Superclass:  Path Loss

The path_loss_free_space object represents a free-space path loss model.

Free-space path loss can be described entirely by three parameters:

1. the carrier wavelength $\lambda$
2. the distance $d$
3. the path loss exponent $\eta$

The path loss (or attenuation) stemming from a free-space path loss model can be deterministically written as

where $G^2$ is the path gain and $1/G^2$ is the path loss.

When $\eta = 2$, this is the classical Friis formula for path loss. Typically, $\eta \geq 2$ except in rare settings with significant clutter. Most often, $\eta \in [2,4]$.

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 ($\eta$).

### 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 $G$ by simply atten $= G^{-2}$.

### 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:

### 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.

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#### 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

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#### 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

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#### initialize()

Initializes a path loss object.

Usage:
initialize()

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#### initialize_free_space()

Initializes a free-space path loss object.

Usage:
initialize_free_space()

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#### 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

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#### 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.

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#### 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:

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#### 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)

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#### 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

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#### 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

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#### 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)

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#### 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)

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#### 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

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