54605993-W-RF-Optimization-Guide-20060608-a-3-1.pdf

W-RF Optimization Operations Guide For internal use only

2006-01-18 Huawei Confidential No Spreading Without Permission Page 1 of 65

Product name Confidentiality level

WCDMA RNP For internal use only

Product version Total 66 pages

3.1

W-RF Optimization Operations Guide

(For internal use only)

Prepared by He Fengming Date 2006-01-18

Reviewed by Xie Zhibin, Jiao Anqiang, Hua Yunlong, Hu Wensu, Wan Liang, Ai Hua, and Yan Lin

Date

2006-03-15

Reviewed by Qin Yan Date 2006-03-15

Approved by Date

Huawei Technologies Co., Ltd. All Rights Reserved



Revision Records

Date Revised version Description Author

2004-12-05 1.00 Initial transmittal Zhou Xinjie

2005-03-02 1.01 Revising it according to review Zhou Xinjie

2006-01-18 3.0 Simplifying tasks of RF optimization, enhancing operability, and adding content based on KPI optimization

He Fengming

2006-02-27 3.01 Replacing CQT method with indoor test; Clarifying solution scale of interference and access problems; Deleting content of removing neighbor cells; updating RF optimization flow chat

He Fengming

2006-03-15 3.02 Removing content of repeaters and baseline; Adding optimization target and method for SHO Factor based on DT; updating partial cases; adding cases for cluster division; Combining blind coverage and coverage voids to weak coverage; adding simple method for removing neighbor cells

He Fengming

2006-04-18 3.03 According to the review by change control board (CCB), changing the interval of VP tests to 15s, adding other simple causes to imbalance of uplink and downlink, correcting some grammatical mistakes.

He Fengming

2006-05-13 3.1 Adding HSDPA-related content; changing the RF optimization objectives of unloaded R99 and HSDPA networks in urban and suburban areas

Wu Yue and Wang Dekai



Table of Contents

Chapter 1 Introduction to RF Optimization .................................................................................... 9 1.1 Contents of RF Optimization ................................................................................................. 9 1.2 Document Structure ............................................................................................................... 9

Chapter 2 Basic Processes for RF Optimization ......................................................................... 11 2.1 Flow Chat of RF Optimization ............................................................................................. 11 2.2 Detailed Sections of RF Optimization .................................................................................. 12

2.2.1 Test Preparations ...................................................................................................... 12 2.2.2 Data Collection .......................................................................................................... 13 2.2.3 Problem Analysis ...................................................................................................... 13

Chapter 3 Test Preparations .......................................................................................................... 15 3.1 Deciding Optimization Goal ................................................................................................. 15 3.2 Dividing Clusters .................................................................................................................. 19 3.3 Deciding Test Route ............................................................................................................ 20 3.4 Preparing Tools and Data ................................................................................................... 21

3.4.1 Preparing Software ................................................................................................... 21 3.4.2 Preparing Hardware .................................................................................................. 21 3.4.3 Preparing Data .......................................................................................................... 22

Chapter 4 Data Collection .............................................................................................................. 23 4.1 Drive Test ............................................................................................................................ 23

4.1.1 DT Types ................................................................................................................... 23 4.1.2 Setting DT Indexes ................................................................................................... 24

1) Start Genex Probe 1.3 software.............................................................................................. 24

2) Select Configuration > System Config > Test Plan .............................................................. 24

3) Set DT indexes as shown in Figure 4-1 ................................................................................. 24

Figure 4-1 Setting DT .......................................................................................................................... 24 4.2 Indoor Test .......................................................................................................................... 25 4.3 Collecting RNC Configuration Data ..................................................................................... 25

Chapter 5 Coverage Problem Analysis ......................................................................................... 27 5.1 Coverage Problem Types .................................................................................................... 27

5.1.1 Weak coverage ......................................................................................................... 27 5.1.2 Cross-cell Coverage ................................................................................................. 28 5.1.3 Unbalanced Uplink and Downlink ............................................................................. 28 5.1.4 No Primary Pilot ........................................................................................................ 29

5.2 Coverage Analysis Processes ............................................................................................. 29 5.2.1 Downlink Coverage Analysis .................................................................................... 29 5.2.2 Uplink Coverage Analysis ......................................................................................... 33

Figure 5-4 Distribution of UE transmit power ...................................................................................... 34 5.3 Coverage Problem Cases ................................................................................................... 35

