subroutine detectmsk32(cbig,n,mycall,partnercall,lines,nmessages,nutc,ntol) use timer_module, only: timer parameter (NSPM=192, NPTS=3*NSPM, MAXSTEPS=7500, NFFT=3*NSPM, MAXCAND=40) character*4 rpt(0:31) character*6 mycall,partnercall character*22 msg,hashmsg,msgreceived,allmessages(20) character*80 lines(100) complex cbig(n) complex cdat(NPTS) !Analytic signal complex cdat2(NPTS) complex c(NSPM) complex ctmp(NFFT) complex cb(42) !Complex waveform for sync word complex cbr(42) !Complex waveform for reversed sync word complex cfac,cca,ccb complex cc(NPTS) complex ccr(NPTS) complex cc1(NPTS) complex cc2(NPTS) complex ccr1(NPTS) complex ccr2(NPTS) complex bb(6) integer s8(8),s8r(8),hardbits(32) integer, dimension(1) :: iloc integer ihammd(0:4096-1) integer indices(MAXSTEPS) integer ipeaks(10) integer ig24(0:4096-1) integer likelymessages(0:31) logical qsocontext logical ismask(NFFT) real cbi(42),cbq(42) real cd(0:4095) real detmet(-2:MAXSTEPS+3) real detfer(MAXSTEPS) real rcw(12) real dd(NPTS) real ddr(NPTS) real ferrs(MAXCAND) real pp(12) !Half-sine pulse shape real snrs(MAXCAND) real times(MAXCAND) real tonespec(NFFT) real*8 dt, df, fs, pi, twopi real softbits(32) logical first data first/.true./ data s8/0,1,1,1,0,0,1,0/ data s8r/1,0,1,1,0,0,0,1/ data rpt /'-04 ','-02 ','+00 ','+02 ','+04 ','+06 ','+08 ','+10 ','+12 ', & '+14 ','+16 ','+18 ','+20 ','+22 ','+24 ', & 'R-04','R-02','R+00','R+02','R+04','R+06','R+08','R+10','R+12', & 'R+14','R+16','R+18','R+20','R+22','R+24', & 'RRR ','73 '/ save df,first,cb,cbr,fs,pi,twopi,dt,s8,rcw,pp,nmatchedfilter,ig24 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) rcw(i)=(1-cos(angle))/2 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) s8r=2*s8r-1 cbq(1:6)=pp(7:12)*s8r(1) cbq(7:18)=pp*s8r(3) cbq(19:30)=pp*s8r(5) cbq(31:42)=pp*s8r(7) cbi(1:12)=pp*s8r(2) cbi(13:24)=pp*s8r(4) cbi(25:36)=pp*s8r(6) cbi(37:42)=pp(1:6)*s8r(8) cbr=cmplx(cbi,cbq) call golay24_table(ig24) first=.false. endif ! Define the 32 likely messages do irpt=0,31 hashmsg=trim(mycall)//' '//trim(partnercall)//' '//rpt(irpt) call fmtmsg(hashmsg,iz) call hash(hashmsg,22,ihash) ihash=iand(ihash,127) ig=32*ihash + irpt likelymessages(irpt)=ig ! write(*,*) irpt,hashmsg,ig,ig24(ig) enddo qsocontext=.false. ! Fill the detmet, detferr arrays nstepsize=48 ! 