Implementation of the strongest cell handover algorithm, based on RSRP measurements and Event A3. More...

#include "a3-rsrp-handover-algorithm.h"

Inheritance diagram for ns3::A3RsrpHandoverAlgorithm:

Collaboration diagram for ns3::A3RsrpHandoverAlgorithm:

Public Member Functions
	A3RsrpHandoverAlgorithm ()
	Creates a strongest cell handover algorithm instance.

	~A3RsrpHandoverAlgorithm () override

LteHandoverManagementSapProvider *	GetLteHandoverManagementSapProvider () override
	Export the "provider" part of the Handover Management SAP interface.

void	SetLteHandoverManagementSapUser (LteHandoverManagementSapUser *s) override
	Set the "user" part of the Handover Management SAP interface that this handover algorithm instance will interact with.

Public Member Functions inherited from ns3::LteHandoverAlgorithm
	LteHandoverAlgorithm ()

	~LteHandoverAlgorithm () override

Public Member Functions inherited from ns3::Object
	Object ()
	Constructor.

	~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 override
	Get the most derived TypeId for this Object.

template<typename T >
Ptr< T >	GetObject () const
	Get a pointer to the requested aggregated Object.

template<>
Ptr< Object >	GetObject () const
	Specialization of () 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.

template<>
Ptr< Object >	GetObject (TypeId tid) const
	Specialization of (TypeId tid) for objects of type ns3::Object.

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.

	SimpleRefCount (const SimpleRefCount &o)
	Copy 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::LteHandoverAlgorithm
static TypeId	GetTypeId ()
	Get the type ID.

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.

Protected Member Functions
void	DoDispose () override
	Destructor implementation.

void	DoInitialize () override
	Initialize() implementation.

void	DoReportUeMeas (uint16_t rnti, LteRrcSap::MeasResults measResults) override
	Implementation of LteHandoverManagementSapProvider::ReportUeMeas.

Protected Member Functions inherited from ns3::LteHandoverAlgorithm
void	DoDispose () override
	Destructor implementation.

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.

Private Member Functions
bool	IsValidNeighbour (uint16_t cellId)
	Determines if a neighbour cell is a valid destination for handover.

Private Attributes
LteHandoverManagementSapProvider *	m_handoverManagementSapProvider
	Receive API calls from the eNodeB RRC instance.

LteHandoverManagementSapUser *	m_handoverManagementSapUser
	Interface to the eNodeB RRC instance.

double	m_hysteresisDb
	The `Hysteresis` attribute.

std::vector< uint8_t >	m_measIds
	The expected measurement identity for A3 measurements.

Time	m_timeToTrigger
	The `TimeToTrigger` attribute.

Friends
class	MemberLteHandoverManagementSapProvider< A3RsrpHandoverAlgorithm >
	let the forwarder class access the protected and private members

Additional Inherited Members
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

Implementation of the strongest cell handover algorithm, based on RSRP measurements and Event A3.

The algorithm utilizes Event A3 (Section 5.5.4.4 of 3GPP TS 36.331) UE measurements and the Reference Signal Reference Power (RSRP). It is defined as the event when the UE perceives that a neighbour cell's RSRP is better than the serving cell's RSRP.

Handover margin (a.k.a. hysteresis) and time-to-trigger (TTT) can be configured to delay the event triggering. The values of these parameters apply to all attached UEs.

The following code snippet is an example of using and configuring the handover algorithm in a simulation program:

Ptr<LteHelper> lteHelper = CreateObject<LteHelper> ();

NodeContainer enbNodes;
// configure the nodes here...

lteHelper->SetHandoverAlgorithmType ("ns3::A3RsrpHandoverAlgorithm");
lteHelper->SetHandoverAlgorithmAttribute ("Hysteresis",
                                          DoubleValue (3.0));
lteHelper->SetHandoverAlgorithmAttribute ("TimeToTrigger",
                                          TimeValue (MilliSeconds (256)));
NetDeviceContainer enbLteDevs = lteHelper->InstallEnbDevice (enbNodes);

Note: Setting the handover algorithm type and attributes after the call to LteHelper::InstallEnbDevice does not have any effect to the devices that have already been installed.

Definition at line 54 of file a3-rsrp-handover-algorithm.h.

Constructor & Destructor Documentation

◆ A3RsrpHandoverAlgorithm()

ns3::A3RsrpHandoverAlgorithm::A3RsrpHandoverAlgorithm ( )

Creates a strongest cell handover algorithm instance.

Definition at line 27 of file a3-rsrp-handover-algorithm.cc.

References m_handoverManagementSapProvider, MemberLteHandoverManagementSapProvider< A3RsrpHandoverAlgorithm >, and NS_LOG_FUNCTION.

◆ ~A3RsrpHandoverAlgorithm()

ns3::A3RsrpHandoverAlgorithm::~A3RsrpHandoverAlgorithm ( )

override

Definition at line 35 of file a3-rsrp-handover-algorithm.cc.

References NS_LOG_FUNCTION.

Member Function Documentation

◆ DoDispose()

void ns3::A3RsrpHandoverAlgorithm::DoDispose ( )

overrideprotectedvirtual

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.

Reimplemented from ns3::Object.

Definition at line 105 of file a3-rsrp-handover-algorithm.cc.

References m_handoverManagementSapProvider, and NS_LOG_FUNCTION.

◆ DoInitialize()

void ns3::A3RsrpHandoverAlgorithm::DoInitialize ( )

overrideprotectedvirtual

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 82 of file a3-rsrp-handover-algorithm.cc.

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◆ DoReportUeMeas()

void ns3::A3RsrpHandoverAlgorithm::DoReportUeMeas	(	uint16_t	rnti,
		LteRrcSap::MeasResults	measResults )

overrideprotectedvirtual

Implementation of LteHandoverManagementSapProvider::ReportUeMeas.

Parameters

rnti	Radio Network Temporary Identity, an integer identifying the UE where the report originates from
measResults	a single report of one measurement identity

Implements ns3::LteHandoverAlgorithm.

Definition at line 112 of file a3-rsrp-handover-algorithm.cc.

References ns3::LteRrcSap::MeasResults::haveMeasResultNeighCells, IsValidNeighbour(), m_handoverManagementSapUser, m_measIds, ns3::LteRrcSap::MeasResults::measId, ns3::LteRrcSap::MeasResults::measResultListEutra, ns3::LteRrcSap::MeasResults::measResultPCell, NS_LOG_FUNCTION, NS_LOG_LOGIC, NS_LOG_WARN, ns3::LteRrcSap::MeasResultPCell::rsrpResult, and ns3::LteHandoverManagementSapUser::TriggerHandover().

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◆ GetLteHandoverManagementSapProvider()

LteHandoverManagementSapProvider * ns3::A3RsrpHandoverAlgorithm::GetLteHandoverManagementSapProvider ( )

overridevirtual

Export the "provider" part of the Handover Management SAP interface.

Returns: the reference to the "provider" part of the interface, typically to be kept by an LteEnbRrc instance

Implements ns3::LteHandoverAlgorithm.

Definition at line 75 of file a3-rsrp-handover-algorithm.cc.

References m_handoverManagementSapProvider, and NS_LOG_FUNCTION.

◆ GetTypeId()

TypeId ns3::A3RsrpHandoverAlgorithm::GetTypeId ( )

static

Get the type ID.

Returns: the object TypeId

Definition at line 41 of file a3-rsrp-handover-algorithm.cc.

References m_hysteresisDb, m_timeToTrigger, ns3::MakeDoubleAccessor(), ns3::MakeDoubleChecker(), ns3::MakeTimeAccessor(), ns3::MakeTimeChecker(), ns3::MilliSeconds(), and ns3::TypeId::SetParent().

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◆ IsValidNeighbour()

bool ns3::A3RsrpHandoverAlgorithm::IsValidNeighbour ( uint16_t cellId )

private

Determines if a neighbour cell is a valid destination for handover.

Currently always return true.

Parameters

cellId The cell ID of the neighbour cell.

Returns: True if the cell is a valid destination for handover.

Todo: In the future, this function can be expanded to validate whether the neighbour cell is a valid target cell, e.g., taking into account the NRT in ANR and whether it is a CSG cell with closed access.

Definition at line 164 of file a3-rsrp-handover-algorithm.cc.

References NS_LOG_FUNCTION.

Referenced by DoReportUeMeas().

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