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cleanup and improvement of syncmsk144

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6736 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke 2016-06-06 01:53:04 +00:00
parent 6e54009797
commit 51428985b3
1 changed files with 26 additions and 22 deletions
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48
lib/syncmsk144.f90
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@ -8,6 +8,7 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
character*22 msgreceived
character*85 pchk_file,gen_file
complex cdat(npts) !Analytic signal
complex cdat2(npts)
complex c(NSPM)
complex ctmp(6000)
complex cb(42) !Complex waveform for sync word
@ -152,15 +153,17 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
enddo
enddo
do iav=0,1
do iav=1,3
do ipk=1,5
do id=1,3
if( id .eq. 1 ) is=0
if( id .eq. 2 ) is=-1
if( id .eq. 3 ) is=1
! we want ic to be the index of the first sample of the message
ic=ipeaks(ipk)
! we want ic to be the index of the first sample of the message
ic=ipeaks(ipk)
! now do fine adjustment of sync index
! bb is used to place the sampling index at the center of the eye
do i=1,6
io=i-3
@ -169,7 +172,6 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
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+is
if( ic .le. 864 ) ic=ic+864
@ -184,22 +186,10 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
! ibb=iloc(1)
! write(*,*) 'ic1: ',ic,'bb peak is at : ',ibb
! Average three frames on the second pass - truncation of the high frame
! is not properly accounted for.
c=cdat(ic:ic+864-1)
if( iav .eq. 1 ) then
id0=ic+864
id1=min(ic+864+863,npts)
np=id1-id0+1
c(1:np)=c(1:np)+cdat(id0:id1)
id0=ic-864
id1=ic-1
c=c+cdat(id0:id1)
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))
! Should a larger separation be used when frames are averaged?
cca=sum(cdat(ic:ic+41)*conjg(cb))
ccb=sum(cdat(ic+56*6:ic+56*6+41)*conjg(cb))
cfac=ccb*conjg(cca)
ferr2=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt)
@ -207,7 +197,19 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
fest=1500+ferr+ferr2
! Remove fine frequency error
call tweak1(c,NSPM,-ferr2,c)
call tweak1(cdat,npts,-ferr2,cdat2)
! place the beginning of the central frame at NSPM+1
cdat2=cshift(cdat2,ic-865)
! Do frame averaging on passes 2 and 3
if( iav .eq. 1 ) then
c=cdat2(NSPM+1:2*NSPM)
elseif( iav .eq. 2 ) then
c=cdat2(NSPM+1:2*NSPM)+cdat2(2*NSPM+1:npts)
elseif( iav .eq. 3 ) then
c=cdat2(1:NSPM)+cdat2(NSPM+1:2*NSPM)+cdat2(2*NSPM+1:npts)
endif
! Estimate final frequency error and carrier phase.
cca=sum(c(1:1+41)*conjg(cb))
@ -238,6 +240,8 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
nbadsync=nbadsync+sum(s8*(2*hardbits(57:57+7)-1))
nbadsync=16-nbadsync
if( nbadsync .gt. 6 ) cycle
! 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)
@ -258,8 +262,8 @@ subroutine syncmsk144(cdat,npts,msgreceived,fest)
unscrambledsoftbits(1:127:2)=lratio(1:64)
unscrambledsoftbits(2:128:2)=lratio(65:128)
max_iterations=20
max_dither=50
max_iterations=10
max_dither=100
call ldpc_decode(unscrambledsoftbits, decoded, max_iterations, niterations, max_dither, ndither)
! if( niterations .lt. 0 ) then