mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-12-24 11:40:31 -05:00
1022a55665
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@8437 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
176 lines
4.5 KiB
Fortran
176 lines
4.5 KiB
Fortran
program ldpcsim
|
|
|
|
use, intrinsic :: iso_c_binding
|
|
use iso_c_binding, only: c_loc,c_size_t
|
|
use hashing
|
|
use packjt
|
|
parameter(NRECENT=10)
|
|
character*12 recent_calls(NRECENT)
|
|
character*22 msg,msgsent,msgreceived
|
|
character*8 arg
|
|
integer*1, allocatable :: codeword(:), decoded(:), message(:)
|
|
integer*1, target:: i1Msg8BitBytes(10)
|
|
integer*1 i1hash(4)
|
|
integer*1 msgbits(80)
|
|
integer*4 i4Msg6BitWords(13)
|
|
integer ihash
|
|
integer nerrtot(128),nerrdec(128)
|
|
real*8, allocatable :: lratio(:), rxdata(:), rxavgd(:)
|
|
real, allocatable :: yy(:), llr(:)
|
|
equivalence(ihash,i1hash)
|
|
|
|
do i=1,NRECENT
|
|
recent_calls(i)=' '
|
|
enddo
|
|
nerrtot=0
|
|
nerrdec=0
|
|
|
|
nargs=iargc()
|
|
if(nargs.ne.4) then
|
|
print*,'Usage: ldpcsim niter navg #trials s '
|
|
print*,'eg: ldpcsim 10 1 1000 0.75'
|
|
return
|
|
endif
|
|
call getarg(1,arg)
|
|
read(arg,*) max_iterations
|
|
call getarg(2,arg)
|
|
read(arg,*) navg
|
|
call getarg(3,arg)
|
|
read(arg,*) ntrials
|
|
call getarg(4,arg)
|
|
read(arg,*) s
|
|
|
|
! don't count hash bits as data bits
|
|
N=128
|
|
K=72
|
|
rate=real(K)/real(N)
|
|
|
|
write(*,*) "rate: ",rate
|
|
|
|
write(*,*) "niter= ",max_iterations," navg= ",navg," s= ",s
|
|
|
|
allocate ( codeword(N), decoded(K), message(K) )
|
|
allocate ( lratio(N), rxdata(N), rxavgd(N), yy(N), llr(N) )
|
|
|
|
msg="K9AN K1JT EN50"
|
|
call packmsg(msg,i4Msg6BitWords,itype,.false.) !Pack into 12 6-bit bytes
|
|
call unpackmsg(i4Msg6BitWords,msgsent,.false.,' ') !Unpack to get msgsent
|
|
write(*,*) "message sent ",msgsent
|
|
|
|
i4=0
|
|
ik=0
|
|
im=0
|
|
do i=1,12
|
|
nn=i4Msg6BitWords(i)
|
|
do j=1, 6
|
|
ik=ik+1
|
|
i4=i4+i4+iand(1,ishft(nn,j-6))
|
|
i4=iand(i4,255)
|
|
if(ik.eq.8) then
|
|
im=im+1
|
|
! if(i4.gt.127) i4=i4-256
|
|
i1Msg8BitBytes(im)=i4
|
|
ik=0
|
|
endif
|
|
enddo
|
|
enddo
|
|
|
|
ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146)
|
|
ihash=2*iand(ihash,32767) !Generate the 8-bit hash
|
|
i1Msg8BitBytes(10)=i1hash(1) !Hash code to byte 10
|
|
mbit=0
|
|
do i=1, 10
|
|
i1=i1Msg8BitBytes(i)
|
|
do ibit=1,8
|
|
mbit=mbit+1
|
|
msgbits(mbit)=iand(1,ishft(i1,ibit-8))
|
|
enddo
|
|
enddo
|
|
call encode_msk144(msgbits,codeword)
|
|
call init_random_seed()
|
|
|
|
write(*,*) "Eb/N0 SNR2500 ngood nundetected nbadhash sigma"
|
|
do idb = -6, 14
|
|
db=idb/2.0-1.0
|
|
sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
|
|
ngood=0
|
|
nue=0
|
|
nbadhash=0
|
|
|
|
do itrial=1, ntrials
|
|
rxavgd=0d0
|
|
do iav=1,navg
|
|
call sgran()
|
|
! Create a realization of a noisy received word
|
|
do i=1,N
|
|
rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
|
|
enddo
|
|
rxavgd=rxavgd+rxdata
|
|
enddo
|
|
rxdata=rxavgd
|
|
nerr=0
|
|
do i=1,N
|
|
if( rxdata(i)*(2*codeword(i)-1.0) .lt. 0 ) nerr=nerr+1
|
|
enddo
|
|
nerrtot(nerr)=nerrtot(nerr)+1
|
|
|
|
! Correct signal normalization is important for this decoder.
|
|
rxav=sum(rxdata)/N
|
|
rx2av=sum(rxdata*rxdata)/N
|
|
rxsig=sqrt(rx2av-rxav*rxav)
|
|
rxdata=rxdata/rxsig
|
|
! To match the metric to the channel, s should be set to the noise standard deviation.
|
|
! For now, set s to the value that optimizes decode probability near threshold.
|
|
! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
|
|
! magnitude in UER
|
|
if( s .lt. 0 ) then
|
|
ss=sigma
|
|
else
|
|
ss=s
|
|
endif
|
|
|
|
llr=2.0*rxdata/(ss*ss)
|
|
lratio=exp(llr)
|
|
yy=rxdata
|
|
|
|
! max_iterations is max number of belief propagation iterations
|
|
! call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
|
|
! call amsdecode(yy, max_iterations, decoded, niterations)
|
|
! call bitflipmsk144(rxdata, decoded, niterations)
|
|
call bpdecode144(llr, max_iterations, decoded, niterations)
|
|
|
|
! If the decoder finds a valid codeword, niterations will be .ge. 0.
|
|
if( niterations .ge. 0 ) then
|
|
call extractmessage144(decoded,msgreceived,nhashflag,recent_calls,nrecent)
|
|
if( nhashflag .ne. 1 ) then
|
|
nbadhash=nbadhash+1
|
|
endif
|
|
nueflag=0
|
|
|
|
! Check the message plus hash against what was sent.
|
|
do i=1,K
|
|
if( msgbits(i) .ne. decoded(i) ) then
|
|
nueflag=1
|
|
endif
|
|
enddo
|
|
if( nhashflag .eq. 1 .and. nueflag .eq. 0 ) then
|
|
ngood=ngood+1
|
|
nerrdec(nerr)=nerrdec(nerr)+1
|
|
else if( nhashflag .eq. 1 .and. nueflag .eq. 1 ) then
|
|
nue=nue+1;
|
|
endif
|
|
endif
|
|
enddo
|
|
snr2500=db-3.5
|
|
write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,1x,i8,8x,f5.2)") db,snr2500,ngood,nue,nbadhash,ss
|
|
|
|
enddo
|
|
|
|
open(unit=23,file='nerrhisto.dat',status='unknown')
|
|
do i=1,128
|
|
write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10)
|
|
enddo
|
|
close(23)
|
|
|
|
end program ldpcsim
|