A/ TM HIU MNG TRUYN DN TI BU IN TNH T T HU

TRNG I HC BCH KHOA H NI

PROJECT 2 ti :CNG NGH WIMAX V M PHNG Ging vin hng dn : GVC.ThS H S Bng Sinh vin thc hin : Nguyn c Chin Lp : CNTT-TT 1.1 K56

MSSV: 20111249H Ni, thng 05 nm 2014 LI NI U

Trong nhng nm gn y, cc dch v ng dng trn Internet c bc pht trin bng n vi nhiu loi hnh dch v mi nh cc dch v mua bn trc tuyn, ngn hng, du lch hay cc dch v o to t xa, game trc tuyn... Cng vi s pht trin bng n ca cc loi hnh dch v trn Internet, cc cng ngh truy cp cng lin tc c pht trin p ng nhng i hi ngy cng cao v bng thng cho truy cp Internet. Cc cng ngh truy cp bng rng c pht trin nhanh chng trong nhng nm gn y bao gm cc cng ngh truy cp hu tuyn v cng ngh v tuyn.

Mt lot cc chun v mng truy cp v tuyn bng rng c nhiu t chc nghin cu, xy dng v pht trin nh chun IEEE 802.11x, IEEE 802.15, IEEE 802.16, IEEE 802.20, HIPERLAN 1/2, HomeRF, chun Bluetooth,vv... Phm vi ng dng ca cc chun ny bao trm t mng c nhn (PAN), mng ni b (LAN), mng din rng (MAN) v mng din rng (WAN).

H thng WiMAX c sn xut da trn h tiu chun IEEE 802.16 ang c cc hng cung cp thit b cng nh nh cung cp dch v quan tm c bit. Cc h thng WiMAX c nh da trn chun 802.16-2004 c sn xut, a vo th nghim v c din n WIMAX cp chng nhn cho thy r nhng u im ca cng ngh ny. H thng WiMAX di ng da trn tiu chun 802.16e cng ang c cc nh cung cp thit b ln k hoch a thit b vo th nghim trong thi gian ti.

Mng Vin thng Vit Nam trong nhng nm qua c s pht trin mnh m, cc h thng cung cp dch v truy cp bng rng v ang c trin khai ti hu ht cc tnh thnh. Trong khi , nhu cu s dng dch v bng rng li ang i hi rt cp thit ti nhiu vng, nhiu khu vc m cc gii php hin c rt kh trin khai hoc trin khai chm. c th trin khai nhanh chng v hiu qu h thng truy cp bng rng ti cc khu vc ny th vic nghin cu trin khai cc h thng truy cp v tuyn bng rng WiMAX l ht sc cn thit.

Mc lc

2LI NI U

3Mc lc

4Chng 1: TNG QUAN V WIMAX

41.1. Gii thiu chng.

41.2. Khi nim.

41.3. c im.

71.4. Cc chun ca Wimax.

91.5. Cc bng tn ca Wimax.

12Chng 2: K THUT IU CH OFDM

122.1. Cc k thut ghp knh:

132.2. u nhc im ca OFDM

15Chng 3: CU TRC GI TIN OFDM

153.1. Cu trc chung

153.2. Cc thnh phn trong khung

163.3. Cu trc phn Downlink-MAP v Uplink-MAP

20Chng 4: M PHNG WIMAX TRN OMNET++

204.1. Gii thiu chng.

204.2. Gii thiu v chng trnh m phng OMNet++.

23KT LUN V HNG PHT TRIN TI

25TI LIU THAM KHO

Chng 1: TNG QUAN V WIMAX1.1. Gii thiu chng.

Trong chng ny trnh by tng qut v cng ngh truy nhp v tuyn bng rng, c im, cc chun ca WiMAX, bng tn s dng, cch thc truyn sng, cc m hnh ng dng, l trnh pht trin v tnh hnh trin khai WiMAX. 1.2. Khi nim.WiMax l mt mng khng dy bng thng rng vit tt l Worldwide Interoperability for Microwave Access. WiMax ng dng trong thit b mng Internet dnh s lng ngi s dng ln thm vo gi thnh r. WiMax c thit k da vo tiu chun IEEE 802.16. WiMax gii quyt tt nht nhng vn kh khn trong vic qun l u cui.WiMax s dng k thut sng v tuyn kt ni cc my tnh trong mng Internet thay v dng dy kt ni nh DSL hay cp modem. WiMax nh mt tng i trong vng ln cn hp l n mt trm ch m n c yu cu thit lp mt ng d liu n Internet. Ngi s dng trong phm vi t 3 n 5 dm so vi trm ch s c thit lp mt ng dn cng ngh NLOS (Non-Line-Of-Sight) vi tc truyn d liu rt cao l 75Mbps. Cn nu ngi s dng trong phm vi ln hn 30 dm so vi trm ch th s c anten s dng cng ngh LOS (Line-Of-Sight) vi tc truyn d liu gn bng 280Mbps. WiMAX l mt chun khng dy ang pht trin rt nhanh, ha hn to ra kh nng kt ni bng thng rng tc cao cho c mng c nh ln mng khng dy di ng, phm vi ph sng c m rng.1.3. c im.

