????t? ???t?a ?p?????????? ????? ?

About This Presentation

Title:

????t? ???t?a ?p?????????? ????? ?

Description:

: . 4 ... – PowerPoint PPT presentation

Number of Views:24

Avg rating:3.0/5.0

Slides: 31

Provided by: Kosta90

Category:

more less

Transcript and Presenter's Notes

Title: ????t? ???t?a ?p?????????? ????? ?

1
????t? ???t?a ?p??????????????? ?
???ep????????a?? T?µata??????? ??. 4

?e?????? ?s?st??µ?s?? ??a????
?a? ?e?????? ??af?????t?ta?

2
?as???? a???? ?s?st??µ?s??

?? fa???µe?? t?? p???d??de?s?? sta ?a????a t??
d??t??? ????t?? ep?????????? p???a?e? t??
eµf???s? d?as?µß?????? pa?eµß???? (ISI -
Intersymbol Interference).
?st? f(t) ? ????st??? ap????s? t?? s????????
?a?a???? (f??t?? p?µp??, ?a????, f??t?? d??t?).
?? ?aµßa??µe?? s?µa ?a ??e? t? µ??f?
St? d??t? µ?a e?d??? d??ta??, ? ?s?sta?µ?st??
(equalizer), a?a?aµß??e? t?? a?t?µet?p?s? t??
ISI.
?s?st??µ?s? ???µ??eta? ?p??ad?p?te ?e?t?????a
epe?e??as?a? s?µat?? p?? µe???e? d?ast??? t?
d?as?µß????? pa?eµß???.

3
?as???? a???? ?s?st??µ?s??

S?st?µa ep????????a? µe ??aµµ??? p??sa?µ?st???
?s?sta?µ?st?

? ???d?? t?? ?s?sta?µ?st? ??e? t? µ??f?
St???? ? s?ed?asµ?? t?? heq(t), ?ste ? ???d??
t?? ?s?sta?µ?st? ?a te??e? st? x(t).
Se a??et?? efa?µ???? ? ?s?sta?µ?st?? p??pe? ?a
e??a? ??????? µetaßa???µe??? ??a ?a pa?a??????e?
t?? a??a??? t?? ?a?a????

4
?at??????p???s? ?s?sta?µ?st??

?e ß?s? t? ???t???? ße?t?st?p???s??
???t???? µ???st?? p??a??f??e?a? (Maximum
Likelihood Criterion - ML) Se ???e ???????
st??µ?, ? a????e?t?? pa???e? ap?fas? ?p?? e???
s?µß????, ?ste ?a µe??st?p??e?ta? ? p??a??t?ta
s?st?? ap?fas??, ded?µ???? t?? t?µ?? t??
?aµßa??µe??? s?µat??. ???a? ß??t?st??
?s?sta?µ?st??, a??? µe????? p???p????t?ta?.
???t???? µ?de??sµ?? t?? d?as?µß?????? pa?eµß????
(Zero-forcing Criterion - ZF) ? ?s?sta?µ?st??
µ?de???e? t? d?as?µß????? pa?eµß???. ???a? p???
ap?? ???t???? a??? µe ßas??? µe?????t?µa ?t? de?
?aµß??e? ?p??? t? ????ß?.
???t???? e????st?? µ?s?? tet?a??????? sf??µat??
(Minimum Mean Square Error Criterion - MMSE)
??a??st?p??e? t? µ?s? tet?a?????? sf??µa t??
e??d?? t?? ?s?sta?µ?st?, se s??s? µe t??
ap?ste???µe?? a???????a. ?aµß??e? ?p??? t?? t?s?
t? d?as?µß????? pa?eµß??? ?s? ?a? t?? p??s?et???
????ß?.

5
?at??????p???s? ?s?sta?µ?st??

?e ß?s? t? d?µ? t?? ?s?sta?µ?st?
?????s??? ?s?sta?µ?st?? (transversal equalizers)
??as??? FIR f??t?a, µe sta?e?? a???µ?
s??te?est??, µ?sa ap? ta ?p??a d????eta? t?
?aµßa??µe?? s?µa.
?s?sta?µ?st?? µe d?µ? lattice ?s?sta?µ?st?? µe
e?d??? ???µa??t? d?µ? p?? t??? d??e? µe?a??te??
e?e????a (????st? t??? ?s?sta?µ?st? / d?µ?
pipelinable). ?p?te????ta? ap? ??a? a???µ? ?µ????
ßa?µ?d??, p?? a?t?st???e? st?? a???µ? t??
s??te?est?? e??? e????s??? ?s?sta?µ?st?. ?
p??s???? ep?p???? ßa?µ?d?? ???eta? e????a.

