将以下matlab语句改写为c++ s = awgn(x,6)

在 C++ 中，可以使用以下语句来模拟 MATLAB 中的 awgn 函数：

#include <random> // for normal_distribution
#include <cmath> // for sqrt

// Define a function to add white Gaussian noise to a signal x with specified signal-to-noise ratio (SNR)
std::vector<double> add_awgn_noise(const std::vector<double>& x, double snr_db) {
    std::default_random_engine generator;
    std::normal_distribution<double> distribution(0.0, 1.0); // mean = 0, standard deviation = 1

    // Calculate the noise power
    double snr = pow(10, snr_db / 10.0);
    double signal_power = 0.0;
    double noise_power = 0.0;
    for (size_t i = 0; i < x.size(); i++) {
        signal_power += x[i] * x[i];
        double noise = distribution(generator);
        noise_power += noise * noise;
    }
    noise_power /= x.size();
    double target_noise_power = signal_power / snr;
    double scale_factor = sqrt(target_noise_power / noise_power);

    // Add the noise to the signal
    std::vector<double> y(x.size());
    for (size_t i = 0; i < x.size(); i++) {
        double noise = scale_factor * distribution(generator);
        y[i] = x[i] + noise;
    }

    return y;
}

下面是如何使用上述函数模拟 MATLAB 中的 `awgn(x,6)`：

std::vector<double> x = { 1.0, 2.0, 3.0, 4.0, 5.0 };
std::vector<double> y = add_awgn_noise(x, 6.0);