WiMAX c thit k ch trng vo nhng thch thc gn vi cc loi trin khai truy nhp c dy truyn thng nh:

Backhaul. S dng cc anten im im ni nhiu hotspot vi nhau v n cc trm gc qua nhng khong cc di (ng kt ni gia im truy nhp WLAN v mng bng rng c nh).

Last mile. S dng cc anten im a im ni cc thu bao thuc nh ring hoc doanh nghip ti trm gc.WiMAX c pht trin vi nhiu mc tiu quan tm nh:

Cu trc mm do : WiMAX h tr cc cu trc h thng bao gm im a im, cng ngh li (mesh) v ph sng khp mi ni. iu khin truy nhp MAC) phng tin truyn dn h tr im a im v dch v rng khp bi lp lch mt khe thi gian cho mi trm di ng (MS). Nu c duy nht mt MS trong mng, trm gc (BS) s lin lc vi MS trn c s im im. Mt BS trong mt cu hnh im im c th s dng anten chm hp hn bao ph cc khong cch xa hn. Cht lng dch v QoS : WiMAX c th c ti u ng i vi hn hp lu lng s c mang. C 4 loi dch v c h tr: dch v cp pht t nguyn (UGS), dch v hi vng thi gian thc (rtPS), dch v hi vng khng thi gian thc (nrtPS), n lc tt nht (BE).

Trin khai nhanh: So snh vi trin khai cc gii php c dy, WiMAX yu cu t hoc khng c bt c s xy dng thit lp bn ngoi. V d, o h to rnh cc ng cp th khng yu cu. Cc nh vn hnh m c c cc ng k s dng mt trong cc di tn ng k, hoc d kin s dng mt trong cc di tn khng ng k, khng cn trnh cc ng dng hn na cho chnh ph.

Dch v a mc: Cch thc ni m QoS c phn pht ni chung da vo s tha thun mc dch v (SLA) gia nh cung cp dch v v ngi s dng cui cng. Chi tit hn, mt nh cung cp dch v c th cung cp cc SLA khc nhau ti cc thu bao khc nhau, thm ch ti nhng ngi dng khc nhau s dng cng MS. Cung cp truy nhp bng rng c nh trong nhng khu vc th v ngoi , ni cht lng cp ng th km hoc a vo kh khn, khc phc thit b s trong nhng vng mt thp ni m cc nhn t cng ngh v kinh t thc hin pht trin bng rng rt thch thc. Tnh tng thch: WiMAX da vo quc t, cc chun khng c tnh cht r rt nh cung cp, to ra s d dng i vi ngi dng cui cng truyn ti v s dng MS ca h cc v tr khc nhau, hoc vi cc nh cung cp dch v khc nhau. Tnh tng thch bo v s u t ca mt nh vn hnh ban u v n c th chn la thit b t cc nh i l thit b, v n s tip tc a chi ph thit b xung khi c mt s chp nhn a s. Di ng: IEEE 802.16e b sung thm cc c im chnh h tr kh nng di ng. Nhng ci tin lp vt l OFDM (ghp knh phn chia tn s trc giao) v OFDMA (a truy nhp phn chia tn s trc giao) h tr cc thit b v cc dch v trong mt mi trng di ng. Nhng ci tin ny, bao gm OFDMA m rng c, MIMO (nhiu u ra nhiu u vo), v h tr i vi ch idle/sleep v hand off, s cho php kh nng di ng y tc ti 160 km/h. Mng WiMax di ng cho php ngi s dng c th truy cp Internet khng dy bng thng rng ti bt c trong thnh ph no. Li nhun: WiMAX da vo mt chun quc t m. S chp nhn a s ca chun v s dng chi ph thp, cc chip c sn xut hng lot, s a chi ph gim t ngt v gi cnh tranh xy ra s cung cp s tit kim chi ph ng k cho cc nh cung cp dch v v ngi s dng cui cng. Mi trng khng dy c s dng bi WiMAX cho php cc nh cung cp dch v ph v nhng chi ph gn vi trin khai c dy, nh thi gian v cng sc. Hot ng NLOS: Kh nng hat ng ca mng WiMAX m khng i hi tm nhn thng gia BS v MS. Kh nng ny ca n gip cc sn phm WiMAX phn pht di thng rng trong mt mi trng NLOS. Ph sng rng hn: WiMAX h tr ng nhiu mc iu ch, bao gm BPSK, QPSK, 16QAM, 64QAM. Khi yu cu vi b khuch i cng sut cao v hot ng vi iu ch mc thp (v d BPSK hoc QPSK). Cc h thng WiMAX c th ph sng mt vng a l rng khi ng truyn gia BS v MS khng b cn tr. M rng phm vi b gii hn hin ti ca WLAN cng cng (hotspot) n phm vi rng (hotzone) cng cng ngh th c th s dng nh v di chuyn. nhng iu kin tt nht c th t c phm vi ph sng 50 km vi tc d liu b h thp (mt vi Mbit/s), phm vi ph sng in hnh l gn 5 km vi CPE (NLOS) trong nh v gn 15km vi mt CPE c ni vi mt anten bn ngoi (LOS).

