subroutine ft4_decode(cdatetime0,tbuf,nfa,nfb,nfqso,iwave,ndecodes,mycall, & hiscall,nrx,line) use packjt77 include 'ft4_params.f90' parameter (NSS=NSPS/NDOWN) character message*37 character c77*77 character*61 line,linex(100) character*37 decodes(100) character*120 data_dir character*17 cdatetime0 character*6 mycall,hiscall,hhmmss complex cd2(0:NMAX/NDOWN-1) !Complex waveform complex cb(0:NMAX/NDOWN-1) complex cd(0:NN*NSS-1) !Complex waveform complex ctwk(4*NSS),ctwk2(4*NSS) complex csymb(NSS) complex cs(0:3,NN) real s4(0:3,NN) real bmeta(2*NN),bmetb(2*NN),bmetc(2*NN) real a(5) real llr(2*ND),llr2(2*ND),llra(2*ND),llrb(2*ND),llrc(2*ND) real s2(0:255) real candidate(3,100) real savg(NH1),sbase(NH1) integer nrxx(100) integer icos4(0:3) integer*2 iwave(NMAX) !Generated full-length waveform integer*1 message77(77),apmask(2*ND),cw(2*ND) integer*1 hbits(2*NN) integer graymap(0:3) integer ip(1) logical unpk77_success logical one(0:255,0:7) ! 256 4-symbol sequences, 8 bits logical first data icos4/0,1,3,2/ data graymap/0,1,3,2/ data first/.true./ save one,first,nrxx,linex hhmmss=cdatetime0(8:13) fs=12000.0/NDOWN !Sample rate after downsampling dt=1/fs !Sample interval after downsample (s) tt=NSPS*dt !Duration of "itone" symbols (s) txt=NZ*dt !Transmission length (s) without ramp up/down twopi=8.0*atan(1.0) h=1.0 if(first) then one=.false. do i=0,255 do j=0,7 if(iand(i,2**j).ne.0) one(i,j)=.true. enddo enddo first=.false. endif candidate=0.0 ncand=0 syncmin=1.2 maxcand=100 ! ### This is temporary. Correct directory should be passed in as an argument. data_dir="." fa=nfa fb=nfb call getcandidates4(iwave,fa,fb,syncmin,nfqso,maxcand,savg,candidate, & ncand,sbase) ndecodes=0 do icand=1,ncand f0=candidate(1,icand) xsnr=10*log10(candidate(3,icand))-18.0 if( f0.le.375.0 .or. f0.ge.(5000.0-375.0) ) cycle call ft4_downsample(iwave,f0,cd2) ! downsample from 512 Sa/Symbol to 32 Sa/Symbol sum2=sum(cd2*conjg(cd2))/(real(NMAX)/real(NDOWN)) if(sum2.gt.0.0) cd2=cd2/sqrt(sum2) ! Sample rate is now 12000/16 = 750 samples/second do isync=1,2 if(isync.eq.1) then idfmin=-50 idfmax=50 idfstp=3 ibmin=0 ibmax=374 ibstp=4 else idfmin=idfbest-5 idfmax=idfbest+5 idfstp=1 ibmin=max(0,ibest-5) ibmax=min(ibest+5,NMAX/NDOWN-1) ibstp=1 endif ibest=-1 smax=-99. idfbest=0 do idf=idfmin,idfmax,idfstp a=0. a(1)=real(idf) ctwk=1. call twkfreq1(ctwk,4*NSS,fs,a,ctwk2) do istart=ibmin,ibmax,ibstp call sync4d(cd2,istart,ctwk2,1,sync) !Find sync power if(sync.gt.smax) then smax=sync ibest=istart idfbest=idf endif enddo enddo enddo f0=f0+real(idfbest) call ft4_downsample(iwave,f0,cb) !Final downsample with corrected f0 sum2=sum(abs(cb)**2)/(real(NSS)*NN) if(sum2.gt.0.0) cb=cb/sqrt(sum2) cd=cb(ibest:ibest+NN*NSS-1) do k=1,NN i1=(k-1)*NSS csymb=cd(i1:i1+NSS-1) call four2a(csymb,NSS,1,-1,1) cs(0:3,k)=csymb(1:4) s4(0:3,k)=abs(csymb(1:4)) enddo ! Sync quality check is1=0 is2=0 is3=0 is4=0 do k=1,4 ip=maxloc(s4(:,k)) if(icos4(k-1).eq.