mirror of https://github.com/saitohirga/WSJT-X.git
Add routines to decode msk40 and msk144 messages using log-domain belief propagation. Also add new routines to test msk144/msk40 encoding and decoding.
git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7035 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Steven Franke
parent
5e8f9074a6
commit
7ba75b79c9
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@ -0,0 +1,290 @@
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subroutine bpdecode144(llr,maxiterations,decoded,niterations)
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!
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! A log-domain belief propagation decoder for the msk144 code.
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! The code is a regular (128,80) code with column weight 3 and row weight 8.
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! k9an August, 2016
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!
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integer, parameter:: N=128, K=80, M=N-K
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integer*1 codeword(N),cw(N)
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integer*1 colorder(N)
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integer*1 decoded(K)
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integer Nm(8,M) ! 8 bits per check
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integer Mn(3,N) ! 3 checks per bit
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integer synd(M)
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real*8 tov(3,N)
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real*8 toc(8,M)
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real*8 tanhtoc(8,M)
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real*8 zn(N)
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real*8 llr(N)
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real*8 Tmn
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real*8 xth
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data colorder/0,1,2,3,4,5,6,7,8,9, &
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10,11,12,13,14,15,24,26,29,30, &
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32,43,44,47,60,77,79,97,101,111, &
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96,38,64,53,93,34,59,94,74,90, &
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108,123,85,57,70,25,69,62,48,49, &
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50,51,52,33,54,55,56,21,58,36, &
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16,61,23,63,20,65,66,67,68,46, &
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22,71,72,73,31,75,76,45,78,17, &
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80,81,82,83,84,42,86,87,88,89, &
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39,91,92,35,37,95,19,27,98,99, &
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100,28,102,103,104,105,106,107,40,109, &
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110,18,112,113,114,115,116,117,118,119, &
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120,121,122,41,124,125,126,127/
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data Mn/ &
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1, 14, 38, &
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2, 4, 41, &
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3, 19, 39, &
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5, 29, 34, &
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6, 35, 40, &
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7, 20, 45, &
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8, 28, 48, &
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9, 22, 25, &
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10, 24, 36, &
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11, 12, 37, &
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13, 43, 44, &
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15, 18, 46, &
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16, 17, 47, &
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21, 32, 33, &
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23, 30, 31, &
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26, 27, 42, &
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1, 12, 46, &
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2, 36, 38, &
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3, 5, 10, &
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4, 9, 23, &
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6, 13, 39, &
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7, 15, 17, &
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8, 18, 27, &
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11, 33, 40, &
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14, 28, 44, &
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16, 29, 31, &
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19, 20, 22, &
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21, 30, 42, &
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24, 26, 47, &
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25, 37, 48, &
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32, 34, 45, &
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8, 35, 41, &
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12, 31, 43, &
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1, 19, 21, &
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2, 43, 45, &
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3, 4, 11, &
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5, 18, 33, &
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6, 25, 47, &
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7, 28, 30, &
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9, 14, 34, &
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10, 35, 42, &
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13, 15, 22, &
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16, 37, 38, &
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17, 41, 44, &
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20, 24, 29, &
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18, 23, 39, &
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12, 26, 32, &
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27, 38, 40, &
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15, 36, 48, &
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2, 30, 46, &
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1, 4, 13, &
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3, 28, 32, &
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5, 43, 47, &
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6, 34, 46, &
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7, 9, 40, &
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8, 11, 45, &
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10, 17, 23, &
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14, 31, 35, &
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16, 22, 42, &
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19, 37, 44, &
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20, 33, 48, &
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21, 24, 41, &
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25, 27, 29, &
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26, 39, 48, &
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19, 31, 36, &
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1, 5, 7, &
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2, 29, 39, &
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3, 16, 46, &
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4, 26, 37, &
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6, 28, 45, &
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8, 22, 33, &
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9, 21, 43, &
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10, 25, 38, &
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11, 14, 24, &
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12, 17, 40, &
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13, 27, 30, &
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15, 32, 35, &
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18, 44, 47, &
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20, 23, 36, &
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34, 41, 42, &
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1, 32, 48, &
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2, 3, 33, &
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4, 29, 42, &
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5, 14, 37, &
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6, 7, 36, &
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8, 9, 39, &
