Nghiên cứu chất lượng dịch vụ trong Wimax.PDF

TONG QUAN VE He THONG WiMAX
CHIXYNG 1: TONG QUAN VE H$ THONG WiMAX
1.1. WiMAX la gi?
WiMAX (Worldwide Interoperability for Microwave Access) la mot deg nghe
khOng day bang rung, h8 trq khii !tang kit
noi
bang thing rung
toc
dO cao cho ci mpg
co
djnh lin mpg khong day di gong. Hai phien ban ctia WiMAX di duqc IEEE dua ra
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 phien ban nay sir dung ky thu$t
ghep kenh phan chia theo
tin s6 trtrc
giao OFDM (Orthogonnal Frequency Division
Multiple) hoot dung trong ci m6i trubng shin thing - LOS (line-of-sight) vi kitting
nhin thing - NLOS (Non-line-of-sight.
Mobile WiMAX (WiMAX di dung):
dua tren fieu chuin IEEE 802.16e, h8 trq cho
clang di dung, cung cep khi tiling chuyen yang - handoff vi chuyen mpg - roaming.
Tieu chuin nay sir dung phuong thirc da truy c$p ghip kenh chia tin
so tnrc
giao
OFDMA (Orthogonnal Frequency Division Multiple Access) - li su ph6i hqp cc5a ky
thuot ghep

kenh
va lcy thuit phan chia tin
s6
c6 tinh chit Ulm giao, nit pht hqp voi
m8i trutng truyen dAn da dubng nhim tang thong luqng ding nhu dung luong
tang dO linh hoot trong vies quin ly tii nguyen, liin dung
tai
da ph6 tin, chi thin khh
Ming phh song yeti citc loci dja hinh da dung.
WiMAX da
ducc
phat trien vi ;chic phuc duct nhitng nhuqc diem cult citc c8ng
nghe truy c$p bang rang tru6c day, cu the:
Phan Tien Tking
MSV: A13162
Trang 2
TONG QUAN VE Ht THONG WiMAX
—
Ciu true mem deo: WiMAX h6 trq clic ciu trim he thong bao
g6m
diem da
diem, c8ng nghe lir& (mesh) vi phu sting khip mqi not Dieu lchien truy nh$p
m8i twang - MAC, phut:mg tien truyen din h6 trq diem - da diem va dich vu
rang khip b6i

mOt khe thin gian cho m6i tram di dang (MS). Neu c6
duy nhit mOt MS trong ming, tram g6c (BS) sE lien lac v6i MS tren ca set
diem - diem. Mat BS trong mOt ciu hinh diem - diem c6 the sir ding anten
chum hgp han
a

bao phu clic khoing each xa han.
—
Chit lueing djch vu QoS: WiMAX c6 the dirge
t6i in
dOng d6i yen h6n hqp
luu
luqng sE duct mang. CO 4 loci djch vu dirge h6 trq: djch vu tip phut to
nguyen (UGS), djch vu hei Wong thbi gian thvc (rtPS), djch vu hal yang
khOng thin gian thirc (nrtPS),
n6 km tot
nhit (BE).
—
Tries kluti nhanh, chi phi thip: So sloth von
trien
khai care giii phap co day,
WiMAX yeu eau it ho#c kh8ng eh bit rent sir xay dying thiet lop ben ngoli. VI
du, duo h6 de Mo ranh cat dubng cap thi kh8ng yeu c$u. Ngotli ra, doa ten
clic chuin m6 cha WiMAX, se kh8ng c6 so dOc
guy& ye lieu
chain nay, din
den viec chnh trash chit nhilu nha sin xuit, lam cho chi phi diu to mOt he
thong gut= ding ke.
—
Djch vu da mat: Cach thirc not ma QoS dirge pha
►

phtit n6i chung doa vac so
thea thu$n mire djch vu (SLA - Service Level Agreement) gitta nha cung cap
dich vu va ngubi sir ding
cu6i can. Chi

flit han, mOt nha cung alp djch vu
c6 the cung cap clic SLA khac nhau tai care thug bao ldiac nhau, thklm chi till
nlittng ngubi dhng !chat nhau sir ding sung MS. Cung cep truy nh$p bang
rung
co
dinh tong Meng khu voe d8 thi va ngotti 8, not chit luqng cap deg
thl kbm ho#c dim vao 16.6 khan, khlc phuc thiet bj
s6
tong nhttng yang met
da thip not ml cat nhan
t6
c8ng nghe vh kinh ti thyt hien phut trier bang
rang rut thich thirc.
—
Tinh Wang thich: WiMAX duct )(Ay (long de tors thinh mOt chuin quOc te,
Mo ra so
a
ding d6i vdi ngubi dOng
cu6i
sung
a
truyen tai vi sir dyng MS
chit hq 6 clic vi tri khitc nhau, hetet yeti cat nhti cung
cap dich vu khac
nhau.
Tinh tucmg thich bito ve so ditu to cua mOt nha van hash ban diu vi n6 c6 the
chqn lira thiet bi ttr care nhi

thiet
—

Di ding: IEEE 802.16e b6 sung them tic dec diem chinh h6 trq khi !rang di
dung. Nhttng cii
den
lap vat ly OFDM (ghep kenh phin chia
tin so titre giao)
va OFDMA (da truy nh$p pit chia tin s6 trot giao) de h6 trq cat thiet bi va
the dich sit tong mOt m8i tnrbng di dung. Nhttng cii lien nay, bao
g6m
Phan Tien Tang
MSV: A13162
Trang 3
TONG QUAN VE Ile THONG WiMAX
OFDMA mit rung duqc, MEMO (Multi In Multi Out - nhieu diu vac nhieu
diu ra), vi h8 thy del vat the dO idle/sleep vit handoff, se cho phep kha Wing
di dung (fly du 6 the dO tea 160 km/h. Mang WiMAX di dung cho phep ngtriti
sfr dung c6 the truy cop Internet khang day bang thong rung Ali bit cu dfu c6
phi sting WiMAX.
—
Hog dung NLOS: Khii tiling hog dung curt mang WiMAX ma Idling did hei
tern nun thing gitta BS vi MS. KM Wing My cos n6 gift') ac sin phim
WiMAX phAn phit dii thong rung trong met mei truing NLOS.
—
Phu sting rung han: WiMAX h8 trq dung nhieu mire dieu chi, bao gem
BPSK, QPSK, 16QAM, 64QAM. Khi yeu au yeti bO khuich dg tong suit
cao vi hog dung vol di& the mire thip (vi du BPSK ho(ic QPSK). Cac he
thong WiMAX c6 the phi sang mOt yang dirt 13± rung !chi dutrng truyin gifts
BS vi MS kiting bj an frit Met rung pham vi bj giOi hp hien tai mitt WLAN
ding cung (hotspot) den phi= vi rung (hotzone). O nhttng dieu kien tot nil&
ce the dot (bye phgn vi phi sting 50 km v6i toe dO dit lieu bj ha thip (mOt
vii Mbit/s), pham vi phi sting dien hinhli gin 5 km v6i CPE (NLOS) trong

nhi vit gin 15km vii mOt CPE duet not vii mOt anten ben ngoii (LOS).
—
Dung lucmg cao: C6 the dot duce dung luqng 75 Mbit/s cho cac tram g6c yeti
mOt kenh 20 MHz trong cac dieu kien truyin song tot nhit.
—
Tinh mei rung: Chuin 802.16 -2004 M trq cac dii th8ng kenh dui s6 v8 tuyen
(RF) mem deo vi sfr dung loi the kenh tin s6 nay nhu la mOt each di tang
dung luqng martg. Chuin cftng djnh r8 h8 trq deli vai TPC (dieu khien c8ng
suit phit)
vh
cic phep do chit luqng kenh nhu the Gang cu them vtio de h8
trq sa dung ph6 hieu quit. Chuin dA dupe thiet Ice de 4t tt le len tai hang
tram th#m chi hang nghin nguOi sa dung trong mOt kenh RF. H8 trq nhieu
kenh cho Step cac nhb the to thiet bj cung cap mOt phuang tien de chi trcmg
vho phi= vi su dung ph6 vi nlang quy djnh cip phit duce mai r8 bid cac nhi
v#n hinh trong the thj truing quac to thay deli !chic nhau.
—
Bin mkft: Bing each ma hOa the lien kit v8 tuyin gifta BS vi MS, su dung
chuin ma hba tien tien AES, dim bao sv tan von ctia Ott lieu trao deli qua
giao dien v6 tuyen. Cung cip cho ac nha v#n Minh vii sv bito ve manh
cheng lai nhftng hAnh vi dinh cip djch vu.
Phan Tien Ting
MSV: A13162
Trang 4
TONG QUAN VE
H$
THONG WiMAX
1.2. Cic chuAn chit WiMAX
1.2.1. Chan IEEE 802.16-2001.
ChuAn IEEE 802.16-2001

