mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-11-16 09:01:59 -05:00
9582ccd5d5
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7441 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
164 lines
4.7 KiB
Fortran
164 lines
4.7 KiB
Fortran
subroutine msk40decodeframe(c,mycall,hiscall,xsnr,bswl,nhasharray, &
|
|
recent_calls,nrecent,msgreceived,nsuccess)
|
|
! use timer_module, only: timer
|
|
|
|
parameter (NSPM=240)
|
|
character*4 rpt(0:15)
|
|
character*6 mycall,hiscall,mycall0,hiscall0
|
|
character*22 hashmsg,msgreceived
|
|
character*12 recent_calls(nrecent)
|
|
complex cb(42)
|
|
complex cfac,cca
|
|
complex c(NSPM)
|
|
integer*1 cw(32)
|
|
integer*1 decoded(16)
|
|
integer s8r(8),hardbits(40)
|
|
integer nhasharray(nrecent,nrecent)
|
|
real*8 dt, fs, pi, twopi
|
|
real cbi(42),cbq(42)
|
|
real pp(12)
|
|
real softbits(40)
|
|
real llr(32)
|
|
logical first
|
|
logical bswl
|
|
data first/.true./
|
|
data s8r/1,0,1,1,0,0,0,1/
|
|
data mycall0/'dummy'/,hiscall0/'dummy'/
|
|
data rpt/"-03 ","+00 ","+03 ","+06 ","+10 ","+13 ","+16 ", &
|
|
"R-03","R+00","R+03","R+06","R+10","R+13","R+16", &
|
|
"RRR ","73 "/
|
|
save first,cb,fs,pi,twopi,dt,s8r,pp,rpt,mycall0,hiscall0,ihash
|
|
|
|
if(first) then
|
|
! define half-sine pulse and raised-cosine edge window
|
|
pi=4d0*datan(1d0)
|
|
twopi=8d0*datan(1d0)
|
|
fs=12000.0
|
|
dt=1.0/fs
|
|
|
|
do i=1,12
|
|
angle=(i-1)*pi/12.0
|
|
pp(i)=sin(angle)
|
|
enddo
|
|
|
|
! define the sync word waveforms
|
|
s8r=2*s8r-1
|
|
cbq(1:6)=pp(7:12)*s8r(1)
|
|
cbq(7:18)=pp*s8r(3)
|
|
cbq(19:30)=pp*s8r(5)
|
|
cbq(31:42)=pp*s8r(7)
|
|
cbi(1:12)=pp*s8r(2)
|
|
cbi(13:24)=pp*s8r(4)
|
|
cbi(25:36)=pp*s8r(6)
|
|
cbi(37:42)=pp(1:6)*s8r(8)
|
|
cb=cmplx(cbi,cbq)
|
|
first=.false.
|
|
endif
|
|
|
|
if(mycall.ne.mycall0 .or. hiscall.ne.hiscall0) then
|
|
hashmsg=trim(mycall)//' '//trim(hiscall)
|
|
call fmtmsg(hashmsg,iz)
|
|
call hash(hashmsg,22,ihash)
|
|
ihash=iand(ihash,4095)
|
|
mycall0=mycall
|
|
hiscall0=hiscall
|
|
endif
|
|
|
|
nsuccess=0
|
|
msgreceived=' '
|
|
|
|
! Estimate carrier phase.
|
|
cca=sum(c(1:1+41)*conjg(cb))
|
|
phase0=atan2(imag(cca),real(cca))
|
|
|
|
! Remove phase error - want constellation rotated so that sample points lie on I/Q axes
|
|
cfac=cmplx(cos(phase0),sin(phase0))
|
|
c=c*conjg(cfac)
|
|
|
|
! Matched filter.
|
|
softbits(1)=sum(imag(c(1:6))*pp(7:12))+sum(imag(c(NSPM-5:NSPM))*pp(1:6))
|
|
softbits(2)=sum(real(c(1:12))*pp)
|
|
do i=2,20
|
|
softbits(2*i-1)=sum(imag(c(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
|
|
softbits(2*i)=sum(real(c(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
|
|
enddo
|
|
|
|
! Sync word hard error weight is used to reject frames that
|
|
! are unlikely to decode.