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10, 13, 19, &
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11, 18, 30, &
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12, 16, 20, &
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15, 29, 44, &
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17, 34, 38, &
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6, 21, 22, &
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23, 32, 40, &
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24, 27, 46, &
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25, 41, 45, &
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7, 26, 43, &
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28, 31, 47, &
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20, 35, 38, &
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1, 33, 41, &
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2, 42, 44, &
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3, 23, 48, &
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4, 31, 45, &
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5, 8, 30, &
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9, 16, 36, &
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10, 40, 47, &
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11, 17, 46, &
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12, 21, 34, &
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13, 24, 28, &
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14, 18, 43, &
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15, 25, 26, &
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19, 27, 35, &
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22, 37, 39, &
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1, 16, 18, &
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2, 6, 20, &
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3, 30, 43, &
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4, 28, 33, &
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5, 22, 23, &
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7, 39, 42, &
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8, 12, 38, &
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9, 35, 46, &
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10, 27, 32, &
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11, 15, 34, &
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13, 36, 37, &
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14, 41, 47, &
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17, 21, 25, &
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19, 29, 45, &
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24, 31, 48, &
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26, 40, 44/
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data Nm/ &
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1, 17, 34, 51, 66, 81, 99, 113, &
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2, 18, 35, 50, 67, 82, 100, 114, &
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3, 19, 36, 52, 68, 82, 101, 115, &
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2, 20, 36, 51, 69, 83, 102, 116, &
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4, 19, 37, 53, 66, 84, 103, 117, &
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5, 21, 38, 54, 70, 85, 92, 114, &
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6, 22, 39, 55, 66, 85, 96, 118, &
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7, 23, 32, 56, 71, 86, 103, 119, &
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8, 20, 40, 55, 72, 86, 104, 120, &
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9, 19, 41, 57, 73, 87, 105, 121, &
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10, 24, 36, 56, 74, 88, 106, 122, &
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10, 17, 33, 47, 75, 89, 107, 119, &
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11, 21, 42, 51, 76, 87, 108, 123, &
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1, 25, 40, 58, 74, 84, 109, 124, &
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12, 22, 42, 49, 77, 90, 110, 122, &
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13, 26, 43, 59, 68, 89, 104, 113, &
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13, 22, 44, 57, 75, 91, 106, 125, &
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12, 23, 37, 46, 78, 88, 109, 113, &
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3, 27, 34, 60, 65, 87, 111, 126, &
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6, 27, 45, 61, 79, 89, 98, 114, &
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14, 28, 34, 62, 72, 92, 107, 125, &
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8, 27, 42, 59, 71, 92, 112, 117, &
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15, 20, 46, 57, 79, 93, 101, 117, &
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9, 29, 45, 62, 74, 94, 108, 127, &
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8, 30, 38, 63, 73, 95, 110, 125, &
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16, 29, 47, 64, 69, 96, 110, 128, &
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16, 23, 48, 63, 76, 94, 111, 121, &
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7, 25, 39, 52, 70, 97, 108, 116, &
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4, 26, 45, 63, 67, 83, 90, 126, &
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15, 28, 39, 50, 76, 88, 103, 115, &
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15, 26, 33, 58, 65, 97, 102, 127, &
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14, 31, 47, 52, 77, 81, 93, 121, &
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14, 24, 37, 61, 71, 82, 99, 116, &
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4, 31, 40, 54, 80, 91, 107, 122, &
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5, 32, 41, 58, 77, 98, 111, 120, &
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9, 18, 49, 65, 79, 85, 104, 123, &
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10, 30, 43, 60, 69, 84, 112, 123, &
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1, 18, 43, 48, 73, 91, 98, 119, &
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3, 21, 46, 64, 67, 86, 112, 118, &
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5, 24, 48, 55, 75, 93, 105, 128, &
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2, 32, 44, 62, 80, 95, 99, 124, &
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16, 28, 41, 59, 80, 83, 100, 118, &
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11, 33, 35, 53, 72, 96, 109, 115, &
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11, 25, 44, 60, 78, 90, 100, 128, &
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6, 31, 35, 56, 70, 95, 102, 126, &
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12, 17, 50, 54, 68, 94, 106, 120, &
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13, 29, 38, 53, 78, 97, 105, 124, &
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7, 30, 49, 61, 64, 81, 101, 127/
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nrw=8
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ncw=3
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toc=0
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tov=0
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tanhtoc=0
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! initial messages to checks
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do j=1,M
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do i=1,nrw
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toc(i,j)=llr((Nm(i,j)))
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enddo
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enddo
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do iter=0,maxiterations
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! Update bit log likelihood ratios
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do i=1,N
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zn(i)=llr(i)+sum(tov(1:ncw,i))
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enddo
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! Check to see if we have a codeword
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cw=0
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where( zn .gt. 0. ) cw=1
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ncheck=0
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do i=1,M
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synd(i)=sum(cw(Nm(1:nrw,i)))
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synd(i)=mod(synd(i),2)
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if( synd(i) .ne. 0 ) ncheck=ncheck+1
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enddo
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if( ncheck .eq. 0 ) then ! we have a codeword - reorder the columns and return it.
