN, gia mt ASN v mt CSN v gia cc CSN) v c bit gia mt MS, ASN v CSN cho php tng tc gia nhiu nh cung cp.

    - H tr cc phng php nng cp gia nhiu kiu thng dng thnh cc gi nh v bt buc hp l v mt cng ngh.

    - Cho php b sung cc nh cung cp khc nhau trn c s kt hp cc thc th chc nng khc nhau trn cc thc th mng vt l, vi iu kin nhng b sung ny tun theo cc giao thc v th tc quy chun qua cc im tham chiu thch hp, nh nh ngha trong c im k thut mng.

    - H tr cho trng hp mt nh khai thc ring l bnh thng nht s dng mt ASN cng vi mt t hp c gii hn cc chc nng CSN, v th nh khai thc c th a ra dch v truy cp Internet c bn m khng xem xt v Roaming hay tng thch.

    2.4.1 Qu trnh vo mng

    Mt trm thu bao WiMAX phi hon thnh th tc vo mng lin lc c vi mng. Trng thi vo mng thay i thit lp li nu n b li tip tc t bt k trng thi no.

    ng b knh ng xung

    Khi SS mun vo mng, n qut mt knh trong danh sch tn s nh ngha. Thng thng mt SS c cu hnh s dng mt BS c th vi mt t hp cho trc cc tham s vn hnh, khi hot ng trong bng tn c cp php. Nu SS tm thy mt knh ng xung v c th ng b mc vt l s dng

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    mo u chu k khung. Thng tin v iu ch v cc tham s UL v DL khc ginh c bng cch quan st DCD v UCD ca knh ng xung.

    Initial Ranging

    Khi mt SS c ng b vi knh DL v nhn DL v UL-MAP cho mt khung, n bt u th tc Initial Ranging bng cch gi mt bn tin MAC yu cu Ranging s dng cng sut truyn dn cc tiu. Nu khng nhn c tr li t BS, SS gi li bn tin trn mt khung k tip s dng cng sut truyn dn cao hn. Cui cng l SS nhn mt tr li Ranging.Tr li th hin cng sut v nhng hiu chnh nh thi m SS phi lm hoc th hin s thnh cng. Nu tr li ch th hiu chnh, SS phi lm cc hiu chnh ny v gi mt yu cu Ranging khc. Nu tr li ch th thnh cng, SS sn sng gi d liu ng ln.

    Trao i cc kh nng

    Sau khi hong thnh bc Initial Ranging thnh cng, SS gi bn tin yu cu kh nng cho BS miu t kh nng ca n v mc iu ch, lc m ha v tc , phng php song cng c h tr. BS chp nhn hoc t chi SS da vo kh nng ca n.

    Nhn thc

    Sau khi thng lng kh nng, BS nhn thc SS, v cung cp vt liu kha cho php mt m d liu. SS gi chng nhn X.509 ca nh sn xut SS v miu t cc thut ton mt m ha c h tr cho BS ca n. BS ph chun nhn dng ca SS, quyt nh thut ton mt m v giao thc c s dng sau gi mt bn tin tr l nhn thc cho SS. Tr li cha vt liu kha c s dng bi SS. SS c yu cu thc hin nh k th tc nhn thc v trao i kha lm mi vt liu kha ca n.

    ng k

    Sau khi nhn thc, SS gi mt bn tin yu cu ng k cho BS v BS gi tr li ng k ti SS. Trao i ng k bao gm h tr phin bn IP, h tr SS c qun l hoc khng c qun l, h tr cc tham s ARQ, h tr cc ty chn phn loi, h tr CRC v iu khin lung.

    Kt ni

    Sau khi ng k, SS khi ng DHCP (IETF RFC 2131) nhn c a ch IP v cc tham s khc thit lp kt ni IP. BS v SS duy tr ngy gi hin ti s

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    dng giao thc the time of the day (IETF RFC 868). SS cng ti v cc tham s sn sng cho vic hot ng s dng TFTP (IETF RFC 1350).

    Hnh 16 : Qu trnh vo mng

    To kt ni truyn ti

    Sau khi hon thnh ng k v trao i cc tham s vn hnh, cc kt ni truyn ti c to ra. Vi cc lung dch v c d tr trc, th tc to kt ni c khi u bi BS. BS gi mt bn tin yu cu thm lung dch v ng cho SS v SS xc nhn vic to kt ni. Vi cc lung dch v khng d tr trc, to kt ni c khi to bi SS bng cch gi mt bn tin yu cu thm lung dch v ng cho BS. BS tr li vi mt xc nhn.

    2.4.2 Mt s nguyn l c bn trong trin khai mng WiMAX:

    1. Kin trc mng da trn c cu chuyn mch gi, bao gm cc th tc da trn chun IEEE 802.16 v cc sa i ca n, cc chun IETF v Ethernet ph hp.

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    2. Kin trc mng cho php tch ring kin trc truy nhp (v h tr cc cu hnh) t dch v kt ni IP. Cc phn t mng ca h thng kt ni khng nhn bit v cc chi tit v tuyn IEEE 802.16.

    3. Kin trc mng cho php tnh modul v linh ng cung cp mt di rn cc ty chn nh:

    Mng WiMAX t quy m nh n quy m ln. Cc bng tn v tuyn vng nng thn, ngoi v thnh th Cc cu hnh c th bc, bng phng hoc Mesh v cc bin th ca

    chng. Cc kiu c nh, mang xch v di ng cng tn ti

    2.4.3 Cc dch v v cc ng dng c h tr trong WiMAX.

    1. Cc dch v thoi, a phng tin v cc dch v iu tit c y quyn khc nh dch v khn v ngn chn hp php.

    2. Truy nhp n nhiu mng ca nh cung cp dch v ng dng (ASP) c lp theo kiu khng nhn bit.

    3. Truyn thng in thoi di ng s dng VoIP. 4. H tr giao din vi nhiu cng tng thch v media cho php vic pht cc

    dch v hin thi/ k tha truyn qua IP (v d SMS qua IP, MMS, WAP) truy nhp mng WiMAX.

    5. H tr vic pht cc dch v qung b v a im qua mng truy nhp WiMAX.

    2.5 Nhng u im v mi trng ng dng ca WiMAX 2.5.1 u im

    C s quan trng ca cng ngh WiMAX l s tng thch ca thit b WiMAX, c Din n WiMAX chng nhn, to s tin cy v lm tng s lng ln cho nh cung cp dch v khi mua thit b khng ch t 1 cng ty v tt c u tng thch vi nhau. Din n WiMAX ln u tin t hp nhng cng ty hng u trong ngnh truyn thng v my tnh to nn mt nn tng chung cho vic trin khai cc dch v v tuyn bng rng IP trn ton cu.Ngoi ra cn cc c s quan trng khc l :

    Chi ph thp hn

    CPE v tuyn c nh c th s dng cng loi chipset modem c s dng trong my tnh c nhn (PC) v PDA, v khong cch gn cc modem c th t lp t trong nh CPE s tng t nh cp, DSL v cc trm gc c th s dng cng loi chipset chung c thit k cho cc im truy cp WiMAX chi ph thp v cui

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    cng l s lng tng cng tha mn cho vic u t vo vic tch hp mc cao hn cc chipset tn s v tuyn (RF), lm chi ph gim hn na.

    bao ph rng hn

    Cng ngh sau WiMAX c ti u mang n bao ph NLOS tt nht. Cc u im ca NLOS l bao ph trn din rng, kh nng d bo bao ph tt hn v chi ph thp hn c ngha l s trm gc v backhaul t hn, nh c RF n gin, cc thi im lp t thp ngn hn v lp t CPE nhanh hn.

    Nh c cc k thut ci tin bao ph NLOS nh phn tp, m ha thi gian khng gian v yu cu truyn li t ng (Automatic Retransmission Request - ARQ), cc khong cch bao ph s c tng ln.

    Cng sut cao hn

    u im quan trng ca WiMAX l s dng k thut OFDM (Orthogonal Frequency Division Multiplexing) qua cc c ch iu ch n sng mang vi kh nng cung cp hiu sut bng thng cao hn v do thng lng d liu cao hn vi lung xung hn 1Mbit/s v thm ch cc tc d liu cao hn nhiu d trong NLOS vi cc iu kin a ng. iu ch thch ng (Adaptive Modulation) cng lm tng tin cy ng kt ni i vi hot ng phn loi sng mang v kh nng gi iu ch 64QAM khong cch rng hn, tng cng sut qua cc khong cch di hn

    Chun cho truy cp v tuyn c nh v di ng

    WiMAX s tr thnh mt gii php chi ph hp l nht cho cc nh khai thc trin khai cc ng dng v tuyn c nh v di ng cho cc my xch tay v PDA.

    Din n WiMAX s chng nhn cc sn phm tun th v tng thch da trn cc chun 802.16 ca IEEE v HiperMAN ca ETSI.

    Li ch ca doanh nghip v ngi s dng h gia nh

    i vi cc doanh nghip, WiMAX cho php truy cp bng rng vi chi ph hp l. V phn ln cc doanh nghip s khng c chia thnh khu vc c ng cp, la chn duy nht ca h i vi dch v bng rng l t cc nh cung cp vin thng a phng. iu ny dn ti s c quyn. Cc doanh nghip s c hng li t vic trin khai cc h thng WiMAX chng nhn nh to ra s cnh tranh mi trn th trng, gim gi v cho php cc doanh nghip thit lp mng ring ca mnh. iu ny c bit ph hp i vi cc ngnh nh kh t, m,

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    nng nghip, vn ti, xy dng v cc ngnh khc nm nhng v tr xa xi, ho lnh.

    i vi ngi s dng l h gia nh nhng vng nng thn (ni dch v DSL v cp cha th vn ti), WiMAX mang li kh nng truy cp bng rng. iu ny c bit ph hp cc nc ang pht trin ni m h tng vin thng truyn thng vn cha th tip cn

    2.5.2 Mi trng ng dng ca WiMAX

    WiMAX vi th mnh l ph sng rng, khng cn c vo a hnh bng phng hay him tr, ph hp cho vic ph cp Internet bng thng rng ti mi min t nc, k c cc vng su, vng xa. WiMAX c coi l cng ngh l tng cho ton b khu vc ng Nam , gip cc nc trong khu vc thc hin cc mc tiu cp thit nh chnh ph in t, pht trin gio dc, y t, nng nghip...

    Mt mng MAN khng dy da trn chun giao din khng gian WiMAX c cu hnh theo cng mt cch nh mt mng t bo truyn thng vi chin lc nh v trm gc BS s dng mt kin trc PMP phn pht cc dch v qua mt bn knh ln n vi km ty thuc vo tn s, cng sut pht v nhy u thu. Trong cc vng vi mt dn c cao, phm vi thng s b hn ch hn gii hn do lng ph sn c.

    Cc BS theo tiu chun c backhaul n mng li bng phng tin si hay cc lin kt sng vi ba im-im n cc node si c sn hay thng qua cc ng dy cho thu t mt nh khai thc hu tuyn hin thi. Phm vi v kkh nng NLOS lm cho cng ngh ny tr nn hp dn c mang li li nhun trong nhiu loi mi trng rng ln. Cng ngh ny c hnh dung ban u nh mt phng tin cung cp truy nhp bng rng chng cui (last mile) khng dy trong cc mng MAN vi hiu sut v cc dch v c th bng hoc tt hn DSL truyn thng, cp hay cc dch v ng dy cho thu T1/E1.

    Ngy nay th trng ny ch yu ph thuc vo tnh sn c ca DSL hay cp. Mt s vng m cc dch v c sn khng p ng s mong i ca khch hng v hiu nng hay tin cy v gi c qu cao. Trong nhiu vng nng thn th khch hng b hn ch v cc dch v quay s tc thp. Trong cc nc ang pht trin c nhiu vng khng c cc phng tin sn c truy nhp Internet. Cng ngh WiMAX s cho php mt nh khai thc tp trung v mt kinh t vo loi th trng ny v c mt iu kin kinh doanh thun li di mt s a dng ca cc iu kin con ngi.

    a\ Cc nh kinh doanh va v nh

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    Loi th trng ny thng l rt nh trong cc vng khng phi cc mi trng thnh th cnh tranh mc cao. Cng ngh WiMAX c th mang li li nhun khi p ng cc nhu cu ca cc nh kinh doanh va v nh trong cc mi trng mt thp v cng c th cung cp mt chn la c li trong cc mi trng thnh th cnh tranh vi DSL v cc dch v ng dy thu.

    b\ Backhaul im nng Wi-fi

    Cc im nng Wifi c lp t trn khp th gii mt tc cao. Tuy nhin,mt trong nhng tr ngi cho vic tip tc pht trin im nng l tnh sn sng ca cc gii php Backhaul dung lng cao, c nhiu li ch. ng dng ny cng c th c tp trung vi cng ngh WiMAX. V vi kh nng di ng, WiMAX cng c th lp y khong trng gia cc vng bao ph im nng Wi-fi.

