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WiMAX Overview&

Technology

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171 Tng quan v WiMAX

171.1 Gii thiu chung v WiMAX

171.2 S i ln t Wifi n WiMAX

191.3 Hai m hnh ng dng WiMAX

191.3.1 M hnh ng dng c nh (Fixed WiMAX)

201.3.2 M hnh ng dng WiMAX di ng

202 Cc chun trong WiMAX

202.1 Chun IEEE 802.16 - 2001

212.2 Chun IEEE 802.16a

222.3 Chun IEEE 802.16c - 2002

222.4 Chun IEEE 802.16d - 2004

222.5 Chun IEEE 802.16e 2005

233 c im chun 802.16d v 802.16e cho WiMAX c nh v di ng

233.1 Cu trc khung lp PHY

313.1.1 C ch iu khin

333.2 Lp MAC

343.2.1 Service-specific convergence sublayer

343.2.2 MAC common path sublayer_lp con phn chung

413.2.3 Lp con bo mt

463.3 So snh v cc phng thc nng cp t chun 802.16d v 802.16e

463.3.1 So snh

473.3.2 Cc phng thc nng cp

474 Cc k thut c s dng trong WiMAX

474.1 K thut iu ch s

474.1.1 K thut iu ch pha QPSK

494.1.2 K thut iu ch bin cu phng QAM

504.2 K thut iu ch OFDM

544.3 K thut song cng

564.4 K thut a truy nhp

564.4.1 TDMA

564.4.2 OFDMA

634.4.3 Scalable OFDMA (SOFDMA)

644.5 iu ch thch nghi v m ha AMC

664.6 C ch yu cu truyn li t ng ARQ

674.6.1 Kiu ARQ dng v i

684.6.2 Kiu ARQ li N

704.6.3 Kiu ARQ chn lc

714.6.4 Hybrid ARQ

724.7 Phn hi knh nhanh CIQCH

734.8 H tr cht lng dch v QoS

754.9 Dch v lp lch MAC

764.10 Chuyn giao trong WiMAX di ng

794.11 Qun l s di ng v cng sut tiu th

Mc lc hnh nh8Hnh 1.1 M hnh mng WiMAX c nh

14Hnh 3.1 Cu trc khung OFDM dnh cho truyn TDD

15Hnh 3.2 Cu trc khung OFDM dnh cho truyn FDD

18Hnh 3.3 Cu trc khung WiMAX OFDM

19Hnh 3.4 Minh ha khung OFDMA vi cu trc a vng

22Hnh 3.5 M hnh lp PHY v MAC

25Hnh 3.7 nh dng MAC PDU

26Hnh 3.8 Generic MAC header format

27Hnh 3.9 Bandwidth request header

28Hnh 3.10 MAC management messages format

28Hnh 3.11 Ghp MAC PDU

29Hnh 3.12 MAC PDU encryption

31Hnh 3.13 M hnh lp con bo mt

34Hnh 3.14 Giao thc chng thc

36Hnh 4.1 iu ch QPSK

37Hnh 4.2 B bin i ni tip song song

37Hnh 4.3 T hp bit iu ch QPSK

38Hnh 4.4 S khi iu ch QPSK

39Hnh 4.5 S khi phng php iu ch M_QAM

40Hnh 4.6 K thut ghp knh theo tn s trc giao

41Hnh 4.7 Cu trc ca mt k hiu OFDM

43Hnh 4.8 Tin t vng CP v hin tng a ng

44Hnh 4.9 Hai ch song cng TDD v FDD

46Hnh 4.10 Cu trc sng mang con OFDMA

47Hnh 4.11 Knh con ha trong OFDMA

48Hnh 4.12 S to knh trong m hnh FUSH

48Hnh 4.13 Cluster trong m hnh DL PUSH

49Hnh 4.14 Tile trong m hnh UL PUSH

50Hnh 4.15 M hnh AMC

51Hnh 4.16 Nhm cc sng mang con cho mi ngi dng khc nhau

51Hnh 4.17 Cu trc khung cng ngh a truy nhp OFDMA

54Hnh 4.18 iu ch thch nghi v m ha da trn khong cch vi BS

56Hnh 4.19 M hnh giao thc ARQ dng v i

57Hnh 4.20 M hnh giao thc ARQ li N

58Hnh 4.21 Giao thc ARQ li N vi gi tin b li

58Hnh 4.22 Giao thc ARQ li N vi ACK b li

60Hnh 4.23 C ch yu cu lp li khi li xy ra

62Hnh 4.24 H tr QoS WiMAX di ng

66Hnh 4.25 Chuyn giao cng HHO

67Hnh 4.26 Chuyn trm gc nhanh ( FBSS )

