Situations where the 3G network cannot carry a call due to interference or poor radio conditions - and the call needs to be carried out or completed in the 2G network - are typically caused by missing neighbors, which are cells that have not been defined in the neighbor list of the strongest cell at a given location, but which have an RxLevel good enough to be added to the UE’s neighbor list as a potential cell to hand over from 3G to 2G.
The analysis is a single defined process that integrates map visualization of neighbor relationships with reported recommendations.
The 3G-2G Missing Neighbors analysis uses scanner data for cells within a specified radius and compares the visible channels to the current neighbor list as given in the 2G cellrefs data. The results of the analysis are presented in a map and table.
Sort by Additions column to find out the recommendation of which missing neighbor sites/sectors should be added.
Before You Begin
You will need to have loaded the following:
1. A UMTS scanner stream that relates to a single UMTS frequency. Increasingly, UMTS scanners are able to scan several frequencies (identified by the UARFCN) simultaneously.
2. A GSM scanner or handset stream that was logged at the same time. If a handset stream is used, it must have been logged in idle mode.
3. These must have been loaded using a suitable matching cellrefs file, which must contain a field called GSMNeighborList on the WCDMA_Cell network element.
Using Neighbor List Analysis
1. To start this analysis, from the Summary Dashboard page, click on the
Radio Network Explorer button and click on this tab, or click on an
appropriate Important Issue in the left-hand Issues panel:
2. If you have not done so before, check the data settings that control the neighbor list analysis algorithm. In this example we will be interested in the Minimum Sample Count and the Addition Threshold. If you alter a data setting, the analysis will immediately update.
3. Sort the top table by the Additions column. You can now see the sector with the highest number of recommended additions to its neighbor list. Check that the Server Count column shows an acceptable value (you can also define a cutoff threshold using the Minimum Sample Count as shown above).
4. Click on the top row in the table to show information for that sector.
There are many additions in this example as the cellrefs file does not contain any 3G-2G neighbor definitions - therefore there are also no retentions or removals suggested.
The side panel on the left shows each recommendation for a sector individually, sorted by the % of data points that meet the recommendation algorithm. If you accept the suggestion, you can select the checkbox in the table to mark your choice.
The map now shows lines to the recommended additions. The thickness of each line shows how well the suggestion meets the criteria of the analysis. The circle represents the user-defined radius (SL_Overspill_Dist_Threshold) used by the analysis to identify potential neighbors. It also displays the data points used in the analysis Add the CPICH_Scan_EcIo_SortedBy_EcIo_0 attribute to the map.
5. Select and examine a few suggested additional neighbors. If you accept all suggestions for a sector, you can select the related checkbox in the table to mark your choice.
Note that the number beside the button changes to match your selection. For example, there were 178 suggested additions in the first row, with none currently selected for export, the number would show 0/178.
If you clicked, read 178/178. If you do not want to select every recommendation for a sector, you can use the table in the side panel on the left. So if you selected 13 additions, this would result in that number - useful if, as in this example, there are many recommendations, and you need to keep track of how many you have already selected. If you refuse to accept the suggestion, for example because there is no 3G-2G neighbor data in the cellrefs file, the sheer number of suggested additions is 51, compared with the maximum permitted number of 32. Note that the more potential neighbors you add, the longer it will take for a handset to find appropriate neighbors, conceivably resulting in a
dropped call. You may well have an upper limit already defined by your internal guidelines.
6. If you disagree with a suggested addition, you may want to use the View SC feature to find an alternative sector to add to the neighbor list. Note that in this case you will not be able to output your choice, and will need to make the correction to the switch manually (for example, by editing the CSV file).
7. Repeat this process for each row in the top table, as necessary.
8. You could now go through the same process for the 'Removals' column (this example contains no 'removals' suggestions). Note that by default the map does not show lines for removal recommendations.
9. Once you are satisfied with the recommendations that you have selected, you can output them to a CSV file. From the top of the page, click the