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OFDM Principle
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Objects
After the course, you will: Know the Concept of OFDM
Understand the OFDM Principle
Know the enefits and Drawbac!s of OFDM Understand the Key "echnolo#ies of OFDM
Know the OFDM Application
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Content
Basic Points enefits and Drawbac!s
Key "echnolo#ies
Application in D$ Application in U$
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Frequency selective fading Time selective fading
%adio Channel Characteristics
Multi&Path 'ffect "i(e&)ariant Channel
Fre*uency
Fre*uency
Transmitter
Receiver
"i(e
Power
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%adio Channel+s Proble(s to ol-e
Time selective
fading
OFDM
Technology
Frequency selective
fading
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.hat is OFDM /
OFDM: Ortho#onal Fre*uency Di-ision Multiple0in#, is a !ind of
(ulti&carrier trans(ission1
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.hy usin# OFDM /
andwidth utili2ation rate is hi#her than FDM
Fre*uency selecti-e fadin# is s(all
"i(e selecti-e fadin# is s(all
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OFDM Modulation and De(odulation
Modulation
Demodulation
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OFDM Principle Dia#ra(
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Content
asic Points Benefits and Drawbacks
Key "echnolo#ies
Application in D$ Application in U$
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OFDM enefits
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OFDM Drawbac!s
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asic Points enefits and Drawbac!s
Key "echnolo#ies
ycle Prefi! Technology Channel 'sti(ation
ynchronous technolo#y
Adapti-e Modulation and Codin#
Application in D$ Application in U$
Content
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Multi&Path 'ffect
34: #uardin# inter-al
Path "
"he second sy(bol in Path 5 interfereswith the first sy(bol in Path 6
Path #
44 74ntery(bol 4nterference8 will occur because of (ulti&path effect
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4f 34 is 4nserted
34: 3uardin# 4nter-al
Path "
Path #
$%
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4C4 rou#ht by 34
subcarrier #
Delayed subcarrier "
$% FFT %ntegrationTime & #'subcarrier s(acing
Part of subcarrier " causing
%% on subcarrier #
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4f CP is 4nserted
A(plitude
"i(e$% FFT %ntegral Time )ength
OFDM *ymbol )ength
P
CP7Cycle Prefi08
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asic Points enefits and Drawbac!s
Key "echnolo#ies
Cycle Prefi0 "echnolo#y hannel +stimation
ynchronous technolo#y
Adapti-e Modulation and Codin#
Application in D$
Application in U$
Content
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Channel 'sti(ation and %eference y(bols
"o esti(ate the fre*uency&do(ain channel tapdirectly by insertin# reference sy(bols7%81
TS36.211 DL RS, normal CP,1TX
One %
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%eference sy(bols $ocation
,ormal P *ingle
-ntenna
,ormal P Two
-ntennabearin# the radio resource unit of
the antenna 9
bearin# the radio resource unit
of the antenna 5
bearin# the data resource unit 4dle resource unit
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asic Points enefits and Drawbac!s
Key "echnolo#ies
Cycle Prefi0 "echnolo#y Channel 'sti(ation
*ynchronous technology
Adapti-e Modulation and Codin#
Application in D$
Application in U$
Content
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ynchroni2ation %e*uire(ents
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Carrier ynchroni2ation
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Carrier and y(bol ynchroni2ation
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asic Points enefits and Drawbac!s
Key "echnolo#ies Cycle Prefi0 "echnolo#y
Channel 'sti(ation
ynchronous technolo#y
-da(tive Modulation and oding
Application in D$ Application in U$
Content
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AMC7Adapti-e Modulation and Codin#8
dyna(ic adaption of the
(odulation sche(e
dyna(ic adaption of the
codin# sche(e
dyna(ic adaption of the bits
Performance
enhancements
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Content
asic Points enefits and Drawbac!s
Key "echnolo#ies
-((lication in D) Application in U$
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OFDM "i(e&Fre*uency tructure
%esource 'le(ent
%esource loc!
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andwidth Analysis
,ominal
Bandwidth
.M/01
51 ; < 59 5< 69
,umber of RB = 5< 6< < 599
Frequency Domain
Real Bandwidth
.M/01
519? 61> 1< @ 5;1< 5?
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OFDMA: Downlin! (ultiple access
Up to = AM can be used
%esistance to (ulti&path interference by Cyclic Prefi01
Friendly to M4MO1
ub&carriers
ub&fra(e
Frequency
Time
"i(e fre*uencyresource for User 5
"i(e fre*uencyresource for User 6
"i(e fre*uencyresource for User ;
yste( andwidth
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Content
asic Points enefits and Drawbac!s
Key "echnolo#ies
Application in D$ -((lication in 2)
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.hy select C&FDMA/
DF"&&OFDM 7DF"&
pread&OFDM8 in the
fre*uency do(ain
OFDM
*3FDM-
.*ingle arrier
FDM-1
,ot suitable for terminal
*uitable for terminal
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C&FDMA: Uplin! (ultiple access
Up to 5= AM can be used
in#le carrier (odulation achie-eslower Pea! to A-era#e %atio
7PAP%8
FDMA is efficiently achie-ed
throu#h FF" operation
,in#le Carrier ,ub&fra(e
Frequency
Time
"i(e fre*uencyresource for User 5
"i(e fre*uencyresource for User 6
"i(e fre*uencyresource for User ;
,yste( andwidth
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OFDMA and C&FDMA Co(parison
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DF"&&OFDM Process
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OFDM -s DF"&&OFDM
B OFDM PAP% is far hi#her than DF"&&OFDMB "he hi#her (odulation (ode DF"&&OFDM adopts, the hi#her PAP% it #ets1
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Distributed DF"&&OFDM enefitDrawbac!
B $ocali2ed DF"&&OFDM is adopted in $"' U$1
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u((ary
.hat is OFDMOFDMA/ OFDM enefitsDrawbac!s/
%elated Key "echnolo#ies/
.hy C&FDMA/ Difference between DF"&&OFDM OFDM/
DF"&&OFDM "ypes/
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