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Enable extended correlation for Glonass G1

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This commit is contained in:
Javier Arribas
2025-12-17 17:05:59 +01:00
parent 8e4343d5ec
commit 330cfae079
5 changed files with 35 additions and 75 deletions
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src/algorithms/telemetry_decoder/gnuradio_blocks/glonass_l1_ca_telemetry_decoder_gs.cc
+22 -62
View File
@@ -87,25 +87,7 @@ glonass_l1_ca_telemetry_decoder_gs::glonass_l1_ca_telemetry_decoder_gs(
d_satellite = Gnss_Satellite(satellite.get_system(), satellite.get_PRN());
LOG(INFO) << "Initializing GLONASS L1 CA TELEMETRY DECODING";
// preamble bits to sampled symbols
int32_t n = 0;
for (uint16_t d_preambles_bit : d_preambles_bits)
{
for (uint32_t j = 0; j < GLONASS_GNAV_TELEMETRY_SYMBOLS_PER_PREAMBLE_BIT; j++)
{
if (d_preambles_bit == 1)
{
d_preambles_symbols[n] = 1;
}
else
{
d_preambles_symbols[n] = -1;
}
n++;
}
}
d_symbol_history.set_capacity(GLONASS_GNAV_STRING_SYMBOLS);
d_symbol_history.set_capacity(GLONASS_GNAV_STRING_BIBINARY_WITH_PREABLE);
if (d_dump_crc_stats)
{
@@ -159,43 +141,15 @@ glonass_l1_ca_telemetry_decoder_gs::~glonass_l1_ca_telemetry_decoder_gs()
void glonass_l1_ca_telemetry_decoder_gs::decode_string(const double *frame_symbols, int32_t frame_length, double cn0)
{
double chip_acc = 0.0;
int32_t chip_acc_counter = 0;
// 1. Transform from symbols to bits
std::string bi_binary_code;
bi_binary_code.reserve(frame_length / GLONASS_GNAV_TELEMETRY_SYMBOLS_PER_BIT);
std::string relative_code;
relative_code.reserve(GLONASS_GNAV_STRING_BITS);
std::string data_bits;
data_bits.reserve(GLONASS_GNAV_STRING_BITS + 1);
// Group samples into bi-binary code
for (int32_t i = 0; i < (frame_length); i++)
{
chip_acc += frame_symbols[i];
chip_acc_counter += 1;
if (chip_acc_counter == (GLONASS_GNAV_TELEMETRY_SYMBOLS_PER_BIT))
{
if (chip_acc > 0)
{
bi_binary_code.push_back('1');
chip_acc_counter = 0;
chip_acc = 0;
}
else
{
bi_binary_code.push_back('0');
chip_acc_counter = 0;
chip_acc = 0;
}
}
}
// Convert from bi-binary code to relative code
for (int32_t i = 0; i < (GLONASS_GNAV_STRING_BITS); i++)
{
if (bi_binary_code[2 * i] == '1' && bi_binary_code[2 * i + 1] == '0')
if (frame_symbols[2 * i] >0 && frame_symbols[2 * i + 1] <=0)
{
relative_code.push_back('1');
}
@@ -324,6 +278,7 @@ int glonass_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribu
const auto **in = reinterpret_cast<const Gnss_Synchro **>(&input_items[0]); // Get the input buffer pointer
Gnss_Synchro current_symbol{}; // structure to save the synchronization information and send the output object to the next block
// 1. Copy the current tracking output
current_symbol = in[0][0];
d_symbol_history.push_back(current_symbol); // add new symbol to the symbol queue
@@ -332,26 +287,28 @@ int glonass_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribu
d_flag_preamble = false;
if (static_cast<int32_t>(d_symbol_history.size()) >= d_symbols_per_preamble)
if (static_cast<int32_t>(d_symbol_history.size()) >= GLONASS_GNAV_PREAMBLE_LENGTH_BITS)
{
// ******* preamble correlation ********
for (int32_t i = 0; i < d_symbols_per_preamble; i++)
for (int32_t i = 0; i < GLONASS_GNAV_PREAMBLE_LENGTH_BITS; i++)
