PathlossWiki - User contributions [en]

Refractivity

2020-02-21T19:32:33Z

Cassieg:

The refractive index (n) of air is defined as:

n = c/v

[[File:equationtest.wmf]]

where:
*c is the velocity of light in a vacuum.
*v is the velocity of light in air.

A typical value of n is 1.000301. For convenience the refractive index is expressed as refractivity (N)

N = (n-1) x 10^6

which results in a typical value of 301 Refractivity is defined by the equation:

N = 77.6 x (P/T) + 3.732 x 10^5 x (e/T^2)

where:
*P is the atmospheric pressure.
*T is the absolute temperature.
*e is the water vapor pressure.
*N varies with elevation. In a well mixed troposphere, the variation is exponential; however, in the range from 1 to 2 kilometers above sea level, the variation is approximately linear. This is referred to as a constant refractivity gradient. The refractivity gradient determines the microwave beam-bending.

Handling the variations of refractivity with elevation is the major challenge in the design of high reliability microwave links

File:Equationtest.gif

2020-02-21T19:20:17Z

Cassieg:

Point to Point Microwave Link Design

2020-02-21T19:09:15Z

Cassieg:

*[[Fade Mechanisms]]

*[[Basic Link Design Steps]]

*[[Refractivity]]

Point to Point Microwave Link Design

2020-02-21T19:07:15Z

Cassieg:

==[[Fade Mechanisms]]==

[[Basic Link Design Steps]]

[[Refractivity]]

Point to Point Microwave Link Design

2020-02-21T19:07:00Z

Cassieg:

=[[Fade Mechanisms]]=

[[Basic Link Design Steps]]

[[Refractivity]]

Point to Point Microwave Link Design

2020-02-21T19:03:04Z

Cassieg:

[[Fade Mechanisms]]

[[Basic Link Design Steps]]

[[Refractivity]]

Refractivity

2020-02-21T19:01:21Z

Cassieg:

The refractive index (n) of air is defined as:

n = c/v

where:
*c is the velocity of light in a vacuum.
*v is the velocity of light in air.

A typical value of n is 1.000301. For convenience the refractive index is expressed as refractivity (N)

N = (n-1) x 10^6

which results in a typical value of 301 Refractivity is defined by the equation:

N = 77.6 x (P/T) + 3.732 x 10^5 x (e/T^2)

where:
*P is the atmospheric pressure.
*T is the absolute temperature.
*e is the water vapor pressure.
*N varies with elevation. In a well mixed troposphere, the variation is exponential; however, in the range from 1 to 2 kilometers above sea level, the variation is approximately linear. This is referred to as a constant refractivity gradient. The refractivity gradient determines the microwave beam-bending.

Handling the variations of refractivity with elevation is the major challenge in the design of high reliability microwave links

Refractivity

2020-02-21T19:00:56Z

Cassieg:

The refractive index (n) of air is defined as:

n = c/v

where:
c is the velocity of light in a vacuum.
v is the velocity of light in air.
A typical value of n is 1.000301. For convenience the refractive index is expressed as refractivity (N)

N = (n-1) x 10^6

which results in a typical value of 301 Refractivity is defined by the equation:

N = 77.6 x (P/T) + 3.732 x 10^5 x (e/T^2)

where:
P is the atmospheric pressure.
T is the absolute temperature.
e is the water vapor pressure.
N varies with elevation. In a well mixed troposphere, the variation is exponential; however, in the range from 1 to 2 kilometers above sea level, the variation is approximately linear. This is referred to as a constant refractivity gradient. The refractivity gradient determines the microwave beam-bending.

Handling the variations of refractivity with elevation is the major challenge in the design of high reliability microwave links

Refractivity

2020-02-21T18:38:28Z

Cassieg: Created page with "The refractive index (n) of air is defined as: \dfrac{c}{v} = n"

The refractive index (n) of air is defined as:

\dfrac{c}{v} = n

Point to Point Microwave Link Design

2020-02-21T18:33:19Z

Cassieg:

[[Fade Mechanisms]]

[[Basic Link Design Steps]]

Basic Link Design Steps

2020-02-21T18:32:32Z

Cassieg:

# Generate the terrain profile.
# Path clearance. Determine the antenna heights required for free space line of sight. This step may fail if the heights are impractical.
# Enter the radio, antenna and transmission line specifications. The receive signal level and fade margin are avail-able at this point.
# Calculate the availability due multipath fading.
# Calculate the availability due to high intensity rain.
# Determine if path is susceptible to obstruction fading. This step may require an increase in antenna heights.
# Determine if the path geometry supports a specular reflection.
# Determine if the path is susceptible to ducting.

