WSJT-X/lib/ldpc/msksim.f90

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Fortran
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program msksim
use, intrinsic :: iso_c_binding
parameter (N=128, M=48, K=80) ! M and N are global variables on the C side.
integer(1) message(1:K)
integer(1) codeword(1:N)
integer(1) decoded(1:K)
real*8 lratio(N)
character(50) pchk_file,gen_file
pchk_file="./jtmode_codes/ldpc-128-80-sf13.pchk"
gen_file="./jtmode_codes/ldpc-128-80-sf13.gen"
call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
message(1:40)=1
message(41:80)=0
call ldpc_encode(message,codeword)
max_iterations=10
ntrials=1000000
rate=real(K)/real(N)
write(*,*) "Eb/N0 ngood nundetected"
do idb = 0, 11
db=idb/2.0-0.5
sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
ngood=0
nue=0
do itrial=1, ntrials
do i=1,N
rxdata = 2.0*(codeword(i)-0.5) + sigma*gran()
lratio(i)=exp(2.0*rxdata/(sigma*sigma))
enddo
call ldpc_decode(lratio, decoded, max_iterations, niterations)
if( niterations .ge. 0 ) then
nueflag=0
do i=1,K
if( message(i) .ne. decoded(i) ) then
nueflag=1
endif
enddo
if( nueflag .eq. 1 ) then
nue=nue+1
else
ngood=ngood+1;
endif
endif
enddo
write(*,"(f4.1,1x,i8,1x,i8)") db,ngood,nue
enddo
end program msksim