mirror of https://github.com/saitohirga/WSJT-X.git
195 lines
6.2 KiB
Fortran
195 lines
6.2 KiB
Fortran
!
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! Simulator for terminated convolutional codes (so, far, only rate 1/2)
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! BPSK on AWGN Channel
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!
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! Hybrid decoder - Fano Sequential Decoder and Ordered Statistics Decoder (OSD)a
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!
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program tccsim
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parameter (N=162,K=50)
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integer*1 gen(K,N)
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integer*1 gg(64)
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integer*1 mbits(50),mbits2(50)
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integer*4 mettab(-128:127,0:1)
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parameter (NSYM=162)
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parameter (MAXSYM=162)
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character*12 arg
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character*22 msg,msg2
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integer*1 data0(13)
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integer*1 data1(13)
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integer*1 dat(206)
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integer*1 softsym(162)
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integer*1 apmask(162),cw0(162),cw(162)
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real*4 xx0(0:255)
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real ss(162)
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character*64 g ! Interleaved polynomial coefficients
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data g/'1101010010001100101001011101100001000000100111100010010010111111'/
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data xx0/ & !Metric table
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1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
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1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
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1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
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1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
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1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
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1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, &
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0.988, 1.000, 0.991, 0.993, 1.000, 0.995, 1.000, 0.991, &
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1.000, 0.991, 0.992, 0.991, 0.990, 0.990, 0.992, 0.996, &
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0.990, 0.994, 0.993, 0.991, 0.992, 0.989, 0.991, 0.987, &
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0.985, 0.989, 0.984, 0.983, 0.979, 0.977, 0.971, 0.975, &
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0.974, 0.970, 0.970, 0.970, 0.967, 0.962, 0.960, 0.957, &
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0.956, 0.953, 0.942, 0.946, 0.937, 0.933, 0.929, 0.920, &
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0.917, 0.911, 0.903, 0.895, 0.884, 0.877, 0.869, 0.858, &
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0.846, 0.834, 0.821, 0.806, 0.790, 0.775, 0.755, 0.737, &
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0.713, 0.691, 0.667, 0.640, 0.612, 0.581, 0.548, 0.510, &
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0.472, 0.425, 0.378, 0.328, 0.274, 0.212, 0.146, 0.075, &
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0.000,-0.079,-0.163,-0.249,-0.338,-0.425,-0.514,-0.606, &
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-0.706,-0.796,-0.895,-0.987,-1.084,-1.181,-1.280,-1.376, &
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-1.473,-1.587,-1.678,-1.790,-1.882,-1.992,-2.096,-2.201, &
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-2.301,-2.411,-2.531,-2.608,-2.690,-2.829,-2.939,-3.058, &
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-3.164,-3.212,-3.377,-3.463,-3.550,-3.768,-3.677,-3.975, &
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-4.062,-4.098,-4.186,-4.261,-4.472,-4.621,-4.623,-4.608, &
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-4.822,-4.870,-4.652,-4.954,-5.108,-5.377,-5.544,-5.995, &
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-5.632,-5.826,-6.304,-6.002,-6.559,-6.369,-6.658,-7.016, &
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-6.184,-7.332,-6.534,-6.152,-6.113,-6.288,-6.426,-6.313, &
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-9.966,-6.371,-9.966,-7.055,-9.966,-6.629,-6.313,-9.966, &
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-5.858,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966, &
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-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966, &
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-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966, &
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-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966, &
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-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966, &
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-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966,-9.966/
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bias=0.42
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scale=120
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! ndelta=nint(3.4*scale)
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ndelta=100
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ib=150
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slope=2
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do i=0,255
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mettab(i-128,0)=nint(scale*(xx0(i)-bias))
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if(i.gt.ib) mettab(i-128,0)=mettab(ib-128,0)-slope*(i-ib)
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if(i.ge.1) mettab(128-i,1)=mettab(i-128,0)
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enddo
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mettab(-128,1)=mettab(-127,1)
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! Get command-line argument(s)
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nargs=iargc()
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if(nargs.ne.3) then
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print*,'Usage: tccsim "message" ntrials ndepth'
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go to 999
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endif
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call getarg(1,msg) !Get message from command line
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write(*,1000) msg
