DAI HOC QUOC
GIA
HA
NOI
Ten ae
tai
Nghien
CLFU
giai phap
cong
nghe
FPGA cho cac
inng
dung
truyen thong.
Ma so: QC 08-12
Chu nhiem
de
tai: Ts.
Nguyin
Quoc Tuan
DAI HOC QUOC GIA HA
Npl_
TRUNG
TAM THONG TIN
THU
VIEN
OOG ^00000^5
Hanoi
2009
1.MUCLUC

7.8 Tai lieu tham khao
2.
Bang giai thich cac
chfr vi§t
tat:
Ky
hieu
TiingAnh
Tieng Viet
ADC Analog to Digital Converter
ADSL Asymmetric Digital Subscriber Line
AMI Alternate Mark Inversion
ANSI American National Standards
Institute
AOC A Overhead Control Channel
ATM Asynchronous Transfer Mode
ATU ADSL Transceiver Unit
ATU-C ADSL Transmission Unit at the
Central Office
ATU-R ADSL Transmission Unit at the
Remote Side
AWGN
BER
BRI
BRITE
BT
CAP
CBI
CDMA
CDSL

Don vi thu phat (truyen dan)
Don vi truyen dan ADSL
j:
cap dich vu
Don vi truyen dan ADSL phi
Nhieu Gauss, trang cong
tinl-
Ty
le
bit loi
ISDN
toe
do
CO
ban
Mo rong truyen dan ISDN to
Thuat toan phan bo bit chat
c
Dieu che bien do-pha khong
Nhieu giua cac bang
Da truy cap phan chia theo
n-
Khach hang DSL
Uy ban tu van
v6
dien thoa
quoc te
Dap ling xung kenh
Loi
ghcp

EOC
ET
ETSI
FDM
FEC
Voice Coder / Decoder
Cyclic Prefix
Central Processing Unit
Cycle Redundancy Check
Carrier Serving Area
Cyclic Suffix
Digital to Analog Converter
Digital Added Main Line
Dynamic Bandwidth Optimization
Direct Current
Discrete Cosine Transform
Digital Data Service
Decision Feed-back Equalizer
Discrete Fourier Transform
Digital Loop Carrier
Discrete
MuUi-Band
Discrete MultiTone
Discrete
MuhiScale
Digital Suscriber Line
Digital Signal Processing
Discrete Wavelet Multitone
Transform
Discrete Wavelet Transform

Da am rai rac
Da phan giai rai rac
Duong day thue bao so
Xii ly
tin hieu so
Bien doi da song con rai rac
Phep bien doi song con
roi
rac
Lai,
khir
tieng vong
Thuat toan hieu suat
ciia
Campello
Kenh boat dong theo kieu nhiing
Thuat toan nang
lugng
chat
ciia
Campello
Vien tieu chuan vien thong chau Au
Hop kenh phan chia theo tan so
Kiem
loi huong
thuan
CODEC
CP
CPU
CRC

Cyclic Suffix
Digital to Analog Converter
Digital Added Main Line
Dynamic Bandwidth Optimization
Direct Current
Discrete Cosine Transform
Digital Data Service
Decision Feed-back Equalizer
Discrete Fourier Transform
Digital Loop Carrier
Discrete Multi-Band
Discrete MultiTone
Discrete MuhiScale
Digital Suscriber Line
Digital Signal Processing
Discrete Wavelet Multitone
Transform
Discrete Wavelet Transform
Echo-Canceled Hybrid
Efficiency
Embedded Operations Channel
E-Tightness
European Telecommunications
Standards Institute
Frequency Division Multiplexing
Forward Error Control
Bg ma hoa va giai ma thoai
Tien to vong
Bg (don vi)
xir

