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Algorithm Design DocumentDocument no.: CRAW_???_001 draft v0.1
Spectrum Sensing AlgorithmDesign Document
Abstract: This document illustrates the algorithm design
for CRAWs spectrum sensing proect. This document
includes introduction! o"er"ie# of the sensing algorithms!
the co"ariance $ased sensing algorithm and the spectrum
$ased h%$rid detection algorithm for signal em$edded in
spurious and noise. Detailed descriptions on
implementation of the algorithms are included. Channel
selection filters are also attached in the appendi&.
Role Name Designation Signature
Owner 'eng (onghong Research )cientist
Reviewer 'hang Wei*iang
+e Tran ,huoc Cuong
)%ed -a"een AltafAhmed
Research anager
Research /fficer
)enior Research /fficer
Approver /h )er Wah ,roect anager! CRAW
Revision 1.0 Date of Issue 1 Dec 00
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COPYRIGH NOIC!Cop%right 2 00 $% 3nstitute for 3nfocomm Research 43R5! )ingapore. All rights reser"ed.
-o part of this pu$lication ma% $e reproduced! transmitted! transcri$ed! stored in aretrie"al s%stem! or translated into an% language #ithout the #ritten permission of 3 R.
"ARNING
Chec6 document control s%stem for the latest "ersion $efore using or cop%ing.
R!#ISION HISORY
Revision Date Authors Comments Reasons for
Change0.1 0 /CT 00 (. 7.
'eng1.0 1 D8C 00 (. 7.
'eng
CONRI$%ORS
/h )er Wah
9ruce +e
'hang Wei*iang
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D!(INIIONS) ACRONY*S + A$$R!#IAIONS
AA A"erage Amplitude
ADC Analog to Digital Con"erter
CA Co"ariance A$solute alue
CRAW ,roect Code -ame! Research ,roect on W;RA-
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A$-! O( CON!N
COPYRIGHT NOTICE.....................................................................................................................................................2
WARNING..........................................................................................................................................................................2
REVISION HISTORY.......................................................................................................................................................2
CONTRIBUTORS..............................................................................................................................................................2
DEFINITIONS, ACRONYMS & ABBREVIATIONS....................................................................................................3
TABLE OF CONTENT......................................................................................................................................................4
1. INTRODUCTION.........................................................................................................................................................5
1.1. PURPOSE....................................................................................................................................................................51.2. SCOPE........................................................................................................................................................................51.3. REFERENCEDOCUMENTS..........................................................................................................................................5
2. OVERVIEW OF SENSING ALGORITHMS.................................................................................................... .........7
3. COVARIANCE BASED SENSING ALGORITHM.................................................................................................. .
4. IMPLEMENTATION OF THE CAV ALGORITHM...............................................................................................11
5. SPECTRUM BASED HYBRID DETECTION.........................................................................................................12
!. IMPLEMENTATION OF THE SHD ALGORITHM......................................................................................... .....15
7. APPENDI" 1# DIGITAL FILTERS...........................................................................................................................1!
. APPENDI" 2# MATLAB CODES.............................................................................................................................1$
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/0 Intro1uction
This document descri$es the algorithm design for the CRAW spectrum sensing proect.
The main purpose for this proect is to detect the presence of R< signals in the 77 ! signal e&istsL other#ise! signal not e&ists
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Algorithm Design DocumentDocument no.: CRAW_???_001 draft v0.1
/: he choice of channel selection filter
To ha"e a good adacent channel signal reection! the channel selection filter should
ha"e stop;$and attenuation as high as possi$le! prefera$l% higher than G0d9.
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1( )
faIP =
20 Spectrum 5ase1 h>5ri1 1etection)ometimes the recei"ed signal ma% not onl% contain the desired signal and #hite noise!
$ut also some spurious signal and interference. The spurious signal ma% $e generated $%
Analog;to;Digital Con"erters 4ADC5 due to its non;linearit%. 3f the sensing antenna is near
some electronic de"ices! the spurious signal generated $% the de"ices can $e strong in
the recei"ed signal. We need signal processing techni*ues to handle the
spurious=interference.
