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eec8ef436a
save, to avoid what appears to be a stack overflow on Windows. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6728 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
308 lines
8.4 KiB
Fortran
308 lines
8.4 KiB
Fortran
subroutine syncmsk144(cdat,npts,metric,msgreceived,fest)
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use iso_c_binding, only: c_loc,c_size_t
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use packjt
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use hashing
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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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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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complex csum,cfac,cca,ccb
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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 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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integer*4 i4Msg6BitWords(12) !72-bit message as 6-bit words
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integer*4 i4Dec6BitWords(12)
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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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real rcw(12)
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real dd(npts)
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real pp(12) !Half-sine pulse shape
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real*8 dt, df, fs, twopi
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real softbits(144)
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real*8 unscrambledsoftbits(128)
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real lratio(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,cd,pi,twopi,dt,f0,f1
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save
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if(first) then
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! These files can be found in /lib/ldpc/jtmode_codes directory
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pchk_file="peg-128-80-reg3.pchk"
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gen_file="peg-128-80-reg3.gen"
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call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
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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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dt=1.0/12000.0
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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 waveform
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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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! Coarse carrier frequency sync
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! look for tones near 2k and 4k in the (analytic signal)**2 spectrum
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! search range for coarse frequency error is +/- 100 Hz
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fs=12000.0
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nfft=6000 !using a zero-padded fft to get 2 Hz bins
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df=fs/nfft
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ctmp=cmplx(0.0,0.0)
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ctmp(1:npts)=cdat**2
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ctmp(1:12)=ctmp(1:12)*rcw
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ctmp(npts-11:npts)=ctmp(npts-11:npts)*rcw(12:1:-1)
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call four2a(ctmp,nfft,1,-1,1)
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tonespec=abs(ctmp)**2
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ismask=.false.
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ismask(1901:2101)=.true. ! high tone search window
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iloc=maxloc(tonespec,ismask)
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ihpk=iloc(1)
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ah=tonespec(ihpk)
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ismask=.false.
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ismask(901:1101)=.true. ! window for low tone
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iloc=maxloc(tonespec,ismask)
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ilpk=iloc(1)
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al=tonespec(ilpk)
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if( ah .ge. al ) then
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ferr=(ihpk-2001)*df/2.0
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tot=sum(tonespec(1901:2101))
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q1=200*ah/(tot-tonespec(ihpk))
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else
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ferr=(ilpk-1001)*df/2.0
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tot=sum(tonespec(901:1101))
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q1=200*al/(tot-tonespec(ilpk))
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endif
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fdiff=(ihpk-ilpk)*df
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! remove coarse freq error - should now be within a few Hz
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call tweak1(cdat,npts,-(1500+ferr),cdat)
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! attempt frame synchronization
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! correlate with sync word waveforms - the resulting complex
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! correlations provide all synch information.
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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-(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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! 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 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.
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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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c=c*conjg(cfac)
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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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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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! 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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softbits=softbits/ssig
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sigma=0.65
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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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lratio=exp(2.0*lratio/(sigma*sigma))
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unscrambledsoftbits(1:127:2)=lratio(1:64)
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unscrambledsoftbits(2:128:2)=lratio(65:128)
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max_iterations=20
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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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! 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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itmp=0
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do ibit=1,8
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itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*8+ibit))
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enddo
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i1Dec8BitBytes(ibyte)=itmp
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enddo
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! Calculate the hash using the first 9 bytes.
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ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
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ihashdec=2*iand(ihashdec,255)
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! Compare calculated hash with received byte 10 - if they agree, keep the message.
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i1hashdec=ihashdec
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if( i1hashdec .eq. i1Dec8BitBytes(10) ) then
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! Good hash --- unpack 72-bit message
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do ibyte=1,12
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itmp=0
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do ibit=1,6
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itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
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enddo
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i4Dec6BitWords(ibyte)=itmp
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enddo
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call unpackmsg(i4Dec6BitWords,msgreceived)
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endif
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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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