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57 lines
1.4 KiB
Fortran
57 lines
1.4 KiB
Fortran
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subroutine encode4K25A(message,codeword)
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! A (280,70) rate 1/4 tailbiting convolutional code using
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! the "4K25A" polynomials from EbNaut website.
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! Code is transparent, has constraint length 25, and has dmin=58
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character*10 g1,g2,g3,g4
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integer*1 codeword(280)
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!integer*1 p1(25),p2(25),p3(25),p4(25)
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integer*1 p1(16),p2(16),p3(16),p4(16)
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integer*1 gg(100)
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integer*1 gen(280,70)
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integer*1 itmp(280)
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integer*1 message(70)
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logical first
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data first/.true./
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data g1/"106042635"/
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data g2/"125445117"/
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data g3/"152646773"/
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data g4/"167561761"/
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!data p1/1,0,0,0,1,1,0,0,0,0,1,0,0,0,1,0,1,1,0,0,1,1,1,0,1/
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!data p2/1,0,1,0,1,0,1,1,0,0,1,0,0,1,0,1,0,0,1,0,0,1,1,1,1/
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!data p3/1,1,0,1,0,1,0,1,1,0,1,0,0,1,1,0,1,1,1,1,1,1,0,1,1/
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!data p4/1,1,1,0,1,1,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,0,0,0,1/
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data p1/1,0,1,0,1,1,0,0,1,1,0,1,1,1,1,1/
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data p2/1,0,1,1,0,1,0,0,1,1,1,1,1,0,0,1/
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data p3/1,1,0,0,1,0,1,1,0,1,1,1,0,0,1,1/
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data p4/1,1,1,0,1,1,0,1,1,1,1,0,0,1,0,1/
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save first,gen
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if( first ) then ! fill the generator matrix
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gg=0
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! gg(1:25)=p1
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! gg(26:50)=p2
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! gg(51:75)=p3
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! gg(76:100)=p4
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gg(1:16)=p1
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gg(17:32)=p2
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gg(33:48)=p3
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gg(49:64)=p4
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gen=0
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! gen(1:100,1)=gg(1:100)
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gen(1:64,1)=gg(1:64)
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do i=2,70
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gen(:,i)=cshift(gen(:,i-1),-4,1)
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enddo
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first=.false.
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endif
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codeword=0
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do i=1,70
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if(message(i).eq.1) codeword=codeword+gen(:,i)
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enddo
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codeword=mod(codeword,2)
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return
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end subroutine encode4K25A
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