Basic Link Design Steps

2020-02-21T18:32:15Z

Cassieg:

# Generate the terrain profile.

# Path clearance. Determine the antenna heights required for free space line of sight. This step may fail if the heights are impractical.

# Enter the radio, antenna and transmission line specifications. The receive signal level and fade margin are avail-able at this point.

# Calculate the availability due multipath fading.

# Calculate the availability due to high intensity rain.

# Determine if path is susceptible to obstruction fading. This step may require an increase in antenna heights.

# Determine if the path geometry supports a specular reflection.

# Determine if the path is susceptible to ducting.

Basic Link Design Steps

2020-02-21T18:31:45Z

Cassieg:

Basic Link Design Steps

2020-02-21T18:30:38Z

Cassieg: Created page with "1. Generate the terrain profile. 2. Path clearance. Determine the antenna heights required for free space line of sight. This step may fail if the heights are impractical. 3. ..."

1. Generate the terrain profile.
2. Path clearance. Determine the antenna heights required for free space line of sight. This step may fail if the heights are impractical.
3. Enter the radio, antenna and transmission line specifications. The receive signal level and fade margin are avail-able at this point.
4. Calculate the availability due multipath fading.
5. Calculate the availability due to high intensity rain.
6. Determine if path is susceptible to obstruction fading. This step may require an increase in antenna heights.
7. Determine if the path geometry supports a specular reflection.
8. Determine if the path is susceptible to ducting.

Fade Mechanisms

2020-02-21T18:29:14Z

Cassieg:

Microwave fades fall into the following categories:

* Multipath fading
* Obstruction fading
* Fading due to a specular reflection
* Ducting and propagation anomalies
* Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only
depends on the change of the refractive index with height
along the path

{| class="wikitable" style="display: inline-table;"
|+
|-
! Availability
! Seconds
! Minutes
! Hours
|-
|99%
|315360
|5256
|87.6
|-
|99.9%
|31536
|525
|8.76
|-
|99.99%
|3153
|52.5
|0.876
|-
|99.999%
|315
|5.3
|0.088
|}

==Link Performance Definition==

The definition of link performance only considers multipath and rain fades.
This implies the following assumptions:

* the path has sufficient clearance / fade margin to obviate the possibility of an obstruction fade.
* signal nulls due to a specular reflection are small com-pared to the fade margin or a space diversity configura-tion has been implemented.
* the probability of ducting is unknown.

==Microwave link performance==
ANSI (North America)
All fades durations are considered i.e. the total time that the signal is below the threshold level due to rain and multi-path.
The overall link performance is expressed as an annual percentage of the link availability e.g 99.999% (315 sec-onds total outage) in both directions of transmission.

Multipath fades on a link are not correlated. The total time below level due to multipath, is the sum of the outage times in each direction.

Rain fades affect both directions of transmission equally.

Therefore, the total time below level for rain and multipath is the sum of the multipath outage time in each direction plus the outage time due to rain.

European Telecommunications Standards Institute (ETSI)

Link performance is for the worst month in one direction. Performance is divided into two categories:

* Fades which last less than 10 consecutive seconds are classed as severely errored seconds (SES).
* Fades which last longer than 10 consecutive seconds are classed as unavailability. All rain fades are considered as unavailability.

Note that Pathloss program can predict the time duration of multipath fades and separate the fades into SES and unavailability; however this is not used.
By convention multipath fades are always classed as SES.

On SDH radio systems two additional parameters are used:

* severely errored seconds ratio (SESR)
* background block error rate (BBER)

Fade Mechanisms

2020-02-21T18:28:32Z

Cassieg:

Fade Mechanisms

2020-02-21T18:26:17Z

Cassieg:

Microwave fades fall into the following categories:

* Multipath fading
* Obstruction fading
* Fading due to a specular reflection
* Ducting and propagation anomalies
* Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only
depends on the change of the refractive index with height
along the path

{| class="wikitable" style="display: inline-table;"
|+
|-
! Availability
! Seconds
! Minutes
! Hours
|-
|99%
|315360
|5256
|87.6
|-
|99.9%
|31536
|525
|8.76
|-
|99.99%
|3153
|52.5
|0.876
|-
|99.999%
|315
|5.3
|0.088
|}

==Link Performance Definition==

The definition of link performance only considers multipath and rain fades.
This implies the following assumptions:

* the path has sufficient clearance / fade margin to obviate the possibility of an obstruction fade.
* signal nulls due to a specular reflection are small com-pared to the fade margin or a space diversity configura-tion has been implemented.
* the probability of ducting is unknown.