Dung lng cao: C th t c dung lng 75 Mbit/s cho cc trm gc vi mt knh 20 MHz trong cc iu kin truyn sng tt nht. Tnh m rng. Chun 802.16 -2004 h tr cc di thng knh tn s v tuyn (RF) mm do v s dng li cc knh tn s ny nh l mt cch tng dung lng mng. Chun cng nh r h tr i vi TPC (iu khin cng sut pht) v cc php o cht lng knh nh cc cng c thm vo h tr s dng ph hiu qu. Chun c thit k t t l ln ti hng trm thm ch hng nghn ngi s dng trong mt knh RF. Cc nh vn hnh c th cp pht li ph qua hnh qut nh s thu bao gia tng. H tr nhiu knh cho php cc nh ch to thit b cung cp mt phng tin ch trng vo phm vi s dng ph v nhng quy nh cp pht c ni r bi cc nh vn hnh trong cc th trng quc t thay i khc nhau.

Bo mt: Bng cch mt ha cc lin kt v tuyn gia BS v MS, s dng chun mt ha tin tin AES ch CCM, m bo s ton vn ca d liu trao i qua giao din v tuyn. Cung cp cho cc nh vn hnh vi s bo v mnh chng li nhng hnh vi nh cp dch v.

1.4. Cc chun ca Wimax.1.4.1. Chun IEEE 802.16 2001.

Chun IEEE 802.16-2001 c hon thnh vo thng 10/2001 v c cng b vo 4/2002, nh ngha c t k thut giao din khng gian WirelessMAN cho cc mng vng th. c im chnh ca IEEE 802.16 2001:

Giao din khng gian cho h thng truy nhp khng dy bng rng c nh hat ng di tn 10 66 GHz, cn tha mn tm nhn thng.

Lp vt l PHY: WirelessMAN-SC.

Tc bit: 32 134 Mbps vi knh 28 MHz.

iu ch QPSK, 16 QAM v 64 QAM.

Cc di thng knh 20 MHz, 25 MHz, 28 MHz.

Bn knh cell: 2 5 km.

Kt ni c nh hng, MAC TDM/TDMA, QoS, bo mt.

1.4.2. Chun IEEE 802.16a.V nhng kh khn trong trin khai chun IEEE 802.16, hng vo vic s dng tn s t 10 66 GHz, mt d n sa i c tn IEEE 802.16a c hon thnh vo thng 11/2002 v c cng b vo thng 4/2003. Chun ny c m rng h tr giao din khng gian cho nhng tn s trong bng tn 211 GHz, bao gm c nhng ph cp php v khng cp php v khng cn tho mn iu kin tm nhn thng. c im chnh ca IEEE 802.16a nh sau:

B sung 802.16, cc hiu chnh MAC v cc c im PHY thm vo cho di 2 11 GHz (NLOS).

Tc bit : ti 75Mbps vi knh 20 MHz.

iu ch OFDMA vi 2048 sng mang, OFDM 256 sng mang, QPSK, 16 QAM, 64 QAM.

Di thng knh c th thay i gia 1,25MHz v 20MHz.

Bn knh cell: 6 9 km.

Lp vt l PHY: WirelessMAN-OFDM, OFDMA, SCa.

Cc chc nng MAC thm vo: h tr PHY OFDM v OFDMA, h tr cng ngh Mesh, ARQ.

1.4.3. Chun IEEE 802.16 2004. Thng 7/2004, chun IEEE 802.16 2004 hay IEEE 802.16d c chp thng qua, kt hp ca cc chun IEEE 802.16 2001, IEEE 802.16a, ng dng LOS di tn s 10- 66 GHz v NLOS di 2- 11 GHz. Kh nng v tuyn b sung nh l beam forming v knh con OFDM. 1.4.4. Chun IEEE 802.16e.u nm 2005, chun khng dy bng thng rng 802.16e vi tn giMobile WiMax c ph chun, cho php trm gc kt ni ti nhng thit b ang di chuyn.Chun ny gip cho cc thit b t cc nh sn xut ny c th lm vic, tng thch tt vi cc thit b t cc nh sn xut khc. 802.16e hat ng cc bng tn nh hn 6 GHz, tc ln ti 15 Mbps vi knh 5 MHz, bn knh cell t 2 5 km.

WiMAX 802.16e c h tr handoff v roaming. S dng SOFDMA, mt cng ngh iu ch a sng mang. Cc nh cung cp dch v m trin khai 802.16e cng c th s dng mng cung cp dch v c nh. 802.16e h tr cho SOFDMA cho php s sng mang thay i, ngoi cc m hnh OFDM v OFDMA. S phn chia sng mang trong m hnh OFDMA c thit k ti thiu nh hng ca nhiu pha thit b ngi dng vi anten a hng. C th hn, 802.16e a ra h tr ci tin h tr MIMO v AAS, cng nh cc handoff cng v mm. N cng ci tin cc kh nng tit kim cng sut cho cc thit b di ng v cc c im bo mt linh hot hn.1.5. Cc bng tn ca Wimax.

1.5.1.Cc bng tn c xut cho WiMAX trn th gii.

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

Bng tn 2,3-2,4GHz (2,3GHz Band) : c xut s dng cho Mobile WiMAX. Ti Hn Quc bng ny c trin khai cho WBA (WiBro).

Bng tn 2,4-2,4835GHz: c xut s dng cho WiMAX trong tng lai .

Bng tn 2,5-2,69GHz (2,5GHz Band): c xut s dng cho WiMAX di ng trong giai on u .

