WSJT-X/lib/ft8/ft8_a7.f90

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Fortran
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module ft8_a7
parameter(MAXDEC=100)
! For the following three arrays
! First index i=decode number in this sequence
! Second index j=0 or 1 for even or odd sequence
! Third index k=0 or 1 for previous or current tally for this j
real dt0(MAXDEC,0:1,0:1) !dt0(i,j,k)
real f0(MAXDEC,0:1,0:1) !f0(i,j,k)
character*37 msg0(MAXDEC,0:1,0:1) !msg0(i,j,k)
integer itone_a7(79)
integer jseq !even=0, odd=1
integer ndec(0:1,0:1) !ndec(j,k)
data ndec/4*0/,jseq/0/
contains
subroutine ft8_a7_save(nutc,dt,f,msg)
use packjt77
character*37 msg,msg1
character*13 w(19)
character*4 g4
integer nw(19)
logical isgrid4
! Statement function:
isgrid4(g4)=(len_trim(g4).eq.4 .and. &
ichar(g4(1:1)).ge.ichar('A') .and. ichar(g4(1:1)).le.ichar('R') .and. &
ichar(g4(2:2)).ge.ichar('A') .and. ichar(g4(2:2)).le.ichar('R') .and. &
ichar(g4(3:3)).ge.ichar('0') .and. ichar(g4(3:3)).le.ichar('9') .and. &
ichar(g4(4:4)).ge.ichar('0') .and. ichar(g4(4:4)).le.ichar('9'))
if(index(msg,'/').ge.1 .or. index(msg,'<').ge.1) go to 999
call split77(msg,nwords,nw,w) !Parse msg into words
if(nwords.lt.1) go to 999
if(w(1)(1:3).eq.'CQ_') go to 999
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j=mod(nutc/5,2) !j is 0 or 1 for odd/even sequence
jseq=j
! Add this decode to current table for this sequence
ndec(j,1)=ndec(j,1)+1 !Number of decodes in this sequence
i=ndec(j,1) !i is index of a new table entry
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if(i.ge.MAXDEC-1) return !Prevent table overflow
dt0(i,j,1)=dt !Save dt in table
f0(i,j,1)=f !Save f in table
msg0(i,j,1)=trim(w(1))//' '//trim(w(2)) !Save "call_1 call_2"
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if(w(1)(1:3).eq.'CQ ' .and. nw(2).le.2) then
msg0(i,j,1)='CQ '//trim(w(2))//' '//trim(w(3)) !Save "CQ DX Call_2"
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endif
msg1=msg0(i,j,1) !Message without grid
nn=len(trim(msg1)) !Message length without grid
! Include grid as part of message
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if(isgrid4(w(nwords))) msg0(i,j,1)=trim(msg0(i,j,1))//' '//trim(w(nwords))
! If a transmission at this frequency with message fragment "call_1 call_2"
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! was decoded in the previous sequence, flag it as "DO NOT USE" because
! we have already decoded and subtracted that station's next transmission.
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call split77(msg0(i,j,1),nwords,nw,w) !Parse msg into words
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do i=1,ndec(j,0)
if(f0(i,j,0).le.-98.0) cycle
i2=index(msg0(i,j,0),' '//trim(w(2)))
if(abs(f-f0(i,j,0)).le.3.0 .and. i2.ge.3) then
f0(i,j,0)=-98.0 !Flag as "do not use" for a potential a7 decode
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endif
enddo
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999 return
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end subroutine ft8_a7_save
subroutine ft8_a7d(dd0,newdat,call_1,call_2,grid4,xdt,f1,xbase,nharderrors,dmin, &
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msg37,xsnr)
! Examine the raw data in dd0() for possible "a7" decodes.
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use crc
use timer_module, only: timer
use packjt77
include 'ft8_params.f90'
parameter(NP2=2812)
character*37 msg37,msg,msgsent,msgbest
character*12 call_1,call_2
character*4 grid4
real a(5)
real s8(0:7,NN)
real s2(0:511)
real dmm(206)
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real bmeta(174),bmetb(174),bmetc(174),bmetd(174)
real llra(174),llrb(174),llrc(174),llrd(174) !Soft symbols
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real dd0(15*12000)
real ss(9)
real rcw(174)
integer*1 cw(174)
integer*1 msgbits(77)
integer*1 nxor(174),hdec(174)
integer itone(NN)
integer icos7(0:6),ip(1)
logical one(0:511,0:8)
integer graymap(0:7)
integer iloc(1)
complex cd0(0:3199)
complex ctwk(32)
complex csymb(32)
complex cs(0:7,NN)
logical std_1,std_2
logical first,newdat
data icos7/3,1,4,0,6,5,2/ !Sync array
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data first/.true./
data graymap/0,1,3,2,5,6,4,7/
save one
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if(first) then
one=.false.