==Microwave link performance==
ANSI (North America)
All fades durations are considered i.e. the total time that the signal is below the threshold level due to rain and multi-path.
The overall link performance is expressed as an annual percentage of the link availability e.g 99.999% (315 sec-onds total outage) in both directions of transmission.

Multipath fades on a link are not correlated. The total time below level due to multipath, is the sum of the outage times in each direction.
Rain fades affect both directions of transmission equally.
Therefore, the total time below level for rain and multipath is the sum of the multipath outage time in each direction plus the outage time due to rain.
European Telecommunications Standards Institute (ETSI)

Fade Mechanisms

2020-02-21T18:25:05Z

Cassieg:

Point to Point Microwave Link Design

2020-02-21T18:22:30Z

Cassieg: Replaced content with "Fade Mechanisms -"

[[Fade Mechanisms]] -

Point to Point Microwave Link Design

2020-02-21T18:22:01Z

Cassieg:

[[Fade Mechanisms]]

Microwave fades fall into the following categories:

* Multipath fading
* Obstruction fading
* Fading due to a specular reflection
* Ducting and propagation anomalies
* Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only
depends on the change of the refractive index with height
along the path

{| class="wikitable" style="display: inline-table;"
|+
|-
! Availability
! Seconds
! Minutes
! Hours
|-
|99%
|315360
|5256
|87.6
|-
|99.9%
|31536
|525
|8.76
|-
|99.99%
|3153
|52.5
|0.876
|-
|99.999%
|315
|5.3
|0.088
|}

Point to Point Microwave Link Design

2020-02-21T18:20:03Z

Cassieg:

==Fade Mechanisms== - http://pathloss.com/pwiki/index.php?title=Fade_Mechanisms

Microwave fades fall into the following categories:

* Multipath fading
* Obstruction fading
* Fading due to a specular reflection
* Ducting and propagation anomalies
* Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only
depends on the change of the refractive index with height
along the path

{| class="wikitable" style="display: inline-table;"
|+
|-
! Availability
! Seconds
! Minutes
! Hours
|-
|99%
|315360
|5256
|87.6
|-
|99.9%
|31536
|525
|8.76
|-
|99.99%
|3153
|52.5
|0.876
|-
|99.999%
|315
|5.3
|0.088
|}

Fade Mechanisms

2020-02-21T18:19:24Z

Cassieg:

Fade Mechanisms

2020-02-21T18:19:12Z

Cassieg: Created page with "=Fade Mechanisms= Microwave fades fall into the following categories: * Multipath fading * Obstruction fading * Fading due to a specular reflection * Ducting and propagation ..."

=Fade Mechanisms=
Microwave fades fall into the following categories:

* Multipath fading
* Obstruction fading
* Fading due to a specular reflection
* Ducting and propagation anomalies
* Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only
depends on the change of the refractive index with height
along the path

{| class="wikitable" style="display: inline-table;"
|+
|-
! Availability
! Seconds
! Minutes
! Hours
|-
|99%
|315360
|5256
|87.6
|-
|99.9%
|31536
|525
|8.76
|-
|99.99%
|3153
|52.5
|0.876
|-
|99.999%
|315
|5.3
|0.088
|}

Point to Point Microwave Link Design

2020-02-21T18:17:03Z

Cassieg:

==Fade Mechanisms==
Microwave fades fall into the following categories:

* Multipath fading
* Obstruction fading
* Fading due to a specular reflection
* Ducting and propagation anomalies
* Rain fading (above ~ 8 GHz)

With the exception of rain fading, microwave fading only
depends on the change of the refractive index with height
along the path

{| class="wikitable" style="display: inline-table;"
|+
|-
! Availability
! Seconds
! Minutes
! Hours
|-
|99%
|315360
|5256
|87.6
|-
|99.9%
|31536
|525
|8.76
|-
|99.99%
|3153
|52.5
|0.876
|-
|99.999%
|315
|5.3
|0.088
|}

Point to Point Microwave Link Design

2020-02-21T18:15:18Z

Cassieg: