mirror of https://github.com/saitohirga/WSJT-X.git
170 lines
4.4 KiB
Fortran
170 lines
4.4 KiB
Fortran
program ldpcsim
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use, intrinsic :: iso_c_binding
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use iso_c_binding, only: c_loc,c_size_t
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use crc
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use packjt
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integer, parameter:: NRECENT=10, N=128, K=90, M=N-K
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character*12 recent_calls(NRECENT)
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character*22 msg,msgsent,msgreceived
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character*96 tmpchar
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character*8 arg
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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 i1hash(4)
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integer*1 msgbits(80)
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integer*4 i4Msg6BitWords(13)
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integer ihash
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integer nerrtot(N),nerrdec(N),nmpcbad(K)
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real*8, allocatable :: lratio(:), rxdata(:), rxavgd(:)
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real, allocatable :: yy(:), llr(:)
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equivalence(ihash,i1hash)
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do i=1,NRECENT
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recent_calls(i)=' '
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enddo
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nerrtot=0
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nerrdec=0
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nargs=iargc()
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if(nargs.ne.4) then
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print*,'Usage: ldpcsim niter navg #trials s '
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print*,'eg: ldpcsim 10 1 1000 0.75'
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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,*) navg
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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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! don't count hash bits as data bits
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rate=real(K)/real(N)
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write(*,*) "rate: ",rate
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write(*,*) "niter= ",max_iterations," navg= ",navg," s= ",s
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allocate ( codeword(N), decoded(K), message(K) )
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allocate ( lratio(N), rxdata(N), rxavgd(N), yy(N), llr(N) )
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msg="K9AN K1JT 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.,' ') !Unpack to get msgsent
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write(*,*) "message sent ",msgsent
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tmpchar=' '
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write(tmpchar,'(12b6.6)') i4Msg6BitWords
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tmpchar(73:77)="00000" !i5bit
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write(*,*) tmpchar
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read(tmpchar,'(10b8)') i1Msg8BitBytes(1:10)
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write(*,*) i1Msg8BitBytes
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i1Msg8BitBytes(10:12)=0
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checksum = crc13 (c_loc (i1Msg8ZBitZBytes), 12)
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i1Msg8BitBytes(11)=checksum/256
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i1Msg8BitBytes(12)=iand (checksum,255)
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checksumok = crc13_check(c_loc (i1Msg8ZBitBytes), 12)
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if( checksumok ) write(*,*) 'Good checksum'
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write(tmpchar,'(12b8.8)') i1Msg8BitBytes(1:9)
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read(tmpchar,'(77b)') msgbits(1:77)
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read(tmpchar(84:96),'(6b)') msgbits(78:90)
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call encode_128_90(msgbits,codeword)
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call init_random_seed()
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write(*,*) "Eb/N0 SNR2500 ngood nundetected nbadhash sigma"
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do idb = -6, 14
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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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nbadhash=0
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do itrial=1, ntrials
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rxavgd=0d0
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do iav=1,navg
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call sgran()
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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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rxavgd=rxavgd+rxdata
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enddo
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rxdata=rxavgd
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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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nerrtot(nerr)=nerrtot(nerr)+1
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! Correct signal normalization is important for this decoder.
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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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! To match the metric to the channel, s should be set to the noise standard deviation.
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! For now, set s to the value that optimizes decode probability near threshold.
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! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
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! magnitude in UER
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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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lratio=exp(llr)
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yy=rxdata
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! max_iterations is max number of belief propagation iterations
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call bpdecode128_90(llr, apmask, max_iterations, decoded, cw, nharderrors, niterations)
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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 extractmessage1128_90(decoded,msgreceived,ncrcflag)
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if( nncrcflag .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
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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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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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enddo
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snr2500=db-3.5
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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,N
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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,K
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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 ldpcsim
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