From f13e31820470291fdd49627287a2dc08f3fa674c Mon Sep 17 00:00:00 2001 From: Joe Taylor Date: Fri, 29 Oct 2021 15:28:42 -0400 Subject: [PATCH] Improvements to a7 decoding for FT8. --- lib/ft8_a7.f90 | 209 +++++++++++++++++++++++++++++++++++++++++++++ lib/ft8_decode.f90 | 25 ++++-- 2 files changed, 225 insertions(+), 9 deletions(-) create mode 100644 lib/ft8_a7.f90 diff --git a/lib/ft8_a7.f90 b/lib/ft8_a7.f90 new file mode 100644 index 000000000..96ffe13e6 --- /dev/null +++ b/lib/ft8_a7.f90 @@ -0,0 +1,209 @@ +module ft8_a7 + + parameter(MAXDEC=100) + +! For the following three arrays +! First index i=decode number in this sequence +! Second index j=0 or 1 for even or odd sequence +! Third index k=0 or 1 for previous or current tally for this j + real dt0(MAXDEC,0:1,0:1) !dt0(i,j,k) + real f0(MAXDEC,0:1,0:1) !f0(i,j,k) + character*37 msg0(MAXDEC,0:1,0:1) !msg0(i,j,k) + + integer jseq !even=0, odd=1 + integer ndec(0:1,0:1) !ndec(j,k) + data ndec/4*0/,jseq/0/ + +contains + +subroutine ft8_a7_save(nutc,dt,f,msg) + + use packjt77 + character*37 msg,msg1 + character*13 w(19) + character*4 g4 + integer nw(19) + logical isgrid4 + +! Statement function: + isgrid4(g4)=(len_trim(g4).eq.4 .and. & + ichar(g4(1:1)).ge.ichar('A') .and. ichar(g4(1:1)).le.ichar('R') .and. & + ichar(g4(2:2)).ge.ichar('A') .and. ichar(g4(2:2)).le.ichar('R') .and. & + ichar(g4(3:3)).ge.ichar('0') .and. ichar(g4(3:3)).le.ichar('9') .and. & + ichar(g4(4:4)).ge.ichar('0') .and. ichar(g4(4:4)).le.ichar('9')) + + j=mod(nutc/5,2) !j is 0 or 1 for odd/even sequence + jseq=j + +! Add this decode to current table for this sequence + ndec(j,1)=ndec(j,1)+1 !Number of decodes in this sequence + i=ndec(j,1) !i is pointer to new table entry + if(i.ge.MAXDEC-1) return !Prevent table overflow + if(index(msg,'<...>').ge.1) return !Don't save an unknown hashcall + + dt0(i,j,1)=dt !Save dt in table + f0(i,j,1)=f !Save f in table + f0(i+1,j,1)=-99.0 !Flag after last entry in current table + call split77(msg,nwords,nw,w) !Parse msg into words + msg0(i,j,1)=trim(w(1))//' '//trim(w(2)) + if(w(1)(1:3).eq.'CQ ' .and. nw(2).le.2) then + msg0(i,j,1)='CQ '//trim(w(2))//' '//trim(w(3)) + endif + msg1=msg0(i,j,1) !Message without grid + nn=len(trim(msg1)) !Message length without grid + if(isgrid4(w(nwords))) msg0(i,j,1)=trim(msg0(i,j,1))//' '//trim(w(nwords)) + +! If a transmission at this frequency with this message fragment +! was decoded in the previous sequence, flag it as "DO NOT USE" because +! we have already decoded that station's next transmission. + + call split77(msg1,nwords,nw,w) !Parse msg into words + do i=1,ndec(j,0) + if(f0(i,j,0).le.-98.0) cycle + i2=index(msg0(i,j,0),' '//trim(w(2))) + if(abs(f-f0(i,j,0)).lt.2.0 .and. i2.ge.3) then + f0(i,j,0)=-98.0 !Remove from list of to-be-tried a7 decodes + endif + enddo + + return +end subroutine ft8_a7_save + +subroutine ft8_dec7(cd,xdt0,f0,msg0,xdt,xsnr,msgbest,snr7,snr7b) + +! Get a7 (q3-style) decodes for FT8. + + use packjt77 + parameter(NN=79,NSPS=32) + parameter(NWAVE=NN*NSPS) !2528 + parameter(NZ=3200,NLAGS=NZ-NWAVE) + parameter(MAXMSG=206) + character*12 call_1,call_2 + character*13 w(19) + character*4 grid4 + character*37 msg0,msg,msgbest,msgsent + character c77*77 + complex cwave(0:NWAVE-1) + complex cd(0:NZ-1) + complex z + real xjunk(NWAVE) + real ccf(0:NLAGS-1) + real ccfmsg(MAXMSG) + integer itone(NN) + integer nw(19) + integer*1 msgbits(77) + logical std_1,std_2 + + if(xdt0.eq.