Chuyên đề Nghiên cứu chất lượng dịch vụ trong Wimax trình bày nội dung tổng quan về hệ thống WiMax, các kĩ thuật sử dụng trong WiMax, giải pháp công nghệ WiMax, ứng dụng công nghệ WiMax. Để biết rõ hơn về nội dung chi tiết, mời các bạn cùng tham khảo.
BQ MAO DIJC VA DAO TAO TRUUNG DAI HQC THANG LONG —o0o THANG LONG UNIVERSITY CHUYEN DE TOT NGHIEP NGHIEN CITU CHAT LONG DICH vu TRONG WIMAX Gila vien hurting chin Sinh viers thyc hi§n MA sink vien Chuyen nginh :ThS Holing Tryng Minh :Phan Tien TAng :A13162 :Tin vien thong HA NQI - 2013 MVC LVC "Ma NO1 MU CHUCING 1: TONG QUAN THONG W1MAX 1.1 WiMAX 111 gl? 1.2 Cac chnin cal WIMAX 1.2.1 Chan IEEE 802.16-2001 1.2.2 Chuin IEEE 802.16a 1.2.3 Chain !PPP 802.16-2004 1.2.4 Chuhn IEEE 802.16e 1.3 Phil WiMAX 1.3.1 Bang tiln dang 1.3.2 Bang tin khong (tang k9 5GHz 1.3.3 Clic bang tin duqc d8 nu& cho WiMAX tren the gitri 1.3.4 Citc bang tin Is Viet Nam co khe Ming dinh cho WiMAX 1.4 Truyin sang 10 1.4.1 Dieu the thich nghi 11 1.4.2 CEng nghe sou l& 12 1.4.3 Dilu khien Ong suit 12 1.4.4 Cac c8ng nghe v8 My& tien den 12 1.5 So sinh WiMAX vai WiFi vi 3G 13 1.5.1 WiFi 13 1.5.2 3G 14 1.6 KM kiln chirang CHVONG 2: CAC Ki THUAT SLY DUNG TRONG WiMAX 2.1 Ky thu$t OFDM 16 17 17 2.1.1 Su inh huong cua mai trubng den viec truyen dAn 17 2.1.2 Da song mang (Multicarrier) 17 2.13 CEng nghe OFDM yeti kha Wing km the nhieu 19 2.1.4 Tao vet thu OFDM 21 2.1.5 Cac set dls Mitt the 21 2.1.6 Khoing bio (GUARD PERIOD) 22 2.1.7 Tao cac 10 hieu OFDM 23 2.1.8 M8 tit k, hieu OFDM 24 2.1.9 Ciu trim khung 25 2.2 KT thult OFDMA cho mung WIMAX 25 2.2.1 Nguyen 1y co him 26 2.2.2 Nhttng Se till vact trOi 26 2.2.3 Citc giao dike OFDMA 27 2.2.4 au tree 10 hieu OFDMA vi pit kenh 28 2.2.5 CAu frac khung TDD 30 2.2.6 T6ng quit A khung (Frame) 31 2.2.7 Ckc phin khung (Frame Parts) 32 2.3 KM lu.n chimng CHIJONG 3: GUI PHAP CONG NGH$ WIMAX 3.1 WiMAX c6 djnh - IEEE 802.16d-2004 33 34 34 3.1.1 Lop MAC 34 3.1.2 Lop PHY 42 3.2 WiMAX di Ong - IEEE 802.16e - 2005 47 3.2.1 Lop PHY 47 3.2.2 Lop MAC 52 3.3 Kit hien chwung 56 CHUONG 4: UNG DVNG CC1NG NGH$ WIMAX 4.1 M8 hinh triton khai WIMAX Oleic yen an tray 4p di Ong 57 57 4.1.1 T6 einem tram g6c BS 57 4.1.2 Tinh di gang cka ngutti dOng 57 4.1.3 Chuin sfr dung 57 4.2 M8 hinh triton khai WIMAX veti the yen can tray 4p c6 djnh 58 4.2.1 Thitst bj du cutai khich Wing 58 4.2.2 Chan stl dung 58 4.3 Tinh hinh *ng dung WiMAX * Vitt Nam 4.3.1 liu diem 59 59 4.3.2 Thach thirc 60 4.3.3 Tinh hinh thvc to 62 4.4 Xu hiftng can wimax that gian tot trait qui ma thi gi6i 67 4.5 Tiim Sing cho wimax Viet Nam 68 4.6 Kit lu$n chwung 68 KET LUAN VA BUYING PHAT MIEN DE TAI 70 Kit loan 70 thrimg phIt triin di tel 71 TAI LISU TRAM 101i0 72 DANH SACH HiNH YE Hinh 1.1 M8 hinh mpg WiMAX Hinh 1.2 Minh hos host dOng WiMAX 11 With 1.3 Bin kinh cell quan 110 Ai dilu chi thich nghi 11 Hirsh 1.4 MISO 12 HInh 1.5 MIMO 13 With 2.1 Suy gilun tin hieu theo lchoing cich 17 HInh 2.2 Su tao m tin hieu OFDM 18 HInh 2.3 FDM th8ng thubng vi OFDM 18 With 2.4 So sinh song mang cia OFDM yeti cic hinh thirc Mg& thong 19 Hirsh 2.5 OFDM phit vi thu 20 Filth 2.6 So d6 lch6i cos thiet bi diu cu6i 21 HInh 2.7 Gin dis IQ cos 16QAM dung mit Gray 22 Hinh 2.8 Chin lchoing thbi gian &to cho m8i hieu 23 Milt 2.9 BO phit OFDM song mang 24 Hirsh 2.10 Ctiu frac Tulin thbi gian cial0 hieu OFDM 24 filth 2.11 M8 tit tin s6 OFDM 24 Hinh 2.12 Ciu true khung 802.16 OFDM 25 Mirth 2.13 So slip /cep theo hai chieu OFDMA 26 Hinh 2.14 Sr so sinh OFDM vi OFDM 27 HInh 2.15 Ciu true song mang OFDMA 29 Hirsh 2.16 Kenh pit gip tin s6 DL 29 Hinh 2.17 au frac tile cho UL PUSC 30 With 2.18 du frac khung OFDMA 32 H1nh 3.1 Qui trinh phis loci MAC SDU 34 H1nh 3.2 du tic cila MAC PDU 36 H1nh 3.3 Qui With truyen-nhin 42 Hinh 3.4 Qui Irinh xen ke 44 Hirsh 3.5 du trim khung TDD 46 Hinh 3.6 Ciiu tic khung dutmg xu6ng TDD 46 Hinh 3.7 Chu tnic khung dubng len TDD 46 Hinh 3.8 OFDM yi OFDMA 48 HInh 3.9 Hieu cmg kenh hoe (sub channelization) 48 Hinh 3.10 Dieu chi thich nghi vi mi h6a dtra tren khoing each yeti BS 49 Hinh 3.11 Co che yeu au lap lai 16i xiy 51 HIM 3.12 H6 trq QoS Mobile WiMAX 52 Hinh 4.1 Ng dung da clang ctla Mobile WiMAX 59 Hinh 4.2 Toin anti thung lung Ti Van 63 Minh 4.3 Binh Si ye thiet bj tram g6c BS dugs lip On DSc nhl diem BDVHX 64 HInh 4.4 HInh inh thrc te thiet hi Out door phis Ichich hAng 65 Hirsh 4.5 Hinh inh nu& din Ti Van troy cep Internet 65 fah 4.6 WiMAX tren taxi 68 DANH SACH BANG BLEU Bang 1.1 So sitnh cac chain !PPP 802.16 Bang 1.2 So sloth WiMAX di Ong vi 3G 15 Bang 2.1 MR Gray 22 Bang 2.2 Tham s6 vet 1, cua OFDM 27 Bang 3.1 Cie loci khoi bao mot se dung tong IFFF 