ft8d/ft8b.f90

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Fortran
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subroutine ft8b(dd0,newdat,nQSOProgress,nfqso,nftx,ndepth,lapon,lapcqonly, &
napwid,nagain,iaptype,f1,xdt,xbase,apsym,nharderrors,dmin, &
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nbadcrc,ipass,msgcall,msggrid,xsnr)
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use crc
include 'ft8_params.f90'
parameter(NP2=2812)
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character msgcall*6,msggrid*4,message*22
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real a(5)
real s1(0:7,ND),s2(0:7,NN),s1sort(8*ND)
real ps(0:7),psl(0:7)
real bmeta(3*ND),bmetb(3*ND),bmetap(3*ND)
real llr(3*ND),llra(3*ND),llr0(3*ND),llr1(3*ND),llrap(3*ND) !Soft symbols
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complex dd0(NMAX)
integer*1 decoded(KK),apmask(3*ND),cw(3*ND)
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integer apsym(KK)
integer mcq(28),mde(28),mrrr(16),m73(16),mrr73(16)
integer itone(NN)
integer indxs1(8*ND)
integer icos7(0:6),ip(1)
integer nappasses(0:5) !Number of decoding passes to use for each QSO state
integer naptypes(0:5,4) ! (nQSOProgress, decoding pass) maximum of 4 passes for now
complex cd0(3200)
complex ctwk(32)
complex csymb(32)
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logical first,newdat,lapon,lapcqonly,nagain
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equivalence (s1,s1sort)
data icos7/2,5,6,0,4,1,3/
data mcq/1,1,1,1,1,0,1,0,0,0,0,0,1,0,0,0,0,0,1,1,0,0,0,1,1,0,0,1/
data mrrr/0,1,1,1,1,1,1,0,1,1,0,0,1,1,1,1/
data m73/0,1,1,1,1,1,1,0,1,1,0,1,0,0,0,0/
data mde/1,1,1,1,1,1,1,1,0,1,1,0,0,1,0,0,0,0,0,1,1,1,0,1,0,0,0,1/
data mrr73/0,0,0,0,0,0,1,0,0,0,0,1,0,1,0,1/
data first/.true./
save nappasses,naptypes
if(first) then
mcq=2*mcq-1
mde=2*mde-1
mrrr=2*mrrr-1
m73=2*m73-1
mrr73=2*mrr73-1
nappasses(0)=2
nappasses(1)=2
nappasses(2)=2
nappasses(3)=4
nappasses(4)=4
nappasses(5)=3
! iaptype
!------------------------
! 1 CQ ??? ???
! 2 MyCall ??? ???
! 3 MyCall DxCall ???
! 4 MyCall DxCall RRR
! 5 MyCall DxCall 73
! 6 MyCall DxCall RR73
! 7 ??? DxCall ???
naptypes(0,1:4)=(/1,2,0,0/)
naptypes(1,1:4)=(/2,3,0,0/)
naptypes(2,1:4)=(/2,3,0,0/)
naptypes(3,1:4)=(/3,4,5,6/)
naptypes(4,1:4)=(/3,4,5,6/)
naptypes(5,1:4)=(/3,1,2,0/)
first=.false.
endif
max_iterations=30
nharderrors=-1
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fs2=4000.0/NDOWN
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dt2=1.0/fs2
twopi=8.0*atan(1.0)
delfbest=0.