Vien tieu chuan vien thong chau Au
Hop kenh phan chia theo tan
s6
Kiem loi huong thuan
FEQ Frequency-Domain Equalizer
FEXT Far End CrossTalk
FFE Feed-Forward Equalizer
FFT Fast Fourier Transform
FIR Finite Impulse Response
FPGA Field Programable Gate Array
FSK Frequency Shift Keying
FSN Full-service Network
FTTH Fiber To the Home
FWT Fast Wavelet Transform
G.DMT The full-rate Recommendation
G992.1
HDSL High-bit-rate Digital Subscriber Line
HDSL2 Second-generation High-bit-rate
Digital Subscriber Line
HDTV High-definition Television
HSF High SuperFrame
HPF High-pass Filter
IBI
Inter-Band Interference
ICl
Inter-Carrier Interference
IDFT
Inverse Discrete Fourier Transform
IDWMT
Inverse Discrete Wavelet Multitone

loai
Mang cap quang toi tan nha
Phep bien doi song con
nhai
Khuyen nghi toan
toe
G.99:
ADSL
Duong day thue bao so
toe (
Duong day thue bao so
toe
thu
2
Truyen hinh phan giai cao
Sieu khung
Mach
Igc
thong cao
Nhieu trong bang
Nhieu giua cac song mang
Phep bien doi Fourier roi
rai
Phep bien doi da song con n
Phep bien doi ngugc song
c(
Vien Ky thuat Dien va Dien
Phep bien doi Fourier nhanh
Dap ling xung v6 han
Mang so da dich vu

Multiplexing
PAM Pulse Amplitude Modulation
PAPR
Peak-to-Average
Power Ratio
PCM Pulse Code Modulation
PDF Probability Density Function
POTS Plain Old Telephone Service
PR Perfect Reconstruction
PSD Power Spectrum Density
PSK Phase Shift Keying
PSTN Public Switched Telephone Network
QAM Quadrature Amplitude Modulation
QMF Quadrature Mirror Filter
Sai so binh phuang trung binh toi thieu
Mach
Igc
thong thap
Dau cuoi
duong
day
Thich nghi du phong
Co so thong tin quan ly
Da loi vao da loi ra
Xii
li hang trieu
lenh
Dieu che da song mang
Bg
Igc

Dieu che bien do cau phuong
Bg
Igc girong
cau phuong
RA Rate-Adaptive
RADSL Rate-Adaptive DSL
RF Radio Frequency
RFI
Radio Frequency Interference
RLSE Recursive least squared Error
RS Reed Solomon
SCM Single Carrier Modulation
SDSL Symmetric DSL (Single-pair DSL)
SDR Software Define Radio
SER Symbol Error Rate
SISO
Single Input Single Output
SF Super Frame
SNR Signal to Noise Ratio
STFT Space Time Frequency Transform
STM Synchronous Transfer Mode
TCM Trellis Coded Modulation
TDM Time Division Multiplex
TEQ Time - Domain Equalizer
TIR
Target Impulse Response
UADSL Universal ADSL
UAWG Universal ADSL Work Group
UEC Unit
-

Ty so cong suat tin hieu tren
Bien doi khong thoi gian tan
Che do truyen dan dong bg
Dieu che ma
luoi
Hop kenh phan chia thoi gia
Bg can bang mien thoi gian
Dap ling xung mong muon
ADSL toan cau
Nhom lam viec ADSL toan
c
Rang bugc nang lugng don \
Rang bugc
"tap"
dan
vj
Duong day thue bao so
toe
d
Buu chinh Vien thong Viet n
Cac kieu duong day thue bac
Mang khong day thanh pho
Mang khong day
cue
bo
3.
Danh sach
nhirng ngu-oi
tham gia
thue

nhan.
Ths
Chuyen nghanh
Dien
tir
Vien
thong
Dien
tii
Vien
thong
Dien tu Vien
thong
Dien
tir
Vien
thong
Co quan cong tac
Dai hgc Cong nghe,
DHQG Ha ngi
Dai hgc Cong nghe DHQG
Ha noi
Dai hgc Cong nghe DHQG
Ha ngi
Dai hgc Cong nghe DHQG
Ha ngi
4.
Danh muc cac bang so lieu
Bangl:
Kich

