Keep track of the orbital position and velocity of a satellite. More...

#include "leo-circular-orbit-mobility-model.h"

Inheritance diagram for ns3::LeoCircularOrbitMobilityModel:

Collaboration diagram for ns3::LeoCircularOrbitMobilityModel:

Public Member Functions
	LeoCircularOrbitMobilityModel ()
	constructor
	~LeoCircularOrbitMobilityModel () override
	destructor
Ptr< MobilityModel >	Copy () const override
	Copy function allows one to copy the underlying MobilityModel from a MobilityModel pointer, by calling each children Copy implementation.
Vector	DoGetGeocentricPosition () const override
	Returns the Geocentric Position of the Node in ECEF (cartesian).
double	GetAltitude () const
	Gets the altitude in m.
double	GetAltitudeKm () const
	Gets the altitude in km (not the usual meters used in ns-3).
double	GetAngularVelocity () const
	Get the orbital angular velocity.
double	GetInclination () const
	Gets the inclination.
double	GetSpeed () const
	Gets the speed of the node.
void	SetAltitude (double h)
	Sets the altitude in m.
void	SetAltitudeKm (double h)
	Sets the altitude in km (not the usual meters used in ns-3).
void	SetInclination (double incl)
	Sets the inclination.
Public Member Functions inherited from ns3::GeocentricConstantPositionMobilityModel
	GeocentricConstantPositionMobilityModel ()=default
	Create a position located at coordinates (0,0,0).
	~GeocentricConstantPositionMobilityModel () override=default
virtual Vector	GetCoordinateTranslationReferencePoint () const
	Get the reference point for coordinate conversion.
double	GetDistanceFrom (Ptr< const GeocentricConstantPositionMobilityModel > other) const
virtual double	GetElevationAngle (Ptr< const GeocentricConstantPositionMobilityModel > other)
	Computes elevation angle between a ground terminal and a HAPS/Satellite.
virtual Vector	GetGeocentricPosition () const
	Get the position using Geocentric Cartesian coordinates.
virtual Vector	GetGeographicPosition () const
	Get the position using geographic (geodetic) coordinates.
virtual Vector	GetPosition () const
virtual void	SetCoordinateTranslationReferencePoint (const Vector &refPoint)
	Set the reference point for coordinate conversion.
virtual void	SetGeocentricPosition (const Vector &position)
	Set the position using Geocentric Cartesian coordinates.
virtual void	SetGeographicPosition (const Vector &latLonAlt)
	Set the position using geographic coordinates.
virtual void	SetPosition (const Vector &position)
Public Member Functions inherited from ns3::MobilityModel
	MobilityModel ()
	~MobilityModel () override=0
int64_t	AssignStreams (int64_t stream)
	Assign a fixed random variable stream number to the random variables used by this model.
double	GetDistanceFrom (Ptr< const MobilityModel > position) const
Vector	GetPosition () const
Vector	GetPositionWithReference (const Vector &referencePosition) const
	This method may be used if the position returned may depend on some reference position provided.
double	GetRelativeSpeed (Ptr< const MobilityModel > other) const
Vector	GetVelocity () const
void	SetPosition (const Vector &position)
Public Member Functions inherited from ns3::Object
	Object ()
	Caller graph was not generated because of its size.
	~Object () override
	Destructor.
void	AggregateObject (Ptr< Object > other)
	Aggregate two Objects together.
void	Dispose ()
	Dispose of this Object.
AggregateIterator	GetAggregateIterator () const
	Get an iterator to the Objects aggregated to this one.
TypeId	GetInstanceTypeId () const final
	Get the most derived TypeId for this Object.
template<>
Ptr< Object >	GetObject () const
	Specialization of () for objects of type ns3::Object.
template<typename T>
Ptr< T >	GetObject () const
	Get a pointer to the requested aggregated Object.
template<>
Ptr< Object >	GetObject (TypeId tid) const
	Specialization of (TypeId tid) for objects of type ns3::Object.
template<typename T>
Ptr< T >	GetObject (TypeId tid) const
	Get a pointer to the requested aggregated Object by TypeId.
void	Initialize ()
	Invoke DoInitialize on all Objects aggregated to this one.
bool	IsInitialized () const
	Check if the object has been initialized.
void	UnidirectionalAggregateObject (Ptr< Object > other)
	Aggregate an Object to another Object.
Public Member Functions inherited from ns3::SimpleRefCount< Object, ObjectBase, ObjectDeleter >
	SimpleRefCount ()
	Default constructor.
uint32_t	GetReferenceCount () const
	Get the reference count of the object.
SimpleRefCount &	operator= (const SimpleRefCount &o)
	Assignment operator.
void	Ref () const
	Increment the reference count.
void	Unref () const
	Decrement the reference count.
Public Member Functions inherited from ns3::ObjectBase
virtual	~ObjectBase ()
	Virtual destructor.
void	GetAttribute (std::string name, AttributeValue &value, bool permissive=false) const
	Get the value of an attribute, raising fatal errors if unsuccessful.
bool	GetAttributeFailSafe (std::string name, AttributeValue &value) const
	Get the value of an attribute without raising errors.
void	SetAttribute (std::string name, const AttributeValue &value)
	Set a single attribute, raising fatal errors if unsuccessful.
bool	SetAttributeFailSafe (std::string name, const AttributeValue &value)
	Set a single attribute without raising errors.
bool	TraceConnect (std::string name, std::string context, const CallbackBase &cb)
	Connect a TraceSource to a Callback with a context.
bool	TraceConnectWithoutContext (std::string name, const CallbackBase &cb)
	Connect a TraceSource to a Callback without a context.
bool	TraceDisconnect (std::string name, std::string context, const CallbackBase &cb)
	Disconnect from a TraceSource a Callback previously connected with a context.
bool	TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb)
	Disconnect from a TraceSource a Callback previously connected without a context.