There are t#o h%pothesises: 0H : signal not e&istsL and 1H : signal e&ists. 3f there is
possi$le spurious signal! the recei"ed signal samples under the t#o h%pothesises are
therefore respecti"el% as follo#s:
0
1
: ( ) ( ) ( )K
i
i
H x n n n =
= +
1
1
: ( ) ( ) ( ) ( )K
i
i
H x n s n n n
=
= + + !
#here )(ns is the transmitted signal passed through a #ireless channel 4including fading
and multipath effect5! ( )i n is a possi$le spurious signal and )(n is the #hite noise
samples. -ote that )(ns can $e the superposition of multiple signals. The spurious signal
( )i n is normall% an e&tremel% narro#$and signal. an% detection algorithms cannot
differentiate the transmitted signal )(ns and spurious signal ( )i n . Therefore! these
algorithms #ill produce false alarm #hen spurious signal presents! that is! e"en ifinterested signal does not presents! the algorithms #ill #rongl% report signal presentB due
to the interference of the spurious signals. To sol"e this pro$lem! #e propose a detection
algorithm $ased on po#er spectrum densit% or
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Algorithm Design DocumentDocument no.: CRAW_???_001 draft v0.1
The flo#;chart of the algorithm is gi"en in
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/ 12
0
( ) ( ) , 0,1,..., 1N M
T m
m
n X n n M
=
= =
Alternati"el%! #e can also use the AA at terminating case defined as
/ 1
0
( ) ( ) , 0,1,..., 1N M
T m
m
n X n n M
=
= =
The pre;#hitening "ector ( )nW is simpl% chosen as ( )T n or A ( )T n . The "ector can $e
computed offline once for all and stored.
,: hreshol1 setting
The threshold 1 is set $ased on the re*uired pro$a$ilit% of false alarm at terminating
case. +et faP $e the re*uired pro$a$ilit% of false alarm. At terminating case! the
spurious detection method is used for I tests. To guarantee high relia$ilit%! the num$er
of tests I should $e large. +et the ratio ( ) /x meann of test i $e ( )i . Reorder ( )i into
1( )i #ith descending order. Then the threshold 1 is chosen as
1 1( )
faIP =
The threshold 2 is set $ased on the re*uired pro$a$ilit% of false alarm #hen $oth
spurious signal and noise present. +et faP $e the re*uired pro$a$ilit% of false alarm.
The threshold 2 should $e chosen such that the pro$a$ilit% of decision signal presentB
is less than faP .
40 Appen1i< /8 1igital filters
The coefficients of the filter #ith $and#idth G7K are as follo#s 4centered at fre*uenc%
E.E 7K! after truncation to 10 $its5:
1 1 0 ;1 ; ; ;1 0 0 ;1 ;1 0 0 0
;1 ; ; 0 1 1 0 0 0 1 0 ;1 ;1 0 0
0 ; ; ; 0 1 1 0 ;1 0 H 1 ;1 ;1 1