5.3.1 Weak Coverage Cases Due to Improper Engineering Parameters .......................... 35 5.3.2 Cross-cell Coverage Due to Improper NodeB Location ........................................... 36 5.3.3 Coverage Restriction Due to Improper Installation of Antennas .............................. 38

Chapter 6 Pilot Pollution Problem Analysis ................................................................................. 40 6.1 Pilot Pollution Definition and Judgment Standards ............................................................. 40

6.1.1 Definition ................................................................................................................... 40 6.1.2 Judgment Standards ................................................................................................. 40

6.2 Causes and Influence Analysis ........................................................................................... 40 6.2.1 Causes Analysis ....................................................................................................... 40 6.2.2 Influence Analysis ..................................................................................................... 42

6.3 Solutions to Pilot Pollution ................................................................................................... 42 6.3.1 Antenna Adjustment.................................................................................................. 42 6.3.2 PICH Power Adjustment ........................................................................................... 44 6.3.3 Using RRU or Micro Cells ......................................................................................... 45



6.4 Process for Analyzing Pilot Pollution Problem .................................................................... 46 6.5 Optimization Cases for Eliminating Pilot Pollution .............................................................. 47

6.5.1 Data Analysis before Optimization ............................................................................ 47 6.5.2 Data Analysis after Optimization ............................................................................... 52

Chapter 7 Handover Problem Analysis ......................................................................................... 55 7.1 Neighbor Cell Optimization .................................................................................................. 55

7.1.1 DT Data Analysis ...................................................................................................... 55 7.1.2 Removing Redundant Neighbor Cells ...................................................................... 60

7.2 SHO Factor based on DT Analysis ..................................................................................... 61 7.2.1 Definition of SHO Factor based on DT ..................................................................... 61 7.2.2 General Principles and Methods in Optimization ...................................................... 61

Chapter 8 Adjustment Methods ..................................................................................................... 63

Chapter 9 Summary ........................................................................................................................ 64

Chapter 10 Appendix: Coverage Enhancement Technologies .................................................. 65 10.1 Coverage-enhancing Technologies ................................................................................... 65

10.1.1 TMAs ....................................................................................................................... 65 10.1.2 Receive and Transmit Diversity .............................................................................. 65 10.1.3 RRU ........................................................................................................................ 65 10.1.4 Micro Cells .............................................................................................................. 65

References: ...................................................................................................................................... 66



List of Tables

Table 3-1 List of RF optimization goals ............................................................................................ 15

Table 3-2 Recommended software for RF optimization................................................................... 21

Table 3-3 Recommended hardware for RF optimization ................................................................. 21

Table 3-4 Data to be collected before optimization.......................................................................... 22

Table 4-1 Configured parameters to be checked ............................................................................. 25



List of Figures

Figure 2-1 RF optimization flow chat ................................................................................................ 12

Figure 3-1 Divided clusters in a project ............................................................................................ 20

Figure 4-1 Setting DT ....................................................................................................................... 24

Figure 5-1 RSCP for 1st Best ServiceCell ........................................................................................ 31

Figure 5-2 Distribution of pilot SC for the 1st Best ServiceCell ........................................................ 32

Figure 5-3 Analyzing comparison of UE and scanner coverage ...................................................... 33

Figure 5-4 Distribution of UE transmit power ................................................................................... 34

Figure 5-5 Coverage near Xiajiao Sugar Plant (before optimization) .............................................. 35

Figure 5-6 Coverage near Xiajiao Sugar Plant (after optimization).................................................. 36

Figure 5-7 Cross-cell coverage before optimization ......................................................................... 37

Figure 5-8 Few cross-cell coverage areas after optimization ........................................................... 38

Figure 5-9 Coverage restriction due to antenna blocked by roof ..................................................... 38

Figure 5-10 Optimizing antennas by adjusting feeders .................................................................... 39

Figure 6-1 Pilot pollution due to improper antenna azimuth............................................................. 43

Figure 6-2 Pilot pollution due to improper antenna down tilt ............................................................ 43

Figure 6-3 Pilot pollution due to improper distribution of cells.......................................................... 44

Figure 6-4 Pilot pollution due to ambient factors .............................................................................. 45

Figure 6-5 Survey photo of each cell related to pilot pollution ......................................................... 46

Figure 6-6 Pilot pollution near Yuxing Rd. ........................................................................................ 48

Figure 6-7 Best ServiceCell near Yuxing Rd. ................................................................................... 48

Figure 6-8 The 2nd best ServiceCell near Yuxing Rd. ..................................................................... 49

Figure 6-9 The 3rd best ServiceCell near Yuxing Rd. ...................................................................... 49