802.16-2004 42 Bang 3.2 MA sea 16i dbi yeti cac phuang then dieu chi 43 Bang 3.3 Kich ce kh6i bit xen ke 44 Bang 3.4 Cie phuang thee dieu chi vi MA has dtrqc he trq 802.16e 49 Bang 3.5 T6c dO de lieu lap PHY Mobile WiMAX 50 Bang 3.6 thing hqp ye QoS Mobile WiMAX 53 THU4T Nab VIET TAT AAS AK BE BER BM BS BW BWA CDMA CA CP CPE CPS CRC CS DES DFS DFT DHCP DL EC ECB EDE FEC ETSI FBSS FDMA FDD FEC FFT FSS FWA GPS H-FDD HHO IE MIT IDFT IFFT adaptive antena system Authorization key Best effort Bit error ratio Base station network interface Base station Bandwidth Broadband wireless access code division multiple access Certification authority Cyclic Prefix Customer Premise Equipment Common part sublayer Cyclic redundancy check Convergence sublayer Data encryption standard Dynamic frequency selection Discrete Fourier Transform Dynamic host configuration protocol Downlink Encryption control Electronic code book Encrypt-Decrypt-Encrypt Forward Error Correction European Telecommunications Standard Institute Fast Base Station Switching Frequency Division Multiple Access Frequency division duplex Forward error correction Fast Fourier transform Fixed satellite service Fixed wireless access Global positioning satellite Half-duplex FDD Hard Handoff Information element Internet Engineering Task Force Inverse Discrete Fourier Transform Inversion Fast Fourier transform He th6ng anten thich nghi Khali cAp phep C6 ging toi da Ty le lei bit Giao dien gins tram g6c vi mong Tram g6c Bang thong Truy nh$p khong day bang rung Da truy nh$p chia Quyln chung thoc Tien t6 tan hob Thiet bj din cu6i thue bao Lap plan chung !Gem tra yang du Lap hOi to Tieu chuin mat ma du lieu Loa chip tin se dung Bien al Fourier raj roc The toe du hinh the khang c6 dinh Huang xuting Dieu khan m#t ma Bang mat ma then to M$t ma-m#t ma Ma Ma se I8i throe Vien lieu chum ten thong Chau Au Chuyen d6i tom g6c nhanh Da truy nh$p phan chia tin se Song cang chia tin se Sea 181 huang di Bien dig Fourier nhanh Djch vo ye tinh c6 djnh Truy nh$p khang day c6 dinh Ve tinh ctinh vj tan ciu FDD ben song cong Chuyen yang can Phiin to thong tin TO chat Icy su that Ice Internet Bien doi Fourier rai roc ngtrqc Bien d6i Fourier nguqc nhanh IP ITU KEK LAN LMDS Internet Protocol International Telecommunications Union Key encryption key Local area network Local multipoint distriution service LOS MAC Line of sight Medium access control layer MAN MDHO MIMO MMDS MPEG Metropolitan area network Macro Diversity Handover Multi input Multi output Multichannel multipoint distribution service Moving Picture Experts Group NCFG NLOS nrtPS Network configuration Non line of sight Non-real-time polling service OFDM Orthogonal frequency division multiplexing OFDMA Orthogonal frequency division multiple access PARP Peak-to Average Power Ratio PCMCIA Personal Computer Memory Card International Association PDA Personal Digital Assistant PDH Plesiochronous digital hierarchy PDU Protocol data unit PER Packet Error Rate PHY Physical layer PKM Privacy key management Point - to - multipoint PMP PPP Point-to-Point Protocol QAM Quadrature amplitude modulation QoS Quality of Service QPSK Quadrature phase-shift keying REQ Request rtPS Real-time polling service Rx Reception SA Security association SAID Security association identifier SAP Service access point Thb tic Internet Hiep hOi viers th8ng Qu6c ti Khoa met ma Ichoa mons 110i h0 Djch vv phan ph6i da diem nOi hitt Tia live xa Lop (lieu khiin truy nhip m8i trubng Mang khu Arc phi Chuyin giao da clang rieng Da dubng vim da dubng Djch vp phin ph6i da diim da kenh Nhom chuyen gia nghien cuu WI gang Ciu hinh mpg Tia kheng tnrc xa Djch vµ tham db kheing thai gian thrc Ghep kenh chia tin s6 trvc giao Da truy nhep chia tin sea tnrc giao Cong suit Wong d6i cvc dai Hiep hOi quOc to ye tim mach nher ala may tinh ca nhan That bi vv s6 ca nhin Phan cep s6 din ding b0 Don vi da lieu filo tic Ty le 16i gei Lop vat lf Quin ly khoi rieng Diem da diem Thb tic diem-diem Dieu chi bien dO au phuong Chit luong djch vi Khoa djch pha ciu phuong Yeu ciu Djch vi them db thbi gian thvc Thu Tip hop bao met BO nhin clang tap hop &to met Diem truy nh$p djch vi SAR SC SDH SDU SF SFID SNMP SNR SS STC TDD TDM TDMA TEK Tx UGS UL Synthetic aperture radar Single carrier Synchronous Digital Hierarchy Service data unit Service flow Service Flow Identifier Simple Network Management Protocol Signal-to-noise ratio Subscriber Station Space time coding Time division duplex Time division multiplex Time division multiple access Traffic encryption key Transmission Unsolicited grant service Uplink Rada khe het nit tao Keith mang dun Phan