Defining Parameters for a Single Microwave Link

You set the parameters that affect calculations for a microwave link on three tabs of the microwave link’s Properties dialog box: the Geoclimatic tab, the Performance tab, and the Propagation tab.

To define the parameters for a single microwave link:

1. Select the Network explorer.

2. Click the Expand button ( ) to expand the Links folder.

3. Click the Expand button ( ) to expand the Microwave Links folder.

4. Right-click the microwave link for which you want to set the parameters. The context menu appears.

5. Select Properties from the context menu. The Properties dialog box appears.

The microwave link Properties dialog box has several tabs: General, Radio, Connections, Geoclimatic, Performance, Propagation, and Display. The microwave link settings that affect calculations are on the Geoclimatic, Performance, and Propagation tabs and are described here. For an explanation of the options available on the General, Radio, Connections, and Display tabs, see "Backhaul Networks" on page 187.

6. Click the Geoclimatic tab (see Figure 4.6).

You can also access a microwave link’s Properties dialog box by right-clicking the micro-wave link on the map and selecting Properties from the context menu.

7. On the Geoclimatic tab, you can define climate-related settings affecting the microwave link:

• Common Parameters: Under Common Parameters, you can define the parameters common to all calculation methods.

• Temperature: Set the average temperature of the zone in which the microwave link operates. Clicking the but-ton ( ) beside the Temperature text box opens a dialog box where you can select the temperature based on Rec. ITU-R P.1510-0, ITU-R P.835-3 (and select a season), or the temperature set in the geoclimatic file. For more information on the geoclimatic file, see "Geoclimatic Maps" on page 113.

• Refractivity gradient: Under Refractivity gradient, you can set the following parameters:

In normal conditions: Set the refractivity gradient observed 50% of time in N-units per km. Clicking the button ( ) beside the In normal conditions text box opens a dialog box where you can select the method to esti-mate the refractivity gradient under normal conditions. The refractivity gradient can be calculated from Rec.

ITU-R P.453-9, using a user-defined reference altitude, or the refractivity gradient can be based on data given by Rec. ITU-R P.453-9 for less than 65 m. and a percentage of the year that N is not exceeded (50% is set by default), or the refractivity gradient can be set in the geoclimatic file. For more information on the geoclimatic file, see "Geoclimatic Maps" on page 113.

The k factor median value, calculated using the set parameters, is displayed.

In sub-refraction conditions: Set the refractivity gradient observed 99% of time in N-units per km. Clicking the button ( ) beside the In sub-refraction conditions text box automatically calculates the refractivity gradient under sub-refraction conditions.

The k factor effective value, calculated using the set parameters, is displayed.

• Location: Under Location, you can define the following parameters:

• For converting month/year (Rec. ITU-R P.841): Select the climatic zone used to convert annual statistics into worst-month statistics. You can choose between "Global", "Europe North West", "Europe Mediterranean",

"Europe Nordic", "Europe Alpine", "Poland", "Russian Federation", "Congo", "Canada (Prairie and North)",

"Canada (Coast and Great Lakes)", "Canada (Central and Montains)", "Indonesia" and "Japan".

• For Tropospheric losses and interference (Rec. ITU-R P.617): Select the climatic zone considered in tropo-spheric scattering attenuation and interference calculations. You can choose between "Maritim Climate",

Figure 4.6: Microwave link Properties dialog box - Geoclimatic tab

"Equatorial Climate", "Tropical Climate", "Wet Tropical Climate", "Desert Climate", "Continental Climate" and

"Oceanic Climate". Clicking the button ( ) beside the For Tropospheric losses and interference (Rec. ITU-R P.617) text box opens a dialog box where you can select the zone based on Rec. ITU-R P.617-3.

• Rainfall Rate: Under Rainfall Rate, you can define the conditions under which the microwave operates.

• Value exceeded during 0.01% of the average year (Rec. ITU-R P.530): Set the rainfall rate exceeded 0.01% of the average year (or, in other words, an amount of rainfall almost never observed). This information is used only when working with Rec. ITU-R P.530 as availability calculation method. Click the button ( ) beside the Value exceeded during 0.01% of the average year (Rec. ITU-R P.530) text box to specify whether the value is based on Rec. ITU-R P.837-4, Rec. ITU-R P.837-5 and Rec. ITU-R P.837-6, or the value set in the geoclimatic file.

For more information on the geoclimatic file, see "Geoclimatic Maps" on page 113.

• Rain zone (Crane method): Select the rain zone in which the microwave link operates. This information is used only when working with Crane as availability calculation method. You can select the following rain zones: "A",

"B", "B1", "B2", "C", "D1", "D2", "D3", "E", "F", "G" and "H".

• Atmospheric Conditions (Rec. ITU-R P.530): Under Atmospheric Conditions (Rec. ITU-R P.530), you can define the conditions under which the microwave operates. These parameters are used by ITU-R P.530 to calculate the quality of the microwave link.

• Water vapour density: Set the water vapour density in grams per cubic metre. Clicking the button ( ) beside the Water vapour density text box opens a dialog box where you can select the water vapour density based on Rec. ITU-R P.836-3 (and select the percentage of the average year where the defined water vapour density is exceeded), or based on Rec. ITU-R P.835-3 (and select a season), or the water vapour density set in the ge-oclimatic file. For more information on the gege-oclimatic file, see "Gege-oclimatic Maps" on page 113. The dialog box also displays the water vapour pressure in hectopascals (hPa) calculated using your data and based on Rec.

ITU-R P.453-9.

