WSJT-X/lib/fsk4hf/wspr5d.f90

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6.6 KiB
Fortran
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program wspr5d
! Decode WSPR-LF data read from *.c5 or *.wav files.
! WSPR-LF is a potential WSPR-like mode intended for use at LF and MF.
! It uses an LDPC (300,60) code, OQPSK modulation, and 5 minute T/R sequences.
! Reception and Demodulation algorithm:
! 1. Compute coarse spectrum; find fc1 = approx carrier freq
! 2. Mix from fc1 to 0; LPF at +/- 0.75*R
! 3. Square, FFT; find peaks near -R/2 and +R/2 to get fc2
! 4. Mix from fc2 to 0
! 5. Fit cb13 (central part of csync) to c -> lag, phase
! 6. Fit complex ploynomial for channel equalization
! 7. Get soft bits from equalized data
! Still to do: find and decode more than one signal in the specified passband.
include 'wsprlf_params.f90'
parameter (NMAX=300*12000)
character arg*8,message*22,cbits*50,infile*80,fname*16,datetime*11
character*120 data_dir
complex csync(0:NZ-1) !Sync symbols only, from cbb
complex c(0:NZ-1) !Complex waveform
complex c1(0:NZ-1) !Complex waveform
complex zz(NS+ND) !Complex symbol values (intermediate)
complex z
real*8 fMHz
real rxdata(ND),llr(ND) !Soft symbols
real pp(2*NSPS) !Shaped pulse for OQPSK
real a(5) !For twkfreq1
real aa(20),bb(20) !Fitted polyco's
real fpks(20)
integer id(NS+ND) !NRZ values (+/-1) for Sync and Data
integer ierror(NS+ND)
integer isync(48) !Long sync vector
integer ib13(13) !Barker 13 code
integer ihdr(11)
integer*8 n8
integer*2 iwave(NMAX) !Generated full-length waveform
integer*1 idat(7)
integer*1 decoded(KK),apmask(ND),cw(ND)
data ib13/1,1,1,1,1,-1,-1,1,1,-1,1,-1,1/
nargs=iargc()
if(nargs.lt.2) then
print*,'Usage: wspr5d [-a <data_dir>] [-f fMHz] file1 [file2 ...]'
go to 999
endif
iarg=1
data_dir="."
call getarg(iarg,arg)
if(arg(1:2).eq.'-a') then
call getarg(iarg+1,data_dir)
iarg=iarg+2
endif
call getarg(iarg,arg)
if(arg(1:2).eq.'-f') then
call getarg(iarg+1,arg)
read(arg,*) fMHz
iarg=iarg+2
endif
open(13,file=trim(data_dir)//'/ALL_WSPR.TXT',status='unknown', &
position='append')
! maxn=4 !Default value
maxn=2
twopi=8.0*atan(1.0)
fs=NSPS*12000.0/NSPS0 !Sample rate
dt=1.0/fs !Sample interval (s)
tt=NSPS*dt !Duration of "itone" symbols (s)
ts=2*NSPS*dt !Duration of OQPSK symbols (s)
baud=1.0/tt !Keying rate for "itone" symbols (baud)
txt=NZ*dt !Transmission length (s)
do i=1,N2 !Half-sine pulse shape
pp(i)=sin(0.5*(i-1)*twopi/(2*NSPS))
enddo
n8=z'cbf089223a51'
do i=1,48
isync(i)=-1
if(iand(n8,1).eq.1) isync(i)=1
n8=n8/2
enddo
! Define array id() for sync symbols
id=0
do j=1,48 !First group of 48
id(2*j-1)=2*isync(j)
enddo
do j=1,13 !Barker 13 code
id(j+96)=2*ib13(j)
enddo
do j=1,48 !Second group of 48
id(2*j+109)=2*isync(j)
enddo
csync=0.
