238 lines
7.6 KiB
C
238 lines
7.6 KiB
C
#include <math.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <complex.h>
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#include "../wav/wav.h"
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#include "../files/files.h"
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#include "../plot/plot_constellation.h"
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#include <string.h>
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#include <SDL2/SDL.h>
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#define A 1
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struct qam_system_s {
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int M; // Nombre de symboles M-QAM
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int k; // Nombre de bits/symboles
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double Fs; // Fréquence d'échantillionage
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double Ts; // Temps d'échantillionage
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int N; // Nombre d'échantillions
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double Fc; // Fréquence de la porteuse
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double complex** constellation; // Tableau de symboles I + j Q
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};
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typedef struct qam_system_s qam_system;
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// Initialisation de la constellation (double tableau de taille sqrt(M)),
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// ToDo : changer à un tableau à 1 dimension pour éviter de calculer sqrt(M)
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void init_constellation (qam_system* qam) {
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int sm = (int)sqrt(qam->M);
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qam->constellation = (double complex**)malloc(sizeof(double complex*) * sm);
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for (int i = 0; i < sm; i++) {
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qam->constellation[i] = (double complex*)malloc(sizeof(double complex) * sm);
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}
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double norm_factor = sqrt((double)(qam->M - 1) / 3.0); // Pour puissance unitaire
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for (int i = 0; i < sm; i++) {
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double complex ip = -(sm - 1) + 2 * i;
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for (int j = 0; j < sm; j++) {
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double complex qp = -(sm - 1) + 2 * j;
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qam->constellation[i][j] = (ip + I * qp);
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}
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}
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}
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// Calcul du bruit gaussien pour un sigma donné
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// Formule de Box-Muller
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double gaussian_noise (double sigma) {
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double u1 = (rand() + 1) / ((double)RAND_MAX + 2);
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double u2 = (rand() + 1) / ((double)RAND_MAX + 2);
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return sigma * sqrt(-2 * log(u1)) * cos(2 * M_PI * u2);
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}
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// Ajout du bruit
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void add_noise (double complex* s, int len, double sigma) {
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for (int i = 0; i < len; i++) {
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double nr = gaussian_noise(sigma);
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double ni = gaussian_noise(sigma);
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s[i] += nr + I * ni;
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}
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}
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// Changer le tableau de bits en boolen ou alors la represenation binaire et shifter pour extraire les bits (pas bien si M plus grand)
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void bits_to_symbols (qam_system* qam, uint8_t* bits, int nb_bits, double complex* symbols) {
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int nb_symbols = nb_bits / qam->k;
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int sm = sqrt(qam->M);
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for (int k = 0; k < nb_symbols; k++) {
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int id = 0;
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for (int b = 0 ; b < qam->k; b++) {
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id = id * 2 + bits[k * qam->k + b];
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}
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int i = id / sm;
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int j = id % sm;
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symbols[k] = qam->constellation[i][j];
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}
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}
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// Modulation QAM
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void modulate (qam_system* qam, double complex* symbols, int nb_symbols, double complex* s) {
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for (int k = 0; k < nb_symbols; k++) {
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double complex iq = symbols[k];
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for (int n = 0; n < qam->N; n++) {
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s[k * qam->N + n] = iq * cexp(2 * I * M_PI * qam->Fc * ((double)n / qam->Fs));
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}
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}
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}
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// Demodulation QAM
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void demodulate(qam_system* qam, double complex* s, int nb_symbols, uint8_t* bits_hat) {
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for (int k = 0; k < nb_symbols; k++) {
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double complex r = 0;
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for (int n = 0; n < qam->N; n++) {
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r += s[k * qam->N + n] * cexp(-2 * I * M_PI * qam->Fc * ((double)n / qam->Fs));
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}
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r /= qam->N;
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// Distance euclidien de Ir et Qr pour avoir le point le plus proche de la constellation
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int sm = (int)sqrt(qam->M);
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double min_d = INFINITY;
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int i_cl, j_cl = 0;
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for (int i = 0; i < sm; i++) {
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for (int j = 0; j < sm; j++) {
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double d = cabs(r - qam->constellation[i][j]);
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if (d < min_d) {
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min_d = d;
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i_cl = i;
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j_cl = j;
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}
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}
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}
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/*
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double norm_factor = sqrt((double)(qam->M - 1) / 3.0);
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double Ir = creal(r) * norm_factor / A;
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double Qr = cimag(r) * norm_factor / A;
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int i = (int)round((Ir + (sm - 1)) / 2.0);
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int j = (int)round((Qr + (sm - 1)) / 2.0);
