subroutine mskrtd(id2,nutc0,tsec,ntol,nrxfreq,ndepth,mycall,hiscall, &
bshmsg,btrain,pcoeffs,bswl,datadir,line)
! Real-time decoder for MSK144.
! Analysis block size = NZ = 7168 samples, t_block = 0.597333 s
! Called from hspec() at half-block increments, about 0.3 s
use packjt77
parameter (NZ=7168) !Block size
parameter (NSPM=864) !Number of samples per message frame
parameter (NFFT1=8192) !FFT size for making analytic signal
parameter (NPATTERNS=4) !Number of frame averaging patterns to try
parameter (NSHMEM=50) !Number of recent SWL messages to remember
character*4 decsym !"&" for mskspd or "^" for long averages
character*37 msgreceived !Decoded message
character*37 msglast,msglastswl !Used for dupechecking
character*80 line !Formatted line with UTC dB T Freq Msg
character*12 mycall,hiscall
character*37 recent_shmsgs(NSHMEM)
character*(*) datadir
complex cdat(NFFT1) !Analytic signal
complex c(NSPM) !Coherently averaged complex data
complex ct(NSPM)
integer*2 id2(NZ) !Raw 16-bit data
integer iavmask(8)
integer iavpatterns(8,NPATTERNS)
integer npkloc(10)
integer nhasharray(MAXRECENT,MAXRECENT)
integer nsnrlast,nsnrlastswl
real d(NFFT1)
real pow(8)
real softbits(144)
real xmc(NPATTERNS)
real*8 pcoeffs(5)
logical*1 bshmsg,btrain,bswl
logical*1 first
logical*1 bshdecode
logical*1 seenb4
logical*1 bflag
logical*1 bvar
data first/.true./
data iavpatterns/ &
1,1,1,1,0,0,0,0, &
0,0,1,1,1,1,0,0, &
1,1,1,1,1,0,0,0, &
1,1,1,1,1,1,1,0/
data xmc/2.0,4.5,2.5,3.5/ !Used to set time at center of averaging mask
save first,tsec0,nutc00,pnoise,cdat,msglast,msglastswl, &
nsnrlast,nsnrlastswl,nhasharray,recent_shmsgs
! nsnrlast,nsnrlastswl,nhasharray,recent_shmsgs,mycall13
if(first) then
tsec0=tsec
nutc00=nutc0
pnoise=-1.0
do i=1,MAXRECENT
recent_calls(i)(1:13)=' '
enddo
do i=1,nshmem
recent_shmsgs(i)(1:37)=' '
enddo
msglast=' '
msglastswl=' '
nsnrlast=-99
nsnrlastswl=-99
mycall13=mycall//' '
dxcall13=hiscall//' '
first=.false.
endif
fc=nrxfreq
! Reset if mycall or dxcall changes
if(mycall13(1:12).ne.mycall .or. dxcall13(1:12).ne.hiscall) first=.true.
! Dupe checking setup
if(nutc00.ne.nutc0 .or. tsec.lt.tsec0) then ! reset dupe checker
msglast=' '
msglastswl=' '
nsnrlast=-99
nsnrlastswl=-99
nutc00=nutc0
endif
tframe=float(NSPM)/12000.0
line=char(0)
msgreceived=' '
max_iterations=10
niterations=0
d(1:NZ)=id2
rms=sqrt(sum(d(1:NZ)*d(1:NZ))/NZ)
if(rms.lt.1.0) go to 999
fac=1.0/rms
d(1:NZ)=fac*d(1:NZ)
d(NZ+1:NFFT1)=0.
bvar=.true.
if( btrain ) bvar=.false. ! if training, turn off rx eq
call analytic(d,NZ,NFFT1,cdat,pcoeffs,bvar)
! Calculate average power for each frame and for the entire block.
! If decode is successful, largest power will be taken as signal+noise.
! If no decode, entire-block average will be used to update noise estimate.
pmax=-99
do i=1,8
ib=(i-1)*NSPM+1
ie=ib+NSPM-1
pow(i)=real(dot_product(cdat(ib:ie),cdat(ib:ie)))*rms**2
pmax=max(pmax,pow(i))
enddo
pavg=sum(pow)/8.0
! Short ping decoder uses squared-signal spectrum to determine where to
! center a 3-frame analysis window and attempts to decode each of the
! 3 frames along with 2- and 3-frame averages.
np=8*NSPM
call msk144spd(cdat,np,ntol,ndecodesuccess,msgreceived,fc,fest,tdec,navg,ct, &
softbits)
bshdecode=.false.
if(ndecodesuccess.eq.0 .and. (bshmsg.or.bswl)) then
call msk40spd(cdat,np,ntol,mycall,hiscall,bswl,nhasharray, &
ndecodesuccess,msgreceived,fc,fest,tdec,navg)
if(ndecodesuccess .ge.1) bshdecode=.true.
endif
if( ndecodesuccess .ge. 1 ) then
tdec=tsec+tdec
ipk=0
is=0
goto 900
endif
! If short ping decoder doesn't find a decode,
! Fast - short ping decoder only.
