Huawei Owj102103 Wcdma Rno Rf Optimization Issue1.1

Course OWJ102103

WCDMA RNO RF Optimization

ISSUE 1.1

OWJ102103 WCDMA RNO RF Optimization ISSUE 1.1 Table of Contents

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Table of Contents

Introduction....................................................................................................................................... 1 Chapter 1 RF Optimization Overview ............................................................................................. 2

1.1 Clusters ................................................................................................................................. 2 1.2 Drive Routes ......................................................................................................................... 2 1.3 Tools...................................................................................................................................... 2 1.4 Optimization Targets ............................................................................................................. 2 1.5 Optimization Solutions .......................................................................................................... 3 1.6 Overall Process..................................................................................................................... 3

Chapter 2 RF Analysis Approach.................................................................................................... 5 2.1 Cell Dominance..................................................................................................................... 5 2.2 CPICH Coverage (RSCP) ..................................................................................................... 6 2.3 Interference (CPICH Ec/Io) ................................................................................................... 7 2.4 Uplink Coverage.................................................................................................................... 8 2.5 Pilot Pollution ........................................................................................................................ 9 2.6 Estimated Active Set Size ................................................................................................... 10 2.7 Neighbor List verification..................................................................................................... 11 2.8 UE SHO Performance......................................................................................................... 12 2.9 Drop Calls............................................................................................................................ 12

Summary.......................................................................................................................................... 15

OWJ102103 WCDMA RNO RF Optimization ISSUE 1.1 List of Tables


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List of Tables

Table 1-1 Optimization Suggest Targets ....................................................................................2

Table 2-1 Pilot pollution results ................................................................................................10

Table 2-2 Example output of the Neighbor list verification.......................................................12

Table 2-3 Soft handover success rate......................................................................................12

OWJ102103 WCDMA RNO RF Optimization ISSUE 1.1 Introduction


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Introduction

This document provides a detailed discussion of the RF (Cluster) optimization phase of the 3G radio network.

It is expected that all integrated sites will undergo the Single Site Verification process. The objectives of the single site verification are to ensure there is no installation or parameters related faults with any of the sites.

Once all the sites in a given area are integrated and verified, RF (or Cluster) optimization could begin. This refers to the main phase of optimization which aims at optimizing coverage while in the same time keeping interference and pilot pollution under control over the target area.

This document presents a step-by-step approach for the analysis of drive survey data that collected using Agilent Scanner and test UE. The analysis is being done using Actix Analyzer.

It should be emphasized that the RF optimization will be an ongoing activity and will need to be revisited as traffic increases in the network and as new sites are deployed.

In addition, as the network matures, the optimization process should take into account statistical data and key performance indicators collected throughout the network.

In this document, sample data from one part of the network is used to illustrate the various analysis techniques. Although this data is from an incomplete cluster of sites, it is sufficient for the purpose of this document.

The layout of this document is as follows: Section 2 provides an overview of the RF optimization process while section 3 outlines the analysis steps need to identify various RF issues. A summary of the analysis is provided in section 4. The appendixes at the end of the document contain various Actix related configuration data that should be used when performing data analysis to ensure consistency throughout the network.

OWJ102103 WCDMA RNO RF Optimization ISSUE 1.1 Chapter 1 RF Optimization Overview


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Chapter 1 RF Optimization Overview

1.1 Clusters

Due to the nature of UMTS (i.e. the inter-dependence of coverage and capacity and the frequency reuse factor of one), it is crucial that the RF optimization is carried out for groups or clusters of sites rather than on single site basis. This will ensure that the impact of all the sites in a given area on coverage as well as interference is taken into account.

Prior to any changes to a specific site, detailed analysis of the impact of such change on the adjacent sites must be considered to ensure there could be no adverse effects on the area.

1.2 Drive Routes

The cluster drive surveys should include the coverage areas of each cell and all the major roads and streets as well as any other important locations.

It is essential to use identical drive routes prior and post any optimization changes in order to accurately quantify the impact of such changes.

