program ldpcsim174_91 ! End to end test of the (174,91)/crc14 encoder and decoder. use packjt77 integer, parameter:: N=174, K=91, M=N-K, NN=58 character*37 msg,msgsent character*77 c77 character*8 arg integer*1, allocatable :: codeword(:), decoded(:), message(:) integer*1 msgbits(77) integer*1 message91(91) integer*1 apmask(N), cw(N) integer lmax(1) integer modtype, itone(79), itonecw(58), graymap(0:7) integer nerrtot(0:N),nerrdec(0:N) integer channeltype logical unpk77_success logical one(0:511,0:8) real*8, allocatable :: rxdata(:) real llr(174),llra(174),llrb(174),llrc(174),llrd(174) real bmeta(174),bmetb(174),bmetc(174),bmetd(174) complex cs(0:7,NN) real s2(0:511) data graymap/0,1,3,2,5,6,4,7/ nerrtot=0 nerrdec=0 ! nargs=iargc() if(nargs.ne.7) then print*,'Usage: ldpcsim maxosd norder #trials s Keff modtype channel' print*,'eg: ldpcsim 10 2 1000 0.84 91 1 0' print*,' maxosd<0: do bp only' print*,' maxosd=0: do bp and then call osd once with channel llrs' print*,' maxosd>1: do bp and then call osd maxosd times with saved bp outputs' print*,' norder : osd decoding depth' print*,' s : BPSK only, noise sigma, if s<0 value is ignored and sigma is calculated from SNR.' print*,' Keff : Keff must be in the range [77,91]; Keff-77 is the # of bits to use as CRC.' print*,' modtype : 0, coherent BPSK; 1 noncoherent 8FSK' print*,' channel : 0, AWGN; 1, block Rayleigh (Rayleigh only works with 8FSK!)' return endif call getarg(1,arg) read(arg,*) maxosd call getarg(2,arg) read(arg,*) norder call getarg(3,arg) read(arg,*) ntrials call getarg(4,arg) read(arg,*) s call getarg(5,arg) read(arg,*) Keff call getarg(6,arg) read(arg,*) modtype call getarg(7,arg) read(arg,*) channeltype ! scale Eb/No for a (174,91) code rate=real(K)/real(N) write(*,*) "rate: ",rate allocate ( codeword(N), decoded(K), message(K) ) allocate ( rxdata(N) ) one=.false. do i=0,511 do j=0,8 if(iand(i,2**j).ne.0) one(i,j)=.true. enddo enddo msg="K9ABC K1ABC FN20" i3=0 n3=1 call pack77(msg,i3,n3,c77) !Pack into 12 6-bit bytes call unpack77(c77,1,msgsent,unpk77_success) !Unpack to get msgsent write(*,*) "message sent ",msgsent read(c77,'(77i1)') msgbits(1:77) write(*,*) 'message' write(*,'(a71,1x,a3,1x,a3)') c77(1:71),c77(72:74),c77(75:77) call init_random_seed() iq=1 if(modtype.gt.0) then ! MFSK - get tones i3=-1 n3=-1 call genft8(msg,i3,n3,msgsent,msgbits,itone) write(*,*) 'message tones' write(*,'(79(i1,1x))') itone itonecw(1:29)=itone(8:36) itonecw(30:58)=itone(44:72) iq=3 ! bits per symbol endif call encode174_91(msgbits,codeword) write(*,*) 'crc14' write(*,'(14i1)') codeword(78:91) write(*,*) 'codeword' write(*,'(22(8i1,1x))') codeword write(*,*) 'Eb/N0 Es/N0 SNR2500 ngood nundetected sigma psymerr pbiterr' do idb = 20,-4,-1 nsymerr=0 nbiterr=0 db=idb/2.0-1.0 sigma=1/sqrt( 2*rate*iq*(10**(db/10.0)) ) ngood=0 nue=0 nsumerr=0 do itrial=1, ntrials ! Create a realization of a noisy received word if(modtype.eq.0) then do i=1,N rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran() enddo nerr=0 do i=1,N if( rxdata(i)*(2*codeword(i)-1.0) .lt. 0 ) nerr=nerr+1 enddo if(nerr.ge.1) nerrtot(nerr)=nerrtot(nerr)+1 rxav=sum(rxdata)/N rx2av=sum(rxdata*rxdata)/N rxsig=sqrt(rx2av-rxav*rxav) rxdata=rxdata/rxsig if( s .lt. 0 ) then ss=sigma else ss=s endif llr=2.0*rxdata/(ss*ss) else ! noncoherent MFSK do i=1,58 do j=0,7 if(j.eq.itonecw(i)) then if(channeltype.eq.0) then A=1.0 elseif(channeltype.eq.1) then xI=gran()**2 + gran()**2 A=sqrt(xI/2) endif cs(j,i)= A + sigma*gran() + cmplx(0,1)*sigma*gran() elseif(j.ne.itonecw(i)) then cs(j,i)= sigma*gran() + cmplx(0,1)*sigma*gran() endif enddo lmax=maxloc(abs(cs(:,i))) if(lmax(1)-1.ne.itonecw(i) ) nsymerr=nsymerr+1 enddo do nsym=1,3 nt=2**(3*nsym) do ks=1,58,nsym amax=-1.0 do i=0,nt-1 i1=i/64 i2=iand(i,63)/8 i3=iand(i,7) if(nsym.eq.1) then s2(i)=abs(cs(graymap(i3),ks)) elseif(nsym.eq.2) then s2(i)=abs(cs(graymap(i2),ks)+cs(graymap(i3),ks+1)) elseif(nsym.eq.3) then if(ks.ne.58) then s2(i)=abs(cs(graymap(i1),ks)+cs(graymap(i2),ks+1)+cs(graymap(i3),ks+2)) else s2(i)=abs(cs(graymap(i1),ks)) endif else print*,"Error - nsym must be 1, 2, or 3." endif enddo i32=1+(ks-1)*3 if(nsym.eq.1) ibmax=2 if(nsym.eq.2) ibmax=5 if(nsym.eq.3) ibmax=8 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(i32+ib .gt.174) cycle if(nsym.eq.1) then bmeta(i32+ib)=bm den=max(maxval(s2(0:nt-1),one(0:nt-1,ibmax-ib)), & maxval(s2(0:nt-1),.not.one(0:nt-1,ibmax-ib))) if(den.gt.0.0) then cm=bm/den else ! erase it cm=0.0 endif bmetd(i32+ib)=cm elseif(nsym.eq.2) then bmetb(i32+ib)=bm elseif(nsym.eq.3) then bmetc(i32+ib)=bm endif enddo enddo enddo call normalizebmet(bmeta,174) call normalizebmet(bmetb,174) call normalizebmet(bmetc,174) call normalizebmet(bmetd,174) scalefac=2.83 llra=scalefac*bmeta llrb=scalefac*bmetb llrc=scalefac*bmetc llrd=scalefac*bmetd llr=llrc endif do i=1, 174 if(llr(i)*(codeword(i)-0.5).lt.0) nbiterr=nbiterr+1 enddo nap=0 ! number of AP bits llr(1:nap)=5*(2.0*msgbits(1:nap)-1.0) apmask=0 apmask(1:nap)=1 call decode174_91(llr,Keff,maxosd,norder,apmask,message91,cw,ntype,nharderrors,dmin) ! If the decoder finds a valid codeword, nharderrors will be .ge. 0. if( nharderrors.ge.0 ) then nhw=count(cw.ne.codeword) if(nhw.eq.0) then ! this is a good decode ngood=ngood+1 nerrdec(nerr)=nerrdec(nerr)+1 else nue=nue+1 endif endif nsumerr=nsumerr+nerr enddo esn0=db+10.0*log10(iq*rate) ! iq=3 bits per symbol for 8FSK snr2500=esn0-10.0*log10(2500/6.25) ! pberr=real(nsumerr)/(real(ntrials*N)) psymerr=real(nsymerr)/(ntrials*174.0/iq) pbiterr=real(nbiterr)/(ntrials*174.0) write(*,"(f4.1,4x,f5.1,4x,f5.1,1x,i8,1x,i8,8x,f5.2,8x,e10.3,8x,e10.3)") db,esn0,snr2500,ngood,nue,ss,psymerr,pbiterr enddo open(unit=23,file='nerrhisto.dat',status='unknown') do i=1,174 write(23,'(i4,2x,i10,i10,f10.2)') i,nerrdec(i),nerrtot(i),real(nerrdec(i))/real(nerrtot(i)+1e-10) enddo close(23) end program ldpcsim174_91 subroutine normalizebmet(bmet,n) real bmet(n) bmetav=sum(bmet)/real(n) bmet2av=sum(bmet*bmet)/real(n) var=bmet2av-bmetav*bmetav if( var .gt. 0.0 ) then bmetsig=sqrt(var) else bmetsig=sqrt(bmet2av) endif bmet=bmet/bmetsig return end subroutine normalizebmet