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i = (i < 0) ? 0 : ((i >= sm) ? sm - 1 : i);
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j = (j < 0) ? 0 : ((j >= sm) ? sm - 1 : j);
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int id = i * sm + j;
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*/
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int id = i_cl * sm + j_cl;
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for (int b = 0; b < qam->k; b++) {
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bits_hat[k * qam->k + (qam->k - 1 - b)] = (id >> b) & 1;
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}
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}
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}
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double complex* demodulate_points(qam_system* qam, double complex* s, int nb_symbols) {
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double complex* points = malloc(sizeof(double complex) * nb_symbols);
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for (int k = 0; k < nb_symbols; k++) {
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double complex r = 0;
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for (int n = 0; n < qam->N; n++) {
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r += s[k * qam->N + n] * cexp(-2 * I * M_PI * qam->Fc * ((double)n / qam->Fs));
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}
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r /= qam->N;
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double norm_factor = sqrt((double)(qam->M - 1) / 3.0);
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double Ir = creal(r);
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double Qr = cimag(r);
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points[k] = Ir + I * Qr;
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}
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return points;
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}
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// Libération de la mémoire
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void free_constellation(qam_system* qam) {
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int sm = (int)sqrt(qam->M);
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for (int i = 0; i < sm; i++)
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free(qam->constellation[i]);
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free(qam->constellation);
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}
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int main (int argc, char *argv[]) {
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if (argc < 2) {
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fprintf(stderr, "Utilisation: %s <fichier_entree>\n", argv[0]);
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return 1;
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}
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qam_system qam;
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qam.M = 16;
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qam.k = (int)log2((double)(qam.M));
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qam.Fs = 44100;
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qam.Ts = 0.0003;
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qam.N = (int)qam.Fs * qam.Ts;
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qam.Fc = 2000;
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init_constellation(&qam);
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printf("Lecture du fichier...\n");
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// Lecture du fichier et conversion en bits
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const char *input_filename = argv[1];
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bit_array input_bits = file_to_bits(input_filename);
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size_t nb_symbols = input_bits.nb_bits / qam.k;
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printf("Mise en forme des symboles...\n");
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// Mise en forme des symboles
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double complex *symbols = malloc(sizeof(double complex) * nb_symbols);
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bits_to_symbols(&qam, input_bits.bits, input_bits.nb_bits, symbols);
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printf("Modulation...\n");
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// Modulation QAM
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int total_samples = qam.N * nb_symbols;
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double complex* s = (double complex*)malloc(sizeof(double complex) * total_samples);
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modulate(&qam, symbols, nb_symbols, s);
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// Ajout du bruit
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double signal_power = (2.0/3.0)*(qam.M-1); // puissance moyenne avant échelle
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double snr_dB = 10; // Signal to noise ratio
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double snr_lin = pow(10.0, snr_dB / 10.0);
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double sigma = sqrt(signal_power / snr_lin);
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printf("Ajout du bruit... \n puissance du signal : %f\n SNR db : %f\n sigma : %f\n", signal_power, snr_dB, sigma);
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add_noise(s, total_samples, sigma);
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printf("Demodulation...\n");
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// Demodulation QAM
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bit_array output_bits;
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output_bits.nb_bits = input_bits.nb_bits;
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output_bits.bits = (uint8_t*)malloc(output_bits.nb_bits);
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demodulate(&qam, s, nb_symbols, output_bits.bits);
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printf("Ecriture...\n");
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// Ecriture du fichier de Demodulation
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char *output_filename = make_output_filename(input_filename);
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bits_to_file(output_filename, &output_bits);
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// Affichage du signal dans un .wav
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double* si = (double*)malloc(sizeof(double) * total_samples);
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for (int i = 0; i < total_samples; i++) {
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si[i] = cimag(s[i]);
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}
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write_wav("output.wav", si, total_samples);
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// Plot
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printf("Ploting...");
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plot_t plot;
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plot_init(&plot, 1400, 1400, 0.04);
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plot_draw_constellation(&plot, qam.constellation, qam.M);
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SDL_Color red = {255, 0, 0, 255};
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plot_draw_points_animated(&plot, demodulate_points(&qam, s, nb_symbols), nb_symbols, red, 5);
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// Libération mémoire
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plot_close(&plot);
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free_bit_array(&input_bits);
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free_bit_array(&output_bits);
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free(symbols);
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free(s);
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free_constellation(&qam);
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free(output_filename);
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return 0;
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}
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