2018-02-08 21:28:33 -05:00
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program ldpcsim
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use, intrinsic :: iso_c_binding
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use hashing
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use packjt
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character*22 msg,msgsent,msgreceived
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character*8 arg
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integer*1, allocatable :: codeword(:), decoded(:), message(:)
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real*8, allocatable :: rxdata(:), rxavgd(:)
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real, allocatable :: llr(:)
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integer ihash
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integer*1 hardbits(32)
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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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K=16
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N=32
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!rate=real(K)/real(N)
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! don't count hash bits as data bits
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rate=4.0/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 ( rxdata(N), rxavgd(N), llr(N) )
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msg="K1JT K9AN"
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call fmtmsg(msg,iz)
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call hash(msg,22,ihash)
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irpt=14
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ihash=iand(ihash,4095) !12-bit hash
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ig=16*ihash + irpt !4-bit report
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write(*,*) irpt,ihash,ig
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do i=1,16
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message(i)=iand(1,ishft(ig,1-i))
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enddo
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write(*,'(16i1)') message
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call encode_msk40(message,codeword)
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write(*,'(32i1)') codeword
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call init_random_seed()
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write(*,*) "Eb/N0 SNR2500 ngood nundetected nbadhash"
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do idb = 0, 30
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db=idb/2.0
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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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itsum=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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! 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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if( s .le. 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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call bpdecode40(llr, max_iterations, decoded, niterations)
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! If the decoder finds a valid codeword, niterations will be .ge. 0.
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if( niterations .ge. 0 ) then
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nueflag=0
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nhashflag=0
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imsg=0
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do i=1,16
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2019-03-21 21:14:23 -04:00
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imsg=ishft(imsg,1)+iand(1_1,decoded(17-i))
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2018-02-08 21:28:33 -05:00
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enddo
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nrxrpt=iand(imsg,15)
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nrxhash=(imsg-nrxrpt)/16
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if( nrxhash .ne. ihash ) then
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nbadhash=nbadhash+1
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nhashflag=1
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endif
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! Check the message plus hash against what was sent.
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do i=1,K
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if( message(i) .ne. decoded(i) ) then
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nueflag=1
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endif
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enddo
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if( nhashflag .eq. 0 .and. nueflag .eq. 0 ) then
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ngood=ngood+1
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itsum=itsum+niterations
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else if( nhashflag .eq. 0 .and. nueflag .eq. 1 ) then
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nue=nue+1;
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endif
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else
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hardbits=0
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where(llr .gt. 0) hardbits=1
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! write(*,'(32i1)') hardbits
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! write(*,'(32i1)') codeword
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isum=0
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do i=1,32
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if( hardbits(i) .ne. codeword(i) ) isum=isum+1
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enddo
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! write(*,*) 'number of errors ',isum
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endif
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enddo
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avits=real(itsum)/real(ngood+0.1)
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snr2500=db-10.0
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write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,1x,i8,1x,f8.2,1x,f8.1)") db,snr2500,ngood,nue,nbadhash,ss,avits
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enddo
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end program ldpcsim
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