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niterations=iter
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codeword=cw(colorder+1)
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decoded=codeword(M+1:N)
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return
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endif
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! Send messages from bits to check nodes
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do j=1,M
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do i=1,nrw
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toc(i,j)=zn(Nm(i,j))
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do kk=1,ncw ! subtract off what the bit had received from the check
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if( Mn(kk,Nm(i,j)) .eq. j ) then ! Mn(3,128)
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toc(i,j)=toc(i,j)-tov(kk,Nm(i,j))
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endif
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enddo
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enddo
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enddo
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! send messages from check nodes to variable nodes
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do i=1,M
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tanhtoc(1:nrw,i)=tanh(-toc(1:nrw,i)/2)
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enddo
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do j=1,N
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do i=1,ncw
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ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j
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Tmn=1.0
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do kk=1,nrw
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if( Nm(kk,ichk) .ne. j ) then
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Tmn=Tmn*tanhtoc(kk,ichk)
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endif
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enddo
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tov(i,j)=2*atanh(-Tmn)
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enddo
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enddo
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xth=35.0
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where(tov .gt. xth) tov=xth
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where(tov .lt. -xth) tov=-xth
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enddo
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niterations=-1
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end subroutine bpdecode144
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@ -0,0 +1,157 @@
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subroutine bpdecode40(llr,maxiterations,decoded,niterations)
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!
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! A log-domain belief propagation decoder for the msk40 code.
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! The code is a regular (32,16) code with column weight 3 and row weights 5,6,7.
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! k9an August, 2016
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!
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integer, parameter:: N=32, K=16, M=N-K
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integer*1 codeword(N),cw(N)
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integer*1 colorder(N)
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integer*1 decoded(K)
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integer Nm(7,M)
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integer Mn(3,N) ! 3 checks per bit
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integer synd(M)
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real*8 tov(3,N)
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real*8 toc(7,M)
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real*8 tanhtoc(7,M)
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real*8 zn(N)
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real*8 llr(N)
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real*8 Tmn
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real*8 xth
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integer nrw(M)
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data colorder/ &
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4, 1, 2, 3, 0, 8, 6, 10, &
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13, 28, 20, 23, 17, 15, 27, 25, &
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16, 12, 18, 19, 7, 21, 22, 11, &
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24, 5, 26, 14, 9, 29, 30, 31/
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data Mn/ &
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1, 6, 13, &
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2, 3, 14, &
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4, 8, 15, &
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5, 11, 12, &
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7, 10, 16, &
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6, 9, 15, &
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1, 11, 16, &
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2, 4, 5, &
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3, 7, 9, &
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8, 10, 12, &
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8, 13, 14, &
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1, 4, 12, &
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2, 6, 10, &
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3, 11, 15, &
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5, 9, 14, &
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7, 13, 15, &
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12, 14, 16, &
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1, 2, 8, &
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3, 5, 6, &
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4, 9, 11, &
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1, 7, 14, &
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5, 10, 13, &
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3, 4, 16, &
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2, 15, 16, &
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6, 7, 12, &
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7, 8, 11, &
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1, 9, 10, &
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2, 11, 13, &
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3, 12, 13, &
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4, 6, 14, &
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1, 5, 15, &
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8, 9, 16/
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data Nm/ &
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1, 7, 12, 18, 21, 27, 31, &
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2, 8, 13, 18, 24, 28, 0, &
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2, 9, 14, 19, 23, 29, 0, &
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3, 8, 12, 20, 23, 30, 0, &
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4, 8, 15, 19, 22, 31, 0, &
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1, 6, 13, 19, 25, 30, 0, &
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5, 9, 16, 21, 25, 26, 0, &
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3, 10, 11, 18, 26, 32, 0, &
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6, 9, 15, 20, 27, 32, 0,&
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5, 10, 13, 22, 27, 0, 0, &
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4, 7, 14, 20, 26, 28, 0, &
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4, 10, 12, 17, 25, 29, 0, &
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1, 11, 16, 22, 28, 29, 0, &
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2, 11, 15, 17, 21, 30, 0, &
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3, 6, 14, 16, 24, 31, 0, &
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5, 7, 17, 23, 24, 32, 0/
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data nrw/7,6,6,6,6,6,6,6,6,5,6,6,6,6,6,6/
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ncw=3
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toc=0
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tov=0
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tanhtoc=0
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! initialize messages to checks
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do j=1,M
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do i=1,nrw(j)
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toc(i,j)=llr((Nm(i,j)))
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enddo
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enddo
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do iter=0,maxiterations
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! Update bit log likelihood ratios (tov=0 in iteration 0).
