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WSJT-X/lib/ft8/bpdecode174.f90

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Use quarter-symbol steps for time sync. Lower sync threshold. Implement subtraction and two pass decoding. Use osd2 only near nfqso. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7861 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-07-12 17:49:39 -04:00
subroutine bpdecode174(llr,apmask,maxiterations,decoded,cw,nharderror,iter)
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
!
! A log-domain belief propagation decoder for the (174,87) code.
!
integer, parameter:: N=174, K=87, M=N-K
integer*1 codeword(N),cw(N),apmask(N)
integer colorder(N)
integer*1 decoded(K)
integer Nm(7,M) ! 5, 6, or 7 bits per check
integer Mn(3,N) ! 3 checks per bit
integer synd(M)
real tov(3,N)
real toc(7,M)
real tanhtoc(7,M)
real zn(N)
real llr(N)
real Tmn
integer nrw(M)
data colorder/ &
0, 1, 2, 3, 30, 4, 5, 6, 7, 8, 9, 10, 11, 32, 12, 40, 13, 14, 15, 16,&
17, 18, 37, 45, 29, 19, 20, 21, 41, 22, 42, 31, 33, 34, 44, 35, 47, 51, 50, 43,&
36, 52, 63, 46, 25, 55, 27, 24, 23, 53, 39, 49, 59, 38, 48, 61, 60, 57, 28, 62,&
56, 58, 65, 66, 26, 70, 64, 69, 68, 67, 74, 71, 54, 76, 72, 75, 78, 77, 80, 79,&
73, 83, 84, 81, 82, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99,&
100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,&
120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,&
140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,&
160,161,162,163,164,165,166,167,168,169,170,171,172,173/
data Mn/ &
1, 25, 69, &
2, 5, 73, &
3, 32, 68, &
4, 51, 61, &
6, 63, 70, &
7, 33, 79, &
8, 50, 86, &
9, 37, 43, &
10, 41, 65, &
11, 14, 64, &
12, 75, 77, &
13, 23, 81, &
15, 16, 82, &
17, 56, 66, &
18, 53, 60, &
19, 31, 52, &
20, 67, 84, &
21, 29, 72, &
22, 24, 44, &
26, 35, 76, &
27, 36, 38, &
28, 40, 42, &
30, 54, 55, &
34, 49, 87, &
39, 57, 58, &
45, 74, 83, &
46, 62, 80, &
47, 48, 85, &
59, 71, 78, &
1, 50, 53, &
2, 47, 84, &
3, 25, 79, &
4, 6, 14, &
5, 7, 80, &
8, 34, 55, &
9, 36, 69, &
10, 43, 83, &
11, 23, 74, &
12, 17, 44, &
13, 57, 76, &
15, 27, 56, &
16, 28, 29, &
18, 19, 59, &
20, 40, 63, &
21, 35, 52, &
22, 54, 64, &
24, 62, 78, &
26, 32, 77, &
30, 72, 85, &
31, 65, 87, &
33, 39, 51, &
37, 48, 75, &
38, 70, 71, &
41, 42, 68, &
45, 67, 86, &
46, 81, 82, &
49, 66, 73, &
58, 60, 66, &
61, 65, 85, &
1, 14, 21, &
2, 13, 59, &
3, 67, 82, &
4, 32, 73, &
5, 36, 54, &
6, 43, 46, &
7, 28, 75, &
8, 33, 71, &
9, 49, 76, &
10, 58, 64, &
11, 48, 68, &
12, 19, 45, &
15, 50, 61, &
16, 22, 26, &
17, 72, 80, &
18, 40, 55, &
