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JakesFadingGenerator.cpp

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 * A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
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#include <RISE/scenario/ftfading/JakesFadingGenerator.hpp>
#include <WNS/module/Base.hpp>
#include <WNS/distribution/Uniform.hpp>
#include <WNS/rng/RNGen.hpp>

using namespace rise;
using namespace rise::scenario;
using namespace rise::scenario::ftfading;

JakesFadingGenerator::JakesFadingGenerator()
{
}

JakesFadingGenerator::~JakesFadingGenerator()
{}

void
JakesFadingGenerator::initJakes(const double _maximumDopplerFrequency, const double _samplingTime, const unsigned int _numberOfWaves)
{
    currentSampleIndex = 0;

    //maximumDopplerFrequency = _maximumDopplerFrequency;
    samplingTime  = _samplingTime;
    //numberOfWaves = _numberOfWaves;
    numberOfWavesQuarter = _numberOfWaves/4;

    wns::distribution::Uniform randomAngle = 
        wns::distribution::Uniform(0.0, 2.0 * M_PI); // between 0..2pi

    double scaleFactor = 2.0/std::sqrt(static_cast<double>(numberOfWavesQuarter));

    complexTurningFactorVector.resize(numberOfWavesQuarter, 0.0);
    for (unsigned int i=0; i<numberOfWavesQuarter; ++i)
        complexTurningFactorVector[i] = std::polar<double>(1,randomAngle() ) * scaleFactor;

    omega.resize(numberOfWavesQuarter, 0.0);
    for (unsigned int i=0; i<numberOfWavesQuarter; ++i)
        omega[i] = 2.0*M_PI*_maximumDopplerFrequency * samplingTime * std::cos(static_cast<double>((2.0*M_PI*(i+0.5) + randomAngle()) / _numberOfWaves));

    thetaInitial = randomAngle(); // from random number generator
}

// TODO?? std::complex<double> JakesFadingGenerator::getComplexFadingValue(unsigned int sample)

std::complex<double>
JakesFadingGenerator::getNextComplexFadingValue()
{
    std::complex<double> complexSum = 0.0;
    for (unsigned int i=0; i<numberOfWavesQuarter; ++i)
        complexSum += complexTurningFactorVector[i] * std::cos(omega[i]*currentSampleIndex/*now*/ + thetaInitial);
    ++currentSampleIndex; // advance timestep
    return complexSum; // * scaleFactor is now already included in complexTurningFactorVector[i]
}

wns::Ratio
JakesFadingGenerator::getNextFadingRatio()
{
    return wns::Ratio::from_factor(std::abs(getNextComplexFadingValue()));
}

double
JakesFadingGenerator::getNextFadingValue()
{
    return std::abs(getNextComplexFadingValue());
}

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