mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2024-10-01 01:26:39 -04:00
296 lines
8.6 KiB
Fortran
296 lines
8.6 KiB
Fortran
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subroutine ft4_decode(cdatetime0,nfqso,iwave,ndecodes,mycall,hiscall,nrx,line)
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use packjt77
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include 'ft4_params.f90'
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character message*37
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character c77*77
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character*61 line
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character*37 decodes(100)
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character*120 data_dir
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character*17 cdatetime0
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character*6 mycall,hiscall,hhmmss
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complex cd2(0:NMAX/16-1) !Complex waveform
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complex cb(0:NMAX/16-1)
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complex cd(0:76*20-1) !Complex waveform
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complex ctwk(80),ctwk2(80)
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complex csymb(20)
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complex cs(0:3,NN)
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real s4(0:3,NN)
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real bmeta(152),bmetb(152),bmetc(152)
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real s(NH1,NHSYM)
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real a(5)
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real llr(128),llr2(128),llra(128),llrb(128),llrc(128)
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real s2(0:255)
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real candidate(3,100)
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real savg(NH1),sbase(NH1)
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integer icos4(0:3)
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integer*2 iwave(NMAX) !Generated full-length waveform
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integer*1 message77(77),apmask(128),cw(128)
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integer*1 hbits(152)
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integer graymap(0:3)
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integer ip(1)
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logical unpk77_success
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logical one(0:511,0:7) ! 256 4-symbol sequences, 8 bits
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logical first
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data icos4/0,1,3,2/
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data graymap/0,1,3,2/
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data first/.true./
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save one
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hhmmss=cdatetime0(12:17)
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fs=12000.0/NDOWN !Sample rate
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dt=1/fs !Sample interval after downsample (s)
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tt=NSPS*dt !Duration of "itone" symbols (s)
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baud=1.0/tt !Keying rate for "itone" symbols (baud)
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txt=NZ*dt !Transmission length (s)
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twopi=8.0*atan(1.0)
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h=1.0 !h=0.8 seems to be optimum for AWGN sensitivity (not for fading)
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if(first) then
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one=.false.
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do i=0,255
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do j=0,7
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if(iand(i,2**j).ne.0) one(i,j)=.true.
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enddo
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enddo
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first=.false.
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endif
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data_dir="."
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fMHz=7.074
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candidate=0.0
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ncand=0
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nfa=375
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nfb=3000
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syncmin=1.0
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maxcand=100
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! call syncft4(iwave,nfa,nfb,syncmin,nfqso,maxcand,s,candidate,ncand,sbase)
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call getcandidates4(iwave,375.0,3000.0,0.2,2200.0,100,savg,candidate,ncand,sbase)
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ndecodes=0
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do icand=1,ncand
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f0=candidate(1,icand)-1.5*37.5
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xsnr=10*log10(candidate(3,icand))
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if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle
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call ft4_downsample(iwave,f0,cd2) ! downsample from 320 Sa/Symbol to 20 Sa/Symbol
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sum2=sum(cd2*conjg(cd2))/(20.0*76)
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if(sum2.gt.0.0) cd2=cd2/sqrt(sum2)
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! 750 samples/second here
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ibest=-1
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smax=-99.
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dfbest=-1.
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do idf=-90,+90,5
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df=idf
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a=0.
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a(1)=df
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ctwk=1.
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call twkfreq1(ctwk,80,fs,a,ctwk2)
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do istart=0,315
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call sync4d(cd2,istart,ctwk2,1,sync)
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if(sync.gt.smax) then
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smax=sync
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ibest=istart
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dfbest=df
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endif
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enddo
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enddo
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f0=f0+dfbest
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!f0=1443.75
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call ft4_downsample(iwave,f0,cb) ! downsample from 320s/Symbol to 20s/Symbol
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sum2=sum(abs(cb)**2)/(20.0*76)
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if(sum2.gt.0.0) cb=cb/sqrt(sum2)
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!ibest=208
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cd=cb(ibest:ibest+76*20-1)
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do k=1,NN
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i1=(k-1)*20
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csymb=cd(i1:i1+19)
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call four2a(csymb,20,1,-1,1)
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cs(0:3,k)=csymb(1:4)/1e2
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s4(0:3,k)=abs(csymb(1:4))
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enddo
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! sync quality check
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is1=0
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is2=0
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is3=0
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do k=1,4
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ip=maxloc(s4(:,k))
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if(icos4(k-1).eq.(ip(1)-1)) is1=is1+1
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ip=maxloc(s4(:,k+36))
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if(icos4(k-1).eq.(ip(1)-1)) is2=is2+1
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ip=maxloc(s4(:,k+72))
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if(icos4(k-1).eq.(ip(1)-1)) is3=is3+1
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enddo
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! hard sync sum - max is 12
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nsync=is1+is2+is3
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do nseq=1,3
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if(nseq.eq.1) nsym=1
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if(nseq.eq.2) nsym=2
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if(nseq.eq.3) nsym=4
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nt=2**(2*nsym)
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do ks=1,76,nsym
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amax=-1.0
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do i=0,nt-1
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i1=i/64
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i2=iand(i,63)/16
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i3=iand(i,15)/4
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i4=iand(i,3)
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if(nsym.eq.1) then
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s2(i)=abs(cs(graymap(i4),ks))
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elseif(nsym.eq.2) then
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s2(i)=abs(cs(graymap(i3),ks)+cs(graymap(i4),ks+1))
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elseif(nsym.eq.4) then
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s2(i)=abs(cs(graymap(i1),ks ) + &
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cs(graymap(i2),ks+1) + &
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cs(graymap(i3),ks+2) + &
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cs(graymap(i4),ks+3) &
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)
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else
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print*,"Error - nsym must be 1, 2, or 4."
