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Move decoding of synced frame into a subroutine.

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git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7100 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke 2016-09-20 20:21:24 +00:00
parent e3f1eb82f6
commit 3ceeb73fd6
2 changed files with 117 additions and 62 deletions
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109
lib/msk144decodeframe.f90 Normal file
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@ -0,0 +1,109 @@
subroutine msk144decodeframe(c,msgreceived,nsuccess)
use timer_module, only: timer
parameter (NSPM=864)
character*22 msgreceived
complex cb(42)
complex cfac,cca,ccb
complex c(NSPM)
integer*1 decoded(80)
integer s8(8),hardbits(144)
real*8 dt, df, fs, pi, twopi
real cbi(42),cbq(42)
real pp(12)
real softbits(144)
real llr(128)
logical first
data first/.true./
data s8/0,1,1,1,0,0,1,0/
save df,first,cb,fs,pi,twopi,dt,s8,pp,nmatchedfilter
if(first) then
nmatchedfilter=1
! define half-sine pulse and raised-cosine edge window
pi=4d0*datan(1d0)
twopi=8d0*datan(1d0)
fs=12000.0
dt=1.0/fs
df=fs/NFFT
do i=1,12
angle=(i-1)*pi/12.0
pp(i)=sin(angle)
enddo
! define the sync word waveforms
s8=2*s8-1
cbq(1:6)=pp(7:12)*s8(1)
cbq(7:18)=pp*s8(3)
cbq(19:30)=pp*s8(5)
cbq(31:42)=pp*s8(7)
cbi(1:12)=pp*s8(2)
cbi(13:24)=pp*s8(4)
cbi(25:36)=pp*s8(6)
cbi(37:42)=pp(1:6)*s8(8)
cb=cmplx(cbi,cbq)
first=.false.
endif
nsuccess=0
msgreceived=' '
! Estimate carrier phase.
cca=sum(c(1:1+41)*conjg(cb))
ccb=sum(c(1+56*6:1+56*6+41)*conjg(cb))
cfac=ccb*conjg(cca)
phase0=atan2(imag(cca+ccb),real(cca+ccb))
! 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(864-5:864))*pp(1:6))
softbits(2)=sum(real(c(1:12))*pp)
do i=2,72
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 as a discriminator for
! frames that have reasonable probability of decoding
hardbits=0
do i=1,144
if( softbits(i) .ge. 0.0 ) then
hardbits(i)=1
endif
enddo
nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8 ) )/2
nbadsync2=(8-sum( (2*hardbits(1+56:8+56)-1)*s8 ) )/2
nbadsync=nbadsync1+nbadsync2
if( nbadsync .gt. 4 ) then
return
endif
! normalize the softsymbols before submitting to decoder
sav=sum(softbits)/144
s2av=sum(softbits*softbits)/144
ssig=sqrt(s2av-sav*sav)
softbits=softbits/ssig
sigma=0.70
llr(1:48)=softbits(9:9+47)
llr(49:128)=softbits(65:65+80-1)
llr=2.0*llr/(sigma*sigma)
max_iterations=10
max_dither=1
call timer('bpdec144 ',0)
call bpdecode144(llr,max_iterations,decoded,niterations)
call timer('bpdec144 ',1)
if( niterations .ge. 0.0 ) then
call extractmessage144(decoded,msgreceived,nhashflag)
if( nhashflag .gt. 0 ) then ! CRCs match, so print it
nsuccess=1
endif
endif
return
end subroutine msk144decodeframe

70
lib/mskrtd.f90
View File

@ -21,24 +21,19 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
complex ct2(2*NSPM)
complex cs(NSPM)
complex cb(42) !Complex waveform for sync word
complex cfac,cca,ccb
complex cc(0:NSPM-1)
! integer*8 count0,count1,count2,count3,clkfreq
integer s8(8),hardbits(144)
integer s8(8)
integer iloc(1)
integer ipeaks(10)
integer nav(6)
integer*1 decoded(80)
real cbi(42),cbq(42)
real d(NFFT1)
real xcc(0:NSPM-1)
real xccs(0:NSPM-1)
real pp(12) !Half-sine pulse shape
real softbits(144)
real lratio(128)
real llr(128)
logical first
data first/.true./
data s8/0,1,1,1,0,0,1,0/
@ -87,7 +82,7 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
call analytic(d,NZ,NFFT1,cdat) !Convert to analytic signal and filter
nmessages=0
line=char(0)
line=' '
nshort=0
npts=7168
nsnr=-4 !### Temporary ###
@ -145,61 +140,13 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
if(is.eq.3) ic0=min(NSPM,ic0+1)
ct=cshift(c,ic0-1)
! Estimate final frequency error and carrier phase.
cca=sum(ct(1:1+41)*conjg(cb))
ccb=sum(ct(1+56*6:1+56*6+41)*conjg(cb))
cfac=ccb*conjg(cca)
! ffin=atan2(imag(cfac),real(cfac))/(twopi*56*6*dt)
phase0=atan2(imag(cca+ccb),real(cca+ccb))
call msk144decodeframe(ct,msgreceived,nsuccess)
! Remove phase error: rotate constellation so sample points lie on I/Q axes
cfac=cmplx(cos(phase0),sin(phase0))
ct=ct*conjg(cfac)
! Use matched filter
softbits(1)=sum(imag(ct(1:6))*pp(7:12)) + &
sum(imag(ct(864-5:864))*pp(1:6))
softbits(2)=sum(real(ct(1:12))*pp)
do i=2,72
softbits(2*i-1)=sum(imag(ct(1+(i-1)*12-6:1+(i-1)*12+5))*pp)
softbits(2*i)=sum(real(ct(7+(i-1)*12-6:7+(i-1)*12+5))*pp)
enddo
! Number of hard errors in sync word is a good discriminator for
! frames that have reasonable probability of decoding
hardbits=0
do i=1,144
if(softbits(i) .ge. 0.0) then
hardbits(i)=1
endif
enddo
nbadsync1=(8-sum((2*hardbits(1:8)-1)*s8))/2
nbadsync2=(8-sum((2*hardbits(1+56:8+56)-1)*s8))/2
nbadsync=nbadsync1+nbadsync2
if(nbadsync .gt. 3) cycle
! Normalize softsymbols before submitting to decoder
sav=sum(softbits)/144
s2av=sum(softbits*softbits)/144
ssig=sqrt(s2av-sav*sav)
softbits=softbits/ssig
sigma=0.70
lratio(1:48)=softbits(9:9+47)
lratio(49:128)=softbits(65:65+80-1)
llr=2.0*lratio/(sigma*sigma)
call bpdecode144(llr,max_iterations,decoded,niterations)
if(niterations .ge. 0.0) then
call extractmessage144(decoded,msgreceived,nhashflag)
if(nhashflag .gt. 0) then ! CRCs match, so print it
write(line,1020) nutc0,nsnr,tsec,nint(fest),msgreceived,char(0)
1020 format(i6.6,i4,f5.1,i5,' ^ ',a22,a1)
endif
goto 999
else
msgreceived=' '
ndither=-99 !Bad hash flag = -99
if(nsuccess .gt. 0) then
write(*,*) nsuccess,msgreceived
write(line,1020) nutc0,nsnr,tsec,nint(fest),msgreceived,char(0)
1020 format(i6.6,i4,f5.1,i5,' ^ ',a22,a1)
goto 999
endif
enddo !Slicer dither
enddo !Peak loop
@ -221,4 +168,3 @@ subroutine mskrtd(id2,nutc0,tsec,ntol,line)
return
end subroutine mskrtd