1.3 Tools

The drive surveys should be conducted using the Agilent scanner and Test UE in continuous AMR call or Video Phone call.

The use of the UE data is important to the RF optimization as it provides additional information that could help identify certain issues, such as: Uplink coverage problems, missing neighbors, too many soft handover events, etc.

The scanner will be using an externally mounted antenna while the UE will be kept inside the car in the same location for each drive test.

For post-processing the data, Actix Analyzer will be used as outlined in this document. For consistency, Actix should be configured as outlined in Appendixes A-D of this document.

1.4 Optimization Targets

The targets and thresholds in Table 1-1below are for use in the early phase of network optimization and are applicable to the scanner measurements unless otherwise stated.

For description of terms such as pilot pollution, please refer to the next section.

Table 1-1 Optimization Suggest Targets

Item Requirements Comments Target - 85 dBm CPICH RSCP Minimum -95 dBm

Corresponds to outdoor measurements.



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Item Requirements Comments Target -8 dB CPICH Ec/Io Minimum - 14 dB

Applicable for unloaded network.

Active Set size (estimated) Target 3 Based on scanner data.

Max % < 10 % % of time a cell is seen as a pilot polluter. Pilot pollution Threshold 8 dB Relative to best server when cell in not in Active Set.

UE Tx power Max 95 % For e1a, e1b & e1c

1.5 Optimization Solutions

Most of the coverage and interference issues could be resolved through adjusting sites parameters, such as (in order of priority): z Antenna tilt z Antenna azimuth z Antenna location z Antenna height z Antenna type z Site location z New site Detailed discussion of the different optimization problems and solutions is provided in section 5.

1.6 Overall Process

The high-level Cluster process is depicted in Figure 1-1below. As can be seen, the process can be quite iterative and therefore careful analysis is required to ensure the optimum solution is achieved with the minimum number of iterations.



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Figure 1-1 High level RF optimization steps

OWJ102103 WCDMA RNO RF Optimization ISSUE 1.1 Chapter 2 RF Analysis Approach


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Chapter 2 RF Analysis Approach

This section presents various plots that produced using Actix along with a description of the analysis approach.

It should be noted that the effect of an RF problem will typically be seen in a number of these plots and therefore a summary of the analysis is needed to conclude on the fundamental causes of any failures. This summary will be provided in the next section.

During the analysis of the individual plots, any observed issues should be marked to facilitate further investigations and comparisons with other plots.

2.1 Cell Dominance

One of the first plots that should be analyzed is the scrambling code plot as shown in Figure 2-1.

The plot should visually be checked for:

Cells with no dominance at all:

This could indicate that a site was not radiating during the drive survey (this should be confirmed from the network stats).

If a cell is suspected to not have been radiating during the test, the problem must be confirmed before proceeding with the rest of the analysis. (The drive survey will need to be repeated if not all the cells were radiating).

Very poor dominance can also be caused by blocking of the antenna. If such a problem is suspected, a site visit must be made to verify the antenna clearance.

Cells with either excessive or poor dominance:

This could be due to a high site or non-optimum antenna tilts.

Cells with too large dominance will be causing interference to adjacent cells resulting in poorer capacity.

Areas of non-dominance:

This refers to areas where there is not a single clear dominant cell and where the best server changes too frequently. Such conditions will result in excessive number of soft handover events reducing the system efficiency and increasing the probability of call drops.

UE vs. Scanner scrambling codes:

It is also useful to perform visual comparison between the UE and scanner SC plots. Significant differences between the plots may indicate a missing neighbor or failed soft handover problem.



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Any observed issues should be marked on the plot for further investigation and correlation with other plots.

Figure 2-1 Scanner Scrambling Code plot

2.2 CPICH Coverage (RSCP)

The RSCP plot should be analyzed based on the thresholds presented in Table 1-1which are summarized below:

Good: RSCP -85 dBm

Fair: -95 dBm RSCP < -85 dBm

Poor: RSCP < - 95 dBm

Note: The above levels are applicable for outdoor scanner measurements.

Areas of poor coverage as well as significant areas of fair coverage should be highlighted for further investigation.



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Figure 2-2 Scanner CPICH RSCP plot

It is also useful to examine the RSCP coverage on per cell bases in order to highlight any cells that have too large a footprint. An example can be seen in Figure2-2 in section 4.

When comparing RSCP coverage from scanner and UE, it should be noted that the UE will have lower levels as a result of the in-car penetration loss and differences of antenna gain.

2.3 Interference (CPICH Ec/Io)

In parallel with the analysis of RSCP coverage, the Ec/Io plot should also be analyzed based on the thresholds presented in Table 1-1, as follows:

Good: Ec/Io -8 dB

Fair: -14 dB Ec/Io < -8 dB

Poor: Ec/Io < - 14 dB

Note: The -8 dB threshold takes into account the expected future interference increase as a result of increased traffic.

Areas of poor Ec/Io should be checked against RSCP levels as follows: z If RSCP levels are also POOR, then the fundamental cause of low is Ec/Io is poor

coverage



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z If RSCP levels are GOOD, this will imply strong system interference. Such scenario could arise when two sectors are pointing at each other.

Areas of poor Ec/Io should be highlighted for further investigation. An example Ec/Io plot is shown in Figure 2-3below.

Comparisons of the Ec/Io plots from the scanner and UE should be made. Areas where UE Ec/Io is significantly lower than that of the scanner may imply a problem of missing neighbor or delayed soft handover which can be associated with call drops.

Figure 2-3 Scanner CPICH Ec/Io

2.4 Uplink Coverage

Figure 2-4shows an example of UE Tx power. Any areas where the UE Tx power is high should be highlighted as areas of possible poor uplink coverage that require further investigation.

Areas of high Tx power should be compared to the CPICH plots to verify if the problem only exists on the uplink.



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Figure 2-4 UE Tx power

2.5 Pilot Pollution

Within Actix, the Pilot Pollution Set includes all pilots that are not in the active set BUT are within a certain margin of the best server (the margin is set to 8dB as listed in Table 1-1 above).

An example of pilot pollution results is provided in Table 2-1. This shows the % of time each cell was seen as a pilot polluter. Cells which are frequently seen as polluters (e.g. >10) should be marked and investigated.

These results should be used in conjunction with the Estimated Active Set Size, Figure 2-5, which shows the locations that have too many pilots.



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Table 2-1 Pilot pollution results

SC Count % in Pollution Set8 206 12.9%9 165 10.3%10 157 9.8%11 156 9.7%12 148 9.2%13 135 8.4%16 95 5.9%17 94 5.9%18 76 4.7%19 74 4.6%20 73 4.6%21 56 3.5%32 54 3.4%35 39 2.4%37 33 2.1%43 19 1.2%48 8 0.5%53 7 0.4%67 3 0.2%80 2 0.1%130 2 0.1%

2.6 Estimated Active Set Size

Another useful measure of pilot pollution is by looking at the estimated active set based on the scanner data. This plot is obtained by modeling the network soft handover parameters within Actix.

In order to see areas of excessive SHO candidates, the estimated active set size is allowed to exceed maximum of 3.

Locations where there are more than 3 pilots in the active set should be marked and sources of the interference should be identified. This can be done in conjunction with the Pilot pollution analysis.



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Figure 2-5 Estimated Active Set from scanner data

2.7 Neighbor List verification

The neighbor list could be verified and optimized using the Neighbor List Verification tool within Actix.

Prior to performing this analysis, the neighbor lists of each cell must be included in the CellRef file used by Actix.

The tool compares the drive survey data against the neighbor list in the CellReff and then provides the following recommendations for each cell:

Retain: This indicates that those neighbors have been confirmed from the drive survey data.

Add: Missing neighbors (thats neighbors seen in the drive test but not included in the neighbor list)

Remove: These neighbors that were not measured but are in the neighbor list.

Table 2-2below shows a typical example from running the Neighbor List Verification for one cell (SC: 009).



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It should be noted that careful consideration is needed prior to removing neighbors since the Actix results are drive route dependent.