duqc hoar) think vho thing 10/2001 vh duqc cemg 136
vho 4/2002, djnh nghia dac ti
k9
thu$t giao din kitting gian WirelessMANni cho Mc
ming vbng d8 thj.
Dac diem chinh Ma IEEE 802.16-2001:
+
Giao dies !thong gian cho he thing truy nh$p khong day bang rung
do
djnh
host dung 6 did tin 10 - 66 GHz, cAn th6a man tim thin thing.
+
Lip vat 15
,
PHY: WirelessMAN-SC.
+
T6c dO bit: 32 -134 Mbps yeti kenh 28 MHz.
+
Dieu chi QPSK, 16 QAM vi 64 QAM.
+
Cic dii thong kenh 20 MHz, 25 MHz, 28 MHz.
+
Ban icinh cell: 2 - 5 Ian.
+
Ket
n6i
c6 djnh hueng, MAC TDWIDMA, QoS, bin
mot.
1.2.2. Chan IEEE 802.16a.
Vi nhong kith khan trong then khai chuin IEEE 802.16, hueng vho vies sir dung

tin s6 tir 10 -
66 GHz, mOt dv in sou d6i c6 ten IEEE 802.16a da duqc holn thhnh vho
thing 11/2002 vh duqc c6ng b6 via thing 4/2003. Chuim nay
duqc
me rung h6 trq
giao dien kh8ng gian cho nhemg ten
s6
trong bang tin 2-11 GHz, bao
g6m
ci nhttng
phi cup phap vh khong cep phip vi khemg cin that man dieu ;den tim nhin thing.
Dac diem chinh curt IEEE 802.16a nhu sau:
+
B6 sung 802.16, cic hieu chinh MAC vi cic dac diem PHY them vho cho
2-11 GHz (NLOS).
+
Tic dO bit: teri 75Mbps yeti kenh 20 MHz.
+
Dieu chi OFDMA vOl 2048 sting mang, OFDM 256 sting mang, QPSK,
16 QAM, 64 QAM.
+
Dii thong kenh c6 the thay d6i gilts 1,25MHz vi 20MHz.
+
Ban lcinh cell: 6 - 9 lcm.
+
Lop vat PHY: WirelessMAN-OFDM, OFDMA, SCa.
+
Cic chile niing MAC them vtio: h6 trq PHY OFDM vi OFDMA, h8 trq
cemg nghe Mesh, ARQ.
Phan Tien Tang

MSV: A13162
Trang 5
TONG QUAN VE lit THONG WiMAX
1.2.3. Chula,: IEEE 802.16-2004.
Tilling 7/2004, chuim IEEE 802.16 - 2004 hay IEEE 802.16d dupe chip nh$n
thOng qua, ket hap cuts cac
chuk
IEEE 802.16 - 2001, IEEE 802.16a, ling dung LOS 6
did
tan s6
10- 66 GHz vi NLOS ti did 2- 11 GHz. Khii Ming v8
tuyen b6 sung
nhu lh
"beam forming" vi kenh con OFDM.
1.2.4. Chuin IEEE 802.16e.
Chan khong day bang thong rung 802.16e vai ten gqi Mobile WiMax cho phep
tram
g6c ket n6i
tai nhitng thiet bj dang di chuyin. Chum nay gap cho the thiet bj a
cac nhe sin xuit ray cti the lam viec, tutmg thich
t6t voi
cac thiet bj tfc ciic nha san
xuit khac. 802.16e hqat dung 6 cac bang tin nhe han 6 GHz,
t6c
dg len teri 15 Mbps
yen kenh 5 MHz, ban lcinh cell to 2 - 5 km.
WiMAX 802.16e c6 h6 trq handoff vi roaming. Su dung SOFDMA, mOt c8ng
nghe dieu the da song mang. Cac nhi cung cep dich vy tan khai 802.16e cling c6 the
su
dung Truing d6 cung cup dich vp

c6
djnh. 802.16e h6 trq cho SOFDMA cho phip
s6
song mang thay d6i, ngoii the m8 hinh OFDM vi OFDMA. Sr phAn chia sting mang
trong m8 hinh OFDMA dirge thiet ke d6
t6i
thieu inh Wing cua nhigu phis thiet bj
ngutti dOng yeti anten da hueng. Cu the han, 802.16e dim ra h6 trq cii den h6 trq
MIMO vi AAS, cling nhu cit handoff cimg vi mem. NO cling cii
tien
cac khi nAng
tilt kiem
c8ng suit cho cfic thiet bj di dung vi cic dac diem bao mot linh hoot han.
Phan Tien Tang
MSV: A13162
Trang 6
TONG QUAN 'VE HE THONG WiMAX
DM tin
s6
10-66GHz <11GHz <6GHz
M6i truang truyen
Line of Sight (LOS)
Non Line of Sight
(NLOS)
NLOS
T6c dO
32-144Mbps
Up to 70 Mbps
10M - 30M
Dieu the

Dieu the dun sOng
Mang QPSK
OFDM 256 sOng
mang con QPSK,
16 QAM, 64QAM
S-OFDMA QPSK,
16 QAM, 64 QAM
Mirc di ding
C6 dinh
c6
dinh CO the cho
the
dO di
chuyen thip
Bang th6ng kenh
20,25,28MHz
5- trtn 20MHz 1.25-20 MHz
Bin Icinh cell
1.7-5km
5 tai 10Ian;
toi
da
50 km thy thuOc
vao
dieu kien
truyen
1.7-5km
Bang 1.1 So seinh cac chain IEEE 802.16
Voi nhftng dtic diem va su phat den cult cac chuin IEEE802.16 n6i tree, to co the
'than thiy dtrqc sulchic nhau ca ban cang nhu firth ke thira caa cic chuin nay.

IEEE yin dang nghien cuv va dui ra cac chuin 802.16 mai nhim hoen thien
chuin nay. Vi du nhu: IEEE 802.16f-2005, IF.F.E802.16g-2007 b6 sung cho thu tyc
quitn
lfr
ke hooch vtl djch Ai, IEEE 802.16k-2007; IFFY. 802.16-2009 cling c6 tieu
chart IEEE 802,16-2.004, 802.16e-2005 vi 802.16-2004/Cor1-2005, 802.16f-2005,
vi 802.16g-2007, 802.16m
1.3. Phi WiMAX.
WiMAX - thiet bi mem deo se dtrqc phep hoot ding tong ca hai dai duct ding
Icfr va kh8ng ducm ding Icfr.
1.3.1. Bang
tin
piing kj
Cfic giai phap clang
k9
cung cep cac tru diem chit lucmg djch vu duct chi thien
cao han cac giai phitp !thong clang k9, chip nh$n NLOS tot han a cac tin s6 thip, ne
co mOt nein quy deg suit dutmg xu6ng ring han va co the h6 trq cac anten trong nhtl
t6t han. Giai phip (tang kfr cho phep kiem so& qua cach sir dung ph6 vil Watt.
Phan Tien Tang
MSV: A13162
Trang 7
TONG QUAN VE He THONG WiMAX
a Bins
tin
1111nz $ 2.5 GHz
DA dirge dip ph& trong phin 16u the gi6i, bao
gem
bile
M9, my