(ip(1)-1)) is1=is1+1 ip=maxloc(s4(:,k+33)) if(icos4(k-1).eq.(ip(1)-1)) is2=is2+1 ip=maxloc(s4(:,k+66)) if(icos4(k-1).eq.(ip(1)-1)) is3=is3+1 ip=maxloc(s4(:,k+99)) if(icos4(k-1).eq.(ip(1)-1)) is4=is4+1 enddo nsync=is1+is2+is3+is4 !Number of hard sync errors, 0-16 if(smax .lt. 0.9 .or. nsync .lt. 9) cycle do nseq=1,3 !Try coherent sequences of 1, 2, and 4 symbols if(nseq.eq.1) nsym=1 if(nseq.eq.2) nsym=2 if(nseq.eq.3) nsym=4 nt=2**(2*nsym) do ks=1,NN-nsym+1,nsym !87+16=103 symbols. amax=-1.0 do i=0,nt-1 i1=i/64 i2=iand(i,63)/16 i3=iand(i,15)/4 i4=iand(i,3) if(nsym.eq.1) then s2(i)=abs(cs(graymap(i4),ks)) elseif(nsym.eq.2) then s2(i)=abs(cs(graymap(i3),ks)+cs(graymap(i4),ks+1)) elseif(nsym.eq.4) then s2(i)=abs(cs(graymap(i1),ks ) + & cs(graymap(i2),ks+1) + & cs(graymap(i3),ks+2) + & cs(graymap(i4),ks+3) & ) else print*,"Error - nsym must be 1, 2, or 4." endif enddo ipt=1+(ks-1)*2 if(nsym.eq.1) ibmax=1 if(nsym.eq.2) ibmax=3 if(nsym.eq.4) ibmax=7 do ib=0,ibmax bm=maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)) - & maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib)) if(ipt+ib.gt.2*NN) cycle if(nsym.eq.1) then bmeta(ipt+ib)=bm elseif(nsym.eq.2) then bmetb(ipt+ib)=bm elseif(nsym.eq.4) then bmetc(ipt+ib)=bm endif enddo enddo enddo call normalizebmet(bmeta,2*NN) call normalizebmet(bmetb,2*NN) call normalizebmet(bmetc,2*NN) hbits=0 where(bmeta.ge.0) hbits=1 ns1=count(hbits( 1: 8).eq.(/0,0,0,1,1,0,1,1/)) ns2=count(hbits( 67: 74).eq.(/0,0,0,1,1,0,1,1/)) ns3=count(hbits(133:140).eq.(/0,0,0,1,1,0,1,1/)) ns4=count(hbits(199:206).eq.(/0,0,0,1,1,0,1,1/)) nsync_qual=ns1+ns2+ns3+ns4 if(nsync_qual.lt. 20) cycle scalefac=2.83 llra( 1: 58)=bmeta( 9: 66) llra( 59:116)=bmeta( 75:132) llra(117:174)=bmeta(141:198) llra=scalefac*llra llrb( 1: 58)=bmetb( 9: 66) llrb( 59:116)=bmetb( 75:132) llrb(117:174)=bmetb(141:198) llrb=scalefac*llrb llrc( 1: 58)=bmetc( 9: 66) llrc( 59:116)=bmetc( 75:132) llrc(117:174)=bmetc(141:198) llrc=scalefac*llrc do isd=1,3 if(isd.eq.1) llr=llra if(isd.eq.2) llr=llrb if(isd.eq.3) llr=llrc apmask=0 max_iterations=40 do ibias=0,0 llr2=llr if(ibias.eq.1) llr2=llr+0.4 if(ibias.eq.2) llr2=llr-0.4 call bpdecode174_91(llr2,apmask,max_iterations,message77, & cw,nharderror,niterations) if(nharderror.ge.0) exit