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clean qam

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zeefaad
2025-10-21 12:42:32 +02:00
parent 12b5aa5071
commit b7952fc38a
8 changed files with 2309 additions and 8274 deletions
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268
QAM/qam.c
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@ -39,38 +39,6 @@ void init_constellation (qam_system* qam) {
}
}
// Calcul du bruit gaussien pour un sigma donné
// Formule de Box-Muller
double gaussian_noise (double sigma) {
double u1 = (rand() + 1) / ((double)RAND_MAX + 2);
double u2 = (rand() + 1) / ((double)RAND_MAX + 2);
return sigma * sqrt(-2 * log(u1)) * cos(2 * M_PI * u2);
}
// Ajout du bruit
void add_noise (double complex* s, int len, double sigma) {
for (int i = 0; i < len; i++) {
double nr = gaussian_noise(sigma);
double ni = gaussian_noise(sigma);
s[i] += nr + I * ni;
}
}
// 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];
}
}
// Modulation QAM
void modulate (qam_system* qam, double complex* symbols, int nb_symbols, double complex* s) {
for (int k = 0; k < nb_symbols; k++) {
@ -121,63 +89,40 @@ void demodulate(qam_system* qam, double complex* s, int nb_symbols, uint8_t* bit
}
}
// PLL pour corriger le déphasage
void pll_qam_symbol(qam_system* qam, double complex* symbols_rx, double complex* r_corr, int nb_symbols, double Kp, double Ki, double alpha, FILE* fp_error) {
double phase_est = 0.0;
double integrator = 0.0;
double filtered_error = 0.0;
// Calcul du bruit gaussien pour un sigma donné
// Formule de Box-Muller
double gaussian_noise (double sigma) {
double u1 = (rand() + 1) / ((double)RAND_MAX + 2);
double u2 = (rand() + 1) / ((double)RAND_MAX + 2);
return sigma * sqrt(-2 * log(u1)) * cos(2 * M_PI * u2);
}
int sm = (int)sqrt(qam->M);
int N = qam->N;
for (int k = 0; k < nb_symbols; k++) {
double complex r_symbol = 0;
for (int n = 0; n < N; n++) {
int idx = k * N + n;
r_symbol += symbols_rx[idx] * cexp(-2.0 * I * M_PI * qam->Fc * ((double)idx / qam->Fs));
}
r_symbol /= N;
r_symbol *= cexp(-I * phase_est);
double min_d = INFINITY;
double complex closest = 0;
for (int i = 0; i < sm; i++) {
for (int j = 0; j < sm; j++) {
double d = cabs(r_symbol - qam->constellation[i][j]);
if (d < min_d) {
min_d = d;
closest = qam->constellation[i][j];
}
}
}
double error = carg(r_symbol * conj(closest));
filtered_error = (1.0 - alpha) * filtered_error + alpha * error;
integrator += Ki * filtered_error;
phase_est += Kp * filtered_error + integrator;
// Écriture de l'erreur PLL dans le fichier
if (fp_error) {
fprintf(fp_error, "%d % .8f\n", k, 100 * filtered_error);
fflush(fp_error);
}
for (int n = 0; n < N; n++) {
int idx = k * N + n;
r_corr[idx] = symbols_rx[idx] * cexp(-I * phase_est);
}
// Ajout du bruit
void add_noise (double complex* s, int len, double sigma) {
//double signal_power = (2.0/3.0)*(qam.M-1);
//double snr_dB = 5; // SNR en dB
//double snr_lin = pow(10.0, snr_dB / 10.0);
//double sigma = sqrt(signal_power / snr_lin);
for (int i = 0; i < len; i++) {
double nr = gaussian_noise(sigma);
double ni = gaussian_noise(sigma);
s[i] += nr + I * ni;
}
}
// Libération de la mémoire
void free_constellation(qam_system* qam) {
int sm = (int)sqrt(qam->M);
for (int i = 0; i < sm; i++)
free(qam->constellation[i]);
free(qam->constellation);
// 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];
}
}
double compare_bits(uint8_t* bits1, uint8_t* bits2, int nb_bits) {
@ -188,75 +133,72 @@ double compare_bits(uint8_t* bits1, uint8_t* bits2, int nb_bits) {
return (double)errors / nb_bits;
}
// Minimise le BER (si la pll s'est lockée de maniere déphasée de k*pi/2)
void demodulate2(qam_system* qam, double complex* r_corr, int nb_symbols, uint8_t* input_bits, uint8_t* output_bits, FILE* fp_constel) {
int nb_bits = nb_symbols * qam->k;
double best_ber = INFINITY;
double best_angle = 0.0;
uint8_t* temp_bits = (uint8_t*)malloc(nb_bits * sizeof(uint8_t));
for (int r = 0; r < 4; r++) {
double angle = r * M_PI/2;
double complex* rotated = (double complex*)malloc(sizeof(double complex) * nb_symbols * qam->N);
for (int i = 0; i < nb_symbols * qam->N; i++) {
rotated[i] = r_corr[i] * cexp(I * angle);
}
demodulate(qam, rotated, nb_symbols, temp_bits, fp_constel);
double ber = compare_bits(input_bits, temp_bits, nb_bits);
if (ber < best_ber) {
best_ber = ber;
best_angle = angle;
}
free(rotated);
void add_dephasage(double complex* s, double phi_offset, int total_samples) {
for (int i = 0; i < total_samples; i++) {
s[i] *= cexp(I * phi_offset);
}