Figure 6-10 The 4th best ServiceCell near Yuxing Rd...................................................................... 50

Figure 6-11 Composition of pilot pollution near Yuxing Rd. .............................................................. 50

Figure 6-12 RSSI near Yuxing Rd. ................................................................................................... 51

Figure 6-13 RSCP of Best ServiceCell near Yuxing Rd. .................................................................. 51

Figure 6-14 RSCP of SC270 cell near Yuxing Rd. ........................................................................... 52

Figure 6-15 Pilot pollution near Yuxing Rd. after optimization .......................................................... 53

Figure 6-16 Best ServiceCell near Yuxing Rd. after optimization ..................................................... 53

Figure 6-17 RSCP of best ServiceCell near Yuxing Rd. after optimization ...................................... 54

Figure 6-18 RSCP of SC270 cell near Yuxing Rd. after optimization ............................................... 54

Figure 7-1 Changing conditions for judging neighbor cells .............................................................. 56

Figure 7-2 Generating neighbor cell analysis report by using Assistant .......................................... 57

Figure 7-3 Result of missing neighbor cells ..................................................................................... 57

Figure 7-4 Variation of active set Ec/Io recorded by UE before call drop ........................................ 59

Figure 7-5 Variation of active set Ec/Io recorded by scanner before call drop ................................. 59

Figure 7-6 RSCP for candidate of 4th Best ServiceCell ................................................................... 62



W-RF Optimization Guide

Key words: WCDMA, network optimization, and RF optimization

Abstract: This document describes tasks to be completed during RF optimization stage in

WCDMA network optimization. The tasks include RF optimization goal, flow,

procedure, input and output, and precautions concerning RF optimization.

Acronyms and abbreviations:

Acronyms and

abbreviations

Full spelling

CPICH Common Pilot Channel

DT Drive Test

KPI Key Performance Indicator

MML Man Machine Language

OCNS Orthogonal Channel Noise Simulator

OMC Operation and Maintenance Center

PS Packet-Switched domain

RF Radio Frequency

RNC Radio Network Controller

RSCP Received Signal Code Power

RTWP Received Total Wideband Power

VIC Very Important Cell

VIP Very Important People

VP Video Phone

RNO Radio Network Planning

TMA Tower Mounted Amplifier

HSDPA High Speed Downlink Packet Access

CQI Channel Quality Indicator





1 Introduction to RF Optimization

During RF optimization stage, as one of RNO, you optimize radio frequency (RF)

signals. This aims to control pilot pollution and SHO Factor based on DT in

optimizing signal coverage, so that the distribution of radio signals is normal in

next service parameters optimization stage.

1.1 Contents of RF Optimization

RF optimization includes the following aspects:

Pilot signal coverage optimization

It includes the following two parts:

Weak coverage optimization for ensuring seamless coverage by pilot

signals in the network

Primary pilot cell optimization for ensuring proper coverage areas by

each primary pilot cell, clear edge of primary pilot cells, and that

alternation of primary pilot cells is reduced as possible.

Pilot pollution optimization

Pilot pollution refers to that excessive pilots of approximately equivalent

strength cover an area without a primary pilot. Pilot pollution might cause

increasing of downlink interference, call drop due to frequent handover, low

network capacity. The problems must be solved by adjusting engineering

parameters.

Handover optimization

It consists of two parts:

Checking missing neighbor cells, verifying and perfecting list of

neighbor cells, solving handover, call drop, and downlink interference

problems.

Ensuring proper SHO Factor based on DT by adjusting engineering

parameters properly.

1.2 Document Structure

This documents consists of the following chapters:

Chapter 1 Introduction to RF Optimization

Chapter 2 Basic Processes for RF Optimization

Chapter 3 Test Preparations

Chapter 4 Data Collection

Chapter 5 Coverage Problem Analysis

Chapter 6 Pilot Pollution Problem Analysis

Chapter 7 Handover Problem Analysis



Chapter 8 Adjustment Methods

Chapter 9 Summary

Chapter 10 Appendix



2 Basic Processes for RF Optimization

Once all the sites are installed and verification is complete, RF optimization starts.

In some situations for a tight schedule, RF optimization might start after the

construction of partial sites is complete. RF optimization is usually performed after

80% of total sites in a cluster are constructed.

RF optimization stage is one major stage of RNO. It aims at the following aspects:

Optimizing signal coverage

Control pilot pollution

Control SHO Factor based on DT

RF optimization also involves optimizing list of neighbor cells.

