mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2025-04-19 09:49:37 -04:00
Add untested Fortran routuine ftrsd3.f90.
This commit is contained in:
Joe Taylor
parent
939eaa11ef
commit
d7d8a70322
188
lib/superfox/ftrsd3.f90
Normal file
188
lib/superfox/ftrsd3.f90
Normal file
@ -0,0 +1,188 @@
|
||||
subroutine ftrsd3(rxdat,rxprob,rxdat2,rxprob2,ntrials0,correct,param,ntry)
|
||||
|
||||
! Soft-decision decoder for Reed-Solomon codes.
|
||||
|
||||
! This decoding scheme is built around Phil Karn's Berlekamp-Massey
|
||||
! errors and erasures decoder. The approach is inspired by a number of
|
||||
! publications, including the stochastic Chase decoder described
|
||||
! in "Stochastic Chase Decoding of Reed-Solomon Codes", by Leroux et al.,
|
||||
! IEEE Communications Letters, Vol. 14, No. 9, September 2010 and
|
||||
! "Soft-Decision Decoding of Reed-Solomon Codes Using Successive Error-
|
||||
! and-Erasure Decoding," by Soo-Woong Lee and B. V. K. Vijaya Kumar.
|
||||
|
||||
! Steve Franke K9AN and Joe Taylor K1JT
|
||||
|
||||
use sfox_mod
|
||||
|
||||
integer, dimension(0:NN-1) :: rxdat,rxprob,rxdat2,rxprob2,workdat, &
|
||||
correct,indexes
|
||||
integer rxdat(0:NN-1) !Hard-decision symbol values
|
||||
integer rxprob(0:NN-1) !Probabilities that rxdat values are correct
|
||||
integer rxdat2(0:NN-1) !Second most probable symbol values
|
||||
integer rxprob2(0:NN-1) !Probabilities that rxdat2 values are correct
|
||||
integer workdat(0:NN-1) !Work array
|
||||
integer correct(0:NN-1) !Corrected codeword
|
||||
integer indexes(0:NN-1) !For sorting probabilities
|
||||
integer probs(0:NN-1) !Temp array for sorting probabilities
|
||||
integer thresh0(0:NN-1) !Temp array for thresholds
|
||||
integer era_pos(0:NN-KK-1) !Index values for erasures
|
||||
integer*8 nseed,ir !No unsigned int in Fortran
|
||||
integer pass,tmp
|
||||
|
||||
integer perr(0:7,0:7)
|
||||
data perr/ 4, 9,11,13,14,14,15,15, &
|
||||
2,20,20,30,40,50,50,50, &
|
||||
7,24,27,40,50,50,50,50, &
|
||||
13,25,35,46,52,70,50,50, &
|
||||
17,30,42,54,55,64,71,70, &
|
||||
25,39,48,57,64,66,77,77, &
|
||||
32,45,54,63,66,75,78,83, &
|
||||
51,58,57,66,72,77,82,86/
|
||||
|
||||
ntrials=ntrials0
|
||||
nhard=0
|
||||
nhard_min=32768
|
||||
nsoft=0
|
||||
nsoft_min=32768
|
||||
ntotal=0
|
||||
ntotal_min=32768
|
||||
nera_best=0
|
||||
nsym=nn
|
||||
|
||||
do i=0,NN-1
|
||||
indexes(i)=i
|
||||
probs(i)=rxprob(i)
|
||||
enddo
|
||||
|
||||
do pass=1,nsym-1
|
||||
do k=0,nsym-pass-1
|
||||
if(probs(k).lt.probs(k+1)) then
|
||||
probs(k)=probs(k+1)
|
||||
probs(k+1)=tmp
|
||||
tmp=indexes(k)
|
||||
indexes(k)=indexes(k+1)
|
||||
indexes(k+1)=tmp
|
||||
enddo
|
||||
enddo
|
||||
enddo
|
||||
|
||||
era_pos=0
|
||||
numera=0
|
||||
workdat=rxdat
|
||||
call rs_decode_sf(workdat,era_pos,numera,nerr) !Call the decoder
|
||||
|
||||
if(nerr.ge.0) then
|
||||
! Hard-decision decoding succeeded. Save codeword and some parameters.
|
||||
nhard=count(workdat.ne.rxdat)
|
||||
correct=workdat
|
||||
param(0)=0
|
||||
param(1)=nhard
|
||||
param(2)=0
|
||||
param(3)=0
|
||||
param(4)=0
|
||||
param(5)=0
|
||||
param(7)=1000*1000 !???
|
||||
ntry=0
|
||||
return
|
||||
endif
|
||||
|
||||
! Hard-decision decoding failed. Try the FT soft-decision method.