    Hnh17 :cc Mi trng ng dng ca WiMAX

    c\ Backhaul mng t bo

    Phn ln backhaul c thc hin bng cch thu cc dch v T1/E1 t cc nh khai thc hu tuyn hin thi hoc s dng sng vi ba im-im thng dng hn cho mng t bo di ng, nhng WiMAX c th hot ng ng vai tr trong

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    vic cho php cc nh khai thc di ng tng mt cch c li kh nng backhaul s dng WiMAX nh mt mng bao ph. Phng php bao ph ny s cho php cc nh khai thc di ng thm kh nng yu cu h tr phm vi ln cc dch v di ng mi m h ln k hoch ngh khng c s ri ro ca vic ph hy cc dch v ang tn ti. Trong nhiu trng hp ng dng ny s c tp trung mt cch tt nht thng qua 801.16 da trn cc lin kt im-im chia s vi h thng PMP.

    d\ Cc dch v an ton cng cng v cc mng ring

    H tr cho cc dch v di dng v kh nng cung cp bao ph khp ni trong mt vng thnh th , cung cp mt cng c thi hnh lut l, bo v cao v cc cu to an ton cng cng khc cho php chng duy tr truyn thng quan trng trong cc iu kin bt li khc nhau. Cc mng ring cho cc ngnh cng nghip phc tp, cc trng i hc v cc loi mi trng khc cng u l mt c hi kinh doanh tim nng cho WiMAX.

    Cng ngh WiMAX l gii php cho nhiu loi ng dng bng rng tc cao cng thi im vi khong cch xa v cho php cc nh khai thc dch v hi t tt c trn mng IP cung cp cc dch v "3 cung": d liu, thoi v video.

    WiMAX vi s h tr QoS, kh nng vn di v cng sut d liu cao c dnh cho cc ng dng truy cp bng rng c nh nhng vng xa xi, ho lnh, nht l khi khong cch l qu ln i vi DSL v cp cng nh cho cc khu vc thnh th cc nc ang pht trin. Nhng ng dng cho h dn gm c Internet tc cao, thoi qua IP, video lung/chi game trc tuyn cng vi cc ng dng cng thm cho doanh nghip nh hi ngh video v gim st video, mng ring o bo mt (yu cu an ninh cao). Cng ngh WiMAX cho php bao trm cc ng dng vi yu cu bng thng rng hn.

    WiMAX cng cho php cc ng dng truy cp xch tay, vi s hp nht trong cc my tnh xch tay v PDA, cho php cc khu vc ni th v thnh ph tr thnh nhng "khu vc din rng" ngha l c th truy cp v tuyn bng rng ngoi tri. Do vy, WiMAX l mt cng ngh b sung bnh thng cho cc mng di ng v cung cp bng thng ln hn v cho cc mng Wi-Fi nh cung cp kt ni bng rng cc khu vcln hn.

    2.6 So snh gia Wi-Fi v WiMAX[4]

    S khc nhau c bn nht gia WiMAX v Wi-fi l chng c thit k cho cc ng dng hon ton khc nhau. Wi-Fi l mt cng ngh mng vng ni ht LAN c thit k tng thm tnh di ng cho cc mng LAN hu tuyn ring. WiMAX mt mt khc c thit k cung cp mt dch v truy nhp khng dy

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    bng rng (BWA) cho mng vng thnh th MAN. V th trong khi Wi-Fi h tr truyn dn trong phm vi hn trm mt th WiMAX c th h tr cc ngi dng trong bn knh ti hng chc kilmt.

    Bn cnh s khc nhau v phm vi truyn dn, mt s ci thin v cng ngh lien kt v tuyn l khc nhau gia WiMAX v Wi-Fi. Chun IEEE802.11 WLAN miu t bn giao din lin kt v tuyn hot ng trong bng tn v tuyn khng cp php 2.4 hoc 5GHz. Cc chun WiMAX bao gm mt di rng hn cc b sung tim nng gii quyt cc yu cu ca cc sng mang khp th gii. Cc bng tn WiMAX s dng c bng tn cp php v khng cp php ch yu trong di t 2-11GHz

    Trong cc bng tn khng cp php, cc chun WiMAX kt hp c im la chn tn s ng nhng ni m sng v tuyn t dng tm kim mt knh cha s dng. Trong cc vng xa, nhiu c th c gim thiu.

    Trong khi vi WiMAX th knh ng ln v ng xung s dng k thut ghp knh phn chia theo thi gian TDD v ghp knh phn chia theo tn s FDD. Trong TDD vi khe thi gian c n nh cho ng ln v ng xung tch bit nhau v th knh truyn l song cng ton phn. Trong khi gim tc truyn 50% th cc h thng ny ch s dng mt na bng tn v tuyn so vi FDD.

    i vi Wi-Fi th tt c cc h thng Wi-Fi l cc h thng TDD trn c s tranh chp ni m im truy nhp v cc trm s dng chung mt knh. Bi v hot ng mi trng dng chung nn tt c mng Wi-Fi l bn song cng.

    Wi-Fi s dng hai cng ngh truyn dn v tuyn c bn. :802.11b: lin kt v tuyn s dng mt cng ngh tri ph tun t trc tip c gi l kha c m ha b sung (CCK). Sau lung bit c x l vi m c bit v sau c iu ch s dng QPSK.

    802.11a v 802.11g s dng OFDM. u pht m ha lung bit trn 64 sng mang s dng BPSK, QPSK hay mt trong hai kiu 16-QAM, 64-QAM. Mt s thng tin c pht l khng cn thit, v th u thu khng phi nhn tt c cc sng mang con khi phc thng tin.

    WiMAX s dng cng ngh OFDM v OFDMA cho lp vt l lm tng quy m v tc cho mng.

    C WiMAX v Wi-Fi u s dng iu ch thch ng v nhiu mc hiu chnh li trc ti u ha tc truyn v hiu sut li. Khi mt tn hiu v tuyn gim cng sut hay c nhiu th t l li s tng. iu ch thch ng ngha l u pht s t ng thay i hiu sut tng ln hay thm ch gim i.

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    C ch hiu chnh li trc FEC nhm khc phc bt li v ci thin hiu nng truyn dn. Tuy nhin lc u Wi-Fi vi chun 802.11b cha c FEC nhng FEC m xon c kt hp trong 802.11a v 802.11g. WiMAX s dng c hai h thng FEC m xon v Reed-Solomon.

    Bng 7: So snh WiMAX v WiFi

    Thuc tnh

    Wi-Fi (802.11)

    WiMAX(802.16)

    Kh nng

    - Knh c nh (20MHz) - MAC h tr hng chc ngi s dng

    - Knh c bng tn thay i Kh nng m rng bng tn t 1,5#20Mhz - MAC h tr hng trm ngi s dng

    Cht lng QoS

    - S dng (CSMA/CA) nn khng m bo v cht lng - Hin ti khng h tr m thanh,video - Khng cho php cc mc dch v khc nhau - Ch c TDD (bt i xng) - Ch 802.11e u tin cho QoS

    - C m bo v cht lng trn MAC -H tr m thanh,hnh nh - H tr nhiu mc dch v T1 cho ngi bun bn, c bit hiu qu nh ring - C TDD/FDD/HFDD (c i xng v bt i xng) - Yu cu bt buc cho QoS

    Phm vi

    - Ti u khong 100 m - Khng c kh nng b khong cch - Thit k a ng trong nh (tr 0,8ms) -Ti u ho tp trung ti hai lp PHY v MAC trong phm vi 100m - M rng phm vi nh thay i cng sut nhng lp MAC c th khng chun tc

    -Ti u ho khng 50km - Thit k cho nhiu ngi s dng hng km - Chu c tr a ng ln c 10 ms - Lp PHY v MAC vi kh nng m rng trong phm vi cho php - MAC chun tc

    Ph sng

    - Ti u ho trong nh - Khng h tr mng cu hnh pha trn

    - Ti u ho bn ngoi trong tm nhn hn ch - H tr cu hnh mng pha trn - H tr k thut anten thng minh

    Bo mt

    - Chun ang tn ti l WPA v WEP - 802.11i c ch bo mt a ch

    - C kho b ba DES (128 bit) v RSA(1024 bit

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    Bn cnh trong WiMAX c h tr nhiu cng ngh v tuyn hin i nh cc anten thng minh c th lm gim thiu nhiu v nng cao tc truyn. Kt hp vi tnh a dng u pht, a dng u thu MIMO ci thin phm vi bao ph. Tc truyn d liu c h tr cho WiMAX l rt cao, ln ti 100Mbps trong mt knh 20MHz trong tc c duy tr l 70Mbps. i vi Wi-Fi tc truyn c h tr ti a ch t 54Mbps.

    Lp MAC ca WiMAX v Wi-Fi hon ton khc nhau. i vi WiMAX th giao thc lp MAC c th chia s knh v tuyn gia hng trm ngi dng trong khi vn m bo QoS, WiMAX s dng k thut yu cu/ cp pht loi tr cc tranh chp ng ln h tr tr nht qun cho thoi v tr bin i cho cc dch v d liu. Giao thc MAC ca WiMAX cng c c im sa li s dng yu cu truyn li t ng ARQ. Ngc li trong Wi-Fi th giao thc lp MAC trn c s tranh chp. Giao thc MAC ca Wi-FI c gi l a truy nhp cm ng sng mang v trnh xung t (CSMA/CA). Trong khi WLAN l bn song cng chia s mi trng, tt c cc trm s pht v thu trn cng mt knh v tuyn. Vn c bn l cc trm khng th lng khi khi ang gi v v th khng th pht hin xung t.

    V th mt k thut c h tr cho Wi-Fi gi l chc nng iu khin phn tn (DCF). Nn tng k thut c bn l nh ngha mt h thng ca cc khong thi gian i v cc b m thi gian li gim nhng khng hy b cc xung t. Mt trm Wi-Fi s ch pht nu n cho rng knh ri. Tt c vic truyn dn c xc nhn, v th nu trm gc khng c xc nhn, n cho rng mt xung t xy ra v th li sau mt khong thi gian i ngu nhin. Tc ng ca xung t s gia tng khi lu lng tng ln hay ang trong tnh trng trm di ng khng th lng nghe cc trm khc (vn node n).

    Trong mng WiMAX, giao thc yu cu/ chp nhn c h tr. Truy nhp ng ln s c iu khin bi trm gc. Cc ngi dng mun truyn ng ln u tin phi gi cc yu cu trn mt knh truy nhp trn c s tranh chp. Cho php dnh ring dng knh ng ln sau c cp pht bi trm gc s dng mt h thng chp nhn. Ch c mt trm c cho php gi trong mt thi im, nh vy khng c xung t ng ln.

    Do cc li ch m giao thc yu cu/ chp nhn mang li nn WiMAX h tr nhiu mc QoS. K thut truy nhp ca WiMAX c th h tr 4 loi dch v c bn. Trong Wi-Fi th chun 802.11j c h tr QoS. C hai kiu hot ng c s dng ci thin cc dch v thoi:

    - M rng a mi trng Wi-Fi (WME) - a mi trng c lp lch Wi-Fi (WSM)

    WME s dng mt giao thc c gi l truy nhp iu khin phn tn nng cao (EDCA) l mt phin bn ci tin ca DCF. EDCA nh ngha 8 mc u tin truy nhp cho knh v tuyn chia s. Ging nh DCF ban u, truy nhp EDCA l mt

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    giao thc trn c s tranh chp m s dng mt khong thi gian i v cc b m thi gain li trnh xung t. Tuy nhin, vi DCF tt c trm s dng cng mt gi tr v do c cng u tin cho vic pht trn knh truyn. Vi EDCA mi u tin truy nhp khc nhau c n nh mt khong thi gain i v b m li khc nhau. Truyn dn vi u tin truy nhp cao hn c gn khong i ngn hn. Chun cng bao gm mt kiu packet-bursting cho php mt im truy nhp hay mt trm di ng d tr knh v gi 3 n 5 gi theo tun t.

    EDCA khng c k thut phn pht dch v tr nht qun. N ch m bo rng truyn thoi s i t hn truyn d liu. Tr nht qun chnh xc c th c cung cp vi ty chn WSM. WSM hot ng gn ging chc nng iu khin im (PCF). Trong WSM, im truy nhp theo nh k qung b mt bn tin iu khin bt buc tt c trm phi x l knh khi bn v khng c gng truyn. Trong chu k , im truy nhp kim sot vng mi trm c nh ngha dch v cm bin vi thi gian. s dng WSM, thit b u tin phi gi mt profile lu lng miu t cc yu cu bng thng, tr v jitter. Nu im truy nhp khng c ti nguyn p ng profile lu lng, n gi li mt tn hiu bn. Nguyn nhn m WSM l mt c im ty chn l tt c cc im truy nhp c th gi li mt thng bo dch v cha sn sng ti cc yu cu profile ca trm gc

    V bo mt, Trong Wi-Fi, mt m ha l ty chn, v c ba cng ngh khc nhau c nh ngha:

    - Wired Equivalent Privacy (WEP): mt m ha 104 bit hoc 40 bit trn c s RC4 vi kha tnh

    - Wi-Fi Protected Access(WPA): Mt chun mi s dng kha WEP 104 hoc 40 bit nhng thay i kha trn mi gi cn tr nhng k trm kha. Giao thc chuyn kha c gi l giao thc ton vn kha theo thi gian TKIP(Temporal Key Tntegrity Protocol).

