mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-22 20:28:42 -05:00
49 lines
1.0 KiB
Fortran
49 lines
1.0 KiB
Fortran
|
subroutine encode204(message,codeword)
|
||
|
|
! Encode an 68-bit message and return a 204-bit codeword.
|
||
|
|
! The generator matrix has dimensions (136,68).
|
||
|
|
! The code is a (204,68) regular ldpc code with column weight 3.
|
||
|
|
! 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_204_68_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=1,17
|
||
|
|
read(g(i)(j:j),"(Z1)") istr
|
||
|
|
do jj=1, 4
|
||
|
|
icol=(j-1)*4+jj
|
||
|
|
if( btest(istr,4-jj) ) gen(i,icol)=1
|
||
|
|
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 encode204
|