Hinh 15
Hinh 16
Hinh 17
He thong thu phat dua tren MCM dien hinh
Kit FPGA Virtex-4 Xillinx
Software Radio Platform - FPGA Design
IPCore
FFTv3_2 ciia
Xillinx
SDR cho he truyen dan da song mang dua tren OFDM
SDR cho he truyen dan da song mang dua tren DMT
So do nguyen li bg tao du lieu
16-QAM
Diem chom sao thu /phat
So do nguyen li bg dieu che va chen Cp (OFDM)
Dang tin hieu sau khi dieu che va chen Cp
Pho va dang tin hieu sau khi dieu che
So do khoi bg giai dieu che dua tren FFT
So do khoi tien
xii
li tin hieu
I/Q
va tach
d6ng
bg cua OFDM
Thong tin dong bg OFDM
Kien
triic
Cordic
xii

- Cho truyen dan da tan roi rac DMT cho cac he thong c6 day
- Cho truyen dan Hgrp kenh phan chia tan so true giao (OFDM) cho cac he
thong khong day
• Kha nang
ling
dung
thue
ta cua cac ket qua:
- Thiat
ka
cac he truyen dan OFDM cho cac mang khong day di dong tha he 4.
- Cho phep ling dung thiat
ka
cho cac mang truy cap bang rgng c6 day khac
nhuADSL2^
6.3 Ket qua dao tao
•
San pham dao tao
- Dai hgc: 01 khoa luan tot nghiep sinh vian Dai hgc chat lugng cao
• Bo xung tai lieu cho giao trinh
- Bo xung mot phan kian
thiic
cho giao trinh giang day Dai hgc
lian
quan
dan
phan
mam
dinh
nghia

bkg phSn mam
(SDR) la he
th6ng
thu phat
cl
dugc kha nang lap trinh cao cho truyen thong. Trong mot he thong SDR, tat
trong thiat bi khi
xii
li dugc hoan thien
b^ng
phSn
mem. Do vay cac thanh
p
th6ng sii
dung SDR cho phep
linh
dong va la cac giao
thiic
mang thong minh
phan chia
tSn
s6
true
giao (OFDM) va da
t^n
rai rac (DMT) dung cho cac he
cha da song mang (MCM) da tra thanh cong nghe
diau
cha thong dung ch
(ADSL,

tuong tu
(Analoj
Ian
thiet
ka
cac
thilt bj
v6 tuyen nay,
chiic
nang
ciia
he trong thiat bi dugc
khong
CO
the thay doi mot
each
de dang. Nha su phat trian manh me
ciia ki
th
hieu
s6
(DSP), day
c6ng
kha lap trinh (FPGA) va cac bg xu li muc dich cl
cho phep ling dung
xii
li tin hieu bang phan
mam.
Cac
diau

true
tiap
voi
cac bg
bian
doi tuong tu - so (ADC) va
bian
doi so - tuan]
Cac bg nay c6 tha noi true tiep vai antenna. Nhu vay, trong cac he thong
SDI
cac tin hieu dugc
thue
hien bang phan
mam
va phan
mam
noi
true tiap
toi ant
Do
sir
han cha
ciia
gia thanh san pham, hieu nang va han cha
ciia
kha na
cac he thong SDR
thue sir
la rat hiem. Tren
thue

dii da
dap
ling
nhiau
ling
dung do anh huong
ciia
cac
he dieu hanh (OS). CPU voi mot FPGA dua
tran
DSP la he
thdng
SDR
dii
manh
da xii
li
tin hieu va dieu
khian.
• Dieu che da song mang (MCM)
Tat ca cac he thong truyan du lieu
dau
su dung mot kieu cong nghe diau cha nao do
da
ma hoa
dir
lieu so roi
da
truyan. Tai may thu, viec giai diau cha dugc
thirc