6
?at??????p???s? ?s?sta?µ?st??

?e ß?s? t? ??????? µetaß??? t?? ?s?sta?µ?st?
Sta?e??? ?s?sta?µ?st?? (fixed or preset
equalizers) ?? s??te?est??
?p????????ta? µ?a f??? st?? a??? t?? ?e?t?????a?
t??? ?a? pa?aµ????? sta?e???.
???sa?µ?st???? ?s?sta?µ?st?? (adaptive
equalizers) ?? s??te?est??
µetaß?????ta? s??e??? ?ste ?a pa?a????????? t??
???????? µetaß???? t?? ?a?a????.
?e ß?s? t? ??aµµ???t?ta ? µ? t?? d?µ?? t???
G?aµµ???? ?s?sta?µ?st??
? ???d?? e??a?
??aµµ??? s????t?s? t?? e?s?d?? t???.
??-??aµµ???? ?s?sta?µ?st??
? ???d?? de?
e??a? ??aµµ??? s????t?s? t?? e?s?d?? t??? (p.?.
?? ?s?sta?µ?st?? p?? st??????ta? st? ???t????
ML).

7
T? ???t???? ML

??µ? e??? ?s?sta?µ?st? MLSE
(Maximum Likelihood Sequence Estimation)

?????e? ??e? t?? p??a??? a???????e? ded?µ???? ?a?
ep????e? e?e??? µe t? µ???st? p??a??f??e?a t??
?aµßa??µe??? s?µat??
?pa?te? ???s? t?? ?a?a???? µet?d?s?? ?a? t??
?ata??µ?? t?? ????ß??.
?e???? p???p????t?ta. ? ???s? t?? a??????µ??
Viterbi µe???e? d?ast??? t??? ?p?????sµ??? ?a?
ep?t??pe? t?? efa?µ??? se µ????? µ????? ?a????a.
????p????t?ta ap? O(NL) se O(?ML), ?p?? L t?
µ???? ?a?a????, ? ? t??? t?? a?faß?t?? ?a?
? t? p????? t?? s?µß????

8
T? ???t???? ZF

? ?s?sta?µ?st?? s?ed???eta? ?ts? ?ste ?a
µ?de???e? t? d?as?µß????? pa?eµß??? (apa?te?ta?
e?t?µ?s? t?? ?a?a????)
?
???ad? ??a? ?s?sta?µ?st?? ZF ?pe???? µ????? e??a?
??a a?t?st??f? f??t?? ??a t?? ????st??? ap????s?
t?? ?a?a????
?as??? µe?????t?µa de ?aµß??e? ?p??? t? ????ß?
µe ap?t??esµa ?a p???a?e? e??s??s? st??
s????t?te? ?p?? ? ap????s? s????t?ta? t??
?a?a???? pa???s???e? µe???e? ß???se??.

9
T? ???t???? MMSE

? ?s?sta?µ?st?? s?ed???eta? ?ts? ?ste ?a
e?a??st?p??e? t? µ?s? tet?a?????? sf??µa st??
???d? t??
?? ? ?s?sta?µ?st?? ??e? ?pe??? µ???? ?a? ?
????ß?? e??a? AWG
??e????t?µa e?a??st?p??e? t? ?????sµa t?? ?s????
t?? ISI ?a? t?? p??s?et???? ????ß?? ?a?
pet??a??e? µ????te?? ???µ? sfa?µ?t??.

10
G?aµµ??? ?s?st??µ?s?

?as??? d?µ? e??? ??aµµ???? e????s??? ?s?sta?µ?st?

? e?s?d?? st? d??ta?? ap?fas?? e??a? ??a?
??aµµ???? s??d?asµ?? t?? e?s?d?? t?? ?s?sta?µ?st?
st?? t?????sa ?a? t?? p??????µe?e? ????????
st??µ??, µe ß??? p?? ?a???????ta? ap? t? e??st?te
???t????
??a? ??aµµ???? ?s?sta?µ?st?? µp??e? ?a e??a? e?te
ZF e?te MMSE.
?p??e? ?a ???p????e? ?a? st? d?µ? lattice.

