mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-05 00:41:19 -05:00
60 lines
1.3 KiB
Fortran
60 lines
1.3 KiB
Fortran
subroutine bitflip128_90(llr,message77,cw,nharderror)
|
|
!
|
|
! A hard-decision bit flipping decoder for the (128,90) code.
|
|
!
|
|
|
|
use iso_c_binding, only: c_loc,c_size_t
|
|
use crc
|
|
integer, parameter:: N=128, K=90, M=N-K
|
|
integer*1 cw(N),apmask(N)
|
|
integer*1 decoded(K)
|
|
integer*1 message77(77)
|
|
integer Nm(11,M)
|
|
integer Mn(3,N)
|
|
integer nrw(M)
|
|
integer synd(M)
|
|
integer nuns(N)
|
|
real zn(N)
|
|
real llr(N)
|
|
|
|
include "ldpc_128_90_reordered_parity.f90"
|
|
|
|
decoded=0
|
|
zn=llr
|
|
|
|
do iter=0,0
|
|
|
|
! Check to see if we have a codeword (check before we do any iteration).
|
|
cw=0
|
|
where( zn .gt. 0. ) cw=1
|
|
ncheck=0
|
|
nuns=0
|
|
do i=1,M
|
|
synd(i)=sum(cw(Nm(1:nrw(i),i)))
|
|
if( mod(synd(i),2) .ne. 0 ) then
|
|
ncheck=ncheck+1
|
|
do j=1,nrw(i)
|
|
nuns(Nm(j,i))=nuns(Nm(j,i))+1
|
|
enddo
|
|
endif
|
|
enddo
|
|
if( ncheck .eq. 0 ) then ! we have a codeword - reorder the columns and return it
|
|
decoded=cw(1:K)
|
|
call chkcrc13a(decoded,nbadcrc)
|
|
if(nbadcrc.eq.0) then
|
|
message77=decoded(1:77)
|
|
nharderror=count( (2*cw-1)*llr .lt. 0.0 )
|
|
return
|
|
endif
|
|
endif
|
|
! flip the sign on the symbols that show up in the largest number
|
|
! of un-satisfied parity checks
|
|
where( nuns .eq. maxval(nuns) ) zn=-zn
|
|
|
|
enddo
|
|
llr=zn
|
|
nharderror=-1
|
|
return
|
|
|
|
end subroutine bitflip128_90
|