    - IEEE 802.11i/WPA2: Chun ny da trn cng ngh mt m ha mnh uc gi l chun mt m nng cao AES. Mt m trong WiMAX ban u l chun mt m s (3DES). Sau kt hp vi chun mt m nng cao AES v m bo tnh bo mt cao.

    V tnh di ng trong WiMAX v Wi-Fi cng c nhng khc bit. Trong khi chun 802.16 ca WiMAX c thit k cho truy nhp bng rng di ng m bo tc cao v chuyn giao khng gin on, m bo tc di chuyn ca phng tin giao thng. Vi Wi-Fi tnh di ng b hn ch v ch m bo cho vic di chuyn tc thp.

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    Tng kt

    Sau khi tm hiu kin trc mng WiMAX vi nhng k thut u vit c s dng gip cng ngh WiMAX c nhng c im vt tri nh kh nng che ph trong c iu kin tm nhn thng (LOS) v khng theo tm nhn thng (NLOS). cho php nh khai thc cung cp d liu bng rng n nhiu i tng khch hng.

    Cng ngh WiMAX cng c rt nhiu u im em li t cc cng ngh nh: cng ngh OFDM, iu ch thch nghi v hiu chnh li. Ngoi ra, WiMAX cng c nhiu tnh nng tu chn nh: ARQ, knh con ho, phn tp, v m ho khng gian - thi gian ha hn s em li cho nh khai thc hiu sut v cht lng dch v cao hn so vi cc cng ngh khc.

    Da vo nhng c s k thut ny nh gi tnh kh thi ca cng ngh gip cc nh khai thc dch v cn bng gia gi thnh v hiu sut; la chn cc tnh nng hp l cho m hnh kinh doanh c th.

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    Chng 3

    Kh Nng ng Dng WiMAX Ti Vit Nam

    Trong chng mt v chng hai ta thy ,so vi cc h thng truy nhp bng rng, WiMAX c nhng th mnh vt tri nh h tr nhiu cu hnh , c kh nng ph sng rng khp,tnh bo mt cao nh h tr chun mt m d liu tin tinv v.. vi nhng dch v c th c cung cp trn mng WiMAX nh thoi truyn thng hoc thoi qua Internet (VoIP); truy cp Internet tc cao; hi ngh truyn hnh; mng ring o; truyn hnh di ng; gii tr trc tuyn v nhiu dch v gi tr gia tng khc.

    Chnh v nhng u th m WiMAX ang thu ht c s quan tm rt ln ca th gii.

    3.1 Tnh hnh trin khai WiMAX trn th gii

    WiMAX hin ang c th nghim mt s nc nh Nht Bn, Nga v Vit Nam.

    Cng ngh ny c bit ph hp vi nhng khu vc c a hnh phc tp ,v nhng ni m h h thng cp ng cha c trin khai, mt khc, do bn knh ph sng rng v tn hiu mnh cho php sng WiMAX tip cn c c nhng khu vc xa xi ho lnh, iu m WiFi khng th thc hin.

    Ti mt s ni dch v DSL c trin khai hng lot nhng cht lng ng dy km v khong cch t ngi dng n cc tng i trung tm xa hoc mt dn c thp nn tc ng truyn khng m bo.WiMAX vi kh nng h tr cht lng QoS ,vng ph sng xa ,tc cao,ngoi ra vi u im khng y v vi chn 802.16e h tr kh nng di ng khin cho WiMAX s l mt la chn tt

    Hin nay cc h thng ch yu c trin khai vi cu hnh im a im v cu hnh li

    3.1.1 Tnh hnh chung

    Cng ngh ny hin mi ch c th nghim mt s khu vc trn th gii. L cng ngh ra i sau nn WiMAX c nhiu u im khc phc c mt s kh khn m nhng cng ngh trc gp phi. Din n WiMAX thu ht c s quan tm ln ca rt nhiu nh cung cp dch v v thit b vin thng hng u nh:

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    Tp on Intel lin tc vn ng v ng h chun WiMAX 802.16. H u t ti 600 triu USD cho Clearwire, hng cung cp dch v khng dy tc cao cho ngi tiu dng ti M.Vo thng 7/2007 Clearwire lp k hoch cho dn IPO 400 triu USD vi s u t 600 triu USD t Intel. Chin lc ca Intel trong vic to ra mt sc ht th trng vi cc chip thng qua vic u t vo mt nh cung cp dch v m s cn thit nhiu chip trong cc thit b v CPE.[16]

    NextNet cng ang c bit n Motorola cho nhng d n ca mnh. R rng, Motorola bn thn l mt nh cung cp mt bng WiMAX rng ln do vy Motorola thu ht nn tng c lp t ca NextNet. Tuy nhin, Motorola nhn c nhiu thin v vic c mt nn tng c lp t quy m t cc nh cung cp khc. Chng ta hy xem v tr th trng k tip ca cc nh cung cp vin thng trong th trng WiMAX. Sam sung ang dn u vic ng gi cc sn phm WiMAX di ng, Alcatel v Siemens ang to ra nhng n lc mnh m a cc sn phm WiMAX ca h ra th trng. OEMing t Airspan Qualcom cn phi duyt li WiMAX trc khi ri khi xng. Vic kim nh thc t xu hng hot ng WiMAX s l th t ca cc nh cung cp trong th gii WiMAX

    Cng nh Intel, cc sn phm WiMAX u tin c ch i n t: Proxim, hng ch to kinh doanh v WLAN, y c cc sn phm WiMAX ang trong cc phng th nghim.

    Truyn thng Ensemble. Mt s tp on truyn thng v dch v Internet ln trn th gii nh News Corportion hay Yahoo cng mt n WiMAX v coi y l cng ngh b sung chomng di ng v bng rng c nh. Ti Nht, lin minh SoftBank - Motorola hin cng cho trin khai WiMAX di ng trn di tn 2.5 GHz bt u t thng 9/2006.Trong khi , mt t th nghim cng ngh vi quy m ln cng ang din ra ti Nga. Hai hng thit b cng ngh Avalcom v Aperto nc ny kt hp vi nhiunh cung cp dch v hin thc ha d n ti nhiu khu vc nh Moscow, Siberia...[2]

    Ring ti Hn Quc, do khng mun chng kin du hiu "Intel Inside" chim lnh trn th trng bng rng khng dy, Samsung tch cc ng h pht trin mt cng ngh tng t mang tn WiBro nhm gt b WiMAX ti nc ny. Cc hng vin thng y bt u kinh doanh dch v WiBro khu vc trung tm, trng i hc v cc tuyn giao thng cng cng chnh trong Seoul. Khch hng s mua th tr gi t 170 USD n 300 USD ci vo my tnh xch tay cn th h tr nhng thit b di ng khc nh PDA v in thoi thng minh s c mt trn th trng vi thng na.

    Flarion, hng ny c mt th nghim chy th Nam Hn Quc ca c cu bng rng khng dy s dng cng ngh anten thng minh v h tr 802.16a. Hn Quc c xem nh mt lnh th ni m bng rng khng dy c thng qua

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    nhanh nht. Tuy nhin, ngi lnh o ca hng ny quan tm n chun 802.20 hay Mobile-Fi.

    Fujitsu Microelectronics ang pht trin mt thit b 802.16. Fujitsu s lm vic vi nhiu nh cung cp cc thit b trc u cui v ngh h tng thch vi thit b ca hng.

    Taiwan-based Gen-WAN Technology gii thiu thit b mng khng dy bng rng s dng 802.16a, ngh cc trm gc, cc thit b u cui c nh v di ng, cc b lp v cc h thng qun l mng. Hng ny s tung ra th trng cc sn phm c gi l BWIA, ban u cho s an ton cng cng v cc mc ch qun s, WiMAX ngh cc tn hiu ng tin cy hn mng t bo trong tnh hnh khn cp.

    Wi-LAN, mt trong nhng ngi sng lp ch cht v WiMAX, a ra th trng cc gii php h thng tin chun ha da trn chip v s h tr hon hon vic chun ha trong thi gian ti. Cng ngh OFDM bng rng c cp bng sng ch ,bao gm c chun 802.16a v cng ty ny c mt c s h tng v hp ng trin khai vi Fujitsu Microelectronics.

    Broadcom v Texas Instruments cng ang a ra nhng qung co v WiMAX v c mong ch a vo th trng bn cnh Intel v Fujitsu. y l mt lnh vc m cc hng ch to chip s nh r tp hp cc kh nng ct li v iu khin cc chc nng ct li v th h gi vai tr c bn trong xu hng pht trin ca 802.16.

    Cc i tc cng ngh u tin ca Intel t th trng BWA, cc hng ny s s dng cc sn phm Intel sp ti trong cc trm gc c quyn trc y ca h, l Alvarion v Aperto Networks. Alvarion c mt hp ng quan trng h tr China Unicom vi cc thit b WiMAX cho 6 thnh ph c gii thiu u tin.

    AirTap Communications l mt trong nhng ngi ng k u tin vo th trng mng WiMAX M, phc v cc SME v cc nh kinh doanh ln trong phm vi cc vng thnh th.

    3.1.2 Cc thit b c gii thiu trn th gii

    4/2005, h thng WiMAX da trn chip (SoC) ca Fujitsu c gii thiu, ni ln nh mt ngi ng u trong cng ngh bn dn khng dy bng rng. Vi mt s b sung vo lp MAC v PHY ca IEEE 802.16-2004, Fujitsu WiMAX SoC, MB87M3550 a ra mt gii php mang li li nhun cho c cc ng dng trm gc v trm thu bao. SoC c tch hp cao ny b sung iu khin v tuyn MAC,

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    PHY v tt c cc mch tng t cn thit cho cc bng tn c cp php v khng c cp php thch hp.

    Mt s h thng WiMAX trn th trng

    Hng SX

    Alvarion Cambridge broadband

    Navini Redline communication

    Wi-LAN

    H thng

    BeezeAccess OFDM

    VectaStar 3500

    Ripware AN-100 Ligra 3000

    K thut

    FDD FDD TDD TDD/H-FDD

    FDD

    a truy nhp

    CSMA/CA TDMA CDMA a sng mang

    TDMA TDMA

    iu ch

    OFDM,BPSK,QPSK,16QAM,64QAM

    n sng mang QPSK, 16QAM 64QAM

    Thch ng theo chiu xung 16QAM 8QPSK BPSK,Chiu ln QPSK

    OFDM thch ng BPSK,QPSK 16QAM,64QAM

    OFDM,BPS,QPSK 16QAM

    rng bng tn knh(MHz

    2 x 1.75 2 x 3.5

    1.75 3.5 7 14

    3 5

    3.5 7 14

    3.5 7

    Thng lng max

    12 Mbps

    48Mbps xung:4,2Mbps ln:2.2 Mbps

    3.5Mbps 12Mbps

    knh 3.5MHz 14MHz 5MHz 14MHz 7MHz

    ppiuch

    64 QAM 64 QAM 16QAM,QPSK

    64QAM 16QAM

    Nng lng pht x ca BS

    --- 25dBm 29dBm 33.5dBm

    27-47dBm EIRP cho mi phn t antennal

    23 dBm

    22/33dBm (TB/nh)

    Anten khu vc ca BS

    16.5dBi 60

    13.5dBi 60

    360 hoc 120

    17dBi 60 14dBi 90

    17dBi 60 14dBi 90 13dBi 120 12dBi 180 11dBi omni

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    Nng lng pht x CPE

    ---

    25 dBm 29 dBm 33 dBm

    31 dBm EIRP

    15 dBm 17/27 dBm (TB/nh)

    Antennal CPE

    18 dBi 20

    16.5dBi 20

    Cho pht thay i 2dBi 360 6dBi 120

    18dBi 15 24dBi 8

    18dBi 20 21dBi 12 23dBi 9.6

    Giao din pha BS

    10/100BaseT

    STM-1 T1,ATM/IMA 10/100 BaseT

    T1/E1 10/100BasseT

    10/100BaseT

    Giao din pha CPE

    10/100BaseT

    10/100BaseT G.703,E1,V35,STM-1

    USB 10BaseT

    T1/E1 10/100BaseT

    10/100BaseT

    Bng 8 : Thit b h thng trn th trng

    Fujitsu WiMAX SoC, MB87M3400 l mt b x l di tn c s tn hiu hn hp gia hai lp MAC v PHY c tch hp hon ton mang li li nhun cho cc ng dng truy nhp khng dy bng rng. SoC ny c thit k h tr di tn t 2GHz n 11GHz trong c hai bng tn cp php v khng cp php. B x l h tr tt c cc bng tn c sn t 1.75MHz n 20MHz. WiMAX SoC ca Fujitsu hon ton tun theo chun IEEE 802.16-2004 ca WiMAX v c th c cu hnh c s dng trong c hai ng dng trm thu bao v trm gc.

    SoC ny h tr cc lc iu ch thch ng hiu sut cao bao gm 64QAM, 16QAM, QPSK v BPSK. Khi p dng iu ch 64QAM vo mt knh 20MHz v s dng tt c 192 sng mang con, tc d liu ca SoC c th ln ti 75Mbps. Knh con ha ng ln cng c h tr nh c nh ngha trong chun. Vic nng cao hiu nng c th c thc hin vi hai ng c RISC c gn vo SoC. Hai b x ny l khng ch hp dn v vic s dng cc chc nng c bn c yu cu bi c tnh k thut WiMAX nhng cng cho php khong trng thm vo s dng phn mm ng dng ca ngi dng.

    MiTAC Technology, ng u th gii v my tnh c nhn, mng v cc sn phm truyn thng, gii thiu mt trm gc trong nh da trn Fujitsu MB87M3400. Trm thu bao trong nh ny hon ton tun theo cc chun IEEE 802.16-2004 v ETSI HiperMAN, h tr nh tuyn mng, truy nhp khng dy bng rng trn c s WiMAX v VoIP. c kt ni vi mt trm gc WiMAX s dng lin kt v tuyn 3.5GHz pht thoi tc cao, d liu v a phng tin, Trm thu bao kt hp vi mt anten di vi ty chn ca mt anten bn ngoi, cung cp linh hot cao nht.

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    Aperto Networks, mt nh cung cp h thng WiMAX hng u phc v hn 200 nh khai thc 65 quc gia,. Thit b WiMAX ca cng ty s c a ra th trng l dng sn phm PM500, phn cn lica h PacketMAX. Cc sn phm ny trong mt series, c trng ca chng l s ci tin hin i nht v chip, v tuyn v cc cng ngh anten s l phng tin truy nhp khng dy bng rng ca nhiu loi dch v nh video, thoi, d liu gm c VoIP.

    Thit b silicon WIMAX th h tip theo ca tp on Intel, tn m l Rosedale2, c la chn bi 10 nh cung cp thit b WiMAX hng u th gii nhm a ra nhng gii php th h mi cho cc mng WiMAX. Rosedale 2 l mt thit b h thng trn mt chip c chi ph thp v h tr cc chun IEEE 802.16-2004 v IEEE 802.16e-2005, cho php to ra cc modem WiMAX s dng cho c mng di ng ln c nh.

    Rosedale2 s tn dng li th ca cc mng WIMAX di ng ang c trin khai rng ri trn th gii bi cc nh cung cp c s h tng nh Alcatel. Nm trong chng trnh cng tc m rng nhm y nhanh tc trin khai cc mng WiMAX di ng, Rosedale2 l mt phn ca Chng trnh kim tra tng thch (Interoperability Testing) ton cu ca Alcatel.

    Cc thit b s dng Rosedale2 do vy c k vng l s tng thch khng gii hn vi gii php Universal WiMAX (802.16e-2005) ca Alcatel vn h tr v cn bn cc m hnh s dng di ng, bn di ng v c nh. Ngoi ra, tt c cc khch hng hin ti ca gii php c nh m Intel a ra trc y, modem khng dy Intel PRO/ Wireless 5116 (tn m l Rosedale), gm Airspan Networks, Alvarion, Aperto Networks, Axcelera Broadband Wireless, Proxim Wireless, Redline Communications, Siemens Home and Office Communication Devices v SR Telecom u c k hoch a ra cc gii php WiMAX s dng Rosedale2. Do tng thch hon ton v chn cm vi modem khng dy Intel PRO/Wireless 5116, Rosedale2 s mang li mt kh nng nng cp d dng cho cc khch hng.

    Intel cam kt hp tc vi cc khch hng ca mnh nhm a ra cc gii php truy cp Internet khng dy tc cao d dng hn v hiu qu hn v chi ph thng qua vic s dng mng WiMAX. Vi kh nng h tr hai ch mng ca Rosedale2, Intel hy vng s gip y nhanh tc trin khai cc mng WiMAX.

    Rosedale2 c kh nng h tr mng di ng v c thit k nhm cho php cc nh sn xut thit b pht trin cc sn phm modem ca mnh t cc ng dng c nh sang cc ng dng di ng ch vi mt thao tc nng cp phn mm n gin. Vi cc thit b s dng Rosedale2, cc nh cung cp dch v c th la chn ngay lp tc vic trin khai mt mng WiMAX di ng hay trin khai mt mng WiMAX c nh cho thi im hin ti ri sau c th d dng v hiu qu nng cp ln mng di ng.

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    Rosedale2 l mt s b sung mi cho h sn phm rt c ch i ca Intel v cc gii php WiMAX di ng gm mt thit b PC card h tr WiMAX di ng v mt thit b radio Wi-Fi/WiMAX a bng tn vi mt chip duy nht, tn m l Ofer

    1/2006 T chc WiMAX Forum chnh thc chng nhn mt s thit b theo thng s IEEE 802.16-2004 (chun cho php trin khai cc mng Internet khng dy din rng) trong t mt.Nhng thit b ny bao gm phn cng ca Aperto Networks (M), Redline Communications (Canada) v Sequans Communications (Php). Tt c cc sn phm ny hot ng trn bng tn 3,5 GHz ti rt nhiu nc trn th gii, nhng khng c s dng ti M.

    Cc nh sn xut thit b s c kh nng bt u bng cch ngh mt s kt hp ca thit b tt nht i vi nhiu nh khai thc v thit b vng dn c ngoi tri m c th c to khung bn pha nh hay mt cn h. Vi s pht trin ca 802.16e, cc dch v WiMAX cui cng c th c sn sang cho cc thit b mang xch/ c cng nh my tnh xch tay, in thoi thng minh v cc PDA cng nh cc h thng hng hi, t v cc thit b phi truyn thng khc m c th to ra vic s dng mt kt ni Internet di ng.

    Ngy 11/10/2006 Intel cng b Chip WiMAX h tr WiMAX di ng u tin trn th gii. S c mt ca Intel WiMAX Connection 2250, mt h thng trn mt chip th h tip theo ca Intel c xem l mt bc tin cc k quan trng ca cng ngh WiMAX di ng .

    Intel cn pht trin c mt con chip silicon WiMAX vi tn m Baxter Peak dnh ring cho cc thit b di ng. Cui nm ngoi, hng in thoi s 1 th gii Nokia tng tuyn b s s dng Baxter Peak trong dng my tablet N-Series xut xng nm 2008 ca hng.

    21/5/2007, b phn Fujitsu Microelectronics America (M) cng b mu silicon di ng u tin ca hng ny trn sn phm chip WiMAX mi vi hiu sut vt tri so vi cc sn phm i th khc.

    Sn phm c tn l MB86K21 802.16e, p ng y cc yu cu ca chng nhn WiMAX Forum Wave 2.

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    Con chip WiMAX ny h tr knh bng thng t 5-10MHz, c trang b mt lot cc ch module iu hp, tnh nng bo mt tch hp sn, h tr USB 2.0 v giao din Card Bus / PCI.

    D kin nhng sn phm chip hon thin u tin s c gii thiu ti th trng chu , v tip sau l M. Fujitsu cng s cung cp gi thit k h thng Systems Design Kit v gi cp pht nn tng tham chiu PC Card (PC Card Reference Platform Delivery Kit) khch hng c th d dng lm quen vi sn phm.

    4/ 2008 Nokia gii thiu N810 s l mt trong nhng thit b di ng u tin trn th trng c thit k ring cho cng ngh mng khng dy tc cao Wi-Max. .Nokia vn trang b cho N810 cng ngh Wi-Fi tch hp.

    Theo d kin, cc mu PC Siu di ng da trn nn tng Menlow do nhng thng hiu nh Asus, BenQ v Lenovo sn xut s c trng by ti CES nm nay(2008), sau chnh thc xut xng trong 6 thng u nm.

    Th h tip theo ca ca Menlow s l Moorestown, d kin trnh lng vo nm 2009

    Nu nh nm 2007 mi c mt s sn phm ri rc dnh cho WiMAX th nm 2008 c d bo s c bc tin nhy vt vi 100 sn phm (khng tnh cc thit b in t tiu dng v cc thit b c ci t sn).

    Hin Motorola ang trin khai WiMAX vi s hp tc vi cc lin minh vin thng hng u v cc hp ng hp tc vi cc cng ty vin thng hng u. Motorola c chn dng bi Wateen Pakistan, v Agni Bangladesh trin khai WiMAX trn ton quc.

    Motorola hin c mt s hp ng thng mi trin khai WiMAX trn ton th gii v hng lot cc cuc th nghim ang din tra trn khp khu vc chu Thi Bnh Dng

    WiMAX di ng mi l trin vng ln nht ca WiMAX. Vi cng ngh ny, ngi dng u cui c th c s dng Internet tc cao ln n 1Mbps, ti bt k ni no trong vng ph sng bn knh rng nhiu km. Thit b u cui ca dch v WiMAX di ng c th l cc card PCMCIA, USB, hoc c tch hp sn vo trong con chip my tnh (kiu nh cng ngh Centrino ca Intel).

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    Cng theo d bo ca WiMAX Forum, nm 2009 s c 180 sn phm dnh cho WiMAX,nm 1010 l 290 sn phm, v nm 2011 l 430 sn phm.

    D kin vo qu 2 ny s c nhng sn phm cng ngh u tin c chng nhn h tr cng ngh WiMAX di ng.

    3.1.3 Di ph hot ng ca WiMAX trn mt s nc hin nay

    a/ Ph khng cp php

    Australia c mt s nh cung cp ang yu cu s dng cc cng ngh da trn chun 802.16. Ban u tp trung vo bng ph cp php 5.8GHz. Australia khng c ph khng cp php. i vi cc dch v truy nhp khng dy WAS, cc

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    nh iu tit a ra mt s cc bng tn ph c sn di cc tha thun giy php khc nhau.

    Vi ph 2.4GHz v 5.8GHz, cc bng ny c to ra cho WAS theo iu khon ca giy php loi mt. iu ny cung cp mt mi trng iu tit public park. Nhng ngi dng tip nhn khng m bo s bo v khi nhiu t cc dch v khc v phi khng gy ra nhiu cho cc dch v khc. Cc thit b gim kh nng gy ra nhiu bi v thit k ca chng v cng sut b hn ch. Giy php loi mt khng c s dng cho cc c nhn ring l v khng phi tr chi ph cho giy php.

    Ti o bng 2.4GHz l c sn do. Tuy nhin, vo thi im ny n cha c bit n nu WiMAX thc hin giao din khng gian hay khng. Bng 5.8GHz nc ny hin ang khng c sn.

    Canada, cc bng 2.4GHz v 5.8GHz c th c s dng cho WiMAX. Cng nghip Canada khng c ph c ch nh cho cc cng ngh c th, nh WiMAX, nhng WiMAX c th c s dng bt k bng tn no, nhng ph hp vi nhng hn ch cng ngh

    Php, theo l thuyt c th s dng cc cng ngh WiMAX trong bng tn 2.4GHz (bng 6.8GHz khng c cng khai Php). Tuy nhin, c th c nhiu kh khn trong thc t do nhng hn ch v cng sut c a ra bi PIRE v chun ETSI.

    Nht, hin nay MIC khng cp pht ph cho WiMAX nhng hin nay c mt y ban nghin cu ang nghin cu MAN khng dy.

    Hn Quc khng bt buc chun ha cng ngh cho iu kin khng dy v do khng c cc quy tc ring qun l vic s dng WiMAX trong cc bng tn khng cp php.

    Thy in, bng tn 2.4GHz c m cho cc loi cng ngh khc nhau v mt h thng WiMAX s c cho php vi iu kin n tham gia vo ETSI EN 300 328 V1.5.1. Bng tn 5.470-5.7625GHz ni chung l c sn cho cc h thng da trn WiMAX vi iu kin chng hon thnh cc yu cu bt k. Bu in Thy in v i l Telecom quyt nh a ra bng 5.725-5.875GHZ cho vic s dng BWA, ph hp vi iu kin khng cp php.

    M c th hot ng trong cc bng tn khng cp php vi iu kin cc thit b p ng cc yu cu vn hnh v k thut theo cc nguyn tc Part 15 p dng cho bng tn c th m n ang hot ng.

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    Mehico, cc nh khai thc khng c php s dng cc cng ngh WiMAX trong cc bng ph khng cp php. Hin nay, cc bng 2.4 v 5.8GHz l khng cp php Mehico.

    b/ Ph cp php

    Australia, c ph d phng cho WAS apparatus-licensed v WAS spectrum licensed. Khng c ph ring c d phng cho cng ngh WiMAX. Tuy nhin, cc giy php ph c ch nh bi chuyn gia mi trng v truyn thng Australia trung lp v cng ngh v th cc dch v WiMAX c th thch hp vi cc bng 2.3GHz v 3.4GHz. Ph trong cc bng 2.3GHz v 3.5GHz c gi bi mt s cc nh khai thc.

    Ti o, cng ngh 3.5GHz l trung lp v th WiMAX c th c s dng bi cc giy php.

    Canada, cc bng 2.3, 2.5 v 3.5GHz c th c s dng cho WiMAX. Cng nghip Canada khng c ph c ch nh cho cc cng ngh c th, nh WiMAX, nhng WiMAX c th c s dng bt k bng no ph hp vi cc hn ch cng ngh. Do , cc bng khc c th sn c cho WiMAX trong tng lai khi cng ngh v cc chun pht trin.