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do i=1,N
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zn(i)=llr(i)+sum(tov(1:ncw,i))
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enddo
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! Check to see if we have a codeword (check before we do any iteration).
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cw=0
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where( zn .gt. 0. ) cw=1
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ncheck=0
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do i=1,M
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synd(i)=sum(cw(Nm(1:nrw(i),i)))
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synd(i)=mod(synd(i),2)
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if( synd(i) .ne. 0 ) ncheck=ncheck+1
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enddo
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if( ncheck .eq. 0 ) then ! we have a codeword - reorder the columns and return it
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niterations=iter
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codeword=cw(colorder+1)
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decoded=codeword(M+1:N)
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return
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endif
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! Send messages from bits to check nodes
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do j=1,M
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do i=1,nrw(j)
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toc(i,j)=zn(Nm(i,j))
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do kk=1,ncw ! subtract off what the bit had received from the check
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if( Mn(kk,Nm(i,j)) .eq. j ) then
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toc(i,j)=toc(i,j)-tov(kk,Nm(i,j))
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endif
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enddo
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enddo
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enddo
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! send messages from check nodes to variable nodes
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do i=1,M
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tanhtoc(1:nrw(i),i)=tanh(-toc(1:nrw(i),i)/2.)
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enddo
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do j=1,N
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do i=1,ncw
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ichk=Mn(i,j) ! Mn(:,j) are the checks that include bit j
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Tmn=1.0
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do kk=1,nrw(ichk)
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if( Nm(kk,ichk) .ne. j ) then
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Tmn=Tmn*tanhtoc(kk,ichk)
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endif
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enddo
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tov(i,j)=2.*atanh(-Tmn)
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enddo
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enddo
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xth=35.0
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||||
where(tov .gt. xth) tov=xth
|
||||
where(tov .lt. -xth) tov=-xth
|
||||
|
||||
enddo
|
||||
niterations=-1
|
||||
return
|
||||
end subroutine bpdecode40
|
||||
|
|
@ -0,0 +1,162 @@
|
|||
program ldpcsim
|
||||
|
||||
use, intrinsic :: iso_c_binding
|
||||
use iso_c_binding, only: c_loc,c_size_t
|
||||
use hashing
|
||||
use packjt
|
||||
character*22 msg,msgsent,msgreceived
|
||||
character*80 prefix
|
||||
character*85 pchk_file,gen_file
|
||||