|
||||
! Generate random erasure-locator vectors and see if any of them
|
||||
! decode. This will generate a list of "candidate" codewords. The
|
||||
! soft distance between each candidate codeword and the received
|
||||
! word is estimated by finding the largest (pp1) and second-largest
|
||||
! (pp2) outputs from a synchronized filter-bank operating on the
|
||||
! symbol spectra, and using these to decide which candidate
|
||||
! codeword is "best".
|
||||
|
||||
nseed=1 !Seed for random numbers
|
||||
ncandidates=0
|
||||
nsum=0
|
||||
do i=0,NN-1
|
||||
nsum=nsum+rxprob(i)
|
||||
j=indexes(NN-1-i)
|
||||
ratio=(float)rxprob2(j)/((float)rxprob(j)+0.01)
|
||||
ii=7.999*ratio
|
||||
jj=(NN-1-i)/8
|
||||
thresh0(i)=1.3*perr(jj)(ii)
|
||||
enddo
|
||||
if(nsum.le.0) return
|
||||
|
||||
pp1=0.
|
||||
pp2=0.
|
||||
do k=1,ntrials
|
||||
era_pos=0
|
||||
workdat=rxdat
|
||||
|
||||
! Mark a subset of the symbols as erasures.
|
||||
! Run through the ranked symbols, starting with the worst, i=0.
|
||||
! NB: j is the symbol-vector index of the symbol with rank i.
|
||||
|
||||
numera=0
|
||||
do i=0,NN-1
|
||||
j=indexes(126-i)
|
||||
thresh=thresh0(i)
|
||||
|
||||
! Generate a random number ir, 0 <= ir <= 100 (see POSIX.1-2001 example).
|
||||
nseed=nseed*1103515245 + 12345
|
||||
ir=mod(nseed/65536),32768)
|
||||
ir=(100*ir)/32768
|
||||
nseed=iand(ir,4294967295)
|
||||
|
||||
if((ir.lt.thresh ) .and. numera.lt.(NN-KK)) then
|
||||
era_pos(numera)=j
|
||||
numera=numera+1
|
||||
endif
|
||||
enddo
|
||||
|
||||
! nerr=decode_rs_int(rs,workdat,era_pos,numera,0);
|
||||
call rs_decode_sf(workdat,era_pos,numera,nerr) !Call the decoder
|
||||
|
||||
if( nerr.ge.0) then
|
||||
! We have a candidate codeword. Find its hard and soft distance from
|
||||
! the received word. Also find pp1 and pp2 from the full array
|
||||
! s3(64,127) of synchronized symbol spectra.
|
||||
ncandidates=ncandidates+1
|
||||
nhard=0
|
||||
nsoft=0
|
||||
do i=0,NN-1
|
||||
if(workdat(i).ne. rxdat(i)) then
|
||||
nhard=nhard+1;
|
||||
if(workdat(i) .ne. rxdat2(i)) nsoft=nsoft+rxprob(i)
|
||||
endif
|
||||
enddo
|
||||
nsoft=(NN-1)*nsoft/nsum
|
||||
ntotal=nsoft+nhard
|
||||
|
||||
pp=0.
|
||||
call getpp3(s3,workdat,pp)
|
||||
if(pp.gt.pp1) then
|
||||
pp2=pp1
|
||||
pp1=pp
|
||||
nsoft_min=nsoft
|
||||
nhard_min=nhard
|
||||
ntotal_min=ntotal
|
||||
correct=workdat
|
||||
nera_best=numera
|
||||
ntry=k
|
||||
else
|
||||
if(pp.gt.pp2 .and. pp.ne.pp1) pp2=pp
|
||||
endif
|
||||
if(nhard_min <= 41 && ntotal_min <= 71) exit !### New values ###
|
||||
enddo
|
||||
if(k.eq.ntrials) ntry=k
|
||||
enddo
|
||||
|
||||
param(0)=ncandidates
|
||||
param(1)=nhard_min
|
||||
param(2)=nsoft_min
|
||||
param(3)=nera_best
|
||||
! param(4)= pp1 > 0 ? 1000.0*pp2/pp1 : 1000.0
|
||||
param(5)=ntotal_min
|
||||
param(6)=ntry
|
||||
param(7)=1000.0*pp2
|
||||
param(8)=1000.0*pp1
|
||||
if(param(0).eq.0) param(2)=-1
|
||||
|
||||
return
|
||||
end subroutine ftrsd3
|
||||
@ -13,7 +13,6 @@ contains
|
||||
1280,1296,1344,1350,1372,1400,1440,1470,1500,1512, &
|
||||
1536,1568,1600,1620,1680,1728,1920,1944,1960,2000/
|
||||
|
||||
|
||||
MM=mm0 !Bits per symbol
|
||||
NQ=2**MM !Q, number of MFSK tones
|
||||
NN=nn0 !Channel symbols, before puncture
|
||||
|
||||
Loading…
Reference in New Issue
Block a user