WSJT-X/lib/genmet.f90

91 lines
1.9 KiB
Fortran
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program genmet
! Generate metric table for M-FSK modulation.
character*12 arg
real*4 r(0:255)
integer hist(2,-128:128)
data hist/514*0/,idum/-1/
lim(x)=min(127,max(-128,nint(scale*x)))
nargs=iargc()
if(nargs.ne.5) then
print*,'Usage: genmet ncoh nadd m0 snr iters'
go to 999
endif
call getarg(1,arg)
read(arg,*) ncoh
call getarg(2,arg)
read(arg,*) nadd
call getarg(3,arg)
read(arg,*) m0
call getarg(4,arg)
read(arg,*) snr
call getarg(5,arg)
read(arg,*) iters
ntones=2**m0
xm0=m0
scale=5.0
fac=sqrt(1.0/nadd)
s=sqrt(10.0**(0.1*snr))
hist=0
nerr=0
call sgran()
do iter=1,iters
do i=0,ntones-1
r(i)=0.
do n=1,nadd
x1=0.707*gran()
y1=0.707*gran()
if(i.eq.0) x1=x1+s
if(ncoh.eq.0) r(i)=r(i) + x1*x1 + y1*y1
if(ncoh.ne.0) r(i)=r(i) + x1
enddo
r(i)=fac*r(i)
enddo
do m=0,m0-1
n=2**m
r1=0.
r2=0.
do i=0,ntones-1
if(iand(i,n).ne.0) r1=max(r1,r(i))
if(iand(i,n).eq.0) r2=max(r2,r(i))
enddo
don=r2-r1
doff=r1-r2
if(don.lt.0.0) nerr=nerr+1
j1=lim(doff)
hist(1,j1)=hist(1,j1)+1
j2=lim(don)
hist(2,j2)=hist(2,j2)+1
enddo
enddo
do i=-128,127
write(13,1010) i/scale,hist(1,i)/(xm0*iters),hist(2,i)/(xm0*iters)
1010 format(f8.3,2f12.9)
enddo
ber=nerr/(xm0*iters)
write(*,1020) nadd,m0,snr,ber
1020 format('nadd:',i3,' m0:',i2,' snr: 'f5.1,' BER:',f8.3)
xln2=log(2.0)
do i=-128,127
p1=hist(2,i)/(xm0*iters)
p0=hist(1,i)/(xm0*iters)
if(p0+p1.eq.0.0 .and. i.lt.0) p0=1.e-6
if(p0+p1.eq.0.0 .and. i.gt.0) p1=1.e-6
xlhd0=log(max(0.001,2.0*p0/(p0+p1)))/xln2
xlhd1=log(max(0.001,2.0*p1/(p0+p1)))/xln2
write(14,1012) i/scale,xlhd0,xlhd1,p0/(p0+p1),p1/(p0+p1)
1012 format(f7.1,2f8.3,2f9.6)
enddo
999 end program genmet