Static Public Member Functions
static TypeId	GetTypeId ()
	Get the type ID.
Static Public Member Functions inherited from ns3::GeocentricConstantPositionMobilityModel
static TypeId	GetTypeId ()
	Register this type with the TypeId system.
Static Public Member Functions inherited from ns3::MobilityModel
static TypeId	GetTypeId ()
	Register this type with the TypeId system.
Static Public Member Functions inherited from ns3::Object
static TypeId	GetTypeId ()
	Register this type.
Static Public Member Functions inherited from ns3::ObjectBase
static TypeId	GetTypeId ()
	Get the type ID.

Private Member Functions
double	CalcLongitude (Time t) const
	Calculate the ECEF longitude of the ascending node at simulation time t.
Vector	CalcPosition (Time t) const
	Calculate the position at time t.
void	DoDispose () override
	Destructor implementation.
Vector	DoGetPosition () const override
	Returns the node current position.
Vector	DoGetVelocity () const override
	Returns the current velocity of the node.
void	DoInitialize () override
	Initialize() implementation.
void	DoSetPosition (const Vector &position) override
	Sets the node position via argument.
void	NotifyCourseChangeAndReschedule ()
	Fire NotifyCourseChange and reschedule at m_resolutionTimeStep.
Vector3D	PlaneNorm (Time t) const
	Get the normal vector of the orbital plane.
Vector3D	RotatePlane (double theta, const Vector3D &v, Time t) const
	Rotates a position vector by angle 'a' around the orbital plane normal, using the Rodrigues rotation formula (see https://en.wikipedia.org/wiki/Rodrigues%27_rotation_formula ).

Private Attributes
double	m_argumentOfLatitude
	Argument of latitude in rad.
EventId	m_courseChangeEvent
	Event for course change notification.
double	m_inclination
	Inclination in rad.
double	m_longitude
	Longitudinal offset in rad.
double	m_orbitalSpeed
	Orbital speed in m/s; negative means compute from gravity.
double	m_orbitHeight
	Orbit height in km.
Time	m_resolutionTimeStep
	Time interval between CourseChange notifications; zero disables periodic notifications.

Additional Inherited Members
Public Types inherited from ns3::MobilityModel
typedef void(*	TracedCallback) (Ptr< const MobilityModel > model)
	TracedCallback signature.
Protected Member Functions inherited from ns3::MobilityModel
void	NotifyCourseChange () const
	Must be invoked by subclasses when the course of the position changes to notify course change listeners.
Protected Member Functions inherited from ns3::Object
	Object (const Object &o)
	Copy an Object.
virtual void	NotifyNewAggregate ()
	Notify all Objects aggregated to this one of a new Object being aggregated.
Protected Member Functions inherited from ns3::ObjectBase
void	ConstructSelf (const AttributeConstructionList &attributes)
	Complete construction of ObjectBase; invoked by derived classes.
virtual void	NotifyConstructionCompleted ()
	Notifier called once the ObjectBase is fully constructed.
Related Symbols inherited from ns3::ObjectBase
static TypeId	GetObjectIid ()
	Ensure the TypeId for ObjectBase gets fully configured to anchor the inheritance tree properly.