When the indexes like DT and traffic measurement after RF adjustment meets

KPI requirements, RF optimization stage ends. Otherwise you must reanalyze

data and adjust parameters repeatedly until all KPI requirements are met. After

RF optimization, RNO comes to parameter optimization stage.

2.1 Flow Chat of RF Optimization

RF optimization includes the following four parts:

Test preparations

Data collection

Problem analysis

Parameter adjustment

0 shows the RF optimization flow chat.



RF optimization flow chat

In 0, the data collection, problem analysis, and parameter adjustment might be

repeatedly performed according to optimization goal and actual on-site situations

until RF indexes meet KPI requirements.

2.2 Detailed Sections of RF Optimization

2.2.1 Test Preparations

During test preparations, proceed as below:

Decide KPI goals for optimization according to the contract



Divide clusters properly and decide test route with the operator

The KPI test acceptance route is especially important.

Prepare tools and materials for RF optimization

This ensures smooth RF optimization.

2.2.2 Data Collection

Collect the following data:

UE and scanner data

Collect UE and scanner data by the following methods:

DT

Indoor test

Signaling tracing

Call data tracing at RNC side

Configuration data

The configuration data and the call data tracing help to locate problems.

Data collection is a precondition for problem analysis.

2.2.3 Problem Analysis

You can locate problems by analyzing collected data. After analyzing coverage

problems, pilot pollution problems, and handover problems, provide

corresponding adjustment solutions. After adjustment, test the adjustment result.

If the test result cannot meet KPI requirements, reanalyze problems and readjust

parameters until all KPI requirements are met.

Due to weak coverage, pilot pollution, and missing neighbor cells, the following

problems are related to location:

Downlink interference

Access problems

Call drop problems

The previous problems occur regularly. You can solve them by repeated

optimization.

If the coverage is good, pilot pollution and missing neighbor cells are not present,

the access and call drop problems need to be solved during parameter

optimization stage. You can refer to corresponding guidebooks. The period for

solving uplink interference problems (RTWP is over high but no high traffic

matches it) is long, even as long as the RF optimization ends. For solutions, see

WCDMA Interference Solution Guide.

Output an updated list of engineering parameters and list of cell parameters after

RF optimization. The list of engineering parameters reflects adjustment of

engineering parameters (such as down tilt and azimuth) during RF optimization



stage. The list of cell parameters reflects the adjustment of cell parameters (such

as neighbor cell configuration) during RF optimization stage.



3 Test Preparations

Test preparations include the following four aspects:

Deciding optimization goal

Dividing clusters

Deciding DT route

Preparing tools and data

3.1 Deciding Optimization Goal

The key of RF optimization is to solve problems as below:

Weak coverage

Pilot pollution

High SHO Factor based on DT

Actually, different operators might have different standards on KPI requirements,

index definition, and attention. Therefore the RF optimization goal is to meet the

coverage and handover KPI requirements in the contract (commercial

deployment offices) or planning report (trial offices).

Define the indexes as required by contract as below:

The index definition is the percentage ratio of the sampling points with the index

(such as CPICH Ec/Io) greater than the reference value in all sampling points.

Usually after RF optimization, the network must meets the index requirements

listed in 0.

Note:

0 provides reference indexes, only for guiding RNO engineers to clarify the RF

optimization objectives, not for actual project bidding. Different projects may have

different indexes. The contract decides the actual indexes and values.

0 lists the RF optimization objectives according to analysis of and suggestion to

coverage by existing network.

List of RF optimization objectives in R99 networks

Index Reference Remarks

CPICH Ec/Io ≥ –9dB ≥ 97% in

urban area

According to test result from the scanner,

in unloaded and outdoor conditions, in



≥ 97% in

suburban

area

planning coverage areas, test in a

grid-like route to cover all cells.

CPICH RSCP ≥ –95dBm

≥ 98% in

urban area

According to test result from the scanner,

in unloaded and outdoor conditions, in

planning coverage areas, test in a

grid-like route to cover all cells. The

coverage level request is basic. If

operators have penetration loss request,

add the penetration loss to the coverage

level.

≥ 95% in

suburban

area

SHO Factor based on DT 30%–40%

The SHO Factor based on DT should be

5% to 10% lower than the goal, because

the following optimizations cause the soft

handover factor to increase

Pilot pollution ratio ≤ 5% –

The RF optimization of HSDPA services aims to improve the distribution of UE

CQI.