Bng tn 3,3-3,4GHz (3,3GHz Band): c xut s dng cho WiMAX c nh. Bng tn 3,4-3,6GHz (3,5GHz Band): c xut s dng cho WiMAX c nh trong giai on u : FWA (Fixed Wireless Access)/WBA (WideBand Access). Bng tn 3,6-3,8GHz: c xut s dng cho WiMAX c nh (WBA) v cp cho Chu u. Tuy nhin, bng 3,7-3,8 GHz c dung cho v tinh vin thng Chu , nn bng tn ny khng c s dng cho Wimax Chu . Bng tn 5,725-5,850GHz: c xut s dng cho WiMAX c nh trong giai on u. Ngoi ra, mt s bng tn khc phn b cho BWA cng c mt s nc xem xt cho BWA/WiMax l: bng tn 700-800MHz (< 1GHz), bng 4,9-5,1GHz.

1.5.2.Cc bng tn Vit nam c kh nng dnh cho WiMAX.

Bng tn 2,3-2,4GHz :

C th dnh on bng tn ny cho WiMAX. Bng tn 2,3-2,4GHz thch hp cho c WiMAX c nh v di ng.

Bng tn 2,5-2,69GHz :

Bng tn ny hin nay ang c s dng nhiu cho vi ba v MMDS (tp trung ch yu H ni v thnh ph H Ch Minh). Ngoi ra, bng tn ny l mt trong cc bng tn c xut s dng cho 3G.

Bng tn ny li l bng tn c nh gi l thch hp nht cho WiMAX di ng v c Din n WiMAX xc nhn chnh thc l bng tn WiMAX. Mt s nc cng dnh bng tn ny cho WiMAX nh M, Mhic, Brazil, Canada, Singapo. V vy, ngh dnh bng tn 2,5-2,69GHz cho WiMAX.

Bng tn 3,3-3,4GHz: Theo Qui hoch ph tn s VT quc gia, bng tn ny c phn b cho cc nghip v V tuyn nh v, c nh v lu ng. Hin nay, v pha dn s v qun s vn cha c h thng no c trin khai trong bng tn ny. Do , c th cho php s dng WiMAX trong bng tn 3,3-3,4GHz.

Bng tn 3,4-3,6GHz, 3,6-3,8GHz: i vi Vit nam, h thng v tinh VINASAT d kin s s dng mt s on bng tn trong bng C v Ku, trong c bng tn 3,4-3,7GHz. Ngoi ra, on bng tn 3,7-3,8GHz mc d cha s dng cho VINASAT nhng c th c s dng cho cc trm mt t lin lc vi cc h thng v tinh khc. V vy, khng nn trin khai WiMAX trong bng tn 3,4 - 3,8 GHz.

Bng tn 5,725-5,850GHz:Hin nay, bng tn ny c B qui nh dnh cho WiFi. Nu cho php trin khai WiMAX trong bng tn ny th cng s hn ch bng tn dnh cho WiFi. Bng tn ny c th thch hp cho cc h thng WiMAX vng nng thn, vng su, vng xa, c th cho php h thng WiMAX pht vi cng sut cao hn gim gi thnh trin khai h thng WiMAX. V vy, ngh cho php trin khai WiMAX trong bng tn 5,725-5,850GHz nhng WiMAX phi dng chung bng tn v phi bo v cc h thng WiFi.

Nh vy, vi hin trng s dng bng tn ti Vit Nam nh trn, cc bng tn c kh nng dnh cho WiMAX Vit Nam l:

Bng tn 2,3-2,4GHz v 3,3-3,4GHz cho cc h thng truy cp khng dy bng rng, k c WiMAX.

Bng tn 5,725-5,850GHz cho cc h thng truy cp khng dy bng rng, k c WiMAX nhng cc h thng ny phi dng chung bng tn vi cc h thng WiFi vi iu kin bo v cc h thng WiFi hot ng trong bng tn ny.

Bng tn 2,5-2,690GHz cho cc h thng truy cp khng dy bng rng, k c IMT-2000 v WiMAX.

Hin ti, chnh ph cp php th nghim dch v WiMAX di ng ti bng tn 2,3-2,4 GHz; v bng tn 2,5-2,69 GHz. (theo cng vn s 5535/VPCP-CN ca Vn phng Chnh ph).

Chng 2: K THUT IU CH OFDM2.1. Cc k thut ghp knh: Ghp knh theo bc sng mang (WDM):

c dng cho truyn dn cp quang. Ghp knh theo bc sng cho php cc knh c truyn ti nhng bc sng khc nhau cho cng mt hng hay c hai hng trn cng mt si quang. L mt bin th ca ghp knh thao tn s.

Ghp knh theo thi gian (TDM):

Phng php ny a cc bn tin khc nhau, v d: t cc m PCM ca nhng ngi s dng kahcs nhau vo cc khe thi gian khng chng ln ln nhau. Mi knh ca ngi s dng dng mt bng tn ln nhng ch trong 1 khong thi gian, gi l khe thi gian. Thng tin ca mi ngi s dng s chim mt khe thi gian ca mt khung v nguyn l phn chia theo thi gian caho php nhiu ngi s dng truy cp mng ti 1 thi im v s dng cng mt tn s sng mang.