68Hnh 4.27 Chuyn giao phn tp MDHO

Mc lc bng biu15Bng 3.1 Thng s nh dng ca DLFP

22Bng 3.2 Mt s bn tin s dng kt ni c s

22Bng 3.3 Mt s bn tin s dng kt ni qun l s cp

31Bng 3.4 Ni dung kha chng thc AK trong PMK version 2

33Bng 3.5 Bng so snh chun 802.16d v 802.16e

51Bng 4.1 Cc tham s t l OFDMA

53Bng 4.2 Tc d liu PHY trong WiMAX di ng

61Bng 4.3 Cc dch v WiMAX v QoS

1 Tng quan v WiMAX1.1 Gii thiu chung v WiMAX

Wimax , tn vit tt ca Worldwide Interoperability for Microwave Access, l h thng truy nhp vi ba c tnh tng tc ton cu da trn c s tiu chun k thut IEEE 802.16-2004. Tiu chun ny do hai t chc quc t a ra: T cng tc 802.16 trong ban tiu chun IEEE 802, v Din n WiMAX. T cng tc IEEE 802.16 l ngi ch nh ra tiu chun; cn Din n WiMAX l ngi trin khai ng dng tiu chun IEEE 802.16. WiMAX l mt cng ngh c tao ra bi s nh hng ca cc thnh phn truyn tin v s trang b ca cc cng ty, n thc y v chng nhn tnh tng thch ca thit b truy nhp bng rng khng dy, n tng thch vi chun IEEE 802.16 v chun ETSI-HIPERMAN. WiMax hot ng gn ging vi Wi-Fi nhng c ci thin kh nhiu c th tng tc truyn dn d liu ti 70 Mbit/s vi phm vi hot ng 2-10 km trong khu vc thnh th v 50 km ti nhng vng ho lnh.

T chc phi li nhun WiMAX bao gm cc cng ty sn xut thit b v linh kin truyn thng hng u th gii ang n lc thc y v xc nhn tnh tng thch v kh nng hot ng tng tc ca thit b truy cp khng dy bng thng rng tun theo chun k thut IEEE 802.16 v tng tc trin khai truy cp khng dy bng thng rng trn ton cu. Do cc chun 802.16 thng c bit n vi ci tn WiMAX.

Cng ngh truy nhp khng dy ang c trin khai ng dng c trin vng nhm b sung cho mng thng tin di ng. Mng Wi-Fi ch yu phc v cho mng cc b LAN, cn WiMAX phc v ch yu cho mng th MAN (Metropolitan Area Network). Mng WiMAX cng nh mng th hu tuyn (truyn dn qua cp) nh mng DSL u c s dng phc v cc thu bao trong vng ti 50km.1.2 S i ln t Wifi n WiMAX

Trn thc t, trong thi gian qua, vi s ra i ca Wifi lm thay i cch thc trao i thng tin ca ngi s dng.Tuy nhin, do Wifi l cng ngh c thit k hng ti cc mng LAN kh dy, chnh v vy trong nhng trng hp c th, khi p dng cng ngh ny cho mng MAN, th n bc l rt nhiu nhng hn ch. Trc ht Wifi c thit k cho mng t thu bao,knh truyn ca n c nh kch thc khong 20Mhz, do vy rt km linh hot. Bn cnh , Wifi khng h tr kin trc Mesh, mt kin trc m bo s lin thng tt trong mng th.Hn na, nu ta truyn trong mi trng tt, t nhiu, tm nhn thng ( LOS ), dng cc Anten nh hng vi cng sut ln th Wifi cng ch t ti khong cch vi km, rt hn ch cho vic ph song trong mt pham vi ln

S ra i ca Wimax khc phc c nhng nhc im trn ca Wifi. Hin nay, Wimax c xem l mt gii php ton din ca cng ngh khng dy bng rng trong th, ngoi v nhng vng nng thn xa xi ho lnh Wimax cho php truyn khng dy cc loi d liu, hnh nh, m thanh nhanh hn c DSL hay cp, v tt nhin l nhanh hn nhiu ln cc cng ngh khng dy hin hnh nh 802.11a hay 802.11b m khng yu cu iu kin truyn thng.