do j=1,205
if(abs(id(j)).eq.2) then
ia=nint((j-0.5)*N2)
ib=ia+N2-1
csync(ia:ib)=pp*id(j)/abs(id(j))
endif
enddo
write(*,*) 'iarg, nargs ',iarg,nargs
do ifile=iarg,nargs
call getarg(ifile,infile)
open(10,file=infile,status='old',access='stream')
j1=index(infile,'.c5')
j2=index(infile,'.wav')
if(j1.gt.0) then
read(10,end=999) fname,ntrmin,fMHz,c
read(fname(8:11),*) nutc
write(datetime,'(i11)') nutc
else if(j2.gt.0) then
read(10,end=999) ihdr,iwave
read(infile(j2-4:j2-1),*) nutc
datetime=infile(j2-11:j2-1)
call wspr5_downsample(iwave,c)
else
print*,'Wrong file format?'
go to 999
endif
close(10)
fa=100.0
fb=150.0
call getfc1w(c,fs,fa,fb,fc1,xsnr) !First approx for freq
npeaks=20
call getfc2w(c,csync,npeaks,fs,fc1,fpks) !Refined freq
a(1)=-fc1
a(2:5)=0.
call twkfreq1(c,NZ,fs,a,c) !Mix c down by fc1+fc2
! Find time offset xdt
amax=0.
jpk=0
iaa=0
ibb=NZ-1
jmax=1260
do j=-jmax,jmax,NSPS/8
ia=j
ib=NZ-1+j
if(ia.lt.0) then
ia=0
iaa=-j
else
iaa=0
endif
if(ib.gt.NZ-1) then
ib=NZ-1
ibb=NZ-1-j
endif
z=sum(c(ia:ib)*conjg(csync(iaa:ibb)))
if(abs(z).gt.amax) then
amax=abs(z)
jpk=j
endif
enddo
xdt=jpk/fs
xdt=1.0
jpk=fs*xdt
do i=0,NZ-1
j=i+jpk
if(j.ge.0 .and. j.lt.NZ) c1(i)=c(j)
enddo
nterms=maxn
do itry=1,npeaks
nhard0=0
nhardsync0=0
ifer=1
a(1)=-fpks(itry)
a(2:5)=0.
call twkfreq1(c1,NZ,fs,a,c) !Mix c1 into c
call cpolyfitw(c,pp,id,maxn,aa,bb,zz,nhs)
call msksoftsymw(zz,aa,bb,id,nterms,ierror,rxdata,nhard0,nhardsync0)
if(nhardsync0.gt.35) cycle
rxav=sum(rxdata)/ND
rx2av=sum(rxdata*rxdata)/ND
rxsig=sqrt(rx2av-rxav*rxav)
rxdata=rxdata/rxsig
ss=0.84
llr=2.0*rxdata/(ss*ss)
apmask=0
max_iterations=40
ifer=0
call bpdecode300(llr,apmask,max_iterations,decoded,niterations,cw)
nhardmin=0
if(niterations.lt.0) call osd300(llr,apmask,5,decoded,cw,nhardmin,dmin)
nbadcrc=0
call chkcrc10(decoded,nbadcrc)
if(nbadcrc.ne.0) ifer=1
if(ifer.eq.0) exit
enddo !Freq dither loop
message=' '
if(ifer.eq.0) then
write(cbits,1100) decoded(1:50)
1100 format(50i1)
read(cbits,1102) idat
1102 format(6b8,b2)
idat(7)=ishft(idat(7),6)
call wqdecode(idat,message,itype)
nsnr=nint(xsnr)
! freq=fMHz + 1.d-6*(fc1+fc2)
! freq=fMHz + 1.d-6*(fc1+fpks(itry))
freq=fc1+fpks(itry)
nfdot=0
write(13,1110) datetime,0,nsnr,xdt,freq,message,nfdot
1110 format(a11,2i4,f6.2,f12.7,2x,a22,i3)
write(*,1112) datetime(8:11),nsnr,xdt,freq,nfdot,message,itry,nhardmin
!1112 format(a4,i4,f5.1,f11.6,i3,2x,a22,i4)
1112 format(a4,i4,f8.3,f8.3,i3,2x,a22,i4,i4)
endif
enddo ! ifile loop
write(*,1120)
1120 format("<DecodeFinished>")
999 end program wspr5d