Latin, D8ng vu
Tay
Au va nhieu ming caa
chau
A -
Thai Binh Duang nhu mOt bang tin dang 1c9.
MOi
qu6c
gia thubng cep phit dal khic nhau, vi v$y ph6 dupe cup phit qua cac vang c6 the
tfr 2,495 GHz den 2,690 GHz. Tong ph6 kha dung 18 195 MHz, bao
gtom
cac did pheng
ye Nal cac kenh MDS, gba 2.495 GHz va 2.690 GHz. HO trq FDD, TDD. Ph6 tren
tnoi
dling k9 la 22.5 MHz, mOt block 16.5 MHz vtl mOt block 6 MHz,
tong s6
8 clang 1E9.
b. Bins
tin
an Id 3.5 GHz.
Chau Au, vien chuin vier th8ng Chau
Au
dA plan ph6i dal 3,5 GHz, bit diu
dirge sir dung cho WPLL, cho cac gi8i phap WiMAX clang ky. T6ng ph6 khi dung
thay 461 then
qu6c
gia nhung ned chung khoing 200MHz gifts 3,4 GHz vi 3,8 GHz.
HO trq FDD, TDD. MOt vii
qu6c
gia chi sfr dung FDD trong khi cac

qu6c
gia khic cho
s* dung FDD hokIc TDD. Ph6 ben
m61
slang Icy thay d6i ta. 2x5MHz den 2x56 MHz.
1.3.2. Bing
tin
khOng ding
45
56Hz
Phan
16n cac qu6c gia tom the gi6i dA stl dung ph6 5 GHz cho Mc bang ding
kheng long k9 nhu: Wing 5,15 GHz va 5,85 GHz
Cac giiti phap kitting dling 1c9 cung cep mOt vii thu$n lqi chinh ham cac gi8i phap
Clang k9, bao
Om
chi phi ban dL thip han, rut m nhanh han, vi mOt bang chung c6
the dirge su dung 6 phin 16n the gi6i. Cac ici kb My dang thu but sir quan tam v8 c6
khi Ming cho sir chip nhen bang rung nhanh ch6ng.
Tuy nhien mOt giai phap kh8ng clang 1c9 thi khi nAng nhiL cao han, va nhieu sv
canh tranh desi tied Mc nha kinh doanh bit dung sin cho viec trim khai. MOt gi8i phip
kitting clang k9 se khang duqc xem nhu mOt sv thay the cho giai phip dang ky. MOi
giai phip cung cep mOt thi twang khic nhau dva vio str thoa hiep gifts chi phi vi QoS.
1.3.3. Cdc being
tin thtyc ii xuit
cho WIMAX win thi
gtdrt
Cac bang
tan
dirge Diln dart WiMax trong xem xdt va v$n dung ca quan quip

19
tan so
cac nu6c phan b6 cho WiMax la:
—
Bang tin 2,3-2,4GHz (2,3GHz Band): dirge de St sti
.
dung cho Mobile
WiMAX. Tai Han Qu6c bang My dit dirge trien khai cho WBA (WiBro).
—
Bang tin 2,4-2,4835GHz: duqc de xuit sfr dung cho WiMAX trong Wang lai.
—
Bang tin 2,5-2,69GHz (2,5GHz Band):
duct
de St sir dung cho WiMAX di
dOng trong giai don diu.
—
Bang tin 3,3-3,4GHz (3,3GHz Band): dirge de xuit s6r Mpg cho
WiMAX c6
djnh.
Phan Tien Tang
MSV: A13162
Trang 8
TONG QUAN VE He THONG WiMAX
—
Bang ten 3,4-3,6GHz (3,5GHz Band): &roc de
xuit sfr dung
cho WiMAX
c6
djnh
trong giai

door du:
FWA (Fixed Wireless Access)/WBA (WideBand Access).
—
Bang ten 3,6-3,8GHz: dirge de 'cult so. dung cho WiMAX
c6
djnh (WBA) vil
cap cho Chau
Au.
Tuy nhien, bang 3,7-3,8 GHz dit dirge dung cho ve tinh vigil
tilting Chau
A, nen
bang ten My khong dirge st• dung cho Wimax Chau
A.
—
Bang tin 5,725-5,850GHz: dirge
di xuat
s* dung cho WiMAX
c6
djnh trong
giai clop
du.
—
Ngoli ra, mOt
s6 bang tin Ichic phitn b6 cho BWA cOng dirge
mOt so nuoc
xem
xat cho BWA/WiMax la: bang tin 700-800MHz (< 1GHz), bang 4,9-5,1GHz.
1.3.4. Cdc bang hiss it Viet Nam cd khd niing dank cho WiMAX
—
Bang tin 2,3-2,4GHz: C6 the danh (loon bang tin My cho WiMAX. Bang tin

2,3-2,4GHz thich hop cho ca WiMAX c6 djnh va di (tong.
—
Bang tan 2,5-2,69011z: Bang tin My hien nay dang dirge s* dung nhieu cho
vi ba vi MMDS Nip thing chti
yeu
6 Hi nOi wit thinh ph6 H6 Chi Minh)
Ngotti ra, bang tan nay II mOt trong cac bang
tan duce
de )(at su dung cho
3a
Bang tin nay loi li bang tan dirge dank gia la thich hop nit& cho WiMAX
di ding va da
duce
Dign din WiMAX )(sic nhen chinh thtic 11 bang tin
WiMAX. MOt s6 nuke cOng d1 danh bang tin nay cho WiMAX nhu
My,
Mehice, Brazil, Canada, Singapo. VI v$y,
de
nghj danh bang tin 2,5-2,69GHz
cho WiMAX.
—
Bang tan 3,3-3,4GHz: Theo Qui hooch ph6 tin
s6
VTD
qu6c
gia, bang tin
nay duce Olin b6 cho the nghiep At Ves
tuyen
djnh vi, c6 djnh ve
ltru ding.

Ve phis clan sir va quilt' su veil chua co he thong Mc, duqc
trien
khai tong
bang
tin my.
Do do, c6 the cho phep s* dung WiMAX trong bang
ten
3,3 -
3,4GHz.
—
BAng tin 3,4-3,6GHz, 3,6-3,8GHz: D6i v6i Viet Nam, he thong
4
tinh
VINASAT su dung mOt
s6
doon bang tan trong bang C va Ku, trong d6 cal
bang
ten
3,4-3,7 GHz. Ngohi ra, (loon bang tan 3,7-3,8 GHz m#c de chua su
dung cho VINASAT nhung c6 the dupe s* dung cho cac from mit dat lien loc
v6i the
he
thong ve tinh !chic. VI v$y kheong
nen tan
khai WiMAX trong
bang tin 3,4-3,8 GHz.
—
Bang tan 5,725-5,850GHz: Hien nay, bang tin My da dupe BO qui djnh dart
cho WiFi. Neu cho phdp tan khai WiMAX trong bang tan My thi cOng se
hp 64 bang

tin dinh
cho WiFi. Bang tin nay c6 the thich hop cho the he
Phan Tien 'fling
MSV: A13162
Trang 9
TONG QUAN VE He THONG 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 thanh then Mug he
thong WiMAX. VI voy, de nghj cho phep trier khai WiMAX trong bang tin
5,725-5,850GHz nhung WiMAX phiti clang chung bang tin vi phai bao ve
cic he th6ng WiFi.
Nhu vtly, vbi hien tang sil dvng bang tin tai Viet Nam nhu tren, cac bang tin c6
Icha Wing dinh cho WiMAX et Viet Nam la:
—
Bang tin 2,3-2,4GHz vi 3,3-3,4GHz cho cic he thong truy c(ip kh8ng day
bang rung, kg ea WiMAX.
—
Bang tin 5,725-5,850GHz cho cast he thOng truy cop kh8ng day bang rung, ke ca
WiMAX nhung cic he th6ng nay phii clang chung bang tin yeti cic h>i thong
WiFi vOi dieu kien bao ve
ctic
he thong WiFi hog dOng trong bang tin nay.
—
Bang tin 2,5-2,690GHz cho cic he thong truy cop !thong day bang rung, kg
ca IMT-2000 va WiMAX.
Chlnh phi da cep phep thu nghiem djch vp WiMAX di dOng tai bang tin 2,3-2,4
GHz vii bang tin 2,5-2,69 GHz. (Theo deg van s6 55351VPCP-CN dm Van phemg
Chinh phi).
1.4. Truyin song.

