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191 lines
5.1 KiB
Fortran
191 lines
5.1 KiB
Fortran
subroutine get_fst4_bitmetrics(cd,nss,bitmetrics,s4,nsync_qual,badsync)
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use timer_module, only: timer
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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 :: ci(:,:) ! ideal waveforms, 20 samples per symbol, 4 tones
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complex c1(4,8),c2(16,4),c4(256,2)
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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 hbits(2*NN)
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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,nss0
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if(nss.ne.nss0 .and. allocated(ci)) deallocate(ci)
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if(first .or. nss.ne.nss0) then
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allocate(ci(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/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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ci(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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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(ci(:,itone)))
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enddo
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s4(0:3,k)=abs(cs(0:3,k))**2
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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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call timer('seqcorrs',0)
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bitmetrics=0.0
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! Process the frame in 8-symbol chunks. Use 1-symbol correlations to calculate
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! 2-symbol correlations. Then use 2-symbol correlations to calculate 4-symbol
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! correlations. Finally, use 4-symbol correlations to calculate 8-symbol corrs.
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! This eliminates redundant calculations.
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do k=1,NN,8
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do m=1,8 ! do 4 1-symbol correlations for each of 8 symbs
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s2=0
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do n=1,4
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c1(n,m)=cs(graymap(n-1),k+m-1)
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s2(n-1)=abs(c1(n,m))
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enddo
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ipt=(k-1)*2+2*(m-1)+1
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do ib=0,1
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bm=maxval(s2(0:3),one(0:3,1-ib)) - &
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maxval(s2(0:3),.not.one(0:3,1-ib))
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if(ipt+ib.gt.2*NN) cycle
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bitmetrics(ipt+ib,1)=bm
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enddo
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enddo
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do m=1,4 ! do 16 2-symbol correlations for each of 4 2-symbol groups
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s2=0
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do i=1,4
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do j=1,4
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is=(i-1)*4+j
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c2(is,m)=c1(i,2*m-1)-c1(j,2*m)
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s2(is-1)=abs(c2(is,m))
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enddo
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enddo
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ipt=(k-1)*2+4*(m-1)+1
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do ib=0,3
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bm=maxval(s2(0:15),one(0:15,3-ib)) - &
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maxval(s2(0:15),.not.one(0:15,3-ib))
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if(ipt+ib.gt.2*NN) cycle
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bitmetrics(ipt+ib,2)=bm
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enddo
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enddo
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do m=1,2 ! do 256 4-symbol corrs for each of 2 4-symbol groups
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s2=0
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do i=1,16
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do j=1,16
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is=(i-1)*16+j
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c4(is,m)=c2(i,2*m-1)+c2(j,2*m)
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s2(is-1)=abs(c4(is,m))
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enddo
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enddo
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ipt=(k-1)*2+8*(m-1)+1
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do ib=0,7
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bm=maxval(s2(0:255),one(0:255,7-ib)) - &
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maxval(s2(0:255),.not.one(0:255,7-ib))
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if(ipt+ib.gt.2*NN) cycle
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bitmetrics(ipt+ib,3)=bm
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enddo
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enddo
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s2=0 ! do 65536 8-symbol correlations for the entire group
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do i=1,256
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do j=1,256
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is=(i-1)*256+j
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s2(is-1)=abs(c4(i,1)+c4(j,2))
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enddo
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enddo
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ipt=(k-1)*2+1
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do ib=0,15
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bm=maxval(s2(0:65535),one(0:65535,15-ib)) - &
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maxval(s2(0:65535),.not.one(0:65535,15-ib))
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if(ipt+ib.gt.2*NN) cycle
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bitmetrics(ipt+ib,4)=bm
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enddo
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enddo
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call timer('seqcorrs',1)
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hbits=0
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where(bitmetrics(:,1).ge.0) hbits=1
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ns1=count(hbits( 1: 16).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/))
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ns2=count(hbits( 77: 92).eq.(/1,1,1,0,0,1,0,0,1,0,1,1,0,0,0,1/))
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ns3=count(hbits(153:168).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/))
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ns4=count(hbits(229:244).eq.(/1,1,1,0,0,1,0,0,1,0,1,1,0,0,0,1/))
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ns5=count(hbits(305:320).eq.(/0,0,0,1,1,0,1,1,0,1,0,0,1,1,1,0/))
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nsync_qual=ns1+ns2+ns3+ns4+ns5
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if(nsync_qual.lt. 46) then
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badsync=.true.
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return
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endif
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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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scalefac=2.83
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bitmetrics=scalefac*bitmetrics
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return
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end subroutine get_fst4_bitmetrics
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