• Atmospheric pressure: Set the atmospheric pressure in hectopascal (hPa). Click the button ( ) beside the Atmospheric pressure box to specify whether the atmospheric pressure is based on Rec. ITU-R P.835-3 (and select a season), or the value set in the geoclimatic file. For more information on the geoclimatic file, see

"Geoclimatic Maps" on page 113.

• Relative humidity: The Relative humidity displayed is calculated using the defined water vapour density.

• Rain height (0°C/32°F Isotherm): You can enter the Rain height (0°C/32°F Isotherm) in metres. The rain height is the height of the top of the rain column above mean sea level from the 0°C isotherm. Click the button ( ) beside the Rain height box to specify whether the value is based on Rec. ITU-R P.839-3, or the value set in the geoclimatic file. For more information on the geoclimatic file, see "Geoclimatic Maps" on page 113.

• Geoclimatic factor: The parameters under Geoclimatic factor are used to calculate the quality of the microwave link and are broken down by calculation method. You can set the following parameters:

• ITU-R P.530-5, -8: Under ITU-R P.530-5, -8, you can select the Environment. You can choose between "Open areas" for terrestrial microwave links where the height of the lowest antenna in the microwave link is lower than 700 m; "Mountains" for terrestrial microwave links where the height of the lowest antenna in the micro-wave link is higher than 700 m; "Lakes" for micromicro-wave links over an expanse of water; or "Overwater" for mi-crowave links over an extended expanse of water. Finally, you can define the PL factor. PL is the percent of time the relative refractivity gradient is less than -100 N⁄Km. The PL factor can be found on the ITU-R maps.

• Rec. ITU-R P.530: Under ITU-R P.530, you can define the K factor. K models geoclimatic and terrain effects on climate. Clicking the button ( ) beside the K box opens a dialog box where you can select the K factor based on Rec. ITU-R P. 530-5 or Rec. ITU-R P. 530-8 (and select a terrain type and enter a value for C0 and for the percentage of time the refractivity gradient (< 100 m.) is less than -100 N-units⁄km for the worst average month) or based on Rec. ITU-R P. 530-10 and above (and select the simplified method where you also define the refractivity gradient (< 65 m.) not exceeded during 1% of the average year or select the method with terrain roughness taken into account where you define the refractivity gradient and the terrain roughness).

• Vigants-Barnett: Parameters available under Vigants-Barnett are used with Vigants-Barnett method only.

Climate zone: Select the climatic zone that best describes the climate in which the microwave link operates.

You can choose between "Warm and Humid", "Temperate", "Dry", "Great Lakes Areas", "Gulf Coasts", "Ha-waii-Caribbean", "Alaska Coasts", and "Alaska Inland".

Terrain type: Select <Auto> to consider terrain roughness of the link in the Terrain-climate factor C calculation or the terrain type that best describes the terrain in which the microwave link operates. You can choose be-tween "Flat Terrain", "Average Terrain", "Great Lakes", "Gulf Coasts", "Islands", "Alaska Mountain", or "Tun-dra Zones".

Changing the terrain type automatically updates the climate zone and vice-versa.

Terrain-climate factor C: The propagation condition factor for the Vigants-Barnett method. You can define the value or let Atoll calculate the Terrain-climate factor C value based on the defined Climate zone and Terrain type. When <Auto> mode is selected as Terrain type, Atoll calculates the Terrain-climate factor C based on the terrain roughness of the link which depends on its profile. Clicking the button ( ) beside the

Terrain-climate factor C box opens a dialog box to specify whether the value is based on the roughness of the selected terrain type or on a user-defined roughness value.

• K.Q. method: Under K.Q. method, you can define K.Q. for the K.Q method. K models geoclimatic and terrain effects on climate while Q is the factor for variables other than those dependent on distance and frequency.

8. Click the Performance tab (see Figure 4.7).

9. On the Performance tab, you can define performance-related parameters:

• Link class: Under Link class, you can select the TDM and IP link classes.. Each link class can have different perfor-mance objectives. By assigning link classes to microwave links, you are assigning the target parameters and usage limitations of the link class to the selected microwave links. For information on creating a link class, see "Defining Link Classes" on page 272.

Clicking the Browse button ( ) opens the Properties dialog box of the selected link class.

The Quality Objectives and Availability Objectives tabs provide tables where you can view the selected perfor-mance objectives (SESR, ESR, BBER, RXLEV, MARG, IPER) for the specified link class. For SESR, ESR, and BBER pa-rameters, Atoll displays the cutoff probability, the annual and monthly cutoff duration as well as the non-cutoff percentage.

• BER: Under BER, you can set the values for BER 1 and BER 2. Atoll displays the resulting sensitivity for each BER.

If the value for BER that you enter is not defined in the properties of the equipment, Atoll will interpolate to de-termine the corresponding sensitivity.

By default, only the ground altitude is used to evaluate terrain roughness. You can config-ure Atoll to consider both the ground altitude and the clutter height in roughness calcula-tion by editing the Atoll.ini configuracalcula-tion file. For more informacalcula-tion about editing the configuration file, see the Administrator Manual.

Figure 4.7: Microwave link Properties dialog box - Performance tab

• Reliability: Under Reliability, you can set the Mean time to repair (MTTR) in hour. The MTTR is taken into account when calculating unavailability due to failures if the microwave link is not equipped with a hot standby channel system.

10. Click the Propagation tab (see Figure 4.8).

11. On the Propagation tab, you can define propagation-related parameters:

• Useful signal: Under Useful signal, you can select the propagation model that will be used to calculate the useful signal. From this parameter, Atoll evaluates the margin which is then considered for calculating the quality and the availability of the microwave link.

• Interfering signal: Under Interfering signal, you can select the propagation model that will be used to calculate signal level received from interfering sites.

12. Click OK.