Table 2-2 Example output of the Neighbor list verification

009 576 Retain 018 82 14.2%Retain 010 46 8.0%Retain 016 31 5.4%Retain 032 20 3.5%Retain 011 18 3.1%

Add 130 17 3.0%Retain 021 17 3.0%Retain 008 12 2.1%Retain 020 6 1.0%Retain 012 5 0.9%Retain 017 2 0.3%

Remove 053 0 0.0%Remove 019 0 0.0%Remove 034 0 0.0%Remove 037 0 0.0%Remove 013 0 0.0%Remove 051 0 0.0%

70548 Ajman Central 25.41204 55.447

Nbr SC Sample Count %Latitude LongitudeSample Count ActionSC Cell Site

2.8 UE SHO Performance

The success rates for event 1a, 1b & 1c and can be obtained from Actix as shown in the example below.

Table 2-3 Soft handover success rate

Number of Active Set Updates

Event CountEvent 1a - 328Event 1b - 306Event 1c - C 64

Number of Active Set Update Completes

Event CountEvent 1a - 326Event 1b - 305Event 1c - C 62

Soft-Handover Success Rate

Event RateEvent 1a - 99.4Event 1b - 99.7Event 1c - C 96.9

2.9 Drop Calls

All drop calls which are due to RF issues must be analyzed and the appropriate steps taken to avoid such drops from reoccurring.



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RF related issues that may result in drop calls may include: z Poor coverage (RSCP & Ec/Io) z High interference and hence poor Ec/Io z Poor uplink coverage (insufficient UE Tx power) z Poor dominance (best cell changes too frequently resulting in too many SHO

events) z Pilot pollution (too many cells present) z Missing neighbors z Fast change of RF conditions (e.g. turning a corner) If none of the above are the causes of the call drop and the RF conditions are evidently good at the location of the drop call, then the failure should be reported as a system fault for further analysis. (Such analysis would also require collecting network traces).

Note that drop calls that repeatedly occur in same locations must be analyzed in detail in order to determine the exact causes.

Drop Call Analysis

There are a number of approaches for drop call analysis and the steps below are designed to assist in quickly identifying RF related failures: z If RSCP & Ec/Io degrades before drop for BOTH scanner and UE then check for

coverage problems z If prior to the drop, the Ec/Io (and RSCP) degrades for UE ONLY while scanner

shows no degradation, then the following checks should be made: Is the best server for the UE is the same as that of the scanner? (If not, it is possible that the UE failed to perform soft handover)

Does UE camp on new cell immediately after drop?

If the UE camps on a new cell after the drop, was that cell neighbored to the previous cell? (if not, consider adding this neighbor)

Was the UE measuring this neighbor?

Were there too many and too quick changes of best server making it difficult for UE to perform measurements and SHO in time. (if this is the case: improve cell dominance through antenna optimization)

Does the UE Tx power increase to max prior to dropping call while Ec/Io level remains good?

If the Tx power increase is gradual and UE is far from site the failure is due to uplink coverage limitation

If the increase is sudden and UE may be not be too far from site - Check uplink load from SIB7 following drop call is it unusually high? z If uplink load is reported to be high, confirm from network stats that the high load is

due to genuine traffic otherwise check for a possible site fault z If uplink load is not high, problem could be due to possible power control failure. If the above steps do not reveal the causes of the drop calls then analysis of the messages should be carried out to determine the sequence of events prior to the drop call.

If the drop call does not appear to be RFrelated and the RF conditions at the location of the drop appear to be goods then no further work is needed as part of the RF Optimizations.



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However, exact location of the drop should be marked for later comparisons with future drive surveys (if un-explained drops keep occurring at the same location, more detailed investigation will be required to establish the exact causes).

OWJ102103 WCDMA RNO RF Optimization ISSUE 1.1 Summary


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Summary

This document outlined analysis approach for RF drive survey data as well as analysis of some drop calls. Throughout the report, example Actix plots were used for illustration purposes only as the data was collected from an incomplete cluster of sites.

Huawei Owj102103 Wcdma Rno Rf Optimization Issue1.1

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