Ngoi ra cn c ghp knh theo nng (PDH)

Ghp knh theo tn s (FDM):

Bin tn s mi tn hiu ln mt tn s sng mang khc nhau. Cc tn hiu c iu ch truyn i qua cng mt knh truyn v b lc n bng s phn chia cc tn hiu n bn thu. Bng tn ca h thng c chia thnh nhiu knh hp khc nhau, mi knh dnh cho mt ngi s dng trong ton b thi gian truyn tin.

pha thu c th tch c cc tn hiu bng cc b lc th phi c nhn khong cch gia ph ca cc sng mang. Ph ca cc tn hiu khng st nhau gp nn lng ph bng thng do hiu sut s dng bng thng ca FDM kh thp.

S ra i ca k thut ghp knh phn chia theo tn s trc giao OFDM ( Orthogonal Frequency Division Multiplexing) gii quyt c vn ny.

V bn cht OFDM l l k thut ghp knh theo tn s tng t nh FDM, song vi cc sng mang trc giao trn min tn s. K thut OFDM l mt trng hp c bit ca phng php iu ch a sng mang, trong cc sng mang ph trc giao vi nhau, nh vy ph tnh hiu cc sng mang ph cho php chng ln ln nhau m pha thu vn c th khi phc li tn hiu ban u. S chng ln ph tn hiu lm cho h thng OFDM c hiu sut s dng ph ln hn nhiu so vi k thut iu ch thng thng.

Hnh: Ph ca mt sng mang thong thng(a) v ph ca mt tn hiu OFDM (b,c)

* Trc giao trong OFDM

Tn hiu c gi l trc giao vi nhau nu chng c lp vi nhau. Trc giao l mt c tnh cho php nhiu tn hiu mang tin c c truyn i trn knh truyn thng thng m khng c nhiu gia chng. Mt tnh trc giao gia cc tn hiu s gy ra s ri lon gia cc tn hiu, lm gim cht ln thng tin.

OFDM t c s trc giao bng cch iu ch tn hiu vo mt tp cc sng mang trc giao. Tn s gc ca tng sng mang con s bng mt s nguyn ln nghch o thi gian tn ti symbol

2.2. u nhc im ca OFDMu im:- Tng hiu qu s dng bng thng.- Bn vng vi fading chn lc tn s do cc k hiu c bng thng hp nn mi sng mang ph ch chu fading phng. - Chng c nhiu lin k hiuISIdo chu k k hiu di hn cng vi vic chn thm khong bo v cho mi k hiuOFDM.- S phc tp ca my pht v my thu gim ng k nh s dngFFTv IFFT.- C th truyn d liu tc cao.Khuyt im:- Nhy vi offset tn s+ Ch cn mt sai lch nh cng c th lm mt tnh trc giao ca cc sng mang ph. V vyOFDMrt nhy vi hiu ng dch tn Dopler.+ Cc sng mang ph ch tht s trc giao khi my pht v my thu s dng cng tp tn s. V vy, my thu phi c lng v hiu chnh offset tn s sng mang ca tn hiu thu c.+ Ti my thu, s rt kh khn trong vic quyt nh v tr nh thi ti u gim nh hng caICIvISI.+ T s cng sut nh trn cng sut trung bnh PAPR (Peak to Average Power Ratio) l ln v tn hiuOFDMl tng ca N thnh phn c iu ch bi cc tn s khc nhau.Khi cc thnh phn ny ng pha, chng to ra ng ra mt tn hiu c bin rt ln. Ngc li, khi chng ngc pha, chng li trit tiu nhau lm ng rabng 0. Chnh v vy, PAPR trong h thngOFDMl rt ln.

Chng 3: CU TRC GI TIN OFDM3.1. Cu trc chung

Hnh 3.1: Cu trc khung 802.16 OFDM

802.16 s dng k thut truy cp OFDM m c x dng trong cc h thng khc nh 802.11a. Nhng c im mi chnh l lp PHY(Physical layer) quan h vi 802.11a l: s sng mang FFT(Fast Fuorier Tranform) di hn ( t 64-FFT n 256-FFT); thay i c bng thng v tn s ly mu, v thay i c t s cu hai gi tr ny; nhiu ngi s dng c vi mt Tx burst; loi iu ch c th thay i theo thi gian trong khung; bn thay cho hai gi tr khong bo v cn thit.

Cu trc khung tin: mi khung tin c chia thnh khung nh DL(Downlink) v UL(Uplink). Nhng khung nh DL v UL c bt u vi preamble( cho bit gii hn s sng mang ca symbol) tm li thng tin v knh truyn v cho php my thu tm li p ng knh. FCH v DL MAP cha thng tin ni dung khung(v tr v iu ch ca mi burst) v c iu ch-BPSK.

3.2. Cc thnh phn trong khungUL v DL c tch ra bi cc khe h: transmit transition gap(TTG) sau khung con DL v receive transiton gap(RTG) sau khung con UL.

Trong DL c 4 thnh phn m n mang thng tin cho php my thu gii iu ch tn hiu: preamble, FCH,DL-MAP v UL-MAP.

Bn thnh phn ny trong cu trc 802.16- 2004 c s dng cho vic truyn thm thng tin tn hiu cn thit trong tn hiu OFDMA( Orthogonal Frequency Division Multiplex Access- a truy nhp phn chia theo tn s trc giao)

Preamble

preamble l bt u ca mi khung tin DL. N bao gm cc sng mang u ch-BPSK v c di 1 symbol OFDMA.

