DSP/QAM/qam.c

#include <math.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <complex.h>
#include "../WAV/wav.h"
#include "../files/files.h"
#include <string.h>

#define A 10000

struct qam_system_s {
    int M; // Nombre de symboles M-QAM
    int k; // Nombre de bits/symboles
    double Fs; // Fréquence d'échantillionage
    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
};
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);
    }

    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;
        for (int j = 0; j < sm; j++) {
            double complex qp = -(sm - 1) + 2 * j;
            qam->constellation[i][j] = A * (ip + I * qp) / norm_factor; 
        }
    }
}

// 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++) {
        double complex iq = symbols[k];
        for (int n = 0; n < qam->N; n++) {
            s[k * qam->N + n] = iq * cexp(2 * I * M_PI * qam->Fc * ((double)n / qam->Fs)); 
        }
    }
}

// Demodulation qam
void demodulate(qam_system* qam, double complex* s, int nb_symbols, uint8_t* bits_hat, double sigma) {
    for (int k = 0; k < nb_symbols; k++) {
        double complex r = 0;
        for (int n = 0; n < qam->N; n++) {
            r += s[k * qam->N + n] * cexp(-2 * I * M_PI * qam->Fc * ((double)n / qam->Fs));
        }
        r /= qam->N;

        // Distance euclidien de Ir et Qr pour avoir le point le plus proche de la constellation
        
        int sm = (int)sqrt(qam->M);
        /* TEMPS INFINI
        double min_d = INFINITY;
        int i_cl, 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;
                }
            }
        }
        */
        double norm_factor = sqrt((double)(qam->M - 1) / 3.0);
        double Ir = creal(r) * norm_factor / A;
        double Qr = cimag(r) * norm_factor / A;

        int i = (int)round((Ir + (sm - 1)) / 2.0);
        int j = (int)round((Qr + (sm - 1)) / 2.0);

        i = (i < 0) ? 0 : ((i >= sm) ? sm - 1 : i);
        j = (j < 0) ? 0 : ((j >= sm) ? sm - 1 : j);

        int id = i * sm + j;

        //int id = i_cl * sm + j_cl;
        for (int b = 0; b < qam->k; b++) {
            bits_hat[k * qam->k + (qam->k - 1 - b)] = (id >> 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 (int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Utilisation: %s <fichier_entree>\n", argv[0]);
        return 1;
    }

    qam_system qam;
    qam.M = 256;
    qam.k = (int)log2((double)(qam.M));
    qam.Fs = 44100;
    qam.Ts = 0.00003;
    qam.N = (int)qam.Fs * qam.Ts;
    qam.Fc = 2000;
    init_constellation(&qam);

    // Nombre de bit multiple de k sinon remplir de zero jusqu'a ce que ce le soit
    //int bits[16] = {1,0,1,1,  0,1,1,0,  1,1,0,0,  0,0,0,1};
    //int nb_bits = 16;
    //int nb_symbols = 16 / qam.k;

    printf("Lecture du fichier\n");
    // Lecture du fichier et conversion en bits
    const char *input_filename = argv[1];
    bit_array input_bits = file_to_bits(input_filename);
    size_t nb_symbols = input_bits.nb_bits / qam.k;

    printf("Mise en forme des symboles\n");
    // Mise en forme des symboles
    double complex *symbols = malloc(sizeof(double complex) * nb_symbols);
    bits_to_symbols(&qam, input_bits.bits, input_bits.nb_bits, symbols);

    printf("Modulation\n");
    // Modulation QAM 
    int total_samples = qam.N * nb_symbols;
    double complex* s = (double complex*)malloc(sizeof(double complex) * total_samples);
    modulate(&qam, symbols, nb_symbols, s);

    printf("Demodulation\n");

    // Demodulation QAM
    bit_array output_bits;
    output_bits.nb_bits = input_bits.nb_bits;
    output_bits.bits = (uint8_t*)malloc(output_bits.nb_bits);
    demodulate(&qam, s, nb_symbols, output_bits.bits, 0.0);

    printf("Ecriture...\n");
    // Ecriture du fichier de Demodulation
    char *output_filename = make_output_filename(input_filename);
    bits_to_file(output_filename, &output_bits);


    // Affichage du signal dans un .wav
    double* si = (double*)malloc(sizeof(double) * total_samples);
    for (int i = 0; i < total_samples; i++) {
       si[i] = cimag(s[i]); 
    }
    write_wav("s.wav", si, total_samples);

    // Libération mémoire
    free_bit_array(&input_bits);
    free_bit_array(&output_bits);
    free(symbols);
    free(s);
    free_constellation(&qam);
    free(output_filename);

    return 0;
}