11
?? G?aµµ??? ?s?st??µ?s?

?as??? d?µ? e??? ?s?sta?µ?st? µe epa?at??f?d?t?s?
ap?f?se?? (DFE)

?as??? ?d?a ? ISI p?? ?fe??eta? se p??????µe?a
s?µß??a (p?? ????? a????e??e?) µp??e? ?a
e?t?µ??e? ?a? ?a afa??e?e? ap? t? ?aµßa??µe??
s?µa p??? ap? t?? a????e?s? t?? ep?µe???
s?µß????.
? ???d?? t?? ?s?sta?µ?st? d??eta? ap? t? s??s?

12
?? G?aµµ??? ?s?st??µ?s?

??a? µ?-??aµµ???? ?s?sta?µ?st?? µp??e? ?a e??a?
e?te ZF e?te MMSE, a?????a µe t? ???t???? p??
???s?µ?p??e?ta? st?? ?p?????sµ? t?? s??te?est??
t??.
?? ?? p??????µe?e? ap?f?se?? e??a? s?st?? ?a? t?
µ???? t?? feedback f??t??? a??et? µe????,
ep?t?????eta? p????? e???e??? t?? ISI.
???ß??µa ap?te?e? t? fa???µe?? t?? d??d?s??
?a??? ???? se p??????µe?e? ap?f?se??
d?ad?d??ta? sta ep?µe?a s?µß??a µ?s? t?? f??t???
a??d?as?? (feedback) p???a???ta? e?de??µ???? ??a
????.
Ge???? ? DFE pa???s???e? ?a??te?? s?µpe??f??? ap?
t??? ??aµµ????? ?s?sta?µ?st??.

13
???sa?µ?st??? ?s?st??µ?s?

?as??? d?µ? e??? p??sa?µ?st???? ??aµµ????
?s?sta?µ?st?

?? s??te?est?? t?? ?s?sta?µ?st? de? e??a?
sta?e??? a??? e??µe?????ta? µe t? ß???e?a
?at??????? a??????µ?? ?ste ?a pa?a????????? t??
a??a??? t?? ?a?a????.
?p???e? µ?a p?????a a??????µ?? ??a t?? p??sa?µ???
t?? s??te?est??.

14
???sa?µ?st??? ?s?st??µ?s?

?as???? a???? p??sa?µ?st???? ?s?st??µ?s??
S?????? p??? t? µet?d?s? t?? p????f???a?,
µetad?deta? µ?a a???????a e?µ???s?? p?? ß????e?
st?? a????? p??sa?µ??? t?? s??te?est?? t??
?s?sta?µ?st?.
??ad??as?a s?????s?? µe ß?s? t? s?µa ?????? ek,
a?a?e????ta? s??e??? ?? s??te?est?? t??
?s?sta?µ?st? ?a? µe???eta? epa?a??pt??? ?
s????t?s? e?a??st?p???s??.
?et? t? s?????s?, ? a??????µ?? e?te pa???e?
t??? s??te?est?? (µ???? ?a ??ße? ??a a???????a
e?µ???s??) e?te µetaßa??e? st?? ?a??d????µe?? ap?
t?? ap?f?se?? ?e?t?????a (???s?µ?p??e? t??
ap?f?se?? ??a ta s?µß??a p????f???a? ?? a???????a
e?µ???s??).
??f??? p??sa?µ?st???? a??????µ?? p??sfat?
?at?????a a??????µ?? p?? a???p????? ta
?a?a?t???st??? t?? µetad?d?µe??? s?µat?? ?a? de?
apa?t??? a???????a e?µ???s??.

15
?p????? p??sa?µ?st???? a??????µ??

?as???? pa?????te? t?? ap?d?s?? p??sa?µ?st????
a??????µ??
???µ?? s?????s?? ? a???µ?? t?? apa?t??µe???
epa?a???e?? ?ste ? a??????µ?? ?a s??????e? a??et?
???t? st? ß??t?st? ??s?, ?ta? ? e?s?d?? e??a?
st?s?µ?.
Misadjustment ?a??µet??? p?? µet??e? t??
ap????s? t?? te????? µ?s?? sf??µat?? e???
a??????µ?? (sf??µa sta?e??? ?at?stas??) ap? t?
ß??t?st? e????st? tet?a?????? sf??µa.
Tracking S?et??eta? µe t?? ??a??t?ta t??
a??????µ?? ?a pa?a??????e? t?? µetaß???? st?
?a????.
?p?????st??? p???p????t?ta ? a???µ?? t??
apa?t??µe??? p???e?? ??a t?? e?t??es? µ?a?
epa??????? t?? a??????µ??. ?d?a?te?a s?µa?t???
??a a??????µ??? p?a?µat????-??????.
????µ?t???? ?d??t?te? ??af??eta? se sf??µata
st???????p???s?? ? sf??µata a?apa??stas?? p??
p????pt??? ?at? t?? ???p???s? e??? a??????µ??.
S?ss??e?s? ?a??? µp??e? ?a ?d???se? se ast??e?a.