Trong khi !lieu ding nghe hien dang tan tai cho !thong day bang rung chi c6 the
cung cep phi sang
LOS,
Gang nghe WiMAX ducrc toSi uu de cung cep phi sang
NLOS.
CEng nghe den den ctia WiMAX cung cap tat nhit cho ca hai. Ca LOS vi
NLOS bj anh huong bei cic d#c tfnh dirbng truyen m8i tru&ng cis chimg, ten thit
dutmg don, vi ngan guy' kit nhi v8 tuyen.
Trong lien lac LOS, mOt tin hieu di qua mOt dirtmg Ulm tiep vi Ichong N tic
nghen tir may phit din may thu. MOt lien lac LOS yeu cau phin Ion mien Fresnel this
nhAt thi kh8ng bj nein cim cis bit Id vet can nao, neu lieu chain nay ;thong thda man
thi c6 sir thu nh6 ding ke cubng dO tin hien quan sit. DO
her
Fresnel duct yeu ciu phu
thuOc vao tin s6 hoM Ong vi Ichoing each gifts vi tri miy phit vi may thu.
Trong lien lac NLOS, tin hieu den miy thu qua phin xa, tin xa, nhigu xa. Cic tin
hieu den may thu bao gam cac thanh phin hY dubng tnrc dip, cic dutmg duqc phim xp
nhieu lin, Wing luqng bj tin xa vi cic thrtmg truyen bj nhigu xa. Cic tin hieu nay c6
Idioang trg khic nhau, suy hao, phan cvc vii dO on djnh quan hu vbi dubng truyen trim
dip la nguyen nhan gay ra nhigu ISI vi mio tin hieu. Dieu d6 !thong phai la van
de
deli
ved LOS, nhung yeti NLOS thi Iai la van de chinh.
Phan Tian Tang
MSV: A13162
Trang 10
TONG QUAN VE HE THONG WiMAX
C6 nhieu tru diem ma nhttng trier khai NLOS too ra ding khao !chit. VI du, S
yeu cau 1#p ke hooch chat
the va

giai Igut chiIu cao anten ma t
h
rong lcheong cho phdp
anten duqc be trf cho LOS. Vai nhOng
Wen khai
ti bao ke nhau phom vi rung, nai tin
s6
duce saf dtmg loi la tai hp, ha thip anten la thufm lqi de giim nhieu kenh chung
girra tic vj trf cell lien ke. Dieu nay thuang c6 tic dung fink day cic
torn etc hoot
dung trong cic dieu lden NLOS. Cie he thong LOS khong the giam chi& cao anten
bai
vi lam nhu vay se c6 tic dOng den throng quan sit
Ulm tikp
duqc
yeu au tfr
CPE
den
tram geoc.
Hinh 1.2 Minh hpa heat dong WiMAX.
CEng nghe NLOS cfing giam phi
ton cli
at
bang cich d#t dm% cic mai the that
bi CPE dimg nhu nguyen bin vl giant bat kh6 khan dinh vj tri cic dia diem
at
CPE
thich hqp. CEng nghe cang giam bat nhu ciu quan sit vj tri thiet bj phis truck vl
cli
thien dt) chlnh xic ca a cic c8ng cu lop kg hooch NLOS.

CEng nghe NLOS vl nhttng firth ning
dupe Hang
cao trong WiMAX to kha
nal% a* dung Net
bj phis dau khich hang (CPE) trong nhl.
1.4.1. Dien chi thich nghi.
Dieu
chi thich nghi cho phop he th6ng WiMAX dieu chinh so de diet' the tin
hieu phu thuOc Arlo diau kien SNR cart lien kit v8 tuyen. Khi lien ket vo thy& chit
luqng cao, so de diets chi cao nhit
duqc
sfr dung, dua ra
he
thong dung luvng lan hon.
BPSK
SNR = 6dB, lbit/Hz
QPSK
SNR = 9dB, 2bit/Hz
16QAM
SNR = 16 dB, 4 bit/Hz
64QAM
SNR = 22dB, 6 bit/Hz
Binh 1.3 B6n kinh cell quan hg vol dau chi thich nghi.
Phan Tien Tang
MSV: A13162
Trang 11
TONG QUAN VE He THONG WiMAX
Trong qua trinh suy gilun tin hieu, he thong WiMAX c6 the djch den mOt sa d6
dieu the thip han
de

duy tri chit lumg kot
not
vi On djnh lien ket. Dac diem nay cho
phep he thong !chic phuc fading Iva chqn than gian.
1.4.2. Cling nghe spa 111.
Cac c8ng nghe sat
161
di duqc hop nhit trong WiMAX de giant cac yeu ciu ti
so
tin hieu ten tap am he thong. Cac thuit Min FEC, ma has xoin vi chen
duqc
clang de
phit hien vi sera cac lei cii thien thong lucmg. Cac deg nghe suit
161
manh gulp khOi
phuc cac khung bj lei ma c6 the bj mit do fading Iva chon tin
so vi the lei
cum. Tv
dung yeu ciu lap 1gi (ARQ) duce clang de sou lei mi Wong the duqc sou b61 FEC, gal
lei
thong tin bj 161. Dieu nay c6 y nghia citi thien chit ltrqng
tex de, 16i
bit (BER) dei
vii met mirc nguang nhu nhau.
1.4.3. Dilu khan c8ng suit.
Cic tit*
toast dieu khien ding suit duqc dung do citi thief' chit luqng toan be he
thong, no duqc thvc hien btri tram
gic
gni thong tin dieu ;chi& ding

suit den
mei CPE
de dieu chinh mtic c8ng
suit truyin
sao cho mire da Shen 6 train
gic
Oil 6 met mirc da
xic djnh three. Trong mei twang fading thay doi gong, mirc chi lieu da djnh truac nay
c6 nghTa 11 CPE chi tuyen da ding
suit
they man yeu ciu ay. Dieu khien deg suit
gilun sv tieu thu Gong suit
tong
the cue CPE vi nhieu vii !tilting
tram gee cling
vi frt.
V6i LOS, c8ng
suit truyin
cos CPE gin timing ling vii khoang ctich mitt n6 den tram
g6c,
vii NLOS, thy thuec nhieu vio dO ha vi vet can.
1.4.4. Clic c8ng ngke
v8
tuyin den din.
a.
Ph& On thu
va
vhdt.
Cic hrcrc
de phan top duqc sir dung de lqi dung the tin hieu da duOng vi phitn

xey ra trong cite mei twang NLOS. Bing citch sir dung /fink Aug ten (truyen va/hoac
nhon), fading, nhieu vi ten hao throng truyin c6 the duqc Mm giant. Phan tap truyin
sir dyng ma thin gian khung gian STC. Doi vii phan tap nhan, cac citing nghe nhu kit
hqp tjr le
t6i
da (MRC) mang 13i uu diem caa hai dtrimg thu rieng Wet. Vi MISO (met
diu ra
nhieu diu
vio) xem Error! Reference source not found.4.
HIM 1.4 MISO.
Phan Tien Tang
MSV: A13162
Trang 12
TONG QUAN VE He THONG WiMAX
M6 rung ten MIMO (xem Error! Reference source not found.5), sir clang
MIMO cling se ning cao th8ng lucmg vl tang Mc throng tin hieu. MIMO sti clang
Wilk Ang ten thu vi/hoic phat cho ghep kenh theo kh8ng gian. M61 Ang ten ce the
truyen dtr lieu khac nhau ma sau de c6 the &roc gill ma 6 may thu. Did v6i OFDMA,
bed vi mai s6ng mang con la cac kenh bang hap Wong to, fading
Iva
chip tin s6 xuit
hien nhu ll fading phing toi m6i s6ng mang. Hieu (mg nay ce the sau d6 duqc m6
hlnh hOa nhuli mOt so khuech dpi thong d6i phtic hop vi c6 the don gian hes so thoc
hien ctia met may thu MIMO cho OFDMA.
HIM 1.5 MIMO.
b.
Cdc he thane ant ten notch nig
AAS la met phi!' try chip. Cie tram g6c c6 trung bj AAS c6 the tao ra cac chum
ml c6 the duqc Ili, tip trung Wing lucmg truyen de dat
duqc

