GSM CELL COVERAGE ANALYSIS - Actix Spotlight Desktop User Guide

You can use this analysis to:



Determine the coverage footprint for each cell.



Visualize where a cell is the best server.



Determine the relative grade of service as regards to EcIo, Mobile Rx Power and Mobile TX Power for selected cell(s), based on a user-defined threshold.



Visualize where cells are overshooting their coverage design boundary as defined by SL_Overspill_Dist_Threshold (drawn as a red circle on the map).



Visualize the neighbor BCCH, TCH and BSIC plans, within the range G_Interference_Radius (drawn as a dotted blue circle on the map).

7.6.1 Before you start

You can use scanner or handset data for this analysis.

7.6.2 Example of No Dominance

The Summary Dashboard shows an Important Issue: '% area with No Serving Cell Dominance'. See Coverage criteria to see how this was derived.

1 From the Summary Dashboard, click on an appropriate 'issue' link to open the Cell Coverage analysis page, for example the issue shown above. 2 Note that several rows in the top table have a low sample count, '#', and

2 3 To remove rows with low sample counts, apply a Filter with a threshold

of, say, 50 counts. Click Add Filter and OK.

4 From the Attribute drop-down menu, select an attribute to plot on the map, base on the related Important Issue from the Summary Dashboard (for this example, No Serving Cell Dominance):

Important Issue Attribute Poor Voice Quality ServRxQualSub Poor Signal Strength ServRxLevSub

No Serving Cell Dominance NumNeighbors within 5 dB

The attribute is used in the calculation to identify the issue, as explained in Coverage criteria.

Note that drive test data is binned according to the selections made in step 4 of defining the project template. However, any events displayed on the map (for example, by using the Events drop-down menu) will use the exact position rather than a binned position, so events might not align with the data points.

2 5 Examine the top table of the analysis for indications of poorly performing

cells relating to the Important Issue, and select likely candidate rows. In the example below, a problem row has been selected. The first map image shows the 'NumNeighbors within 5 dB' attribute plotted, which highlights an area of poor dominance (drawn in red). The second map image shows RxLev (Where Seen) plotted for the same sector, which shows that it covers an unnecessarily large area. This could be corrected by applying some downtilt to the sector.

7.6.3 Example of GSM visualization

This analysis can also be used to highlight and investigate interference issues, based on the information held in the cellrefs file. In this example, the Quality tab of the side panel shows a high percentage of Poor RxQual at the same time as Good RxLev, which is usually an indicator of interference.

1 Use the top table to locate and select cells exhibiting this combination of poor RxQual and good RxLev.

2 Now from the side panel, select the Visualization tab.

Depending on the information available, up to four radio buttons are displayed at the top of the panel with which you can pick the required type of cell plan visualization.

If you have interference, you may need to see if there are any cells in the area that have the same frequencies. On the map you can see the

selected sector in gray, together with colored co-channel, adjacent lower and adjacent higher interference sectors. The cell coverage radius is shown as a red circle, and the cell plan visualization radius is shown as a dotted blue circle.

If TCH information is present in the cellrefs file, radio buttons will be displayed for the two TCH display options, and TCHList information will appear in the pop-up sector information.

7.6.4 Features of this analysis page



Map - When you click a row in the top table or on a site on the map, the

map shows the coverage wedge for the selected cell, EcIo & RSCP. The red circle represents the user-configured coverage design boundary, and data points outside this circle represent overspill.



Analysis – The page can operate in two analysis modes: Best Server and

Where Seen. Best Server mode shows the Ec/Io attribute when the selected cell was the best server (and also RxQual). The Where Seen mode shows RxLev whenever the cell was measured; coverage footprints can only be seen for those cells that were best servers at least once during the drive.



SC Search – Visualize a SC on the map. Input a SC to visualize on the map

and this feature would color red all the sites with this SC. This quickly identifies co-SC locations.



Filters – Select this link to specify filters for the table on the top panel.



Events – Lists the event attributes that can be plotted on the map.

Currently plotted events are shown in red in the list.



