Missing Neighbors in WCDMA Analysis Guide
July 2004
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The content of this manual is provided for information only, is subject to change without notice, and should not be construed as a commitment by Actix. Actix assumes no responsibility or liability for any errors or inaccuracies that appear in this documentation. Copyright © Actix 2004-2008. All rights reserved. All trademarks are hereby acknowledged.
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Contents 1 INTRODUCTION .........................................................................................4 2 SETTINGS EXPLAINED .................................................................................5 3 MISSING NEIGHBORS EXAMPLE ......................................................................6 4 NEIGHBOR LIST RECOMMENDATIONS REPORT ......................................................9 5 MISSING / REMOVE NEIGHBOR ATTRIBUTES ..................................................... 10 6 DROPPED CALL ANALYSIS........................................................................... 13
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Introduction 4
1 Introduction Missing Neighbor Analysis is a fundamental aspect to WCDMA network optimization. It should be performed as part of the rollout phase of a network to construct and/or optimize the adjacency lists of each cell; and throughout the life of the network as changes to traffic and tilt affect the coverage pattern and interference interaction between the cells. Missing Neighbor Analysis in Actix Analyzer has been designed to allow engineers to generate a list of suggested Missing Neighbors and allow engineers to visualize the suggested cells on a map. Full control of the suggestion criteria is included to allow for changes in clutter, terrain and rollout phase of the network. These suggestion criteria are described as follows:
Settings inside Tools > Preferences
These criteria are applied to the scanned signal measurements to build a suggested list of cells. Only cells which satisfy all criteria are included in the fi nal list of suggested Missing Neighbors.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Settings Explained 5
2 Settings Explained Criteria
Default Value
Description
Reporting Range (dB)
5
EcIo offset applied to the Best EcIo value. EcIo values must be within this offset of the Nth_Best cell to be included as a suggested cell.
Maximum size
32
Maximum size of the suggested list. This should be set to your network infrastructure s maximum adjacency list size.
Addition Threshold (%)
1
The percentage of samples of the suggested cell relative to the Nth_Best cell must at least equal this value to be suggested. This is to reduce stray signals affecting the choice.
Removal Threshold (%)
0.2
The percentage of samples that must be achieved for a cell in the current adjacency list of the Nth_Best cell, or it will be recommended for removal.
Minimal Samples
50
The minimum number of samples of the Nth_Best cell before it s neighbors will be analyzed. This is to remove statistically invalid measurements from the suggestions.
Maximum Intersite Distance (metres)
5000
The line-of-sight distance between the Nth_Best and suggested cell must be less t han or equal to this value. Increase this value for rural areas where the average intersite distance is naturally greater than a dense-urban environment. Set this value to 0 to disable this feature.
Angle to site threshold (degrees)
90
Include existing neighbors
Disabled
This feature controls whether the criteria is applied to existing neighbors, to validate the current adjacency list of each cell according to the scanner measurements.
Only process first best SC
Enabled
By selecting this option, the adjacency list of only the Nth_Best cells will be included in the creation of the suggested list. By disabling this feature, the adjacency list of all cells that fall within the Reporting Range will also be analyzed.
The maximum criteria applied to the angle between any point in the drive route and a suggested missing neighbor. This is to ensure Missing Neighbors are not suggested from reflected signals / back-lobes, and ensure only cells angled towards the scanned drive are suggested. Set this value to 0 to disable this feature.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Missing Neighbors Example 6
3 Missing Neighbors Example The following example explains how the Missing Neighbors are calculated:
Example scanner measurement drive. SC 103 on Site 1 is the strongest signal at point “X”
In this example, at point “X”, SC 103 is the Nth_Best SC (CPICH_Scan_SC_SortedBy_EcIo_0). The closest cell to point “X” is at Site 1 1. Its adjacency list includes 101, 102, 201 and 202. At point X , the scanned list is as follows:
SC
EcIo (dBm)
103
-5
202
-6
302
-7
203
-8
402
-9
301
-9
101
-11
303
-15
1
Note: The scanner reports SC numbers, so Analyzer selects the closest cell to the drive route at that time, with a matching SC. www.actix.com
Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Missing Neighbors Example 7
•
At point “X”, the strongest signal is SC 103 is at -5dBm.