pham vi lon hon. Khi
nhin, cluing c6 the tip trung 6 liming co the mitt may thu. Dieu nay gulp cho loci be
nhiiu kh8ng mong mu& tt cite vi tri khlc.
1.5. So slab WIMAX v6i WIFI vi 3G
Hien nay 6 Viet Nam cluing ta, WiFi vl 3G dang ll hai ding nghe kit nil kh8ng
day phlt trien nhit nen ta c6 the so sanh chimg veri WiMAX.
1.5.1. WiFi
WiFi - Wireless Fidelity la ten pi ml cite nhl san mit
at
cho mat chuin kit n6i
khOng day(IFFE 802.11), cang nghe set dyng s6ng radio de thiet lip he thing kit n6i
mang kh8ng day. Day 11 deg nghe mang throe thuang mai h6a tien tier nhit hien nay.
WiFi vl WiMAX c6 cling mat nguyen hoot Ong 11 truy cep mpg qua tin hieu
v8 tuyEn.
Kit
nig WiFi nhanh nhit c6 the nu* duqc UM 54 Mbps trong cac dieu kien
t6i uu. WiMAX c6 the filly& len tell 70 Mbps, them chi khi bj chia tich gifta vai choc
ding ty vl hang tram hO gia dinh ngubi dOng thi it Whit n6 se cung cip t6c dO tuang
duang v6i t6c dO truyen con modem cap cho m61 ngubi dUng. Nhtmg so Iduic nhau 16n
Whit
gitra WiMAX vi WiFi khOng phii la tic dO truyin ma la ban lcinh phti song. WiFi
Phan Tien Ting
MSV: A13162
Trang 13
TONG QUAN VE 1-1B THONG WiMAX
c6 ban lcinh phu sling khan 30m con v6i WiMAX thl rung hen nhieu khoitng 50Km.
Co ly tang la do
tin so
duqc stl dtmg vi cOng suit ctia may phat.
Tuy vay, WiMAX

duqc
thiet ke khOng phiti de mau than voi WiFi ma de
Gang
tin tai voi
WiFi. VOng plmi sang cua WiMAX duqc do theo 1Cm
2
, trong khi yang pho
song cua WiFi
duqc
do theo m
2
. Chuin WIMAX
gee
(IF.FE 802.16) de xuit vier su
chmg phi tin 10-66 GHz cho
truyin din WIMAX,
ma cao hen nhieu co ly WiFi (len
tel tei
da 5GHz). Nhung 802.16a da h6 trq them cho
tin sto
2-11 GHz. MOt tram glic
WIMAX co the
duqc
truy cap btri han 60 ngatri su dung. WIMAX ding c6 the cung
cap
cac djch vu gang ba.
Cac dile diem Id thuat WIMAX cOng cung cap the dieu kien thu$n lqi
tot
han
nhieu so voi WiFi, cung cap dO rung bang tin cao han vi an ninh dit lieu cao bang

cach sir dung cac ke hooch mil hOa tang cueng. WIMAX cling co the cung cap djch vu
theo ca hal dja diem LOS va NLOS, nhung co ly se thay doi cho phu hqp.
WIMAX cho phep them nhap vac) dich vu bang ring Vol?, video, Ara truy cap
internet ding thtri. Ctic anten WIMAX c6 the "chia se" mOt thap cell ma khOng can
den
xep
chirc niing cult the
mang t6
ong dit ditch hqp.
1.5.2. 3G
a.
Etats:
La
the he
thong tin di dung
se
cho phep chuyen rating bit kk, c6 kha rang truyin
thong da phuang fien chit Wong cao.
Cfic
he
thong 3G duqc xay dung tren ca sa CDMA hoitc CDMA kit hqp
voi
TDMA, co ldui !tang cung cap mOt bang tin rung theo yeu ciu, do de c6 the trq cac
djch vu co
nhieu the
dO lchfic nhau. O
the he thir 3, the he thong thong tin di dung c6
xu the hoti nhap filth mOt fieu chuin chung duy shit va phuc vu len den 2Mbps. M#c
dh 3G duqc firth tam se la mOt chuin mang tinh town
ciu

nhung chi phi thy dung ca
so Ito tang cho he thong nay
rat ton
kern.
b.
So stink WIMAX di &Ina viti 36.
WCDMA duqc phitt trien de tang lchi niing dubng
xuting
voi phien bim truy nhlip
goi throng
xueng t6c du
cao (HSDPA) va truy nh#p gel dubng len
tec
dO cao HSUPA.
Nhom phat trier 3G cOng can nhic phat hien khi niing truyen xa han cho WCDMA
nhu la cung cap MEMO vOi HSPA.
Tuang to nhu stay, CDMA 2000 ducat ph& train de tang Ichit rang truyen din
se
lieu
tai phi& ban lx EVDO-Rev 0 Ara lx EVDO-Rev A. MOt clang cao nits la phi&
ban EVDO Rev B Qua vtio khit niing da song mang.
Phan Tien Tang
MSV: A13162
Trang 14
Tieu chuin ca sec
CDMA2000/IS-
95
WCDMA

IEEE802.16e

FDD

FDD

TDD

TDM

CDM-TDM

OFDMA

CDMA

CDMA

1,25 MHz

50 MHz
5; 7; 8,75; 10 MHz

MA h6a

Turbo

CC Turbo

CC, Turbo

TOc du dinh DL

3,1 Mbps

14 Mbps
46 Mbps,
DL/UL=3
32 Mbps,
DL/UL=1

TOc du dinh UL

1,8 Mbps

5,8 Mbps

7 Mbps, DL/UL=1
4 Mb s s, DL/UL=3

H-ARQ


D c ng b0 4 kenh
nhanh IR

D i ng be
e
• 6 kenh
nhanh

CC

D ng b0 da kenh
CC

Lap
ljch


L$p ljch nhanh
DL

L$p ljch nhanh
UL
L$p ljch nhanh DL
va UL

Chuyen yang (Handoff)

Chuyin vtIng
mem Ito

Ch. yang cling khoi
tau mang


Kich cif khung
DL

1 67 ms

2 ms

5 ms TDD
UL

667 ms
2/ 10 ms


Dieu chi DL
QPSK/ 8PSK/
16 AM
QPSK/ 16QAM
QPSK/ 16QAM/ 64
AM
Dieu the UL
BPSK, QPSK/
8PSK
BPSK/

QPSK/ 16 QAM

TONG QUAN VE
He
THONG WiMAX
Do 1xEVDO va HSDPA/HSPA dupe phit then ter tieu chitin CDMA
3G
de cung
cep djch vp
s6

lieu thong qua mang ban diu duce thiet ke cho djch vu thoai di dung do
d6 no thus huOng ca nhftng uu diem va ca nhOng han the cult he thong 3G. WiMAX
ban
du
dirge phit then cho truy nh$p v6 tuyin bang rang
co
djnh va ne dirge
ten
tru
cho truyen
s6 lieu.
WiMAX di dung throe phit trien tren ca so cis WiMAX
co
djnh va
duce diet' chinh
a
phi\ hap cho yeu cau di dOng. Viec so sinh gifta cic thuac tinh cis
WiMAX di dung vOi 3G tren ca so he thong lx EVDO va HSDPA/HDPA se cho to
they r5 cong nghe nao se dip Ong throe cic did hai cis mang djch vu
s6
lieu bang rang
di dung. Cac thuOc tfnh cu the dirge dua ra trong bang 1.2.
Bang 1.2 So sdnh Ws:MAX di Ong vie 3G.
Phan Tien Tang
MSV: A13162
Trang 15
TONG QUAN VE He THONG WiMAX
1.6. Kit luen chuvng.
Qua tim hieu nhDng phan trinh btly 6 tren glop to ce mOt cal !thin
ten quan ye