do i=0,511
do j=0,8
if(iand(i,2**j).ne.0) one(i,j)=.true.
enddo
enddo
first=.false.
endif
call stdcall(call_1,std_1)
if(call_1(1:3).eq.'CQ ') std_1=.true.
call stdcall(call_2,std_2)
fs2=12000.0/NDOWN
dt2=1.0/fs2
twopi=8.0*atan(1.0)
delfbest=0.
ibest=0
call timer('ft8_down',0)
call ft8_downsample(dd0,newdat,f1,cd0) !Mix f1 to baseband and downsample
call timer('ft8_down',1)
i0=nint((xdt+0.5)*fs2) !Initial guess for start of signal
smax=0.0
do idt=i0-10,i0+10 !Search over +/- one quarter symbol
call sync8d(cd0,idt,ctwk,0,sync) !NB: ctwk not used here
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if(sync.gt.smax) then
smax=sync
ibest=idt
endif
enddo
! Peak up in frequency
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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,ibest,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)
f1=f1+delfbest !Improved estimate of DF
call timer('ft8_down',0)
call ft8_downsample(dd0,.false.,f1,cd0) !Mix f1 to baseband and downsample
call timer('ft8_down',1)
smax=0.0
do idt=-4,4 !Search over +/- one quarter symbol
call sync8d(cd0,ibest+idt,ctwk,0,sync)
ss(idt+5)=sync
enddo
smax=maxval(ss)
iloc=maxloc(ss)
ibest=iloc(1)-5+ibest
xdt=(ibest-1)*dt2 - 0.5
sync=smax
do k=1,NN
i1=ibest+(k-1)*32
csymb=cmplx(0.0,0.0)
if( i1.ge.0 .and. i1+31 .le. NP2-1 ) csymb=cd0(i1:i1+31)
call four2a(csymb,32,1,-1,1)
cs(0:7,k)=csymb(1:8)/1e3
s8(0:7,k)=abs(csymb(1:8))
enddo
! sync quality check
is1=0
is2=0
is3=0
do k=1,7
ip=maxloc(s8(:,k))
if(icos7(k-1).eq.(ip(1)-1)) is1=is1+1
ip=maxloc(s8(:,k+36))
if(icos7(k-1).eq.(ip(1)-1)) is2=is2+1
ip=maxloc(s8(:,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) return ! bail out
do nsym=1,3
nt=2**(3*nsym)
do ihalf=1,2
do k=1,29,nsym
if(ihalf.eq.1) ks=k+7
if(ihalf.eq.2) ks=k+43
amax=-1.0
do i=0,nt-1
i1=i/64
i2=iand(i,63)/8
i3=iand(i,7)
if(nsym.eq.1) then
s2(i)=abs(cs(graymap(i3),ks))
elseif(nsym.eq.2) then
s2(i)=abs(cs(graymap(i2),ks)+cs(graymap(i3),ks+1))
elseif(nsym.eq.3) then
s2(i)=abs(cs(graymap(i1),ks)+cs(graymap(i2),ks+1)+cs(graymap(i3),ks+2))
else
print*,"Error - nsym must be 1, 2, or 3."
endif
enddo
i32=1+(k-1)*3+(ihalf-1)*87
if(nsym.eq.1) ibmax=2
if(nsym.eq.2) ibmax=5
if(nsym.eq.3) ibmax=8
do ib=0,ibmax
bm=maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)) - &
maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib))
if(i32+ib .gt.174) cycle
if(nsym.eq.1) then
bmeta(i32+ib)=bm
den=max(maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)), &
maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib)))
if(den.gt.0.0) then
cm=bm/den
else ! erase it
cm=0.0
endif
bmetd(i32+ib)=cm
elseif(nsym.eq.2) then
bmetb(i32+ib)=bm
elseif(nsym.eq.3) then
bmetc(i32+ib)=bm
endif
enddo
enddo
enddo
enddo
call normalizebmet(bmeta,174)
call normalizebmet(bmetb,174)
call normalizebmet(bmetc,174)
call normalizebmet(bmetd,174)
scalefac=2.83
llra=scalefac*bmeta
llrb=scalefac*bmetb
llrc=scalefac*bmetc
llrd=scalefac*bmetd
! apmag=maxval(abs(llra))*1.01
MAXMSG=206
pbest=0.