•
Applying the Reporting Range of 5dB creates a short-list of SC 202, 302, 203, 402 and 301 (greater than -10dBm). The signals from SC 101 and 303 are too weak to be considered.
•
SC 202 is are already defined as a neighbor of SC 103, so this is eliminated too, leaving us with a suggested list of 203, 302, 402 and 301.
•
Applying the intersite distance threshold, SC 402 is over 5Km away from SC 103, so it is removed from the suggested list, leaving us with SC 203, 302 and 301.
•
The angle between the point “X” and the azimuth of the SC s is now analyzed. To be considered, the azimuth must fall with +/-90 degrees of the line-of-sight vector from the point X to that site. To allow for the spread of beamwidth, half the beamwidth is added/subtracted to the azimuth to give extra tolerance of angle.
Example of angle to site threshold for sector validation
When half the beamwidth is added/subtracted (depending on w hether the azimuth is to the left or right of the vector connecting the scanner point and the cell) to the azimuth of the cell, the final criteria is applied to the cell. If the angle of the cell then falls within the angle setting in Tools > Preferences, the cell will be included in the suggested list. In the example above, SC 302 is included as a Missing Neighbor. The azimuth of SC 301 was originally outside our 90° threshold, but when subtracting half its beamwidth, it falls within our acceptable range so is therefore included as a Missing Neighbor. The azimuth of SC 203 + half its beamwidth still does not fall within our 90° threshold, so it is not included in the list.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Missing Neighbors Example 8
Our final list of Missing Neighbors is then 301 and 302. Due to the fact that SC 302 has a stronger EcIo value than SC 301 at point “X”, the Missing Neighbors at point “X” are as follows: Missing_Neighbours_0 = 302 Missing_Neighbours_1 = 301 relative to CPICH_Scan_SC_SortedBy_EcIo_0 = 103 at point “X” This is repeated for all points in the scanned drivetest route, creating an array of SCs at each point, sorted by their EcIo value, which satisfy the selection criteria and are not currently defined as a neighbor of the Nth_Best_0 cell at that time. If the “Only use Nth Best cell” option is disabled, not only the Nth_Best cell will be considered. Using the principle that if cell A and cell B are within 5dB, and cell A and cell C are within 5dB, the relationship between cell B and cell C should be analyzed too. This obviously increases that processing needed at each point, and is recommended for neighbor list optimization of more mature networks. Once the final list of suggested Missing Neighbors has been compiled, the results can be viewed in two ways: through the Accelerated Network Rollout analysis pack report (Neighbor List Recommendations), and also by visualizing them on the map/chart/table.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004 Neighbor List Recommendations report 9
4 Neighbor List Recommendations report Once this report has been run from the ANR analysis pack, the recommended additions / removals / retentions are presented in a tabular format as follows: Nth_Best SC
Site
Cell
Sample Count
Action
Nbr SC
Sample Count
%
Intersite Distance
110
Site123
Site123-a
5000
Add
200
1250
25
2.5
Retain
112
500
10
3.5
Remove
113
5
0.1
3.5
In this example, SC 110 (Site123-a) was the Nth_Best measurement for 5000 samples during the scanner measurement. Its current adjacency list includes SC 112 and 113. While SC 111 was the Nth_Best cells, there were 1250 samples of SC 200, 500 samples for SC 112 and only 5 samples for SC 113 (sorted by % samples). SC 200 is not already in the adjacency list for SC 110, all criteria have been met for this cell, so it is suggested as a Missing Neighbor. SC 112 was scanned enough times to recommend to be kept in the adjacency list. SC 113 (at the same site as SC 112, 3.5Km away from SC 110) was only scanned 5 times, so it has been recommended to be removed. NOTE: It is important to drive enough routes and collect enough data to ensure these cell suggestions are statistically valid.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004 Missing / Remove Neighbor attributes 10
5 Missing / Remove Neighbor attributes In the Workspace Explorer, you should see the grouping Neighbor Analysis, containing 2 sorted lists, for Missing Neighbor suggestions and Removal suggestions.