1 ;1 ;H ;E ;H ;1 1 1 ;1 ; 1 E E 1 ;1 0
;1 ; ;M ;G ;1 1 ;1 ;E ;H M 11 1 ;1
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Algorithm Design DocumentDocument no.: CRAW_???_001 draft v0.1
G ; ;11 ;1 ; ;1 0 ;G ;11 ; 1H 1E 1
11 1 11 ;H ;1 ;1 ; 0 ;E ;1 ;E ;1E E 1 0
;1 M G 1 ; ;G ; ;H ;1G ;HG ;EG ;1 10 H
; ;G H MM EH ;1 ;E ;H 1M ;MH ;E ;E ;0 1
E11 1 ;0 ;E ;E ;MH 1M ;H ;E ;1 EH MM H ;G
; H 10 ;1 ;EG ;HG ;1G ;H ; ;G ; 1 G M
;1 0 1 E ;1E ;E ;1 ;E 0 ; ;1 ;1 ;H 11 1 11
1 1E 1H ; ;11 ;G 0 ;1 ; ;1 ;11 ; G
;1 1 11 M ;H ;E ;1 1 ;1 ;G ;M ; ;1
0 ;1 1 E E 1 ; ;1 1 1 ;1 ;H ;E ;H ;1
1 1 ;1 ;1 1 H 0 ;1 0 1 1 0 ; ; ; 0 0 0 ;1 ;1 0 1 0 0 0 1 1 0 ; ;
;1 0 0 0 ;1 ;1 0 0 ;1 ; ; ;1 0 1
1
The coefficients of the filter #ith $and#idth 10I7K 4centered at fre*uenc% .GM0G
7K! after truncation to 10 $its5 are as follo#s:
G 1E ;10 ;M ;H ;M ; ;HM ;GG ;1E0 ;1H 1H H H ME
MM EH GH 1H 1 ;1H1 ;G ;G0 ;H0M ;H0 ;E ;G1 ;1 1H 1EM E
H H1 EM E 1 ;M ;1 ;0H ;MH ;HG ;HH ;G0 ;E1 ;110 HE
1ME H10 HH H0 EM HH M ;G1 ;1 ;H0 ;HE ;HE ;HE ;E ;G
;H E HM HG H EH G 0 ;MG ;E0 ;H ;HE ;HE ;HM
;HM ;1G ;EE 11 G M0 HGH H HH0 H 0H M ;11 ;E ;H0E ;HE
;H ;H ;G ;1M1 ; 1HM 0 H1M HE HM0 HG 1 G ;1G ;1M
;H ;HM ;HM ;H1 ;1 ;1G 11 1H E HHE E00 HM HG 0G 1H ;M;0 ;E0 ;HEG ;E0E ;HM ;H1M ;M ;1 HG 1M GH HGE E0M HM0 H10 0
11E ;GH ;E ; ;HH ;E11 ;HG ;H01 ;GG ;M 1 E1 M0 H0 E11 H0
M0 E1 1 ;M ;GG ;H01 ;HG ;E11 ;HH ; ;E ;GH 11E 0 H10 HM0
E0M HGE GH 1M HG ;1 ;M ;H1M ;HM ;E0E ;HEG ;E0 ;0 ;M 1H 0G
HG HM E00 HHE E 1H 11 ;1G ;1 ;H1 ;HM ;HM ;H ;1M ;1G G
1 HG HM0 HE H1M 0 1HM ; ;1M1 ;G ;H ;H ;HE ;H0E ;E
;11 M 0H H HH0 H HGH M0 G 11 ;EE ;1G ;HM ;HM ;HE ;HE
;H ;E0 ;MG 0 G EH H HG HM E ;H ;G ;E ;HE
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;HE ;HE ;H0 ;1 ;G1 M HH EM H0 HH H10 1ME HE ;110 ;E1
;G0 ;HH ;HG ;MH ;0H ;1 ;M 1 E EM H1 H E 1EM 1H
;1 ;G1 ;E ;H0 ;H0M ;G0 ;G ;1H1 1 1H GH EH MM ME H H
1H ;1H ;1E0 ;GG ;HM ; ;M ;H ;M ;10 1E G
60 Appen1i< &8 *atla5 co1es
The atla$ code for the CA algorithm is included in the follo#ing as an illustration to
the method.
OO atla$ codes for the CA algorithm
-)P000L OO the num$er of s%m$ols generated
threPL OO input the threshold here
hfPL OO input filter here
+P10L OO the smooth factor
-TP1L OO the num$er of filter taps
OO The pre;#hitening matri& generation $ased on filterR-1PKeros4+!-TQ+;15L
for nP1:+
R-14n!n:nQ-T;15PhfL
end
OO The pre;#hitening matri&
R-PR-1R-1SL
RR-Ps*rtm4R-5L
RR-Pin"4RR-5L
OO 3nput the signal samples here
&1PL
OO
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Algorithm Design DocumentDocument no.: CRAW_???_001 draft v0.1
End of Document