dmin=1.e30
nharderrors=-1
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do imsg=1,MAXMSG
msg=trim(call_1)//' '//trim(call_2)
i=imsg
if(call_1(1:3).eq.'CQ ' .and. i.ne.5) msg='QU1RK '//trim(call_2)
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if(.not.std_1) then
if(i.eq.1 .or. i.ge.6) msg='<'//trim(call_1)//'> '//trim(call_2)
if(i.ge.2 .and. i.le.4) msg=trim(call_1)//' <'//trim(call_2)//'>'
else if(.not.std_2) then
if(i.le.4 .or. i.eq.6) msg='<'//trim(call_1)//'> '//trim(call_2)
if(i.ge.7) msg=trim(call_1)//' <'//trim(call_2)//'>'
endif
j0=len(trim(msg))+2
if(i.eq.2) msg(j0:j0+2)='RRR'
if(i.eq.3) msg(j0:j0+3)='RR73'
if(i.eq.4) msg(j0:j0+1)='73'
if(i.eq.5) then
if(std_2) then
msg='CQ '//trim(call_2)
if(call_1(3:3).eq.'_') msg=trim(call_1)//' '//trim(call_2)
if(grid4.ne.'RR73') msg=trim(msg)//' '//grid4
endif
if(.not.std_2) msg='CQ '//trim(call_2)
endif
if(i.eq.6 .and. std_2) msg(j0:j0+3)=grid4
if(i.ge.7) then
isnr = -50 + (i-7)/2
if(iand(i,1).eq.1) then
write(msg(j0:j0+2),'(i3.2)') isnr
if(msg(j0:j0).eq.' ') msg(j0:j0)='+'
else
write(msg(j0:j0+3),'("R",i3.2)') isnr
if(msg(j0+1:j0+1).eq.' ') msg(j0+1:j0+1)='+'
endif
endif
i3=-1
n3=-1
call genft8(msg,i3,n3,msgsent,msgbits,itone) !Source-encode this message
call encode174_91(msgbits,cw) !Get codeword for this message
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rcw=2*cw-1
pow=0.0
do i=1,79
pow=pow+s8(itone(i),i)**2
enddo
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hdec=0
where(llra.ge.0.0) hdec=1
nxor=ieor(hdec,cw)
da=sum(nxor*abs(llra))
hdec=0
where(llrb.ge.0.0) hdec=1
nxor=ieor(hdec,cw)
dbb=sum(nxor*abs(llrb))
hdec=0
where(llrc.ge.0.0) hdec=1
nxor=ieor(hdec,cw)
dc=sum(nxor*abs(llrc))
hdec=0
where(llrd.ge.0.0) hdec=1
nxor=ieor(hdec,cw)
dd=sum(nxor*abs(llrd))
dm=min(da,dbb,dc,dd)
dmm(imsg)=dm
if(dm.lt.dmin) then
dmin=dm
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msgbest=msgsent
pbest=pow
if(dm.eq.da) then
nharderrors=count((2*cw-1)*llra.lt.0.0)
else if(dm.eq.dbb) then
nharderrors=count((2*cw-1)*llrb.lt.0.0)
else if(dm.eq.dc) then
nharderrors=count((2*cw-1)*llrc.lt.0.0)
else if(dm.eq.dd) then
nharderrors=count((2*cw-1)*llrd.lt.0.0)
endif
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endif
enddo ! imsg
iloc=minloc(dmm)
dmm(iloc(1))=1.e30
iloc=minloc(dmm)
dmin2=dmm(iloc(1))
xsnr=-24.
arg=pbest/xbase/3.0e6-1.0
if(arg.gt.0.0) xsnr=max(-24.0,db(arg)-27.0)
! write(41,3041) nharderrors,dmin,dmin2,dmin2/dmin,xsnr,trim(msgbest)
!3041 format(i3,2f7.1,f7.2,f7.1,1x,a)
if(dmin.gt.100.0 .or. dmin2/dmin.lt.1.3) nharderrors=-1
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msg37=msgbest
if(msg37(1:3).eq.'CQ ' .and. std_2 .and. grid4.eq.' ') nharderrors=-1
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if(msg37(1:6).eq.'QU1RK ') nharderrors=-1
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return
end subroutine ft8_a7d
end module ft8_a7