According to theoretical analysis, the CQI reported by UE and PCPICH Ec/Nt

have relationship as below:

CQIUE = Ec/NtPCPICH + MPO + 10log16 + 4.5dB

Wherein,

Nt = (1- a) * Ior + Ioc + No

a is the orthogonal factor

lor is the signals of serving cell

loc is the interference signals from neighbor cells

No is the thermal noise

Io = Ior + Ioc + No

Therefore, PCPICH Ec/Nt is approximately equal to PCPICH Ec/Io.

MPO = Min (13,CellMaxPower –PcpichPower – MPOConstant)

The maximum transmit power of a cell is usually 43 dBm, and the pilot channel

power is 33 dBm. When MPOConstant is 2.5 dB, the default configuration by

RNC, the MPO is 7.5 dB.

The 4.5 dB is obtained according to the linear relationship between the SNR of all

the subscriber's HS-PDSCHs and the corresponding CQIs. Namely, SNR =

–4.5dB + CQIUE, and SNR = Ec/NtHS-PDSCH + 10log16.



When calculating CQIUE at UE side, the UE assumes that the total transmit power

of HS-PDSCH is PHS-DSCH = PPCPICH + MPO. Wherein, PPCPICH is the transmit

power of PCPICH. Therefore, Ec/NtHS-PDSCH = Ec/NtPCPICH + MPO. As a result,

the CQI reported by UE is as below:

CQIUE = Ec/NtPCPICH + MPO + 10log16 + 4.5dB

According to previous analysis, the offset between CQIUE and PCPICH Ec/Io is 24

dB. Therefore, in terms of actual optimization, to optimize CQI is to optimize

Ec/Io.

Assume that the cell power is dynamically distributed between R99 and HSDPA

networks. After receiving CQIUE from UE, the NodeB adjust the CQI as below:

The CQI adjusted by NodeB, CQINodeB = ( Pcell - Pcommon – PR99 – PHS-SCCH –

(PPCPICH + MPO ) + CQIUE.

Wherein,

Pcell is the maximum transmit power of cell

Pcommon is the CCH power of cell

PR99 is the power of downlink associated DPCH for R99 or HSDPA

subscribers.

PHS-SCCH is the HS-SCCH power.

Assume:

Pcell = 43 dBm

Pcommon is 20% of total power of cell

No R99 subscribers are in the cell

PR99 is too low to neglect

PHS-SCCH is 5% of total power of cell

Therefore,

CQINodeB = 1 + CQIUE

According to experience in actual test, based on the difference between the Ec/Io

from scanner and the Ec/Io from UE, reserve a margin of 1 dB. At the edge of cell,

an HSDPA subscriber may occupy total power of cell, so the throughput rate at

cell edge is equivalent to the throughput rate at cell edge for the single subscriber.

Error! Reference source not found. lists the relationship among the CQI

reported by UE, pilot Ec/Io, and throughput rate at MAC-HS layer (MPO = 7.5

dB).

Relationship among the CQI reported by UE, pilot Ec/Io, and throughput rate at

MAC-HS layer

9 > CQI 15 > CQI ≥ 9 CQI ≥ 15

Subscribers'

feeling Poor Fair Good



throughput rate at

MAC-HS layer for

single subscriber

0–320 kpbs 320 kbps to1.39

Mbps > 1.39 Mbps

Ec/Io > –15dB –15dB to –9dB ≥ – 9dB

The throughput rate provided in Error! Reference source not found. is based

on the test in the following conditions:

The codes and lub are not restricted.

The category 12 UE has a subscribed rate of 2 Mpbs.

The subscribed type is background or interactive service

Power is dynamically distributed. Namely, without R99 subscribers, all the

power is used by the HSDPA subscriber to guarantee rate as high as

possible.

According to the requirements on RF optimization of unloaded R99 network,

the CPICH Ec/Io ≥ –9 dB. After HSDPA is introduced, power is dynamically

distributed, and the single HSDPA subscriber at cell edge uses all the power.

Meanwhile, the downlink load reaches 90%, and CPICH Ec/Io ≥ 15.5dB.

If operators' requirement on throughput rate at cell edge is not the recommended

values as listed in Error! Reference source not found., search the required

value in 0.

0 lists the mapping relationship of HSDPA Catogory12 UE CQI and TB size. The

CQIs that is larger than 13 or smaller than 5 are excluded. The rate at MAC-HS

layer for the subscriber is (TBsize / 2ms) * (1 – BLER), wherein, the BLER is 10%.

