2018-02-08 21:28:33 -05:00
|
|
|
subroutine encode174(message,codeword)
|
2018-08-05 11:33:30 -04:00
|
|
|
! Encode an 87-bit message and return a 174-bit codeword.
|
|
|
|
|
! The generator matrix has dimensions (87,87).
|
|
|
|
|
! The code is a (174,87) regular ldpc code with column weight 3.
|
2018-02-08 21:28:33 -05:00
|
|
|
! The code was generated using the PEG algorithm.
|
|
|
|
|
! After creating the codeword, the columns are re-ordered according to
|
|
|
|
|
! "colorder" to make the codeword compatible with the parity-check matrix
|
|
|
|
|
!
|
|
|
|
|
|
|
|
|
|
include "ldpc_174_87_params.f90"
|
|
|
|
|
|
|
|
|
|
integer*1 codeword(N)
|
|
|
|
|
integer*1 gen(M,K)
|
|
|
|
|
integer*1 itmp(N)
|
|
|
|
|
integer*1 message(K)
|
|
|
|
|
integer*1 pchecks(M)
|
|
|
|
|
logical first
|
|
|
|
|
data first/.true./
|
|
|
|
|
|
|
|
|
|
save first,gen
|
|
|
|
|
|
|
|
|
|
if( first ) then ! fill the generator matrix
|
|
|
|
|
gen=0
|
|
|
|
|
do i=1,M
|
|
|
|
|
do j=1,11
|
|
|
|
|
read(g(i)( (j-1)*2+1:(j-1)*2+2 ),"(Z2)") istr
|
|
|
|
|
do jj=1, 8
|
|
|
|
|
icol=(j-1)*8+jj
|
|
|
|
|
if( icol .le. 87 ) then
|
|
|
|
|
if( btest(istr,8-jj) ) gen(i,icol)=1
|
|
|
|
|
endif
|
|
|
|
|
enddo
|
|
|
|
|
enddo
|
|
|
|
|
enddo
|
|
|
|
|
first=.false.
|
|
|
|
|
endif
|
|
|
|
|
|
|
|
|
|
do i=1,M
|
|
|
|
|
nsum=0
|
|
|
|
|
do j=1,K
|
|
|
|
|
nsum=nsum+message(j)*gen(i,j)
|
|
|
|
|
enddo
|
|
|
|
|
pchecks(i)=mod(nsum,2)
|
|
|
|
|
enddo
|
|
|
|
|
itmp(1:M)=pchecks
|
|
|
|
|
itmp(M+1:N)=message(1:K)
|
|
|
|
|
codeword(colorder+1)=itmp(1:N)
|
|
|
|
|
|
|
|
|
|
return
|
|
|
|
|
end subroutine encode174
|
