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first pass LDPC decoder working with QAM16

dr-qam16-cport
drowe67 2024-04-05 19:55:30 +10:30 committed by David Rowe
parent c0821c86e7
commit 1b2a4a797b
1 changed files with 17 additions and 2 deletions
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19
src/mpdecode_core.c
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@ -27,11 +27,21 @@
#define QPSK_CONSTELLATION_SIZE 4
#define QPSK_BITS_PER_SYMBOL 2
/* QPSK constellation for symbol likelihood calculations */
/* Constellations for symbol likelihood calculations */
static COMP S_matrix[] = {
static COMP S_matrix_qpsk[] = {
{1.0f, 0.0f}, {0.0f, 1.0f}, {0.0f, -1.0f}, {-1.0f, 0.0f}};
static COMP S_matrix_qam16[] = {
{4.4721e-01, 2.7756e-17}, {8.9443e-01, 4.4721e-01},
{8.9443e-01, -4.4721e-01}, {1.3416e+00, 1.1102e-16},
{2.7756e-17, -4.4721e-01}, {-4.4721e-01, -8.9443e-01},
{4.4721e-01, -8.9443e-01}, {1.1102e-16, -1.3416e+00},
{-2.7756e-17, 4.4721e-01}, {4.4721e-01, 8.9443e-01},
{-4.4721e-01, 8.9443e-01}, {-1.1102e-16, 1.3416e+00},
{-4.4721e-01, -2.7756e-17}, {-8.9443e-01, -4.4721e-01},
{-8.9443e-01, 4.4721e-01}, {-1.3416e+00, -1.1102e-16}};
// c_nodes will be an array of NumberParityBits of struct c_node
// Each c_node contains an array of <degree> c_sub_node elements
// This structure reduces the indexing calclations in SumProduct()
@ -634,6 +644,11 @@ void symbols_to_llrs(float llr[], COMP rx_psk_symbols[], float rx_amps[],
float symbol_likelihood[nsyms * constellation_points];
float bit_likelihood[nsyms * bps];
COMP *S_matrix;
assert((bps == 2) || (bps == 4));
if (bps == 2) S_matrix = S_matrix_qpsk;
if (bps == 4) S_matrix = S_matrix_qam16;
Demod2D(symbol_likelihood, rx_psk_symbols, S_matrix, constellation_points,
EsNo, rx_amps, mean_amp, nsyms);
Somap(bit_likelihood, symbol_likelihood, constellation_points, bps, nsyms);