path_loss.cpp

#include "path_loss.hpp"
#include "utility.hpp"
#include "wireless_comm_signal.hpp"
#include "physical_layer.hpp"

const double FreeSpace::m_DEFAULT_LOSS_FACTOR = 1.0;
const double TwoRay::m_DEFAULT_ANTENNA_HEIGHT = 1.5;

PathLoss::PathLoss()
{

}

PathLoss::~PathLoss()
{

}

FreeSpace::FreeSpace()
   : m_lossFactor(m_DEFAULT_LOSS_FACTOR)
{
   assert(m_lossFactor >= 1.0);
}

FreeSpace::FreeSpace(double lossFactor)
   : m_lossFactor(lossFactor)
{
   if(m_lossFactor < 1.0)
      m_lossFactor = m_DEFAULT_LOSS_FACTOR;
   assert(m_lossFactor >= 1.0);
}

TwoRay::TwoRay()
   : FreeSpace(), m_antennaHeight(m_DEFAULT_ANTENNA_HEIGHT)
{

}

TwoRay::TwoRay(double lossFactor)
   : FreeSpace(lossFactor), m_antennaHeight(m_DEFAULT_ANTENNA_HEIGHT)
{

}

double FreeSpace::getRecvdStrength(const WirelessCommSignal& signal,
   const PhysicalLayer& receiver) const
{
   double numerator = decibelsToPower(signal.getDbStrength()) * 
      signal.getTransmitterGain() * receiver.getGain() * 
      pow(signal.getWavelength(), 2);
   double distance = Location::distance(
      signal.getLocation(), receiver.getLocation());
   double denominator = pow((4.0 * PI), 2) * 
      pow(distance, 2) * m_lossFactor;

   assert(denominator > 0.0);

   return (numerator / denominator);
}

double TwoRay::getRecvdStrength(const WirelessCommSignal& signal,
   const PhysicalLayer& receiver) const
{

   // These equations are largely from ns-2.  If the distance
   // is less than crossoverDistance, then use the FreeSpace
   // model; otherwise use the TwoRay model.

   double crossoverDistance = (4 * PI * 
      m_antennaHeight * m_antennaHeight) / signal.getWavelength();
   double distance = Location::distance(
      signal.getLocation(), receiver.getLocation());

   double recvdStrength = FreeSpace::getRecvdStrength(signal, receiver);

   if(m_DEBUG_SIGNAL_STRENGTH) {
      ostringstream debugStream;
      debugStream << __FUNCTION__ << " crossover: " <<
         crossoverDistance << ", dist: " << distance <<
         ", FS SS: " << recvdStrength;
      LogStreamManager::instance()->logDebugItem(debugStream.str());
   }

   // If the distance is greater, use the Two Ray equation.
   if(distance > crossoverDistance) {
      double numerator = decibelsToPower(signal.getDbStrength()) *
         signal.getTransmitterGain() * receiver.getGain() *
         pow(m_antennaHeight, 2) * pow(m_antennaHeight, 2);
      double denominator = pow(distance, 4) * m_lossFactor;
      assert(denominator > 0.0);
      recvdStrength = numerator / denominator;
   }
   
   return recvdStrength;
}

---