Detailed Description

Keep track of the orbital position and velocity of a satellite.

This uses simple circular orbits based on the inclination of the orbital plane and the altitude of the satellite. Assumes earth is a perfect sphere.

Note: Position in DoSetPosition() is in degrees, not the usual meters. Note: Altitude is stored in km, not the usual ns-3 m.

This model is distinct from GeocentricEcefMobilityModel in that it implements a dynamic circular orbital model, whereas GeocentricEcefMobilityModel is intended for ECEF coordinates that do not evolve according to orbital dynamics.

Definition at line 42 of file leo-circular-orbit-mobility-model.h.

Constructor & Destructor Documentation

◆ LeoCircularOrbitMobilityModel()

ns3::LeoCircularOrbitMobilityModel::LeoCircularOrbitMobilityModel ( )

constructor

Todo: The current implementation uses a periodic event to trigger NotifyCourseChange(). As suggested by reviewers, a more idiomatic approach would be to rely on the underlying MobilityModel trace source. However, due to the continuous nature of LEO orbit changes, the periodic approximation is currently used.

Definition at line 66 of file leo-circular-orbit-mobility-model.cc.

References ns3::GeocentricConstantPositionMobilityModel::GeocentricConstantPositionMobilityModel(), m_argumentOfLatitude, m_longitude, m_orbitalSpeed, and NS_LOG_FUNCTION.

Referenced by GetTypeId().

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◆ ~LeoCircularOrbitMobilityModel()

ns3::LeoCircularOrbitMobilityModel::~LeoCircularOrbitMobilityModel ( )

override

destructor

Definition at line 82 of file leo-circular-orbit-mobility-model.cc.

References m_courseChangeEvent, and NS_LOG_FUNCTION.

Member Function Documentation

◆ CalcLongitude()

double ns3::LeoCircularOrbitMobilityModel::CalcLongitude ( Time t ) const

private

Calculate the ECEF longitude of the ascending node at simulation time t.

The orbital plane drifts westward in the ECEF frame because the Earth rotates eastward, so this returns m_longitude minus the Earth-rotation angle accumulated over time t.

Parameters

t time

Returns: longitude of the ascending node in radians (ECEF)

Definition at line 140 of file leo-circular-orbit-mobility-model.cc.

References ns3::Days(), and m_longitude.

Referenced by CalcPosition(), and PlaneNorm().

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◆ CalcPosition()

Vector ns3::LeoCircularOrbitMobilityModel::CalcPosition ( Time t ) const

private

Calculate the position at time t.

The returned Vector contains Cartesian ECEF coordinates in meters. Note that this differs from DoSetPosition(), where the Vector encodes angular orbital parameters (longitude and offset in degrees); that discrepancy is a consequence of the MobilityModel base class interface, which uses a single Vector type for both input and output.

Parameters

t	simulation time

Returns: ECEF position in meters

Definition at line 171 of file leo-circular-orbit-mobility-model.cc.

References CalcLongitude(), GetAngularVelocity(), ns3::Time::GetSeconds(), m_argumentOfLatitude, m_inclination, m_orbitHeight, ns3::M_PER_KM, RotatePlane(), and x.

Referenced by DoGetGeocentricPosition(), DoGetPosition(), and NotifyCourseChangeAndReschedule().

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◆ Copy()

Ptr< MobilityModel > ns3::LeoCircularOrbitMobilityModel::Copy ( ) const

inlineoverridevirtual

Copy function allows one to copy the underlying MobilityModel from a MobilityModel pointer, by calling each children Copy implementation.

This is primarily used by wraparound models for the spectrum channel.

Returns: a copy of the current mobility model

Reimplemented from ns3::GeocentricConstantPositionMobilityModel.

Definition at line 119 of file leo-circular-orbit-mobility-model.h.

References ns3::CreateObject().

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◆ DoDispose()

void ns3::LeoCircularOrbitMobilityModel::DoDispose ( )

overrideprivatevirtual

Destructor implementation.

