Radial except when
using SPM Systematic Method used for coverage studies: radial except when using SPM
Result
One value inside a calculation binDifferent values inside a
calculation bin One value inside a calculation bin
a. When using SPM, you can choose either radial or systematic calculation option.
Notes:
• In coverage studies, Atoll calculates path loss for every bin within calculation areas.
However, only results on calculation bins inside the computation zone are displayed.
• Profile point analysis is calculated in real time. Therefore, prediction is always consistent with the network. On the other hand, if you modify any parameter (radio or geo), which may make matrices invalid, consider updating the matrices before using point analysis based on path loss matrices.
• Due to different calculation methods, you can get different results at a same point when performing a point analysis in profile or reception mode.
Notes:
• In any project, Atoll considers that the receiver antenna is in the transmitter antenna axis.
Therefore, the receiver antenna attenuation is supposed to be zero.
• Transmitter antenna attenuation may not be considered in this step. It depends on propagation model provider, who may choose to include this parameter in calculation. However, all the propagation models available in Atoll calculate by considering transmitter antenna attenuation.
3rd step: Then, Atoll determines the prediction criterion and displays coverage.
For a signal level study,
The signal level at the receiver ( ) is calculated. We have (in dBm):
Where
is the effective isotropic radiated power of the transmitter.
is the transmitter power.
is the transmitter antenna gain.
are transmitter losses.
is the shadowing margin.
are the indoor losses, taken into account when the option “Indoor coverage” is selected, are receiver losses.
is the receiver antenna gain.
The prediction is performed for a user-defined cell edge coverage probability (x%). This means that the measured criterion exceeds the predicted criterion for x% of time. The prediction is reliable during x% of time.
4.2 Path Loss Matrices
Atoll is able to calculate two path loss matrices per transmitter, a first matrix over a smaller radius computed with a high resolution and a propagation model (main matrix), and a second matrix over a larger radius computed with a low resolution and another propagation model (extended matrix).
To be considered for calculations, a transmitter must fulfil the following conditions:
• It must be active,
• It must satisfy filter criteria defined in the Transmitters folder, and
• It must have a calculation area.
In the rest of the document, a transmitter fulfilling the conditions detailed above will be called TBC transmitter.
The path loss matrix size of a TBC transmitter depends on its calculation area. Atoll determines a path loss value ( ) on each calculation bin (calculation bin is defined by the resolution) of the calculation area of the TBC transmitter. You may have one or two path loss matrices per TBC transmitter.
Note:
• For a cell edge coverage probability of 50%, the shadowing margin is always zero. In this case, Atoll still works as above.
Notes:
• In UMTS and CDMA documents, and .
• In UMTS and CDMA documents, Atoll considers that and equal zero when calculating the received signal level (in point analysis, Profile and Reception tabs, and in common coverage studies such as Coverage per transmitter, Coverage by field level, Overlapping).
• In GSM_EGPRS documents, .
• In GSM_EGPRS documents, receiver is equipped with an antenna with zero gain.
Note:
• In case of interference studies, only signal from interfered transmitter (C) is downgraded by the shadowing margin. We consider that interference value (I) is not altered by the shadowing margin.
4.2.1 Calculation Area Determination
4.2.1.1 Computation Zone
Transmitter calculation area is made of a rectangle or a square depending on transmitter calculation radius and the computation zone.
Calculation radius enables Atoll to define a square around the transmitter. One side of the square equals twice the entered calculation radius.
Since the computation zone can be made of one or several polygons, transmitter calculation area corresponds to the intersection area between its calculation square and the rectangle containing the computation zone area(s).
4.2.2 Calculate / Force Calculation Comparison
4.2.2.1 Calculate
The Calculate feature (F7) enables you:
1. To calculate prediction studies
The first time you click Calculate (no path loss matrices exist), Atoll computes path loss matrices for each TBC transmitter. Then, it calculates created and unlocked coverage prediction studies inside the computation zone.
2. To check result validity and update calculations
If calculations have been performed once and you have changed some parameters such as radio data or calculation area, Atoll automatically detects path loss matrices to be recalculated. These are either one or several path loss matrices that become invalid due to certain modifications. Then Atoll calculates the prediction study, or just the prediction study if matrices were all still valid.
Figure 4.1Example 1: Single Calculation Area
Figure 4.2Example 2: Multiple Calculation Areas Computation zone(s)
Rectangle containing the computation zone(s) Calculation area defined (square)
Transmitter
Calculation area: real area for which Atoll calculates path losses
4.2.2.2 Force Calculation
With the Force calculation feature (Ctrl+F7), Atoll deletes all the path loss matrices even if they are valid, recalculates them and then updates the results of prediction studies.
4.2.3 Matrix Validity
Atoll manages path loss matrix validity transmitter by transmitter, even in case of transmitters with two path loss matrices (main and extended matrices). Therefore, even if only one path loss matrix of the transmitter is invalid, Atoll will recalculate both of them. All the geographic data modifications and some radio data changes can make matrices invalid. This table lists these modifications and also changes that have an impact only on prediction studies.
Note:
• Geographic data (DTM, clutter) modification makes path loss matrices invalid. However, Atoll does not detect this invalidity just by using Calculate. Therefore, to update