Mapping relationship of HSDPA Catogory12 UE CQI and TB size

CQI TB Size

5 365

6 365

7 365

8 711

9 711

10 1055

11 1405

12 1742

13 2083



As previously mentioned, to optimize HSDPA is to optimize Ec/Io of target

networks. Therefore, in terms of optimization method, the HSDPA and R99

networks are consistent. The following optimization flow will not distinguish

HSDPA networks from R99 networks.

3.2 Dividing Clusters

According to the features of UMTS technologies, the coverage and capacity are

interactional and the frequency reuse factor is 1. Therefore RF optimization must

be performed on a group of or a cluster of NodeBs at the same time instead of

performing RF optimization on single site one by one. This ensures that

interference from intra-frequency neighbor cells are considered during

optimization. Analyze the impact of the adjustment of an index on other sites

before adjustment.

Dividing clusters involves approval by the operator. The following factors must be

considered upon dividing clusters:

According to experiences, the number of NodeBs in a cluster depends on

the actual situation. 15–25 NodeBs in a cluster is recommended. Too many

or few NodeBs in a cluster is improper.

A cluster must not cover different areas of test (planning) full coverage

services.

Refer to the divided clusters for network project maintenance of the operator.

Landform factor

Landforms affect signal propagation. Mountains block signal propagation, so

they are natural borders for dividing clusters. Rivers causes a longer

propagation distance, so they affect dividing clusters in various aspects. If a

river is narrow, the signals along two banks will interact. If the transportation

between two banks allows, divide sites along the two banks in the same

cluster. If a river is wide, the upstream and downstream will interact. In this

situation, the transportation between two banks is inconvenient, dividing

clusters by the bank according to actual situation.

A cell-like cluster is much usual than a strip-like cluster.

Administrative areas

When the coverage area involves several administrative areas, divide

clusters according to administrative areas. This is easily acceptable by the

operator.

DT workload

The DT must be performed within a day for a cluster. A DT takes about four

hours.

0 shows divided clusters in a project.



Divided clusters in a project

In 0:

JB03 and JB04 belongs to dense urban areas.

JB01 belongs to express way areas.

JB02, JB05, JB06, and JB07 belong to urban areas.

JB08 belongs to suburban area.

The number of NodeBs in a cluster is 18–22.

3.3 Deciding Test Route

Confirm the KPI DT acceptance route with the operator before DT. If the operator

already has a decided DT acceptance route, you must consider this upon

deciding the KPI DT acceptance route. If the objective factors like network layout

cannot fully meet the coverage requirements of decided test route by the operator,

you must point this out.

The KPI DT acceptance route is the core route of RF optimization test routes. Its

optimization is the core of RF optimization. The following tasks, such as

parameter optimization and acceptance, are based on KPI DT acceptance route.

The KPI DT acceptance route must cover major streets, important location, VIP,

and VIC. The DT route should cover all cells as possible. The initial test and final

test must cover all cells. If time is enough, cover all streets in the planned area.

Use the same DT route in every test to compare performances more accurately.

Round-trip DT is performed if possible.

Consider actual factors like lanes and left-turn restriction while deciding test route.

Before negotiating with the operator, communicate these factors with local drivers

for whether the route is acceptable.



3.4 Preparing Tools and Data

Prepare necessary software (listed in 0), hardware (listed in 0), and various data

(listed in 0), because the following test and analysis are based on them.

3.4.1 Preparing Software

0 lists the recommended software for RF optimization

Recommended software for RF optimization

No. Software Function Remarks

1 Genex Probe DT Above

V1.3

2 Genex

Assistant

Analyzing DT data and checking

neighbor cells

Above

V1.3

3 Genex Nastar Analyzing performance, checking

health, and locating problems –

4 Mapinfo Displaying maps and generating route

data –

3.4.2 Preparing Hardware

0 lists the recommended hardware for RF optimization

Recommended hardware for RF optimization

No. Device Specification Remarks

1 Scanner DTI Scanner –

2 Test terminal

and data line U626, E620, Qualcomm, and so on

At least two

test terminals.

If there is

HSDPA

request, use

the data card

E620. U626

does not

support

HSDPA.

3 Laptop PM1.3G/512M/20G/USB/COM/PRN –

4 Vehicle

mounted DC to AC, over 300W –



inverter

3.4.3 Preparing Data

0 lists the data to be collected before optimization

Data to be collected before optimization

No. Needed data Whether is

necessary Remarks

1 List of engineering parameters Yes –

2 Map Yes By Mapinfo or in

paper

3 KPI requirements Yes –

4 Network configuration

parameters Yes –

5 Survey report No –

6 Single site verification checklist No –

7 Floor plan of the target

buildings Yes For indoor test



4 Data Collection

During RF optimization stage, the key is the optimization of radio signals

distribution, with the major means of DT and indoor test. Before test, confirm with

the customer care engineers the following aspects:

Whether the target NodeBs, RNCs, and related CN are abnormal due to

being disabled, blocked, congested, and transmission alarms.

