path_loss.cpp

RFID reader 语 tag 模拟器

 #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;
 }