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