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Gray Mapping

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zeefaad
2025-10-23 13:03:14 +02:00
parent b4a9fc0cec
commit d3e45f775b
5 changed files with 272 additions and 140 deletions
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60
QAM/qam.c
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@ -14,27 +14,23 @@ struct qam_system_s {
double Ts; // Temps d'échantillionage
int N; // Nombre d'échantillions
double Fc; // Fréquence de la porteuse
double complex** constellation; // Tableau de symboles I + j Q
double complex* constellation; // Tableau de symboles I + j Q 1D
};
typedef struct qam_system_s qam_system;
// Initialisation de la constellation (double tableau de taille sqrt(M)),
// ToDo : changer à un tableau à 1 dimension pour éviter de calculer sqrt(M)
void init_constellation (qam_system* qam) {
int sm = (int)sqrt(qam->M);
qam->constellation = (double complex**)malloc(sizeof(double complex*) * sm);
for (int i = 0; i < sm; i++) {
qam->constellation[i] = (double complex*)malloc(sizeof(double complex) * sm);
}
qam->constellation = (double complex*)malloc(sizeof(double complex) * qam->M);
double norm_factor = sqrt((double)(qam->M - 1) / 3.0); // Pour puissance unitaire
for (int i = 0; i < sm; i++) {
double complex ip = -(sm - 1) + 2 * i;
double ip = -(sm - 1) + 2 * i;
for (int j = 0; j < sm; j++) {
double complex qp = -(sm - 1) + 2 * j;
qam->constellation[i][j] = (ip + I * qp) / norm_factor;
double qp = -(sm - 1) + 2 * j;
int idx = i * sm + j;
qam->constellation[idx] = (ip + I * qp) / norm_factor;
}
}
}
@ -81,27 +77,15 @@ void demodulate(qam_system* qam, double complex* s, int nb_symbols, uint8_t* bit
double min_d = INFINITY;
int i_cl = 0;
int j_cl = 0;
for (int i = 0; i < sm; i++) {
for (int j = 0; j < sm; j++) {
double d = cabs(r - qam->constellation[i][j]);
if (d < min_d) {
min_d = d;
i_cl = i;
j_cl = j;
}
for (int idx = 0; idx < qam->M; idx++) {
double d = cabs(r - qam->constellation[idx]);
if (d < min_d) {
min_d = d;
i_cl = idx / sm;
j_cl = idx % sm;
}
}
/*
// Ancienne methode (non gray)
// index du symbole (id) : même mappage que dans bits_to_symbols()
int id = i_cl * sm + j_cl;
for (int b = 0; b < qam->k; b++) {
bits_hat[k * qam->k + b] = (id >> (qam->k - 1 - b)) & 1;
}
*/
// Gray mapping
if (qam->k % 2 != 0) {
printf("demodulate : k pair (k = %d)\n", qam->k);
@ -141,20 +125,6 @@ void add_noise (double complex* s, int len, double sigma) {
}
// Changer le tableau de bits en boolen ou alors la represenation binaire et shifter pour extraire les bits (pas bien si M plus grand)
/*void bits_to_symbols (qam_system* qam, uint8_t* bits, int nb_bits, double complex* symbols) {
int nb_symbols = nb_bits / qam->k;
int sm = sqrt(qam->M);
for (int k = 0; k < nb_symbols; k++) {
int id = 0;
for (int b = 0 ; b < qam->k; b++) {
id = id * 2 + bits[k * qam->k + b];
}
int i = id / sm;
int j = id % sm;
symbols[k] = qam->constellation[i][j];
}
}*/
void bits_to_symbols (qam_system* qam, uint8_t* bits, int nb_bits, double complex* symbols) {
int nb_symbols = nb_bits / qam->k;
int sm = (int)sqrt(qam->M);
@ -182,7 +152,7 @@ void bits_to_symbols (qam_system* qam, uint8_t* bits, int nb_bits, double comple
printf("bits_to_symbols : IOOR i_gray = %d j_gray = %d sm = %d \n", i_gray, j_gray, sm);
exit(1);
}
symbols[sym] = qam->constellation[i_gray][j_gray];
symbols[sym] = qam->constellation[i_gray * sm + j_gray];
}
}
@ -211,7 +181,8 @@ void fill_constellation_data(qam_system* qam, FILE *fp_ref) {
int sm = (int)sqrt(qam->M);
for (int i = 0; i < sm; i++) {
for (int j = 0; j < sm; j++) {
fprintf(fp_ref, "% .8f % .8f\n", creal(qam->constellation[i][j]), cimag(qam->constellation[i][j]));
int idx = i * sm + j;
fprintf(fp_ref, "% .8f % .8f\n", creal(qam->constellation[idx]), cimag(qam->constellation[idx]));
}
}
}
@ -241,6 +212,7 @@ void free_constellation(qam_system* qam) {
for (int i = 0; i < sm; i++)
free(qam->constellation[i]);
free(qam->constellation);
}
int main () {