mirror of https://github.com/saitohirga/WSJT-X.git
Improvements to msk144d.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6727 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke
parent
98e2829d41
commit
a87f7270b0
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@ -47,12 +47,13 @@ subroutine msk144_decode(id2,npts,nutc,nprint,line)
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nfft=min(2**n,1024*1024)
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call analytic(d,npts,nfft,c) !Convert to analytic signal and filter
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nafter=NSPM
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nafter=2*NSPM
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nbefore=NSPM
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! Process ping list (sorted by S/N) from top down.
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do n=1,nyel
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ia=ty(n)*12000.0 - NSPM/2
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ia=ty(n)*12000.0 - nbefore
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if(ia.lt.1) ia=1
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ib=ia + 2*nafter-1
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ib=ia + nbefore + nafter - 1
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if(ib.gt.NFFTMAX) ib=NFFTMAX
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iz=ib-ia+1
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cdat2(1:iz)=c(ia:ib) !Select nlen complex samples
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@ -4,10 +4,12 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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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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parameter (NSPM=864)
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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 cdat2(npts) !Analytic signal
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complex cav(NSPM) !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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@ -15,7 +17,7 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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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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complex bb(6)
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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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@ -24,6 +26,7 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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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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integer ipeaks(10)
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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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@ -114,55 +117,103 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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cc=0
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cc1=0
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cc2=0
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do i=1,npts-448-41
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do i=1,npts-(56*6+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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! the goal is for ic to be the index of the first sample of the message
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! This parameter could be dithered
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ic=ic2
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! Estimate fine frequency error and initial carrier phase using
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! difference and sum of sync-word phases. Only frequency error is used.
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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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! Find 5 largest peaks
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do ipk=1,5
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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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ipeaks(ipk)=ic2
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dd(max(1,ic2-7):min(npts-56*6-41,ic2+7))=0.0
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enddo
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! See if we can find "closed brackets" - a pair of peaks that differ by 864, plus or minus
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! This information is not yet used for anything
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do ii=1,5
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do jj=ii+1,5
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if( (ii .ne. jj) .and. (abs( abs(ipeaks(ii)-ipeaks(jj))-864) .le. 5) ) then
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write(78,*) "closed brackets: ",ii,jj,ipeaks(ii),ipeaks(jj),abs(ipeaks(ii)-ipeaks(jj))
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endif
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enddo
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enddo
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do iav=0,1
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do ipk=1,5
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! we want ic to be the index of the first sample of the message
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ic=ipeaks(ipk)
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! This needs to be improved - it's used to protect the edges of the array from
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! overruns.
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if( ic .lt. 12 .or. ic .gt. 2*864-12 ) then
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! write(*,*) "Peak not in central section: ",ipk,is,ic
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cycle
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endif
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! bb is used to place the sampling index at the center of the eye
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do i=1,6
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io=i-3
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bb(i) = sum( ( cdat(ic+io:ic+io+864:6) * conjg( cdat(ic+io+6:ic+io+6+864:6) ) )*2 )
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enddo
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iloc=maxloc(abs(bb))
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ibb=iloc(1)
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! write(*,*) 'ic0: ',ic,'bb peak is at : ',ibb
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! Adjust frame index to place peak of bb at desired lag
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ic=ic + ibb-2
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! Sanity check - recompute bb and verify that peak is now at designated lag.
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! do i=1,6
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! io=i-3
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! bb(i) = sum( ( cdat(ic+io:ic+io+864:6) * conjg( cdat(ic+io+6:ic+io+6+864:6) ) )*2 )
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! enddo
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! iloc=maxloc(abs(bb))
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! ibb=iloc(1)
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! write(*,*) 'ic1: ',ic,'bb peak is at : ',ibb
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! Average two frames on the second pass only if its incredibly easy to do
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! better than nothing. Should be improved.
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c=cdat(ic:ic+864-1)
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if( iav .eq. 1 ) then
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id0=ic+864
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id1=ic+864+863
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if( id1 .le. npts ) then
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c=c+cdat(id0:id1)
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else
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cycle
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endif
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endif
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! Estimate fine frequency error.
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cca=sum(c(1:1+41)*conjg(cb))
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ccb=sum(c(1+56*6:1+56*6+41)*conjg(cb))
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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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! Final estimate of the carrier frequency - returned to the calling program
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fest=1500+ferr+ferr2
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! Remove fine frequency error
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call tweak1(cdat,npts,-ferr2,cdat)
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! Remove fine frequency error and put the results in cdat2
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call tweak1(c,npts,-ferr2,c)
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! Estimate final frequency error and carrier phase using
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! difference and sum of sync-word phases
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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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! Estimate final frequency error and carrier phase.
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cca=sum(c(1:1+41)*conjg(cb))
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ccb=sum(c(1+56*6:1+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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! Remove the static phase error from the data
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cfac=cmplx(cos(phase0),sin(phase0))
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cdat=cdat*conjg(cfac)
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c=c*conjg(cfac)
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! we hope that we are synced. For now we use only the frame
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! that starts at ic
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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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enddo
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! sample to get softsamples
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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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@ -175,14 +226,19 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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enddo
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! calculated the number of sync-word bits that are incorrect
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! this might come in handy some day
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nbadsync=sum(s8*(2*hardbits(1:8)-1))
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nbadsync=nbadsync+sum(s8*(2*hardbits(57:57+7)-1))
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nbadsync=16-nbadsync
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! this could be used to count the number of hard errors that were corrected
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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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! normalize the softsymbols before submitting to decoder
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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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@ -200,11 +256,20 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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max_dither=50
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call ldpc_decode(unscrambledsoftbits, decoded, max_iterations, niterations, max_dither, ndither)
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if( niterations .lt. 0 ) then
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msgreceived=' '
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return
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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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if( niterations .ge. 0.0 ) then
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goto 778
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endif
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enddo
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enddo
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msgreceived=' '
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goto 999
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778 continue
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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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@ -234,7 +299,8 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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call unpackmsg(i4Dec6BitWords,msgreceived)
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endif
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write(78,*) fest,nbadsync,phase0,niterations,ndither,i1hashdec,i1Dec8BitBytes(10),msgreceived
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return
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write(78,1001) iav,ipk,is,fest,nbadsync,phase0,niterations,ndither,i1hashdec,i1Dec8BitBytes(10),msgreceived
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1001 format(i6,i6,i6,f10.1,i6,f10.2,i6,i6,i6,i6,4x,a22)
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999 return
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end subroutine syncmsk144
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