WSJT-X/lib/fst4/get_fst4_bitmetrics2.f90

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Fortran
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subroutine get_fst4_bitmetrics2(cd,nss,hmod,nsizes,bitmetrics,s4snr,badsync)
include 'fst4_params.f90'
complex cd(0:NN*nss-1)
complex csymb(nss)
complex, allocatable, save :: c1(:,:) ! ideal waveforms, 4 tones
complex cp(0:3) ! accumulated phase shift over symbol types 0:3
integer isyncword1(0:7),isyncword2(0:7)
integer graymap(0:3)
integer ip(1)
integer hmod
logical one(0:65535,0:15) ! 65536 8-symbol sequences, 16 bits
logical first
logical badsync
real bitmetrics(2*NN,4)
real s2(0:65535)
real s4(0:3,NN,4),s4snr(0:3,NN)
data isyncword1/0,1,3,2,1,0,2,3/
data isyncword2/2,3,1,0,3,2,0,1/
data graymap/0,1,3,2/
data first/.true./,nss0/-1/
save first,one,cp,nss0
if(nss.ne.nss0 .and. allocated(c1)) deallocate(c1)
if(first .or. nss.ne.nss0) then
allocate(c1(nss,0:3))
one=.false.
do i=0,65535
do j=0,15
if(iand(i,2**j).ne.0) one(i,j)=.true.
enddo
enddo
twopi=8.0*atan(1.0)
dphi=twopi*hmod/nss
do itone=0,3
dp=(itone-1.5)*dphi
phi=0.0
do j=1,nss
c1(j,itone)=cmplx(cos(phi),sin(phi))
phi=mod(phi+dp,twopi)
enddo
cp(itone)=cmplx(cos(phi),sin(phi))
enddo
first=.false.
endif
do k=1,NN
i1=(k-1)*NSS
csymb=cd(i1:i1+NSS-1)
do itone=0,3
s4(itone,k,1)=abs(sum(csymb*conjg(c1(:,itone))))**2
s4(itone,k,2)=abs(sum(csymb( 1:nss/2)*conjg(c1( 1:nss/2,itone))))**2 + &
abs(sum(csymb(nss/2+1: nss)*conjg(c1(nss/2+1: nss,itone))))**2
s4(itone,k,3)=abs(sum(csymb( 1: nss/4)*conjg(c1( 1: nss/4,itone))))**2 + &
abs(sum(csymb( nss/4+1: nss/2)*conjg(c1( nss/4+1: nss/2,itone))))**2 + &
abs(sum(csymb( nss/2+1:3*nss/4)*conjg(c1( nss/2+1:3*nss/4,itone))))**2 + &
abs(sum(csymb(3*nss/4+1: nss)*conjg(c1(3*nss/4+1: nss,itone))))**2
s4(itone,k,4)=abs(sum(csymb( 1: nss/8)*conjg(c1( 1: nss/8,itone))))**2 + &
abs(sum(csymb( nss/8+1: nss/4)*conjg(c1( nss/8+1: nss/4,itone))))**2 + &
abs(sum(csymb( nss/4+1:3*nss/8)*conjg(c1( nss/4+1:3*nss/8,itone))))**2 + &
abs(sum(csymb(3*nss/8+1: nss/2)*conjg(c1(3*nss/8+1: nss/2,itone))))**2 + &
abs(sum(csymb( nss/2+1:5*nss/8)*conjg(c1( nss/2+1:5*nss/8,itone))))**2 + &
abs(sum(csymb(5*nss/8+1:3*nss/4)*conjg(c1(5*nss/8+1:3*nss/4,itone))))**2 + &
abs(sum(csymb(3*nss/4+1:7*nss/8)*conjg(c1(3*nss/4+1:7*nss/8,itone))))**2 + &
abs(sum(csymb(7*nss/8+1: nss)*conjg(c1(7*nss/8+1: nss,itone))))**2
enddo
enddo
! Sync quality check
is1=0
is2=0
is3=0
is4=0
is5=0
badsync=.false.
ibmax=0
is1=0; is2=0; is3=0; is4=0; is5=0
do k=1,8
ip=maxloc(s4(:,k,1))
if(isyncword1(k-1).eq.(ip(1)-1)) is1=is1+1
ip=maxloc(s4(:,k+38,1))
if(isyncword2(k-1).eq.(ip(1)-1)) is2=is2+1
ip=maxloc(s4(:,k+76,1))
if(isyncword1(k-1).eq.(ip(1)-1)) is3=is3+1
ip=maxloc(s4(:,k+114,1))
if(isyncword2(k-1).eq.(ip(1)-1)) is4=is4+1
ip=maxloc(s4(:,k+152,1))
if(isyncword1(k-1).eq.(ip(1)-1)) is5=is5+1
enddo
nsync=is1+is2+is3+is4+is5 !Number of correct hard sync symbols, 0-40
badsync=.false.
if(nsync .lt. 16) then
badsync=.true.
return
endif
bitmetrics=0.0
do nsub=1,nsizes
do ks=1,NN
s2=0
do i=0,3
s2(i)=s4(graymap(i),ks,nsub)
enddo
ipt=1+(ks-1)*2
ibmax=1
do ib=0,ibmax
bm=maxval(s2(0:3),one(0:3,ibmax-ib)) - &
maxval(s2(0:3),.not.one(0:3,ibmax-ib))
if(ipt+ib.gt.2*NN) cycle
bitmetrics(ipt+ib,nsub)=bm
enddo
enddo
enddo
call normalizebmet(bitmetrics(:,1),2*NN)
call normalizebmet(bitmetrics(:,2),2*NN)
call normalizebmet(bitmetrics(:,3),2*NN)
call normalizebmet(bitmetrics(:,4),2*NN)
! Return the s4 array corresponding to N=1. Will be used for SNR calculation
s4snr(:,:)=s4(:,:,1)
return
end subroutine get_fst4_bitmetrics2