    Php, Cc bng tn cho WiMAX bao gm 3.4-3.8GHz. Phn ph ny c a ra trong khi cc phn khc ang trong qu trnh pht hnh.

    Nht, cc bng 4.9 v 5.0GHz l c sn cho cc h thng truy nhp khng dy bao gm WiMAX.

    Mehico khng c cc bng tn cp php cho WiMAX trong di 2.3 hay 3.5GHz.

    Vng quc Anh, chi tit v cc bng ph m Ofcom s a ra th trng c lit k trong K hoach b sung c cu t chc ph. Trong di 3.4-4.0GHz c hai giy php c truy cp cho ph, Pipex v UK Broadband hin nay u ang s dng cc thit b WiMAX. Ch rng Ofcom s a ra ph sn c m khng c nhng p buc cng ngh v do truy nhp n cc bng s khng phi tun theo mt chun giao din khng gian c th (nh WiMAX), v th cc bng WiMAX c th c s dng bi cc chun giao din khng gian khc.

    M, giy php c quyt nh trong cc bng 2.3GHz v 2.5GHz c th c s dng bi WiMAX tng thch hoc cc cng ngh khc m s dng cc cng ngh tin WiMAX (pre-WiMAX) hin ang c lp t. Bng 3.4-3.6GHz s khng sn c cho WiMAX M. Tuy nhin, bng 3.650-3.700GHz hin nay

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    c n nh cho cc dch v di ng v c nh. V th, FCC lp k hoch bn 90MHZ 1.7-2.1GHz, ci ny c th c s dng mt cch ng tin cy bi cc ngi dnh c giy php cung cp cc dch v thng qua WiMAX nu nh cc chun cng nghip c sa i cho php hot ng di 2GHz.

    c/ Cc giy php c tha nhn

    Australia, ngi nm gi ch yu ph trong bng 2.3GHz l Austar (2302- 2400MHZ), y l mt nh cung cp Pay TV, nhng hin nay khng s dng ph ny. Telstra v Unwired Australia gi mt lng ng k ph Australia trong bng tn ny. Unwired gi ph bao ph pha ng v pha nam b bin Australia, vng ny chim 95% dn c Australia. Personal Broadband Australia gi mt giy php ph trong bng 1900-1920MHz, mc d n s dng cng ngh iBurst v khng phi IEEE 802.16.

    Canada, cc giy php c quyt nh cho cc h thng truy nhp khng dy trong cc bng 2.3, 2.5 v 3.5GHz. Ph trong bng 2.3 v 3.5GHz c bn trong nm 2004 v 2005. Tng s c 32 cng ty c quyt nh 841 giy php. Ph trong bng 2.5GHz xuyn sut hu ht Canada c quyt nh vo 2000. Nhng ngi nm gi giy php bao gm Inuksuk, SaskTel v MAnitoba School Board. Nhng ngi nm gi giy php khc trong bng tn ny bao gm: Look TV, Image Wireless v Skycable c cp quyn cung cp cc dch v phn phi a im v cc phng tin truy cp Internet hn ch. Cc giy php c yu cu thm tnh mm do v chnh sch ny hin nay vn ang c xem xt.

    Php, ch c mt giy php c quyt nh cho Altitude Telecom. Ph c cp pht trn nn tng n trc c phc v trc.

    Nht, s lng giy php khng hn ch cho cc bng 4.9/5.0GHz do cc bng ny phi chia s gia cc nh khai thc s dng mt chc nng cm nhn sng mang.

    Hn Quc, cc dch v vin thng da trn iu kin thun li yu cu mt

    giy php ca nh nc v KT, STK v Hanaro Telecom c thng qua giy php cho cc dch v WiBro 2.3GHz vo thng 3, 2005.

    Hungary c nm nh khai thc c th s dng cc h thng FWA bao gm WiMAX trn c s ca cc giy php ton quc trong cc bng 3410-3494MHz v 3510-3594MHz.

    trn l tnh hnh ca mt s quc gia tiu biu trn th gii v vic trin khai v qun l WiMAX, ngoi ra cn nhiu quc gia khc

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    3.1.4 Kt qu trin khai

    19/03/2008 Motorola thng bo th nghim thnh cng d n WiMAX di ng ti Thi Lan cng vi hng i l Thng tin Hp nht (UIH)

    y l mc nh du cuc th nghim thnh cng u tin trong s rt nhiu d n th nghim WiMAX di ng ca Motorola Thi Lan v cng l mc quan trng trong vic pht trin WiMAX trn ton cu ca Motorola. UIH c U ban Vin thng Quc gia ca Thi Lan (NTC) cp php th nghim WiMAX vo nm ngoi v tin hnh mt s th nghim nhm nh gi kh nng phn lung WiMAX ti Bangkok v Phuket. Qua cc cuc th nghim ny, UIH tri nghim y cc tnh nng di ng khng gii hn ca cc gii php WiMAX di ng ca Motorola.

    Vi cng ngh WiMAX ca Motorola, cc nh cung cp dch v bng thng rng s c th em n cc dch v bng thng rng khng dy c nhn tt hn cho cc ng dng nh VPN, gii tr trc tuyn, xem video trc tuyn, gi in qua Internet v chi game trc tuyn. Motorola hin ang c 19 hp ng WiMAX v 77 d n WiMAX ti 44 nc trn ton th gii.

    Ti thi im ny, s ngi s dng WiMAX ti chu l hn 2 triu ngi, v M l hn 3 triu ngi, nhng trong vng 2 cho n 5 nm na, con s ny s tng vt ln, v d tnh s t khong hn 60 triu ngi dng WiMAX vo nm 2012.

    Theo T chc WiMAX Forum, hin c hn 260 cc d n lin quan ti WiMAX c trin khai ti 110 quc gia v khu vc. Kt qu l khong 4 t ngi trn ton cu hin nay c c hi tip cn WiMAX trong khi cng ngh ny ang dn c hon thin v s tr thnh cng ngh kt ni khng dy tc cao ch cht trong thi gian ti.

    Trong khi , th trng thit b sn phm dnh cho WiMAX ang rt si ng vi s gp mt ca nhiu i gia cng ngh trn th gii nh Intel, Motorola, Nokia, Samsung, Alvarion, Alcatel-Lucent, AT&T, Sprint

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    D on ca WiMAX Forum s ngi s dng WiMAX theo khu vc (n v triu ngi

    Vng 2007 2008 2009 2010 2011 2012

    Bc M 2,61 4,03 6,25 9,59 14,79 22,62

    M 0,66 1,18 2,14 3,92 7,17 12,97

    Chu - TBD 1,39 2,84 5,99 12,96 28,17 60,45

    Chu u 1,35 2,34 4,09 7,08 12,23 21,01 Chu phi/Trung ng 0,30 0,65 1,46 3,32 7,50 16,60

    Tng cng 6,32 11,04 19,91 36,88 69,87 133,66 Bng 9 D on v ngi dng WiMAX theo khu vc

    Chu s l trung tm ca WiMAX l nhn nh ca Tin s Ferrie Hu, Gim c t chc WiMAX Forum khu vc ng Nam , ti Hi ngh WiMAX hin ti v tng lai din ra (4/4/2008) H Ni.

    3.2 Kh nng trin khai WiMAX ti Vit Nam:

    3.2.1 c im ca Vit Nam

    Cu trc a hnh a dng v phc tp 3/4 lnh th l i ni.1/4 lnh th l ng bng, nhiu sng sui v c hng ngn o ln nh nm ri rc t Bc n Nam .i ni him tr, dc cao, phn ct mnh, rt kh khn trong xy dng c s h tng trin khai mng cp.

    Ngoi cc thnh ph v nhng khu trung tm,nhng khu vc cn li do c im t dn, dn c phn b tha tht hoc kinh t khong pht trin,nn tng h tng cha c (ng i li kh khn,c bit mt s ni cha c in) nn hu nh cha c loi hnh truy nhp bng rng no c trin khai.Do khi trin khai cbt k loi hnh cng ngh no ti y cng phi xy dng t u nn vn u t ban u b ra l rt ln nhng hiu qu v kinh t khng cao thm tr hu nh khng c.

    Tuy nhin ti cc thnh ph v cc trung tm th tp trung hu ht c s h tng x hi v k thut, dn c ng c, kinh t pht trin. nhu cu v ng truyn bng rng ln v pht trin nhanh,Tuy nhin nhng khu vc ny cc loi hnh truy nhp bng rng nh ADSL,WiFi .. kh pht trin.vic trin khai WiMAX i ng ti nhng vng ny t ra thch hp hn.

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    T nhng c th , ta thy c nhng thun li v kh khn khi trin khai WiMAX l:

    3.2.2 Nhng thun li :

    - Chnh sch rng m ca nh nc nhm khuyn khch v pht trin cng ngh thng tin Vit Nam.

    - Th trng VN nhn chung rt si ng v pht trin rt nhanh. Nhu cu dng internet ca ngi dn cng ngy cng tng cao. Nhu cu truyn thng tc cao l rt ln.

    - Nc ta c nhiu loi a hnh phc tp nhiu i ni sng sui,hi o rt kh khn trong vic trin khai mng cp vi u th ca mnh WiMAX t ra rt ph hp.

    - Cc nh cung cp dch v nh Viettel,VNPT c th tn dng c s h tng cc trn BTS ca mng mobile trin khai trn khp c nc.

    3.2.3 Nhng kh khn

    Do kh nng linh hot ca WiMAX l nguyn nhn khin cho vic chun ho thit b kh ng nht dn ti ch th sn sut thit b hng lot nn gi thnh thit b cn kh cao v cha tng thch, Mt khc,hu ht cc hng cung cp thit b vin thng ln (Alcatel, Siemens, Motorola) hin nay c xu hng u t nghin cu sn xut thit b theo hng WiMAX di ng chun 802.16e. Trong khi , Vit Nam cc doanh nghip li th nghim WiMAX chun d, ti tn s 3.3 GHz. Cho nn, s lng i tc c thit b th nghim rt t ,Vit Nam phi t hng ring vi hng ALvarion do nu trin khai rng vi m hnh trn th gi thnh s cao. gii quyt vn ny chng ta c th chn di tn khc hoc thit b ca cc hng khc cho ph hp.

    Kh nng ca WiMAX l truyn xa n c nhng vng ho lnh.vng hi o Nhng mt dn tha v nhu cu truy nhp bng rng tc cao cha ln t ngi s dng. Tnh kh thi v mt kinh t thp.

    Cc chuyn gia nhn nh, nm 2008 s l nm ca WiMAX ti Vit Nam vi cc li th v chnh sch, cng ngh, v s quan tm ca nhiu tp on cng ngh ln ca ton cu nh Motorola, Intel Tp ch cng ngh trc tuyn ITBusinessEdge trong mt bi nhn nh cui nm 2007 cho bit Vit Nam s l tm im ca WiMAX t nm 2008

    m bo cc yu t hiu qu v chi ph, ch tiu vng ph sng v dung lng h thng., cn cn c nhiu tiu ch nh gi da trn nhng s c v tnh ph bin, mc chun ha ca cng ngh i vi c thit b mng v thit b u

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    cui. Sau khi phn tch, nh gi cc vn lin quan n vic trin khai th nghim WiMAX ti Vit Nam,

    cc chuyn gia c mt s xut sau:

    V phin bn WiMAX, cn la chn trin khai l chun 802.16e v c nhiu nh sn xut sn sng cung cp thit b, m bo kh nng m rng, nng cp trong giai on pht trin sau, to ra mt h thng ng b, tit kim chi ph mua sm thit b v ti nguyn tn s, trin khai c nhiu dch v cao cp, h tr di ng

    V tn s hot ng ca WiMAX, la chn u tin l bng tn 2,5 GHz. Bng tn ny c th quy hoch cho WiMAX m khng nh hng n cc mng khc. C th xem xt bng 3,5 GHz l la chn tip theo.

    V phm vi trin khai WiMAX, nn da trn nhu cu ca tng vng, nhng thnh ph ln nh: H Ni, thnh ph H Ch Minh, Hi Phng, Nng cung cp cc dch v truy nhp v tuyn bng rng nh video, data, hoc thit lp cc ng truyn dn a Internet n nhng vng su, vng xa, min ni, hi o - ni c nhiu kh khn trong xy dng cc ng truyn dn hu tuyn.

    Mc d Vit Nam cha th thng mi ha cng ngh WiMAX v ngi dn cha th hng li g t cng ngh ny, nhng gii truyn thng trn th gii ni v Vit Nam nh con chim u n v trin khai WiMAX. Ti hng lot cc cuc trin lm ln trn th gii nh 3GSM Ty Ban Nha, 3G Hong Kong, Communic 2007 Singapore, Vit Nam c nh gi nh l ngi sao sng trn bn WiMAX th gii

    3.3 Tnh hnh trin khai th nghim WiMAX Vit Nam

    3.3.1 Tnh hnh chung

    Hin Vit Nam c bn doanh nghip c B Bu chnh Vin thng cp php th nghim dch v WiMAX l

    - Tp on bu chnh vin thng VNPT (th nghim c WiMAX c nh Fixed v di ng Mobile),

    - Tng cng ty truyn thng a phng tin VTC (tp trung vo dch v hnh, v d IPTV),

    - Tng cng ty vin thng qun i Viettel (WiMAX di ng) v - Cng ty c phn vin thng FPT Telecom. FPT ng k c Fixed v Mobile

    WiMAX nhng do chi ph trin khai tn km, i tng ban u ca cng ty ny s l nhng khch hng c thu nhp cao.