20, 35, 51, &
23, 25, 34, &
24, 63, 87, &
27, 39, 74, &
29, 78, 83, &
30, 70, 77, &
31, 69, 84, &
22, 37, 86, &
38, 41, 81, &
42, 44, 57, &
47, 53, 62, &
52, 56, 79, &
60, 75, 81, &
1, 39, 77, &
2, 16, 41, &
3, 31, 54, &
4, 36, 78, &
5, 45, 65, &
6, 57, 85, &
7, 14, 49, &
8, 21, 46, &
9, 15, 72, &
10, 20, 62, &
11, 17, 71, &
12, 34, 47, &
13, 68, 86, &
18, 23, 43, &
19, 64, 73, &
24, 48, 79, &
25, 70, 83, &
26, 80, 87, &
27, 32, 40, &
28, 56, 69, &
29, 63, 66, &
30, 42, 50, &
33, 37, 82, &
35, 60, 74, &
38, 55, 84, &
44, 52, 61, &
51, 53, 72, &
58, 59, 67, &
47, 56, 76, &
1, 19, 37, &
2, 61, 75, &
3, 8, 66, &
4, 60, 84, &
5, 34, 39, &
6, 26, 53, &
7, 32, 57, &
9, 52, 67, &
10, 12, 15, &
11, 51, 69, &
13, 14, 65, &
16, 31, 43, &
17, 20, 36, &
18, 80, 86, &
21, 48, 59, &
22, 40, 46, &
23, 33, 62, &
24, 30, 74, &
25, 42, 64, &
27, 49, 85, &
28, 38, 73, &
29, 44, 81, &
35, 68, 70, &
41, 63, 76, &
45, 49, 71, &
50, 58, 87, &
48, 54, 83, &
13, 55, 79, &
77, 78, 82, &
1, 2, 24, &
3, 6, 75, &
4, 56, 87, &
5, 44, 53, &
7, 50, 83, &
8, 10, 28, &
9, 55, 62, &
11, 29, 67, &
12, 33, 40, &
14, 16, 20, &
15, 35, 73, &
17, 31, 39, &
18, 36, 57, &
19, 46, 76, &
21, 42, 84, &
22, 34, 59, &
23, 26, 61, &
25, 60, 65, &
27, 64, 80, &
30, 37, 66, &
32, 45, 72, &
38, 51, 86, &
41, 77, 79, &
43, 56, 68, &
47, 74, 82, &
40, 52, 78, &
54, 61, 71, &
46, 58, 69/
data Nm/ &
1, 30, 60, 89, 118, 147, 0, &
2, 31, 61, 90, 119, 147, 0, &
3, 32, 62, 91, 120, 148, 0, &
4, 33, 63, 92, 121, 149, 0, &
2, 34, 64, 93, 122, 150, 0, &
5, 33, 65, 94, 123, 148, 0, &
6, 34, 66, 95, 124, 151, 0, &
7, 35, 67, 96, 120, 152, 0, &
8, 36, 68, 97, 125, 153, 0, &
9, 37, 69, 98, 126, 152, 0, &
10, 38, 70, 99, 127, 154, 0, &
11, 39, 71, 100, 126, 155, 0, &
12, 40, 61, 101, 128, 145, 0, &
10, 33, 60, 95, 128, 156, 0, &
13, 41, 72, 97, 126, 157, 0, &
13, 42, 73, 90, 129, 156, 0, &
14, 39, 74, 99, 130, 158, 0, &
15, 43, 75, 102, 131, 159, 0, &
16, 43, 71, 103, 118, 160, 0, &
17, 44, 76, 98, 130, 156, 0, &
18, 45, 60, 96, 132, 161, 0, &
19, 46, 73, 83, 133, 162, 0, &
12, 38, 77, 102, 134, 163, 0, &
19, 47, 78, 104, 135, 147, 0, &
1, 32, 77, 105, 136, 164, 0, &
20, 48, 73, 106, 123, 163, 0, &
21, 41, 79, 107, 137, 165, 0, &
22, 42, 66, 108, 138, 152, 0, &
18, 42, 80, 109, 139, 154, 0, &
23, 49, 81, 110, 135, 166, 0, &
16, 50, 82, 91, 129, 158, 0, &
3, 48, 63, 107, 124, 167, 0, &
6, 51, 67, 111, 134, 155, 0, &
24, 35, 77, 100, 122, 162, 0, &
20, 45, 76, 112, 140, 157, 0, &
21, 36, 64, 92, 130, 159, 0, &
8, 52, 83, 111, 118, 166, 0, &
21, 53, 84, 113, 138, 168, 0, &
25, 51, 79, 89, 122, 158, 0, &