{
if (d_symbol_history[i].Prompt_I < 0.0) // symbols clipping
{
corr_value -= d_preambles_symbols[i];
corr_value -= d_preambles_bits[i];
}
else
{
corr_value += d_preambles_symbols[i];
corr_value += d_preambles_bits[i];
}
}
// std::cout<< "Preamble correlation value: " << corr_value << std::endl;
}
// ******* frame sync ******************
if (d_stat == 0) // no preamble information
{
if (abs(corr_value) >= d_symbols_per_preamble)
if (abs(corr_value) >= GLONASS_GNAV_PREAMBLE_LENGTH_BITS)
{
// Record the preamble sample stamp
d_preamble_index = d_sample_counter;
@@ -359,17 +316,19 @@ int glonass_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribu
// Enter into frame pre-detection status
d_stat = 1;
d_preamble_time_samples = d_symbol_history[0].Tracking_sample_counter; // record the preamble sample stamp
//std::cout<< "Preamble detection for GLONASS L1 C/A SAT " << this->d_satellite;
}
}
else if (d_stat == 1) // possible preamble lock
{
if (abs(corr_value) >= d_symbols_per_preamble)
if (abs(corr_value) >= GLONASS_GNAV_PREAMBLE_LENGTH_BITS)
{
// check preamble separation
preamble_diff = static_cast<int32_t>(d_sample_counter - d_preamble_index);
// Record the PRN start sample index associated to the preamble
d_preamble_time_samples = static_cast<double>(d_symbol_history[0].Tracking_sample_counter);
if (abs(preamble_diff - GLONASS_GNAV_PREAMBLE_PERIOD_SYMBOLS) == 0)
if (abs(preamble_diff - GLONASS_GNAV_PREAMBLE_PERIOD_BITS) == 0)
{
// try to decode frame
LOG(INFO) << "Starting string decoder for GLONASS L1 C/A SAT " << this->d_satellite;
@@ -379,34 +338,35 @@ int glonass_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribu
}
else
{
if (preamble_diff > GLONASS_GNAV_PREAMBLE_PERIOD_SYMBOLS)
if (preamble_diff > GLONASS_GNAV_PREAMBLE_PERIOD_BITS)
{
d_stat = 0; // start again
}
DLOG(INFO) << "Failed string decoder for GLONASS L1 C/A SAT " << this->d_satellite;
//std::cout<< "Failed string decoder for GLONASS L1 C/A SAT " << this->d_satellite<<". Preamble separation: " << preamble_diff << " samples.";
}
}
}
else if (d_stat == 2)
{
// FIXME: The preamble index marks the first symbol of the string count. Here I just wait for another full string to be received before processing
if (d_sample_counter == d_preamble_index + static_cast<uint64_t>(GLONASS_GNAV_STRING_SYMBOLS))
if (d_sample_counter == d_preamble_index + static_cast<uint64_t>(GLONASS_GNAV_STRING_BIBINARY_WITH_PREABLE))
{
// NEW GLONASS string received
// 0. fetch the symbols into an array
const int32_t string_length = GLONASS_GNAV_STRING_SYMBOLS - d_symbols_per_preamble;
std::array<double, GLONASS_GNAV_DATA_SYMBOLS> string_symbols{};
const int32_t string_length = GLONASS_GNAV_STRING_BIBINARY_WITH_PREABLE - GLONASS_GNAV_PREAMBLE_LENGTH_BITS;
std::array<double, GLONASS_GNAV_STRING_BIBINARY_WITH_PREABLE - GLONASS_GNAV_PREAMBLE_LENGTH_BITS> string_symbols{};
// ******* SYMBOL TO BIT *******
for (int32_t i = 0; i < string_length; i++)
{
if (corr_value > 0)
{
string_symbols[i] = d_symbol_history[i + d_symbols_per_preamble].Prompt_I; // because last symbol of the preamble is just received now!
string_symbols[i] = d_symbol_history[i + GLONASS_GNAV_PREAMBLE_LENGTH_BITS].Prompt_I; // because last symbol of the preamble is just received now!