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    WiMAX vi th mnh l ph sng Internet rng, khng cn c vo a hnh bng phng hay him tr, nn rt ph hp cho vic ph cp Internet bng thng rng ti mi min t nc, k c cc vng su, vng xa ca Vit Nam.

    WiMAX cng c coi l cng ngh l tng cho ton b khu vc ng Nam , gip cc nc trong khu vc thc hin cc mc tiu cp thit nh: Chnh ph in t, Pht trin gio dc v y t, Pht trin nng nghip...vi hai loi hnh: WiMAX c nh (Fixed WiMAX) v WiMAX di ng (Mobile WiMAX),.

    15/02/2006 :Th tng Chnh ph c cng vn chnh thc cho php ba doanh nghip c cung cp dch v WiMAX di ng v c nh. l VNPT, FPT Telecom, v VTC.

    20/03/2006 WiMAX: bn doanh nghip l VNPT, FPT Telecom, VTC v Viettel c B Bu chnh Vin thng ra quyt nh cp php th nghim cung cp dch v WiMAX c nh (fixed WiMAX).di tn dnh cho dch v WiMAX c nh t 3.3GHz n 3.4GHz, vi tiu chun IEEE802.16d c ITU thng qua nm 2004. Thi gian cc doanh nghip c php th nghim dch v s l mt nm. Sau khi ht thi gian th nghim, B Bu chnh Vin thng s tip tc xem xt c th cp php cho doanh nghip no chnh thc c cung cp dch v.

    04/2006 Tp on Bu chnh Vin thng Vit Nam VNPT v mt s DOANH NGHIP vin thng khc ang trong giai on tch cc trin khai th nghim cng ngh WiMAX ti 5 tnh thnh l H Ni, Nng, TP.HCM, Lo Cai v Bc Ninh.

    Doanh nghp ch lc trc tip th nghim dch v ny l cng ty in ton v Truyn s liu VDC (thuc VNPT). Hin ti, VDC ang hp tc vi cng ty Intel kho st mt bng v lp t thit b ti Lo Cai. Khong hai thng na, dch v s bt u cung cp th nghim ra bn ngoi. Theo k hoch, vic cung cp th nghim s din ra trong vng 1 nm i vi cc thit b c nh.

    Theo VDC, kh khn u tin l vic la chn thit b hp chun v tn s cp php. y l cng ngh mi khng ch Vit Nam m c trn th gii. Hin ti, trn th gii, cng ngh WiMAX cn ang rt mi m v mi ch c hng Intel trin khai cy ghp chp WiMAX trong cc thit b ca mnh trong chng trnh ABC.

    V pha FPT Telecom, lnh o DOANH NGHIP ny cho bit, FPT s cung cp c hai dng l mobile WiMAX v fixed WiMAX di tn 2.3 Ghz v 3.3 Ghz. Hin FPT Telecom ang trong giai on la chn thit b v th nghim k thut v nghin cu cc d n tin th nghim.

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    Trong khi , Viettel Internet s th nghim cng ngh Mobile WiMAX v cng ngh WiMAX c nh c nhiu hng th nghim thnh cng. i din doanh nghip ny cho rng, vic u t cho WiMAX s r hn u t cho ADSL rt nhiu nn gi c dch v ny sau khi chnh thc cung cp s mc chp nhn c.

    21/6/2007 Motorola v VDC (thuc Tp on Bu chnh Vin thng VNPT) k mt tho thun trin khai th nghim WiMAX k thut v thng mi ti H Ni v thnh ph H Ch Minh. Vic th nghim ny s din ra trong vng mt nm, VNPT c th nghim WiMAX di ng ti bng tn 2,5-2,69 GHz. Cc h thng ang c th nghim ti H Ni, Nng, thnh ph H Ch Minh, Lo Cai v Bc Ninh.

    VNPT: vic trin khai c chia lm 2 giai on

    Giai on 1: (10/2006-9/2007)

    - VNPT kt hp vi VDC v Intel th nghim WiMAX c nh chun 802.16d-2004

    - Di tn 3.3 GHz - Th nghim ti Lo Cai Vi 19 im i a hnh khc nhau

    Giai on 2 (bt u t 10/2007)

    D n hin cng c trin khai .bn T Van (x T Van), cch th trn gn nht l Sapa hn 9 km, c a hnh i ni him tr khin vic lp cp kt ni Internet kh khn. Ton b khu vc ny gn nh khng c ph sng in thoi di ng v ch c hai ng in thoi PSTN. Hin thi, mt v tinh IPSTAR c s dng thit lp kt ni Internet tc 2 Mb/giy - 512 Kb/giy, lin kt vi trm gc WiMAX tn s 3,3 GHz.

    Trm gc ny dng mt ng-ten kt ni a im ph sng ti cc im th nghim ti T Van.:11 v tr c ph sng bao gm trm y t, im bu in - vn ha x, trng hc, mt h nng dn, tr s Hi ng nhn dn v mt s nh tr cho khch du lch. Kh nng kt ni Internet tc cao i km cc dch v nh VoIP Vi tc ng truyn t c mc 4-5 Mb/s, cht lng truy cp Internet cng nh cc dch v khc (hi ngh truyn hnh, in thoi...) l rt kh quan.

    Theo nh gi ca cc chuyn gia, nu vic th nghim WiMAX ti T Van thnh cng, s l mt m hnh kh thi cho Qu dch v vin thng cng ch v nhng d n vin thng nng thn trong tng lai.

    VNPT cng angth nghim WiMAX di ng trn a bn cc thnh ph ln nh H Ni v TP HCM vi 3 trm gc kt ni PMP ti 30-50 im u cui.Sau 2

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    giai on th nghim VNPT kt lun WiMAX c nh sn sang trin khai thc t vi bt k a im vng su vng xa no

    Viettel : chia lm 2 giai on

    Giai on 1: (8/2006-9/2006)

    - Viettel kt hp vi Motorola v PlametComm th nghim WiMAX c nh theo chun 802.16d bng tn 3.3 GHz

    - Trin khai th nghim trn trm BTS cung cp dch v trn 10 khch hng.

    Giai on 2 : (bt u t 10/2006 )

    - Viettel kt hp vi NextNet v Alvarion triienr khai th nghim WiMAX c nh trn a bn H Ni.

    - Trin khai vi 10 BTS cung cp dch v cho 72 khch hng - Bn knh 2 km vi ng truyn NLOS v 32 km vi ng truyn LOS

    Kt qu thu c l kh tt Viettel vi u th c s h tng trm BTS ca mng Viettel mobile ang bao ph khp c nc cung cp WiMAX trong tng lai.

    VTC:

    - Nm 2006 VTC kt hp vi Alvarion(Israel) trin khai WiMAX c nh ti H Ni.

    - Th nghim trn 3 nhm dch v: truy cp internet,dch v a phng tin v thoi IP

    - 3 trm pht t ti: Lc Trung,Vn H,Hm Long thuc a bn H Ni - Bng tn 2.3 GHz rng gii tn s 30MHz - Sau 1 nm th nghim VTC khng nh : - Vi 3 loi dch v th nghim l :truy nhp internet.VoD,VoIP cho cht lng

    tt,d trin khai v n nh - Kh nng bao ph rng ca WiMAX lm cho s trm pht ca WiMAX =1/3

    s trm ca 3G v t hn nhiu ln so vi s lng trm ca mng di ng GSm hay CDMA

    - VTC vn ang tip tc th nghim ti H Ni , Nng v TPHCM v hng ti th nghim WiMAX di dng

    FPT:

    FPT telecom th nghim fixed WiMAX vi 1 trm BTS v 8 thit b u cui theo chun 802.16d

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    - Hin nay FPT telecom ang hng ti th nghim c 2 m hnh mobile WiMAX (2.3GHz) v fixed WiMAX (3.3GHz)

    FPT Telecom cho bit: h thng VoD v IPTV ca FPT chy trn nn WiMAX rt tt,hnh nh khng b git,chi game trc tuyn khng b dng hnh v c bit vi VoIP m thanh rt tt khng b can nhiu..tuy nhin FPT khng a ra cc s liu k thut c th.

    3.3.2Trin khai thc t

    M hnh 1: Trin khaiWiMAX ti Lo Cai

    hnh 17: M hnh trin khai WiMAX ti Lo Cai

    Lo Cai l mt tnh min ni cao, st bin gii Trung Quc. TP. Lo Cai c mt a bn phc tp, sng Hng chy qua trong lng thnh ph. Bn cnh Lo Cai c xem nh l mt trong nhng tnh i u trong c nc v ng dng CNTT vo vic vn hnh ca h thng chnh quyn cng nh trong cuc sng ca ngi dn. Vic la chn TP. Lo Cai th nghim trin khai nhm mc ch nh gi kh nng trin khai cng ngh WiMAX ti nhng a bn phc tp, nhiu i ni sng sui.

    D n th nghim WiMAX c trin khai ti Lo Cai l kt qu ca s hp tc gia Tp on Bu chnh Vin thng Vit Nam (VNPT), i din l cng ty in

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    ton v Truyn s liu VDC), Tp on Intel v c quan h tr pht trin quc t hoa k (USAID) cng trin khai cng ngh bng thng rng khng dy th h mi ti vng su vng xa ca Vit Nam. Ti a phng c hai n v tham gia h tr trin khai d n l Bu in tnh Lo Cai (n v thnh vin ca VNPT) v trung tm CNTT tnh Lo Cai (LCIT)

    Nhng ng dng cng ngh khng dy bng rng th h mi s c cung cp th im trong 6 thng (t thng 7 n thng 12), trong s dng mt trm pht chnh v khong 20 trm kt ni dn dng.

    Intel, Cng ty in ton v truyn s liu (VDC) cng C quan hp tc pht trin quc t Hoa K ti Vit Nam (USAID) s hp tc vi nhau trong d n ko di 8 thng v cng ngh bng rng khng dy c nh c s dng l Fixed WiMAX 802.16 - 2004 Rev.d vi tn s 3,3 GHz - 3,4 GHz.

    C 18 a im ti Lo Cai c la chn tham gia th nghim gm 6 trng hc, mt s c s y t, im bu in vn ho x, y ban x, doanh nghip va v nh v mt gia nh nng dn cha tng tip xc vi cng ngh hin i. Cc dch v c a vo th nghim l thoi v Internet tc cao.

    D n c tng chi ph khong 500.000 - 600.000 USD, trong USAID h tr 250.000 USD. Theo nh cung cp dch v, cc chng trnh khc cng ang trong giai on lp k hoch s dng v tinh kt ni, m rng WiMAX n nhng vng xa kh n bng ng b.

    PHNG N THC HIN

    Vic th nghim c tin hnh trn hai lnh vc. Truy nhp Internet tc cao da trn mng WiMAX v ng dng gi in thoi qua giao thc IP.

    a/La chn tn s v thit b WiMAX

    - La chn tn s:VNPT c MPT cho php th nghim trong khong:

    on bng tn th nht: 3335.5-3342.5MHz. on bng tn th hai: 3365.5-3392.5MHz.

    - Phng thc song cng: FDD hoc TDD. - Theo ti liu ca thit b c la chn th nghim (Alvarion-BreezeMAX

    3000) v cn c vo gii tn s VNPT c cp, d n th nghim WiMAX la chn thit b hot ng trong gii tn s nh sau:

    Band F: Tx=3331-3335MHz; Rx=3381-3400Mhz

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    rng knh truyn: 3.5MHz Phng thc song cng: FDD

    L do la chn thit b WiMAX

    La chn th nghim thit b ca hng Alvarion c thng hiu BreezeMAX (theo khuyn ngh ca Intel v kinh nghim ca VDC).

    BreezeMAX, v mt thng mi ra i t 2004, c trin khai bi hn 130 nh khai thc trong hn 30 quc gia. BreezeMAX l gii php WiMAX thng mi c chng minh cao cp nht v ln u tin a ra CPE c trang b chip WiMAX giao din bng rng Intel PRO/Wireless 5116.

    c xy dng t nn tng da trn chun IEEE 802.16-2004, BreezeMAX h tr cc dch v c nh, mang xch v di ng vi mt ng truyn tt cho cng ngh di ng WiMAX ni bt da trn chun IEEE 802.16e. BreezeMAX c thit k cho nhiu tn s trong c cc bng tn cp php v khng cp php t 2GHz n 6GHz v hot ng c hai ch song cng FDD v TDD.

    H thng vi nhy rt cao v cng ngh v tuyn OFDM ng u th trng, mnh hot ng trong cc iu kin knh truyn bt li v ng truyn khng tm nhn thng. Vi cng sut cao c h tr phn tp v cc cng ngh anten thng minh, BreezeMAX cho php s dng cc CPE t lp t trong nh trong c cc mi trng thnh th ng c v vng ven thnh th.

