a Friis propagation loss model More...
#include "propagation-loss-model.h"
Public Member Functions | |
FriisPropagationLossModel () | |
double | GetFrequency (void) const |
double | GetMinLoss (void) const |
double | GetSystemLoss (void) const |
void | SetFrequency (double frequency) |
void | SetMinLoss (double minLoss) |
void | SetSystemLoss (double systemLoss) |
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PropagationLossModel () | |
virtual | ~PropagationLossModel () |
int64_t | AssignStreams (int64_t stream) |
If this loss model uses objects of type RandomVariableStream, set the stream numbers to the integers starting with the offset 'stream'. More... | |
double | CalcRxPower (double txPowerDbm, Ptr< MobilityModel > a, Ptr< MobilityModel > b) const |
Returns the Rx Power taking into account all the PropagationLossModel(s) chained to the current one. More... | |
Ptr< PropagationLossModel > | GetNext () |
Gets the next PropagationLossModel in the chain of loss models that act on the signal. More... | |
void | SetNext (Ptr< PropagationLossModel > next) |
Enables a chain of loss models to act on the signal. More... | |
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Object () | |
Constructor. More... | |
virtual | ~Object () |
Destructor. More... | |
void | AggregateObject (Ptr< Object > other) |
Aggregate two Objects together. More... | |
void | Dispose (void) |
Dispose of this Object. More... | |
AggregateIterator | GetAggregateIterator (void) const |
Get an iterator to the Objects aggregated to this one. More... | |
virtual TypeId | GetInstanceTypeId (void) const |
Get the most derived TypeId for this Object. More... | |
template<typename T > | |
Ptr< T > | GetObject (void) const |
Get a pointer to the requested aggregated Object. More... | |
template<typename T > | |
Ptr< T > | GetObject (TypeId tid) const |
Get a pointer to the requested aggregated Object by TypeId. More... | |
void | Initialize (void) |
Invoke DoInitialize on all Objects aggregated to this one. More... | |
bool | IsInitialized (void) const |
Check if the object has been initialized. More... | |
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SimpleRefCount () | |
Default constructor. More... | |
SimpleRefCount (const SimpleRefCount &o) | |
Copy constructor. More... | |
uint32_t | GetReferenceCount (void) const |
Get the reference count of the object. More... | |
SimpleRefCount & | operator= (const SimpleRefCount &o) |
Assignment operator. More... | |
void | Ref (void) const |
Increment the reference count. More... | |
void | Unref (void) const |
Decrement the reference count. More... | |
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virtual | ~ObjectBase () |
Virtual destructor. More... | |
void | GetAttribute (std::string name, AttributeValue &value) const |
Get the value of an attribute, raising fatal errors if unsuccessful. More... | |
bool | GetAttributeFailSafe (std::string name, AttributeValue &value) const |
Get the value of an attribute without raising erros. More... | |
void | SetAttribute (std::string name, const AttributeValue &value) |
Set a single attribute, raising fatal errors if unsuccessful. More... | |
bool | SetAttributeFailSafe (std::string name, const AttributeValue &value) |
Set a single attribute without raising errors. More... | |
bool | TraceConnect (std::string name, std::string context, const CallbackBase &cb) |
Connect a TraceSource to a Callback with a context. More... | |
bool | TraceConnectWithoutContext (std::string name, const CallbackBase &cb) |
Connect a TraceSource to a Callback without a context. More... | |
bool | TraceDisconnect (std::string name, std::string context, const CallbackBase &cb) |
Disconnect from a TraceSource a Callback previously connected with a context. More... | |
bool | TraceDisconnectWithoutContext (std::string name, const CallbackBase &cb) |
Disconnect from a TraceSource a Callback previously connected without a context. More... | |
Static Public Member Functions | |
static TypeId | GetTypeId (void) |
Get the type ID. More... | |
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static TypeId | GetTypeId (void) |
Get the type ID. More... | |
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static TypeId | GetTypeId (void) |
Register this type. More... | |
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static TypeId | GetTypeId (void) |
Get the type ID. More... | |
Private Member Functions | |
FriisPropagationLossModel (const FriisPropagationLossModel &) | |