WiMAX l mng khng dy ph sng mt vng rng ln, thun tin cho vic trin khai mng nhanh, thun li v c li ch kinh t cao so vi vic ko cp, c bit l vng c a hnh phc tp. V vy, mng truy nhp khng dy bng rng WiMAX s p ng c cc chng trnh ph cp Internet cc vng su, vng xa, ni c mt dn c tha. i vi cc vng mt dn c va phi (ngoi vi cc thnh ph ln ni i hi cung cp a dch v vi cht lng c m bo) th vic trin khai WiMAX cung cp cc dch v a phng tin s nhanh v c hiu qu kinh t cao hn v vi vic cung cp bng thng rng s p ng c cc yu cu v cht lng. WiMAX c nhng u th vt tri so vi cc cng ngh cung cp dch v bng thng rng hin nay v tc truyn d liu v gi c thp do cung cp cc dch v trn nn IP. Vi kh nng truy nhp t xa, tc d liu cao p ng a dng cc dch v nh 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... WiMAX ph hp vi cc ng dng truy cp xch tay, vi s hp nht trong cc my tnh xch tay v PDA, cho php truy nhp khng dy bng rng ngoi tri cc khu vc th, ng thi cng thch ng vi cc ng dng truy nhp bng rng c nh nhng vng xa xi, ho lnh.

WiMAX l mt gii php tuyt vi v mt cng ngh kt ni nhng s cn mt chi ph ln phi b ra pht trin h tng cho mt h thng mi trong khi h thng c vn cn cha c s dng ht. Qu thc, nu phi u t mt khon kinh ph trin khai WiMAX trn mt quy m ln trong khi cng ngh 3G vn l tim nng cha khai thc ht th chc chn cc cng ty vin thng s phi tnh ton v cn nhc ht sc k lng trc khi b tin u t cho vic pht trin dch v ny.1.3 Hai m hnh ng dng WiMAX

Tiu chun IEEE 802.16 xut 2 m hnh ng dng:

M hnh ng dng c nh

M hnh ng dng di 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.

Hnh 1.1 M hnh mng WiMAX c nhTiu chun IEEE 802.16-2004 cng cho php t anten trong nh nhng tt nhin tn hiu thu khng khe 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). WiMAX c nh c th phc v cho cc loi ngi dng (user) 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, cc user th c th phn tn ti cc a phng nh nng thn v cc vng su vng xa kh a mng cp hu tuyn n .

S kt cu mng WiMAX c a ra trn hnh 1.4. Trong m hnh ny b phn v tuyn gm cc trm gc WiMAX BS (lm vic vi anten t trn thp cao) v cc trm ph SS (SubStation). Cc trm WiMAX BS ni vi mng th MAN hoc mng PSTN

1.3.2 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. Tiu chun 802.16e b sung cho tiu chun 802.16-2004 hng ti cc user 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 digital truy nhp khng dy c phm vi ph sng rng tha mn c cc nhu cu a dng ca thu bao. Tiu chun IEEE 802.16e c thng qua trong nm 2005.

