Composite D/U Studies
Q: How can I show coverage of one “desired” signal as affected by one or more “undesired” signals?
A: With TAP6.0.2365 or later, including the Aggregate Coverage module, and a Maintenance Subscription date of December 31, 2010, or later, you can compute coverage based on a specified D/U ratio value.
With TAP6.0.2367 or later, including the Aggregate Coverage module, and a Maintenance Subscription date of January 31, 2011, or later, you can also include a desired signal receiver antenna pattern to be used at each of the remote locations for the D/U study.
Note that all values in this example are for demonstration purposes only. You should determine appropriate settings for your application.
The “Composite” function in the TAP Aggregate Coverage module is used for combining the results of two or more coverage studies computed in TAP.
Launch the Composite Calculation function from the “Area” menu in TAP:
The TAP Composite Study form is displayed. Click the “Create a new study” button:
A new Task is created and a Task ID is assigned by the program. Enter a Task Description for this study:
In the “Studies to Include” section, select the TAP Area Coverage studies you have already computed and that you want to include in this D/U study. The studies should be the one “Desired” signal you are interested in, as well as all potential “Undesired” signals you want to consider:
In the “Composite Area” section, define the area you want for the study. Typically you may want to click the “Get Limits from studies” button which will determine the boundary area that includes all the studies you have selected. Other ways of selecting the area are described in Composite Study Methods.
In the “Composite Operation” section, use the pull-down list to select the “D/U Ratio” as the function to use on the selected coverage studies:
Enter the minimum field strength required for operation of the desired signal. The Minimum Field value will be used to evaluate each location in the Composite Area to be computed. Locations where the desired signal is below this value will be marked as having no service.
Note that you can also double-click the Minimum Field value to open the Mobile Facility database and select a record from that database. Selecting a Mobile Facility will insert the Required Field value for that record into the Minimum Field value for the study.
Enter the Desired to Undesired signal ratio (D/U, in dB) for the study. The D/U value will be used to evaluate each location in the Composite Area to be computed. Locations where the desired signal is above the Minimum Field, but where any of the other (undesired) signals do not meet this specification will me marked as “Spec not met” indicating no service at those locations.
Note that the D/U Ratio can be negative.
Where D – U ≥ D/U the coverage will show service from the
D signal
Where D – U < D/U the coverage will show no service from the
D signal
Unlike the TAP Composite Study “Best Server” study, the coverage will not show service by any of the U signals.
Use the “Task D” pulldown list to select which of the “Studies to include” will be considered the Desired signal. All other studies selected in the “Studies to include” list will be treated as Undesired signals.
Click the Save button to save the study.
Click the Run button to start the study:
A list of available studies to run will be displayed. Any studies you have edited during the current session will be marked to run. You can add or remove check-marks for studies in the list. Click the Continue button to start the execution of the marked studies:
When the study is completed (if the AutoDraw box was checked when you set up the study) the coverage map will be displayed in HDMapper:
You can zoom in to specific areas to see locations where the Desired signal was below the required minimum threshold, locations where the Undesired signal will prevent reception of the Desired signal, and locations where the required D/U ratio is exceeded and the Desired signal is available.
With TAP6.0.2367 or later, including the Aggregate Coverage module, and a Maintenance Subscription date of January 31, 2011, or later, you can also include an desired signal receiver antenna pattern to be used at each of the remote locations for the D/U study.
This feature enables you to model the following scenario. The receiver for the Desired signal at each remote location is assumed to have a directional antenna with the major lobe aimed at the Desired signal transmitter. The gain and elevation of the antenna are set as usual in the "Mobile Facility" in the HDCoverage program when the study is setup. The antenna pattern is used in this Composite function for a D/U study to model the isolation provided by the directionality of the remote antenna at each location. Since the remote antenna is assumed to be correctly oriented (azimuth and elevation angle) to the desired signal transmitter, the value of the desired signal will be unaffected. However, in the majority of instances where the direction from the remote location to the Undesired signal source will be off the major lobe of the antenna, the isolation provided by the antenna pattern can be included in the D/U ratio calculation.
To add an antenna pattern to use at the remote locations, set up the D/U study as described above. In the Composite Operation section of the TAP6 Composite Study form, click the lookup button ("...") for the Remote Receiver Antenna Pattern:
Select the TAP Antenna Library you want to use:
When the list of antennas in that library is displayed, select the antenna you want to use and click the Close button:
The description for the selected antenna will be displayed on the Composite Study form:
If you want to remove the antenna pattern, click the "X" button on the form. The result will be that the Composite Study will be performed as if all remote or mobile receivers use omni-directional antennas with identical characteristics for the desired and undesired signals.
Note that no orientation or tilt values are specified. The antenna orientation and tilt are determined at each remote location with the assumption that the antenna is aligned correctly toward the desired source.
When you run the study, the results will reflect the antenna pattern effects:
For example, note the reduced areas of interference ("Spec Not Met") when the remote antenna isolation factor is considered:
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