Workspace Explorer showing Neighbor Analysis group
The lists are sorted by signal strength and contain the SC values of the cells in the list at each point in the scanned drivetest. The strongest Missing Neighbor (Missing_Neighbour_0) should be analyzed first, as it could potentially be the strongest pollution source at that time. Drag the parameter onto the map and open the “Top 10 Scan Measurements” stateform (optionally dock it to under the Workspace Explorer). The legend of the map gives you the list of SCs that were the strongest Missing Neighbor at any point in the drive. The most frequent SC should be targeted first, and by selecting any point in the map, the stateform will synchronize to show the top 10 scanned measurements giving the Nth_Best SC at the top of the list 2. A decision needs to be made whether to add this suggested Missing Neighbor SC into the adjacency list of the Nth_Best SC.
2
In the case of repeated SC values, the closest cell with a matching SC to the Nth_Best_0 cell will be selected. www.actix.com
Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004 Missing / Remove Neighbor attributes 11
Screenshot of Nth_Best SC (CPICH_Scan_SC_SortedBy_EcIo_0) plotted on the map. Missing_Neighbours_0 is added to the map, and synchronized to the Top 10 Scan Measurements stateform. The Display Cell Data view shows the adjacency list of cell “ example0184c” (SC 242).
Once all the strongest Missing Neighbors have been analyzed, the next strongest signal should be analyzed. Following this process with ensure that the most important Missing Neighbors are analyzed first. The same SC could appear as a Missing Neighbor for multiple Nth_Best cells, so it may be easier to create a crosstab query with two dimensions: Missing_Neighbours_0 and Nth_Best_0, to give all occurrences of the combinations. This list can then be filtered from the Statistics Explorer to filter the map view for single SC combinations individually.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004 Missing / Remove Neighbor attributes 12
Screenshot showing validation of intersite distance between Nth-Best SC 242 at site Example018 4 and Missing Neighbor 202 at site Example0199. The map s distance tool has been used and the distance 1.7046Km is underlined.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Dropped Call Analysis 13
6 Dropped Call Analysis Neighbor list analysis can also be used verify the reason behind a d ropped call. This method uses the process of combining the scanner and UE together and checking the Active and Monitored Sets for the UE against the scanned measurements at the point of a dropped call.
Screenshot showing synchronized scanner and handset traces, indicating Missing Neighbor 202 (and differences between best scanned SC 242 and Active Set SC 338.
This requires the scanner and UE traces to be collected at the same time, and for the resulting collection files to be superstreamed together (and correcting any time offset between the collection devices). See t he online Help for instructions on superstreaming using Time Offsets. Once the files have been combined, parameters such as the UTRA_UE_CarrierRSSI and the Uu_CallDropped event can be dragged onto the map. By opening the “UE Missing Neighbors” stateform for the superstream and synchronizing it with dropped call, the top 10 scanned measurements can be visually compared to the Active and Monitored sets for the UE at the time.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Dropped Call Analysis 14
Screenshot showing how dropped calls from the handset can be viewed with the Missing Neighbor attributes when the scanner and handset are synchronized. Here the Active Set and Monitored Set SC s are at very low RSCP values, and poor EcNo too. The scanner detected 3 other SCs, and a missing neighbor just before the drop.
This allows the engineer to understand whether the UE had dropped a call due to a missing neighbor not being defined in the cell s adjacency list, or whether it was a handset problem, resulting in a neighbor that had already been defined not being added to the Monitored Set, and therefore never being able to be added to the Active Set.
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Actix Analyzer Missing Neighbors in WCDMA Analysis Guide July 2004
Dropped Call Analysis 15
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