cAp só dog bO Dan vi dtt lieu djch Luang djch va BO nh$n clang luang djch va Tha tac quan 15, mang dcm gian TS, le tin hieu/tap am Tram thus bao Ma thbi gian Idieng gian Song dog chia thbi gian Ghep kenh chia thbi gian Da truy nhap Phan chia thin gian Khoi mat ma luu ltrong Truyen dAn Djch va cap ph& tkr nguyen Huang len ONG DUNG CONG NGI-1C WiMAX 4.2 M8 hlnh trim khai WiMAX vai cic yea tray cup co dinh Khic yeti viec huong tai ngubi clang yeu ciu firth riling di dung, m8 hlnh trim khai WiMAX cho irng clang truy crap co djnh se hying tai viec mang bang thong 16n tai ngubi clang thong qua he thong v8 tuyen Khich hang cia the he thong c6 the la van pheng lam sr* elm the doanh nghiep, c8ng str, cic h0 gia dinh Loai img dung c6 dac diem la yeu ciu mOt toe dO troy cop cao, On djnh nhung 'thong nhit thiet phai di dOng Djch vu WiMAX d6 se thiet hip met loci djch vp c6 QoS three djnh nghia cho phip cung cep mOt bang thong 16n, cam ket ea toc dO toi da va toe dO t6i thieu cho ngubi dung 4.2.1 Thilt bj dAu cull Mulch kdng Thiet bj diu cu6i Ichich hang c6 the dirge lip dot ngoii trbi (outdoor), hoac de tren ban nha (indoor) Phia sau thiet bi diu cu6i lchich hang c6 the not yid mang LAN elm doanh nghiep hay h0 gia With, twang tv m8 hlnh kat not Nen ctia the c8ng nghe 06 day Trong truing hap nay, WiMAX d6ng vai trb cung cap kit not tai dia diem ngubi ding, thay cho he thong cip ding hay cap quang hien 4.2.2 Chitin sft dpng Khi n6i ten lung clang co dinh, nhiau ngubi se nghi ten viec sir dung WiMAX co dinh theo chuin IEEE 802.16-2004 Cho den thbi diem hien nay, Fixed WiMAX da c6 thiet N duet dm xuat (long loft va thin khai vae thvc te Cic tha nghiem Viet Nam cling nhu thee drug INS cui the hang da trim khai thuang mai hea chum Fixed WiMAX, cho they chuin a hoar town chin mai di trim khai the ling dung truy crap co djnh, hoac c6 the di chuyen dirge - portable (nhung qui trinh di chuyen nhanh thi !dieing gift three kit nti) Chuin IEEE 802.16e se doge khuyin nghi di sfr chmg chung cho ci hai loai ling dung truy crap co dinh va di Ong vai cic thiet bj deli cu6i khic nhau: — Vai yeu ciu truy cup di dung, the chip WiMAX se duet tich her vtlo the thiet N cum thy nhu laptop, PDA, dies — Veri cic yeu ciu truy cap co dinh: se sin xuit cic thiet bi diu can khich hang SS theo chitin 802.16e nhung la thiet bj de ban, thiet N cho phdp kit n6i the may tinh ala ngubi ding co dinh vai mang Internet lchang day WiMAX Phan Tim Tang MSV: A13162 Trong 58 ONG D1JNG CONG Na WiMAX ti t f we MIMS •osom •••••• ".” 44— a A Flan% OINN Wee Hinh 4.1 Ung dyng eta eking ciia Mobile WiMAX Viec then khai chi mOt chuan Mibile WiMAX cho ca hai lo3i img dung di dung vi c6 dinh se flit Idem duct tai nguyen ve ten se ding nhu chi phi trien khai tram gec BTS Tuy nhien chuin Fixed WiMAX c6 the duqc tinh toan sir dung di cung cep kit nei backbone cho cac from BS Mobile WiMAX Hok sir dung Fixed WiMAX de cung cep cho cac lchich hang theo m8 hlnh lease line ma hien dang dAng cap quang de cung cep kit n6i Viec tinh toin co nen so' dung Fixed WiMAX hay kitting xin danh cho ck nha quan 1St, cac doanh nghiep, phen vier ctia chuyen de My chi de cep t6i img dung WiMAX vio vied cung cep bang th8ng rung Mei ngteri dung diu cuei v6i cric tinh Wing tru viet Gus ne 4.3 Tlnh hlnh dug dyng WiMAX & Viet Nam 4.3.1 fru Sim Deli nu6c Viet Nam ce dja hlnh va vj tri dja 1ST thich hqp veri trien khai vi khai thac djch vu bang rung ten nen tang c8ng nghe WiMAX Veri dja hinh nhieu san dja ck yang xa, stung cao, v6i chi& dii dit nut keo dai vi nhe hcp viec trier khai ck hlnh thirc truyen din hou tuyin chua phai la giai phip tei uu, c6 nhtmg daz diem ma hem tuyen chug dap img thrqc thi v8 tuyen ma dies hlnh la WiMAX lgi dap img duqc vi hon nets cOn te m rat phil hqp Tiep din to phai ki den thi twang sir dung intemet vi cac thiet bi di dung hti Viet Nam la rat ce dim ruing va c6 lchi Wing lcinh doanh cao Han rata theo dash gia cua cac nhi chuyen gia thl WiMAX la Ong nghe rat pha hqp v6i ck mac dang phat then nhu Viet Nam, ley vi du rum Pakistan, Thai Lan hay Banglades Phan Tien TOng MSV: A13162 Trang 59 IIING DUNG 0*G NM- WiMAX 4.3.2 Thdch thee Nhfing trd• nggi chfnh tti triin khai Winutx tfr Vitt Nam: Thu nhAt li ve bang tin Ching to se phii dqi nhitng "Ong 16n" ten the giOi then khai truck rbi mei vio Viet Nam The hai, mac de Meg nghe hfra hgn v#y nhtmg rat c6 the cat cang ty vien thong lien lac hin se nglin ngai tong viec trier khai Wimax vi lo ngai se gay that thu cho cic djch vµ SMS vi voice Vu cutoi cling, thich they lan nhit cua Wimax la viec clA bj cic dei the di three chiem het thi phin Xet ve mat Ichic, ding nghe