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https://github.com/saitohirga/WSJT-X.git
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143 lines
3.6 KiB
Fortran
143 lines
3.6 KiB
Fortran
program ldpcsim128_90
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! Simulate the performance of the (128,90) code that is used in
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! the second incarnation of MSK144.
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use packjt77
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integer, parameter:: N=128, K=90, M=N-K
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! character*12 recent_calls(NRECENT)
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character*37 msg,msgsent,msgreceived
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character*77 c77
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character*8 arg
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integer*1 codeword(N), message77(77)
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integer*1 apmask(N),cw(N)
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integer*1 msgbits(77)
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integer*4 i4Msg6BitWords(13)
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integer nerrtot(0:N),nerrdec(0:N)
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logical unpk77_success
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real*8 rxdata(N), rxavgd(N)
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real llr(N),llra(N)
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do i=1,MAXNRECENT
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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.5) then
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print*,'Usage: ldpcsim niter ndeep navg #trials s '
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print*,'eg: ldpcsim 10 2 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,*) ndeep
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call getarg(3,arg)
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read(arg,*) navg
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call getarg(4,arg)
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read(arg,*) ntrials
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call getarg(5,arg)
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read(arg,*) s
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rate=real(77)/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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msg="K1ABC RR73; W9XYZ <KH1/KH7Z> -12"
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i3=0
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n3=1
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call pack77(msg,i3,n3,c77)
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call unpack77(c77,0,msgsent,unpk77_success)
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read(c77,'(77i1)') msgbits
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write(*,*) "message sent ",msgsent
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write(*,*) 'msgbits'
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write(*,'(77i1)') msgbits
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! msgbits is the 77-bit message, codeword is 128 bits
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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 sigma psymerr"
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do idb = 6,6,-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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nsumerr=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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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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! 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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apmask=0
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! max_iterations is max number of belief propagation iterations
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call bpdecode128_90(llr, apmask, max_iterations, message77, cw, nharderrors, niterations)
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if(ndeep.ge.0 .and. nharderrors.lt.0) then
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call osd128_90(llr, apmask, ndeep, message77, cw, nharderrors, dmin)
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endif
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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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write(c77,'(77i1)') message77
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call unpack77(c77,1,msgreceived,unpk77_success)
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nhw=count(cw.ne.codeword)
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if(nhw.eq.0) then ! this is a good decode
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ngood=ngood+1
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nerrdec(nerr)=nerrdec(nerr)+1
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else ! this is an undetected error
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nue=nue+1
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endif
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endif
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nsumerr=nsumerr+nerr
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enddo
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snr2500=db+10*log10(rate*2000.0/2500.0) ! symbol rate is 2000 s^-1 and ref BW is 2500 Hz.
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pberr=real(nsumerr)/real(ntrials*N)
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write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,7x,f5.2,3x,e10.3)") db,snr2500,ngood,nue,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=0,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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end program ldpcsim128_90
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