! Normal - try 4-frame averages
! Deep - try 4-, 5- and 7-frame averages.
npat=NPATTERNS
if( ndepth .eq. 1 ) npat=0
if( ndepth .eq. 2 ) npat=2
do iavg=1,npat
iavmask=iavpatterns(1:8,iavg)
navg=sum(iavmask)
deltaf=10.0/real(navg) ! search increment for frequency sync
npeaks=2
call msk144sync(cdat(1:8*NSPM),8,ntol,deltaf,iavmask,npeaks,fc, &
fest,npkloc,nsyncsuccess,xmax,c)
if( nsyncsuccess .eq. 0 ) cycle
do ipk=1,npeaks
do is=1,3
ic0=npkloc(ipk)
if(is.eq.2) ic0=max(1,ic0-1)
if(is.eq.3) ic0=min(NSPM,ic0+1)
ct=cshift(c,ic0-1)
call msk144decodeframe(ct,softbits,msgreceived,ndecodesuccess)
if(ndecodesuccess .gt. 0) then
tdec=tsec+xmc(iavg)*tframe
goto 900
endif
enddo !Slicer dither
enddo !Peak loop
enddo
msgreceived=' '
! no decode - update noise level used for calculating displayed snr.
if( pnoise .lt. 0 ) then ! initialize noise level
pnoise=pavg
elseif( pavg .gt. pnoise ) then ! noise level is slow to rise
pnoise=0.9*pnoise+0.1*pavg
elseif( pavg .lt. pnoise ) then ! and quick to fall
pnoise=pavg
endif
go to 999
900 continue
! Successful decode - estimate snr
if( pnoise .gt. 0.0 ) then
snr0=10.0*log10(pmax/pnoise-1.0)
else
snr0=0.0
endif
nsnr=nint(snr0)
if(.not. bshdecode) then
call msk144signalquality(ct,snr0,fest,tdec,softbits,msgreceived,hiscall, &
btrain,datadir,ncorrected,eyeopening,pcoeffs)
endif
decsym=' & '
if( btrain ) decsym=' ^ '
if( bshdecode ) then
ncorrected=0
eyeopening=0.0
endif
if( nsnr .lt. -8 ) nsnr=-8
if( nsnr .gt. 24 ) nsnr=24
! Dupe check.
bflag=ndecodesuccess.eq.1 .and. &
(msgreceived.ne.msglast .or. nsnr.gt.nsnrlast .or. tsec.lt.tsec0)
if(bflag) then
msglast=msgreceived
nsnrlast=nsnr
if(.not. bshdecode) then
call update_msk40_hasharray(nhasharray)
endif
write(line,1021) nutc0,nsnr,tdec,nint(fest),decsym,msgreceived,char(0)
1021 format(i6.6,i4,f5.1,i5,a4,a37,a1)
elseif(bswl .and. ndecodesuccess.ge.2) then
seenb4=.false.
do i=1,nshmem
if( msgreceived .eq. recent_shmsgs(i) ) then
seenb4=.true.
endif
enddo
call update_recent_shmsgs(msgreceived,recent_shmsgs,nshmem)
bflag=seenb4 .and. &
(msgreceived.ne.msglastswl .or. nsnr.gt.nsnrlastswl .or. tsec.lt.tsec0) &
.and. nsnr.gt.-6
if(bflag) then
msglastswl=msgreceived
nsnrlastswl=nsnr
write(line,1021) nutc0,nsnr,tdec,nint(fest),decsym,msgreceived,char(0)
endif
endif
999 tsec0=tsec
return
end subroutine mskrtd
subroutine update_recent_shmsgs(message,msgs,nsize)
character*37 msgs(nsize)
character*37 message
logical*1 seen
seen=.false.
do i=1,nsize
if( msgs(i) .eq. message ) seen=.true.
enddo
if( .not. seen ) then
do i=nsize,2,-1
msgs(i)=msgs(i-1)
enddo
msgs(1)=message
endif
return
end subroutine update_recent_shmsgs