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https://github.com/saitohirga/WSJT-X.git
synced 2024-11-18 18:12:12 -05:00
dd1362b69a
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
176 lines
4.5 KiB
Fortran
176 lines
4.5 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 hashing
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use packjt
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parameter(NRECENT=10)
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character*12 recent_calls(NRECENT)
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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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integer*1, target:: i1Msg8BitBytes(10)
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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(128),nerrdec(128)
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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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N=128
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K=72
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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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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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ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146)
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ihash=2*iand(ihash,32767) !Generate the 8-bit hash
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i1Msg8BitBytes(10)=i1hash(1) !CRC to byte 10
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mbit=0
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do i=1, 10
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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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call encode_msk144(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 ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
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! call amsdecode(yy, max_iterations, decoded, niterations)
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! call bitflipmsk144(rxdata, decoded, niterations)
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call bpdecode144(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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call extractmessage144(decoded,msgreceived,nhashflag,recent_calls,nrecent)
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if( nhashflag .ne. 1 ) then
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nbadhash=nbadhash+1
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endif
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nueflag=0
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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( msgbits(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. 1 .and. nueflag .eq. 0 ) then
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ngood=ngood+1
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nerrdec(nerr)=nerrdec(nerr)+1
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else if( nhashflag .eq. 1 .and. 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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write(*,"(f4.1,4x,f5.1,1x,i8,1x,i8,1x,i8,8x,f5.2)") db,snr2500,ngood,nue,nbadhash,ss
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enddo
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open(unit=23,file='nerrhisto.dat',status='unknown')
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do i=1,128
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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 ldpcsim
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