ibest=0
call ft8_downsample(dd0,newdat,f1,cd0) !Mix f1 to baseband and downsample
i0=nint((xdt+0.5)*fs2) !Initial guess for start of signal
smax=0.0
do idt=i0-8,i0+8 !Search over +/- one quarter symbol
call sync8d(cd0,idt,ctwk,0,sync)
if(sync.gt.smax) then
smax=sync
ibest=idt
endif
enddo
xdt2=ibest*dt2 !Improved estimate for DT
! Now peak up in frequency
i0=nint(xdt2*fs2)
smax=0.0
do ifr=-5,5 !Search over +/- 2.5 Hz
delf=ifr*0.5
dphi=twopi*delf*dt2
phi=0.0
do i=1,32
ctwk(i)=cmplx(cos(phi),sin(phi))
phi=mod(phi+dphi,twopi)
enddo
call sync8d(cd0,i0,ctwk,1,sync)
if( sync .gt. smax ) then
smax=sync
delfbest=delf
endif
enddo
a=0.0
a(1)=-delfbest
call twkfreq1(cd0,NP2,fs2,a,cd0)
xdt=xdt2
f1=f1+delfbest !Improved estimate of DF
call sync8d(cd0,i0,ctwk,2,sync)
j=0
do k=1,NN
i1=ibest+(k-1)*32
csymb=cmplx(0.0,0.0)
if( i1.ge.1 .and. i1+31 .le. NP2 ) csymb=cd0(i1:i1+31)
call four2a(csymb,32,1,-1,1)
s2(0:7,k)=abs(csymb(1:8))/1e3
enddo
! sync quality check
is1=0
is2=0
is3=0
do k=1,7
ip=maxloc(s2(:,k))
if(icos7(k-1).eq.(ip(1)-1)) is1=is1+1
ip=maxloc(s2(:,k+36))
if(icos7(k-1).eq.(ip(1)-1)) is2=is2+1
ip=maxloc(s2(:,k+72))
if(icos7(k-1).eq.(ip(1)-1)) is3=is3+1
enddo
! hard sync sum - max is 21
nsync=is1+is2+is3
if(nsync .le. 6) then ! bail out
nbadcrc=1
return
endif
j=0
do k=1,NN
if(k.le.7) cycle
if(k.ge.37 .and. k.le.43) cycle
if(k.gt.72) cycle
j=j+1
s1(0:7,j)=s2(0:7,k)
enddo
call indexx(s1sort,8*ND,indxs1)
xmeds1=s1sort(indxs1(nint(0.5*8*ND)))
s1=s1/xmeds1
do j=1,ND
i4=3*j-2
i2=3*j-1
i1=3*j
! Max amplitude
ps=s1(0:7,j)
r1=max(ps(1),ps(3),ps(5),ps(7))-max(ps(0),ps(2),ps(4),ps(6))
r2=max(ps(2),ps(3),ps(6),ps(7))-max(ps(0),ps(1),ps(4),ps(5))
r4=max(ps(4),ps(5),ps(6),ps(7))-max(ps(0),ps(1),ps(2),ps(3))
bmeta(i4)=r4
bmeta(i2)=r2
bmeta(i1)=r1
bmetap(i4)=r4
bmetap(i2)=r2
bmetap(i1)=r1
! Max log metric
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psl=log(ps+1e-32)
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r1=max(psl(1),psl(3),psl(5),psl(7))-max(psl(0),psl(2),psl(4),psl(6))
r2=max(psl(2),psl(3),psl(6),psl(7))-max(psl(0),psl(1),psl(4),psl(5))
r4=max(psl(4),psl(5),psl(6),psl(7))-max(psl(0),psl(1),psl(2),psl(3))
bmetb(i4)=r4
bmetb(i2)=r2
bmetb(i1)=r1
! Metric for Cauchy noise
! r1=log(ps(1)**3+ps(3)**3+ps(5)**3+ps(7)**3)- &
! log(ps(0)**3+ps(2)**3+ps(4)**3+ps(6)**3)
! r2=log(ps(2)**3+ps(3)**3+ps(6)**3+ps(7)**3)- &
! log(ps(0)**3+ps(1)**3+ps(4)**3+ps(5)**3)
! r4=log(ps(4)**3+ps(5)**3+ps(6)**3+ps(7)**3)- &
! log(ps(0)**3+ps(1)**3+ps(2)**3+ps(3)**3)
! Metric for AWGN, no fading
! bscale=2.5
! b0=bessi0(bscale*ps(0))
! b1=bessi0(bscale*ps(1))
! b2=bessi0(bscale*ps(2))
! b3=bessi0(bscale*ps(3))
! b4=bessi0(bscale*ps(4))
! b5=bessi0(bscale*ps(5))
! b6=bessi0(bscale*ps(6))
! b7=bessi0(bscale*ps(7))
! r1=log(b1+b3+b5+b7)-log(b0+b2+b4+b6)
! r2=log(b2+b3+b6+b7)-log(b0+b1+b4+b5)
! r4=log(b4+b5+b6+b7)-log(b0+b1+b2+b3)
if(nQSOProgress .eq. 0 .or. nQSOProgress .eq. 5) then
! When bits 88:115 are set as ap bits, bit 115 lives in symbol 39 along
! with no-ap bits 116 and 117. Take care of metrics for bits 116 and 117.
