Global Parameters

The global properties of a backhaul project are defined for all microwave links in the Properties of the Links folder. The global parameters are those used for:

• Quality and availability analysis

• Objective selection

To define the global parameters for link quality and availability analysis, and objective selection:

1. In the Network explorer, right-click the Links folder and select Properties from the context menu. The Links Properties dialog box appears.

2. Click the General tab. On the General tab, the parameters you define are valid for all types of analyses: quality and availability analyses, objective selection, and interference calculation.

Under Calculation parameters, you can define the following parameters:

• Median k factor: The value of the k factor (the earth curvature factor), observed 50% of time. Select the value to be used in link analyses:

• Calculated for each link: Atoll calculates the median value of the k factor according to the microwave link po-sition. Then it takes into account the calculated value for the link analysis.

• Same value for all links: If you select this option, the value you enter will be used as the k factor for all links in link analyses.

• Effective k factor: The value of the k factor (the earth curvature factor), observed 99% of time. Select the value to be used in link analyses:

Figure 4.2: Links Properties General tab

• Calculated for each link: Atoll calculates the effective value of the k factor according to the microwave link position. Then it takes into account the calculated value for the link analysis.

• Same value for all links: If you select this option, the value you enter will be used as the k factor for all links in link analyses.

• Under Power control on useful signal, you can select the output power to be considered in useful signal calcula-tions when ATPC is active. You can choose between Use the nominal power and Use the coordinated power.

These options can be defined for quality and availability analyses separately.

• Available modulations: Select if you want to display all modulations which are available for the operation mode of the selected reference radio and compatible with its channel bandwidth (Based on the operation mode) or all modulations compatible with the channel bandwidth of the selected reference radio without any additional filter on its operation mode (Based on the status with or without ACM).

Under Bit Error Rate (BER), you can define the following options:

• Use defined value for each link: If you select Use defined value for each link, Atoll performs the link analysis using the values of the BER1 and BER2 defined in the properties of each microwave link.

• Same value for all links: If you select Same value for all links, you can define a value for BER 1 and BER 2 that Atoll will use for all microwave links.

3. Click the Models tab. On the Models tab, the parameters you define will be used for quality and availability analysis.

Under Availability, you can define the following parameters:

• Method: Select the method to be used to calculate availability. Six availability analysis methods are available (Crane and those based on implemented ITU recommendations: ITU-R P.530-5, ITU-R P.530-8, ITU-R P.530-10, ITU-R P.530-11, ITU-R P.530-12, ITU-R P.530-13, ITU-R P.530-14, and ITU-R P.530-15).

• Attenuation model for rain: Select the model to be used to calculate rain attenuation. Two attenuation models for rain (ITU recommendations 838-1 and 838-3) are available.

• Attenuation model for fog: Select the model to be used to calculate fog attenuation. Two attenuation models for rain (ITU recommendations 840-3 and 840-6) are available.

Under Quality, you can define the following parameters:

Figure 4.3: Links Properties Models tab

• Method: Select the method to be used to calculate quality: Vigants-Barnett, KQ factor, ITU-R P.530-8, ITU-R P.530-10, ITU-R P.530-11, ITU-R P.530-12, ITU-R P.530-13, ITU-R P.530-14, or ITU-R P.530-15.

If you select a method based on one of the ITU-R P.530 recommendations, you can set further parameters under ITU-R P.530.

• Multi-channel frequency diversity: Define whether the number of diversity-standby channels should have an impact on the frequency improvement factor. The selected option is only considered in case of multi-channel fre-quency diversity systems when the equivalent frefre-quency factor is calculated. Select Shared if you want the equiv-alent frequency factor to be in proportion to the number of diversity-standby channels. Otherwise, select Continuous and the equivalent frequency factor will be the same for any N+M configuration (it will be equal to 1).

For more information see the Technical Reference Guide.

• ITU-R P.530: If you selected a Method under Quality based on implemented ITU recommendations (ITU-R P.530-8, ITU-R P.530-10, ITU-R P.530-11, ITU-R P.530-12, ITU-R P.530-13, ITU-R P.530-14, or ITU-R P.530-15), you can set the following parameters:

• Multi-path propagation: Under Multi-path propagation, select the Ignore Signal Enhancements check box if you want Atoll to ignore signal enhancements.

• Multipath occurrence method: If you select recommendation ITU-R P.530-10, ITU-R P.530-11, ITU-R P.530-12, ITU-R P.530-13, ITU-R P.530-14, or ITU-R P.530-15, you can use either a simplified method or a method taking roughness into account to calculate the geoclimatic factor (K).

• Selective fading: Under Selective fading you can define reference delay values for the secondary signal t (tau) for minimum and non-minimum phase conditions.

• Erroneous blocks: Under Erroneous blocks you can define the network level consideration values for the Residual Bit Error Rate (RBER), the number of errors per burst for Bit Error Rate between 10-3 and BER_SES and for Bit Error Rate between BER_SES and RBER.

• K.Q. method: If you selected "KQ factor" as the Method, under Quality, you can set the following parameter:

• Frequency exponent: Define the exponent of the frequency.

• Distance: Define the distance.

Under XPD degradation (ITU-R P.530), you can define the following parameter:

• Ignore interruptions due to the reduction of discrimination decoupling: Select the Ignore interruptions due to the reduction of discrimination decoupling check box if you want Atoll to ignore outages due to the reduc-tion of the XPD.

4. Click the Objectives tab. On the Objectives tab, you can define objective-related parameters.

• Under Performance objectives, you can define the type(s) of objective(s) to be considered for quality and availa-bility (from ITU-T G.821, ITU-T G.826, or ITU-T G.828 recommendations for the quality objectives and ITU-T G.821 or ITU-T G.826 for availability objectives, or a customised objective) and how the objectives are selected. By default, the objectives are selected according to the microwave link data rate and its length. Then, they can be selected according to the type of the objective and the defined priority. Clicking the Browse button ( ) beside the Quality or Availability box opens a dialog box where you can select the type(s) of objective(s) to be used and define their priority.

• Under Apportionment of availability objectives, you can define the ratio between the different objectives con-sidered in the global availability objective. Microwave link unavailability can be due either to rain (with its impact on propagation), to equipment failure, or it can be random. Therefore, the global availability objective consists of

Figure 4.4: Links Properties Objectives tab

three partial objectives for which you can define a weight. These weights are taken into consideration when cal-culating the performance objectives to be considered when analysing the microwave link unavailability due to rain and the unavailability due to equipment failures.

5. Click the Clutter Categories tab. On the Clutter Categories tab, the parameters you define will be used to analyse reflection and calculate vegetation losses.

This tab lists all clutter categories defined in Rec. P.1058-2 and their characteristics. For each clutter category, you can define the following parameters:

• Reflective: Select the Reflective check box if you want Atoll to consider all clutter classes with this clutter category as reflection areas.

• Vegetation with leaves: Select the Vegetation with leaves check box if you want Atoll to consider all clutter classes with this clutter category as vegetation zones with foliage.

• Vegetation without leaves: Select the Vegetation without leaves check box if you want Atoll to consider all clutter classes with this clutter category as vegetation zones without foliage.

• Soil type: Select the type of ground as defined in Rec. ITU-R P. 527-3. The type of ground is used to determine per-mittivity and conductivity values taken into account in reflection analysis. The following are the available types of ground:

• A: sea water (average salinity), 20°C

• B: wet ground

• C: fresh water, 20°C

• D: medium dry ground

• E: very dry ground

• F: pure water, 20°C

• G: ice (fresh water) 6. Click OK.

Figure 4.5: Links Properties Clutter Categories tab