This method is called by Dispose() or by the Object's destructor, whichever comes first.

Subclasses are expected to implement their real destruction code in an overridden version of this method and chain up to their parent's implementation once they are done. i.e, for simplicity, the destructor of every subclass should be empty and its content should be moved to the associated DoDispose() method.

It is safe to call GetObject() from within this method.

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Reimplemented from ns3::Object.

Definition at line 212 of file leo-circular-orbit-mobility-model.cc.

References ns3::Object::DoDispose(), m_courseChangeEvent, and NS_LOG_FUNCTION.

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◆ DoGetGeocentricPosition()

Vector ns3::LeoCircularOrbitMobilityModel::DoGetGeocentricPosition ( ) const

overridevirtual

Returns the Geocentric Position of the Node in ECEF (cartesian).

Returns: ECEF position in meters

Reimplemented from ns3::GeocentricConstantPositionMobilityModel.

Definition at line 227 of file leo-circular-orbit-mobility-model.cc.

References CalcPosition(), and ns3::Simulator::Now().

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◆ DoGetPosition()

Vector ns3::LeoCircularOrbitMobilityModel::DoGetPosition ( ) const

overrideprivatevirtual

Returns the node current position.

Returns: ECEF position in meters

Reimplemented from ns3::GeocentricConstantPositionMobilityModel.

Definition at line 234 of file leo-circular-orbit-mobility-model.cc.

References CalcPosition(), and ns3::Simulator::Now().

Referenced by DoGetVelocity().

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◆ DoGetVelocity()

Vector ns3::LeoCircularOrbitMobilityModel::DoGetVelocity ( ) const

overrideprivatevirtual

Returns the current velocity of the node.

Returns: velocity vector in m/s (ECEF)

Reimplemented from ns3::GeocentricConstantPositionMobilityModel.

Definition at line 109 of file leo-circular-orbit-mobility-model.cc.

References ns3::CrossProduct(), DoGetPosition(), ns3::Vector3D::GetLength(), GetSpeed(), ns3::Simulator::Now(), and PlaneNorm().

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◆ DoInitialize()

void ns3::LeoCircularOrbitMobilityModel::DoInitialize ( )

overrideprivatevirtual

Initialize() implementation.

This method is called only once by Initialize(). If the user calls Initialize() multiple times, DoInitialize() is called only the first time.

Subclasses are expected to override this method and chain up to their parent's implementation once they are done. It is safe to call GetObject() and AggregateObject() from within this method.

Reimplemented from ns3::Object.

Definition at line 197 of file leo-circular-orbit-mobility-model.cc.

References ns3::Object::DoInitialize(), m_courseChangeEvent, m_resolutionTimeStep, NotifyCourseChangeAndReschedule(), NS_LOG_FUNCTION, NS_LOG_INFO, ns3::Time::S, ns3::Simulator::Schedule(), and ns3::Seconds().

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◆ DoSetPosition()

void ns3::LeoCircularOrbitMobilityModel::DoSetPosition ( const Vector & position )

overrideprivatevirtual

Sets the node position via argument.

Note: This method deviates from the MobilityModel interface which typically expects position in meters. For this model, position is interpreted as angular coordinates (degrees) because specifying orbital parameters (longitude of ascending node and offset) is more intuitive in degrees than in meters relative to the earth's center.

Parameters

position position.x is the longitude of the ascending node in degrees; position.y is the argument of latitude on the orbital plane in degrees. Both are converted to radians internally.

Reimplemented from ns3::GeocentricConstantPositionMobilityModel.

Definition at line 240 of file leo-circular-orbit-mobility-model.cc.

References ns3::DegreesToRadians(), GetAltitudeKm(), GetAngularVelocity(), GetInclination(), m_argumentOfLatitude, m_longitude, ns3::MobilityModel::NotifyCourseChange(), NS_LOG_FUNCTION, and NS_LOG_INFO.

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◆ GetAltitude()

double ns3::LeoCircularOrbitMobilityModel::GetAltitude ( ) const

Gets the altitude in m.

Returns: the altitude in m (above Earth surface)

Definition at line 257 of file leo-circular-orbit-mobility-model.cc.

References GetAltitudeKm(), and ns3::M_PER_KM.

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◆ GetAltitudeKm()

double ns3::LeoCircularOrbitMobilityModel::GetAltitudeKm ( ) const

Gets the altitude in km (not the usual meters used in ns-3).

