From 23e16b7e117eefdd0462fbcf1d6344ab18c8f220 Mon Sep 17 00:00:00 2001 From: Steven Franke Date: Sun, 5 Jun 2016 01:19:54 +0000 Subject: [PATCH] Improvements to msk144d. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6727 ab8295b8-cf94-4d9e-aec4-7959e3be5d79 --- lib/msk144_decode.f90 | 7 ++- lib/syncmsk144.f90 | 138 +++++++++++++++++++++++++++++++----------- 2 files changed, 106 insertions(+), 39 deletions(-) diff --git a/lib/msk144_decode.f90 b/lib/msk144_decode.f90 index f732ce0de..cf911974e 100644 --- a/lib/msk144_decode.f90 +++ b/lib/msk144_decode.f90 @@ -47,12 +47,13 @@ subroutine msk144_decode(id2,npts,nutc,nprint,line) nfft=min(2**n,1024*1024) call analytic(d,npts,nfft,c) !Convert to analytic signal and filter - nafter=NSPM + nafter=2*NSPM + nbefore=NSPM ! Process ping list (sorted by S/N) from top down. do n=1,nyel - ia=ty(n)*12000.0 - NSPM/2 + ia=ty(n)*12000.0 - nbefore if(ia.lt.1) ia=1 - ib=ia + 2*nafter-1 + ib=ia + nbefore + nafter - 1 if(ib.gt.NFFTMAX) ib=NFFTMAX iz=ib-ia+1 cdat2(1:iz)=c(ia:ib) !Select nlen complex samples diff --git a/lib/syncmsk144.f90 b/lib/syncmsk144.f90 index c98d70d43..c8cf20111 100644 --- a/lib/syncmsk144.f90 +++ b/lib/syncmsk144.f90 @@ -4,10 +4,12 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) use hashing use timer_module, only: timer - parameter (NSPM=864,NSAVE=2000) + parameter (NSPM=864) character*22 msgreceived character*85 pchk_file,gen_file complex cdat(npts) !Analytic signal + complex cdat2(npts) !Analytic signal + complex cav(NSPM) !Analytic signal complex c(NSPM) complex ctmp(6000) complex cb(42) !Complex waveform for sync word @@ -15,7 +17,7 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) complex cc(npts) complex cc1(npts) complex cc2(npts) - complex cc3(npts) + complex bb(6) integer s8(8),hardbits(144),hardword(128),unscrambledhardbits(128) integer*1, target:: i1Dec8BitBytes(10) integer, dimension(1) :: iloc @@ -24,6 +26,7 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) integer*1 decoded(80) integer*1, allocatable :: message(:) integer*1 i1hashdec + integer ipeaks(10) logical ismask(6000) real cbi(42),cbq(42) real tonespec(6000) @@ -114,55 +117,103 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) cc=0 cc1=0 cc2=0 - do i=1,npts-448-41 + do i=1,npts-(56*6+41) cc1(i)=sum(cdat(i:i+41)*conjg(cb)) cc2(i)=sum(cdat(i+56*6:i+56*6+41)*conjg(cb)) enddo cc=cc1+cc2 dd=abs(cc1)*abs(cc2) - iloc=maxloc(abs(cc)) - ic1=iloc(1) - iloc=maxloc(dd) - ic2=iloc(1) -! the goal is for ic to be the index of the first sample of the message -! This parameter could be dithered - ic=ic2 -! Estimate fine frequency error and initial carrier phase using -! difference and sum of sync-word phases. Only frequency error is used. - cca=sum(cdat(ic:ic+41)*conjg(cb)) - ccb=sum(cdat(ic+56*6:ic+56*6+41)*conjg(cb)) - phase0=atan2(imag(cca+ccb),real(cca+ccb)) +! Find 5 largest peaks + do ipk=1,5 + iloc=maxloc(abs(cc)) + ic1=iloc(1) + iloc=maxloc(dd) + ic2=iloc(1) + ipeaks(ipk)=ic2 + dd(max(1,ic2-7):min(npts-56*6-41,ic2+7))=0.0 + enddo + + +! See if we can find "closed brackets" - a pair of peaks that differ by 864, plus or minus +! This information is not yet used for anything + do ii=1,5 + do jj=ii+1,5 + if( (ii .ne. jj) .and. (abs( abs(ipeaks(ii)-ipeaks(jj))-864) .le. 5) ) then + write(78,*) "closed brackets: ",ii,jj,ipeaks(ii),ipeaks(jj),abs(ipeaks(ii)-ipeaks(jj)) + endif + enddo + enddo + + do iav=0,1 + do ipk=1,5 +! we want ic to be the index of the first sample of the message + ic=ipeaks(ipk) + +! This needs to be improved - it's used to protect the edges of the array from +! overruns. + if( ic .lt. 12 .or. ic .gt. 2*864-12 ) then +! write(*,*) "Peak not in central section: ",ipk,is,ic + cycle + endif + +! bb is used to place the sampling index at the center of the eye + do i=1,6 + io=i-3 + bb(i) = sum( ( cdat(ic+io:ic+io+864:6) * conjg( cdat(ic+io+6:ic+io+6+864:6) ) )*2 ) + enddo + iloc=maxloc(abs(bb)) + ibb=iloc(1) +! write(*,*) 'ic0: ',ic,'bb peak is at : ',ibb +! Adjust frame index to place peak of bb at desired lag + ic=ic + ibb-2 + +! Sanity check - recompute bb and verify that peak is now at designated lag. +! do i=1,6 +! io=i-3 +! bb(i) = sum( ( cdat(ic+io:ic+io+864:6) * conjg( cdat(ic+io+6:ic+io+6+864:6) ) )*2 ) +! enddo +! iloc=maxloc(abs(bb)) +! ibb=iloc(1) +! write(*,*) 'ic1: ',ic,'bb peak is at : ',ibb + +! Average two frames on the second pass only if its incredibly easy to do +! better than nothing. Should be improved. + c=cdat(ic:ic+864-1) + if( iav .eq. 1 ) then + id0=ic+864 + id1=ic+864+863 + if( id1 .le. npts ) then + c=c+cdat(id0:id1) + else + cycle + endif + endif + +! Estimate fine frequency error. + cca=sum(c(1:1+41)*conjg(cb)) + ccb=sum(c(1+56*6:1+56*6+41)*conjg(cb)) cfac=ccb*conjg(cca) ferr2=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt) ! Final estimate of the carrier frequency - returned to the calling program fest=1500+ferr+ferr2 -! Remove fine frequency error - call tweak1(cdat,npts,-ferr2,cdat) +! Remove fine frequency error and put the results in cdat2 + call tweak1(c,npts,-ferr2,c) -! Estimate final frequency error and carrier phase using -! difference and sum of sync-word phases - cca=sum(cdat(ic:ic+41)*conjg(cb)) - ccb=sum(cdat(ic+56*6:ic+56*6+41)*conjg(cb)) +! Estimate final frequency error and carrier phase. + cca=sum(c(1:1+41)*conjg(cb)) + ccb=sum(c(1+56*6:1+56*6+41)*conjg(cb)) cfac=ccb*conjg(cca) ffin=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt) phase0=atan2(imag(cca+ccb),real(cca+ccb)) ! Remove the static phase error from the data cfac=cmplx(cos(phase0),sin(phase0)) - cdat=cdat*conjg(cfac) + c=c*conjg(cfac) -! we hope that we are synced. For now we use only the frame -! that starts at ic - do i=1,864 - ii=ic+i-1 - if( ii .gt. npts ) then - ii=ii-864 - endif - c(i)=cdat(ii) - enddo +! sample to get softsamples do i=1,72 softbits(2*i-1)=imag(c(1+(i-1)*12)) softbits(2*i)=real(c(7+(i-1)*12)) @@ -175,14 +226,19 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) enddo ! calculated the number of sync-word bits that are incorrect +! this might come in handy some day nbadsync=sum(s8*(2*hardbits(1:8)-1)) nbadsync=nbadsync+sum(s8*(2*hardbits(57:57+7)-1)) nbadsync=16-nbadsync +! this could be used to count the number of hard errors that were corrected hardword(1:48)=hardbits(9:9+47) hardword(49:128)=hardbits(65:65+80-1) unscrambledhardbits(1:127:2)=hardword(1:64) unscrambledhardbits(2:128:2)=hardword(65:128) + + +! normalize the softsymbols before submitting to decoder sav=sum(softbits)/144 s2av=sum(softbits*softbits)/144 ssig=sqrt(s2av-sav*sav) @@ -200,11 +256,20 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) max_dither=50 call ldpc_decode(unscrambledsoftbits, decoded, max_iterations, niterations, max_dither, ndither) - if( niterations .lt. 0 ) then - msgreceived=' ' - return +! if( niterations .lt. 0 ) then +! msgreceived=' ' +! return +! endif + if( niterations .ge. 0.0 ) then + goto 778 endif +enddo +enddo +msgreceived=' ' +goto 999 + +778 continue ! The decoder found a codeword - compare decoded hash with calculated ! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash do ibyte=1,10 @@ -234,7 +299,8 @@ subroutine syncmsk144(cdat,npts,metric,msgreceived,fest) call unpackmsg(i4Dec6BitWords,msgreceived) endif -write(78,*) fest,nbadsync,phase0,niterations,ndither,i1hashdec,i1Dec8BitBytes(10),msgreceived -return +write(78,1001) iav,ipk,is,fest,nbadsync,phase0,niterations,ndither,i1hashdec,i1Dec8BitBytes(10),msgreceived +1001 format(i6,i6,i6,f10.1,i6,f10.2,i6,i6,i6,i6,4x,a22) +999 return end subroutine syncmsk144