4ms steps nstep=(n-NPTS)/nstepsize detmet=0 detmax=-999.99 detfer=-999.99 do istp=1,nstep ns=1+nstepsize*(istp-1) ne=ns+NPTS-1 if( ne .gt. n ) exit ctmp=cmplx(0.0,0.0) ctmp(1:NPTS)=cbig(ns:ne) ! Coarse carrier frequency sync - seek tones at 2000 Hz and 4000 Hz in ! squared signal spectrum. ! search range for coarse frequency error is +/- 100 Hz ctmp=ctmp**2 ctmp(1:12)=ctmp(1:12)*rcw ctmp(NPTS-11:NPTS)=ctmp(NPTS-11:NPTS)*rcw(12:1:-1) call four2a(ctmp,NFFT,1,-1,1) tonespec=abs(ctmp)**2 ihlo=(4000-2*ntol)/df+1 ihhi=(4000+2*ntol)/df+1 ismask=.false. ismask(ihlo:ihhi)=.true. ! high tone search window iloc=maxloc(tonespec,ismask) ihpk=iloc(1) deltah=-real( (ctmp(ihpk-1)-ctmp(ihpk+1)) / (2*ctmp(ihpk)-ctmp(ihpk-1)-ctmp(ihpk+1)) ) ah=tonespec(ihpk) illo=(2000-2*ntol)/df+1 ilhi=(2000+2*ntol)/df+1 ismask=.false. ismask(illo:ilhi)=.true. ! window for low tone iloc=maxloc(tonespec,ismask) ilpk=iloc(1) deltal=-real( (ctmp(ilpk-1)-ctmp(ilpk+1)) / (2*ctmp(ilpk)-ctmp(ilpk-1)-ctmp(ilpk+1)) ) al=tonespec(ilpk) fdiff=(ihpk+deltah-ilpk-deltal)*df i2000=2000/df+1 i4000=4000/df+1 ferrh=(ihpk+deltah-i4000)*df/2.0 ferrl=(ilpk+deltal-i2000)*df/2.0 if( ah .ge. al ) then ferr=ferrh else ferr=ferrl endif detmet(istp)=max(ah,al) detfer(istp)=ferr ! write(*,*) istp,ilpk,ihpk,ah,al enddo ! end of detection-metric and frequency error estimation loop call indexx(detmet(1:nstep),nstep,indices) !find median of detection metric vector ! xmed=detmet(indices(nstep/2)) xmed=detmet(indices(nstep/4)) detmet=detmet/xmed ! noise floor of detection metric is 1.0 ndet=0 !do i=1,nstep !write(77,*) i,detmet(i),detfer(i) !enddo do ip=1,MAXCAND ! use something like the "clean" algorithm to find candidates iloc=maxloc(detmet(1:nstep)) il=iloc(1) if( (detmet(il) .lt. 4.2) ) exit if( abs(detfer(il)) .le. ntol ) then ndet=ndet+1 times(ndet)=((il-1)*nstepsize+NPTS/2)*dt ferrs(ndet)=detfer(il) snrs(ndet)=12.0*log10(detmet(il)-1)/2-8.0 endif detmet(max(1,il-3):min(nstep,il+3))=0.0 ! detmet(il)=0.0 enddo ! do ip=1,ndet ! write(*,*) ip,times(ip),snrs(ip),ferrs(ip) ! enddo nmessages=0 allmessages=char(0) lines=char(0) imsgbest=-1 nbadsyncbest=99 nhammdbest=99 cdbest=1e32 cdratbest=0.0 do ip=1,ndet !run through the candidates and try to sync/demod/decode imid=times(ip)*fs if( imid .lt. NPTS/2 ) imid=NPTS/2 if( imid .gt. n-NPTS/2 ) imid=n-NPTS/2 t0=times(ip) cdat=cbig(imid-NPTS/2+1:imid+NPTS/2) ferr=ferrs(ip) nsnr=2*nint(snrs(ip)/2.0) if( nsnr .lt. -4 ) nsnr=-4 if( nsnr .gt. 24 ) nsnr=24 ! remove coarse freq error - should now be within a few Hz call tweak1(cdat,NPTS,-(1500+ferr),cdat) ! attempt frame synchronization ! correlate with sync word waveforms ccr=0 ccr1=0 ccr2=0 do i=1,NPTS-(32*6+41) ccr1(i)=sum(cdat(i:i+41)*conjg(cbr)) ccr2(i)=sum(cdat(i+32*6:i+32*6+41)*conjg(cbr)) enddo ccr=ccr1+ccr2 ddr=abs(ccr1)*abs(ccr2) crmax=maxval(abs(ccr)) ! Find 6 largest peaks do ipk=1,6 iloc=maxloc(abs(ccr)) ic1=iloc(1) iloc=maxloc(ddr) ic2=iloc(1) ipeaks(ipk)=ic1 