WiMAX rat uu vitt nhtmg vin c6 !thong it nhling Ich6 ;chin kW D61i gii ci thiet bj diu cuei hien can dit; c6 s6 lugng han che cic nhi sin xusit cic thiet bj cu6i; viec chan hoi thiet bj kh6 clang nhit ning mem deo; linh host (flexibility) Ma WiMAX Ben canh de, WiMAX dva ten nen IP nen viec ket n6i, dinh se, chit luring (Lich vu, bio mot vi an thin mpg can nghien cuu cu the WiMAX li mOt giii phip tuyet voi ve mat c8ng nghe ket not nhung se can mOt chi phi km phii be de phit trien tang cho mOt he thong mei tong he thong cil yin can chua duqc se dung het Qui thvc, neu phii diu to met khoin kinh phi de then khai WiMAX ten mOt quy m8 len tong c8ng nghe 3G van li tiern fling chua khai thic het thi chic chin Mc cong ty vier thong se phii tinh tan vi can nhic het sue ky luang twee be den dau to cho viec phit trier djch vv niy Thvc to trien khai WiMAX tai Lio Cai ben earth nhling tin hieu Lich cvc thi qui WW1 thu nghiem cling da St hien nhOng diu hieu kheing may !chi quan De 14 vong 16n vio Wimax, song kiem tra trrc tiep tai diem thu song thi ket qui lai chug nhu mong muen — Diem thu song tai tram Viba Cam Dueng„ rich tram phit 9,5 Ian, miy thu chi hien 3/9 vach song, diem thu b vi ti tuang del cao, Ichang bj che chin — Diem thu tong thj xl Lio Cai, cich tram phit song trung tam Ian, bj cay xanh che chin, at miy thu tren mii nha thu duqc vach song Twang hop at may thu du& oat thi chi thu duqc vach sting — Tai nhi nghi cea Btru dien tinh Lio Cai, cich tram phit trung tam 3,2 km, neu oat dung twang c6 the thu duqc den vach sting Tuy nhien, Mc chuyen gia Vien !MKT btru dien trim tiep di do, dainh gii he thong, nhiln thiy: tong dieu kien thbi tat binh thutmg, sting phit to tram phin n vio cic vat can twee den diu thu, Ang ten djnh hueng mei thu duqc Te de c6 the ket lu$n, song Wimax khOng On djnh , phu thuOc nhieu vio hien dung Ma v$t dm, then tiet Phan Tien Tking MSV: A13162 Twang 60 ONG DUNG CONG NGHe WiMAX Trong 19 diem thu sing Wimax ngiy diu tien thi mot diem kh8ng thu duct sting nhu tit totin vi dA phii chuyin sang dirt diem khic Theo cic chuyen gia vier th8ng, an cAn nhic, luu y dic biet viec thu sting phi!' xtt Wimax trait trien khai rung, nhit li tai cic thinh ph616n vit cAn lien tut they d6i Khi mot c8ng nghe mai &it lutin o5 nhftng y kien khic ve c8ng nghe d6 vi WiMax cling khang phii lA mat ngoai le Vii nhftng tinh riling uu viet vA fling img dung to lam WiMax dA mau ching gitinh dtrqc su quan tim dic biet cia cic nhi sin xuAt thiet bj, cic t6 chic, cic doanh nghiep vA ci ci nhAn Song cling khOng It nguai can to hoii nghi ve c8ng nghe nAy vi cling nhu riling cia ne se lint thay d6i djch At kit n61 mang Internet ttrcmg lai vi nhftng 19 cia str hoii nghi Trutc het ve mit kY thu$t WiMax can co mat s6 nhuqc diem sau: — Ve mAt dii ten me WiMax su dung kheing tuong thich tai mqi quitc gia dieu nAy se hurt the nAng phi bien cia WiMax tai thing (Ric gia — Vin de bio mit cia WiMax duqc dinh gii lA can rat nhieu 16 hing di dei hii cic !IA cung cap dich vµ phii mau chang giii quyet van de ay — Ve chuan cis WiMax cling rat ding nii tad bil vl WiMax li mat chuin c8ng nghe nhtmg lai chua duct chuin hot "hien tai thi WiMax dang sfr dyng taxi 10 c8ng nghe khic vA ca tai dung nen ca se chua the lien th8ng ttrcmg thich" — Ve thi twang thl WiMax can phii chiu sty ctmh tranh mtuth me vii cic c8ng nghe khic nhu : Wi-Fi mot ding nghe dA tra nen phi bier dai vii cic rank phit trien, kat nal Internet c6 dAy din nhu DSL, cia mung dien thoui di dOng vein dang phit tan mot cich het sirc nAng dung vi cic c8ng nghe thay the khic nhu mang d8 thj cult cic nuOc chiu Au hay c8ng nghe HSDPA (High Speed Downlink Packet Access) dinh cho diet' thoai di dOng Mil ciu hen ve gii cia nhftng diet bi phut vu cho vier trien khai, lip dit Wimax can dang be ng6, thi nhieu nguai dA bin khoAn ve yin de "tin so chuin cho Wimax" Bei le, nhftng dii tin chart Wimax Icheing the cap cho qui nhieu nguai Ithong c6 the phi Whin du in then khai Wimax tai Lio Cai li mat du an mang firth xi hOi cao, hia hqn lint thay dai cues sang cho nhftng nguai din mien nii, yang cao Viet Nam, ttto dieu kien cho hq Quay flap xfic veri c8ng nghe mai Tuy nhien, tan khai the nio cho hieu qua, cho phi hqp yeti nhu tau vi ning kinh to cia dja phuong mai IA vein de ding nii Phan Tien Ting MSV: A13162 Trang 61 ONG DUNG CONG NGH$ WiMAX 4.3.3 7Ink hinh thitc tai Thuc Wong WiMAX Viet Nam hien 11 rat c6 then vong Sau tit* nghiem Lao Cai chtra duce darth gia cao lim nhien hien cac nhit khai thac dich dang tfch cue trien khai vi thU nghiem c8ng nghe mei nay, vd: ngtly 16/10/2007, Motorola da t8 clam bu6i heti thito chuyen de ve