subroutine detectmsk32(cbig,n,lines,nmessages,nutc) 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) ! character*512 pchk_file,gen_file 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 ','-03 ','-02 ','-01 ','+00 ','+01 ','+02 ','+03 ','+04 ', & '+05 ','+06 ','+07 ','+08 ','+09 ','+10 ', & 'R-04','R-03','R-02','R-01','R+00','R+01','R+02','R+03','R+04', & 'R+05','R+06','R+07','R+08','R+09','R+10', & '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='K9AN K1JT '//rpt(irpt) call fmtmsg(hashmsg,iz) call hash(hashmsg,22,ihash) ihash=iand(ihash,127) ig=32*ihash + irpt likelymessages(irpt)=ig ! write(*,*) hashmsg,ig,ig24(ig) enddo qsocontext=.true. ! 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 i3800=3800/df+1 i4200=4200/df+1 ismask=.false. ismask(i3800:i4200)=.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) i1800=1800/df+1 i2200=2200/df+1 ismask=.false. ismask(i1800:i2200)=.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. 4.0) ) exit if( abs(detfer(il)) .le. 100.0 ) then ndet=ndet+1 times(ndet)=((il-1)*nstepsize+NPTS/2)*dt ferrs(ndet)=detfer(il) snrs(ndet)=12.0*log10(detmet(il))/2-9.0 endif detmet(max(1,il-5):min(nstep,il+5))=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=-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=snrs(ip) ! 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 3 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=1,6 ! 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=0,10 ! frequency jitter if( idf .eq. 0 ) then deltaf=0.0 elseif( mod(idf,2) .eq. 0 ) then deltaf=4*idf else deltaf=-4*(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=1,8 ! Hopefully we can eliminate some of these after looking at more examples if( iav .eq. 1 ) then c=cdat2(NSPM+1:2*NSPM) elseif( iav .eq. 2 ) then c=cdat2(NSPM-95:NSPM+96) c=cshift(c,-96) elseif( iav .eq. 3 ) then c=cdat2(2*NSPM-95:2*NSPM+96) c=cshift(c,-96) elseif( iav .eq. 4 ) then c=cdat2(1:NSPM) elseif( iav .eq. 5 ) then c=cdat2(2*NSPM+1:3*NSPM) elseif( iav .eq. 6 ) then c=cdat2(1:NSPM)+cdat2(NSPM+1:2*NSPM) elseif( iav .eq. 7 ) then c=cdat2(NSPM+1:2*NSPM)+cdat2(2*NSPM+1:3*NSPM) elseif( iav .eq. 8 ) 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)) ! 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 ! sample to get softsamples 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 ! sync word hard error weight is a good discriminator for ! frames that have reasonable probability of decoding hardbits=0 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 32 likely messages only, using correlation discrepancy 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 ) cd(i)=cd(i)+abs(softbits(ii+8)) if( ib*(2*hardbits(ii+8)-1) .lt. 0 ) ihammd(i)=ihammd(i)+1 enddo enddo else ! exhaustive search decoder, using correlation discrepancy 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 ) cd(i)=cd(i)+abs(softbits(ii+8)) if( ib*(2*hardbits(ii+8)-1) .lt. 0 ) ihammd(i)=ihammd(i)+1 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) if( cdrat .gt. cdratbest ) then cdratbest = cdrat cdbest = cdm imsgbest = imsg iavbest = iav ipbest = ip ipkbest = ipk idfbest = idf idbest = id nbadsyncbest = nbadsync if( ( ihammd(imsgbest)+nbadsyncbest .le. 5 ) .and. ( (cdratbest .gt. 1000.0) .or. (cdbest .eq. 0.0) ) ) goto 999 endif enddo ! frame averaging loop enddo ! frequency dithering loop enddo ! sample-time dither loop enddo ! peak loop - could be made more efficient by working harder to find good peaks msgreceived=' ' ! write(78,1001) nutc,t0,nsnr,ic,ipk,is,idf,iav,deltaf,fest,ferr,ferr2,ffin,bba,bbp,nbadsync, & ! phase0,msgreceived ! call flush(78) !1001 format(i6.6,f8.2,i5,i5,i5,i5,i5,i5,f8.2,f8.2,f8.2,f8.2,f8.2,f10.2,f8.2,i5,f8.2,2x,a22) enddo 999 continue if( imsgbest .ge. 0 ) then if(ihammd(imsgbest)+nbadsyncbest .le. 5) 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 nmessages=1 write(msgreceived,'(a1,i3,a1,1x,a4)') "<",nrxhash,">",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),ihammd(imsgbest), & ! cdbest,cdratbest,nbadsyncbest,ipkbest,idbest,idfbest,iavbest endif endif 1022 format(i4.4,2x,i4,f8.3,f8.2,f8.2,i6,i6,a6,i8,i10,i4,f8.2,f8.2,i5,i5,i5,i5,i5) return end subroutine detectmsk32