}
else
{
string_symbols[i] = -d_symbol_history[i + d_symbols_per_preamble].Prompt_I; // because last symbol of the preamble is just received now!
string_symbols[i] = -d_symbol_history[i + GLONASS_GNAV_PREAMBLE_LENGTH_BITS].Prompt_I; // because last symbol of the preamble is just received now!
}
}
@@ -449,7 +409,7 @@ int glonass_l1_ca_telemetry_decoder_gs::general_work(int noutput_items __attribu
}
else // if there is not a new preamble, we define the TOW of the current symbol
{
d_TOW_at_current_symbol = d_TOW_at_current_symbol + GLONASS_L1_CA_CODE_PERIOD_S;
d_TOW_at_current_symbol = d_TOW_at_current_symbol + GLONASS_L1_CA_SYMBOL_PERIOD_S;
}
// if (d_flag_frame_sync == true && d_nav.flag_TOW_set==true && d_nav.get_flag_CRC_test() == true)
src/algorithms/telemetry_decoder/gnuradio_blocks/glonass_l1_ca_telemetry_decoder_gs.h
+1 -8
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@@ -70,17 +70,10 @@ private:
glonass_l1_ca_telemetry_decoder_gs(const Gnss_Satellite &satellite, const Tlm_Conf &conf);
const std::array<uint16_t, GLONASS_GNAV_PREAMBLE_LENGTH_BITS> d_preambles_bits{GLONASS_GNAV_PREAMBLE};
const int32_t d_symbols_per_preamble = GLONASS_GNAV_PREAMBLE_LENGTH_SYMBOLS;
const std::array<int16_t, GLONASS_GNAV_PREAMBLE_LENGTH_BITS> d_preambles_bits{GLONASS_GNAV_PREAMBLE_SAMPLES};
void decode_string(const double *symbols, int32_t frame_length, double cn0);
// Help with coherent tracking
// Preamble decoding
std::array<int32_t, GLONASS_GNAV_PREAMBLE_LENGTH_SYMBOLS> d_preambles_symbols{};
// Storage for incoming data
boost::circular_buffer<Gnss_Synchro> d_symbol_history;
src/algorithms/telemetry_decoder/gnuradio_blocks/glonass_l2_ca_telemetry_decoder_gs.cc
+3 -3
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@@ -104,7 +104,7 @@ glonass_l2_ca_telemetry_decoder_gs::glonass_l2_ca_telemetry_decoder_gs(
}
}
d_symbol_history.set_capacity(GLONASS_GNAV_STRING_SYMBOLS);
d_symbol_history.set_capacity(GLONASS_GNAV_STRING_SYMBOLS_WITH_PREABLE);
if (d_dump_crc_stats)
{
@@ -411,11 +411,11 @@ int glonass_l2_ca_telemetry_decoder_gs::general_work(int noutput_items __attribu
else if (d_stat == 2)
{
// FIXME: The preamble index marks the first symbol of the string count. Here I just wait for another full string to be received before processing
if (d_sample_counter == d_preamble_index + static_cast<uint64_t>(GLONASS_GNAV_STRING_SYMBOLS))
if (d_sample_counter == d_preamble_index + static_cast<uint64_t>(GLONASS_GNAV_STRING_SYMBOLS_WITH_PREABLE))
{
// NEW GLONASS string received
// 0. fetch the symbols into an array
const int32_t string_length = GLONASS_GNAV_STRING_SYMBOLS - d_symbols_per_preamble;
const int32_t string_length = GLONASS_GNAV_STRING_SYMBOLS_WITH_PREABLE - d_symbols_per_preamble;
std::array<double, GLONASS_GNAV_DATA_SYMBOLS> string_symbols{};
// ******* SYMBOL TO BIT *******
src/algorithms/tracking/gnuradio_blocks/dll_pll_veml_tracking.cc
+1 -1
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@@ -2058,7 +2058,7 @@ int dll_pll_veml_tracking::general_work(int noutput_items __attribute__((unused)
run_dll_pll();
update_tracking_vars();
check_carrier_phase_coherent_initialization();