WiMAX yeti nhieu thong tin vi tinh hinh WiMAX tren the gibe vi mOt s6 khuyen nghj cho Viet Nam VNPT la tap doin di diu via trien khai thin nghiem deg nghe WiMAX Chimg to se di theo 10 trinh thin nghiem WiMAX cult VNPT a Tank hinh Irian khai HIM= tel Lao Cat Trong giai doon tfr thing den 12/2006, tap doan Intel, VDC vi Ca quan hop the phat trien qutic to Hoa Kt tai Via Nam (USAID) phoi hop thin nghiem cong nghe bang rung kh8ng day c6 djnh Fixed WiMax 802.16-2004 Rev D6i vai ten s6 3.3 GHz - 3.4 GHz tth 19 diem Lilo Cai g6m ctic trueng hoc, co s6 y te, diem butt dien van holt, uy ban xe, doanh nghiep vita vi nhe vi mOt gia dinh ding dan chtra tang tiep Vic v6i ding nghe hien 4i Djch vu ductc dua vao lit* nghiem la tho3i vi Internet the dO cao, c6 414 chi phi 500 000 USD - 600 000 USD Butte diu thi qui trinh trien khai thf diem WiMax tai Lao Cai dit dot ducc nhftng thinh Ong ban diu nhu: Tai tru?mg THCS Van H6a thl hoc sinh day di c6 ca hOi tikp can WA Internet the dO cao ngoii they c8 vi cic em hoc sinh day duce dung en thoth Internet v6i chat luting tot Toi tnmg tam y th xl Bic Cutmg clic y tai trung tam da dupe tiip can WA Internet the dO cao vi thoth IP tit ci deu hoot dung tat vi phat huy duce hieu qui Thing 5/2007, VNPT tap tuc cung cap thtl nghiem tth 11 diem cfut Ta Van chi.% you hi dm h0 dart, UBND xti, tram y th, throng thing hoc co s6, diem BDVH Phan Tien Tang MSV: A13162 Trang 62 UNG DUNG LONG NGlie WiMAX Ilinh 4.2 Toan canh thung Ifing Tit Van Sau c6 cic th8ng tin ve ket qui du in thir nghiem WiMAX tai Lio Cai sau thing Gila mOt so phucmg tien th8ng tin 41 chting, 41 dien cho nhi sin xuAt thiet bj WiMAX - Alvarion (Israel) vi dai dien Cang ty Dien toin vi Truyen s6 lieu (VDC) d8 c6 bad lim viec vi truc tiep len Lio Cal kiem tra, xem )(it lai toin b0 he thing WiMAX da tit* nghiem thbi gian qua Qua kiem tra toin bO he thong, 8ng Nguyen Minh Dire - dai dien cho Alvarion dit dua mOt so nh$n djnh ring tai Tnrting PTCS Van Hai li diem xa nit& eta he thong, to et: ly li 4,7 km (do tren bin de) he thong WiMAX von hoot dung rat tot tong sued qui trinh tit* nghiem Deng thbi diem lip dat khtc tai xa Van Hoi, cich km Gang lutm hoot gang tot li "diem buu dien Van hoar xa Ngoii cic diem khic tai phubng Bic Cubing yeti diem thin nghiem WiMAX li throng PTCS Bic Cubing, nhi 8ng Vuang Trung Thin, tong ty diu to xay dung Cling trinh vi Tram y to xa Bic Cubng hien tth hog dung tot Tuy nhien, truck d6 c6 y kien cho ring tai hO 8ng Vuang Trung Thin, tin hieu WiMAX khOng tot Nguyen thin li lei phin nhting chit hoin tan khOng lien quan den phial cling thiet bj VAn de niy da duqc VDC /al ly xong Tai Tram y to Bic Cubing, sting Dirc kiem tra thi thiy CPE khOng thu duce tin hieu Nguyen nhin li tai thbi diem lip dat, CPE hutmg ve iingten tram g6c Tuy nhien, sau 46 khoing thing, c8ng an ILA Bic Cubing xily dung try sb lam viec Mth ngei ctia toi nhi chin ngang dubng thu song elk CPE vi xung quanh de khOng c6 cic toi nhi/vat chin khic de too song phin xa nen CPE khOng thu ducat tin hieu nhin thing deng thbi ding khOng thu dupe sting phin xo Cic ben da xfr nang cao CPE them met vi dung thiet bj SAU de mirc tin hieu elm CPE 4t 7/9 stitch sting vi toin b0 thiet bj da hoot dung tot Phan Tien Tang MSV: A13162 Trang 63 ONG DUNG CONG NGHE WiMAX Tram y to xa Von Hoa la mOt nhttng diem du kien thir nghiem, nhien can bO Icy thuat ctia VDC va dpi dien cos nhtl sim xuit thiet bj WiMAX dit kiem tra va they khong thu$n lqi nen da chuyen sang thu nghiem Sa NOi Vu ph6 Nguyen nhan la tai diem Van Hol chug ce dieu Icier) de xay cOt angten lip CPE, chi c6 ng8i nha thip khoang each xa (lion 7km) bj che chin nhieu bei d6i Tai diem khac nhu Diem Van hoa xa Von Hol, dieu kien dun nhin N che chin nhien tin hieu thu phat van rat tot nhat ding nghe ghep kenh phan chia theo tin so tut giao-OFDM va c6 m8i tnrimg cho sting phAn xo Doi v6i chit luqng thoai VoIP tren nen Cong nghe WiMAX, theo khio sat cita Butt dien Tinh Lilo Cai ming nhu VDC hay Vien khoa hoc Icy thuat butt dien du chit luqng djch vu VoIP tren nen cong nghe WiMAX IA tat, am rei rang, khong tieng vong, hien ttrqng ver tieng Hinh 4.3 Hinh cinh ve thilt from gic BS dtipt lip Irk mac nha dam BDYHX Tuy nhien ba loai thiet bj VolP sttir dung giao thirc SIP duqc sir dung lin thir nghiem bao gam IP Phone, ATA - Analog phone va Wifi phone thl chit luqng thiet bj cda Wifi phone kitting tat bing hai loci lai, dOi !chi c6 hien Wong vrt tieng, pin kern - chi thut hien duqc vii cuOc goi mOi cuoc phut la het pin Qua trinh thtl nghiem cho thiy neu cal thien duqc chit luqng pin thl Wifi phone c6 the stir dung duce Do v#y ma chit luqng tho3i