nhau.
Da
tai dua ra so do khoi mot thiat bi thu phat MCM thong thuong trong hinh 1 (ma
diau
cha DMT hay OFDM la mot trong cac
ling
dung
ciia
MCM). Cac
chiic
nang
ciia
bg
thu phat MCM c6 tha dugc chia thanh 2 loai: ma hoa kanh va
diau
cha. Ma hoa coi nhu
la tian
xii
ly truoc khi cac song mang con doc lap nhu nhau dugc
diau
cha.
Diau
che
MCM la loai diau cha cac song mang con doc lap,
sii
dung bian doi Fourier ngugc va
chen dai bao ve. Trong khi do ma hoa kanh eo tha thay doi dang ka giiia cac chuan,
DO lieu
^ Xao tron
Ma hoa

Hinh 1
He thong thu phat dua tren MCM dien
hinh
11
Co 3
vSn da
phai lam
da
thiat ke SDR cho mot he
thdng
thu phat dua
tran N
tian la
vSn
de dieu che/giai dieu che dua
tran
MCM, van
da thii
hai la tian xu
bao
d6ng
bg nhip va
ddng
bg khung giiia hai he thong thu va phat dua
tran
MC
da
cuoi Cling la ma hoa
kanh
va

bit dung cho moi phan
tii
song mang con se phu thugc vao ky thuat dieu ch
(hoac xac xuat bit loi mong muon khi truyan). Vi du, QPSK se doi hoi 2
bil
phan
tii
mang con. So lugng cac phan tu song mang con (hay loai dieu cha) se
dinh bang giao thiic hoac chuan dugc
sii
dung.
Diau che DMT/OFDM dua
tran
thuat toan bian doi ngugc Fourrier roi rac
theo thong thuong thi
sir
dung thay bang giai thuat bien doi ngugc Fourier nhar
iDFT la mot chiic nang c6 loi vao la chuoi dii lieu bieu
dian
cac tan so dugc
day du lieu do va tra lai mot tap cac he so dugc tim thay trong du lieu do biau
thai gian. Bg dieu che DMT/OFDM cho
thSy
ca FFT va IFFT
dau
c6 cung
thuac dugc ki hieu
-
Njjf.
Day chinh la so lugng thong tin loi vao va thong tin

mang con
tran
thue
ta
phai la
true
giao khi
chiing
dugc gian
each,
do vay
chii:
gay nhiau
ISn
nhau. IFFT tim
thSy
trong OFDM coi du lieu
phSn tii
mang cor
bien dieu la loi vao va tao ra du lieu
chu6i
thai gian tai
16i
ra. Tin hieu mien
nay se
chiia
tat ca tong
ciia
tung tin hieu phan
tii

sii
dung IFFT de dieu che , con
biau
thiic (2)
sii
dung FFT
dugc sii
dung
da
giai
diau
cha trong truyen
din
MCM.
Vi biau
tuong
OFDM
chiia
nhiau phan
tii
song mang eon biau dian nhiau bit
nan
khoang
ciia
bieu tuong OFDM nay c6 the tuong doi dai. Diau nay lam giam
nhilu
xuyan
biau
tuong
(ISI)

biau
tugng DMT/OFDM. Trong khoang bao ve do, may thu c6 tha van nhan dugc
cac phian ban bi cham cua biau tugng truoc gay ra. May thu khi do se bo qua phan bao
ve truyan tin. Trong nhiau he DMT/OFDM, dai bao ve nay la
sir
keo dai tao ra tuan hoan
ciia
biau tugng DMT/OFDM.
Da
dai bao ve tao ra tinh tuan hoan thi dai bao ve la ban
sao
ciia
phan cuoi cung
ciia biau
tugng DMT/OFDM dugc dinh vao phan bat dau
ciia
chinh biau tugng do.
Nhu vay khoang thoi gian
eiia
mot ki hieu OFDM/DMT la
T^
=
(T^
+
T^,
(voi
To
la khoang thoi gian
A''
mau IFFT va

