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56 lines
1.7 KiB
Fortran
56 lines
1.7 KiB
Fortran
subroutine sym_prob(s3,rxdat,rxprob,rxdat2,rxprob2)
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! Demodulate the 64-bin spectra for each of 63 symbols in a frame.
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! Parameters
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! rxdat most reliable symbol value
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! rxdat2 second most likely symbol value
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! rxprob probability that rxdat was the transmitted value
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! rxprob2 probability that rxdat2 was the transmitted value
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use sfox_mod
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implicit real*8 (a-h,o-z)
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real*4 s3(0:NQ-1,0:NN-1)
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integer rxdat(0:NN-1),rxprob(0:NN-1),rxdat2(0:NN-1),rxprob2(0:NN-1)
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afac=1.1
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! scale=255.999
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scale=2047.999
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! Compute average spectral value
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ave=sum(s3)/(NQ*ND)
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i1=1 !Silence warning
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i2=1
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! Compute probabilities for most reliable symbol values
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do j=0,NN-1 !Loop over all symbols
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s1=-1.e30
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psum=0.
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do i=0,NQ-1 !Loop over frequency bins
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x=min(afac*s3(i,j)/ave,50.d0)
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psum=psum+s3(i,j)
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if(s3(i,j).gt.s1) then
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s1=s3(i,j) !Find max signal+noise power
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i1=i !Find most reliable symbol value
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endif
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enddo
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if(psum.eq.0.0) psum=1.e-6 !Guard against zero signal+noise
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s2=-1.e30
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do i=0,NQ-1
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if(i.ne.i1 .and. s3(i,j).gt.s2) then
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s2=s3(i,j) !Second largest signal+noise power
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i2=i !Bin number for second largest power
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endif
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enddo
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p1=s1/psum !p1, p2 are symbol metrics for ftrsd
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p2=s2/psum
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rxdat(j)=i1
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rxdat2(j)=i2
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rxprob(j)=scale*p1 !Scaled probabilities, 0 - 255
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rxprob2(j)=scale*p2
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enddo
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return
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end subroutine sym_prob
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