satellite-mobility-observer.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2014 Magister Solutions Ltd
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Sami Rantanen <sami.rantanen@magister.fi>
 */
 
#include "satellite-mobility-observer.h"
 
#include "satellite-utils.h"
 
#include "ns3/boolean.h"
#include "ns3/double.h"
#include "ns3/log.h"
#include "ns3/pointer.h"
#include "ns3/trace-source-accessor.h"
 
#include <cmath>
#include <stdint.h>
#include <string>
 
NS_LOG_COMPONENT_DEFINE("SatMobilityObserver");
 
namespace ns3
{
 
NS_OBJECT_ENSURE_REGISTERED(SatMobilityObserver);
 
TypeId
SatMobilityObserver::GetTypeId(void)
{
    static TypeId tid =
        TypeId("ns3::SatMobilityObserver")
            .SetParent<Object>()
            .AddAttribute("OwnMobility",
                          "Own mobility.",
                          PointerValue(),
                          MakePointerAccessor(&SatMobilityObserver::m_ownMobility),
                          MakePointerChecker<SatMobilityModel>())
            .AddAttribute("SatelliteMobility",
                          "The mobility of the satellite.",
                          PointerValue(),
                          MakePointerAccessor(&SatMobilityObserver::m_geoSatMobility),
                          MakePointerChecker<SatMobilityModel>())
            .AddAttribute("AnotherMobility",
                          "The mobility of the another end node.",
                          PointerValue(),
                          MakePointerAccessor(&SatMobilityObserver::m_anotherMobility),
                          MakePointerChecker<SatMobilityModel>())
            .AddAttribute("OwnPropagation",
                          "Own propagation delay model.",
                          PointerValue(),
                          MakePointerAccessor(&SatMobilityObserver::m_ownProgDelayModel),
                          MakePointerChecker<SatMobilityModel>())
            .AddAttribute("AnotherPropagation",
                          "The propagation delay model of the another end node.",
                          PointerValue(),
                          MakePointerAccessor(&SatMobilityObserver::m_anotherProgDelayModel),
                          MakePointerChecker<SatMobilityModel>())
            .AddAttribute("MinAltitude",
                          "The minimum altitude accepted for own position.",
                          DoubleValue(0),
                          MakeDoubleAccessor(&SatMobilityObserver::m_minAltitude),
                          MakeDoubleChecker<double>())
            .AddAttribute("MaxAltitude",
                          "The maximum altitude accepted for own position.",
                          DoubleValue(500.00),
                          MakeDoubleAccessor(&SatMobilityObserver::m_maxAltitude),
                          MakeDoubleChecker<double>())
            .AddTraceSource("PropertyChanged",
                            "The value of the some property has changed",
                            MakeTraceSourceAccessor(&SatMobilityObserver::m_propertyChangeTrace),
                            "ns3::SatMobilityObserver::PropertyChangedCallback");
    return tid;
}
 
SatMobilityObserver::SatMobilityObserver()
{
    NS_LOG_FUNCTION(this);
 
    // this constructor version should not be used
    NS_ASSERT(false);
}
 
SatMobilityObserver::SatMobilityObserver(Ptr<SatMobilityModel> ownMobility,
                                         Ptr<SatMobilityModel> geoSatMobility,
                                         bool isRegenerative)
    : m_ownMobility(ownMobility),
      m_anotherMobility(nullptr),
      m_geoSatMobility(geoSatMobility),
      m_ownProgDelayModel(nullptr),
      m_anotherProgDelayModel(nullptr),
      m_initialized(false),
      m_isRegenerative(isRegenerative)
{
    NS_LOG_FUNCTION(this << ownMobility << geoSatMobility);
 
    GeoCoordinate satellitePosition = m_geoSatMobility->GetGeoPosition();
    GeoCoordinate ownPosition = m_ownMobility->GetGeoPosition();
 
    // same reference ellipsoide must be used by mobilities
    NS_ASSERT(satellitePosition.GetRefEllipsoid() == ownPosition.GetRefEllipsoid());
 
    double satelliteAltitude = satellitePosition.GetAltitude();
 
    // satellite is expected to be in the sky
    NS_ASSERT(satelliteAltitude > 0.0);
 
    // calculate radius of the earth using satellite information
    m_earthRadius =
        CalculateDistance(satellitePosition.ToVector(), Vector(0, 0, 0)) - satelliteAltitude;
 