song mang
con
thii
nghiem vao trong bieu tugng OFDM/DMT (ggi la
pilot-subcarrier).
Vi cac bieu tugng pilot song mang con la da biat doi voi may thu
nan
may thu c6
tha
sii
dung cac pilot
da
uac
lugtig
cac dieu kien kanh qua tat ca cac cac phan
tii
mang
con va
bii
dap mot each thich dang. Diau nay con dugc ggi la biau tugng pilot ho trg dieu
cha
(pilot symbol assisted modulation - PSAM)
13
Trong cac he MCM kiau khung, moi khung thuong bit
dhu bkng
nu
nao do cac biau tugng mao dau. Co nhiau ly do cho viec do, mot trong so cac
may thu bugc phai c6 kha nang bat dugc vi tri bat dau
ciia
mot

CO
tha dugc
siia
chua bang
each sii
dung du lieu khong loi tu cac song
manj
Hieu suat
ciia
mot vai kiau ma hoa c6 the dugc nang
lan
trong MCM nho bu
Xen ke xao trgn cac bit
dir
lieu sao cho cac bit lian
tiap
trong luong du lieu
du
cac song mang con khac nhau trong cac biau tugng
ciia
MCM. Diau nay eo n
loi nhom trong cac song mang con lian tiep nhau se khong bi xay ra nhu trong
day du lieu khong dugc xen ke. FEC la mot trong cac phuong thiic ma hoa
trgng nhat doi voi truyen dan dua
tran
MCM. Nhung vin
dk
khac nhu: c6
the
xao trgn de lam trang cac luong du lieu, nen du lieu de giam kich thuoc cua do

IFFT/FFT vai N
=
64
(2)
Ma
hoa
16-QAM
(3) Cung cap Cp dam bao
d6ng
bg giua tram thu va tram phat
(4) Cung dp khoang bao ve (mo rgng vong)
dilu
khian.
(5) Co
kha
nang linh boat
Thiet ke trinh bay a day se dat dugc muc tiau nay. Hon nua, da tai se cung
mem kiem soat
tran
cac thong
s6
nhu la kat qua cua
da
tai. He
thdng diau
cha h(
thong
IMHz
cho DSL, khong rgng hon so voi
1.14MHz

Phan
mam
Xillinx
ISE
8.2i xac dinh cho phan
nan
kit FPGA Virtex-4 Xillinx dugc
chi ra trong hinh 2. Kit nay bao gom c6 mot bg Xilinx XtremeDSP phat trian san xuat
bai Nallatech va mot thu phat radio 2.4GHz san xuat boi Fidelity COMTECH,
Inc
XtremeDSP. Cac bg phat trian tinh nang Nallatech Benadda Pro PCI/USB bao gom mot
Virtex-4 FPGA,
16
MByte cua RAM va hai bg A/D va D/A chuyan doi.
Nallatech da cung cap mot so vi du mau thiat
ka
FPGA c6 tha dugc
sir
dung voi cac
kit XtremeDSP. Mot trong nhiing thiat
ka
la mot giao dien don gian cho
FFT/IFFT
voi
PCI bus. Khi khao thiat
ka
nay,
da
tai da dua vao va phat trian mot
nan

sau
15
do kich boat noi dung trong buffer
da
truyan
din.
Du lieu dugc dugc
viat
v;
theo chu trinh va nhip
diau
khian
ciia
bg
dilu
cha (IFFT)
r6i
dugc dge ra
khoi 1
mot bg diau khian dge, bg
diau
khian
dge
don gian diau khian nhip
dge,
so c
giua cac lan
dge
tu bg nha.
Du lieu dugc sinh ra do dge bg nho (MEM) dugc