16
?p????? p??sa?µ?st???? a??????µ??

???t???a ep?????? ?s?sta?µ?st? st?? ????t??
ep????????e?
??st?? ?p?????st???? p?atf??µa?.
?ata????s? ?s????.
???µ?? ded?µ???? ?a? ta??t?ta ????s?? (ep?d????
sta ?a?a?t???st??? t?? ?a?a????, ??a ?a????????
t?? apa?t?se?? ap? t?? ?s?sta?µ?st?).
????st? a?aµe??µe?? ??????? d?asp??? t?? ?a?a????
(?pa???e?e? t?? apa?t??µe?? a???µ? s??te?est??
t?? ?s?sta?µ?st?, ??a ep??e??e? t? ??st?? t??, t?
????? epe?e??as?a? ??p).

17
?a?ade??µata p??sa?µ?st???? a??????µ??

? a??????µ?? LMS (Least Mean Square)
???s?µ?p??e? t? ???t???? MMSE.
?p?te?e? ap??p???s? t?? a??????µ?? steepest
descent. ?pa?te? µ???? 2?1 p??/sµ??? a??
epa?????? (??a ?1 s??te?est??)
?? ß?µa µ e????e? t? ???µ? s?????s?? ?a? t??
e?st??e?a.
?? x(n) s??µat??eta? e?te ap? t?? a???????a
e?µ???s?? e?te ap? t?? ???d? t?? st???e???
ap?fas??.

18
?a?ade??µata p??sa?µ?st???? a??????µ??

? a??????µ?? RLS (Recursive Least Squares)
??a??st?p??e? t? ??????? µ?s? ??? t?? sf??µat??
? pa??µet??? ? ?a?????e? t?? ??a??t?ta
pa?a???????s?? a??a???.
? ???µ?? s?????s?? ?a?????eta? ap? t?? p??a?a R.
??? ??????? s?????s? ap? t?? LMS, a??? ?a?
µe?a??te?? p???p????t?ta (2.5?24.5?)

19
?a???s?as? te?????? ?s?st??µ?s??

20
?e?????? d?af?????t?ta? (diversity)

??µeta??e???ta? t?? t??a?a f?s? t?? as??µat??
d??d?s?? ß??s???ta? a?e???t?te? d?ad??µ?? s?µat??
??a t?? ep????????a, µe d?af??et???
?a?a?t???st??? e?as????s??.
S?????? ? a???p???s? t?? diversity ???eta? st?
d??t?.
?a???s??p???? te?????? diversity
???s?µ?p?????ta? ??a t?? a?t?µet?p?s? t??
e?as????s?? e??e?a? ???µa?a?. Se s?????e?
ep?s??as??, t? ????t? ep????e?, a??µesa st???
sta?µ??? ß?s??, e?e???? p?? de? ep?s????eta? ? ?
sta?µ?? ß?s?? ep????e?, a??µesa se p????? ?e?a?e?
p?? ß??s???ta? se µe???? ap?stas? µeta?? t???,
e?e??? p?? ?aµß??e? t? ?s????te?? s?µa.
?????s??p???? te?????? diversity
???s?µ?p?????ta? ??a t?? a?t?µet?p?s? t??
e?as????s?? µ????? ???µa?a?. ??a??????ta? se
te?????? diversity st? ???? (space diversity),
st? s????t?ta (frequency diversity) ?a? st? ?????
(time diversity). ?p?s?? ?p?????? s??????e?
te?????? p?? a???p????? p?????? ???ste? ??a t??
?d?? s??p? (multiuser diversity).