Copy constructor. More... | |
double | DbmFromW (double w) const |
Transforms a Watt value to Dbm. More... | |
double | DbmToW (double dbm) const |
Transforms a Dbm value to Watt. More... | |
virtual int64_t | DoAssignStreams (int64_t stream) |
Subclasses must implement this; those not using random variables can return zero. More... | |
virtual double | DoCalcRxPower (double txPowerDbm, Ptr< MobilityModel > a, Ptr< MobilityModel > b) const |
Returns the Rx Power taking into account only the particular PropagationLossModel. More... | |
FriisPropagationLossModel & | operator= (const FriisPropagationLossModel &) |
Copy constructor. More... | |
Private Attributes | |
double | m_frequency |
the carrier frequency More... | |
double | m_lambda |
the carrier wavelength More... | |
double | m_minLoss |
the minimum loss More... | |
double | m_systemLoss |
the system loss More... | |
Additional Inherited Members | |
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Object (const Object &o) | |
Copy an Object. More... | |
virtual void | DoDispose (void) |
Destructor implementation. More... | |
virtual void | DoInitialize (void) |
Initialize() implementation. More... | |
virtual void | NotifyNewAggregate (void) |
Notify all Objects aggregated to this one of a new Object being aggregated. More... | |
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void | ConstructSelf (const AttributeConstructionList &attributes) |
Complete construction of ObjectBase; invoked by derived classes. More... | |
virtual void | NotifyConstructionCompleted (void) |
Notifier called once the ObjectBase is fully constructed. More... | |
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static TypeId | GetObjectIid (void) |
Ensure the TypeId for ObjectBase gets fully configured to anchor the inheritance tree properly. More... | |
a Friis propagation loss model
The Friis propagation loss model was first described in "A Note on a Simple Transmission Formula", by "Harald T. Friis".
The original equation was described as: with the following equation for the case of an isotropic antenna with no heat loss:
The final equation becomes:
Modern extensions to this original equation are:
With:
In the implementation, is calculated as
, where
m/s is the speed of light in vacuum, and
is the frequency in Hz which can be configured by the user via the Frequency attribute.
The Friis model is valid only for propagation in free space within the so-called far field region, which can be considered approximately as the region for . The model will still return a value for
, as doing so (rather than triggering a fatal error) is practical for many simulation scenarios. However, we stress that the values obtained in such conditions shall not be considered realistic.
Related with this issue, we note that the Friis formula is undefined for , and results in
for
. Both these conditions occur outside of the far field region, so in principle the Friis model shall not be used in these conditions. In practice, however, Friis is often used in scenarios where accurate propagation modeling is not deemed important, and values of
can occur. To allow practical use of the model in such scenarios, we have to 1) return some value for
, and 2) avoid large discontinuities in propagation loss values (which could lead to artifacts such as bogus capture effects which are much worse than inaccurate propagation loss values). The two issues are conflicting, as, according to the Friis formula,
; so if, for
, we use a fixed loss value, we end up with an infinitely large discontinuity, which as we discussed can cause undesirable simulation artifacts.
To avoid these artifact, this implementation of the Friis model provides an attribute called MinLoss which allows to specify the minimum total loss (in dB) returned by the model. This is used in such a way that continuously increases for
, until MinLoss is reached, and then stay constant; this allow to return a value for
and at the same time avoid discontinuities. The model won't be much realistic, but at least the simulation artifacts discussed before are avoided. The default value of MinLoss is 0 dB, which means that by default the model will return
for
. We note that this value of
is outside of the far field region, hence the validity of the model in the far field region is not affected.
ns3::FriisPropagationLossModel is accessible through the following paths with Config::Set and Config::Connect:
No TraceSources are defined for this type.
