Free-Space Path Loss
A free-space path loss model.
obj/path_loss/path_loss_free_space.m
Superclass: Path Loss
On This Page
- About
- Creating a Free-Space Path Loss Object
- Key Properties
- Setting the Path Loss Exponent
- Example Setup
- Getting the Attenuation
- List of Properties
- List of Methods
- Methods Documentation
About
The path_loss_free_space
object represents a free-space path loss model.
Free-space path loss can be described entirely by three parameters:
- the carrier wavelength
- the distance
- the path loss exponent
The path loss (or attenuation) stemming from a free-space path loss model can be deterministically written as
where is the path gain and is the path loss.
When , this is the classical Friis formula for path loss. Typically, except in rare settings with significant clutter. Most often, .
The path_loss_free_space
object is a subclass of the path_loss
object.
Creating a Free-Space Path Loss Object
A free-space path loss object path_loss_free_space
can be created via
p = path_loss.create('free-space')
Key Properties
The path_loss_free_space
object inherits all properties of the path_loss
object, the key ones being
p.attenuation
p.carrier_frequency
p.carrier_wavelength
p.propagation_velocity
p.distance
In addition to these, the path_loss_free_space
object also has the property
p.path_loss_exponent
to capture the path loss exponent ().
Setting the Path Loss Exponent
To set the path loss exponent of a free space path loss object p
, use
p.set_path_loss_exponent(ple)
where ple
is the path loss exponent (a traditionally positive number).
Example Setup
A typical path_loss_free_pace
object setup looks something similar to
p = path_loss.create()
p.set_carrier_frequency(fc)
p.set_propagation_velocity(vel)
p.set_distance(d)
p.set_path_loss_exponent(ple)
Invoking a Realization
To realize the path loss, use
atten = p.realization()
which, when appropriately setup, will return the attenuation atten
for the given carrier wavelength, distance, and path loss exponent.
Note that atten
is related to the large-scale gain by simply atten
.
Getting the Attenuation
To get the realized attenuation of a path_loss_free_space
object p
, one can also use
atten = p.get_attenuation()
where atten
is the attenuation of the path loss (power loss, linear scale).
List of Properties
The path_loss_free_space
object contains the following properties:
path_loss_free_space.path_loss_exponent
path_loss_free_space.name
path_loss_free_space.type
path_loss_free_space.distance
path_loss_free_space.attenuation
path_loss_free_space.carrier_frequency
path_loss_free_space.carrier_wavelength
path_loss_free_space.propagation_velocity
List of Methods
The path_loss_free_space
object contains the following methods:
path_loss_free_space.compute_path_loss_attenuation
Computes the path attenuation (path loss) according to the free-space path loss (FSPL) formula.path_loss_free_space.create
Creates a path loss object of a specific type.path_loss_free_space.get_attenuation
Returns the realized attenuation of the path loss model.path_loss_free_space.initialize
Initializes a path loss object.path_loss_free_space.initialize_free_space
Initializes a free-space path loss object.path_loss_free_space.path_loss_free_space
Creates a free-space path loss object.path_loss_free_space.realization
Invokes a realization of the path loss.path_loss_free_space.set_carrier_frequency
Sets the carrier frequency of the channel. Also updates the carrier wavelength accordingly.path_loss_free_space.set_distance
Sets the distance of the path (in meters).path_loss_free_space.set_name
Sets the name of the path loss model.path_loss_free_space.set_path_loss_attenuation
Sets the attenuation of the path loss model.path_loss_free_space.set_path_loss_exponent
Sets the path loss exponent.path_loss_free_space.set_propagation_velocity
Sets the propagation velocity of the channel. Also updates the carrier wavelength accordingly.path_loss_free_space.set_type
Sets the type of path loss model.
Methods Documentation
compute_path_loss_attenuation()
Computes the path attenuation (path loss) according to the free-space path loss (FSPL) formula.
- Usage:
atten = compute_path_loss_attenuation()
- Return Values:
atten
— the path attenuation (path loss) (a power loss)- Notes:
- The free-space path loss (FSPL) equation used is G = (lambda / (4*pi))^2 * (1/d)^ple, where G is the inverse path loss in terms of power.
create(type)
Creates a path loss object of a specific type.
- Usage:
obj = path_loss.create()
obj = path_loss.create(type)
- Input Arguments:
type
— (optional) a string specifying which path loss model to create- Return Values:
obj
— a path loss object
get_attenuation()
Returns the realized attenuation of the path loss model.
- Usage:
val = get_attenuation()
- Return Values:
val
— the attenuation (power loss) of the path
initialize()
Initializes a path loss object.
- Usage:
initialize()
initialize_free_space()
Initializes a free-space path loss object.
- Usage:
initialize_free_space()
path_loss_free_space(name)
Creates a free-space path loss object.
- Usage:
obj = path_loss_free_space()
obj = path_loss_free_space(name)
- Input Arguments:
name
— an optional name for the object- Return Values:
obj
— an object representing free-space path loss
realization()
Invokes a realization of the path loss.
- Usage:
atten = realization()
- Return Values:
atten
— the realized path loss attenuation- Notes:
- Since no random variables are involved in the FSPL equation, it will be determininstic and thus fixed across realizations.
set_carrier_frequency(fc)
Sets the carrier frequency of the channel. Also updates the carrier wavelength accordingly.
- Usage:
set_carrier_frequency(fc)
- Input Arguments:
fc
— carrier frequency (Hz)- Notes:
- Also updates carrier wavelength.
set_distance(d)
Sets the distance of the path (in meters).
- Usage:
set_distance(d) Sets the distance of the link to a specific
value.
- Input Arguments:
d
— distance of the path (in meters)
set_name(name)
Sets the name of the path loss model.
- Usage:
set_name()
set_name(name)
- Input Arguments:
name
— (optional) a string; if not passed, ‘path-loss’ is the default name used
set_path_loss_attenuation(atten)
Sets the attenuation of the path loss model.
- Usage:
set_path_loss_attenuation(atten)
- Input Arguments:
atten
— the attenuation (power loss) of the path
set_path_loss_exponent(ple)
Sets the path loss exponent.
- Usage:
set_path_loss_exponent(ple)
- Input Arguments:
ple
— path loss exponent (a positive number)
set_propagation_velocity(val)
Sets the propagation velocity of the channel. Also updates the carrier wavelength accordingly.
- Usage:
set_propagation_velocity(val)
- Input Arguments:
val
— propagation velocity (meters/sec)
set_type(type)
Sets the type of path loss model.
- Usage:
set_type()
set_type(type)
- Input Arguments:
type
— (optional) a string; if not passed, ‘default’ is the default type used