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https://github.com/saitohirga/WSJT-X.git
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374282920c
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6711 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
256 lines
6.8 KiB
Fortran
256 lines
6.8 KiB
Fortran
subroutine syncmsk144(cdat,npts,jpk,ipk,idf,rmax,snr,metric,msgreceived,fest)
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! Attempt synchronization, and if successful decode using Viterbi algorithm.
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use iso_c_binding, only: c_loc,c_size_t
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use packjt
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use hashing
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use timer_module, only: timer
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parameter (NSPM=864,NSAVE=2000)
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character*22 msgreceived
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character*85 pchk_file,gen_file
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complex cdat(npts) !Analytic signal
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complex c(NSPM)
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complex ctmp(6000)
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complex cb(42) !Complex waveform for sync word
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complex csum,cfac,cca,ccb
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complex cc(npts)
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complex cc1(npts)
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complex cc2(npts)
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complex cc3(npts)
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integer s8(8),hardbits(144),hardword(128),unscrambledhardbits(128)
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integer*1, target:: i1Dec8BitBytes(10)
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integer, dimension(1) :: iloc
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integer*4 i4Msg6BitWords(12) !72-bit message as 6-bit words
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integer*4 i4Dec6BitWords(12)
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integer*1 decoded(80)
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integer*1, allocatable :: message(:)
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integer*1 i1hashdec
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logical ismask(6000)
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real cbi(42),cbq(42)
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real tonespec(6000)
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real rcw(12)
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real dd(npts)
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real pp(12) !Half-sine pulse shape
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real*8 dt, df, fs, twopi
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real softbits(144)
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real*8 unscrambledsoftbits(128)
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real lratio(128)
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logical first
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data first/.true./
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data s8/0,1,1,1,0,0,1,0/
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save first,cb,cd,pi,twopi,dt,f0,f1
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if(first) then
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print*,"Initializing ldpc."
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pchk_file="peg-128-80-reg3.pchk"
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gen_file="peg-128-80-reg3.gen"
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call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
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! define half-sine pulse and raised-cosine edge window
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pi=4d0*datan(1d0)
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twopi=8d0*datan(1d0)
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dt=1.0/12000.0
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do i=1,12
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angle=(i-1)*pi/12.0
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pp(i)=sin(angle)
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rcw(i)=(1-cos(angle))/2
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enddo
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! define the sync word waveform
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s8=2*s8-1
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cbq(1:6)=pp(7:12)*s8(1)
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cbq(7:18)=pp*s8(3)
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cbq(19:30)=pp*s8(5)
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cbq(31:42)=pp*s8(7)
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cbi(1:12)=pp*s8(2)
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cbi(13:24)=pp*s8(4)
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cbi(25:36)=pp*s8(6)
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cbi(37:42)=pp(1:6)*s8(8)
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cb=cmplx(cbi,cbq)
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! print*,"cb"
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! do i=1,42
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! print*,i,cbi(i),cbq(i)
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! enddo
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first=.false.
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endif
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! Coarse carrier frequency sync
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! look for tones near 2k and 4k in the analytic signal spectrum
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! search range for coarse frequency error is +/- 100 Hz
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fs=12000.0
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nfft=6000 !using a zero-padded fft to get 2 Hz bins
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df=fs/nfft
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ctmp=cmplx(0.0,0.0)
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ctmp(1:npts)=cdat**2
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ctmp(1:12)=ctmp(1:12)*rcw
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ctmp(npts-11:npts)=ctmp(npts-11:npts)*rcw(12:1:-1)
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call four2a(ctmp,nfft,1,-1,1)
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tonespec=abs(ctmp)**2
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ismask=.false.
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ismask(1901:2101)=.true. ! high tone search window
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iloc=maxloc(tonespec,ismask)
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ihpk=iloc(1)
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ah=tonespec(ihpk)
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ismask=.false.
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ismask(901:1101)=.true. ! window for low tone
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iloc=maxloc(tonespec,ismask)
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ilpk=iloc(1)
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al=tonespec(ilpk)
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if( ah .ge. al ) then
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ferr=(ihpk-2001)*df/2.0
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tot=sum(tonespec(1901:2101))
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q1=200*ah/(tot-tonespec(ihpk))
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else
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ferr=(ilpk-1001)*df/2.0
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tot=sum(tonespec(901:1101))
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q1=200*al/(tot-tonespec(ilpk))
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endif
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fdiff=(ihpk-ilpk)*df
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write(*,*) "Coarse frequency error: ",ferr
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write(*,*) "Tone / avg : ",q1
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write(*,*) "Tone separation : ",fdiff
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! remove coarse freq error - should now be within a few Hz
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call tweak1(cdat,npts,-(1500+ferr),cdat)
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! correlate with sync word waveform
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cc=0
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cc1=0
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cc2=0
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cc3=0
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do i=1,npts-448-41
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cc1(i)=sum(cdat(i:i+41)*conjg(cb))
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cc2(i)=sum(cdat(i+56*6:i+56*6+41)*conjg(cb))
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enddo
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cc=cc1+cc2
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dd=abs(cc1)*abs(cc2)
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iloc=maxloc(abs(cc))
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ic1=iloc(1)
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iloc=maxloc(dd)
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ic2=iloc(1)
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write(*,*) "Syncs: ic1,ic2 ",ic1,ic2
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ic=ic2
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! open(unit=78,file="blah.txt")
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! do i=1,npts-448-41
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! write(78,*) i,abs(cc1(i)),abs(cc2(i)),abs(cc(i)),dd(i),abs(cc3(i))
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! enddo
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! close(78)
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cca=sum(cdat(ic:ic+41)*conjg(cb))
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ccb=sum(cdat(ic+56*6:ic+56*6+41)*conjg(cb))
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phase0=atan2(imag(cca+ccb),real(cca+ccb))
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cfac=ccb*conjg(cca)
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ferr2=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt)
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write(*,*) "Fine frequency error: ",ferr2
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write(*,*) "Coarse Carrier phase : ",phase0
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fest=1500+ferr+ferr2
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write(*,*) "Estimated f0 : ",fest
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! Remove fine frequency error
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call tweak1(cdat,npts,-ferr2,cdat)
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! Estimate final carrier phase
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cca=sum(cdat(ic:ic+41)*conjg(cb))
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ccb=sum(cdat(ic+56*6:ic+56*6+41)*conjg(cb))
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cfac=ccb*conjg(cca)
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ffin=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt)
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phase0=atan2(imag(cca+ccb),real(cca+ccb))
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write(*,*) "Final freq error: ",ffin
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cfac=cmplx(cos(phase0),sin(phase0))
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cdat=cdat*conjg(cfac)
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open(unit=79,file="cdat.txt")
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write(*,*) "npts = ",npts
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do i=1,864
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ii=ic+i-1
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if( ii .gt. npts ) then
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ii=ii-864
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endif
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c(i)=cdat(ii)
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write(79,*) i,real(c(i)),imag(c(i))
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enddo
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close(79)
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do i=1,72
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softbits(2*i-1)=imag(c(1+(i-1)*12))
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softbits(2*i)=real(c(7+(i-1)*12))
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enddo
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hardbits=0
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do i=1,144
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if( softbits(i) .ge. 0.0 ) then
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hardbits(i)=1
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endif
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enddo
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! write(*,*) hardbits(1:8)
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! write(*,*) hardbits(57:57+7)
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hardword(1:48)=hardbits(9:9+47)
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hardword(49:128)=hardbits(65:65+80-1)
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unscrambledhardbits(1:127:2)=hardword(1:64)
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unscrambledhardbits(2:128:2)=hardword(65:128)
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sav=sum(softbits)/144
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s2av=sum(softbits*softbits)/144
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ssig=sqrt(s2av-sav*sav)
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softbits=softbits/ssig
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sigma=0.65
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lratio(1:48)=softbits(9:9+47)
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lratio(49:128)=softbits(65:65+80-1)
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lratio=exp(2.0*lratio/(sigma*sigma))
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unscrambledsoftbits(1:127:2)=lratio(1:64)
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unscrambledsoftbits(2:128:2)=lratio(65:128)
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max_iterations=20
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max_dither=100
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call ldpc_decode(unscrambledsoftbits, decoded, max_iterations, niterations, max_dither, ndither)
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write(*,*) 'Decoder used ',niterations,' and ',ndither,' dither trials.'
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if( niterations .lt. 0 ) then
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msgreceived=' '
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return
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endif
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! The decoder found a codeword - compare decoded hash with calculated
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! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash
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do ibyte=1,10
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itmp=0
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do ibit=1,8
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itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*8+ibit))
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enddo
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i1Dec8BitBytes(ibyte)=itmp
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enddo
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! Calculate the hash using the first 9 bytes.
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ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
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ihashdec=2*iand(ihashdec,255)
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! Compare calculated hash with received byte 10 - if they agree, keep the message.
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i1hashdec=ihashdec
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write(*,*) "Hashes",i1hashdec,i1Dec8BitBytes(10)
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if( i1hashdec .eq. i1Dec8BitBytes(10) ) then
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! Good hash --- unpack 72-bit message
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do ibyte=1,12
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itmp=0
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do ibit=1,6
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itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
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enddo
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i4Dec6BitWords(ibyte)=itmp
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enddo
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call unpackmsg(i4Dec6BitWords,msgreceived)
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endif
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return
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end subroutine syncmsk144
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