Attributes – Lists the most commonly used attributes that can be plotted

on the map. Currently plotted attributes are shown in red in the list. The currently selected attributes will be kept as you move between Spotlight's analysis pages.



Top Panel - Shows a table of summary information. Clicking on a row in

this table causes the side panel to display more information about the site and the map zooms to the site and displays its coverage. The table

containing the following information:

▫ Handset (Where Seen / Best Server)

BCCH

# - Number of samples. Ensure that the site you are looking at has a statistically viable number of samples.

> D(ist.) - Number of samples greater than the coverage design boundary (defined by SL_Overspill_Dist_Threshold).

RxQual, RxLev, (Average, Max, Min). Note that clicking on the icon only displays the Average value.

% > Beam – Percentage of points outside the cell beamwidth. % >180 Beam – Percentage of points outside a hypothetical beamwidth of 180 degrees.

Link Diff – This is the difference between UL and DL pathloss and is used to highlight cell with possible LNA (TMA) issues, if the

difference is greater the 8 dB, where:

2 Poor Ql, Poor Lv and No Dom - see Coverage criteria below for

details.

▫ Scanner (Where Seen / Best Server)

As Handset but no RxQual or Link Diff information in the top table.



Side Panel - Each tab displays various KPIs for the selected site. Note that

if you have the Visualization tab selected and you select a sector not included in the visualization, you will lose the other tabs, and will need to click on a row in the top table to show them again.

▫ Quality tab - (Handset data only) Shows the percentage of Good

and Poor RxQual and RxLev in the data (see Coverage criteria for details).



Distance tab - Displays a histogram of the distances at which the cell was

measured. A red line at the top indicates the maximum range for the analysis (equating to the red circle on the map), as defined by

SL_Overspill_Dist_Threshold (changeable from the Tools, Display Thresholds command). Note that the side panel only shows Best Server data, so if you set the Analysis (see below) to 'Where Seen', the map will only show Where Seen data, so there may appear to be a discrepancy between the two views.



Visualization tab - Displays BCCH, TCH (if available in the cellrefs file) and

Co BSIC co- and adjacent channel interference on the map by coloring in the interfering sectors, out to a distance defined by the threshold

G_Interference_Radius (which can be changed using the Tools, Display Thresholds command). See also the previous worked example of GSM visualization.

Note that the color is determined by the first satisfied condition, in the following order: BCCH co-interference, TCH co-interference, BCCH

adjacent upper, BCCH adjacent lower, TCH adjacent upper, TCH adjacent lower.

2 %Intrf or %Interference in the visualization table is the ratio between the

number of interfering channels in common and the sum of all the channels on the cell. So in the BCCH example below, there is 1 BCCH channel and 3 TCH channels used by the sector. Each row shows only one interfering BCCH channel, and so the %Intrf is 100% x 1/4 = 25%.

In the TCH example below, there is 1 BCCH channel and 3 TCH channels used by the sector. Each row shows three interfering TCH channels, and so the %Intrf is 100% x 3/4 = 75%.

2 TCH Co/adjacent Channel % is shown below. This type of

visualization is inappropriate for frequency hopping - that is, where baseband or synthesized traffic channels are being used.

Co BSIC visualization is shown below. This is used to distinguish between two different cells which are on the same BCCH. Orange sectors show that there is another cell on the same BSIC (co BSIC channel interference), and red sectors show that the cell also has the same BCCH.

7.6.5 Coverage criteria

Condition Top table column

or Quality tab* Criteria

Poor Voice Quality Poor Quality, Poor Ql ServRxQualSub <

G_RxQualSub_Max threshold Poor Signal

Strength

Poor Leverl, Poor Lv ServRxLevSub <

G_RxLevSub_Min threshold No Serving Cell

Dominance No Dom If the sum of all these conditions is > 2: ((ServRxLevSub-

NborRxLev[n])<5) * (abs(ServBCCH-

NborBCCH[n])<375), where n is 0 to 5.

Good Design G. Design % Where none of the above conditions is true.

*This is the percentage of data points where one (or more than one) condition applies.

In document Actix Spotlight Desktop User Guide (Page 65-75)