    Cc CPE BreezeMAX c trang b b chip PRO/Wireless 5116 ca Intel v pht cc dch v truy nhp bng rng n mt phm vi rng cc khch hng bao gm vng dn c, cc ta nh v vn phng nh, cc doanh nghip ln...vv

    Bng 10 Cu hnh h thng c trin khai ti Lao Cai

    Thit b S lng

    - M t

    Trm gc

    Trm gc Indoor Model: BMAX-MBST-IDU-2CH-3.3

    01 - Loi BTS nh t trong nh - C 2 knh (3.3 GHz) - Ngun nui AC - Dung lng gii hn :20 CPE

    Trm gc Outdoor Model: BMAX-BST-AU-ODU-3.3f

    01 - Loi BTS v tuyn ngoi tri - Bng tn 3.3GHz c ng kt ni

    vi antennal - Rx on 3381-3400 ,Tx on 3331-3350

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    Antennal BST Model:Omni ANT3.3-3.5

    01 - Tn s :3.3 -3.5 GHz - ng kt ni u female, tng ch

    10 dB Thit b u cui

    SU indoor Model :BMAX-CPE-IDU-1D

    20 - Thit b kt ni trong nh - H tr cng kt ni d liu loi 10/10

    BaseT SU outdoor Model :BMAX-PRO-SA-3.3

    20

    - CPE v tuyn Pro t ngoi tri tch hp antennal

    - Rx on 3381-3400 ,Tx 3331-3350 - Kh nng cung cp dch v:thoi

    ,data v WiFi hostport

    Thit b qun l

    My ch NMS Model :BreeezeLITE

    01 - My server ca h thng

    b/ S trin khai thc hin tng th

    Hnh 18 :S trin khai ti Lo Cai

    H thng trm gc WiMAX c lp t trn ct anten ca Bu in tnh Lo Cai. Ti y, im truy nhp WiMAX c cp mt ng ADSL vi tc 8Mbps t POP ca VDC ti Lo Cai. H thng cn c mt NMS Server chy phn mm BreezeLITE qun l v gim st cc CPE. Mt Voice Gatway chuyn lu lng VoIP n mng PSTN v ngc li.

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    Tn hiu IP sau khi i qua im truy nhp WiMAX s c chuyn i thnh tn hiu sng v truyn n cc CPE. Cc CPE sau khi nhn c tn hiu sng WiMAX s chuyn i thnh tn hiu IP v cung cp truy nhp Internet cho cc PC v cc ng dng da trn Internet nh VoIP.

    Cc v tr lp t thc t

    - Trm gc BTS t ti phng tng i bu in thnh ph Lo Cai - Antennal BTS lp ti ct antennal bu in TP Lo Cai - Cc trm u cui (SU) :lp ti cc v tr trong thnh ph

    Stt V tr Khong cch n ct antennal bu in(km)

    1 Trung tn cng ngh thng tin tnh Lo Cai 1 2 Trng PTTH s I TP Lo Cai 0.5 3 Trng THPT chuyn Lo Cai 2 4 H nng n phng Bc Cng 2.5 5 Cng ty u t xy dng cc cng trnh 3 6 im truy cp internet 1.5 7 S bu chnh vin thng 1 8 Khch sn Hoa Vinh 0.2 9 Qun caf WiFi 0.2 10 Trng THCS L Qu n 1.5 11 Trng chuyn cp II Ng Vn S 2 12 Trng THCS Vn Hoa 4.7 13 Trm y t x Vn Hoa 5 14 Trm y t phng Bc Cng 3 15 Trung tm y t TP Lo Cai 2.5 16 Bu in Lo Cai 0 17 Bu in vn ha x Vn Hoa 4.5

    Bng 11 cc v tr t thit b ti Lo Cai

    c/ Trin khai ti trm gc (BS) - cao anten t cao 80m ti ct anten bu in tnh. - di khong 200m

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    Hnh 19 :S kt ni trm gc BS

    - Cc cng vic thc hin: Lp t anten ca BTS trn cao 80m trn ct anten. Lp t dy tn hiu vo phng my. m bo h thng ngun UPS. Ci t ng trung k Internet cho trm BTS, phi hp thc hin

    gia cc bn. Ci t h thng Mail server. Ci t h thng VoIP. Ci t h thng NMS.

    d/ Trin khai ti u cui

    - Ti mi im u cui, thit b cho ngi dng s gm hai phn:

    - Khi ngoi tri: Anten lp ngoi tri, hng v thp anten ca Bu in Tnh.Anten ny c th nm trong tm nhn thng LOS hoc khng trong tm nhn thngNLOS. Ngoi ra, ngun nui cho thit b ngoi tri c a qua ng cp tn hiu CAT5 nn kh thun tin cho vic lp t.

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    - Khi trong nh: c t trong nh ca ngi dng u cui. Thit b ny c chc nng nh mt Router. Thit b ngoi tri v thit b trong nh s c kt ni vi nhau bng mt dy cp truyn tn hiu in (theo chun CAT5). Thit b trong nh s c ni vi mt Switch v sau s c ni ti my tnh v thit b in thoi VoIP.

    e/ Phng n trin khai ng dng VoIP

    ng dng VoIP s c th nghim trin khai mt cch c lp vi cc thit b ca mng truyn dn WiMAX. Vic ng dng VoIP c trin khai mt cch c lp c ngha quan trng vi l do: Khi WiMAX c trin khai thnh dch v th cc WiMAX CPE s do cc nh sn xut thit b khc nhau sn xut, nu ph thuc thit b th s rt kh cung cp cc dch v gi tr gia tng trn nn WiMAX nh VoIP.

    V m hnh ng dng th mi u cui s c trang b mt hoc mt vi in thoi IP hoc in thoi cm tay IP. Cc my in thoi ny c nh s ni b v c th gi ln nhau. Khi cc my in thoi IP thc hin cuc gi n mt thu bao PSTN th s bm mt s m rng sau bm s cn gi. Khi cc thu bao t PSTN, di ng mun gi n cc in thoi IP ny th trc ht cn quay s n mt trong hai ng c kt ni vi Voice Gatway, sau bm s in thoi IP cn gi.

    C ch lm vic ca mng VoIP trong d n th nghim ny nh sau:

    Ti VDC s t mt SIP Server (phn mm v thit b phn cng do USAID trang b),SIP Server c nhim v trao i tn hiu cuc gi v qun l cc thu bao in thoi IP. Phn mm ny c cung cp vi giy php s dng trong mt nm.

    Khi cc in thoi IP mun gi ln nhau hoc mun gi ra mng PSTN th u truy nhp n SIP Server bit c a ch IP ca ch n, sau hai thit b gi v c gi s lm vic trc tip ln nhau thng qua giao thc RTP theo m hnh ngang cp.

    S lng thu bao VoIP khng qu 40 thu bao. S lng ng thoi kt ni ti mng PSTN l hai ng. Cc ng PSTN lm trung k c cu hnh ch cho php s dng cho cc cuc gi ni tnh trong Lo Cai c hai chiu

    Bn cnh thit b in thoi IP SIP, trong d n ny cng s tin hnh th nghim my in thoi cm tay WiFi VoIP. y l thit b cm tay, kt ni ti mt im truy nhp WiFi thit lp cuc gi VoIP. V ng dng VoIP l ng dng nhy cm v thi gian nn vic p dng c cng ngh WiMAX v WiFi chy ng dng

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    ny l mt c hi tt th nghim tch hp cng ngh thoi qua cc kt ni khng dy.

    Hnh 20 :S kt ni cho ng dng VoIP

    e/ Kt qu th nghim WiMAX ti Lo Cai

    Kh nng bao ph ca mng: Cc u cui ca d n c trin khai trong bn knh 5km xung quanh trm gc BTS, tuy nhin kt qu o kim h thng do Vin Khoa hc K thut Bu in tin hnh cho thy mng hot ng tt trm vi ba Cam ng vi khong cch 9,5km.

    Tnh c ng: H thng WiMAX Lo Cai c kch thc nh gn, rt d dng cho vic lp t v bo tr, bo hnh. Cc thit b WiMAX ch dng ngun in thng thng, rt thun tin cho vic trin khai v vn hnh

    Kh nng qun l ca mng: H thng WiMAX c ni vi mt Server c th qun l c vic truy nhp vo ra ca cc SU. H thng qun l c chc nng qui nh cc mc cht lng v lu lng khc nhau cho tng SU.

    nh gi chung v hot ng ca h thng WiMAX:

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    - H thng c lp t v hot ng kh n nh - Cc thit b khch hng CPE (Customer Premises Equipment) c lp t

    hin ti u nm trong tm nhn thng nn c cng sut thu c ln. Khi hot ng tc cao CPE v BS c th s dng cc kiu iu ch tc cao nh QAM16, QAM 64 vi t l li cm thp.

    - Tc download, upload d liu ln p ng c cc yu cu dnh v Internet. H thng WiMAX c kh nng cung cp truy nhp tc i ti a ln n 10 Mbps theo thit k v trong thc t t c 4-5 Mbps trong qu trnh th thit b. Cc thu bao trong d n c cung cp mc dch v khc nhau tu vo ng dng ti tng a im th nghim, vi tc ti a khc nhau t 512 Kbps ti 4Mbps, hoc l cam kt v thi gian tr t nht vi thu bao thin v ng dng VoIP nh ti nh ng Vng Trung Thn.

    Khong cch gia CPE v BS (Base Station):

    - Trong iu kin tm nhn thng (LOS): tn hiu vn thu c vi khong cch gia CPE v BS ln ti 9.5 km v c th ln hn.

    - Trong iu kin tm nhn khng thng (NLOS): kh nng hot ng ca h thng ty thuc vo a hnh, a vt gia CPE v BS. H thng hot ng c vi khong cch 2.2km v c th ln hn.

    - Anten ca CPE l anten nh hng nn SU ch thu tt vi nhng v tr ph hp. Ti cng v tr t SU cc gc khc nhau, cng sut thu, t l li bit BER ca CPE khc nhau.

    H thng in thoi VoIP trn nn WiMAX:

    i vi cht lng thoi VoIP trn nn Cng ngh WiMAX, theo kho st ca Vin khoa hc K thut Bu in, VDC v Bu in tnh Lo Cai v Trung tm CNTT tnh Lo Cai cng nh ngi s dng nh gi th cht lng dch v VoIP trn nn cng ngh WiMAX l rt tt, m thanh r rng, khng c ting vng, khng c hin tng v ting.

    Cc thu bao VoIP t ti B-VHX Vn Ho, mt x vng su vng xa l hot ng nhiu nht, phc v cho nhu cu ca nhng h dn ca x ny. Trung bnh mi ngy ti y pht sinh hn 10 cuc gi. Nhng ngi dn xung quanh y cha c iu kin trang b cc thu bao in thoi PSTN cng nh rt ngho, nn h thng ca th nghim pht huy tc dng rt tt ti im ny.

    Cc in thoi VoIP thc hin nhiu cuc gi nht l ti cc im Bu in Lo Cai, B-VHX Vn Ha, Khch sn Hoa Vinh, Trng THCS L Qu n, Trng chuyn cp 2 Ng Vn S, Trm y t x Bc Cng v h nng dn Vng Trung Thn.

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    Cc im B-VHX, im truy nhp Internet cng cng, cc trng hc, trm y t x v cc h dn l nhng im th nghim ht sc thnh cng, nhu cu s dng Internet v in thoi VoIP qua h thng WiMAX ti nhng a im th nghim ny rt ln. Cc c quan chnh quyn do c sn in thoi PSTN nn nhu cu s dng in thoi VoIP trong thc t cha ln nh mong mun.

    Do l cng ngh khng dy nn vic trin khai h thng din ra mt cch nhanh chng, nht l nhng vng su vng xa, nhng ni m vic ko cp vin thng l ht sc kh khn. Ton b thi gian trin khai ti trm gc v 10 im u cui ch din ra trong vng 1 tun. C cu t ti Lo Cai thng hay din ra st l t th u im khng dy cng th hin r hn.

    M hnh 2 Trin khai WiMAX ti H Ni ca Viettel (bt u 10/2006)

    Hnh 21 :M hnh trin khaivwimax ca Viettel

    - Thit b ca hang Acatel (Alvarion) v Motorola (NextNet) c th l:

    - Khu vc trin khai : ni thnh H Ni vi m hnh im a im - Quy m :10 trm tng ng vi 7 im pht sng(1 im pht ti Ng 35

    Ni Trc t 2 trm v ti im 16 pho i Lng t 3 trm ) ph rng trn cc qun ni thnh.