ccr(max(1,ic1-7):min(NPTS-32*6-41,ic1+7))=0.0 enddo do ipk=1,3 ! we want ic to be the index of the first sample of the frame ic0=ipeaks(ipk) ! fine adjustment of sync index do i=1,6 if( ic0+11+NSPM .le. NPTS ) then bb(i) = sum( ( cdat(ic0+i-1+6:ic0+i-1+6+NSPM:6) * conjg( cdat(ic0+i-1:ic0+i-1+NSPM:6) ) )**2 ) else bb(i) = sum( ( cdat(ic0+i-1+6:NPTS:6) * conjg( cdat(ic0+i-1:NPTS-6:6) ) )**2 ) endif enddo iloc=maxloc(abs(bb)) ibb=iloc(1) bba=abs(bb(ibb)) bbp=atan2(-imag(bb(ibb)),-real(bb(ibb)))/(2*twopi*6*dt) if( ibb .le. 3 ) ibb=ibb-1 if( ibb .gt. 3 ) ibb=ibb-7 do id=1,1 ! slicer dither. if( id .eq. 1 ) is=0 if( id .eq. 2 ) is=-1 if( id .eq. 3 ) is=1 ! Adjust frame index to place peak of bb at desired lag ic=ic0+ibb+is if( ic .lt. 1 ) ic=ic+NSPM ! Estimate fine frequency error. cca=sum(cdat(ic:ic+41)*conjg(cb)) if( ic+32*6+41 .le. NPTS ) then ccb=sum(cdat(ic+32*6:ic+32*6+41)*conjg(cb)) cfac=ccb*conjg(cca) ferr2=atan2(imag(cfac),real(cfac))/(twopi*32*6*dt) else ccb=sum(cdat(ic-32*6:ic-32*6+41)*conjg(cb)) cfac=cca*conjg(ccb) ferr2=atan2(imag(cfac),real(cfac))/(twopi*32*6*dt) endif ! Final estimate of the carrier frequency - returned to the calling program fest=1500+ferr+ferr2 do idf=0,6 ! frequency jitter if( idf .eq. 0 ) then deltaf=0.0 elseif( mod(idf,2) .eq. 0 ) then deltaf=2*idf else deltaf=-2*(idf+1) endif ! Remove fine frequency error call tweak1(cdat,NPTS,-(ferr2+deltaf),cdat2) ! place the beginning of frame at index NSPM+1 cdat2=cshift(cdat2,ic-(NSPM+1)) do iav=1,4 ! Frame averaging patterns if( iav .eq. 1 ) then c=cdat2(NSPM+1:2*NSPM) elseif( iav .eq. 2 ) then c=cdat2(1:NSPM)+cdat2(NSPM+1:2*NSPM) elseif( iav .eq. 3 ) then c=cdat2(NSPM+1:2*NSPM)+cdat2(2*NSPM+1:3*NSPM) elseif( iav .eq. 4 ) then c=cdat2(1:NSPM)+cdat2(NSPM+1:2*NSPM)+cdat2(2*NSPM+1:3*NSPM) endif ! Estimate final frequency error and carrier phase. cca=sum(c(1:1+41)*conjg(cb)) phase0=atan2(imag(cca),real(cca)) do ipha=1,3 if( ipha.eq.2 ) phase0=phase0-20*pi/180.0 if( ipha.eq.3 ) phase0=phase0+20*pi/180.0 ! 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) if( nmatchedfilter .eq. 0 ) then do i=1, 16 softbits(2*i-1)=imag(c(1+(i-1)*12)) softbits(2*i)=real(c(7+(i-1)*12)) enddo else ! matched filter softbits(1)=sum(imag(c(1:6))*pp(7:12))+sum(imag(c(NSPM-5:NSPM))*pp(1:6)) softbits(2)=sum(real(c(1:12))*pp) do i=2,16 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 endif hardbits=0 ! use sync word hard error weight to decide whether to send to decoder do i=1, 32 if( softbits(i) .ge. 0.0 ) then hardbits(i)=1 endif enddo nbadsync1=(8-sum( (2*hardbits(1:8)-1)*s8r ) )/2 nbadsync=nbadsync1 if( nbadsync .gt. 3 ) cycle ! normalize