mirror of https://github.com/saitohirga/WSJT-X.git
203 lines
5.4 KiB
Fortran
203 lines
5.4 KiB
Fortran
program ldpcsim174_91
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! End to end test of the (174,91)/crc14 encoder and decoder.
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use crc
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use packjt
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integer, parameter:: N=174, K=91, M=N-K
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character*22 msg,msgsent,msgreceived
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character*8 arg
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character*6 grid
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integer*1, allocatable :: codeword(:), decoded(:), message(:)
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integer*1, target:: i1Msg8BitBytes(12)
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integer*1 msgbits(K)
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integer*1 apmask(N), cw(N)
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integer*2 checksum
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integer*4 i4Msg6BitWords(13)
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integer colorder(N)
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integer nerrtot(N),nerrdec(N),nmpcbad(K)
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logical checksumok
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real*8, allocatable :: rxdata(:)
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real, allocatable :: llr(:)
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include "ldpc_174_91_c_colorder.f90"
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nerrtot=0
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nerrdec=0
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nmpcbad=0 ! Used to collect the number of errors in the message+crc part of the codeword
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nargs=iargc()
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if(nargs.ne.4) then
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print*,'Usage: ldpcsim niter ndepth #trials s '
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print*,'eg: ldpcsim 10 2 1000 0.84'
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print*,'belief propagation iterations: niter, ordered-statistics depth: ndepth'
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print*,'If s is negative, then value is ignored and sigma is calculated from SNR.'
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return
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endif
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call getarg(1,arg)
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read(arg,*) max_iterations
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call getarg(2,arg)
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read(arg,*) ndepth
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call getarg(3,arg)
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read(arg,*) ntrials
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call getarg(4,arg)
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read(arg,*) s
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! scale Eb/No for a (174,91) code
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rate=real(K)/real(N)
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write(*,*) "rate: ",rate
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write(*,*) "niter= ",max_iterations," s= ",s
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allocate ( codeword(N), decoded(K), message(K) )
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allocate ( rxdata(N), llr(N) )
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msg="K1JT K9AN EN50"
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! msg="G4WJS K9AN EN50"
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call packmsg(msg,i4Msg6BitWords,itype,.false.) !Pack into 12 6-bit bytes
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call unpackmsg(i4Msg6BitWords,msgsent,.false.,grid) !Unpack to get msgsent
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write(*,*) "message sent ",msgsent
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i4=0
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ik=0
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im=0
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do i=1,12
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nn=i4Msg6BitWords(i)
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do j=1, 6
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ik=ik+1
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i4=i4+i4+iand(1,ishft(nn,j-6))
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i4=iand(i4,255)
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if(ik.eq.8) then
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im=im+1
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! if(i4.gt.127) i4=i4-256
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i1Msg8BitBytes(im)=i4
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ik=0
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endif
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enddo
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enddo
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i1Msg8BitBytes(10:12)=0
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checksum = crc14 (c_loc (i1Msg8BitBytes), 12)
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! For reference, the next 3 lines show how to check the CRC
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i1Msg8BitBytes(11)=checksum/256
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i1Msg8BitBytes(12)=iand (checksum,255)
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checksumok = crc14_check(c_loc (i1Msg8BitBytes), 12)
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if( checksumok ) write(*,*) 'Good checksum'
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! K=91, For now:
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! msgbits(1:72) JT message bits
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! msgbits(73:77) 5 free message bits (set to 0)
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! msgbits(78:91) CRC14
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mbit=0
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do i=1, 9
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i1=i1Msg8BitBytes(i)
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do ibit=1,8
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mbit=mbit+1
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msgbits(mbit)=iand(1,ishft(i1,ibit-8))
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enddo
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enddo
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msgbits(73:77)=0 ! the five extra message bits go here
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i1=i1Msg8BitBytes(11) ! First 6 bits of crc12 are LSB of this byte
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do ibit=1,6
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msgbits(77+ibit)=iand(1,ishft(i1,ibit-6))
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enddo
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i1=i1Msg8BitBytes(12) ! Now shift in last 8 bits of the CRC
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do ibit=1,8
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msgbits(83+ibit)=iand(1,ishft(i1,ibit-8))
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enddo
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write(*,*) 'message'
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write(*,'(12(8i1,1x))') msgbits
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call encode174_91(msgbits,codeword)
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call init_random_seed()
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! call sgran()
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write(*,*) 'codeword'
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write(*,'(22(8i1,1x))') codeword
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write(*,*) "Eb/N0 SNR2500 ngood nundetected nbadcrc sigma"
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do idb = 20,-10,-1
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!do idb = 0,0,-1
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db=idb/2.0-1.0
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sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
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ngood=0
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nue=0
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nbadcrc=0
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nberr=0
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do itrial=1, ntrials
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! Create a realization of a noisy received word
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do i=1,N
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rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
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enddo
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nerr=0
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do i=1,N
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if( rxdata(i)*(2*codeword(i)-1.0) .lt. 0 ) nerr=nerr+1
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enddo
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if(nerr.ge.1) nerrtot(nerr)=nerrtot(nerr)+1
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nberr=nberr+nerr
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rxav=sum(rxdata)/N
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rx2av=sum(rxdata*rxdata)/N
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rxsig=sqrt(rx2av-rxav*rxav)
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rxdata=rxdata/rxsig
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if( s .lt. 0 ) then
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ss=sigma
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else
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ss=s
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endif
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llr=2.0*rxdata/(ss*ss)
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nap=0 ! number of AP bits
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llr(colorder(174-91+1:174-91+nap)+1)=5*(2.0*msgbits(1:nap)-1.0)
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apmask=0
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apmask(colorder(174-91+1:174-91+nap)+1)=1
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! max_iterations is max number of belief propagation iterations
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call bpdecode174_91(llr, apmask, max_iterations, decoded, cw, nharderrors,niterations)
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if( ndepth .ge. 0 .and. nharderrors .lt. 0 ) call osd174_91(llr, apmask, ndepth, decoded, cw, nharderrors, dmin)
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! If the decoder finds a valid codeword, nharderrors will be .ge. 0.
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if( nharderrors .ge. 0 ) then
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call extractmessage174_91(decoded,msgreceived,ncrcflag)
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if( ncrcflag .ne. 1 ) then
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nbadcrc=nbadcrc+1
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endif
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nueflag=0
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nerrmpc=0
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do i=1,K ! find number of errors in message+crc part of codeword
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if( msgbits(i) .ne. decoded(i) ) then
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nueflag=1
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nerrmpc=nerrmpc+1
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endif
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enddo
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if(nerrmpc.ge.1) nmpcbad(nerrmpc)=nmpcbad(nerrmpc)+1
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if( ncrcflag .eq. 1 ) then
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if( nueflag .eq. 0 ) then
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ngood=ngood+1
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if(nerr.ge.1) nerrdec(nerr)=nerrdec(nerr)+1
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else if( nueflag .eq. 1 ) then
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nue=nue+1;
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endif
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endif
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endif
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enddo
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baud=12000/1920
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snr2500=db+10.0*log10((baud/2500.0))
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pberr=real(nberr)/(real(ntrials*N))
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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
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enddo
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open(unit=23,file='nerrhisto.dat',status='unknown')
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do i=1,174
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write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10)
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enddo
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close(23)
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open(unit=25,file='nmpcbad.dat',status='unknown')
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do i=1,87
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write(25,'(i4,2x,i10)') i,nmpcbad(i)
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enddo
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close(25)
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end program ldpcsim174_91
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