Whether the alarms have negative impact on the validity of test result data.

If the alarms exist, solve the problems before test.

DT is a major test. Collect scanner and UE data of radio signals by DT test. The

data is applicable in analyzing coverage, handover, and pilot pollution problems.

Indoor test involves the following areas:

Indoor coverage areas

Indoor coverage areas include inside buildings, department stores, and

subways.

Inside areas of important facilities

Inside areas of important facilities include gymnasiums and government

offices.

Areas required by the operator

Areas required by the operator include VIC and VIP.

Test the previous areas to locate, analyze, and solve the RF problems.

Indoor test also involves in optimizing handover of indoor and outdoor

intra-frequency, inter-frequency, and inter-system.

The DT and indoor test during RF optimization stage is based on VP service.

According to the contract (commercial deployment offices) and planning report

(trial offices), if seamless coverage by VP service is impossible in areas, such as,

suburban areas and rural areas, the test is based on voice services. For areas

with seamless coverage by PS384K service or HSDPA service required by the

contract (commercial deployment office) or planning report (trial office), such as

office buildings, press centers, and hot spot areas, the test is based on the above

services.

4.1 Drive Test

4.1.1 DT Types

According to different full coverage services in the planned areas, DT might be

one of the following:

3G ONLY continuous call test by using scanner + unloaded VP

According to simulation result and experiences, if the test result meets



requirements on VP service coverage, the test result will also meet identical

coverage requirements of PS144K, PS128K, and PS64K services.

3G ONLY continuous call test by using scanner + unloaded voice service

3G ONLY continuous call test by using scanner + unloaded PS384K

3G ONLY continuous call test by using scanner + unloaded HSDPA

4.1.2 Setting DT Indexes

The following paragraphs take VP service for example.

Setting DT indexes proceeds as below:

Start Genex Probe 1.3 software

Select Configuration > System Config > Test Plan

Set DT indexes as shown in 0

For setting voice, PS384K, and HSDPA services, see WCDMA Test Guide 3.1.

Setting DT

For setting DT, see the following table.

Index Meaning

Enable Whether to implement this index. True for implementation. False

for non-implementation. The recommended value is True.

Call

Number

Called number. Whether the called terminal supports VP must be

confirmed.

Setup

Time (s)

The maximum time for setting up calls. It ranges from 20–30s. The

recommended value is 25s.

Calling

Time (s)

The time for a single call from call start to normal end of call. Set it

great enough according to actual DT route. The recommended

value is 99999s.



Idle Time

(s) Call internal time. The recommended value is 10s.

Call Count Total call times. Set it great enough according to actual DT route.

The recommended value is 999 times.

Collect call data tracing at RNC side while performing drive test. This help to

locate and analyze problems.

Data to be collected includes:

Traced signaling messages of single subscriber

For the detailed description and collection method of call tracing data, see

WCDMA Equipment Room Operations Guide.

4.2 Indoor Test

GPS signals are unobtainable in door test. Obtain the plan of the target area

before test.

Indoor test consists of walking test and vertical test. Perform walking test to obtain

horizontal signals distribution inside buildings by selecting Indoor

Measurement > Walking Test. Perform vertical test to obtain vertical signals

distribution by selecting Indoor Measurement > Vertical Test. For the detailed

method, see WCDMA Test Guide 3.1.

Indoor test services are services by seamless coverage required in the contract

(commercial deployment office) or planning report (trial office). The method for

indoor test and requirements on collecting call tracing data are the same as DT.

4.3 Collecting RNC Configuration Data

During RF optimization stage, collect neighbor cell data of network optimization

and other data configured in RNC database. In addition, check whether the

configured data is consistent with the previously checked/planned data.

While checking configured data, feed back the improperly configured data (if

found) to product support engineers. During checking, pay special attention to

handover reselection parameters and power setting parameters, as listed in 0.

Configured parameters to be checked

Type Content to be checked

Handover

reselection

parameter

IntraFreqNCell (intra-frequency neighbor cell)

InterFreqNCell (inter-frequency neighbor cell)

InterRATNCell (inter-system neighbor cell)



Power

configuration

parameter

MaxAllowedULTxPower (maximum uplink transmit power of UE)

PCPICHPower (PCPICH transmit power)

HSDPA cell

configuration

Whether the HSDPA cell is activated

HS-PDSCH code configuration

HS-SCCH configuration

HS-PDSCH and HS-SCCH power configuration

For handover reselection parameters, check list of neighbor cells, including

intra-frequency, inter-frequency, and inter-system neighbor cells.

