cấu trúc Wimax

7/29/2019 cu trc Wimax

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mng WiMAX


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Cu trc phn lp

V cu trc phn lp, h thng WIMAX c phn chia thnh 4 lp:

Lp con tip ng (Convergence)Lp iu khin truy nhp (MAC layer)

Lp truyn dn (Transmission)

Lp vt l (Physical)


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Cu trc mng WiMAX

1. Tng vt l PHY

Physical layer inh nghia cac c tinh vt ly cua giao din , nh cac thit bi kt

ni, nhng vn lin quan n in nh in ap ai din la cac s nhi phn , cc

kha cnh chc nng nh ci t , bo tr v tho d cac ni kt vt ly. Cc giao


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din ca tng vt ly gm EIA RS -232 v RS-499, k tha cua RS-232. RS-449

cho phep khoang cach cp ni di hn . H thng LAN (Local Network Area:

mng cc b) ph bin la Ethernet , Token Ring, v FDDI (Fiber Distributed Data

Interface).Lp vt l (PHY) c 802.16 nh ngha c ba bin th:

Sng mang n

OFDM 256

OFDMA 2048.

OFDM 256 V OFDMA 2048 s dng di bng tn 2-11 ghz.

Chun c thit k h trcho cphng thc song cng theo thi gian (Time

Division Duplex - TDD) v song cng theo tn s (Frequency Division Duplex -

FDD) cho vic phn chia truyn dn hng ln v hng xung. TDD, ti

ng ln v ng xung dng chung mt knh nhng khng truyn cng lc v

FDD, ti ng ln v ng xung hot ng trong nhng knh ring bit.

Gia PHY v MAC l mt lp con hi t truyn Transmission. Lp ny thc

hin s bin i cc PDU (protocol data units) gia 2 lp.

2. Lp kim sot truy cp MAC

Lp MAC 802.16 c thit k h trng dng im-a im da trn

CSMA/CA (Collision Sense Multiple Access with Collision Avoidance). MAC AP

802.16 qun l ti nguyn UL, DL v gm lun c chc nng nh thi truyn v

nhn.

Lp MAC cn c mt s chc nng h trng dng din rng m tnh di ngkhng n nh nh tch hp dch vdi ng: bnh chn tc thi (realtime Polling

Service) v khng tc thi (non-realtime Polling Service)...; ng gi/phn mnh

tng hiu qu s dng bng tn; Qun l kha ring t (PKM-privacy key

management) bo mt t lp MAC; H trpht a lung; Chuyn mch tc


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cao; Qun l nng lng. PKM phin bn 2 cn c khnng kt hp vi giao thc

xc thc mrng (EAP-Extensible Authentication Protocol).

MAC bao gm nhng lp con quy t chuyn bit v dch v giao din vi nhng

lp cao hn, pha trn lp con phn chung (common part) MAC nng ct thc hinnhng chc nng MAC ch yu. Bn di lp con phn chung l lp con bo mt

(security sublayer).

3. Lp con phn chung (common part sublayer

Cung cp cc chc nng chnh ca MAC bao gm

Chc nng truy nhp

Phn bbng thng

Thit lp

Qun l kt ni.Strao i thng tin gia cc trm gc (Base Station - BS) v trm thu bao

(Subcriber Station - SS) trong mt vng a l theo cc kin trc: imim

(Point to Point), ima im (Point to MultiPoint) v kin trc kt hp

(Mesh).


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4. Lp con bo mt (security sublayer)

Cung cp cc c ch chng thc, trao i kha v m ha. Lp con bo mt cung

cp c chiu khin truy nhp tin cy, m bo an ton d liu trn ng

truyn, khc phc vic truy cp tri php cc dch v bng vic m ha cc lungdch v.

Lp con tip ng (Convergence) lm nhim v giao din gia lp a truy cp v

cc lp trn.


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WiMAX c cnh tranh vi Wi-Fi?


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WiMAX v Wi-Fi s cng tn ti v tr thnh nhng cng ngh b sung ngy

cng ln cho cc ng dng ring. c trng ca WiMAX l khng thay th Wi-Fi.

Hn th WiMAX b sung cho Wi-Fi bng cch m rng phm vi ca Wi-Fi v

mang li nhng thc t ca ngi s dng "kiu Wi-Fi" trn mt quy m a lrng hn. Cng ngh Wi-Fi c thit k v ti u cho cc mng ni b (LAN),

trong khi WiMAX cthit k v ti u cho cc mng thnh ph (MAN). Trong

khong thi gian t 2006 - 2008, c 802.16 v 802.11 xut hin trong cc thit b

ngi s dng t laptop ti cc PDA, c 2 chun ny cho php kt ni v tuyn

trc tip ti ngi s dng - ti gia nh, trong vn phng v khi ang di chuyn.

WiMAX c cnh tranh vi HiperMAN ca ETSI?