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endif
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enddo
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ipt=1+(ks-1)*2
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if(nsym.eq.1) ibmax=1
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if(nsym.eq.2) ibmax=3
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if(nsym.eq.4) ibmax=7
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do ib=0,ibmax
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bm=maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)) - &
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maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib))
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if(ipt+ib .gt.152) cycle
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if(nsym.eq.1) then
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bmeta(ipt+ib)=bm
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elseif(nsym.eq.2) then
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bmetb(ipt+ib)=bm
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elseif(nsym.eq.4) then
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bmetc(ipt+ib)=bm
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endif
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enddo
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enddo
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enddo
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call normalizebmet(bmeta,152)
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call normalizebmet(bmetb,152)
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call normalizebmet(bmetc,152)
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hbits=0
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where(bmeta.ge.0) hbits=1
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ns1=count(hbits( 1: 8).eq.(/0,0,0,1,1,0,1,1/))
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ns2=count(hbits( 73: 80).eq.(/0,0,0,1,1,0,1,1/))
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ns3=count(hbits(145:152).eq.(/0,0,0,1,1,0,1,1/))
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nsync_qual=ns1+ns2+ns3
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sigma=0.7
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llra(1:64)=bmeta(9:72)
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llra(65:128)=bmeta(81:144)
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llra=2*llra/sigma**2
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llrb(1:64)=bmetb(9:72)
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llrb(65:128)=bmetb(81:144)
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llrb=2*llrb/sigma**2
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llrc(1:64)=bmetc(9:72)
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llrc(65:128)=bmetc(81:144)
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llrc=2*llrc/sigma**2
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do isd=1,3
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if(isd.eq.1) llr=llra
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if(isd.eq.2) llr=llrb
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if(isd.eq.3) llr=llrc
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apmask=0
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max_iterations=40
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do ibias=0,0
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llr2=llr
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if(ibias.eq.1) llr2=llr+0.4
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if(ibias.eq.2) llr2=llr-0.4
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call bpdecode128_90(llr2,apmask,max_iterations,message77,cw,nharderror,niterations)
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if(nharderror.ge.0) exit
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enddo
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if(sum(message77).eq.0) cycle
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if( nharderror.ge.0 ) then
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write(c77,'(77i1)') message77(1:77)
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call unpack77(c77,1,message,unpk77_success)
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idupe=0
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do i=1,ndecodes
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if(decodes(i).eq.message) idupe=1
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enddo
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if(idupe.eq.1) exit
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ndecodes=ndecodes+1
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decodes(ndecodes)=message
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nsnr=nint(xsnr)-15
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freq=f0
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write(line,1000) hhmmss,nsnr,ibest/750.0,nint(freq),message
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1000 format(a6,i4,f5.2,i5,' + ',1x,a37)
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open(24,file='all_ft2.txt',status='unknown',position='append')
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write(24,1002) cdatetime0,nsnr,ibest/750.0,nint(freq),message, &
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nharderror,nsync_qual,isd,niterations
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if(hhmmss.eq.' ') write(*,1002) cdatetime0,nsnr, &
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ibest/750.0,nint(freq),message,nharderror,nsync_qual,isd,niterations
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1002 format(a17,i4,f6.2,i5,' Rx ',a37,4i5)
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close(24)
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!### Temporary: assume most recent decoded message conveys "hiscall".
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i0=index(message,' ')
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if(i0.ge.3 .and. i0.le.7) then
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hiscall=message(i0+1:i0+6)
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i1=index(hiscall,' ')
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if(i1.gt.0) hiscall=hiscall(1:i1)
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endif
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nrx=-1
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if(index(message,'CQ ').eq.1) nrx=1
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if((index(message,trim(mycall)//' ').eq.1) .and. &
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(index(message,' '//trim(hiscall)//' ').ge.4)) then
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if(index(message,' 559 ').gt.8) nrx=2
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if(index(message,' R 559 ').gt.8) nrx=3
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if(index(message,' RR73 ').gt.8) nrx=4
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endif
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!###
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exit
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endif
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enddo ! sequence estimation
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enddo !candidate list
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return
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end subroutine ft4_decode
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subroutine ft4_downsample(iwave,f0,c)
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! Input: i*2 data in iwave() at sample rate 12000 Hz
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! Output: Complex data in c(), sampled at 1200 Hz
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include 'ft4_params.f90'
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parameter (NFFT2=NMAX/16)
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integer*2 iwave(NMAX)
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complex c(0:NMAX/16-1)
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complex c1(0:NFFT2-1)
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complex cx(0:NMAX/2)
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real x(NMAX)
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equivalence (x,cx)
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BW=6.0*75
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df=12000.0/NMAX
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x=iwave
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call four2a(x,NMAX,1,-1,0) !r2c FFT to freq domain
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ibw=nint(BW/df)
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i0=nint(f0/df)
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c1=0.
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c1(0)=cx(i0)
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do i=1,NFFT2/2
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arg=(i-1)*df/bw
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win=exp(-arg*arg)
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c1(i)=cx(i0+i)*win
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c1(NFFT2-i)=cx(i0-i)*win
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enddo
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c1=c1/NFFT2
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call four2a(c1,NFFT2,1,1,1) !c2c FFT back to time domain
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c=c1(0:NMAX/16-1)
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return
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end subroutine ft4_downsample
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