21
?????s??p???? te?????? diversity

Space diversity (antenna diversity)
???s?µ?p?????ta? pe??ss?te?e? ap? µ?a ?e?a?e? p??
ap????? µeta?? t??? µ?s? µ???? ??µat?? ? pa?ap???
(????t?) ? de??de? µ??? ??µat?? (sta?µ?? ß?s??).
Frequency diversity ? p????f???a µetad?deta?
ta?t?????a se pe??ss?te?e? ap? µ?a f????se?
s????t?te? p?? ap????? pe??ss?te?? ap? t? e????
????? s?????? t?? ?a?a????. S?µa?t??? µe?????t?µa
? spat??? e????? ?????.
Time diversity ? p????f???a µetad?deta?
epa?a??pt??? se ??????? d?ast?µata p?? ap?????
pe??ss?te?? ap? t? ????? s?????? t?? ?a?a????
(p.?. ???t?? Rake st? DS-CDMA)

22
Te?????? space diversity

Ge???? d????aµµa ßa?µ?d?? e??? s??µat?? µe space
diversity

?at?????e? te??????
Selection diversity
Feedback diversity ? Scanning diversity
Maximal Ratio Combining diversity
Equal Gain Combining diversity

23
Selection Diversity

H ap???ste?? te????? se ???e ??????? st??µ?
ep????eta? e?e??? ? ?e?a?a t?? ?p??a? ? ???d??
pa???s???e? t? µe?a??te?? SNR.
? p??a??t?ta ?a ß?e???? ??e? ?? ?e?a?e? se s?µe?a
µe????? e?as????s?? e??a? p??? µ????.
???sf??e? s?µa?t??? ße?t??s? st? s??des? ????? ?a
apa?te? p??s?et? µetad?d?µe?? ?s?? ? p???p???a
?????µata.
?e? e??a? ? ß??t?st? te?????, ??at? ???eta?
spat??? p????, ?a??? de? ???s?µ?p?????ta? ???? ??
???d?? ta?t?????a.

24
Selection Diversity

?????aµµa p??a??t?t?? ?p??ßas?? e??? ?at?f????

G t? µ?s? SNR st?? ???d? ???e ???d??
? t? ?at?f??

??e? s?ed?aste? ? p??a??t?ta t? SNR se
t??????st?? ??a ???d? ?a ?epe???e? t? ?at?f?? ?,
s??a?t?se? t?? ????? ?/G.
25
Feedback Diversity (Scanning Diversity)

?a s?µata ap? ???e ?e?a?a d?at?????ta? µe sta?e??
se??? µ???? ?a ß?e?e? ??p??? p?? ß??s?eta? p???
ap? ??p??? p???a????sµ??? ?at?f??.
???s?µ?p??e?ta? a?t? t? s?µa µ???? ? ?s??? t?? ?a
p?se? ??t? ap? t? ?at?f??, ?p?te ? d?ad??as?a
epa?a?aµß??eta?.
?a???s???e? ??p?? ?e???te?? ap?d?s? a??? ??e? t?
p?e????t?µa ?t? apa?te?ta? µ??? ??a? d??t?? ?a?
ep?µ???? e??a? p??? ap?? st?? ???p???s?.

26
Maximal Ratio Combining Diversity

? ???d?? e??a? ?at??????? ??aµµ???? s??d?asµ??
t?? e??d?? ???? t?? ?e?a???.
?? SNR e??d?? e??a? t? ?????sµa t?? ep?µ?????
SNRs.
?pa?te? ??a d??t? ?a? ??a ?????µa ?e???sµ?? f?s??
??a ???e ?e?a?a (ta s?µata p??pe? ?a ??????
s?µfas???), ?a??? ?a? ??p??? ?????µa ??a t?
???µ?s? t?? ßa???.
???a? ? ?a??te?? ap? t?? ??aµµ???? te?????? space
diversity p?? pa???s??st??a? a??? ?a? ? p??
p???p????. G??eta? p?a?t??? µe t?? ße?t??s? t??
te?????? epe?e??as?a? s?µat?? ?a? t?? te???????a?
t?? receivers.

27
Equal Gain Combining Diversity

?a??µ??a te????? µe t?? Maximal Ratio Combining,
a??? ????? µetaß??t? ß???, ??a µe?a??te??
e?????a.
?a s?µata e??d?? t?? ???d?? ap??? ?????ta?
s?µfas??? p??? p??ste????.
? ap?d?s? e??a? ???a?? ?at?te??.

28
S??????e? ?ate????se??