233 lines
5.5 KiB
Plaintext
233 lines
5.5 KiB
Plaintext
subroutine ft8b(dd0,newdat,nfqso,f1,xdt,nharderrors,dmin,nbadcrc,message,xsnr)
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use timer_module, only: timer
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include 'ft8_params.f90'
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parameter(NRECENT=10,NP2=2812)
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character message*22,msgsent*22
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character*12 recent_calls(NRECENT)
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real a(5)
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real s1(0:7,ND),s2(0:7,NN)
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real ps(0:7)
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real rxdata(3*ND),llr(3*ND) !Soft symbols
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real dd0(15*12000)
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integer*1 decoded(KK),apmask(3*ND),cw(3*ND)
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integer itone(NN)
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integer icos7(0:6)
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complex cd0(3125)
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complex csync(0:6,32)
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complex ctwk(32)
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complex csymb(32)
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logical newdat,first
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data icos7/2,5,6,0,4,1,3/
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data first/.true./
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save first,twopi,fs2,dt2,taus,baud,csync
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if( first ) then
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twopi=8.0*atan(1.0)
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fs2=12000.0/64.0
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dt2=1/fs2
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taus=32*dt2
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baud=1/taus
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do i=0,6
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phi=0.0
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dphi=twopi*icos7(i)*baud*dt2
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do j=1,32
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csync(i,j)=cmplx(cos(phi),sin(phi))
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phi=mod(phi+dphi,twopi)
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enddo
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enddo
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first=.false.
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endif
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max_iterations=40
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norder=2
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! if(abs(nfqso-f1).lt.10.0) norder=3
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call timer('ft8_down',0)
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call ft8_downsample(dd0,newdat,f1,cd0)
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call timer('ft8_down',1)
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i0=xdt*fs2
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smax=0.0
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do idt=i0-16,i0+16
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sync=0
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do i=0,6
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i1=idt+i*32
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i2=i1+36*32
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i3=i1+72*32
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term1=0.0 ! this needs to be fixed...
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term2=0.0
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term3=0.0
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if( i1.ge.1 .and. i1+31.le.NP2 ) &
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term1=abs(sum(cd0(i1:i1+31)*conjg(csync(i,1:32))))
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if( i2.ge.1 .and. i2+31.le.NP2 ) &
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term2=abs(sum(cd0(i2:i2+31)*conjg(csync(i,1:32))))
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if( i3.ge.1 .and. i3+31.le.NP2 ) &
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term3=abs(sum(cd0(i3:i3+31)*conjg(csync(i,1:32))))
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sync=sync+term1+term2+term3
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enddo
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if( sync .gt. smax ) then
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smax=sync
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ibest=idt
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endif
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enddo
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xdt2=ibest*dt2
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! peak up the frequency
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i0=xdt2*fs2
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smax=0.0
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do ifr=-5,5
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delf=ifr*0.5
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dphi=twopi*delf*dt2
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phi=0.0
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do i=1,32
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ctwk(i)=cmplx(cos(phi),sin(phi))
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phi=mod(phi+dphi,twopi)
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enddo
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sync=0.0
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do i=0,6
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i1=i0+i*32
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i2=i1+36*32
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i3=i1+72*32
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term1=0.0 ! this needs to be fixed...
