WSJT-X/lib/fsk4hf/ldpcsim174.f90
Bill Somerville dd1362b69a Rationalize NA contest mode
Generic message packing and unpacking routines now understand antipode
grid contest messages.  These messages  are now recognized as standard
messages in  message response processing and  dealt with appropriately
when contest mode is selected and applicable (currently FT8 and MSK144
only).

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@8062 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-09-01 20:10:35 +00:00

239 lines
7.0 KiB
Fortran

program ldpcsim174
! End to end test of the (174,75)/crc12 encoder and decoder.
use crc
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(11)
integer*1 msgbits(87)
integer*1 apmask(174), cw(174)
integer*2 checksum
integer*4 i4Msg6BitWords(13)
integer colorder(174)
integer nerrtot(174),nerrdec(174),nmpcbad(87)
logical checksumok,fsk,bpsk
real*8, allocatable :: rxdata(:)
real, allocatable :: llr(:)
data colorder/ &
0, 1, 2, 3, 30, 4, 5, 6, 7, 8, 9, 10, 11, 32, 12, 40, 13, 14, 15, 16,&
17, 18, 37, 45, 29, 19, 20, 21, 41, 22, 42, 31, 33, 34, 44, 35, 47, 51, 50, 43,&
36, 52, 63, 46, 25, 55, 27, 24, 23, 53, 39, 49, 59, 38, 48, 61, 60, 57, 28, 62,&
56, 58, 65, 66, 26, 70, 64, 69, 68, 67, 74, 71, 54, 76, 72, 75, 78, 77, 80, 79,&
73, 83, 84, 81, 82, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99,&
100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,&
120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,&
140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,&
160,161,162,163,164,165,166,167,168,169,170,171,172,173/
do i=1,NRECENT
recent_calls(i)=' '
enddo
nerrtot=0
nerrdec=0
nmpcbad=0 ! Used to collect the number of errors in the message+crc part of the codeword
nargs=iargc()
if(nargs.ne.4) then
print*,'Usage: ldpcsim niter ndepth #trials s '
print*,'eg: ldpcsim 10 2 1000 0.84'
print*,'belief propagation iterations: niter, ordered-statistics depth: ndepth'
print*,'If s is negative, then value is ignored and sigma is calculated from SNR.'
return
endif
call getarg(1,arg)
read(arg,*) max_iterations
call getarg(2,arg)
read(arg,*) ndepth
call getarg(3,arg)
read(arg,*) ntrials
call getarg(4,arg)
read(arg,*) s
fsk=.false.
bpsk=.true.
! don't count crc bits as data bits
N=174
K=87
! scale Eb/No for a (174,87) code
rate=real(K)/real(N)
write(*,*) "rate: ",rate
write(*,*) "niter= ",max_iterations," s= ",s
allocate ( codeword(N), decoded(K), message(K) )
allocate ( rxdata(N), llr(N) )
msg="K1JT K9AN EN50"
! msg="G4WJS K9AN 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
i1Msg8BitBytes(10:11)=0
checksum = crc12 (c_loc (i1Msg8BitBytes), 11)
! For reference, the next 3 lines show how to check the CRC
i1Msg8BitBytes(10)=checksum/256
i1Msg8BitBytes(11)=iand (checksum,255)
checksumok = crc12_check(c_loc (i1Msg8BitBytes), 11)
if( checksumok ) write(*,*) 'Good checksum'
! K=87, For now:
! msgbits(1:72) JT message bits
! msgbits(73:75) 3 free message bits (set to 0)
! msgbits(76:87) CRC12
mbit=0
do i=1, 9
i1=i1Msg8BitBytes(i)
do ibit=1,8
mbit=mbit+1
msgbits(mbit)=iand(1,ishft(i1,ibit-8))
enddo
enddo
msgbits(73:75)=0 ! the three extra message bits go here
i1=i1Msg8BitBytes(10) ! First 4 bits of crc12 are LSB of this byte
do ibit=1,4
msgbits(75+ibit)=iand(1,ishft(i1,ibit-4))
enddo
i1=i1Msg8BitBytes(11) ! Now shift in last 8 bits of the CRC
do ibit=1,8
msgbits(79+ibit)=iand(1,ishft(i1,ibit-8))
enddo
write(*,*) 'message'
write(*,'(11(8i1,1x))') msgbits
call encode174(msgbits,codeword)
call init_random_seed()
! call sgran()
write(*,*) 'codeword'
write(*,'(22(8i1,1x))') codeword
write(*,*) "Es/N0 SNR2500 ngood nundetected nbadcrc sigma"
do idb = 20,-10,-1
!do idb = -3,-3,-1
db=idb/2.0-1.0
sigma=1/sqrt( 2*(10**(db/10.0)) )
ngood=0
nue=0
nbadcrc=0
nberr=0
do itrial=1, ntrials
! Create a realization of a noisy received word
do i=1,N
if( bpsk ) then
rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
elseif( fsk ) then
if( codeword(i) .eq. 1 ) then
r1=(1.0 + sigma*gran())**2 + (sigma*gran())**2
r2=(sigma*gran())**2 + (sigma*gran())**2
elseif( codeword(i) .eq. 0 ) then
r2=(1.0 + sigma*gran())**2 + (sigma*gran())**2
r1=(sigma*gran())**2 + (sigma*gran())**2
endif
! rxdata(i)=0.35*(sqrt(r1)-sqrt(r2))
! rxdata(i)=0.35*(exp(r1)-exp(r2))
rxdata(i)=0.12*(log(r1)-log(r2))
endif
enddo
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
nberr=nberr+nerr
! 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)
nap=0 ! number of AP bits
llr(colorder(174-87+1:174-87+nap)+1)=5*(2.0*msgbits(1:nap)-1.0)
apmask=0
apmask(colorder(174-87+1:174-87+nap)+1)=1
! max_iterations is max number of belief propagation iterations
call bpdecode174(llr, apmask, max_iterations, decoded, cw, nharderrors,niterations)
if( ndepth .ge. 0 .and. nharderrors .lt. 0 ) call osd174(llr, apmask, ndepth, decoded, cw, nharderrors, dmin)
! If the decoder finds a valid codeword, nharderrors will be .ge. 0.
if( nharderrors .ge. 0 ) then
call extractmessage174(decoded,msgreceived,ncrcflag,recent_calls,nrecent)
if( ncrcflag .ne. 1 ) then
nbadcrc=nbadcrc+1
endif
nueflag=0
nerrmpc=0
do i=1,K ! find number of errors in message+crc part of codeword
if( msgbits(i) .ne. decoded(i) ) then
nueflag=1
nerrmpc=nerrmpc+1
endif
enddo
nmpcbad(nerrmpc)=nmpcbad(nerrmpc)+1
if( ncrcflag .eq. 1 ) then
if( nueflag .eq. 0 ) then
ngood=ngood+1
nerrdec(nerr)=nerrdec(nerr)+1
else if( nueflag .eq. 1 ) then
nue=nue+1;
endif
endif
endif
enddo
baud=12000/1920
snr2500=db+10.0*log10((baud/2500.0))
pberr=real(nberr)/(real(ntrials*N))
write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,1x,i8,8x,f5.2,8x,e10.3)") db,snr2500,ngood,nue,nbadcrc,ss,pberr
enddo
open(unit=23,file='nerrhisto.dat',status='unknown')
do i=1,174
write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10)
enddo
close(23)
open(unit=25,file='nmpcbad.dat',status='unknown')
do i=1,87
write(25,'(i4,2x,i10)') i,nmpcbad(i)
enddo
close(25)
end program ldpcsim174