-999.0) return !Silence compiler warning + + snr7=0. + ccfmsg=0. + call split77(msg0,nwords,nw,w) !Parse msg0 into words + call_1=w(1)(1:12) + call_2=w(2)(1:12) + grid4=w(3)(1:4) + if(call_1(1:3).eq.'CQ_') call_1(3:3)=' ' + + call stdcall(call_1,std_1) + if(call_1(1:3).eq.'CQ ') std_1=.true. + call stdcall(call_2,std_2) + + fs=200.0 !Sample rate (Hz) + bt=2.0 + ccfbest=0. + lagbest=-1 + imsgbest=1 + + do imsg=1,MAXMSG + msg=trim(call_1)//' '//trim(call_2) + i=imsg + if(call_1(1:3).eq.'CQ ' .and. i.ne.5) msg='CQ0XYZ '//trim(call_2) + if(.not.std_1) then + if(i.eq.1 .or. i.ge.6) msg='<'//trim(call_1)//'> '//trim(call_2) + if(i.ge.2 .and. i.le.4) msg=trim(call_1)//' <'//trim(call_2)//'>' + else if(.not.std_2) then + if(i.le.4 .or. i.eq.6) msg='<'//trim(call_1)//'> '//trim(call_2) + if(i.ge.7) msg=trim(call_1)//' <'//trim(call_2)//'>' + endif + j0=len(trim(msg))+2 + if(i.eq.2) msg(j0:j0+2)='RRR' + if(i.eq.3) msg(j0:j0+3)='RR73' + if(i.eq.4) msg(j0:j0+1)='73' + if(i.eq.5) then + if(std_2) then + msg='CQ '//trim(call_2) + if(call_1(3:3).eq.'_') msg=trim(call_1)//' '//trim(call_2) + if(grid4.ne.'RR73') msg=trim(msg)//' '//grid4 + endif + if(.not.std_2) msg='CQ '//trim(call_2) + endif + if(i.eq.6 .and. std_2) msg(j0:j0+3)=grid4 + if(i.ge.7) then + isnr = -50 + (i-7)/2 + if(iand(i,1).eq.1) then + write(msg(j0:j0+2),'(i3.2)') isnr + if(msg(j0:j0).eq.' ') msg(j0:j0)='+' + else + write(msg(j0:j0+3),'("R",i3.2)') isnr + if(msg(j0+1:j0+1).eq.' ') msg(j0+1:j0+1)='+' + endif + endif + +! Source-encode, then get itone() + i3=-1 + n3=-1 + call pack77(msg,i3,n3,c77) + call genft8(msg,i3,n3,msgsent,msgbits,itone) + ! Generate complex cwave + f00=0.0 + call gen_ft8wave(itone,NN,NSPS,bt,fs,f00,cwave,xjunk,1,NWAVE) + + lagmax=-1 + ccfmax=0. + nsum=32*2 + lag0=200.0*(xdt0+0.5) + lag1=max(0,lag0-20) + lag2=min(nlags-1,lag0+20) + do lag=lag1,lag2 + z=0. + s=0. + do i=0,NWAVE-1 + z=z + cd(i+lag)*conjg(cwave(i)) + if(mod(i,nsum).eq.nsum-1 .or. i.eq.NWAVE-1) then + s=s + abs(z) + z=0. + endif + enddo + ccf(lag)=s + if(ccf(lag).gt.ccfmax) then + ccfmax=ccf(lag) + lagmax=lag + endif + enddo ! lag + ccfmsg(imsg)=ccfmax + if(ccfmax.gt.ccfbest) then + ccfbest=ccfmax + lagbest=lagmax + msgbest=msg + imsgbest=imsg + endif + enddo ! imsg + + call pctile(ccfmsg,MAXMSG,50,base) + call pctile(ccfmsg,MAXMSG,84,sigma) + sigma=sigma-base + if(sigma.eq.0.0) sigma=1.0 + ccfmsg=(ccfmsg-base)/sigma + xdt=lagbest/200.0 - 0.5 + snr7=maxval(ccfmsg) + ccfmsg(imsgbest)=0. + snr7b=snr7/maxval(ccfmsg) + if(index(msgbest,'CQ0XYZ').ge.1) snr7=0. + xsnr=-99.0 + if(snr7.gt.4.0) xsnr=db(snr7)-24.0 + + return +end subroutine ft8_dec7 + + +end module ft8_a7 diff --git a/lib/ft8_decode.f90 b/lib/ft8_decode.f90 index 259ccc10c..bd08dde5c 100644 --- a/lib/ft8_decode.f90 +++ b/lib/ft8_decode.f90 @@ -237,17 +237,24 @@ contains do i=1,ndec(jseq,0) if(f0(i,jseq,0).eq.-99.0) exit if(f0(i,jseq,0).eq.-98.0) cycle + if(index(msg0(i,jseq,0),'<').ge.1) cycle !### Temporary ### call ft8_downsample(dd,newdat,f0(i,jseq,0),cd0) call ft8_dec7(cd0,dt0(i,jseq,0),f0(i,jseq,0),msg0(i,jseq,0), & - xdt,xsnr,msg37) - if(xsnr.gt.-99.0) then - if(associated(this%callback)) then - nsnr=nint(xsnr) - f1=f0(i,jseq,0) - iaptype=7 - qual=1.0 - call this%callback(sync,nsnr,xdt,f1,msg37,iaptype,qual) - endif + xdt,xsnr,msg37,snr7,snr7b) + ddt=xdt-dt0(i,jseq,0) + write(41,3041) nutc,snr7,snr7b,xdt,ddt,nint(f0(i,jseq,0)),trim(msg37) +3041 format(i6.6,3f7.2,2f6.2,i5,2x,a) + if(snr7.lt.6.0 .or. snr7b.lt.1.8) cycle + write(42,3041) nutc,snr7,snr7b,xdt,ddt,nint(f0(i,jseq,0)),trim(msg37) + flush(41) + flush(42) + if(xsnr.gt.-99.0 .and. associated(this%callback)) then + nsnr=xsnr + f1=f0(i,jseq,0) + iaptype=7 + qual=1.0 + call this%callback(sync,nsnr,xdt,f1,msg37,iaptype,qual) +! Call subtract here? endif newdat=.false. enddo