#include "propagation-loss-model.h"

#include <math.h>

namespace ns3 {

const double FriisPropagationLossModel::PI = 3.1415;

PropagationLossModel::~PropagationLossModel ()

{}

FriisPropagationLossModel::FriisPropagationLossModel ()

  : m_lambda (),

    m_systemLoss (1.0)

{}

void 

FriisPropagationLossModel::SetSystemLoss (double systemLoss)

{

  m_systemLoss = systemLoss;

}

double 

FriisPropagationLossModel::GetSystemLoss (void) const

{

  return m_systemLoss;

}

void 

FriisPropagationLossModel::SetLambda (double frequency, double speed)

{

  m_lambda = speed / frequency;

}

void 

FriisPropagationLossModel::SetLambda (double lambda)

{

  m_lambda = lambda;

}

double 

FriisPropagationLossModel::GetLambda (void) const

{

  return m_lambda;

}

double 

FriisPropagationLossModel::DbmToW (double dbm) const

{

  double mw = pow(10.0,dbm/10.0);

  return mw / 1000.0;

}

double

FriisPropagationLossModel::DbmFromW (double w) const

{

  double dbm = log10 (w * 1000.0) * 10.0;

  return dbm;

}

double 

FriisPropagationLossModel::GetRxPower (double txPowerDbm,

				       double distance) const

{

  /*

   * Friis free space equation:

   * where Pt, Gr, Gr and P are in Watt units

   * L is in meter units.

   *

   *       Pt * Gt * Gr * (lambda^2)

   *   P = --------------------------

   *       (4 * pi * d)^2 * L

   *

   * Gt: tx gain (W)

   * Gr: rx gain (W)

   * Pt: tx power (W)

   * d: distance (m)

   * L: system loss

   * lambda: wavelength (m)

   *

   * Here, we ignore tx and rx gain.

   */

  double numerator = DbmToW (txPowerDbm) * m_lambda * m_lambda;

  double denominator = 16 * PI * PI * distance * distance * m_systemLoss;

  double pr = numerator / denominator;

  return DbmFromW (pr);

}

PathLossPropagationLossModel::PathLossPropagationLossModel ()

{}

void 

PathLossPropagationLossModel::SetPathLossExponent (double n)

{

  m_exponent = n;

}

double 

PathLossPropagationLossModel::GetPathLossExponent (void) const

{

  return m_exponent;

}

double

PathLossPropagationLossModel::DbToW (double db) const

{

  return pow(10.0,db/10.0);

}

double 

PathLossPropagationLossModel::GetRxPower (double txPowerDbm,

					  double distance) const

{

  if (distance <= 1.0)

    {

      return txPowerDbm;

    }

  double prd0 = m_reference->GetRxPower (txPowerDbm, 1.0);

  double pr = 10*log10(prd0) - m_exponent * 10.0 * log10(distance);

  return DbToW (pr);

}

} // namespace ns3