character*8 arg
|
||||
integer*1, allocatable :: codeword(:), decoded(:), message(:)
|
||||
integer*1, target:: i1Msg8BitBytes(10)
|
||||
integer*1 i1hash(4)
|
||||
integer*1 msgbits(80)
|
||||
integer*1 bitseq(144)
|
||||
integer*4 i4Msg6BitWords(13)
|
||||
integer ihash
|
||||
real*8, allocatable :: lratio(:), rxdata(:), llr(:)
|
||||
real, allocatable :: yy(:)
|
||||
equivalence(ihash,i1hash)
|
||||
|
||||
nargs=iargc()
|
||||
if(nargs.ne.7) then
|
||||
print*,'Usage: ldpcsim <pchk file prefix > N K niter ndither #trials s '
|
||||
print*,'eg: ldpcsim "/pathto/peg-32-16-reg3" 32 16 10 1 1000 0.75'
|
||||
return
|
||||
endif
|
||||
call getarg(1,prefix)
|
||||
call getarg(2,arg)
|
||||
read(arg,*) N
|
||||
call getarg(3,arg)
|
||||
read(arg,*) K
|
||||
call getarg(4,arg)
|
||||
read(arg,*) max_iterations
|
||||
call getarg(5,arg)
|
||||
read(arg,*) max_dither
|
||||
call getarg(6,arg)
|
||||
read(arg,*) ntrials
|
||||
call getarg(7,arg)
|
||||
read(arg,*) s
|
||||
|
||||
pchk_file=trim(prefix)//".pchk"
|
||||
gen_file=trim(prefix)//".gen"
|
||||
|
||||
!rate=real(K)/real(N)
|
||||
! don't count hash bits as data bits
|
||||
rate=72.0/real(N)
|
||||
|
||||
write(*,*) "rate: ",rate
|
||||
|
||||
write(*,*) "pchk file: ",pchk_file
|
||||
write(*,*) "niter= ",max_iterations," ndither= ",max_dither," s= ",s
|
||||
|
||||
allocate ( codeword(N), decoded(K), message(K) )
|
||||
allocate ( lratio(N), rxdata(N), yy(N), llr(N) )
|
||||
|
||||
call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
|
||||
msg="K9AN K1JT EN50"
|
||||
call packmsg(msg,i4Msg6BitWords,itype) !Pack into 12 6-bit bytes
|
||||
call unpackmsg(i4Msg6BitWords,msgsent) !Unpack to get msgsent
|
||||
write(*,*) "message sent ",msgsent
|
||||
|
||||
i4=0
|
||||
ik=0
|
||||
im=0
|
||||
do i=1,12
|
||||
nn=i4Msg6BitWords(i)
|
||||
do j=1, 6
|
||||
ik=ik+1
|
||||
i4=i4+i4+iand(1,ishft(nn,j-6))
|
||||
i4=iand(i4,255)
|
||||
if(ik.eq.8) then
|
||||
im=im+1
|
||||
! if(i4.gt.127) i4=i4-256
|
||||
i1Msg8BitBytes(im)=i4
|
||||
ik=0
|
||||
endif
|
||||
enddo
|
||||
enddo
|
||||
|
||||
ihash=nhash(c_loc(i1Msg8BitBytes),int(9,c_size_t),146)
|
||||
ihash=2*iand(ihash,32767) !Generate the 8-bit hash
|
||||
i1Msg8BitBytes(10)=i1hash(1) !CRC to byte 10
|
||||
mbit=0
|
||||
do i=1, 10
|
||||
i1=i1Msg8BitBytes(i)
|
||||
do ibit=1,8
|
||||
mbit=mbit+1
|
||||
msgbits(mbit)=iand(1,ishft(i1,ibit-8))
|
||||
enddo
|
||||
enddo
|
||||
|
||||
call encode_msk144(msgbits,codeword)
|
||||
call init_random_seed()
|
||||
|
||||
write(*,*) "Eb/N0 ngood nundetected nbadhash"
|
||||
do idb = -6, 14
|
||||
db=idb/2.0-1.0
|
||||
sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
|
||||
ngood=0
|
||||
nue=0
|
||||
nbadhash=0
|
||||
|
||||
do itrial=1, ntrials
|
||||
call sgran()
|
||||
! Create a realization of a noisy received word
|
||||
do i=1,N
|
||||
rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
|
||||
enddo
|
||||
|
||||
! Correct signal normalization is important for this decoder.
|
||||
rxav=sum(rxdata)/N
|
||||
rx2av=sum(rxdata*rxdata)/N
|
||||
rxsig=sqrt(rx2av-rxav*rxav)
|
||||
rxdata=rxdata/rxsig
|
||||
! To match the metric to the channel, s should be set to the noise standard deviation.
|
||||
! For now, set s to the value that optimizes decode probability near threshold.
|
||||
! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
|
||||
! magnitude in UER
|
||||
if( s .lt. 0 ) then
|
||||
ss=sigma
|
||||
else
|
||||
ss=s
|
||||
endif
|
||||
|
||||
llr=2.0*rxdata/(ss*ss)
|
||||
lratio=exp(llr)
|
||||
yy=rxdata
|
||||
|
||||
! max_iterations is max number of belief propagation iterations
|
||||
! call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
|
||||
! call amsdecode(yy, max_iterations, decoded, niterations)
|
||||
! call bitflipmsk144(rxdata, decoded, niterations)
|
||||
call bpdecode144(llr, max_iterations, decoded, niterations)
|
||||
|
||||
! If the decoder finds a valid codeword, niterations will be .ge. 0.
