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Enhance click-to-decode performance in MSK144.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7082 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke
parent
966d774f09
commit
1c5a7e0fbc
@ -410,6 +410,7 @@ set (wsjt_FSRCS
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lib/msk144_decode.f90
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lib/msk144sim.f90
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lib/options.f90
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lib/opdetmsk144.f90
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lib/packjt.f90
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lib/pctile.f90
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lib/peakdt9.f90
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@ -38,6 +38,9 @@ subroutine msk144_decode(id2,npts,nutc,nprint,mycall,hiscall, &
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call timer('detec144',0)
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call detectmsk144(c,npts,line,nline,nutc,ntol,t0)
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call timer('detec144',1)
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if( nline .eq. 0 .and. t0 .gt. 0 ) then !Operator detected signal - try averaging 7 frames
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call opdetmsk144(c,npts,line,nline,nutc,ntol,t0)
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endif
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if( nprint .ne. 0 ) then
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do i=1,nline
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write(*,'(a80)') line(i)
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217
lib/opdetmsk144.f90
Normal file
217
lib/opdetmsk144.f90
Normal file
@ -0,0 +1,217 @@
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subroutine opdetmsk144(cbig,n,lines,nmessages,nutc,ntol,t00)
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use timer_module, only: timer
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parameter (NSPM=864, NPTS=7*NSPM, MAXCAND=16)
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character*22 msgreceived,allmessages(20)
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character*80 lines(100)
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complex cbig(n)
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complex cdat(NPTS) !Analytic signal
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complex cdat2(NPTS)
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complex c(NSPM)
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complex ct(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 cfac,cca,ccb
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complex cc1(0:NSPM-1)
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complex cc2(0:NSPM-1)
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complex bb(6)
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integer s8(8),hardbits(144)
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integer, dimension(1) :: iloc
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integer*1 decoded(80)
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integer ipeaks(10)
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real cbi(42),cbq(42)
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real rcw(12)
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real ccm(0:NSPM-1)
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real ccms(0:NSPM-1)
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real dd(0:NSPM-1)
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real pp(12) !Half-sine pulse shape
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real*8 dt, fs, pi, twopi
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real softbits(144)
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real*8 lratio(128)
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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 first,cb,fs,pi,twopi,dt,s8,rcw,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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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 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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nmessages=0
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allmessages=char(0)
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lines=char(0)
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nshort=0
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! write(*,*) "number of points in opdetmsk144",n
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if( n .lt. 24000 .or. n .gt. 49000) return
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nsteps=2*n/6000-1
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! write(*,*) 'nsteps ',nsteps
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nsnr=-4
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do istep=1,nsteps
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ib=(istep-1)*NPTS/2+1
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if( ib+NPTS-1 .gt. n ) ib=n-NPTS+1
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cdat=cbig(ib:ib+NPTS-1)
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xmax=0.0
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bestf=0.0
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do if=-200,200 ! search for frequency that maximizes sync correlation
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ferr=if
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! shift analytic signal to baseband
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call tweak1(cdat,NPTS,-(1500+ferr),cdat2)
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c=0
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do i=1,7
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ib=(i-1)*NSPM+1
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ie=ib+NSPM-1
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c(1:NSPM)=c(1:NSPM)+cdat2(ib:ie)
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enddo
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cc1=0
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cc2=0
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do ish=0,NSPM-1
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ct=cshift(c,ish)
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cc1(ish)=sum(ct(1:42)*conjg(cb))
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cc2(ish)=sum(ct(56*6:56*6+41)*conjg(cb))
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enddo
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ccm=abs(cc1+cc2)
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dd=abs(cc1)*abs(cc2)
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xb=maxval(ccm)
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if( xb .gt. xmax ) then
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xmax=xb
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bestf=ferr
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cs=c
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ccms=ccm
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endif
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enddo
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fest=1500+bestf
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t0=t00+1.0
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c=cs
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ccm=ccms
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! Find 2 largest peaks
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do ipk=1, 2
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iloc=maxloc(ccm)
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ic2=iloc(1)
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ipeaks(ipk)=ic2
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ccm(max(0,ic2-7):min(NSPM-1,ic2+7))=0.0
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enddo
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do ipk=1,2
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do is=1,3
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ic0=ipeaks(ipk)
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if( is.eq.2 ) ic0=max(1,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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! Estimate final frequency error and carrier phase.
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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 - 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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ct=ct*conjg(cfac)
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if( nmatchedfilter .eq. 0 ) then
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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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enddo
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else
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! matched filter -
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softbits(1)=sum(imag(ct(1:6))*pp(7:12))+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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endif
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! sync word hard error weight 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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!write(*,*) 'peak index ',ipk,' pk loc: ',ic0,' nbadsync ',nbadsync
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if( nbadsync .gt. 4 ) cycle
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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=0.75
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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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lratio=exp(2.0*lratio/(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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ndupe=0
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do im=1,nmessages
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if( allmessages(im) .eq. msgreceived ) ndupe=1
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enddo
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if( ndupe .eq. 0 ) then
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nmessages=nmessages+1
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allmessages(nmessages)=msgreceived
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write(lines(nmessages),1020) nutc,nsnr,t0,nint(fest),msgreceived
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1020 format(i6.6,i4,f5.1,i5,' ^ ',a22)
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endif
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goto 999
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else
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msgreceived=' '
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ndither=-99 ! -99 is bad hash flag
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endif
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endif
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enddo ! slicer dither
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enddo ! peak loop
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enddo
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msgreceived=' '
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ndither=-98
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999 continue
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return
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end subroutine opdetmsk144
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