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Fix Viterbi decoder for punctured codes

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This commit is contained in:
Andy 2018-01-26 17:07:15 -03:00
parent db65ea418c
commit e63c0f9f88
2 changed files with 18 additions and 9 deletions
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17
NXDNConvolution.cpp Normal file → Executable file
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@ -27,12 +27,12 @@ const unsigned char BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U
#define WRITE_BIT1(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
#define READ_BIT1(p,i) (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
const uint8_t BRANCH_TABLE1[] = {0U, 0U, 0U, 0U, 2U, 2U, 2U, 2U};
const uint8_t BRANCH_TABLE2[] = {0U, 2U, 2U, 0U, 0U, 2U, 2U, 0U};
const uint8_t BRANCH_TABLE1[] = {0U, 0U, 0U, 0U, 1U, 1U, 1U, 1U};
const uint8_t BRANCH_TABLE2[] = {0U, 1U, 1U, 0U, 0U, 1U, 1U, 0U};
const unsigned int NUM_OF_STATES_D2 = 8U;
const unsigned int NUM_OF_STATES = 16U;
const uint32_t M = 4U;
const uint32_t M = 2U;
const unsigned int K = 5U;
CNXDNConvolution::CNXDNConvolution() :
@ -72,7 +72,16 @@ void CNXDNConvolution::decode(uint8_t s0, uint8_t s1)
for (uint8_t i = 0U; i < NUM_OF_STATES_D2; i++) {
uint8_t j = i * 2U;
uint16_t metric = (BRANCH_TABLE1[i] ^ s0) + (BRANCH_TABLE2[i] ^ s1);
uint16_t metric0 = 0;
uint16_t metric1 = 0;
if (s0 != 99U)
metric0 = (BRANCH_TABLE1[i] ^ s0);
if (s1 != 99U)
metric1 = (BRANCH_TABLE2[i] ^ s1);
uint16_t metric = metric0 + metric1;
uint16_t m0 = m_oldMetrics[i] + metric;
uint16_t m1 = m_oldMetrics[i + NUM_OF_STATES_D2] + (M - metric);

10
NXDNSACCH.cpp Normal file → Executable file
View file

@ -86,14 +86,14 @@ bool CNXDNSACCH::decode(const unsigned char* data)
unsigned int index = 0U;
for (unsigned int i = 0U; i < NXDN_SACCH_LENGTH_BITS; i++) {
if (n == PUNCTURE_LIST[index]) {
::strcat(text, "1, ");
temp2[n++] = 1U;
::strcat(text, "X, ");
temp2[n++] = 99U;
index++;
}
bool b = READ_BIT1(temp1, i);
temp2[n++] = b ? 2U : 0U;
::strcat(text, b ? "2, " : "0, ");
temp2[n++] = b ? 1U : 0U;
::strcat(text, b ? "1, " : "0, ");
}
LogMessage(text);
@ -109,7 +109,7 @@ bool CNXDNSACCH::decode(const unsigned char* data)
conv.decode(s0, s1);
}
conv.chainback(m_data, 36U);
conv.chainback(m_data, 32U);
CUtils::dump("NXDN, SACCH decoded", m_data, 5U);