deg nghe Wimax, so sixth veri cac yang nghe 'thong day lchic, dua ra uu, nhuqc diem,
Idia Ming (mg dung va filth hInh trim lchai caa n6 trong thqc 4. Tu d6 di bit
diu
di du
han, tim hieu
ye
bin true mang truy cep WiMAX se duqc tr1nh bay 6 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
2.1.1. Sir dnh Mang cia nail truing din Wee tn(yIn den
Thir !that to phii khing djnh ring mai trueng truyin thong v8
tuyen 16 mOt
m6i
throng khic nghiet nhit trong
truyen
din th8ng tin. N6 gay suy hao tin hieu ve bien dO
cOng nhu suy hao lira chon tin
s6 kern
theo cgc hieu ting fading da throng.
Sr suy hao tin hieu tang nhanh theo khoitng each vi 6
tin s6
cao, ngotli ra ser suy
hao ding phv thuOc vtlo dia hlnh (khu vvc n8ng th8n, thinh thj, ding bing hay mien
Hinh ve duck dAy mink hoa sty suy gum tin hieu theo khoing each vi tren cac

loci dja hlnh veri cac dieu kien truyen din Ithic nhau ctia hai he thing ISM
tin s6
2,4
GHz vi UNII tin s6 5,4 GHz.
Hinh 2.1 Suy gitim tin
hieu
theo khodng catch.
Ngoli ra trong m8i truong truyen din da duong, nhieu xuyen
ky ter
(ISI) gay Uri
tin hieu phin xa ce thee gian tre !chic nhau th cdc hueng lchic nhau ter nai phat teri nal
thu 11 dieu Wing the tranh khOi. Anh holing nay co the ibm bien ding tin hieu lchien
ben thu kh8ng the kh8i phvc dtrqc tin hieu.
2.1.2. Da song mang (Multicarrier)
Neu
truyen tin hieu khong phii bang mOt song mang and bing nhieu sang mang,
m& song mang tai mOt phin &Et lieu c6 ich
vi duqc
triti deu tren cit bang thong thl khi
chju Anh
hutmg
Au se chi c6 mOt phin dft lieu cat ich bj mkt, dva tren co set der lieu
ctla cac sting mang khac c6 the khei phvc lai de lieu c6 ich.
Phan Tien TAng
MSV: A13162
Trang 17
CAC KT THUAT SU DUNG TRONG WiMAX
Binh 2.2 Sy tgo ra tin hieu OFDM
Do vey, khi ding nhieu song mang c6 tdc dO bit thep, nhieu clit lieu g6c sE duqc
thu chinh xic. Di hei phuc der lieu di mit, ngubi to ding phuong phip sfra lgi FEC-

Forward Error Correction. t3 may thu m6i song mang duqc tech ra khi ding cic b0 loc
th8ng thubng vtl gill dieu chi. Tuy nhien di kh8ng c6 can nhigu gills cic sting mang
(ICI) can phii co khoing ha° ye khi hieu qui 06 kern.
11•1•411.1
A A
HIM : PDM
thong etas
vi CIPDM
Binh 2.3 FDM thong finding va OFDM
Gill phip lchic phuc viec hieu qui ph6 kern khi ce lchoing bio ve (GUARD
PERIOD) la giant khoing cich cic song mang vi cho phep ph8 cis cic song mang canh
nhau trUng nhau. Su Ding lep nay 11 duvc phep nen khoing cach Watt cic sting
mang dtroc chcm chinh xic. Khoing cich nay thrqc chon ung vai trubng hop cic sting
mang true giao vOi nhau. DO 111 phuang phip ghep kenh theo tin so tnrc giao (OFDM).
Cho tel nay dull tren nhttng thanh tuu cis c8ng nghe mach deb hop phuong phip
nay dit duce thuc hien met cich d8 clang.
Phan Tien Tang
MSV: A13162
Trang 18
CAC KT THUAT Sfi DUNG TRONG WiMAX
2.1.3. Cling nghe OFDM v61 lad ndng hon chi nhilu
WIMAX se dung c8ng nghe OFDM de Irwin du lieu 6 giao dien vo tuyin va
cho ph6p the thug bao troy nh$p kenh. Cling c6 nhieu deg nghe ;chic
6
giao Bien nay
nhu FDM, CDMA. Tuy nhien OFDM da chting to n6 co nhftng uu diem han rat nhiiu
va t6c dO truyen, tS
,
le 16i bit, ding nhu hieu qua se dung ph6 tin nen de duqc IFPF.
chqn lam Ong nghe truyin din cho truyen din vet tuyen bang rung trong chain

IEEE.802.16.
Cac ki thu#t se dung trii ph6 true tiep DS-CDMA nhu trong chain 802.11b rat
d6 bi inh hu?mg Uri nhilu da dueing vi thbi gian tr6 c6 the vuqt qua kholing thtri gian
ctia mOt Id tu. OFDM se dung ki thult truyen song song 'Neu bang tin con nen kdo
did th6i gian truyen ld to len nhiiu lin. Ngoli ra OFDM can chen them mOt khan
bao ve GI (Gaurd Interval) thu&ng 16n han tit gian tri t6i da cart kenh truyin gills 2
Id AT nen nit& ISI c6 the
duqc
loai bo hoan twin.
Tren kenh truyen din MI Mau lea chqn tin s6 cling le mOt van de anh Ming len
den chit luqng truyen thong tin hieu. Tuy v$y OFDM ceng rat mem deo va linh hoot
khi giiti guy& yin de nay. OFDM as the khed phut lei kenh truyen thong qua tfn hieu
din duang (Pilot) duqc truyin di cling yeti clang tin hieu th8ng tin. Ngoli ra yeti cite
kenh con suy gilun nghiem treing ye tin s6 thl OFDM can cob mOt Iva chip nett de
giam tSr 1016i bit la gam bat s6 bit ma h6a cho mOt tin hieu dieu the tai
kenh
tin so d6.
Binh 2.4 So sdnh song mang mkt OFDM vol ctic hinh that
truyin thing.
1-11nh teen so sanh gifts hai hinh thee dilu che. D6i yeti clic hinh thin truyin
thong, mOt song mang dan veri bang th8ng rung se duqc truyen di, trong khi v6i
OFDM bang thong rung nay duqc chia that:1h cac bang con, mil bang con se img vol
Phan Tien T(Ing
MSV: A13162
Trang 19
CAC Id THUAT SO
.
DUNG TRONG WiMAX
mOt sing mang con, cic sing mang con trvc giao nhau. Viec chia bang con niy se litm
t6c

dO
tren mai
bang con nay gitim di N lin, tuy nhien, chu Id cis mOt sang mang cling
se dii hon N lin. Dieu niy giop cho viec ding b0
a
ding
hon, trinh nhigu da dubng
cling tot
hon. Viec chia th8ng tin cang glop cho viec chong nhigu
tat
han, vi niu
bj
nhigu, Ong chi bj nhigu ten cite cum don le, nen ce the khic phuc
a
ding han.
Mai sting mang duqc gain
luting
dit lieu de
truyin
di. Bien dO via pha cos sing
mang duqc tinh toan dva tren phuang thin dieu the (thubng li QPSK, BPSK, QAM).
Sau d6 ding bien doi IFFT (Inverse Fast Fourier Tranform) di bign tir mien tin
s6
ve
mien thtri gian. IFFT li mOt phucmg phip toles dhi hieu qui vi dim bio cho cic sing
mang con trvc giao. Tai b0 nhan, nortri to ding Bien doi FFT(Fast Fourier Tranform)
de bien d6i nguqc 13i tir mien thbi gian sang mien
tan so.
MOt van
de