khong phai la muc
tiau
thiat ke
ciia
de tai do do
tran thue ta
no dugc miau t
duong noi giiia tram phat va tram thu. Tin hieu nhan dugc tai may thu dugc
1
dua toi bg bian doi tuong tu - so (ADC) . Khoi nay se gui du lieu loi ra toi
be
Chiic nang
ciia
bg tian
xii
li la phan tich va xac dinh tin hieu dong bg khung,
1
to vong Cp, tach ra tin hieu
phiic
(I/Q) va xap thang hang chiing. Tin hieu
ti'
tha bi v6 hieu trong
truong
hgp mot hoac ca hai
ciia
cac
kanh
dau vao
giii
toi

c6 tha chay hoan toan
tran
may tinh PC hoac hoan toan
tran
kit
FPGA hoac c6 the chay lai gep ca
tran
PC lan
tran
kit FPGA
Mac du chiic nang tu kiem tra khong dugc
sii
dung o trong bao cao nay
ciia
de tai,
nhung
da
tai ciing da tao mot giao dien de kiem soat cac boat dong he thong dugc thiet
ke trong cha do chay lai gep.
Mot trong nhung muc tieu
ciia da
tai la cung
c4p
mot ca so giai thuat SDR
da
c6
tha dong bg giua may thu va may phat da song mang voi bang tan rgng
da
c6 tha kiam
soat that nhieu tian trinh phat khi c6 tha.

hiau dugc cac
yau
cau doi voi MCM, chiing toi chay
mot so chuong trinh chuan
sii
dung FFT/IFFT don gian c6 san
da
khai thac va so sanh
doi chiing Hinh 4 chi ra IPcore FFT/IFFT cua Xillinx cho cac kit Virtex
IlPro,
Virtex4
©FFTv3_2 (XilinxFast Fourier
Transfer
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TRUNG
VAM
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thiat
thue
hien mot
chuAn
MCM theo mot he nao c6 san,
dc tai gia dii
dieu cha
IFFT-64
(16 bit) vai cac song mang con c6 khoang each la
25,6KI
gian keo dai
biau
tugng bang 0,500 giay.
Bang
1
dual day cho thay anh huong
ciia
kich thuoc IFFT vao thoi gia
cau
ciia ling
dung MCM.
Da
duy tri mot khoang thai gian biau tugng MCM
t6c
do
l4y mlu
phai tang so vai kich thuac IFFT. Kich thuoc IFFT hoac bang
chinh
bkg s6
lugng dii lieu no tao ra. Tuy nhian CPU cac may tinh PC thu

160
320
640
Bang
J:
Kich thuac IFFT cho
802.11
su
dungOFDM
Do hieu nang
ciia
CPU lian tuc tang nho
xii
li duong ong, cac CPU da
core,
triple core ). Cac kit FPGA tich hgp DSP vao bg vi
xii
ly vai toe do
cang cao. Nhu vay mot so rang bugc
vh
kich thuac IFFT cung se dugc giai q
each phan
viing
thiet ke chinh xac giiia phan
mam
va
phSn
ciing, cac
yau
du \

S
6 a
Resource
Estimator
100%
o
ode45
n
Scope
/^.
Hinh
5: SDR cho he truyen dan da song mang dua tren OFDM
Hinh 4 va hinh 5 cho so
d6
thiet ke SDR cho he truyan dan da song mang dua
tran
OFDM va DTM. Thue ra ve nguyan
tSe
hai he nay khong khac nhau nhieu do do trong
khuon kho bao cao
da
tai chi trinh bay cho he truyen dan MCM dua
tran
OFDM.
c) Thiet ke bo phat
May phat truyen MCM
thue
hien cac chiic nang thao tac bit nhu phan chia khung
(dinh khung), ma hoa, xen ke xao trgn dii lieu, phan chia cac song mang con
da