2 Cc chun trong WiMAX

2.1 Chun IEEE 802.16 - 2001

Chun IEEE 802.16-2001 c hon thnh vo thng 10/2001 v c cng b vo ngy 08/04/2002, nh ngha c t k thut giao din khng gian WirelessMAN cho cc mng vng th. Vic hon thnh chun bo trc s chp nhn truy nhp khng dy bng rng nh mt cng c ch yu mi trong s c gng lin kt cc ta nh v c quan doanh nghip vi cc mng vin thng nng ct trn th gii.Nh trong nh ngha chun IEEE 802.16, mt mng vng th khng dy cung cp s truy nhp mng cho cc ta nh thng qua ngten ngoi tri c th truyn thng vi cc trm c s rai trung tm (BS). Do h thng khng dy c kh nng hng vo nhng vng a l rng, hoang vng m khng cn pht trin c s h tng tn km nh trong vic trin khai cc kt ni cp nn cng ngh t ra t tn km hn trong vic trin khai v nh vy dn n s truy cp bng rng tng ln khp mi ni. Bn thit k MAC WirelessMAN c th lm thch nghi mi kt ni vi cht lng dch v (QoS) hon ho. Vi cng ngh c m rng theo hng ny, n l chun c pht trin h tr nhng ngi cung lun cn s di chuyn ( v d nh trong xe c chng hn ). Chun IEEE 802.16 c thit k m ra mt tp cc giao din khng gian (air interfaces) da trn mt giao thc MAC thng thng nhng vi cc c t lp vt l ph thuc vo vic s dng v nhng iu chnh ph c lin quan. Chun hng vo cc tn s t 10 66 GHz, ni ph rng hin c sn s dng trn ton cu, nhng ti nhng bc sng ngn c xem nh nhng thch thc trong vic trin khai. Chnh v l do l tin cho s ra i ca chun mi, chun 802.16a.

2.2 Chun IEEE 802.16a

Chun 802.16a c hon thnh vo thng 11 - 2002 v c cng b vo thng 4 - 2003. Chun ny cung cp kh nng truy cp bng rng khng dy u cui v im kt ni bng bng tn 2-11 GHz, bao gm c nhng ph cp php v khng cp php, vi khong cch kt ni ti a c th t ti 50 km trong trng hp kt ni im im v 7-10 km trong trng hp kt ni t im a im. Tc truy nhp c th t ti 70 Mbps.

Trong khi vi di tn 10-66Ghz chun 802.16 - 2001 phi yu cu tm nhn thng, th vi di tn 2-11Ghz chun 802.16a cho php kt ni m khng cn tho mn iu kin tm nhn thng, trnh c tc ng ca cc vt cn trn ng truyn nh cy ci, nh ca. Chun ny s gip ngnh vin thng c cc gii php nh cung cp bng thng theo yu cu, vi thi gian thi cng ngn hay bng thng rng cho h gia nh m cng ngh thu bao s hay mng cp khng tip cn c. So snh vi nhng tn s cao hn, nhng ph nh vy to c hi thu c nhiu khch hng hn vi chi ph chp nhn c, mc d cc tc d liu l khng cao. Tuy nhin, cc dch v s hng ti nhng to nh ring l hay nhng x nghip va v nh.

2.3 Chun IEEE 802.16c - 2002

Chun IEEE 802.16c c a ra vo thng 9/2002. Chun c nng cp ln t chun 802.16 2001. Bn cp nht sa mt s li v s mu thun trong bn tiu chun ban u v thm vo mt s profiles h thng chi tit cho di tn 10 66 GHz.2.4 Chun IEEE 802.16d - 2004

Chun IEEE 802.16-2004 c chnh thc ph chun ngy 24/07/2004 v c cng b rng ri vo thng 9/2004. IEEE 802.16 2004 thng c gi vi tn 802.16-REVd. Chun ny c hnh thnh da trn s tch hp cc chun 802.16-2001, 802.16a, 802.16c. Chun mi ny c pht trin thnh mt tp cc c t h thng c tn l IEEE 802.16-REVd, nhng ton din phn loi nh l mt s k tha hon chnh chun IEEE 802.16 ban u.

Chun 802.16d h tr c 2 di tn s, cho php kt ni thc hin cc mi trng khc nhau :

Bng tn 10 66 Ghz : vi bng tn ny thng c dung trong mi trng tm nhn thng ( LOS ). rng knh c khuyn ngh cho di tn ny l 25 n 28 MHz. N cung cp kh nng h tr tt trong nhng ng dng m hnh im a im.

Bng tn 2 11 GHz : vi bng tn ny thng c dung trong mi trng khng trong tm nhn thng ( NLOS ).N cung cp kh nng h tr tt trong nhng ng dng m hnh Mesh.