quan tong trong
truyen
din li sv dbi hei !chit khe ve sv (long b0 vi
sv sai lech vi tin
s6,
Anti hulk% cult hieu (mg Doppler khi di chuyen vi lech pha se
gay ra nhigu giao thoa
tin so ICI
(Intercarrier Interfrence) mi hau qui la phi be sv
trvc giao gifts cic
tin so
sting mang vi lam tang anh huing tai he tilting cling nhu
BER. Tuy nhien OFDM cling c6 the giim bat sv phtic tap colt
van
de ding b0 thong
qua khoing bio ve GI. Viec su dung chu8i GI cho phep OFDM co the diet' chinh tin
s6
thich hop mac di viec them GI cling ding nghia vai viec gian hieu qui so dung
bang tin.
Binh 2.5 OFDM phtit va thu
BO Serial to Para djnh d?ng luting der lieu, nhim cic bit l.i de gain cho cic sing
mang (VI du se Whim 6 bit mOt nhim lieu li QAM64).
Phan Tien Tang
MSV: A13162
Trang 20
CAC KY THUAT SIT DUNG TRONG WiMAX
OFDM hi mOt ding nghe chia TIM bang tan thlnh de bang nhe hon.Trong WIMAX
then chuan 802.16d, dit ap dung ding nghe ntly. VI v(ty WIMAX fixed c6 the host dOng
duqc trong m8i twang NLOS (Non Light of Sight). Trong WIMAX fixed dirge chia
dui& 256 sang mang con, 19811 danh cho de lieu, con lai dinh cho Hwang &to ve.

2.1.4. Teo va thu OFDM

Tin hi./ OFDM
bong g6c
(basebend)
D/A
oduad
OFSICOAM—etc
LEFT





TRANSMITTER

DIEU Olt
QS

Tin Mtn OFDM
bang g6c
FFT
RECEIVER
Hinh 2.6 Su lid kai can thiit bi delu culla
Phin may phat bien dui dtt lieu
s6 din
truyen, Anti vbo bien clO vb pha cult ck
tai
phu. Sau d6 n6 bien d6i bieu dien ph6 cua dtt lieu vbo trong
mien thoi gian nha sfr

dung hien d6i fourier ran rac deo (inverse Discrecte Fourier Transform). Bien al
nhanh Fourier deo (Inverse Fast fourier Transform) thud hien cUng mOt thirst tofin Whir
IDTF, ngoai trfr ring n6 tlnh hieu qua hon nhieu vb do vay n6 dirge sir dung trong
tit
eft cite he thong thud
te.
De truyin tin hieu OFDM tin hieu mien thei gian doge tinh
toan phlich
len tin s6
an thiet. May thu thirc hien thirst tom nguqc lai vii may phat.
Khi djch tin hieu RF
xu6ng
bang ca se de xi 1St, sau de sir dung bien d6i Fourier
nhanh de phan tich tin hieu tong mien tin s6. Sau de bien 40 vi pha cult et di phu
dirge chip ra vb doge bien d6i ngugc lai thanh dit lieu
so.
2.1.5. Clic se
di
min chi
Dtt lieu s6 dirge truyen tong kit nisi OFDM bang each dung so d6 dieu chi ten
mai tai phu. Sa d6 dieu the lb sir Anti xu the clii lieu vbo chum sao thgc (d6ng pha)
vb
phfrc (vuong pha),
duqc
biet nhu chum sao IQ (inphase Quadrature). SO bit c6 the
doge truyin khi dung mOt symbol tuong fmg vii log2(M) vii M lb
s6 the diem
trong
chom sao. M6i to clit lieu dirge dnh n vbo mOt vi tri IQ duy Whit tong chom sao.
Vecta phfrc hqp thanh I +jQ Wang fmg vii hien dO

4/
2

vb pha argument (I+ jQ)
Vic tang s6 diem tong chum sao khong thay d6i dai thong truyen, do vity
vied dung so d6 dieu she
yeti !Neu
diem chom sao se cho phep citi thien hieu quit phis
(hose hieu suit bang thong). Tuy
ninon, s6
diem tong gian d6 chem sao cang 16n bao
Phan Tien Tang
MSV: A13162
Trong 21
CAC KT THUAT SO
.
DUNG TRONG WiMAX
nhieu Oil viec gild
guy&
ch(mg 6 may thu cang kh6 bey nhieu. D6 la vi !chi de cat vj td
IQ duqc tang gin nhau nen chi chn mOt gia tri nhe nhieu 11 c6 the gay ra 16i truyen.
MA Gray:
Gifin
d6
IQ cho so d8 (lieu the chi m vecta truyen cho tit ca cac lien hqp tCr dli
lieu. Mgi lien hqp tir dtt lieu phid duqc phis phei mOt vecta IQ duy Sits MA Gray la
mOt phuong phi') cho su phiin phdi nay, sao cho cat diem conh nhau trong yam sao
chi lank nhau mOt bit dan. MA nay giup gam thieu d le l6i bit. MA Gray ce the duqc
ml dung cho tit ca cat
so d6

dieu the PSK (BPSK, QPSK, ) va QAM (16QAM,
64QAM, 256QAM ).
Decimal
Gray Coding
0
0,0,0,0
1
0,0,0,1
2
0,0,1,1
3
0,0,1,0
4 0,1,1,0
5
0,1,1,1
6
0,1,0,1
7
0,1,0,0
Dedmai
Gray Coding
8
1,1,0,0
9
1,1,0,1
10
1,1,1,1
11
1,1,1,0
12

1,0,1,0
13
1,0,1,1
14
1,0,0,1
15
1,0,0,0
Bang 2.1 Ma Gray
0000
0
0001
0
0100
0
0101
0
1100
0
1101
0
11:00
0
1031
0
0011
0111
1111
1011
0
0

0 0
0010
0110
1110
1010
0 0
0
0
IBM 2.7 Gidn dd IQ cia 16QAM khi thing and Gray
2.1.6. Khodng bdo
4
(GUARD PERIOD)
Ta they 6 hinh tren, phin ISI cos viec truyin tin hieu OFDM c6 the bj sai do dieu
kien cila qui trinh x11 15r tin hieu, beri vi may thu Icheng nhen duqc thong tin mia
symbol duqc truyen
dip
theo. Dieu d6 c6 nghia 11 may thu cen mOt ldwang then gian
c6 dO dii xfic djnh bang thoi gian symbol c6 ich di c6 the xac djnh duqc symbol
OFDM. IChoing then gian nay gqi la orthogonality Interval.
Phan Tien Tang
MSV: A13162
Trang 22
CAC K! THUAT STY DUNG TRONG WiMAX
C6 the giant tut huerng ISI tOi tin hieu OFDM bang cich them Arlo cic kho
ing

bio ve 6 truck cua
m6i
symbol. Khoing bio ve tuly la bin copy
tan

hoin theo chu ky,
lam ma rang chi& dii cua don sang symbol. NO duqc tao ra bing cach lay plan
cutSi
dm symbol OFDM de dua vac) pit
du.
Do vay viec dua Arlo cic bin copy cult
symbol
noi
duoi nhau tao thinh mOt tin hieu lien tac, Wog c6 stir elm (loan ey ch8
n6i.
Nhu vay viec
sao chop
du cuoi
cua symbol di tao ra mat khoitng thiri gian symbol dii
han va giii dieu the n6 mi Ichong c6
sYna

1
Kt
lieu
IN) N-1

Kt
Mu Mar N

Kt Wu the N•1
Binh 2.8 Chen khoong that gian
bao Are
cho
mai

ky hieu
2. L 7. Too
cdc hiss OFDM
MOt 1E9 hieu OFDM bang tan
g6c
c6 the duqc tact ra trong mien so tru6c khi
duce dieu the vac) cic sang mang con
de
truyen din. De tao ra mat OFDM bang
tan
g6c, mOt luang
dit lieu di
duqc
s6 has trutc tien duqc thiu the
stY clang cic m8 hinh
dieu the chung nhu PSK hottc QAM. Sau do, nhing ky hieu dO lieu nay duqc chuyen
n6i flap
thanh song song truck khi that hieu dieu the cic sang mang con. Cac sang
mang con duqc lay mitt veri t6c da N/T„ veri N la s6 sang mang con Ara T, 11 Ichoting
than gian ky hieu OFDM, khan); tan
se
gifts hai sang mang con Ice can la 2II/N. Cu6i
ding tilting
matt tren m6i
sang mang con
duqc
tang
hqp lai thanh mOt miu OFDM.
Mat 1c9 hieu OFDM duqc tao ra b6i mat he thong OFDM c6 N song mang con gam N
miu va miu tit* m cua mOt1c9 hieu OFDM

