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https://github.com/saitohirga/WSJT-X.git
synced 2025-05-24 02:12:37 -04:00
Move decoding of synced frame into a subroutine.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7100 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke
parent
e1ef9b0ee0
commit
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109
lib/msk144decodeframe.f90
Normal file
109
lib/msk144decodeframe.f90
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@ -0,0 +1,109 @@
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subroutine msk144decodeframe(c,msgreceived,nsuccess)
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use timer_module, only: timer
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parameter (NSPM=864)
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character*22 msgreceived
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complex cb(42)
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complex cfac,cca,ccb
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complex c(NSPM)
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integer*1 decoded(80)
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integer s8(8),hardbits(144)
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real*8 dt, df, fs, pi, twopi
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real cbi(42),cbq(42)
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real pp(12)
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real softbits(144)
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real llr(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 df,first,cb,fs,pi,twopi,dt,s8,pp,nmatchedfilter
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if(first) then
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nmatchedfilter=1
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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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fs=12000.0
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dt=1.0/fs
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df=fs/NFFT
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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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enddo
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! define the sync word waveforms
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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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first=.false.
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endif
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nsuccess=0
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msgreceived=' '
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! Estimate 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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phase0=atan2(imag(cca+ccb),real(cca+ccb))
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! Remove phase error - want constellation rotated so that sample points lie on I/Q axes
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cfac=cmplx(cos(phase0),sin(phase0))
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c=c*conjg(cfac)
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! matched filter -
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softbits(1)=sum(imag(c(1:6))*pp(7:12))+sum(imag(c(864-5:864))*pp(1:6))
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softbits(2)=sum(real(c(1:12))*pp)
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do i=2,72
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softbits(2*i-1)=sum(imag(c(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
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softbits(2*i)=sum(real(c(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
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enddo
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! sync word hard error weight is used as a discriminator for
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! frames that have reasonable probability of decoding
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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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nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8 ) )/2
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nbadsync2=(8-sum( (2*hardbits(1+56:8+56)-1)*s8 ) )/2
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nbadsync=nbadsync1+nbadsync2
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if( nbadsync .gt. 4 ) then
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return
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endif
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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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softbits=softbits/ssig
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sigma=0.70
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llr(1:48)=softbits(9:9+47)
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llr(49:128)=softbits(65:65+80-1)
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llr=2.0*llr/(sigma*sigma)
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max_iterations=10
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max_dither=1
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call timer('bpdec144 ',0)
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call bpdecode144(llr,max_iterations,decoded,niterations)
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call timer('bpdec144 ',1)
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if( niterations .ge. 0.0 ) then
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call extractmessage144(decoded,msgreceived,nhashflag)
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if( nhashflag .gt. 0 ) then ! CRCs match, so print it
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nsuccess=1
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endif
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endif
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return
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end subroutine msk144decodeframe
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@ -21,24 +21,19 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
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complex ct2(2*NSPM)
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complex ct2(2*NSPM)
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complex cs(NSPM)
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complex cs(NSPM)
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complex cb(42) !Complex waveform for sync word
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complex cb(42) !Complex waveform for sync word
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complex cfac,cca,ccb
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complex cc(0:NSPM-1)
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complex cc(0:NSPM-1)
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! integer*8 count0,count1,count2,count3,clkfreq
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! integer*8 count0,count1,count2,count3,clkfreq
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integer s8(8),hardbits(144)
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integer s8(8)
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integer iloc(1)
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integer iloc(1)
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integer ipeaks(10)
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integer ipeaks(10)
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integer nav(6)
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integer nav(6)
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integer*1 decoded(80)
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real cbi(42),cbq(42)
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real cbi(42),cbq(42)
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real d(NFFT1)
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real d(NFFT1)
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real xcc(0:NSPM-1)
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real xcc(0:NSPM-1)
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real xccs(0:NSPM-1)
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real xccs(0:NSPM-1)
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real pp(12) !Half-sine pulse shape
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real pp(12) !Half-sine pulse shape
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real softbits(144)
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real lratio(128)
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real llr(128)
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logical first
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logical first
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data first/.true./
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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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data s8/0,1,1,1,0,0,1,0/
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@ -87,7 +82,7 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
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call analytic(d,NZ,NFFT1,cdat) !Convert to analytic signal and filter
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call analytic(d,NZ,NFFT1,cdat) !Convert to analytic signal and filter
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nmessages=0
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nmessages=0
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line=char(0)
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line=' '
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nshort=0
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nshort=0
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npts=7168
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npts=7168
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nsnr=-4 !### Temporary ###
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nsnr=-4 !### Temporary ###
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@ -145,61 +140,13 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
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if(is.eq.3) ic0=min(NSPM,ic0+1)
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if(is.eq.3) ic0=min(NSPM,ic0+1)
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ct=cshift(c,ic0-1)
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ct=cshift(c,ic0-1)
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! Estimate final frequency error and carrier phase.
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call msk144decodeframe(ct,msgreceived,nsuccess)
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cca=sum(ct(1:1+41)*conjg(cb))
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ccb=sum(ct(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 phase error: rotate constellation so sample points lie on I/Q axes
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if(nsuccess .gt. 0) then
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cfac=cmplx(cos(phase0),sin(phase0))
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write(*,*) nsuccess,msgreceived
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ct=ct*conjg(cfac)
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! Use matched filter
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softbits(1)=sum(imag(ct(1:6))*pp(7:12)) + &
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sum(imag(ct(864-5:864))*pp(1:6))
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softbits(2)=sum(real(ct(1:12))*pp)
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do i=2,72
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softbits(2*i-1)=sum(imag(ct(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
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softbits(2*i)=sum(real(ct(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
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enddo
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! Number of hard errors in sync word is a good discriminator for
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! frames that have reasonable probability of decoding
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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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nbadsync1=(8-sum((2*hardbits(1:8)-1)*s8))/2
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nbadsync2=(8-sum((2*hardbits(1+56:8+56)-1)*s8))/2
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nbadsync=nbadsync1+nbadsync2
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if(nbadsync .gt. 3) cycle
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! Normalize 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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softbits=softbits/ssig
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sigma=0.70
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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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llr=2.0*lratio/(sigma*sigma)
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call bpdecode144(llr,max_iterations,decoded,niterations)
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if(niterations .ge. 0.0) then
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call extractmessage144(decoded,msgreceived,nhashflag)
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if(nhashflag .gt. 0) then ! CRCs match, so print it
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write(line,1020) nutc0,nsnr,tsec,nint(fest),msgreceived,char(0)
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write(line,1020) nutc0,nsnr,tsec,nint(fest),msgreceived,char(0)
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1020 format(i6.6,i4,f5.1,i5,' ^ ',a22,a1)
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1020 format(i6.6,i4,f5.1,i5,' ^ ',a22,a1)
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endif
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goto 999
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goto 999
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else
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msgreceived=' '
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ndither=-99 !Bad hash flag = -99
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endif
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endif
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enddo !Slicer dither
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enddo !Slicer dither
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enddo !Peak loop
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enddo !Peak loop
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@ -221,4 +168,3 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
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return
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return
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end subroutine mskrtd
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end subroutine mskrtd
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