-s
f
'
^
1 biau
tugng
mien tan so - Tuy thuoc vao chat
lugng
duang truyan (SNR) ma
each
ma
hoa dugc
lira
chgn QPSK,
16-QAM
hay 64-QAM
Da
tai su dung
16-QAM
de giam
thieu cac loi sinh ra cho he thong khi truyan tin va do vay bang thong I/O bus giam he so
4.
19
Fie Edt
View
Simulation
Format Tools Help
D cf
y
a

//;; Ichoi
dieu che
(IFFTva
chen Cp).
i) Khoi phat tin hieu
16-QAM:
Dung
da
gia lap du lieu
16-QAM
cho (
kiem tra dugc chi ra trong hinh 7. Khoi phat tin hieu
16-QAM g6m
2
pi
nhau, tao ra tin hieu chom sao I/Q nha phuang phap anh xa. Du lieu
nj
dugc tao nha may phat gia lap
nglu
nhian. Du
lieu
nay dugc coi la dia c
dinh du lieu chom sao
16-QAM
dugc chiia trong bo nha ROM.
Da
phi
yau
cAu
bian

ch. ra trong hinh 8(a). Cac tin hieu nay co tinh tu nhian cao dam bao gia
mau Ian can bat ki c6 gia tri khac nhau trong
chuSi
du liau dai
-^
2500 m
he thong phat va thu de thue hien dong bo.
[!]
QC0B_2/Genl/Q/QAM_I
*
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til d
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ly bg
diau
cha
dua
tran
IFFT
va
chen
Cp
dugc
chi
ra trong hinh
9. Bg
dieu cha dua
tran
iFFT-64 dugc viat dua
tran
ngon ngii VHDL
CO
tha
nhiing
vao
Xillinx Simulator
da
thue hien thiat
ka
he
thong
va mo
phong.

=
(xnjo,
xn_ij

,
xnj^sj
sinh
ra
cap
day dii
lieu
loi ra
xk_r =
{xkj-Q,
xk_rj
.
xkj-^^}
xkj
=
{xkjo,
xkji
,
xkj^sj
Moi phep
bian
doi
chiam khoang
hon 200
lenh may.
Da

(Pipelined Stream
I/O
mode).
So
mau
dii
lieu trong
mot
khung
16i
vao bang
so
mau
dii
lieu trong
1
khung
loi ra sau
khi bian
doi
iFFT.
21
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Disp
Y
Axis
lalal^
XYPIot
•
*

••
XYPId
-•
0
XAxis
:
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•
••
••
••
«
••
FTinh
8a: Diem chom
sao
phat
Hinh
8b: Diem chom sao thu
Cac
kh6i
chiic nang khac
nhu
RAM FIFO,
bg
dam
"Counter"
,
cac

[IGOOO'
iNmr^nr S
t^
[a ^ .: ! IKS 03 ^
GD-»^
CD
>^
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Win
[Ready
xn_r« >4<_(t
>kjm
Kn_im xfi_ind«x
skaii rtd
busv
»«cl_irn/
uout
bud intr wt
done
*m
-^
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FFT v3
2
din
dout
—
empb/
>
full

'od<
////i/;
9:
Sa dS nguyen
li
bo
di^u
ch^
va chen Cp (OFDM)
Moi luong du lieu loi ra IFFT hay ggi la cac biau tugng
{Xk_re,
Xkjm)
dugc
xii
li nhu nhau do vay se co 2 khoi nhu nhau, song song
da tiln
xu li tin hieu
truac khi dugc truyan dan. Hai bg nho RAM FIFO se dugc
diing
da nha dem dii
lieu nham cho phep chuyan doi
t6c
do (thay doi thai gian keo dai cac bieu tugng)
sao cho loi vao FIFO eo toe do thap (thoi gian keo dai biau tuong dai) va loi ra
FIFO CO
toe
do cao (thai gian keo dai biau tuang
ngSn)
de thua 1 khoang thoi
gian chen Cp. Do chiau dai Cp dugc chgn la 16