The General tab contains information about the coverage predictions being compared, including their names and resolutions.
4. Click the Display tab. On the display tab, you can choose how you want the results of the comparison to be dis-played. You can choose among:
- Intersection - Union - Difference
In order to see what changes adding a new base station made, you should choose Difference.
5. Click OK to create the comparison. The comparison in Figure 0.24, shows clearly the area covered only by the new base station.
Figure 0.23: Signal level coverage prediction of network with new base station
Example 2: Studying the Effect of a Change in Transmitter Tilt
If you have an area in a network that is poorly covered by current transmitters, you have several options for increasing coverage. In this example, we will look at how modifying transmitter tilt can improve coverage.
A coverage prediction by transmitter of the current network is made as described in "Making a Coverage Prediction by Transmitter" on page 26. The results are displayed in Figure 0.25. The coverage prediction shows that one transmitter is covering its area poorly. The area is indicated with a red oval in the figure.
You can try modifying the tilt on the transmitter to improve the coverage. The properties of the transmitter can be accessed by right-clicking the transmitter in the map window and selecting Properties from the context menu. The mechanical and electrical tilt of the antenna are defined on the Transmitter tab of the Properties dialogue.
Once the tilt of the antenna has been modified, the original coverage prediction can be recalculated, but then it would be impossible to compare the results. Instead, the original coverage prediction can be copied by selecting Duplicate from its context menu. The copy is then calculated, to show how modifying the antenna tilt has affected coverage (see Figure 0.26).
Figure 0.24: Comparison of both signal level coverage predictions
Figure 0.25: Coverage prediction by transmitter of existing network
As you can see, modifying the antenna tilt increased the coverage of the transmitter. However, to see exactly the change in coverage, you can compare the two predictions.
To compare two predictions:
1. Right-click one of the two predictions. The context menu appears.
2. From the context menu, select Compare with and, from the menu that opens, select the prediction you want to compare with the first. The Comparison Properties dialogue appears.
3. Click the General tab. You can change the Name of the comparison and add Comments.
The General tab contains information about the coverage predictions being compared, including their names and resolutions.
4. Click the Display tab. On the display tab, you can choose how you want the results of the comparison to be dis-played. You can choose among:
- Intersection - Union - Difference
In order to see what changes modifying the antenna tilt made, you can choose Union. This will display all pixels covered by both predictions in one colour and all pixels covered by only one prediction in another colour. The increase in coverage, seen in only the second coverage prediction, will be immediately clear.
5. Click OK to create the comparison. The comparison in Figure 0.27, shows clearly the increase in coverage due at the change in antenna tilt.
0.2.8.8 LTE Coverage Predictions
Two types of LTE coverage predictions are available in Atoll: coverage predictions used to analyse signal quality, and coverage predictions used to analyse the network response to traffic.
Signal quality coverage predictions can be used to analyse the reference signals in the downlink, as well as uplink signals.
These coverage predictions do not depend on the network load conditions.
Figure 0.26: Coverage prediction by transmitter of network after modifications
Figure 0.27: Comparison of both transmitter coverage predictions
You can study the network behaviour under traffic conditions by making coverage predictions used to analyse the network response to traffic. Using these coverage predictions you can study the effective service coverage area and capacity of each cell in the network. These coverage predictions depend on the interference in the network and the cell load condi-tions. For this reason, the network load must be defined in order to calculate these coverage prediccondi-tions.
For the purposes of these coverage predictions, each pixel is considered a non-interfering user with a defined service, mobility type, and terminal. The following are explained in the following sections:
• "Service and User Modelling" on page 37.
This section explains the coverage predictions available for analysing signal quality and for analysing the network response to traffic. The following coverage prediction is explained:
• "Analysing the Signal Quality" on page 39.
• "Analysing the Network Response to Traffic" on page 40.
0.2.8.8.1 Service and User Modelling
Atoll can base LTE coverage predictions on the DL traffic loads and the UL noise rise values entered in the Cells table (for more information, see "Setting the Traffic Loads and the UL Noise Rise" on page 41). Before you can model services, you must define LTE radio bearers. For more information on LTE radio bearers, see "Defining LTE Radio Bearers" on page 77.
In this section, the following are explained:
• "Modelling Services" on page 37.
• "Modelling Mobility Types" on page 38.
• "Modelling Terminals" on page 38.
Modelling Services
Services are the various services available to users. These services can be either voice or data type services. This section explains how to create a service. The following parameters are used in predictions:
• Throughput scaling factor
• Throughput offset
• Body loss
To create or modify a service:
1. Click the Data tab of the Explorer window.