khong on djnh nguyen nhan lA 18i mia thiet bj Vol? chir Wing phiti 16i cos c8ng nghe WiMAX Phan Tien T(tng MSV: A13162 Trang 64 ONG DUNG CONG NGH$ WiMAX Hinh 4.4 Hinh cinh thvc te r thiet bi Out door phia khtfch hang Vt viec Vol!' chua dtrqc se ding nhilu met so dia diem thir nghiem 11 do: Ulu& Ich6 du in thir nghiem, c6 line thoai di ket not gifts he thong VoIP 0111 nghiem vi he thong dien thoai truyin th6ng PSTN nen chi c6 teli da cuOc gqi c6 the thvc hien, deng th6i d6 xity tinh tic !chi nhie'u hon thug bao can thvc hien cuOc gqi ngoii mpg PSTN; line thoai de gqi ngoai nay, chang to eau hinh clulin ac cuOc gqi di dung va lien tinh, chi thvc hien duqc ac cuOc gqi nOi tinh nen nhu ciu sfr dung rot hp chi mot s6 dei tuccng ngubi s6 dung nhu ctic doanh nghiep hay ca quan hanh chinh dja phuong p Binh 4.5 Hinh anh nguoi ddn Tti Van trio? cdp Internet Cac thug bao VoIP da tai buu then van hoe xi Van Holt, mot xa vilng sau yang xa la hot dung nhieu nhit, phuc vv cho nhu au ctla nhfhig h0 din caa xi Trung binh m6i tai day phat sinh han 10 cuOc gqi Ming ngubi din xung quanh day chua c6 diet' lcien bj cac thus bao en thoai PSTN ding nhu nit ngheo nen he thong da phit huy the dung rat t6t tai diem Dva ten nfring an cir de, dpi dien phia nil& dm xuat dua nhon dinh chit luqng dich vv VoIP tren nen cong nghe WiMAX la tot viec VoIP chua duqc clang Phan Tien Ting MSV: A13162 Trang 65 ONG DUNG CONG Mt WiMAX TIMM ef mOt so dja diem thir nghiem li chti quan ngubi sir dung chti khOng phii yeu t6 c8ng nghe Tai nhOng diem thvc sir kW) khan ve tut tang vitt th8ng, diem Internet ding tong thi su dung nit hieu qui Ve kith riling chju Am vi nhiet dO eta thiet N WiMAX, 4i dien nhi sin xuat khing djnh /Lang thong chju vai thbi flit cos thiet bj li rat tat va tinh toga the th8ng s6 k$t thgt nhi sin xuAt dA tfnh den nang cheing chju caa tin& bj dat ngoii trbi Ngoii ra, thiet bj WiMAX tit* nghiem dude sin St bei hang Alvarion - Israel vi da dirge then khai, kiem nghiem thvc ti tai han 200 diem lip at tai hon 80 quoc gia tren the giai vi diu thu dirge kit qui rat tot b Sa haw film Wine oh* Irian Bit mOt c8ng nghe mai nio dbi cOng diu can den mOt khoing thbi gian tiep can thj trubng, WiMAX ding khOng slim ngoii quy luot Tuy nhien, xet tren g6c dO thj tnyang rung 16n la thi Wong town du, ke tn dbi cho den WiMAX von nhOng budc tien nhanh thong, manh me vi A/Ong chic thl cho da van dang giai down nhung WiMAX da cho thay la mOt c8ng nghe uu viet, do rat thich nghi voi thj trubng khich hing d8ng dio vi Ich6 tfnh Do v#y theo dv bio tea Mc nhi chuyen man giiu kinh nghiem thi thbi gian tiep can thj trubng till WiMAX se khOng phii dal qui Mu Vi phi a khich hang, nguai to khOng quan tam nhieu vi mOt thutit, c8ng nghe ma quan tam nhieu din Wing cung cop caa djch vu gig ca phii Ix& de sat dung djch vu Doi v6i WiMAX day !thong phii la dieu gl qui kh6 khan vi la mOt ding nghe tien tien hien cho nen n6 c6 !tang cung cap dirge nhttng loci hInh dich vv bang rung ma hien dang c6 tren thj trubng tren bang thong rung ctia ne tit giii trf den hac top nghien cuu hon nfta theo du firth ctla cic c8ng ty that nghiem thi gig ca tea WiMAX se khOng qui cao bai vi n6 dang ten dubng cash tranh vOi c8ng nghe ADSL hien MOt ma ngu?yi tieu dAng mu6n co WiMAX la toe dO download nhanh, of du nhu MI video, truy cap tir xa toi IPTV vi Vow Doi yeti nhi cung cap, quan tam den lqi nhu‘In dat duqc, theo nhu dv tfnh, chi phi ban diu cao nhtmg gii trash cho WiMAX Icheng phii la khOng canh tranh duqc v6i ADSL hien thbi vi la ding nghe mai cho nen rat co tiem tiling phit trien Dieu dang tiled thtic huang tai dog nghe mai caa cic nhi khai that Bich vu vien thong, them mOt 19 lchic de la thj trubng lchich hang rung ma clang chef dqi ha, n6 se thac day qui tranh the nghiem vi khai that WiMAX tren quy m8 the gi6i Phan Tien Tang MSV: A13162 Trang 66 ONG DUNG CONG NGHe WiMAX Doi vii chinh phi.% cac nude, WiMAX phat trien dkg nghia vdi viec tao dieu kien phat trier cho mpg luei quer' chinh phu thong qua mpg vien thong He se clang ham viec quim 1ST deg din, hoar chinh buck lien chinh phu dien ta, tang Idle Ming ph6 cep tieng net vi quimg bi cho nha mr6c vey chinh phu cac nude, tU nude phit then cho den nude dang phat then deu Ichuyin Ichich vi dang ma rung cap phep cho the thin nghiem WiMAX a Ti nhttng nhen djnh tren ta they ring WiMAX tren thj trubng the gidi ce tiem Ming phit then nit 16n, hOi ty day de cac yeu to kg thuet c8ng nghe cling nhu kinh ti (cung vi cau) Cling vii sum cap phep cua chinh phu cac nude WiMAX se phit then tom ► dien met tmmg lai khang xa 4.4 Xu hitting cua wimax that gian tat trail qui ma thi gidi