WSJT-X/lib/fst4/get_fst4_bitmetrics.f90
2020-09-14 13:07:07 -05:00

190 lines
5.1 KiB
Fortran

subroutine get_fst4_bitmetrics(cd,nss,nmax,nhicoh,bitmetrics,s4,nsync_qual,badsync)
use timer_module, only: timer
include 'fst4_params.f90'
complex cd(0:NN*nss-1)
complex cs(0:3,NN)
complex csymb(nss)
complex, allocatable, save :: ci(:,:) ! ideal waveforms, 20 samples per symbol, 4 tones
complex c1(4,8),c2(16,4),c4(256,2)
integer isyncword1(0:7),isyncword2(0:7)
integer graymap(0:3)
integer ip(1)
integer hbits(2*NN)
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)
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(ci)) deallocate(ci)
if(first .or. nss.ne.nss0) then
allocate(ci(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/nss
do itone=0,3
dp=(itone-1.5)*dphi
phi=0.0
do j=1,nss
ci(j,itone)=cmplx(cos(phi),sin(phi))
phi=mod(phi+dp,twopi)
enddo
enddo
first=.false.
endif
do k=1,NN
i1=(k-1)*NSS
csymb=cd(i1:i1+NSS-1)
do itone=0,3
cs(itone,k)=sum(csymb*conjg(ci(:,itone)))
enddo
s4(0:3,k)=abs(cs(0:3,k))**2
enddo
! Sync quality check
is1=0
is2=0
is3=0
is4=0
is5=0
badsync=.false.
ibmax=0
do k=1,8
ip=maxloc(s4(:,k))
if(isyncword1(k-1).eq.(ip(1)-1)) is1=is1+1
ip=maxloc(s4(:,k+38))
if(isyncword2(k-1).eq.(ip(1)-1)) is2=is2+1
ip=maxloc(s4(:,k+76))
if(isyncword1(k-1).eq.(ip(1)-1)) is3=is3+1
ip=maxloc(s4(:,k+114))
if(isyncword2(k-1).eq.(ip(1)-1)) is4=is4+1
ip=maxloc(s4(:,k+152))
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
call timer('seqcorrs',0)
bitmetrics=0.0
! Process the frame in 8-symbol chunks. Use 1-symbol correlations to calculate
! 2-symbol correlations. Then use 2-symbol correlations to calculate 4-symbol
! correlations. Finally, use 4-symbol correlations to calculate 8-symbol corrs.
! This eliminates redundant calculations.
do k=1,NN,8
do m=1,8 ! do 4 1-symbol correlations for each of 8 symbs
s2=0
do n=1,4
c1(n,m)=cs(graymap(n-1),k+m-1)
s2(n-1)=abs(c1(n,m))
enddo
ipt=(k-1)*2+2*(m-1)+1
do ib=0,1
bm=maxval(s2(0:3),one(0:3,1-ib)) - &
maxval(s2(0:3),.not.one(0:3,1-ib))
if(ipt+ib.gt.2*NN) cycle
bitmetrics(ipt+ib,1)=bm
enddo
enddo
do m=1,4 ! do 16 2-symbol correlations for each of 4 2-symbol groups
s2=0
do i=1,4
do j=1,4
is=(i-1)*4+j
c2(is,m)=c1(i,2*m-1)-c1(j,2*m)
s2(is-1)=abs(c2(is,m))
enddo
enddo
ipt=(k-1)*2+4*(m-1)+1
do ib=0,3
bm=maxval(s2(0:15),one(0:15,3-ib)) - &
maxval(s2(0:15),.not.one(0:15,3-ib))
if(ipt+ib.gt.2*NN) cycle
bitmetrics(ipt+ib,2)=bm
enddo
enddo
do m=1,2 ! do 256 4-symbol corrs for each of 2 4-symbol groups
s2=0
do i=1,16
do j=1,16
is=(i-1)*16+j
c4(is,m)=c2(i,2*m-1)+c2(j,2*m)
s2(is-1)=abs(c4(is,m))
enddo
enddo
ipt=(k-1)*2+8*(m-1)+1
do ib=0,7
bm=maxval(s2(0:255),one(0:255,7-ib)) - &
maxval(s2(0:255),.not.one(0:255,7-ib))
if(ipt+ib.gt.2*NN) cycle
bitmetrics(ipt+ib,3)=bm
enddo
enddo
s2=0 ! do 65536 8-symbol correlations for the entire group
do i=1,256
do j=1,256
is=(i-1)*256+j
s2(is-1)=abs(c4(i,1)+c4(j,2))
enddo
enddo
ipt=(k-1)*2+1
do ib=0,15
bm=maxval(s2(0:65535),one(0:65535,15-ib)) - &
maxval(s2(0:65535),.not.one(0:65535,15-ib))
if(ipt+ib.gt.2*NN) cycle
bitmetrics(ipt+ib,4)=bm
enddo
enddo
call timer('seqcorrs',1)
hbits=0
where(bitmetrics(:,1).ge.0) hbits=1
ns1=count(hbits( 1: 16).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/))
ns2=count(hbits( 77: 92).eq.(/1,1,1,0,0,1,0,0,1,0,1,1,0,0,0,1/))
ns3=count(hbits(153:168).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/))
ns4=count(hbits(229:244).eq.(/1,1,1,0,0,1,0,0,1,0,1,1,0,0,0,1/))
ns5=count(hbits(305:320).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/))
nsync_qual=ns1+ns2+ns3+ns4+ns5
if(nsync_qual.lt. 46) then
badsync=.true.
return
endif
call normalizebmet(bitmetrics(:,1),2*NN)
call normalizebmet(bitmetrics(:,2),2*NN)
call normalizebmet(bitmetrics(:,3),2*NN)
call normalizebmet(bitmetrics(:,4),2*NN)
scalefac=2.83
bitmetrics=scalefac*bitmetrics
return
end subroutine get_fst4_bitmetrics