the softsymbols before submitting to decoder sav=sum(softbits)/32 s2av=sum(softbits*softbits)/32 ssig=sqrt(s2av-sav*sav) softbits=softbits/ssig if( qsocontext ) then ! search only 32 likely messages. cd=1e6 ihammd=99 do i=0,31 ncw=ig24(likelymessages(i)) cd(i)=0.0 ihammd(i)=0 do ii=1,24 ib=iand(1,ishft(ncw,1-ii)) ib=2*ib-1 if( ib*softbits(ii+8) .lt. 0 ) then cd(i)=cd(i)+abs(softbits(ii+8)) ihammd(i)=ihammd(i)+1 endif enddo enddo else ! exhaustive decoder, look at every codeword. cd=1e6 ihammd=99 do i=0,4096-1 ncw=ig24(i) cd(i)=0.0 ihammd(i)=0 do ii=1,24 ib=iand(1,ishft(ncw,1-ii)) ib=2*ib-1 if( ib*softbits(ii+8) .lt. 0 ) then cd(i)=cd(i)+abs(softbits(ii+8)) ihammd(i)=ihammd(i)+1 endif enddo enddo endif cdm=minval(cd) iloc=minloc(cd) imsg=iloc(1)-1 cd(imsg)=1e6 cdm2=minval(cd) iloc=minloc(cd) imsg2=iloc(1)-1 cdrat=cdm2/(cdm+0.001) cdrat2=cdm/(cdm2+0.0001) if( (cdm .lt. cdbest) .or. ((cdm .eq. cdbest) .and. (ihammd(imsg) .lt. nhammdbest)) ) then cdratbest = cdrat cdrat2best = cdrat2 cdbest = cdm imsgbest = imsg imsg2best = imsg2 iavbest = iav ipbest = ip ipkbest = ipk idfbest = idf idbest = id iphabest = ipha nbadsyncbest = nbadsync nhammdbest = ihammd(imsg) if( ( nhammdbest .eq. 0 ) .and. (cdbest .eq. 0.0) .and. (cdratbest .gt. 2000.0) ) goto 999 endif enddo ! phase loop enddo ! frame averaging loop enddo ! frequency dithering loop enddo ! slicer dither loop enddo ! time-sync correlation-peak loop enddo ! candidate loop 999 continue msgreceived=' ' if( imsgbest .gt. 0 ) then if( ( nhammdbest+nbadsyncbest .le. 4 ) .and. cdratbest .gt. 10.0 ) then if( qsocontext ) then nrxrpt=iand(likelymessages(imsgbest),31) nrxhash=(likelymessages(imsgbest)-nrxrpt)/32 imessage=likelymessages(imsgbest) else nrxrpt=iand(imsgbest,31) nrxhash=(imsgbest-nrxrpt)/32 imessage=imsgbest endif ! See if this message has a hash that is expected for a message sent to mycall by partnercall hashmsg=trim(mycall)//' '//trim(partnercall)//' '//rpt(nrxrpt) call fmtmsg(hashmsg,iz) call hash(hashmsg,22,ihash) ihash=iand(ihash,127) if( nrxhash.eq.ihash ) then nmessages=1 write(msgreceived,'(a1,a,1x,a,a1,1x,a4)') "<",trim(mycall),trim(partnercall),">",rpt(nrxrpt) write(lines(nmessages),1020) nutc,nsnr,t0,nint(fest),msgreceived 1020 format(i6.6,i4,f5.1,i5,' & ',a22) ! write(*,1022) nutc,ipbest,times(ipbest),snrs(ipbest),fest,nrxrpt,nrxhash, & ! rpt(nrxrpt),imessage,ig24(imessage),nhammdbest, & ! cdbest,cdratbest,cdrat2best,nbadsyncbest,ipkbest,idbest,idfbest,iavbest,iphabest !1022 format(i4.4,2x,i4,f8.3,f8.2,f8.2,i6,i6,a6,i8,i10,i4,f8.3,f8.2,f8.2,i5,i5,i5,i5,i5,i5) endif endif endif return end subroutine detectmsk32