Preamble c s dng vo hai mc ch:

B tr tun t pilot vo trong preamble lm cho n d dng hn cho my thu trong vic nh gi li tn s v pha , ng b vi my pht. Chng c s dng nh gi v cn bng knh.

S sng mang preamble s dng ch ra 3 segment c s dng. Cc sng mang 0,3,6 ch ra bng segment 0 l c s dng, cc sng mang 1,4,7.. ch ra segment 1 c dng, cc sng mang 2,5,8.. ch ra sefment 3 c dng.

FCH

Frame control header(FCH) c iu ch QPSK v c di 2 symbol OFDMA. V tr vt l ca trng FCH l c nh, khi trong preamble khng c thng tin th n s m t a ch.

Ni dung ca FCH m t Subchannel s dng, di ca DL-MAP v cc tham s truyn dn khc.3.3. Cu trc phn Downlink-MAP v Uplink-MAP Downlink-MAP cho bit cu hnh cm, v tr v thi gian ca cc vng trong Downlink Frame. Nu c thng ip DL-MAP l FDU u tin sau khi truyn FCH. N c iu ch BPSK v bo v vi t l 1/2 ca cc chng trnh m ha bt buc.

Cc thng ip qun l DL-MAP MAC xc nh quyn truy cp vo downlink v uplink thng tin tng ng. DL-MAP qun l cc thng ip xc nh thi gian bt u vo trn ng xung. tng t UL-MAP l mt tp hp cc thng tin nh ngha ton b truy cp cho tt c cc trm thu bao ( subsciber station) trong mt khong thi gian k hoch.

Sau DL-MAP v UL-MAP danh sch cc a ch pht sng bi cc trm gc (base station) cc downlink frame, uplink frame. Hnh di l mt v d v DL-MAP v UP-MAP s dng s dng ch FDD (song cng phn chia theo tn s)

Cho OFDM v OFDMA lp PHY, cho php truy cp ca DL-MAP v UL-MAP trong cc dn v ca k hiu v knh con. Thng tin thi gian trong DL-MAP v UL-MAP l tng i. cc thi im sau y c s dng lm tham chiu cho thng tin thi gian cho mi hai nh thi sau:

DL-MAP: s bt ca k hiu u tin ( bao gm c phn preamble nu c) ca khung trong m thng ip c truyn;

UL-MAP: s bt u ca k hiu u tin (bao gm c phn preamble nu c) ca khung m thng ip c truyn cng vi gi tr ca phn b Strar Time (gi tr m c a ra trong thng ip UL-MAP, bn di)

Thng tin trong DL-MAP l v frame hin ti( trong khung m trong thng ip DL-MAP c gi). Thng tin c mang trong UL-MAP lin quan n mt khong thi gian bt u t phn b Start Time tnh t u ca khung hin ti v kt thc sau khi phn b xc nh cui cng. Do , c hai kh nng tn ti lin quan n khung m lin quan ti UL-MAP( phn bit heo trng phn b Start Time trong UL-MAP):

UL-MAP n dng cho khung n+1(nh trong hnh 1), c xc nh l s lin quan thi gian ti a DL-MAP v UL-MAP.

UL-MAP n dng trong khung n, xc nh s lin quan nh thi gian ti thiu l DL-MAP v UL-MAP.

Hai ln nh thi c th c s dng cho c TDD v FDD cc phin bn khc ca hot ng.

Hnh 1

Hnh 2: thng ip DL-MAP MAC dng tng qut qun l cho OFDM PHY. Mi DL-MAP_IE cho bit thi gian bt u ca mt s i vo ng xung v cu hnh cm (chi tit bao gm c knh vt l ca thuc tnh) ca cm ny.

Thng ip DL-MAP

DL-MAP l mt thng ip qun l MAC xc nh thi gian bt u vo v cu hnh trn downlink. Mi ln bt u vo c th hin bng mt DL-MAP_IE (DL-MAP thng tin thnh phn). nh dng DL-MAP_IE l lp PHY ph thuc. BSs to OFDM PHY DL-MAP trong cc nh dng th hin trong hnh 2, bao gm tt c cc thng s sau y:

Kiu thng ip qun l MAC (2 cho DL-MAP).

ng b ha PHY. Trng ng b PHY ph thuc vo c im k thut PHY s dng. Trng ny l trng ( di l 0 byte) cho lp PHY.

DCD m (knh m t ng xung). Gi tr ca Configuration Change Count ( trng CCC) ca DCD, m m t cc cu hnh downlink lin quan ca map ny.

BS ID. BS ID l 1 trng di 48 bit xc nh cc BS. Cc BS c th lp trnh 24bit quan trng nht nh ID iu hnh. y l 1 mc qun l mng c th kt hp vi cc downlink knh ID ca thng ip DCD s l cc tnh hung edge-of-sector v edge-of-cell. R rng, y khng phi l a ch MAC ca BS.

Phn cn li ca mt DL-MAP l m ha ca DL-MAP IEs c c t k thut PHY ph thuc. DL-MAP ca lp OFDM PHY c nh dng hin thij trong hnh di v bao gm tt c cc thng s sau:

Hnh 3 : trng DL-MAP IE cho OFDM (Wimax) lp PHY

Connection Identifier (CID). Nhn s phn cng ca IE pht sng, multicast hoc a ch unicast.