2.5 Chun IEEE 802.16e 2005 Chun 802.16e - 2005 c t chc IEEE a ra vo thng 11 - 2005. y l phin bn pht trin da trn vic nng cp chun 802.16 - 2004 nhm h tr thm cho cc dch v di ng. Chun ny s dng k thut a truy nhp SOFDMA ( Scalable Orthogonal Frequency Division Multiplexing Access ), k thut iu ch a sng mang s dng knh ph. Bng tn c khuyn co dnh cho chun l < 6Ghz phc v cho cc ng dng trong mi trng ko trong tm nhn thng v ng dng di ng. Tuy tc v kh nng bao ph khng c ln nh chun c nh, nhng vi knh bng thng 10 Mhz, n cng c th t ti tc 30 MHz, vi kh nng bao ph ti 15 km. Mt c im ni bt ca chun ny l c th ng dng trong mi trng di ng vi tc l thuyt c th ln ti n 120 km/h.

3 c im chun 802.16d v 802.16e cho WiMAX c nh v di ng

Trong chun IEEE 802.16 d v 802.16e c a ra 4 cu hnh dnh cho lp PHY l:

+ Wireless MAN-SC PHY s dng phng php iu ch n sng mang v hot ng ti bng tn t 10-66 GHz

+ Wireless MAN-SCa PHY cng s dng phng php iu ch n sng mang nhng c thit k hot ng trong mi trng NLOS v trong gii tn s di 11GHz

+ Wireless MAN-OFDM PHY s dng phng php iu ch OFDM , c thit k hot ng trong mi trng NLOS v trong di tn s di 11GHz

+ Wireless MAN-OFDM PHY cng s dng phng php iu ch OFDM v cng hot ng trong mi trng NLOS di tn s 11GHz, nhng y l lp PHY m rng cho cc ng dng mobile.

3.1 Cu trc khung lp PHYTrong bng tn cp php, phng php song cng c la chn l FDD hoc TDD. Trong bng tn khng phi ng k phng php song cng c s dng l TDD. Mt khung thi gian bao gm PHY PDU ca BS v SS, khong trng v thi gian bo v.

OFDM PHY h tr truyn thng tin da trn cc khung. Mt khung bao gm mt downlink subframe v mt uplink subframe. Mt downlink subframe ch bao gm mt dowlink PHY PDU, mt uplink subframe bao gm mt hoc nhiu uplink PHY PDUs, mi ci c truyn t mt SS khc nhau.

Mt downlink bt u bng mt phn preamble(?) c s dng ng b PHY, tip theo l mt FCH brust. FCH brust l mt OFDM symbol di v c truyn s dng BPSK vi tc vi h thng m bt buc. Nu c truyn trong khung th mt bn tin DL_MAP s l MAC_PDU u tin trong burst ngay sau FCH. Mt bn tin UL_MAP s nm ngay sau bn tin DL_MAP (nu nh n c truyn) hoc l DLFP (nu nhu bn tin DL_MAP khng c truyn). Nu bn tin UCD v DCD c truyn trong khung n s i ngay sau bn tin DL_MAP v UL_MAP. Mc d burst # 1 bao gm cc bn tin iu khin MAC broadcast nhng n khng cn thit phi s dng phng php iu ch v m ha hiu qu. Phng php iu ch m ha hiu qu c th s dng nu n c h tr v p dng cho tt c cc SS ca mt BS. Mt FCH c theo sau bi mt hoc nhiu downlink burst.

Mi mt downlink burst bao gm mt s nguyn cc OFDM symbol. V tr v cc profile ca downlink burst u tin c xc nh trong downlink frame prefix (DLFP). V tr v cu trc ca (profile) ca s lng burst theo sau cng c th s c xc nh trong DLFP. Ti thiu mt DL_MAP y phi c broadcast trong burst# 1. (thng tin trong bng 342)

V tr v profile ca cc burst khc c xc nh trong DL_MAP

Hnh 3.1 Cu trc khung OFDM dnh cho truyn TDD

Hnh 3.2 Cu trc khung OFDM dnh cho truyn FDDSau y l cc thng s nh dng ca DLFP:C phpKch thcNote

DL_frame_prefix_format(){

Base_station_ID4 bits4LBS ca BS_ID. Burst c xc nh bi DLFP s khng c gii m nu nhng bit ny khng ph hp vi nhng bit ca BS m n c ng k

Frame_number4 bits4 LBS

Configuration_change_count4 bts4 LBS ca gi tr change count

Reserved4 bitsS c thit lp v 0

For (n=0;n