Size of this type is 72 bytes (on a 64-bit architecture).
Definition at line 261 of file propagation-loss-model.h.
ns3::FriisPropagationLossModel::FriisPropagationLossModel | ( | ) |
Definition at line 172 of file propagation-loss-model.cc.
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private |
Copy constructor.
Defined and unimplemented to avoid misuse
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private |
Transforms a Watt value to Dbm.
w | the Watt value |
Definition at line 218 of file propagation-loss-model.cc.
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private |
Transforms a Dbm value to Watt.
dbm | the Dbm value |
Definition at line 211 of file propagation-loss-model.cc.
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privatevirtual |
Subclasses must implement this; those not using random variables can return zero.
Implements ns3::PropagationLossModel.
Definition at line 275 of file propagation-loss-model.cc.
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privatevirtual |
Returns the Rx Power taking into account only the particular PropagationLossModel.
txPowerDbm | current transmission power (in dBm) |
a | the mobility model of the source |
b | the mobility model of the destination |
Implements ns3::PropagationLossModel.
Definition at line 225 of file propagation-loss-model.cc.
References ns3::MobilityModel::GetDistanceFrom(), m_lambda, m_minLoss, m_systemLoss, max, NS_LOG_DEBUG, and NS_LOG_WARN.
double ns3::FriisPropagationLossModel::GetFrequency | ( | void | ) | const |
Definition at line 205 of file propagation-loss-model.cc.
References m_frequency.
Referenced by GetTypeId().
double ns3::FriisPropagationLossModel::GetMinLoss | ( | void | ) | const |
Definition at line 191 of file propagation-loss-model.cc.
References m_minLoss.
Referenced by GetTypeId().
double ns3::FriisPropagationLossModel::GetSystemLoss | ( | void | ) | const |
Definition at line 181 of file propagation-loss-model.cc.
References m_systemLoss.
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static |
Get the type ID.
Definition at line 146 of file propagation-loss-model.cc.
References GetFrequency(), GetMinLoss(), m_systemLoss, ns3::MakeDoubleAccessor(), SetFrequency(), SetMinLoss(), and ns3::TypeId::SetParent().
Referenced by ns3::LteHelper::GetTypeId().
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private |
Copy constructor.
Defined and unimplemented to avoid misuse
void ns3::FriisPropagationLossModel::SetFrequency | ( | double | frequency | ) |
frequency | (Hz) |
Set the carrier frequency used in the Friis model calculation.
Definition at line 197 of file propagation-loss-model.cc.
References m_frequency, and m_lambda.
Referenced by GetTypeId().
void ns3::FriisPropagationLossModel::SetMinLoss | ( | double | minLoss | ) |
minLoss | the minimum loss (dB) |
no matter how short the distance, the total propagation loss (in dB) will always be greater or equal than this value
Definition at line 186 of file propagation-loss-model.cc.
References m_minLoss.
Referenced by GetTypeId().
void ns3::FriisPropagationLossModel::SetSystemLoss | ( | double | systemLoss | ) |
systemLoss | (dimension-less) |
Set the system loss used by the Friis propagation model.
Definition at line 176 of file propagation-loss-model.cc.
References m_systemLoss.
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private |
the carrier frequency
Definition at line 341 of file propagation-loss-model.h.
Referenced by GetFrequency(), and SetFrequency().
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private |
the carrier wavelength
Definition at line 340 of file propagation-loss-model.h.
Referenced by DoCalcRxPower(), and SetFrequency().
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private |
the minimum loss
Definition at line 343 of file propagation-loss-model.h.
Referenced by DoCalcRxPower(), GetMinLoss(), and SetMinLoss().
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private |
the system loss
Definition at line 342 of file propagation-loss-model.h.
Referenced by DoCalcRxPower(), GetSystemLoss(), GetTypeId(), and SetSystemLoss().