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132 lines
3.5 KiB
Fortran
132 lines
3.5 KiB
Fortran
subroutine get_fst4_bitmetrics(cd,nss,hmod,nmax,nhicoh,bitmetrics,s4,badsync)
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include 'fst4_params.f90'
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complex cd(0:NN*nss-1)
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complex cs(0:3,NN)
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complex csymb(nss)
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complex, allocatable, save :: c1(:,:) ! ideal waveforms, 20 samples per symbol, 4 tones
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complex cp(0:3) ! accumulated phase shift over symbol types 0:3
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complex csum,cterm
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integer isyncword1(0:7),isyncword2(0:7)
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integer graymap(0:3)
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integer ip(1)
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integer hmod
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logical one(0:65535,0:15) ! 65536 8-symbol sequences, 16 bits
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logical first
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logical badsync
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real bitmetrics(2*NN,4)
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real s2(0:65535)
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real s4(0:3,NN)
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data isyncword1/0,1,3,2,1,0,2,3/
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data isyncword2/2,3,1,0,3,2,0,1/
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data graymap/0,1,3,2/
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data first/.true./,nss0/-1/
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save first,one,cp,nss0
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if(nss.ne.nss0 .and. allocated(c1)) deallocate(c1)
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if(first .or. nss.ne.nss0) then
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allocate(c1(nss,0:3))
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one=.false.
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do i=0,65535
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do j=0,15
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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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twopi=8.0*atan(1.0)
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dphi=twopi*hmod/nss
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do itone=0,3
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dp=(itone-1.5)*dphi
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phi=0.0
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do j=1,nss
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c1(j,itone)=cmplx(cos(phi),sin(phi))
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phi=mod(phi+dp,twopi)
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enddo
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cp(itone)=cmplx(cos(phi),sin(phi))
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enddo
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first=.false.
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endif
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do k=1,NN
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i1=(k-1)*NSS
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csymb=cd(i1:i1+NSS-1)
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do itone=0,3
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cs(itone,k)=sum(csymb*conjg(c1(:,itone)))
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enddo
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s4(0:3,k)=abs(cs(0:3,k))
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enddo
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! Sync quality check
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is1=0
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is2=0
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is3=0
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is4=0
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is5=0
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badsync=.false.
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ibmax=0
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do k=1,8
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ip=maxloc(s4(:,k))
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if(isyncword1(k-1).eq.(ip(1)-1)) is1=is1+1
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ip=maxloc(s4(:,k+38))
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if(isyncword2(k-1).eq.(ip(1)-1)) is2=is2+1
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ip=maxloc(s4(:,k+76))
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if(isyncword1(k-1).eq.(ip(1)-1)) is3=is3+1
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ip=maxloc(s4(:,k+114))
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if(isyncword2(k-1).eq.(ip(1)-1)) is4=is4+1
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ip=maxloc(s4(:,k+152))
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if(isyncword1(k-1).eq.(ip(1)-1)) is5=is5+1
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enddo
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nsync=is1+is2+is3+is4+is5 !Number of correct hard sync symbols, 0-40
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badsync=.false.
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if(nsync .lt. 16) then
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badsync=.true.
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return
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endif
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bitmetrics=0.0
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do nseq=1,nmax !Try coherent sequences of 1, 2, and 4 symbols
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if(nseq.eq.1) nsym=1
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if(nseq.eq.2) nsym=2
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if(nhicoh.eq.0) then
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if(nseq.eq.3) nsym=3
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if(nseq.eq.4) nsym=4
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else
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if(nseq.eq.3) nsym=4
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if(nseq.eq.4) nsym=8
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endif
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nt=4**nsym
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do ks=1,NN-nsym+1,nsym
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s2=0
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do i=0,nt-1
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csum=0
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cterm=1
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do j=0,nsym-1
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ntone=mod(i/4**(nsym-1-j),4)
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csum=csum+cs(graymap(ntone),ks+j)*cterm
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cterm=cterm*conjg(cp(graymap(ntone)))
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enddo
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s2(i)=abs(csum)**2
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enddo
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ipt=1+(ks-1)*2
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if(nsym.eq.1) ibmax=1
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if(nsym.eq.2) ibmax=3
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if(nsym.eq.3) ibmax=5
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if(nsym.eq.4) ibmax=7
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if(nsym.eq.8) ibmax=15
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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(ipt+ib.gt.2*NN) cycle
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bitmetrics(ipt+ib,nseq)=bm
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enddo
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enddo
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enddo
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call normalizebmet(bitmetrics(:,1),2*NN)
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call normalizebmet(bitmetrics(:,2),2*NN)
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call normalizebmet(bitmetrics(:,3),2*NN)
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call normalizebmet(bitmetrics(:,4),2*NN)
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return
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end subroutine get_fst4_bitmetrics
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