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1000 format('Message: ',a22)
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call getarg(2,arg)
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read(arg,*) ntrials
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call getarg(3,arg)
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read(arg,*) ndepth
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nbits=50+31 !User bits=99, constraint length=32
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nbytes=(nbits+7)/8
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limit=20000
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data0=0
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call wqencode(msg,ntype0,data0) !Source encoding
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write(*,*) 'data0 ',data0
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! Demonstrates how to create the generator matrix from a string that contains the interleaved
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! polynomial coefficients
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gen=0
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do j=1,64
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read(g(j:j),"(i1)") gg(j) ! read polynomial coeffs from string
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enddo
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do i=1,K
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gen(i,2*(i-1)+1:2*(i-1)+64)=gg ! fill the generator matrix with cyclic shifts of gg
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enddo
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! get message bits from data0
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nbits=0
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do i=1,7
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do ib=7,0,-1
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nbits=nbits+1
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if(nbits .le. 50) then
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mbits(nbits)=0
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if(btest(data0(i),ib)) mbits(nbits)=1
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endif
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enddo
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enddo
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write(*,*) 'Source encoded message bits: '
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write(*,'(6(8i1,1x),2i1)') mbits
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! Encode message bits using the generator matrix, generating a 162-bit codeword.
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cw0=0
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do i=1,50
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if(mbits(i).eq.1) cw0=mod(cw0+gen(i,:),2)
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enddo
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write(*,*) 'Codeword from generator matrix: '
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write(*,'(162i1)') cw0
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! call encode232(data0,nbytes,dat) !Convolutional encoding
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! write(*,*) 'Codeword from encode232: '
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! write(*,'(162i2)') dat
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! call inter_mept(dat,1) !Interleaving
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! Here, we have channel symbols.
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! call inter_mept(dat,-1) !Remove interleaving
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call init_random_seed()
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call sgran()
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do isnr=10,-20,-1
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sigma=1/sqrt(2*(10**((isnr/2.0)/10.0)))
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ngood=0
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nbad=0
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do i=1,ntrials
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do j=1,162
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ss(j)=-(2*cw0(j)-1)+sigma*gran() !Simulate soft symbols
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enddo
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rms=sqrt(sum(ss**2))
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ss=100*ss/rms
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where(ss>127.0) ss=127.0
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where(ss<-127.0) ss=-127.0
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softsym=ss
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! Call the sequential (Fano algorithm) decoder
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nbits=50+31
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! call fano232(softsym,nbits,mettab,ndelta,limit,data1,ncycles,metric,nerr)
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nerr=1
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iflag=0
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nhardmin=0
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dmin=0.0
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! If Fano fails, call OSD
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if(nerr.ne.0 .and. ndepth.ge.0) then
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apmask=0
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cw=0
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call osdwspr(softsym,apmask,ndepth,cw,nhardmin,dmin)
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! OSD produces a codeword, but code is not systematic
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! Use Fano with hard decisions to retrieve the message from the codeword
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! cw=-(2*cw-1)*64
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! nbits=50+31
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!dat=0
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!dat(1:162)=cw
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! call fano232(dat,nbits,mettab,ndelta,limit,data1,ncycles,metric,nerr)
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! iflag=1
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endif
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! call wqdecode(data1,msg2,ntype1)
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! write(*,*) msg2,iflag,nhardmin,dmin
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if(any(cw.ne.cw0)) nbad=nbad+1
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if(all(cw.eq.cw0)) ngood=ngood+1
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enddo
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write(*,'(f4.1,i8,i8)') isnr/2.0,ngood,nbad
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enddo
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999 end program tccsim
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#include '../wsprcode/wspr_old_subs.f90'
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