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term2=0.0
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term3=0.0
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if( i1.ge.1 .and. i1+31.le.NP2 ) &
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term1=abs(sum(cd0(i1:i1+31)*conjg(ctwk*csync(i,1:32))))
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if( i2.ge.1 .and. i2+31.le.NP2 ) &
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term2=abs(sum(cd0(i2:i2+31)*conjg(ctwk*csync(i,1:32))))
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if( i3.ge.1 .and. i3+31.le.NP2 ) &
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term3=abs(sum(cd0(i3:i3+31)*conjg(ctwk*csync(i,1:32))))
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sync=sync+term1+term2+term3
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enddo
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if( sync .gt. smax ) then
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smax=sync
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delfbest=delf
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endif
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enddo
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a=0.0
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a(1)=-delfbest
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call twkfreq1(cd0,NP2,fs2,a,cd0)
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xdt=xdt2
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f1=f1+delfbest
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j=0
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do k=1,NN
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i1=ibest+(k-1)*32
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csymb=cmplx(0.0,0.0)
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if( i1.ge.1 .and. i1+31 .le. NP2 ) csymb=cd0(i1:i1+31)
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call four2a(csymb,32,1,-1,1)
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s2(0:7,k)=abs(csymb(1:8))
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enddo
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j=0
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do k=1,NN
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if(k.le.7) cycle
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if(k.ge.37 .and. k.le.43) cycle
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if(k.gt.72) cycle
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j=j+1
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s1(0:7,j)=s2(0:7,k)
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enddo
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do j=1,ND
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ps=s1(0:7,j)
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where (ps.gt.0.0) ps=log(ps)
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r1=max(ps(1),ps(3),ps(5),ps(7))-max(ps(0),ps(2),ps(4),ps(6))
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r2=max(ps(2),ps(3),ps(6),ps(7))-max(ps(0),ps(1),ps(4),ps(5))
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r4=max(ps(4),ps(5),ps(6),ps(7))-max(ps(0),ps(1),ps(2),ps(3))
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rxdata(3*j-2)=r4
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rxdata(3*j-1)=r2
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rxdata(3*j)=r1
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enddo
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rxav=sum(rxdata)/(3.0*ND)
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rx2av=sum(rxdata*rxdata)/(3.0*ND)
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var=rx2av-rxav*rxav
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if( var .gt. 0.0 ) then
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rxsig=sqrt(var)
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else
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rxsig=sqrt(rx2av)
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endif
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rxdata=rxdata/rxsig
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ss=0.84
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llr=2.0*rxdata/(ss*ss)
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apmask=0
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cw=0
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call timer('bpd174 ',0)
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call bpdecode174(llr,apmask,max_iterations,decoded,cw,nharderrors)
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call timer('bpd174 ',1)
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dmin=0.0
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if(nharderrors.lt.0) then
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call timer('osd174 ',0)
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call osd174(llr,norder,decoded,cw,nharderrors,dmin)
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call timer('osd174 ',1)
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endif
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nbadcrc=1
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message=' '
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xsnr=-99.0
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if(count(cw.eq.0).eq.174) go to 900 !Reject the all-zero codeword
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if( nharderrors.ge.0 .and. dmin.le.30.0 .and. nharderrors .lt. 30) then
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call chkcrc12a(decoded,nbadcrc)
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else
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nharderrors=-1
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go to 900
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endif
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if(nbadcrc.eq.0) then
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call extractmessage174(decoded,message,ncrcflag,recent_calls,nrecent)
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call genft8(message,msgsent,itone)
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xsig=0.0
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xnoi=0.0
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do i=1,79
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xsig=xsig+s2(itone(i),i)**2
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ios=mod(itone(i)+4,7)
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xnoi=xnoi+s2(ios,i)**2
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enddo
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xsnr=0.001
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if( xnoi.gt.0 .and. xnoi.lt.xsig ) xsnr=xsig/xnoi-1.0
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xsnr=10.0*log10(xsnr)-27.0
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if( xsnr .lt. -24.0 ) xsnr=-24.0
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endif
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900 continue
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return
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end subroutine ft8b
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subroutine ft8_downsample(dd,newdat,f0,c1)
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! Downconvert to complex data sampled at 187.5 Hz, 32 samples/symbol
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parameter (NMAX=15*12000)
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parameter (NFFT1=200000,NFFT2=3125) !200000/64 = 3125
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logical newdat
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complex c1(0:NFFT2-1)
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complex cx(0:NFFT1/2)
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real dd(NMAX),x(NFFT1)
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equivalence (x,cx)
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save cx
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if(newdat) then
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! Data in dd have changed, recompute the long FFT
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x(1:NMAX)=dd
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x(NMAX+1:NFFT1)=0. !Zero-pad the x array
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call four2a(cx,NFFT1,1,-1,0) !r2c FFT to freq domain
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newdat=.false.
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endif
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df=12000.0/NFFT1
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baud=12000.0/2048.0
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i0=nint(f0/df)
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ft=f0+8.0*baud
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it=min(nint(ft/df),NFFT1/2)
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fb=f0-1.0*baud
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ib=max(1,nint(fb/df))
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k=0
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c1=0.
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do i=ib,it
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c1(k)=cx(i)
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k=k+1
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enddo
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c1=cshift(c1,i0-ib)
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call four2a(c1,NFFT2,1,1,1) !c2c FFT back to time domain
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fac=1.0/sqrt(float(NFFT1)*NFFT2)
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c1=fac*c1
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return
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end subroutine ft8_downsample
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