Cc chun 802.16-2004 (256 OFDM PHY) ca IEEE v HiperMAN ca ETSI

s chia s chungcc c tnh k thut PHY v MAC. Din n WiMAX hot ng

chai t chc tiu chun ny m bo mt chun ton cu chung cho MAN

v tuyn, s c chp nhn.

Skhc nhau gia wimax v WCDMA

-) WCDMA s dng bng tn 1900Mhz - 22000Mhz , cn wimax s dng bng

tn tng thch vi h thng vi ba (2Ghz - 10Ghz ) Di ny mi s dng v

(11Ghz - 60Ghz ) ==> vi bng tn khc nhau nhiu nh vy th r dng cc thit

bu cui n phi khc nhau rt ln .

-)Khc nhau pp a truy nhp v tuyn ( khc nhau c bn v vn v tuyn ) :

Vi WCDMA s dng pp a truy nhp phn chia theo m CDMA ( song cng

FDD) , trong khi Wimax l s dng pp a truy nhp TDMA ( song cng c thigian v tn s) + pp a truy nhp tn s trc giao OFDMA ( nhm gip nng cao

hiu qu s dng ph tn )

-) khc nhau vphng thc iu ch

-) vng ph sng ca Wimax rng hn rt nhiu t ti 10 Km


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-)Khc nhau v tc truyn s liu : WCDMA ch c tht tc ti a 2

Mbit/s trong khi Wimax c tht ti 70Mbit/s

-) hin nay cc thit bu cui ca WCDMA ch yu l cc thit bin thoi di

ng , trong khi Wimax li l cc chic my tnh dng truy cp cc dch vnhinternet ....

Nhng ng dng no dnh cho cng ngh WiMAX?

Cng ngh WiMAX l gii php cho nhiu loi ng dng bng rng tc cao

cng thi imvi 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 cpbng rng c nh nhng vng xa xi, ho lnh, nht

l khi khong cch l qu ln i vi DS: 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 gametrc 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 ninhcao). 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 tnhxch 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 thngln hn v cho cc mng Wi-Fi nh cung cp kt ni bngrng cc khu vc ln hn.

Ti sao WiMAX li cn thit? Ti sao WiMAX li quan trng cho v

tuyn bng rng cnh v v tuyn bng rng ding?


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WiMAX cn thit v l mt cng ngh c lp cho php truy cp bng rng c

nh v di ng.

Chun WiMAX l cn thit t mc tiu chi ph thp hn. y l iu m cc

gii php vtuyn c quyn khng th t c do nhng hn ch v s lng.Cc gii php WiMAX c kh nng tng thch cho php gim bt chi ph sn

xut nh vic tch hp cc chip chun, lm cho cc sn phm c Din n

WiMAX chng nhn c chi ph hp l cung cp cc dch v bng rng cng

sut cao nhng khong cch bao ph ln trong cc mi trng Tm nhn thng

(LOS) v khng theo tm nhn thng(NLOS). y l iu kh thi i vi WiMAX

nh c s h tr mnh m ca ngnh cng nghip thng qua Din n WiMAX

vi hn 350 thnh vin bao gm cc nhcung cp thit b, cc nh sn xut chip v

cc nh cung cp dch v hng u.

WiMAX quan trng v tuyn bng rng c nh cung cp truy cp bng rngcn thit ticc doanh nghip v ngi s dng l h gia nh nh l mt s thayth cho cc dchv cp v DSL c bit l khi truy cp ti cp ng l rt khkhn.

WiMAX quan trng trong v tuyn bng rng di ng, v n b sung trn vn

cho 3G v hiu sut truyn d liu lung xung cao hn 1Mbit/s, cho php kt nicc my laptop v PDA v b sung cho Wi-Fi nh bao ph rng hn.

Cc sn phm c Din n WiMAX c li nh th no i vi doanhnghip? v ngi s dng h gia nh?i vi cc doanh nghip, WiMAX cho php truy cp bng rng vi chi ph hpl. V phn lncc doanh nghip s khng c chia thnh khu vc c ngcp, la chn duynht 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 chng li t vic trin khai cc h thng WiMAX chng nhn nh to ra s cnhtranh mi trn th trng, gimgi v cho php cc doanh nghip thit lp mngring ca mnh. iu ny cbit ph hp i vi cc ngnh nh kh t, m,nng nghip, vn ti, xy dng v ccngnh khc nm nhng v tr xa xi, holnh.


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

Nhng dch v g ca WiMAX g s c a ti ngi dng?

WiMAX s cung cp cc kt ni bng rng mi lc mi ni cho mi loi thit b

v trn bt k h thng mng no v d nh :

- Truy cp internet tc cao ti nhng vng ho lnh xa xi.

- V c bn, tng tc truyn d liu cho cc dch v nh l Game Online,

Streaming Video, Video Conferecing, VoIP v cc dch v c bn c xc nh


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khc.

- em n cho thit b Internet khng dy v cc ph truy nhp mt gi c cnh

tranh c th so snh vi cc dch v internet qua Cable, DSL v cp quang.

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