enddo if(sum(message77).eq.0) cycle if( nharderror.ge.0 ) then write(c77,'(77i1)') message77(1:77) call unpack77(c77,1,message,unpk77_success) idupe=0 do i=1,ndecodes if(decodes(i).eq.message) idupe=1 enddo if(idupe.eq.1) exit ndecodes=ndecodes+1 decodes(ndecodes)=message nsnr=nint(xsnr) freq=f0 tsig=mod(tbuf + ibest/750.0,100.0) write(line,1000) hhmmss,nsnr,tsig,nint(freq),message 1000 format(a6,i4,f5.1,i5,' + ',1x,a37) open(24,file='all_ft4.txt',status='unknown',position='append') write(24,1002) cdatetime0,nsnr,tsig,nint(freq),message, & nharderror,nsync_qual,isd,niterations if(hhmmss.eq.' ') write(*,1002) cdatetime0,nsnr, & tsig,nint(freq),message,nharderror,nsync_qual,isd, & niterations 1002 format(a17,i4,f5.1,i5,' Rx ',a37,4i5) close(24) linex(ndecodes)=line !### Temporary: assume most recent decoded message conveys "hiscall". ### i0=index(message,' ') if(i0.ge.3 .and. i0.le.7) then hiscall=message(i0+1:i0+6) i1=index(hiscall,' ') if(i1.gt.0) hiscall=hiscall(1:i1) endif nrx=-1 if(index(message,'CQ ').eq.1) nrx=1 if((index(message,trim(mycall)//' ').eq.1) .and. & (index(message,' '//trim(hiscall)//' ').ge.4)) then if(index(message,' 559 ').gt.8) nrx=2 !### Not right ! if(index(message,' R 559 ').gt.8) nrx=3 !### Not right ! if(index(message,' RR73 ').gt.8) nrx=4 endif nrxx(ndecodes)=nrx !### exit endif enddo !Sequence estimation enddo !Candidate list return entry get_ft4msg(idecode,nrx,line) line=linex(idecode) nrx=nrxx(idecode) return end subroutine ft4_decode subroutine ft4_downsample(iwave,f0,c) ! Input: i*2 data in iwave() at sample rate 12000 Hz ! Output: Complex data in c(), sampled at 1200 Hz include 'ft4_params.f90' parameter (NFFT2=NMAX/16) integer*2 iwave(NMAX) complex c(0:NMAX/NDOWN-1) complex c1(0:NFFT2-1) complex cx(0:NMAX/2) real x(NMAX), window(0:NFFT2-1) equivalence (x,cx) logical first data first/.true./ save first,window df=12000.0/NMAX baud=12000.0/NSPS if(first) then bw_transition = 0.5*baud bw_flat = 4*baud iwt = bw_transition / df iwf = bw_flat / df pi=4.0*atan(1.0) window(0:iwt-1) = 0.5*(1+cos(pi*(/(i,i=iwt-1,0,-1)/)/iwt)) window(iwt:iwt+iwf-1)=1.0 window(iwt+iwf:2*iwt+iwf-1) = 0.5*(1+cos(pi*(/(i,i=0,iwt)/)/iwt)) window(2*iwt+iwf:)=0.0 iws = baud / df window=cshift(window,iws) first=.false. endif x=iwave call four2a(x,NMAX,1,-1,0) !r2c FFT to freq domain i0=nint(f0/df) c1=0. c1(0)=cx(i0) do i=1,NFFT2/2 if(i0+i.le.NMAX/2) c1(i)=cx(i0+i) if(i0-i.ge.0) c1(NFFT2-i)=cx(i0-i) enddo c1=c1*window/NFFT2 call four2a(c1,NFFT2,1,1,1) !c2c FFT back to time domain c=c1(0:NMAX/NDOWN-1) return end subroutine ft4_downsample