Returns: the altitude in km (above Earth surface)

Definition at line 270 of file leo-circular-orbit-mobility-model.cc.

References ns3::GeographicPositions::EARTH_SPHERE_RADIUS, m_orbitHeight, and ns3::M_PER_KM.

Referenced by DoSetPosition(), GetAltitude(), and GetTypeId().

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◆ GetAngularVelocity()

double ns3::LeoCircularOrbitMobilityModel::GetAngularVelocity ( ) const

Get the orbital angular velocity.

Computed from Keplerian mechanics: omega = sqrt(GM / r^3). Negated for retrograde orbits (inclination > 90 degrees).

If the user set an orbital angular velocity >= 0, it will be used instead.

Returns: angular velocity in rad/s

Definition at line 146 of file leo-circular-orbit-mobility-model.cc.

References ns3::GeographicPositions::LEO_EARTH_GGC, m_inclination, m_orbitalSpeed, m_orbitHeight, and ns3::M_PER_KM.

Referenced by CalcPosition(), and DoSetPosition().

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◆ GetInclination()

double ns3::LeoCircularOrbitMobilityModel::GetInclination ( ) const

Gets the inclination.

Returns: the inclination in degrees

Definition at line 283 of file leo-circular-orbit-mobility-model.cc.

References m_inclination, and ns3::RadiansToDegrees().

Referenced by DoSetPosition(), and GetTypeId().

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◆ GetSpeed()

double ns3::LeoCircularOrbitMobilityModel::GetSpeed ( ) const

Gets the speed of the node.

Returns: the speed in m/s

Definition at line 95 of file leo-circular-orbit-mobility-model.cc.

References ns3::GeographicPositions::LEO_EARTH_GGC, m_orbitalSpeed, m_orbitHeight, and ns3::M_PER_KM.

Referenced by DoGetVelocity().

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◆ GetTypeId()

TypeId ns3::LeoCircularOrbitMobilityModel::GetTypeId ( )

static

Get the type ID.

Returns: the object TypeId

Definition at line 32 of file leo-circular-orbit-mobility-model.cc.

References ns3::GeocentricConstantPositionMobilityModel::GeocentricConstantPositionMobilityModel(), LeoCircularOrbitMobilityModel(), GetAltitudeKm(), GetInclination(), m_orbitalSpeed, m_resolutionTimeStep, ns3::MakeDoubleAccessor(), ns3::MakeDoubleChecker(), ns3::MakeTimeAccessor(), ns3::MakeTimeChecker(), ns3::Seconds(), SetAltitudeKm(), SetInclination(), and ns3::TypeId::SetParent().

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◆ NotifyCourseChangeAndReschedule()

void ns3::LeoCircularOrbitMobilityModel::NotifyCourseChangeAndReschedule ( )

private

Fire NotifyCourseChange and reschedule at m_resolutionTimeStep.

Definition at line 185 of file leo-circular-orbit-mobility-model.cc.

References CalcPosition(), m_courseChangeEvent, m_resolutionTimeStep, ns3::MobilityModel::NotifyCourseChange(), NotifyCourseChangeAndReschedule(), ns3::Simulator::Now(), NS_LOG_DEBUG, NS_LOG_FUNCTION, and ns3::Simulator::Schedule().

Referenced by DoInitialize(), and NotifyCourseChangeAndReschedule().

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◆ PlaneNorm()

Vector3D ns3::LeoCircularOrbitMobilityModel::PlaneNorm ( Time t ) const

private

Get the normal vector of the orbital plane.

Parameters

t	the amount of time passed since the start of the simulation

Returns: the normal vector.

Definition at line 119 of file leo-circular-orbit-mobility-model.cc.

References CalcLongitude(), and m_inclination.

Referenced by DoGetVelocity(), and RotatePlane().

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◆ RotatePlane()

Vector3D ns3::LeoCircularOrbitMobilityModel::RotatePlane	(	double	theta,
		const Vector3D &	v,
		Time	t ) const

private

Rotates a position vector by angle 'a' around the orbital plane normal, using the Rodrigues rotation formula (see https://en.wikipedia.org/wiki/Rodrigues%27_rotation_formula ).

Parameters

theta	angle by which to rotate, in radians
v	position vector to rotate, in meters (ECEF)
t	time passed since simulation start (used to compute the current orbital plane normal)