Mtn da !Man dinh d phin ten WiMAX la Ong nghe co tiem Ming phat trien rut ldn ca ve chieu rung iL chieu sau: — Chieu ring: se fiep tic ce nhik giay phep cho thtl nghiem vi khai thic tren nen WiMAX, hien thai ce tren 80 quec gia cho phep thir nghiem WiMAX, se se can tang I8n mOt rich nhanh thong that gian ten nhu cau sit dung mang vier thong tren the gidi ngiy cling nhieu vi hien dang bi qua W — Chilu sau: cac nha nghien eau, cac can bO ky thuet ce tech nhiem dang vii se trop tuc nghien cac chuin hien tie de cling homn thien c8ng nghe WiMAX 3G My Hien nay, theo nghien elm cuss c8ng ty nghien cut thj trubng vier thong Maravedis, m#c de tinh hlnh kinh to am dam nhung thj trubng djch vu mpg bang thong rung yin dang tang twang d#c biet la djch vµ WiMAX Cong ty Yota (Nga) la c8ng ty eau fien then khai cung cep djch vu bang thong rung WiMAX, ngoii viec tiep tuc phat trien thj truing nude tin Yota cung then khai mpg WiMAX Managua, Nicaragua vat ce ke hoach tpi cac thj tnrbng Belarus,Peru My cling dang then khai mang WiMAX tpi cac ph6 Kansas (hen 12.000 dem vuOng), Houston (1.900 dem vuOng vdi trieu nguai clang) Tai Chau A, WiMAX di ducp mOt so nude quan tam ling dung vao thuc tilt; cu the tai Tay Bic An DO vi Indianapolis, nguesi ta di sir dung WiMAX de truyin the thong tin ve giao thong gift') cac lai xe ce the chit dung hen; tai DM Loan, khich hang cos hang taxi M co the xem phim, hitt Web, nghe nhac Ulm tuyen Ichi di xe, lchach hang ce the su dung yeti met man hInh gin ?r ghe sau cda xe taxi (inh duel) Phan Tien Teng MSV: A13162 Trang 67 °NG DUNG CONG NGHE WiMAX Hinh 4.6 WiMAX tren taxi 4.5 Tam thing cho wimax Vitt Nam WiMAX co djnh cing nhu WiMAX di dOng mang tinh dong hank vit cling phat trien Dieu Ichang mang tinh mau than nhu ciu khich hang kh8ng phii li chi theo mOt nhu ciu nhat djnh ma c6 nhang bO phen yeu ciu tinh di dung cao c6 thing ngteri lai yeu ciu mOt chit luqng tot han nhieu ma khong phai la firth di dung that cao D6i vai cic thiet 131 di dung tit nhien duqc stl dung yeti he thong ceu hinh vat the cling nh6 gqn cling tien lqi se am gitim kha niing tuang tic voi tram g6c, vai thiet bj co djnh tai nha thi !thong yeu au vl kha niing di chuyin nen thiet bj c6 the co duce kich Or to han nen hieu suit may thu se tot hon Vii s6 luqng Ichich hang d8ng dio va nhu au bang rung rit 16n, Viet Nam la thi twang tiem niing cis cic nha Ichai thic dich vu villn thong dun tree co se ding nghe WiMAX vai thing uu diem not bat va tien ich dui no 4.6 Kit lutn chiming Mang WIMAX cho phip phti sang pham vi rung, t6c dO truyin tin 16n, cho phip nhieu thus bao ming truy nhap vii cic dich vp nhu VoIP, video Vol chit luqng cao ma ca ADSL cling chua dip ling tot duqc VI v$y WIMAX cho phip nheng ving ma truck day ADSL chug wan tai duqc thi cling c6 the truy Op Internet WIMAX cho phip cic ding ty vai nhieu chi nhinh thinh ph6 Ichong cin lip d#t mang LAN ma chi cin at mOt tram BTS phi sang ca khu virc hok ding Ic}7 thug bao hang thing vai ding ty cung cap dich vv De c6 the truy cep tai mang thi cic thus bao duqc cung cap mOt ma s6 rieng va duqc giai han quyin truy nh#p theo doing hay theo lch6i luqng th8ng tin nhin tir mang Nhin chung c8ng nghe mai se tic dung din mOt s6 met ca ban sau: Phan TiEn Tong MSV: A13162 Trang 68 UNG D1JNG CONG NGI-le WiMAX WIMAX se giftp clic nhi khai thic di Ong Mang phv thu0c vao dubng truyIn phai di thue cilia nhi cung clip mang hilt tuyen VI ngby hitu het cac dubng truer' gitta BSC vi MSC hay giita clic MSC voi deu 11 cap quang, hoac vi ba diem diem Vi v$y ducrc thay the thi cac djch vv di Ong se tang len ve dung lugng de c6 the trien khai them ctic djch vv mai ten vung bao phti rung Ve mat xa hOi thi v6i phain vi phu song rung 16n va chat luong cao, toe dO lon WIMAX cung gitip mOt phAn dAc lIrc cho cac km luqng an ninh, ciru hol hay cic ta chirc ciru he c6 the trl lien lac nhieu dieu kien thai tint, dja hInh Ichic phvc Ai cho nhiem vit Gila mirth Phan Tien Tang MSV: A13162 Trang 69 KET LUAN VA HUONG PHAT TRIEN DE TAI !CET LUAN VA HUIONG PRAT TRIEN DE TAI Kit lu$n Vei muc tieu 16 tim hieu ding nghe truy nh$p ve tuyen WiMAX Qua nghien cthi, phan Lich, so mirth vi dinh gii thvc hien nOi dung chuyen dZ c6 the rut ket lu$n nhu sau: — WiMAX li c8ng nghe truy nh$p va tuyen bang rung duqc phit trim dva tren ho tieu chart IEEE 802.16 vol hai lieu chulin chit yeu duqc ip clung da duce thong qua 11 IEEE 802.16-2004 li co se, cho phien bin WiMAX c6 djnh vi lieu chain IEEE 802.16 e l6 co se cho phien bin WiMAX di dung — Dien din WiMAX lit mOt te chirc gam cic tang ty cung cep thiet bj, nhi cung cap djch vu, nOi dung de cling lira chon cic tieu