|
||||
if( niterations .ge. 0 ) then
|
||||
call extractmessage144(decoded,msgreceived,nhashflag)
|
||||
if( nhashflag .ne. 1 ) then
|
||||
nbadhash=nbadhash+1
|
||||
endif
|
||||
nueflag=0
|
||||
|
||||
! Check the message plus hash against what was sent.
|
||||
do i=1,K
|
||||
if( msgbits(i) .ne. decoded(i) ) then
|
||||
nueflag=1
|
||||
endif
|
||||
enddo
|
||||
if( nhashflag .eq. 1 .and. nueflag .eq. 0 ) then
|
||||
ngood=ngood+1
|
||||
else if( nhashflag .eq. 1 .and. nueflag .eq. 1 ) then
|
||||
nue=nue+1;
|
||||
endif
|
||||
endif
|
||||
enddo
|
||||
|
||||
write(*,"(f4.1,1x,i8,1x,i8,1x,i8,1x,f5.2)") db,ngood,nue,nbadhash,ss
|
||||
|
||||
enddo
|
||||
|
||||
end program ldpcsim
|
||||
|
|
@ -9,8 +9,9 @@ character*80 prefix
|
|||
character*85 pchk_file,gen_file
|
||||
character*8 arg
|
||||
integer*1, allocatable :: codeword(:), decoded(:), message(:)
|
||||
real*8, allocatable :: lratio(:), rxdata(:)
|
||||
real*8, allocatable :: lratio(:), rxdata(:), llr(:)
|
||||
integer ihash
|
||||
integer*1 hardbits(32)
|
||||
|
||||
nargs=iargc()
|
||||
if(nargs.ne.7) then
|
||||
|
|
@ -36,45 +37,48 @@ pchk_file=trim(prefix)//".pchk"
|
|||
gen_file=trim(prefix)//".gen"
|
||||
|
||||
rate=real(K)/real(N)
|
||||
write(*,*) "rate: ",rate
|
||||
! don't count hash bits as data bits
|
||||
!rate=5.0/real(N)
|
||||
|
||||
write(*,*) "rate: ",rate
|
||||
write(*,*) "pchk file: ",pchk_file
|
||||
write(*,*) "niter= ",max_iterations," ndither= ",max_dither," s= ",s
|
||||
|
||||
allocate ( codeword(N), decoded(K), message(K) )
|
||||
allocate ( lratio(N), rxdata(N) )
|
||||
allocate ( lratio(N), rxdata(N), llr(N) )
|
||||
call init_ldpc(trim(pchk_file)//char(0),trim(gen_file)//char(0))
|
||||
|
||||
msg="K9AN K1JT RRR"
|
||||
irpt=62
|
||||
msg="K1JT K9AN RRR "
|
||||
irpt=14
|
||||
call hash(msg,22,ihash)
|
||||
ihash=iand(ihash,1023) !10-bit hash
|
||||
ig=64*ihash + irpt !6-bit report
|
||||
ihash=iand(ihash,4095) !12-bit hash
|
||||
ig=16*ihash + irpt !4-bit report
|
||||
write(*,*) irpt,ihash,ig
|
||||
|
||||
do i=1,16
|
||||
message(i)=iand(1,ishft(ig,1-i))
|
||||
enddo
|
||||
|
||||
call ldpc_encode(message,codeword)
|
||||
write(*,'(16i1)') message
|
||||
!call ldpc_encode(message,codeword)
|
||||
!write(*,'(32i1)') codeword
|
||||
call encode_msk40(message,codeword)
|
||||
write(*,'(32i1)') codeword
|
||||
call init_random_seed()
|
||||
|
||||
write(*,*) "Eb/N0 ngood nundetected nbadhash"
|
||||
do idb = -6, 14
|
||||
!do idb = 14, 14
|
||||
db=idb/2.0-1.0
|
||||
sigma=1/sqrt( 2*rate*(10**(db/10.0)) )
|
||||
ngood=0
|
||||
nue=0
|
||||
nbadhash=0
|
||||
|
||||
itsum=0
|
||||
do itrial=1, ntrials
|
||||
call sgran()
|
||||
call sgran()
|
||||
! Create a realization of a noisy received word
|
||||
do i=1,N
|
||||
rxdata(i) = 2.0*(codeword(i)-0.5) + sigma*gran()
|
||||
!write(*,*) i,gran()
|
||||
rxdata(i) = 2.0*codeword(i)-1.0 + sigma*gran()
|
||||
enddo
|
||||
|
||||
! Correct signal normalization is important for this decoder.