if(j.eq.39) then ! take care of bits that live in symbol 39
if(apsym(28).lt.0) then
bmetap(i2)=max(ps(2),ps(3))-max(ps(0),ps(1))
bmetap(i1)=max(ps(1),ps(3))-max(ps(0),ps(2))
else
bmetap(i2)=max(ps(6),ps(7))-max(ps(4),ps(5))
bmetap(i1)=max(ps(5),ps(7))-max(ps(4),ps(6))
endif
endif
endif
! When bits 116:143 are set as ap bits, bit 115 lives in symbol 39 along
! with ap bits 116 and 117. Take care of metric for bit 115.
! if(j.eq.39) then ! take care of bit 115
! iii=2*(apsym(29)+1)/2 + (apsym(30)+1)/2 ! known values of bits 116 & 117
! if(iii.eq.0) bmetap(i4)=ps(4)-ps(0)
! if(iii.eq.1) bmetap(i4)=ps(5)-ps(1)
! if(iii.eq.2) bmetap(i4)=ps(6)-ps(2)
! if(iii.eq.3) bmetap(i4)=ps(7)-ps(3)
! endif
! bit 144 lives in symbol 48 and will be 1 if it is set as an ap bit.
! take care of metrics for bits 142 and 143
if(j.eq.48) then ! bit 144 is always 1
bmetap(i4)=max(ps(5),ps(7))-max(ps(1),ps(3))
bmetap(i2)=max(ps(3),ps(7))-max(ps(1),ps(5))
endif
! bit 154 lives in symbol 52 and will be 0 if it is set as an ap bit
! take care of metrics for bits 155 and 156
if(j.eq.52) then ! bit 154 will be 0 if it is set as an ap bit.
bmetap(i2)=max(ps(2),ps(3))-max(ps(0),ps(1))
bmetap(i1)=max(ps(1),ps(3))-max(ps(0),ps(2))
endif
enddo
call normalizebmet(bmeta,3*ND)
call normalizebmet(bmetb,3*ND)
call normalizebmet(bmetap,3*ND)
scalefac=2.83
llr0=scalefac*bmeta
llr1=scalefac*bmetb
llra=scalefac*bmetap ! llr's for use with ap
apmag=scalefac*(maxval(abs(bmetap))*1.01)
! pass #
!------------------------------
! 1 regular decoding
! 2 erase 24
! 3 erase 48
! 4 ap pass 1
! 5 ap pass 2
! 6 ap pass 3
! 7 ap pass 4, etc.
if(lapon) then
if(.not.lapcqonly) then
npasses=4+nappasses(nQSOProgress)
else
npasses=5
endif
else
npasses=4
endif
do ipass=1,npasses
llr=llr0
if(ipass.eq.2) llr=llr1
if(ipass.eq.3) llr(1:24)=0.
if(ipass.eq.4) llr(1:48)=0.
if(ipass.le.4) then
apmask=0
llrap=llr
iaptype=0
endif
if(ipass .gt. 4) then
if(.not.lapcqonly) then
iaptype=naptypes(nQSOProgress,ipass-4)
else
iaptype=1
endif
if(iaptype.ge.3 .and. (abs(f1-nfqso).gt.napwid .and. abs(f1-nftx).gt.napwid) ) cycle
if(iaptype.eq.1 .or. iaptype.eq.2 ) then ! AP,???,???
apmask=0
apmask(88:115)=1 ! first 28 bits are AP
apmask(144)=1 ! not free text
llrap=llr
if(iaptype.eq.1) llrap(88:115)=apmag*mcq
if(iaptype.eq.2) llrap(88:115)=apmag*apsym(1:28)
llrap(116:117)=llra(116:117)
llrap(142:143)=llra(142:143)
llrap(144)=-apmag
endif
if(iaptype.eq.3) then ! mycall, dxcall, ???
apmask=0
apmask(88:115)=1 ! mycall
apmask(116:143)=1 ! hiscall
apmask(144)=1 ! not free text
llrap=llr
llrap(88:143)=apmag*apsym(1:56)
llrap(144)=-apmag
endif
if(iaptype.eq.4 .or. iaptype.eq.5 .or. iaptype.eq.6) then
apmask=0
apmask(88:115)=1 ! mycall
apmask(116:143)=1 ! hiscall
apmask(144:159)=1 ! RRR or 73 or RR73
llrap=llr
llrap(88:143)=apmag*apsym(1:56)
if(iaptype.eq.4) llrap(144:159)=apmag*mrrr
if(iaptype.eq.5) llrap(144:159)=apmag*m73
if(iaptype.eq.6) llrap(144:159)=apmag*mrr73
endif
if(iaptype.eq.7) then ! ???, dxcall, ???