    SatelliteStatusChanged();
    m_updateElevationAngle = true;
    m_updateTimingAdvance = true;
    m_timingAdvance_s = Seconds(0);
 
    m_geoSatMobility->TraceConnect("SatCourseChange",
                                   "Satellite",
                                   MakeCallback(&SatMobilityObserver::PositionChanged, this));
    m_ownMobility->TraceConnect("SatCourseChange",
                                "Own",
                                MakeCallback(&SatMobilityObserver::PositionChanged, this));
 
    m_velocity = 0.0;
 
    m_initialized = true;
}
 
void
SatMobilityObserver::DoDispose()
{
    NS_LOG_FUNCTION(this);
 
    m_ownMobility = nullptr;
    m_anotherMobility = nullptr;
    m_geoSatMobility = nullptr;
    m_ownProgDelayModel = nullptr;
    m_anotherProgDelayModel = nullptr;
}
 
SatMobilityObserver::~SatMobilityObserver()
{
    NS_LOG_FUNCTION(this);
}
 
void
SatMobilityObserver::ObserveTimingAdvance(Ptr<PropagationDelayModel> ownDelayModel,
                                          Ptr<PropagationDelayModel> anotherDelayModel,
                                          Ptr<SatMobilityModel> anotherMobility)
{
    NS_LOG_FUNCTION(this << ownDelayModel << anotherDelayModel << anotherMobility);
 
    NS_ASSERT(ownDelayModel != nullptr);
    NS_ASSERT(anotherDelayModel != nullptr);
    NS_ASSERT(anotherMobility != nullptr);
 
    auto cb = MakeCallback(&SatMobilityObserver::PositionChanged, this);
    if (m_anotherMobility != nullptr)
    {
        m_anotherMobility->TraceDisconnect("SatCourseChange", "Another", cb);
    }
 
    m_ownProgDelayModel = ownDelayModel;
    m_anotherProgDelayModel = anotherDelayModel;
    m_anotherMobility = anotherMobility;
 
    // same reference ellipsoide must be used by mobilities
    NS_ASSERT(m_anotherMobility->GetGeoPosition().GetRefEllipsoid() ==
              m_ownMobility->GetGeoPosition().GetRefEllipsoid());
 
    m_anotherMobility->TraceConnect("SatCourseChange", "Another", cb);
}
 
double
SatMobilityObserver::GetElevationAngle(void)
{
    NS_LOG_FUNCTION(this);
 
    if (m_updateElevationAngle == true)
    {
        // same reference ellipsoide must be used by mobilities
        NS_ASSERT(m_geoSatMobility->GetGeoPosition().GetRefEllipsoid() ==
                  m_ownMobility->GetGeoPosition().GetRefEllipsoid());
 
        UpdateElevationAngle();
        m_updateElevationAngle = false;
    }
 
    return m_elevationAngle;
}
 
double
SatMobilityObserver::GetVelocity(void)
{
    NS_LOG_FUNCTION(this);
 
    Vector velocity = m_ownMobility->GetVelocity();
    m_velocity = std::sqrt((velocity.x * velocity.x) + (velocity.y * velocity.y) +
                           (velocity.z * velocity.z));
 
    return m_velocity;
}
 
Time
SatMobilityObserver::GetTimingAdvance(void)
{
    NS_LOG_FUNCTION(this);
 
    // update timing advance, if another end is given and update needed
    if ((m_anotherMobility != nullptr) && (m_updateTimingAdvance == true))
    {
        // another propagation delay is expected to be given
        NS_ASSERT(m_anotherProgDelayModel != nullptr);
 
        // same reference ellipsoide must be used by mobilities
        NS_ASSERT(m_geoSatMobility->GetGeoPosition().GetRefEllipsoid() ==
                  m_ownMobility->GetGeoPosition().GetRefEllipsoid());
 
        // same reference ellipsoide must be used by mobilities
        NS_ASSERT(m_anotherMobility->GetGeoPosition().GetRefEllipsoid() ==
                  m_ownMobility->GetGeoPosition().GetRefEllipsoid());
 
        UpdateTimingAdvance();
        m_updateTimingAdvance = false;
    }
 
    return m_timingAdvance_s;
}
 
void
SatMobilityObserver::NotifyPropertyChange(void) const
{
    NS_LOG_FUNCTION(this);
 
    if (m_initialized)
    {
        m_propertyChangeTrace(this);
    }
}
 
void
SatMobilityObserver::PositionChanged(std::string context, Ptr<const SatMobilityModel> position)
{
    NS_LOG_FUNCTION(this << context << position);
 
