6.OFDM Principle 40

8/18/2019 6.OFDM Principle 40

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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



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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#


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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Key "echnolo#ies

Cycle Prefi0 "echnolo#y hannel +stimation



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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Key "echnolo#ies

Cycle Prefi0 "echnolo#y Channel 'sti(ation

*ynchronous technology


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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Key "echnolo#ies Cycle Prefi0 "echnolo#y

Channel 'sti(ation


-da(tive Modulation and oding


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


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 ;

yste( andwidth


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Content


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 ;

,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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Documents

6.OFDM Principle 40