|
|
hardbits=0
|
|
do i=1,40
|
|
if( softbits(i) .ge. 0.0 ) then
|
|
hardbits(i)=1
|
|
endif
|
|
enddo
|
|
nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8r ) )/2
|
|
nbadsync=nbadsync1
|
|
if( nbadsync .gt. 3 ) then
|
|
return
|
|
endif
|
|
|
|
! Normalize the softsymbols before submitting to decoder.
|
|
sav=sum(softbits)/40
|
|
s2av=sum(softbits*softbits)/40
|
|
ssig=sqrt(s2av-sav*sav)
|
|
softbits=softbits/ssig
|
|
|
|
sigma=0.75
|
|
! if(xsnr.lt.0.0) sigma=0.75-0.0875*xsnr
|
|
if(xsnr.lt.0.0) sigma=0.75-0.11*xsnr
|
|
llr(1:32)=softbits(9:40)
|
|
llr=2.0*llr/(sigma*sigma)
|
|
|
|
max_iterations=5
|
|
call bpdecode40(llr,max_iterations,decoded,niterations)
|
|
|
|
if( niterations .ge. 0.0 ) then
|
|
call encode_msk40(decoded,cw)
|
|
nhammd=0
|
|
cord=0.0
|
|
do i=1,32
|
|
if( cw(i) .ne. hardbits(i+8) ) then
|
|
nhammd=nhammd+1
|
|
cord=cord+abs(softbits(i+8))
|
|
endif
|
|
enddo
|
|
|
|
imsg=0
|
|
do i=1,16
|
|
imsg=ishft(imsg,1)+iand(1,decoded(17-i))
|
|
enddo
|
|
nrxrpt=iand(imsg,15)
|
|
nrxhash=(imsg-nrxrpt)/16
|
|
if(nhammd.le.4 .and. cord .lt. 0.65 .and. nrxhash.eq.ihash) then
|
|
!write(*,*) 'decodeframe ',nhammd,cord,nrxhash,nrxrpt,ihash,xsnr,sigma
|
|
nsuccess=1
|
|
write(msgreceived,'(a1,a,1x,a,a1,1x,a4)') "<",trim(mycall), &
|
|
trim(hiscall),">",rpt(nrxrpt)
|
|
return
|
|
elseif(bswl .and. nhammd.le.2 .and. cord.lt.0.40 .and. xsnr .gt. -3.0) then
|
|
do i=1,nrecent
|
|
do j=i+1,nrecent
|
|
if( nrxhash .eq. nhasharray(i,j) ) then
|
|
nsuccess=1
|
|
write(msgreceived,'(a1,a,1x,a,a1,1x,a4)') "<",trim(recent_calls(i)), &
|
|
trim(recent_calls(j)),">",rpt(nrxrpt)
|
|
!write(*,*) 'decodeframe ',nhammd,cord,nrxhash,nrxrpt,ihash,xsnr,sigma
|
|
elseif( nrxhash .eq. nhasharray(j,i) ) then
|
|
nsuccess=1
|
|
write(msgreceived,'(a1,a,1x,a,a1,1x,a4)') "<",trim(recent_calls(j)), &
|
|
trim(recent_calls(i)),">",rpt(nrxrpt)
|
|
!write(*,*) 'decodeframe ',nhammd,cord,nrxhash,nrxrpt,ihash,xsnr,sigma
|
|
endif
|
|
enddo
|
|
enddo
|
|
if(nsuccess.eq.0 .and. nhammd.le.2 .and. cord.lt.0.40 .and. xsnr.gt.0.0 ) then
|
|
!write(*,*) 'decodeframe ',nhammd,cord,nrxhash,nrxrpt,ihash,xsnr,sigma
|
|
nsuccess=1
|
|
write(msgreceived,'(a1,i4.4,a1,1x,a4)') "<",nrxhash,">",rpt(nrxrpt)
|
|
endif
|
|
endif
|
|
endif
|
|
|
|
return
|
|
end subroutine msk40decodeframe
|