for (int i = 0; i < nb_symbols * qam->N; i++) {
r_corr[i] *= cexp(I * best_angle);
}
demodulate(qam, r_corr, nb_symbols, output_bits, fp_constel);
free(temp_bits);
}
void add_freq(qam_system* qam, double complex* s, double freq_offset, int total_samples) {
for (int i = 0; i < total_samples; i++) {
double t = (double)i / qam->Fs;
s[i] *= cexp(I * 2 * M_PI * freq_offset * t);
}
}
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]));
}
}
}
void reconstruction_text(int nb_chars, uint8_t* output_bits, char* texte_recup) {
for(int i = 0; i < nb_chars; i++){
char c = 0;
for(int b = 0; b < 8; b++){
c |= output_bits[i*8 + b] << (7-b);
}
texte_recup[i] = c;
}
texte_recup[nb_chars] = '\0';
}
void conversion_text_to_bits(int nb_chars, int nb_bits, char* texte, uint8_t* input_bits) {
for(int i = 0; i < nb_chars; i++){
for(int b = 0; b < 8; b++){
input_bits[i*8 + b] = (texte[i] >> (7-b)) & 1;
}
}
}
// Libération de la mémoire
void free_constellation(qam_system* qam) {
int sm = (int)sqrt(qam->M);
for (int i = 0; i < sm; i++)
free(qam->constellation[i]);
free(qam->constellation);
}
int main () {
qam_system qam;
qam.M = 16;
qam.k = (int)log2((double)(qam.M));
qam.Fs = 44100;
//qam.Ts = 0.0003;
//qam.N = (int)qam.Fs * qam.Ts;
qam.Ts = 0.01;
qam.N = (int)(qam.Fs * qam.Ts);
qam.Fc = 2000;
init_constellation(&qam);
//int nb_bits = 1000;
//int nb_symbols = nb_bits / qam.k;
//uint8_t* input_bits = malloc(nb_bits * sizeof(uint8_t));
//for (int i = 0; i < nb_bits; i++) {
// input_bits[i] = rand() % 2;
//}
char* texte = "Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux";
// Conversion du texte en bits
char* texte = "Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux, Vif juge, trempez ce blond whisky aqueux";
int nb_chars = strlen(texte);
int nb_bits = nb_chars * 8;
int nb_symbols = (nb_bits + qam.k - 1) / qam.k;
// Conversion du texte en bits
uint8_t* input_bits = malloc(nb_bits * sizeof(uint8_t));
for(int i = 0; i < nb_chars; i++){
for(int b = 0; b < 8; b++){
input_bits[i*8 + b] = (texte[i] >> (7-b)) & 1;
}
}
conversion_text_to_bits(nb_chars, nb_bits, texte, input_bits);
// Conversion en symboles
double complex* symbols = malloc(sizeof(double complex) * nb_symbols);
@ -268,65 +210,28 @@ int main () {
modulate(&qam, symbols, nb_symbols, s);
// Ajout du bruit
double signal_power = (2.0/3.0)*(qam.M-1); // puissance moyenne
double snr_dB = 5; // SNR en dB
double snr_lin = pow(10.0, snr_dB / 10.0);
double sigma = sqrt(signal_power / snr_lin);
add_noise(s, total_samples, 10);
add_noise(s, total_samples, 0);
FILE *fp_ref = fopen("constellation_ref.dat", "w");
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]));
}
}
fill_constellation_data(&qam, fp_ref);
fclose(fp_ref);
FILE *fp_constel = fopen("constellation.dat", "w");
// Ajout de dephasage
//double phase_offset = M_PI / 6.0; // 30 degrés
//for (int i = 0; i < total_samples; i++) {
// s[i] *= cexp(I * phase_offset);
//}
//add_dephasage(s, M_PI / 6.0, total_samples);
// AJout de decalage de fréquence
double freq_offset = 1; // Hz de décalage
for (int i = 0; i < total_samples; i++) {
double t = (double)i / qam.Fs;
s[i] *= cexp(I * 2 * M_PI * freq_offset * t);
}
// Ajout de decalage entre les symbole
//int offset_samples = (int)(0.3 * qam.N); // décalage de 30% d’un symbole
//memmove(s + offset_samples, s, (total_samples - offset_samples) * sizeof(double complex));
double complex* r_corr = malloc(sizeof(double complex) * total_samples);
double Kp = 0.2;
double Ki = 0.02;
double alpha = 0.1;
FILE* fp_error = fopen("pll_error.dat", "w");
pll_qam_symbol(&qam, s, r_corr, nb_symbols, Kp, Ki, alpha, fp_error);
fclose(fp_error);
//add_freq(&qam, s, 1, total_samples);
// Démodulation
FILE *fp_constel = fopen("constellation.dat", "w");
uint8_t* output_bits = (uint8_t*)malloc(nb_bits * sizeof(uint8_t));
demodulate2(&qam, r_corr, nb_symbols, input_bits, output_bits, fp_constel);
//demodulate(&qam, r_corr, nb_symbols, output_bits, fp_constel);
demodulate(&qam, s, nb_symbols, output_bits, fp_constel);
fclose(fp_constel);
// Reconstruction du texte
char* texte_recup = malloc(nb_chars + 1);
for(int i = 0; i < nb_chars; i++){
char c = 0;
for(int b = 0; b < 8; b++){
c |= output_bits[i*8 + b] << (7-b);
}
texte_recup[i] = c;
}
texte_recup[nb_chars] = '\0';
reconstruction_text(nb_chars, output_bits, texte_recup);
printf("Texte original : %s\n\n", texte);
printf("Texte demodulé : %s\n", texte_recup);
@ -338,7 +243,6 @@ int main () {
free(input_bits);
free(output_bits);
free(symbols);
free(r_corr);
free(s);
free_constellation(&qam);