22, 44, 75, 107, 133, 155, 172, &
9, 54, 84, 90, 141, 169, 0, &
22, 54, 85, 110, 136, 161, 0, &
8, 37, 65, 102, 129, 170, 0, &
19, 39, 85, 114, 139, 150, 0, &
26, 55, 71, 93, 142, 167, 0, &
27, 56, 65, 96, 133, 160, 174, &
28, 31, 86, 100, 117, 171, 0, &
28, 52, 70, 104, 132, 144, 0, &
24, 57, 68, 95, 137, 142, 0, &
7, 30, 72, 110, 143, 151, 0, &
4, 51, 76, 115, 127, 168, 0, &
16, 45, 87, 114, 125, 172, 0, &
15, 30, 86, 115, 123, 150, 0, &
23, 46, 64, 91, 144, 173, 0, &
23, 35, 75, 113, 145, 153, 0, &
14, 41, 87, 108, 117, 149, 170, &
25, 40, 85, 94, 124, 159, 0, &
25, 58, 69, 116, 143, 174, 0, &
29, 43, 61, 116, 132, 162, 0, &
15, 58, 88, 112, 121, 164, 0, &
4, 59, 72, 114, 119, 163, 173, &
27, 47, 86, 98, 134, 153, 0, &
5, 44, 78, 109, 141, 0, 0, &
10, 46, 69, 103, 136, 165, 0, &
9, 50, 59, 93, 128, 164, 0, &
14, 57, 58, 109, 120, 166, 0, &
17, 55, 62, 116, 125, 154, 0, &
3, 54, 70, 101, 140, 170, 0, &
1, 36, 82, 108, 127, 174, 0, &
5, 53, 81, 105, 140, 0, 0, &
29, 53, 67, 99, 142, 173, 0, &
18, 49, 74, 97, 115, 167, 0, &
2, 57, 63, 103, 138, 157, 0, &
26, 38, 79, 112, 135, 171, 0, &
11, 52, 66, 88, 119, 148, 0, &
20, 40, 68, 117, 141, 160, 0, &
11, 48, 81, 89, 146, 169, 0, &
29, 47, 80, 92, 146, 172, 0, &
6, 32, 87, 104, 145, 169, 0, &
27, 34, 74, 106, 131, 165, 0, &
12, 56, 84, 88, 139, 0, 0, &
13, 56, 62, 111, 146, 171, 0, &
26, 37, 80, 105, 144, 151, 0, &
17, 31, 82, 113, 121, 161, 0, &
28, 49, 59, 94, 137, 0, 0, &
7, 55, 83, 101, 131, 168, 0, &
24, 50, 78, 106, 143, 149, 0/
data nrw/ &
6,6,6,6,6,6,6,6,6,6, &
6,6,6,6,6,6,6,6,6,6, &
6,6,6,6,6,6,6,6,6,6, &
6,6,6,6,6,6,6,6,6,7, &
6,6,6,6,6,7,6,6,6,6, &
6,6,6,6,6,7,6,6,6,6, &
7,6,5,6,6,6,6,6,6,5, &
6,6,6,6,6,6,6,6,6,6, &
5,6,6,6,5,6,6/
ncw=3
1. add error-pattern rejection to osd174 (factor of 3 speedup for norder=3) 2. osd codeword selected based on correlation discrepancy instead of Hamming dist (improves sensitivity) 3. trap zero-valued spectrum values caused by large dt. 4. trap all-zero codeword 4. both decoders return number of hard errors 5. osd174 returns correlation discrepancy (rejection threshold still needs to be tuned). 6. both decoders return the codeword with bits in as-transmitted order, for subtraction. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7735 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-23 10:14:09 -04:00
decoded=0
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
toc=0
tov=0
tanhtoc=0
! initialize messages to checks
do j=1,M
do i=1,nrw(j)
toc(i,j)=llr((Nm(i,j)))
enddo
enddo
ncnt=0
do iter=0,maxiterations
! Update bit log likelihood ratios (tov=0 in iteration 0).