N-1
X
m
=

expt
j
2ffmn
}

m 5N-1

(2.2)
N

6
day X„ lb
ky
hieu di lieu duqc
truyen
ten song mang con dui n. Phucmg trinh
2.2 tacmg duong veri host gang IDFT tren chai dit lieu. Dieu nay cling c6 the sir clang
IFFT v6i hieu qui thac hien tuang dining nhu IDFT.
VI
voy, tren thuc
to
IFFT duce
that hien tren chuii di lieu tai mat
du
pith

OFDM cho dieu the bang tan
g6c
vi FFT
duqc thuc hieu tai dau thu de giii di& cite bang tin
g6c. Cuoi can& mOt ky
hien
OFDM bang tan g6c
duqc
dieu the bOi mat sting mang trey than') tin hieu phis vi duqc
Phan Tien Ting
MSV: A13162
Trang 23
CAC KT THUAT SiT DUNG TRONG WiMAX
truyen den deu thu. Trong mien tin s6, dip img niy II de chuyen du tit ci nhttng sang
mang tir Wing tin g6c deng thiri len tin s6 sang mang. Hinh 2.9 cho they mOt bO phit
OFDM gem 4 song mang con vi qui trinh tao ra mOtIcS
,
hieu OFDM.
Chu& bit
Binh 2.9 B6 phat OFDM 4 song mang
2.1.8. M8 td kfi hieu OFDM
a.
Man then
plan
Sang OFDM duqc tao ra nho Bien &Si Fourier ngtrqc, Ichoing then gian niy dtrqc
xem nhu IA Ichoing th&i gian co ich mkt icsr hieu
Tb.
Bin sao cis chu Id k, hieu c6 ich
cu6i citing T
g

,
ductc
g9i lk den t6 min hoin CP, duce sfr dung de hieu qui han tong
tip
hqp da dutmg, trong khi yen duy tri tfnh trqc giao cia cic song mang con. Hlnh
2.10 bieu clan du frac
icsr
hieu OFDM trong mien thin gian.
41

►
-

INE
T
s

4

►

Hinh 2.10 Cite tnic man thol gian ctia kit hieu OFDM
b.
Man
tin
Iwo
Imre pc
1
ON Mot


w^^

OS W
d
if

Binh 2.11 M6 td tan so OFDM
Phan Tien Ting
MSV: A13162
Trang 24
r
impaa
-
s gas
111.8011a
adiermis 00101 Wet
U.
tea
yob* rtheref01011101ale
CAC KT THUAT SLY DUNG TRONG WiMAX
LOp vet lg mks WirelessMAN-OFDM lit (km veto di& cho OFDM. Dft lieu duqc
gfri trong khung mia cic hieu OFDM. MOt kg hieu OFDM
duqc
Mo ra ter cic song
mang vi ce FFT duqc xic djnh bai s6 song mang. CO 3 loci sting mang duqc se dung
6 clay:
—
Cic song mang dit lieu (DC): cho
fruyin
din dft

—
Cic song mang hoa tieu: cho cic raw dfch trot tinh Mac nhau.
—
Cic song mang khung gii trj (Null): khung truyen din tit ci, duqc dung cho
cic dii bio ye vi cic sang mang DC.
Muc dich cda cac dii bato ye la cho phtp tin hieu suy giitm vi tao clang "tubng
gach" (Brick Wall) FFT. NO ding g6p phin xoi be giao thoa gifts cic kenh.
2.1.9. aunt khung.
MOt khung
duqc
chia &AM cic khung nhe DL vi UL. Nhfitg khung nhe DL vi
UL
duqc
bit
dim
voi 8 preamble (cho blot gioi han
s6
song mang mkt symbol) de tim
lai thong tin ve
kenh
truyen vi cho phip may thu tlm lai dip ting
kenh. O
FCH vit DL
MAP chira thong tin
ye
nOi dung khung (vi trf vi kieu dieu cho cOtt m8i burst) vi duqc
dieu the - BPSK.
Hinh 2.12 Cdu trek khung 802.16 OFDM
2.2. KT thu$t OFDMA cho mpg WIMAX
OFDM khai thic phin tip tin

s6 caa
kenh da duerng bei ma hod vi dan xen
th8ng tin qua sting mang con truOc khi truyen din. Dieu chi OFDM co the
duqc
that
hien hieu qui vei bien
tt61
Fourrier nguqc nhanh (IFFT), mil cho phop
mOt s6
luqng
16n song mang con (len tai 2048) v6i dO phitc tap thip. Trong mOt he th6ng OFDM,
tili nguyen khit dung trong mien then gian la cic hieu OFDM vi trong mien tin
s6 la
cic sting mang con. Cic tai nguyen thbi gian vil
tin s6
c6 the duqc sip xep thrinh cic
kenh con de
oip
phit cho tong nguei so dung. Da truy nhip ghop kenh phan chia theo
tin so trim
giao (OFDMA) la mOt ke hoach ghip kenh da truy nh$p de cung cip hoar
Phan Tien Ting
MSV: A13162
Trang 25
CAC IC! THUAT Sti DUNG TRONG WiMAX
dOng ghdp kenh ens luting dtt lieu tir nhilu ngubi su dtmg tren cac kenh con throng
xu6ng vi da truy nhip doting len Uri cac kenh con dutmg len. Nhitu ngubi dung cling
chia se met bang
tin nin
duqc goi IA OFDMA. Mgi ngubi dung c6 the dtng met

so
sting mang con da djnh truck hoc thay del toy theo thong tin can truyen (str diiu
khien nay phi thuOc vao lap MAC).
Cong nghe OFDMA cho phep nhang sang mang con duqc gin Ufa cac ngubi
dung Ichac nhau. VI dv cac sang mang con 1, 3 va 7 c6 the duqc gin cho ngubi dung 1,
va cac sting mang con 2, 5 va 9 cho ngubi dung 2. Nfring nhom sang mang con My c6
the duqc xem nhu cac kenh con. OFDMA cho phep kich thuOc FFT nhe hcm de di
thien chili luqng dhi yeti cac kenh c6 giai thong thip ham.
2.2.1. Nguyen I) co bdn
WIMAX dung cong nghe da truy nh$p kenh OFDM lep MAC, vei viec hO trq
ben hai phuang phap truyin song deg FDD va TDD.
U'u diem cua phuang phap My lit cho phip linh hoot thay dei de rong bang ten
len hoac
xu6ng vi
vay c6 the thay del the dO phat hoic thu dtt lieu chu kh8ng phai la
c6 djnh nhu
trong ADSL hay trong CDMA.
Trong Wi-Fi thi
tat ca cac
tram deu truy nh$p met each ngiu nhien den diem truy
cep AP, vi vey m8 khoang each khac nhau to
mai
nut den AP se lim giam thong luqng
cua
mang. Nhung b 16p MAC ctla 802.16 thi qua trInh truy nhip cua
mai thus bao la
duqc djnh twat vi v(ty cac tram chi c6 duy nhit met
len cash tranh kenh
truyin din la
thei diem m fillip mpg. Sau

mai
thai diem de thi
mai
tram dirge tram
goc gin
cho
met khe thbi gian, khe thin gian d6 c6 the me rOng hay co hgp lai trong qua trinh
truyen
din.
4
,11111111116L
ne
chunk
frequency
User
A
•
Uwe
•
Um
C
1111
User D
Hinh 2.13 Sr sap xip theo hai chau trong OFDMA
2.2.2. Malin qc 111th vuvt
Uu diem ctia viec det
sin
lich trinh nay la viec truyen din
van hoot ttOng
met each

On djnh trong tnrtmg hqp qua tai vi
s6
luqng thug bao ding IcSr vuqt qua cho phdp lam
Phan Tien Tang
MSV: A13162
Trang 26