    // set flag on to idicate that elevation angle is needed to update,
    // when its status is requested with method GetElevationAngle
    m_updateElevationAngle = true;
 
    // set flag on to idicate that timing advance is needed to update,
    // when its status is requested with method GetTimingAdvance
    m_updateTimingAdvance = true;
 
    // call satellite statis updated routine to update needed variables
    if (context == "Satellite")
    {
        SatelliteStatusChanged();
    }
 
    NotifyPropertyChange();
}
 
void
SatMobilityObserver::UpdateElevationAngle()
{
    NS_LOG_FUNCTION(this);
 
    m_elevationAngle = NAN;
 
    GeoCoordinate ownPosition = m_ownMobility->GetGeoPosition();
    GeoCoordinate satellitePosition = m_geoSatMobility->GetGeoPosition();
 
    NS_ASSERT(ownPosition.GetAltitude() >= m_minAltitude &&
              ownPosition.GetAltitude() <= m_maxAltitude);
 
    // elevation angle is always calculated at earth surface, so set altitude to zero
    ownPosition.SetAltitude(0);
 
    // calculate distance from Earth location to satellite
    double distanceToSatellite =
        CalculateDistance(ownPosition.ToVector(), satellitePosition.ToVector());
 
    // calculate elevation angle only, if satellite can be seen from own position
    if (distanceToSatellite <= m_maxDistanceToSatellite)
    {
        double earthLatitude = SatUtils::DegreesToRadians(ownPosition.GetLatitude());
        double satLatitude = SatUtils::DegreesToRadians(satellitePosition.GetLatitude());
 
        double earthLongitude = SatUtils::DegreesToRadians(ownPosition.GetLongitude());
        double satLongitude = SatUtils::DegreesToRadians(satellitePosition.GetLongitude());
 
        double longitudeDelta = satLongitude - earthLongitude;
 
        // Calculate cosini of the central angle
        // TODO: Currently we have assumed that the reference ellipsoide is a sphere.
        // This should be accurate enough for elevation angle calculation with also other
        // reference ellipsoides. But, if more accurate calculation is needed, then the used
        // reference ellipsoide is needed to be take into account.
        double centralAngleCos =
            (std::cos(earthLatitude) * std::cos(satLatitude) * std::cos(longitudeDelta)) +
            (std::sin(earthLatitude) * std::sin(satLatitude));
 
        // Calculate cosini of the elavation angle
        double elCos =
            std::sin(std::acos(centralAngleCos)) /
            std::sqrt(1 + std::pow(m_radiusRatio, 2) - 2 * m_radiusRatio * centralAngleCos);
 
        m_elevationAngle = SatUtils::RadiansToDegrees(std::acos(elCos));
    }
}
 
void
SatMobilityObserver::UpdateTimingAdvance()
{
    NS_LOG_FUNCTION(this);
 
    NS_ASSERT(m_ownProgDelayModel != nullptr);
    NS_ASSERT(m_anotherProgDelayModel != nullptr);
 
    if (m_isRegenerative)
    {
        m_timingAdvance_s = m_ownProgDelayModel->GetDelay(m_ownMobility, m_geoSatMobility);
    }
    else
    {
        m_timingAdvance_s = m_ownProgDelayModel->GetDelay(m_ownMobility, m_geoSatMobility) +
                            m_anotherProgDelayModel->GetDelay(m_anotherMobility, m_geoSatMobility);
    }
}
 
void
SatMobilityObserver::SatelliteStatusChanged()
{
    NS_LOG_FUNCTION(this);
 
    double satelliteAltitude = m_geoSatMobility->GetGeoPosition().GetAltitude();
 
    // satellite is expected to be in the sky
    NS_ASSERT(satelliteAltitude > 0.0);
 
    // calculate maximum distance where UT or GW can be on the Earth.
    double satelliteRadius = satelliteAltitude + m_earthRadius;
    m_maxDistanceToSatellite =
        std::sqrt((satelliteRadius * satelliteRadius) - (m_earthRadius * m_earthRadius));
 
    // calculate ratio of the earth and satellite radius
    m_radiusRatio = m_earthRadius / satelliteRadius;
}
 
} // namespace ns3