if ((d_current_data_symbol == 0) || (d_signal_type == "1G") || (d_signal_type == "2G")) // Glonass telemetry decoder require symbols instead of bits
if ((d_current_data_symbol == 0) || (d_signal_type == "2G")) // Glonass telemetry decoder require symbols instead of bits
{
// enable write dump file this cycle (valid DLL/PLL cycle)
log_data();
src/core/system_parameters/GLONASS_L1_L2_CA.h
+8 -1
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@@ -78,6 +78,7 @@ constexpr double GLONASS_L1_CA_DFREQ_HZ = DFRQ1_GLO; //!< Freq Bias for G
constexpr double GLONASS_L1_CA_CODE_RATE_CPS = 0.511e6; //!< GLONASS L1 C/A code rate [chips/s]
constexpr double GLONASS_L1_CA_CODE_LENGTH_CHIPS = 511.0; //!< GLONASS L1 C/A code length [chips]
constexpr double GLONASS_L1_CA_CODE_PERIOD_S = 0.001; //!< GLONASS L1 C/A code period [seconds]
constexpr double GLONASS_L1_CA_SYMBOL_PERIOD_S = 0.01; //!< GLONASS L1 C/A symbol period [seconds]
constexpr double GLONASS_L1_CA_CHIP_PERIOD_S = 1.9569e-06; //!< GLONASS L1 C/A chip period [seconds]
constexpr double GLONASS_L1_CA_SYMBOL_RATE_BPS = 1000.0;
@@ -93,16 +94,22 @@ constexpr int32_t GLONASS_L1_CA_HISTORY_DEEP = 100;
{ \
1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0}
#define GLONASS_GNAV_PREAMBLE_SAMPLES \
{ \
1, 1, 1, 1, 1, -1, -1, -1, 1, 1, -1, 1, 1, 1, -1, 1, -1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, 1, 1, -1}
constexpr char GLONASS_GNAV_PREAMBLE_STR[301] = "111111111111111111111111111111111111111111111111110000000000000000000000000000001111111111111111111100000000001111111111111111111111111111110000000000111111111100000000001111111111000000000000000000000000000000000000000011111111110000000000000000000011111111110000000000111111111111111111110000000000";
constexpr double GLONASS_GNAV_PREAMBLE_DURATION_S = 0.300;
constexpr int32_t GLONASS_GNAV_PREAMBLE_LENGTH_BITS = 30;
constexpr int32_t GLONASS_GNAV_PREAMBLE_LENGTH_SYMBOLS = 300;
constexpr int32_t GLONASS_GNAV_PREAMBLE_PERIOD_SYMBOLS = 2000;
constexpr int32_t GLONASS_GNAV_PREAMBLE_PERIOD_BITS = 200;
constexpr int32_t GLONASS_GNAV_TELEMETRY_RATE_BITS_SECOND = 50; //!< NAV message bit rate [bits/s]
constexpr int32_t GLONASS_GNAV_TELEMETRY_SYMBOLS_PER_BIT = 10;
constexpr int32_t GLONASS_GNAV_TELEMETRY_SYMBOLS_PER_PREAMBLE_BIT = 10;
constexpr int32_t GLONASS_GNAV_TELEMETRY_RATE_SYMBOLS_SECOND = GLONASS_GNAV_TELEMETRY_RATE_BITS_SECOND * GLONASS_GNAV_TELEMETRY_SYMBOLS_PER_BIT; //!< NAV message bit rate [symbols/s]
constexpr int32_t GLONASS_GNAV_STRING_SYMBOLS = 2000; //!< Number of bits per string in the GNAV message (85 data bits + 30 time mark bits) [bits]
constexpr int32_t GLONASS_GNAV_STRING_SYMBOLS_WITH_PREABLE = 2000;
constexpr int32_t GLONASS_GNAV_STRING_BIBINARY_WITH_PREABLE = 200; //!< Number of bits per string in the GNAV message (85 data bits + 30 time mark bits) [bits]
constexpr int32_t GLONASS_GNAV_STRING_BITS = 85; //!< Number of bits per string in the GNAV message (85 data bits + 30 time mark bits) [bits]
constexpr int32_t GLONASS_GNAV_HAMMING_CODE_BITS = 8; //!< Number of bits in hamming code sequence of GNAV message
constexpr int32_t GLONASS_GNAV_DATA_SYMBOLS = 1700; // STRING DATA WITHOUT PREAMBLE