apmask=0
apmask(116:143)=1 ! hiscall
apmask(144)=1 ! not free text
llrap=llr
llrap(115)=llra(115)
llrap(116:143)=apmag*apsym(29:56)
llrap(144)=-apmag
endif
endif
cw=0
call bpdecode174(llrap,apmask,max_iterations,decoded,cw,nharderrors, &
niterations)
dmin=0.0
if(ndepth.eq.3 .and. nharderrors.lt.0) then
ndeep=3
if(abs(nfqso-f1).le.napwid .or. abs(nftx-f1).le.napwid) then
if((ipass.eq.3 .or. ipass.eq.4) .and. .not.nagain) then
ndeep=3
else
ndeep=4
endif
endif
if(nagain) ndeep=5
call osd174(llrap,apmask,ndeep,decoded,cw,nharderrors,dmin)
endif
nbadcrc=1
message=' '
xsnr=-99.0
if(count(cw.eq.0).eq.174) cycle !Reject the all-zero codeword
if(nharderrors.ge.0 .and. nharderrors+dmin.lt.60.0 .and. &
.not.(sync.lt.2.0 .and. nharderrors.gt.35) .and. &
.not.(ipass.gt.2 .and. nharderrors.gt.39) .and. &
.not.(ipass.eq.4 .and. nharderrors.gt.30) &
) then
call chkcrc12a(decoded,nbadcrc)
else
nharderrors=-1
cycle
endif
if(nbadcrc.eq.0) then
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call extractmessage174(decoded,message,msgcall,msggrid,ncrcflag)
call genft8(message,0,itone)
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xsig=0.0
xnoi=0.0
do i=1,79
xsig=xsig+s2(itone(i),i)**2
ios=mod(itone(i)+4,7)
xnoi=xnoi+s2(ios,i)**2
enddo
xsnr=0.001
if(xnoi.gt.0 .and. xnoi.lt.xsig) xsnr=xsig/xnoi-1.0
xsnr=10.0*log10(xsnr)-27.0
xsnr2=db(xsig/xbase - 1.0) - 32.0
if(.not.nagain) xsnr=xsnr2
if(xsnr .lt. -24.0) xsnr=-24.0
return
endif
enddo
return
end subroutine ft8b
subroutine normalizebmet(bmet,n)
real bmet(n)
bmetav=sum(bmet)/real(n)
bmet2av=sum(bmet*bmet)/real(n)
var=bmet2av-bmetav*bmetav
if( var .gt. 0.0 ) then
bmetsig=sqrt(var)
else
bmetsig=sqrt(bmet2av)
endif
bmet=bmet/bmetsig
return
end subroutine normalizebmet
function bessi0(x)
! From Numerical Recipes
real bessi0,x
double precision p1,p2,p3,p4,p5,p6,p7,q1,q2,q3,q4,q5,q6,q7,q8,q9,y
save p1,p2,p3,p4,p5,p6,p7,q1,q2,q3,q4,q5,q6,q7,q8,q9
data p1,p2,p3,p4,p5,p6,p7/1.0d0,3.5156229d0,3.0899424d0,1.2067492d0, &
0.2659732d0,0.360768d-1,0.45813d-2/
data q1,q2,q3,q4,q5,q6,q7,q8,q9/0.39894228d0,0.1328592d-1, &
0.225319d-2,-0.157565d-2,0.916281d-2,-0.2057706d-1, &
0.2635537d-1,-0.1647633d-1,0.392377d-2/
if (abs(x).lt.3.75) then
y=(x/3.75)**2
bessi0=p1+y*(p2+y*(p3+y*(p4+y*(p5+y*(p6+y*p7)))))
else
ax=abs(x)
y=3.75/ax
bessi0=(exp(ax)/sqrt(ax))*(q1+y*(q2+y*(q3+y*(q4 &
+y*(q5+y*(q6+y*(q7+y*(q8+y*q9))))))))
endif
return
end function bessi0