DIUC(Downlink Interval Usage Code). Cc DIUC 4bit nh ngha kiu cm lin kt vi khong thi gian s i vo. N gii thiu cu hnh l mt phn ca thng ip DCD cho mi DIUC c s dng trong cc DL-MAP ngoi tr nhng lin kt n Gap, kt thc ca map v m rng. Preamble hin ti. Nu c thit lp, s i vo s bt u vi on u. Trong downlink, mt preamble ngn c th c ty chn chn vo vo u mt s i vo ng xung ngoi preamble mc nh t u ca frame.

Start Time. Cho thy thi gian bt u, trong n v thi gian k hiu OFDM, lin quan n k hiu u tin ca PDU PHY ( bao gm c preamble), ni thng ip DL-MAP c truyn i. Thi gian ngay lp tc ch nh bi cc gi tr Start Time. S kt thc ca s i vo cui cng c chn nh bng cch phn b mt kt thc ca map (DIUC=14) vi gi tr 0.

Thng ip UL-MAP

Thng ip UL-MAP phn b truy cp vo cc knh ng ln. nh dng chung ca thng ip UL-MAP l gn ging vi DL-MAP v c th hin trong hnh di:

Hnh 4: Cu trc thng ip UL-MAP MAC qun l tng qut, khng phi tt c cc trng. Mi UL-MAP IE cho bit thi gian bt u ca mt s i vo downlink v cm cu hnh(bao gm c chi tit knh thuc tnh vt l) ca cm ny.

UL-MAP IE c mt s thnh phn mi i vi DL-MAP:

Khong thi gian cho bit thi hn, trong cc n v ca cc k hiu OFDM, vic phn b thi gian bao gm phn m u, cc phn trung gian v postamble, cha trong phn b.

Ch s knh con tng ng vi tn s lch ch s ca cc sng mang con ca s phn b knh con.

Midamble Pepetition Interval( thi gian lp li phn trung gian) cho bit co l 1 phn trung gian, v nu c mt khong thi gian lp li phn trung gian trong k t OFDM(8,16 hoc 32 k t d liu).Chng 4: M PHNG WIMAX TRN OMNET++4.1. Gii thiu chng.

Thng qua m hnh m phng mt mng WiMAX n gin hnh dung mt cch trc quan, c th hn v m hnh trin khai v cch thc hot ng ca mt mng s dng cng ngh ny. Ni dung chng gm 2 phn chnh :

- Gii thiu v chng trnh m phng OMNet++.

- Chng trnh m phng mt mng WiMAX n gin.4.2. Gii thiu v chng trnh m phng OMNet++.

4.2.1. Gii thiu chung.

OMNet++ l cm t vit tt ca: Objective Modular Network Tested in C++. Chc nng chnh ca n l:

- M phng lu lng ca mt mng vin thng.- M phng cc giao thc.- M phng mng c cu trc kiu hng i.- M phng mng a x l v phn b ri rc cc h phn cng.- Kim tra tnh hp l ca cu trc phn cng.- nh gi hot ng ca nhng h thng phn mm phc tp.- V nhng h thng s kin ri rc khc...OMNet++ nhng u im chnh sau:

- n gin trong vic s dng v lp trnh v chy trn Windows v s dng ngn ng C++.- C th va dng m phng mng vin thng (mng bo hiu) v mng my tnh (IP).- Giao din m phng ha p v c nhiu la chn cho tc x l s kin trong mng.-

4.2.2. Cu trc lp trnh ca mt chng trnh m phng dng OMNeT++.

Hnh 4.1. Cu trc lin kt ca mt chng trnh m phng trong OMNet++.

Trc ht trong my phi ci chng trnh VC++ lp trnh mi thao tc trn .

Cu trc lin kt ca mt chng trnh m phng.KT LUN V HNG PHT TRIN TI

Vi mc tiu l nghin cu cng ngh truy nhp v tuyn WiMAX v kh nng trin khai trong thc t, qua nghin cu, phn tch, so snh v nh gi vic thc hin trong ni dung n tt nghip c th rt ra kt lun nh sau:

- WiMAX l cng ngh truy nhp v tuyn bng rng c pht trin da trn h tiu chun IEEE 802.16 vi hai tiu chun ch yu c p dng c thng qua l IEEE 802.16-2004 l c s cho phin bn WiMAX c nh v tiu chun IEEE 802.16 e l c s cho phin bn WiMAX di ng.- Din n WiMAX l mt t chc gm cc cng ty cung cp thit b, nh cung cp dch v, ni dung... cng la chn ra cc tiu chun trong cc tiu chun IEEE 802.16-2004 v IEEE802.16e a ra cc profile cho WiMAX. Cc profile v WiMAX c din n WiMAX thng qua v l c s cho vic sn xut thit b, iu ny cho php cc nh sn sut c kh nng hp tc cng pht trin thit b, gim cc chi ph cho nghin cu pht trin, gim gi thnh sn phm.- Cng ngh OFDM vi nhng tnh nng ni tri nh kh nng chng nhiu, kh nng s dng ph cao, cho php truyn tin vi tc cao...c s dng trong WiMAX c nh cho php h thng c kh nng lm vic tt trong mi trng NLOS v tc truyn tin cao.- Phin bn WiMAX di ng da trn tiu chun IEE802.16e l s sa i b sung cc yu cu cho tiu chun IEEE 802.16-2004 b sung nhng tnh nng mm do v hiu qu hn. Vic s dng OFDMA trong phin bn WiMAX di ng cho php s dng linh hot v hiu qu hn bng thng, cng nh tng cng cc kh nng cho an ten, .. Ngoi ra vi phin bn ny cn h tr thm nhiu tnh nng khc nh cht lng dch v, bo mt vv...- Hai phin bn WiMAX s dng 2 cng ngh ghp knh khc nhau l OFDM v OFDMA do vy khng th s dng chung h tng WiMAX cho c 2 loi ny c. S c c hai hng WiMAX cng tn ti v pht trin cho cc yu cu truy nhp v tuyn bng rng c th trng c nh v di ng. Hn na cn ty vo vic ngi ta mun xy dng mt mng l c nh hay di ng, khi la chn mt gii php WiMAX ngi vn hnh cn nh gi cc h s thm nh l cc phn on th trng ch, cc ph tn s dng, mt vi cc iu chnh rng buc v tin trin khai.- So vi cc cng ngh truy nhp v tuyn bng rng c cng phm vi ng dng, WiMAX l cng ngh ang nhn c s quan tm c bit ca c cc nh sn xut cng nh ngi cung cp dch v v ngi s dng nh cc c tnh ni tri ca n, c bit khi nhu cu truy nhp d liu ngy cng mnh. Vi vic WiMAX c ti u cho dch v d liu, WiMAX c th song song tn ti cng vi cc mng nh 3G c ti u cho thoi. Ty thuc mc ch ca nh cung cp, yu cu khch hng, cc mng s c s pht trin tng ng.- Thit b WiMAX c chun ha v thng mi ha, cng vi kt qu th nghim WiMAX trn th gii cng nh ti Vit Nam, cc chnh sch pht trin c B Bu chnh Vin thng a ra l mt m bo cho vic trin khai WiMAX ti Vit Nam. Kh nng p dng trin khai WiMAX ti Vit Nam l hon ph hp. Cc iu kin trin khai WiMAX ti Vit Nam sn sng. Trc mt, vic trin khai th nghim s thc hin vi WiMAX c nh, khi c kt qu, ty thuc vo cc iu kin, nh cung cp dch v c th trin khai WiMAX c nh hay di ng.

Vi kh nng cung cp cc dch v truy nhp bng rng cho c c nh v di ng, WiMAX s l la chn mang tnh quyt nh cho cc nh cung cp dch v trong thi gian ti nhm chim lnh th trng cng nh tng kh nng cnh tranh ca mnh. Hiu r cc c im k thut, vn dng vo cc iu kin thc t trin khai h thng mt cch nhanh chng v hiu qu s em li nhng kh nng ht sc ln cho cc nh cung cp dch v v c ngi s dng.

Vic trin khai WiMAX ti Vit Nam s p ng c cc i hi ngy mt ln v nhu cu truy nhp bng rng, gp phn thc y kinh t pht trin, c bit l cc khu vc nng thn, min ni v cc khu th mi.Hng pht trin ti

WiMAX l mt cng ngh mi ha hn kh nng pht trin ti Vit Nam. Vi c im ring ca mnh, khi a thit b vo mng Vit Nam cn c nhng la chn ph hp vi cc iu kin c th.

Hng pht trin tip theo ca ti l nghin cu su hn v cc gii php iu khin trong WiMAX, c bit l vn v iu ch v h thng anten thch nghi nhm thit k vng phc v c hiu qu nht. Vn bo mt v vn iu ch trong WiMAX cng s c nghin cu su hn nhm a ra nhng yu cu c th ph hp vi mng li Vit Nam.

Cui cng, ti mong mun c mang nhng kin thc thu c tham gia vo trin khai cc h thng WiMAX ti Vit Nam.

TI LIU THAM KHO

(1(. IEEE 802.16 2004, (October, 2004), Air Interface for Fixed Broadband Wireless Access Systems.

[2]. IEEE 802.16e, (February, 2005), Air Interface for Fixed and Mobile Broadband Wireless Access Systems.

[3]. Hassan Yagoobi, Intel Technology Journal, (Vol 08, August 2004) Scalable OFDMA Physical Layer in IEEE 802.16 WirelessMAN4.

[4]. WiMAX Forum, (2006), Mobile WiMAX Part I: A Technical Overview and Performance Evaluation.

[5]. WiMAX Forum, (March, 2006) Mobile WiMAX Part II: A Comparative Analysis.

[6]. 3GPP TS 25.308, (Sep. 2004), High Speed Downlink Packet Access (HSDPA) Overall Description.

[7]. 3rd Generation Partnership Project 2 3GPP2, (March 2004) CDMA2000 High Rate Packet Data Air Interface Specification .[8]. John Wiley & Sons, Ltd, (2006), The Business of WiMAX

[9]. www.ieee.org[10]. www.vnpt.com.vn[11]. www.wimaxforum.org[12]. www.wimaxpro.org[13]. www.wimax.comFile m t cu trc mng *.ned

Th vin giao din ngi dung *.lib/*.a

File x l ca simple modules *.cpp

Th vin li ca chng trnh m phng *.lib/*.a

NEDC compiling

File m t cu trc mng sau khi dch *_n.cpp

C++ compiling

Linking

Chng trnh m phng

Chy chng trnh

File kt qu *.vec, *.sna, *.sca

File cu hnh omnetpp.ini

1PAGE 2