|
||||
|
|
@ -82,34 +86,27 @@ call sgran()
|
|||
rx2av=sum(rxdata*rxdata)/N
|
||||
rxsig=sqrt(rx2av-rxav*rxav)
|
||||
rxdata=rxdata/rxsig
|
||||
! To match the metric to the channel, s should be set to the noise standard deviation.
|
||||
! For now, set s to the value that optimizes decode probability near threshold.
|
||||
! The s parameter can be tuned to trade a few tenth's dB of threshold for an order of
|
||||
! magnitude in UER
|
||||
if( s .le. 0 ) then
|
||||
ss=sigma
|
||||
else
|
||||
ss=s
|
||||
endif
|
||||
|
||||
do i=1,N
|
||||
lratio(i)=exp(2.0*rxdata(i)/(ss*ss))
|
||||
enddo
|
||||
llr=2.0*rxdata/(ss*ss)
|
||||
lratio=exp(llr)
|
||||
|
||||
! max_iterations is max number of belief propagation iterations
|
||||
call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
|
||||
! call ldpc_decode(lratio, decoded, max_iterations, niterations, max_dither, ndither)
|
||||
call bpdecode40(llr, max_iterations, decoded, niterations)
|
||||
! If the decoder finds a valid codeword, niterations will be .ge. 0.
|
||||
if( niterations .ge. 0 ) then
|
||||
nueflag=0
|
||||
nhashflag=0
|
||||
|
||||
imsg=0
|
||||
do i=1,16
|
||||
imsg=ishft(imsg,1)+iand(1,decoded(17-i))
|
||||
enddo
|
||||
nrxrpt=iand(imsg,63)
|
||||
nrxhash=(imsg-nrxrpt)/64
|
||||
|
||||
nrxrpt=iand(imsg,15)
|
||||
nrxhash=(imsg-nrxrpt)/16
|
||||
if( nrxhash .ne. ihash ) then
|
||||
nbadhash=nbadhash+1
|
||||
nhashflag=1
|
||||
|
|
@ -124,13 +121,24 @@ call sgran()
|
|||
|
||||
if( nhashflag .eq. 0 .and. nueflag .eq. 0 ) then
|
||||
ngood=ngood+1
|
||||
itsum=itsum+niterations
|
||||
else if( nhashflag .eq. 0 .and. nueflag .eq. 1 ) then
|
||||
nue=nue+1;
|
||||
endif
|
||||
else
|
||||
hardbits=0
|
||||
where(llr .gt. 0) hardbits=1
|
||||
! write(*,'(32i1)') hardbits
|
||||
! write(*,'(32i1)') codeword
|
||||
isum=0
|
||||
do i=1,32
|
||||
if( hardbits(i) .ne. codeword(i) ) isum=isum+1
|
||||
enddo
|
||||
! write(*,*) 'number of errors ',isum
|
||||
endif
|
||||
enddo
|
||||
|
||||
write(*,"(f4.1,1x,i8,1x,i8,1x,i8)") db,ngood,nue,nbadhash
|
||||
avits=real(itsum)/real(ngood+0.1)
|
||||
write(*,"(f4.1,1x,i8,1x,i8,1x,i8,1x,f8.2,1x,f8.1)") db,ngood,nue,nbadhash,ss,avits
|
||||
|
||||
enddo
|
||||
|
||||
|
|
@ -39,8 +39,7 @@ program msk144sim
|
|||
h=default_header(12000,NMAX)
|
||||
|
||||
ichk=0
|
||||
encode_exe_file="./encode "
|
||||
call genmsk144(msg,ichk,msgsent,itone,itype,pchk_file,ldpc_msg_file,encode_exe_file)
|
||||
call genmsk144(msg,ichk,msgsent,itone,itype)
|
||||
twopi=8.d0*atan(1.d0)
|
||||
|
||||
nsym=144
|
||||
|
|
|
|||
Loading…
Reference in New Issue