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112 lines
3.1 KiB
Fortran
112 lines
3.1 KiB
Fortran
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subroutine encode_msk144(message,codeword)
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! Encode an 80-bit message and return a 128-bit codeword.
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! The generator matrix has dimensions (48,80).
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! The code is a (128,80) regular ldpc code with column weight 3.
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! The code was generated using the PEG algorithm.
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! After creating the codeword, the columns are re-ordered according to
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! "colorder" to make the codeword compatible with the parity-check
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! matrix stored in Radford Neal's "pchk" format.
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!
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character*20 g(48)
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integer*1 codeword(128)
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integer*1 colorder(128)
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integer*1 gen144(48,80)
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integer*1 itmp(128)
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integer*1 message(80)
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integer*1 pchecks(48)
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logical first
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data first/.true./
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data g/ & !parity-check generator matrix for (128,80) code
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"24084000800020008000", &
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"b39678f7ccdb1baf5f4c", &
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"10001000400408012000", &
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"08104000100002010800", &
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"dc9c18f61ea0e4b7f05c", &
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"42c040160909ca002c00", &
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"cc50b52b9a80db0d7f9e", &
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"dde5ace80780bae74740", &
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"00800080020000890080", &
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"01020040010400400040", &
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"20008010020000100030", &
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"80400008004000040050", &
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"a4b397810915126f5604", &
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"04040100001040200008", &
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"00800006000888000800", &
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"00010c00000104040001", &
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"cc7cd7d953cdc204eba0", &
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"0094abe7dd146beb16ce", &
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"5af2aec8c7b051c7544a", &
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"14040508801840200088", &
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"7392f5e720f8f5a62c1e", &
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"503cc2a06bff4e684ec9", &
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"5a2efd46f1efbb513b80", &
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"ac06e9513fd411f1de03", &
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"16a31be3dd3082ca2bd6", &
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"28542e0daf62fe1d9332", &
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"00210c002001540c0401", &
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"0ed90d56f84298706a98", &
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"939670f7ecdf9baf4f4c", &
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"cfe41dec47a433e66240", &
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"16d2179c2d5888222630", &
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"408000160108ca002800", &
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"808000830a00018900a0", &
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"9ae2ed8ef3afbf8c3a52", &
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"5aaafd86f3efbfc83b02", &
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"f39658f68cdb0baf1f4c", &
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"9414bb6495106261366a", &
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"71ba18670c08411bf682", &
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"7298f1a7217cf5c62e5e", &
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"86d7a4864396a981369b", &
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"a8042c01ae22fe191362", &
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"9235ae108b2d60d0e306", &
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"dfe5ade807a03be74640", &
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"d2451588e6e27ccd9bc4", &
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"12b51ae39d20e2ea3bde", &
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"a49387810d95136fd604", &
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"467e7578e51d5b3b8a0e", &
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"f6ad1ac7cc3aaa3fe580"/
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data colorder/0,1,2,3,4,5,6,7,8,9, &
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10,11,12,13,14,15,24,26,29,30, &
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32,43,44,47,60,77,79,97,101,111, &
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96,38,64,53,93,34,59,94,74,90, &
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108,123,85,57,70,25,69,62,48,49, &
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50,51,52,33,54,55,56,21,58,36, &
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16,61,23,63,20,65,66,67,68,46, &
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22,71,72,73,31,75,76,45,78,17, &
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80,81,82,83,84,42,86,87,88,89, &
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39,91,92,35,37,95,19,27,98,99, &
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100,28,102,103,104,105,106,107,40,109, &
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110,18,112,113,114,115,116,117,118,119, &
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120,121,122,41,124,125,126,127/
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save first,gen144
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if( first ) then ! fill the generator matrix
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gen144=0
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do i=1,48
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do j=1,5
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read(g(i)( (j-1)*4+1:(j-1)*4+4 ),"(Z4)") istr
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do jj=1,16
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icol=(j-1)*16+jj
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if( btest(istr,16-jj) ) gen144(i,icol)=1
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enddo
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enddo
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enddo
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first=.false.
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endif
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do i=1,48
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nsum=0
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do j=1,80
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nsum=nsum+message(j)*gen144(i,j)
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enddo
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pchecks(i)=mod(nsum,2)
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enddo
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itmp(1:48)=pchecks
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itmp(49:128)=message(1:80)
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codeword(colorder+1)=itmp(1:128)
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return
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end subroutine encode_msk144
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