    Hng SX Base Station CPE (indoor) CPE (outdoor)

    CPE mobility

    NextNet 8 40 6 6 Alvarion 2 0 20 0

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    - Dung lng :kh nng phc v ca trm l 3000 khch hng (hin ti th nghim trn 72 khch hng l doanh nghip ,vn phng,h gia nh v qun internet cng cng)

    a/Tnh nng ca cc loi thit b

    Thit b u cui trong nh:

    - C tch hp modem v radio - Ngun nui: in th 110/220V - Tc ti a 10Mbps (download v upload) - Gn nh d s dng - Phm vi hot ng 32 km vi LOS v 2km vi NLOS - Khng cn cu hnh phn mm - Ch truy nhp 24/24 - Tc truy nhp n nh trong ton vng ph sng. - iu ch linh hot 4/16/64 QAM - Tng thch vi nhiu thit b mng chn ph thng (nh 802.11) - Thch ghp cho h gia nh hoc vn phng nh

    Thit b u cui ngoi tri

    - Kt ni khe cm RJ-45 , Ngun nui: in th 110/220V ,c gn thit b chng st

    - C tch hp modem v radio - Tc ti a 10Mbps (download v upload) - Phm vi hot ng 32 km vi LOS v 2km vi NLOS - D dng gn trn tng hoc trn ct,chu thi tit: tt - iu ch linh hot 4/16/64 QAM - Thch ghp cho doanh nghip ,khu ng dn c ,thnh th

    Thit b u cui di ng

    - Tc truy nhp 3Mbps/450Kbp (download/upload)ti v tr tnh; 1Mbps/156Kbps (download/upload)khi di chuyn

    - Tc di chuyn ti a 100 km/h - Phm vi hot ng 32 km vi LOS v 2km vi NLOS - C tch hp modem v radio - Cng sut ln ph hp vi mi iu kin mi trng - Thch hp vi cc loi phng tin giao thng

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    - Ch truy nhp 24/24 - Khng cn cu b ci ring bit. - iu ch linh hot 4/16/64 QAM

    b/ trin khai v cu hnh thit b

    - Cu hnh vi 8 thit b ca NextNet - Tn s 3.3 GHz , rng knh 3.5MHz - Tc d h tr 10Mbps/sector - Gc m ca antennal 90 /secter - Cng ngh TDD - Cng sut ca BaseStation :33dBm (2 watts) - tng ch ca CPE: - RSU :13.4 dBi - OSU 13.4dBi - MSU:ph thuc vo v tr ca thit b - Cc knh tn s s dng: 3344.75 - 3348.24 - 3394.75 v 3398.25 (MHz)

    Cu hnh vi 8 thit b ca Alvarion

    - Tx=3343MHz , Rx=3393 MHz - Bng thng s dng l:2*7MHz - Cng ngh TDD - Cng sut ca BaseStation :30dBm (1 watt) - S secter l 1/1 trm - S knh tn s : 1 tn s /1 sector - Tc d h tr 18Mbps/sector - Gc m ca antennal 90 /secter - Gc ngng ca anten :-5

    Bng 12 v tr v cu hnh chi tit cc thit b th nghim ca Viettel

    Stt Tn trm

    V tr S trm

    Li anten

    Cu hnh

    1

    HNI101 Khu tp th i hc THy Li

    1 sector

    Tn s : F1=2348.25MHz Gc lch anten (so vi hng bc):320 Gc nghing :-3 cao anten: 30m

    2 HNI34 Ng 35 2 sector BS1

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    0 Ni Trc Tn s : F1=3348.25MHz Gc lch anten (so vi hng bc):1400 Gc nghing :-2 cao anten: trn 30m BS2 Tn s : F1=3394.75MHz Gc lch anten (so vi hng bc):220 Gc nghing :-2 cao anten: 60m

    3 HNI28 16 pho i Lng

    3 Sector BS1 Tn s : F=3348.25MHz Gc lch anten (so vi hng bc):160 Gc nghing :-5 cao anten: 60m BS2 Tn s : F=3394.75MHz Gc lch anten (so vi hng bc):320 Gc nghing :-4 cao anten: 60m BS3 (thit b ca Alvarion) Tn s : Tx=3343MHz ,Rx=3393MHz Gc lch anten (so vi hng bc):120 Gc nghing :-4 cao anten: 60m

    4 HNI08 S 8 Trng Thi

    1 Sector Tn s : F=3344.75MHz Gc lch anten (so vi hng bc):320 Gc nghing :-3 cao anten: 30m

    5 HNI86 Ng Dch Vng

    1 sector Tn s : F=3344.75MHz Gc lch anten (so vi hng bc):90 Gc nghing :-4 cao anten: 30m

    6 HNI306

    S 20 ng 515

    1 Sector Tn s : F=3398.25MHz Gc lch anten (so vi hng

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    Hong Hoa Thm

    bc):140 Gc nghing :-2 cao anten: 30m

    7 HNI85 Thn ng Xun nh

    1 omni (thit b ca Alvarion) Tn s : Tx=3343MHz ,Rx=3393MHz Tn s : F1=2348.25MHz Gc lch anten (so vi hng bc):360 cao anten: 30m

    c/ cc dch v th nghim

    Viettel yu cu m bo cht lng tt trn cc thit vi cc dch v:

    - VoIP - Video Conference - Multimedia Streaming - Truy cp internet tc cao - Mobility

    d/ kt qu thu c

    Cc ch tiu v cng ngh

    Cch thc nh gi:

    - o ti giao din mng:o lu lng (MRTG).o d tr - o drive test:s dng MS o cht lng tn hiu ,tc d liu ti nhiu khu

    vc c a hnh khc nhau - o cc thng s v tuyn nh: nhy, nhiu ng knh,nhiu knh lin

    k,cng sut pht ti cc trm gc v cc trm thu bao - o cc thng s h thong nh thng lng, tr gi tin - o cc c tnh ca h thng :kh nng t iu chnh cng sut pht hng

    ln v hng xung,cht lng QoS

    Sau y l nhng s liu c th

    Cc thng s Gi tr

    Tham s v

    S lng cell/sector 19 Tn s hot ng 2500MHz

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    BS v MS

    Phng thc truyn TDD

    Bng thng knh 10MHz

    Khong cch gi cc BS 2.8 km

    Khong cch ti thiu ga cc BS v cc thit b mobile

    36m

    M hnh antennal 70(-3dB 20dBfront-back)

    cao BS 32m

    cao MS 1.5m

    li anten BS 15dBi

    li anten MS -1dBI

    Cng sut pht ti a ca BS 43dBm

    Cng sut pht ti a ca mobile 23dBm

    S anten thu pht ca 1 BS Tx:2 hoc4, Rx 2 hoc 4

    S anten thu pht ca 1 MS Tx :1 ;Rx:2

    Tham s nhiu BS 4dB

    Tham s nhiu MS 7dB

    Qu cng sut Trm gc

    Cng sut pht ca mi anten 10W

    S anten 2

    tng ch kt hi Cyclic 3dB

    tng ch ca anten pht 15dBi

    tng ch pilot -0.7dB

    EIRP 57.3dBm

    S lng sng mang con c s dng 840

    Cng sut ca sng mang con c s dng 28.1dBm

    Thit b Tng ch anten thu -1 dBi

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    u cui

    Tng ch phn tp thu 3dB

    Nhiu thu 7dB

    d tr fading

    Fading a ng 5.56dB

    Fading nhanh 6.0dB

    D tr nhiu 2dB

    Xuy hao xuyn m 10db

    Tng d tr fading 23,56dB

    nhy my thu

    Tp m nhit 174dBm/Hz

    Khong cch sng mang con 10.94KHz

    Kiu iu ch QPSK1/8

    SNR yu cu -3.31dB

    Phm vi khong cch gii hn 0.82

    nhy thu (cho mi sng mang con) -129.9dBm

    nhy thu tng hp -100.7dBm

    Tng ch h thng 160dB

    Suy hao ng trun ti a cho php 136.4dB

    Bng 13: Kt qu s liu sau th nghin thu c ca Viettel

    - Vi NLOS vi khong cch 2-3 km tc c th t 3Mbps/1Mbps (down/up)

    - Trong iu kin thi tit xu v nhiu ca cc loi sng v tuyn khc :cht lng dch v vn m bo.

    - Vi tiu tr dung lng trm: tp trung ngn 30 thit b u cui ti 1 ta nh, cho hot ng lin tc, ngay ti gi cao im WiMAX vn cho cht lng tt v khng xy ra tc nghn

    Nhn xt:

    C 4 cng ty th nghim cng ngh WiMAX ti Vit Nam u c c im chung nh:

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    - Cc dch v cung cp m doanh nghip cung cp cha phong ph .Cc dch v th nghim ch yu l dch v VoIP ni mng v truy nhp Internet v tuyn.

    - Cha c h thng qun l, tnh cc - M hnh th nghim ca nh nn vic nh gi thc s cht lng cha hon

    ton chnh xc, S lng trm thu pht cn t nn hn ch kh nng ph sng, do th nghim cha thc s nh gi c tim nng v cc vn pht sinh khc khi trin khai h thng trn din rng

    - Tt c cc doanh nghip ny u c su hng mun trin khai m hnh WiMAX i ng.

    Qua thi gian th nghim VNPT cho rng, cng ngh WiMAX c nh cho kt qu tt v sn sng a vo trin khai trong thc t v d dng trin khai mt cch nhanh chng cho bt k a im vng su vng xa no.Tuy nhin trc tnh hnh pht trin ca WiMAX di dng v su hng ca cc nh sn xut thi b cng nh nhu cu ca th trng. Do Vit Nam phi cn nhc nn trin khai loi WiMAX no cho ph hp.

    Kt lun

    WiMAX l cng ngh c nhiu u im ni tri nh: Bng thng rng,c ly truyn xa (trong mi c 2 mi trng LOS v NLOS), t ng iu chnh thch nghiv v..do c th s dng hiu qu trong cc mi trng a hnh phc tp,b che chn trong mng truy nhp bng rng

    Thc t c nhiu ro cn t ra cho vic em cng ngh WiMAX vo Vit Nam nh gi thit b ,bng tn ,tnh kinh t.Cc dch v th nghim cho kt qu tt nhng cha thc s nh gi c tim nng tht ca h thng.

    WiMAX l cng ngh mi,cha c m hnh thng mi thnh cng no trc y Do vy, Vit Nam xem xt nhiu yu t nh lu lng thng tin, s lng thu bao tng khu vc trong vic quyt nh trin khai WiMAX, m bo n u c cng ngh, nhng khng trin khai qu rng ri khi cha thc s hiu qu.

    Qua chng ny ta cng thy r nhng thun li v kh khn khi trin khai rng ri WiMAX ti Vit Nam.Da vo nhng g tm hiu c th thy rng WiMAX l mt cng ngh rt ph hp vi c imca Vit Nam.

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    Tng Kt

    Bn kha lun ny nu mt cch tng qut v cc cng ngh truy nhp

    bng rng .Vi phn tm hiu v cu trc mng v nhng k thut c h tr trong

    h thng WIMAX ta thy c c s cho nhng nhng c tnh u vit ca h

    thng.Qua nhng tm hiu s lc ta thy cng ngh WiMAX l mt cng ngh c

    nhiu u im nht hin nay .

    Lun vn cng khi qut tnh hnh pht trin v cng ngh v thit b cng

    vi nhng kt qu t c trong trin khai th nghim cng ngh ny trn th

    gii v Vit Nam.vi nhng c th ring ca Vit Nam ta thy c nhng thun

    li v kh khn khi p dng v trin khai rng ri cng ngh ny.

    y l cng ngh cn ang trong giai on th nghim khng ch ca Vit

    Nam m trn ton th gii do cc thit b cho cng ngh ny cha c sn xut

    hng lot v gi thnh thit b cn kh cao.Nhng v mt k thut ta thy WiMAX

    s dng nhng cng ngh k thut tin tin nht hin nay v ang tng bc

    c hon thin vic chun ha.Nu phi la chn mt cng ngh th WiMAX l

    mt cng ngh tt nht trin khai mng truy nhp bng rng tc cao trn c

    nc.

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    Ti liu tham kho

    [1] Bo co trin khai cung cp truy nhp Internet, a dch v cho cc vng nng thn, vng xa VNPT thng 11 nm 2006 -2007

    [2] Bi ging CNG NGH WIMAX-Nguyn Vit Hng Hc vin CNBCVT

    [3] Cc ngun t liu, s liu thng k ca B KHT, Tng cc Thng k.

    [4] Kt qu nghin cu khoa hc v cng ngh - Vin KHKT Bu in- nh xut bn bu in 2007

    [5] Lun vn thc s - Nguyn Th Oanh-2006 m s :2.07.00 .H Quc Gia H Ni

    [6] Fixed, Nomadic, Portable and Mobile Applications for 802.16-2004 and 802.16e WIMAX networks. WiMAX Forum

    [7] IEEE 802.11 Working Group (2007-06-12). IEEE 802.11-2007: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. ISBN 0-7381-5656-9.

    [8] IEEE 802.16-2004.IEEE October 2004, IEEE 802.16e-2005.IEEE 28February 2006

    [9] Michel D Gallaher (2005),Alliance for telecommunication industry solution board directs meeting.

    [10] SR Telecoms. White paper 2004 [4]. Can WIMAX address your Application? WiMAX Forum

    [11]. WiMAX Introduction. Magaret LaBrecque April 10th, 2003

    [12]Website :www.vnpt.com.vn/tapchibcvt

    [13] Website :www.WiMAXforum.org

    [14] Website :http://en.wikipedia.org/wiki/HIPERLAN#cite_ref-hiperlan_0-0

    [15] Website :ttp://vntelecom.org/diendan/showthread.php?t=25

    [16] Website:http://www.vnmedia.vn/ShowCat.asp?CatId=279 (VnMedia - Cng ngh - Chuyn WiMAX)