do i=1,N
if( apmask(i) .ne. 1 ) then
zn(i)=llr(i)+sum(tov(1:ncw,i))
else
zn(i)=llr(i)
endif
enddo
! Check to see if we have a codeword (check before we do any iteration).
cw=0
where( zn .gt. 0. ) cw=1
ncheck=0
do i=1,M
synd(i)=sum(cw(Nm(1:nrw(i),i)))
if( mod(synd(i),2) .ne. 0 ) ncheck=ncheck+1
Fix some bugs. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7714 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-14 11:59:36 -04:00
! if( mod(synd(i),2) .ne. 0 ) write(*,*) 'check ',i,' unsatisfied'
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
enddo
Fix some bugs. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7714 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-14 11:59:36 -04:00
! write(*,*) 'number of unsatisfied parity checks ',ncheck
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
if( ncheck .eq. 0 ) then ! we have a codeword - reorder the columns and return it
codeword=cw(colorder+1)
decoded=codeword(M+1:N)
nerr=0
do i=1,N
if( (2*cw(i)-1)*llr(i) .lt. 0.0 ) nerr=nerr+1
enddo
1. add error-pattern rejection to osd174 (factor of 3 speedup for norder=3) 2. osd codeword selected based on correlation discrepancy instead of Hamming dist (improves sensitivity) 3. trap zero-valued spectrum values caused by large dt. 4. trap all-zero codeword 4. both decoders return number of hard errors 5. osd174 returns correlation discrepancy (rejection threshold still needs to be tuned). 6. both decoders return the codeword with bits in as-transmitted order, for subtraction. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7735 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-23 10:14:09 -04:00
nharderror=nerr
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
return
endif
if( iter.gt.0 ) then ! this code block implements an early stopping criterion
! if( iter.gt.10000 ) then ! this code block implements an early stopping criterion
nd=ncheck-nclast
if( nd .lt. 0 ) then ! # of unsatisfied parity checks decreased
ncnt=0 ! reset counter
else
ncnt=ncnt+1
endif
! write(*,*) iter,ncheck,nd,ncnt
if( ncnt .ge. 5 .and. iter .ge. 10 .and. ncheck .gt. 15) then
1. add error-pattern rejection to osd174 (factor of 3 speedup for norder=3) 2. osd codeword selected based on correlation discrepancy instead of Hamming dist (improves sensitivity) 3. trap zero-valued spectrum values caused by large dt. 4. trap all-zero codeword 4. both decoders return number of hard errors 5. osd174 returns correlation discrepancy (rejection threshold still needs to be tuned). 6. both decoders return the codeword with bits in as-transmitted order, for subtraction. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7735 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-23 10:14:09 -04:00
nharderror=-1
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
return
endif
endif
nclast=ncheck
! Send messages from bits to check nodes
do j=1,M
do i=1,nrw(j)
ibj=Nm(i,j)
toc(i,j)=zn(ibj)
do kk=1,ncw ! subtract off what the bit had received from the check
if( Mn(kk,ibj) .eq. j ) then
toc(i,j)=toc(i,j)-tov(kk,ibj)
endif
enddo
enddo
enddo
! send messages from check nodes to variable nodes
do i=1,M
tanhtoc(1:7,i)=tanh(-toc(1:7,i)/2)
enddo
do j=1,N
do i=1,ncw
ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j
Tmn=product(tanhtoc(1:nrw(ichk),ichk),mask=Nm(1:nrw(ichk),ichk).ne.j)
call platanh(-Tmn,y)
! y=atanh(-Tmn)
tov(i,j)=2*y
enddo
enddo
enddo
1. add error-pattern rejection to osd174 (factor of 3 speedup for norder=3) 2. osd codeword selected based on correlation discrepancy instead of Hamming dist (improves sensitivity) 3. trap zero-valued spectrum values caused by large dt. 4. trap all-zero codeword 4. both decoders return number of hard errors 5. osd174 returns correlation discrepancy (rejection threshold still needs to be tuned). 6. both decoders return the codeword with bits in as-transmitted order, for subtraction. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7735 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-23 10:14:09 -04:00
nharderror=-1
More test files. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7713 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
2017-06-13 20:45:44 -04:00
return
end subroutine bpdecode174
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