chutin cic tieu chart IEEE 802.16-2004 vi IEEE802.16e de dim cic profile cho WiMAX Cic profile ye WiMAX di duce dies din WiMAX thong qua vi lit cc se cho viec sin 'truth thiet bj, dieu Wily cho phep cic nhi sin suit c6 ning hop tic de cling phit thin thiet bj, gam cic chi phi cho nghien phit then, glint gii thinh sin phim — COng nghe OFDM vei ninitng tinh nAng nOi trOi nhu /tang chOng nAng se dung phi cao, cho phep truyen tin vei tee dO cao duqc sir dung WiMAX c6 djnh da cho phep he thong c6 thing lim viec tot mai truang NLOS vi Mc dO truyen tin cao — Phien bin WiMAX di dOng dva tren lieu chart IEE802.16e 11 sir be sung cic yeu ciu cho tieu chart TER 802.16-2004 dA be, sung nhitng tinh Wing mem deo vi hieu qui hon Viec sfr dung OFDMA phien bin WiMAX di dOng cho phep stl dung linh boat vi hieu qui hcrn bang thong, cOng nhu tang cubng cic niing cho an ten, Ngorli yeti phien bin My ho trq them nhieu tinh niing khic nhu chit luqng djch At, bio met vv — So yeti cic clang nghe truy nh$p v8 tuyen bAng rung c6 cung pham vi img dtmg, WiMAX li cOng nghe ding nhon ducrc sv quan tam dtic biet cfia ci cic nhi sin xuat cOng nhu ngtrtri cung clip djch vtii vi nguoi sir dung nhe cic d#c tint' nOi trOi cola no, d#c biet nhu ciu truy nh$p dit lieu ngtly ring manh V6i viec WiMAX duqc tai uu cho djch vµ de lieu, WiMAX e6 the song song tan tci cling vei cic mang nhu 3G duqc t6i uu cho thoai Thy Phan Tien Tong MSV: A13162 Trang 70 KET LUA/s1 VA HUONG PHAT TRIEN DU thuOc mvc dich cM nha cung cep, yeu ciu ldiach hang, cac mung se cO sv phat trier tuang img Voi !chit rang cung clip cac djch vµ truy nhip bang rOng cho ca c6 djnh vit di ding, WiMAX la lira chip mang firth quyet dinh cho cac nha cung cap djch vµ nhilm chiem lint' thi throng cling nhu tang khri nling cimh tranh ctia mirth Hieu r8 cac clic diem k9 thuit, van dung vao cac dieu kien thvc to di thin khai he thong mOt cach nhanh cheng va hieu quit se dem 13i nhitng kM clang het sirc lan cho cac nhit cung cap djch vp vi ca ngtrai sum dung Viec thin khai WiMAX tai Viet Nam se dap img duce cac den hei mOt lon ye nhu cith truy nh$p bang rOng, gbp philn thiic day kinh to phat villa, dac biet 111 cac khu vvc nong them, mien nui vi cac khu d8 thi mei Hiroug phit train di Si Trong pharn vi di tai nay, em di tam hieu cling nghe ciut mang truyen din khong day WiMAX Tren day em chi dm Mau hai chitin thong dung ciut WiMAX la 802.162004 vi 802.16e Hien nay, ngteri to dang nghien ctiu nhieu han de hotin thin Bong thbi day la mOt he thong truyen din lchong day nen can nghien ciru ki han vi bito mit cM he thong Do do, di tai co the phat trier theo nhitu huCmg !chic di cho de till gin veri thvc to han HuOng phit trier de tai nhu sau: — MO rOng tam hieu cac chutin kink nhieu mac han; Ching han nhu 802.162009, 802.161, — Di sau tam hieu bien phitp bito m$t cM he thong MOt litn nits em xin Chan dun an cite that' c8 giao, bun be, gia dinh da !Nit tinh gii►p der em hart tot ban chuyen di tot nghiep cr5a mlnh Die biet em xin chan cam an thiy HoAng Trong Minh la thiy giito frac tiep huang tao dieu ;den vi chi bio cho em su6t thbi gian em hob chuyen de Phan Tien Tang MSV: A13162 Trang 71 TAI LItU TRAM KHAO [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 "3GPP2", (March 2004) CDMA2000 High Rate Packet Data Air Interface Specification [8].John Wiley & Sons, Ltd, (2006), The Business of WiMAX [9] WiMAX Forum white paper, WiMAX's technology for LOS and NLOS environments [10] WiMAX Forum white paper, The business case for Fixed Wireless Access in Emerging countries [11] WiMAX Forum, (November 2005), Fixed, nomadic, portable and mobile applications for 802.16-2004 and 802.16e WiMAX networks [12] WiMAX Forum white paper, IEEE 802.16 Standard and WiMAX igniting Broadband Wireless Access [13].InTech-Quality_of service_differentiation_in wimax networks [14].www.ieee.org [15].www.quantrimang.com [16].www.svbkol.org [17].www.vnpt.com.vn [18] www.wimaxforum.org [19].www.wimaxpro.org [20].www.wimax.com [21] www.3c.com.vn Phan Tien Tang MSV: A13162 Trang 72 ... ctia WiMAX di duqc IEEE dua nhu sau: Binh 1.1 Md hinh wing WiMAX Fixed WiMAX (WiMAX co djnh): Dora tren lieu chuin IEEE 802.16-2004, duqc thiet ke thich hqp cho clang truy nhkip c6 djnh Trong. .. WiMAX thong WiMAX b vang n8ng th8n, vbng Mu, vang xa, b d6 c6 the cho phep he thong WiMAX phat veti deg suit cao han de giarn gig then Mug he thong WiMAX VI voy, de nghj cho phep trier khai WiMAX. .. bin true mang truy cep WiMAX se duqc tr1nh bay chuong tiep then Phan Tien Tang MSV: A13162 Trang 16 CAC KT THUAT Sir DUNG TRONG WiMAX CHMING 2: CAC KT THUAT SlY DUNG TRONG WiMAX 2.1 Ky thuet OFDM