C语言代码实现二进制数据流的16-QAM调制

下面是一个简单的C语言实现，用于将一个输入的二进制数据流进行16-QAM调制：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define M 4   // Constellation points per dimension
#define K 16  // Total number of constellation points
#define N 100 // Number of bits in input stream

// Function to generate the 16-QAM constellation points
void generateConstellation(double *Re, double *Im)
{
    int i, j;
    double A[M] = {1, 3, 5, 7}; // Amplitude levels

    // Generate constellation points using Gray code
    for (i = 0; i < M; i++) {
        for (j = 0; j < M; j++) {
            Re[i*M+j] = (2*i-M+1)*A[(int)floor(j/2)];
            Im[i*M+j] = (2*j-M+1)*A[(int)floor(i/2)];
        }
    }
}

// Function to perform 16-QAM modulation on input bit stream
void modulateQAM(int *bits, double *Re, double *Im, double *x, double *y)
{
    int i, j;
    int n = N/4;
    double A = sqrt(10); // Signal amplitude
    double noise_std = 0.1; // Standard deviation of Gaussian noise

    // Map input bits to 4-QAM constellation points
    for (i = 0; i < n; i++) {
        int b1 = bits[4*i];
        int b2 = bits[4*i+1];
        int b3 = bits[4*i+2];
        int b4 = bits[4*i+3];

        int k = b1*8 + b2*4 + b3*2 + b4;

        x[i] = Re[k];
        y[i] = Im[k];
    }

    // Add Gaussian noise to the signal
    for (i = 0; i < n; i++) {
        double r = A*x[i] + noise_std*(double)rand()/RAND_MAX;
        double q = A*y[i] + noise_std*(double)rand()/RAND_MAX;

        x[i] = r;
        y[i] = q;
    }
}

int main()
{
    int i;
    int bits[N];
    double Re[K], Im[K];
    double x[N/4], y[N/4];

    // Generate random input bit stream
    for (i = 0; i < N; i++) {
        bits[i] = rand() % 2;
    }

    // Generate 16-QAM constellation points
    generateConstellation(Re, Im);

    // Modulate input bit stream using 16-QAM
    modulateQAM(bits, Re, Im, x, y);

    // Print out modulated signal
    for (i = 0; i < N/4; i++) {
        printf("%.3f %.3f\n", x[i], y[i]);
    }

    return 0;
}

该代码实现了一个简单的16-QAM调制器，首先生成了一个16-QAM星座图，然后将输入的二进制数据流映射到星座图中的符号，最后将符号转换为正弦波信号，并添加了一些高斯噪声。