Output an updated Radio Parameter Configuration Data Table and parameter

revision records. This is useful in problem analysis and following optimization

stages.

Collecting data proceeds as below:

Start RNC LMT

Collect MML scripts

Convert neighbor cell configuration data in MML scripts to Excel files by using

Nastar

Save the data in the format in which the data can be imported to Assistant.

For details, see WCDMA Equipment Room Operations Guide and Nastar User

Manual.



5 Coverage Problem Analysis

Coverage problem analysis is key to RF optimization. It involves signal

distribution. The coverage problems to be analyzed include:

Weak coverage

Cross-cell coverage

Unbalance uplink and downlink

No primary pilot cell

5.1 Coverage Problem Types

5.1.1 Weak coverage

Introduction

Weak coverage refer to that the RSCP of pilot signals in a coverage area is

smaller than –95 dBm. It might be in:

Valley areas

Hillside back

Elevator well

Tunnel

Underground garage

Basement

Areas inside high buildings

If the pilot signals are weaker than that required by full coverage services (such

as VP and PS64K), or just meet the requirements, if the PICH Ec/Io cannot meets

the lowest requirements on full coverage services due to increased

intra-frequency interference, problems like difficult access of full coverage

services will occur.

If the RSCP of pilot signals is weaker than that of minimum access threshold in a

coverage area, the UE cannot camp on the cell, so the UE drops off the network

due to failing in location updating and location registration.

Solutions

For previous problems, use the following methods:

Increase pilot transmit power, adjust antenna down tilt and azimuth, increase

antenna height, use antennas with higher gain to optimize coverage.

If subscribers are abundant in the non-overlapped areas of neighbor NodeBs

or the non-overlapped areas are great, construct new NodeBs or expand the

coverage range of neighbor NodeBs. This ensures a software handover area



with enough great size. Pay attention to that increasing of coverage areas

might cause intra-frequency and inter-frequency interference.

Construct new NodeBs or add RRU in valley and hillside back areas with

weak coverage to expand coverage range.

Use RRU, indoor distributed system, leakage cable, and directional antenna

to solve problems in signal dead zone like elevator well, tunnel, underground

garage, basement, areas inside buildings.

5.1.2 Cross-cell Coverage

Introduction

Cross-cell coverage refers to that the coverage range of some NodeBs is beyond

the planned range and discontinuous primary pilot coverage areas form in

coverage areas of other NodeBs.

For example, if the NodeBs with a height much higher that the average height of

adjacent buildings transmit signals along upland or roads over far, a primary pilot

coverage area form in the coverage area of other NodeBs, an "island" forms.

Therefore, if a call accesses the "island" and the nearby cells of the "island" is not

configured as the neighbor cells, call drops once the UE leaves the island.

Though the nearby cells of the "island" is configured as the neighbor cells, the

"island" is over small, call also drops due to delayed handover.

If the two-side areas along a gulf are improperly planned, cross-cell coverage

occurs on these areas due to short distance between two sides of the gulf.

Consequently, interference occurs.

Solutions

For the previous problems, use the following methods:

For cross-cell coverage, prevent antennas from transmitting signals

straightforward along roads or reduce cross-cell coverage areas by using

sheltering effect of adjacent buildings. Meanwhile you must avoid

intra-frequency interference to other NodeBs.

For over high NodeBs, change the site. You might have difficulties in finding

new sites due to property and equipment installation. In addition, too large

mechanism down tilt causes aberration of antenna direction maps. Therefore

you can eliminate the "island" effect and reduce NodeB coverage areas by

adjusting pilot transmit power and using electric down tilt.

5.1.3 Unbalanced Uplink and Downlink

Introduction

Unbalanced uplink and downlink refers to the following situations in uplink and

downlink symmetric services:



The downlink coverage is good but the uplink coverage is restricted. More

specific, the UE transmit power reaches the maximum which still cannot

meet uplink BLER requirements.

The downlink coverage is restricted. More specific, the downlink DCH

transmit power reaches the maximum which still cannot meet downlink

BLER requirements.

If the uplink and downlink are unbalanced, call drops easily. The probable cause

is restricted uplink coverage.

Solutions

For the unbalanced uplink and downlink problems, check for interference by

monitoring RTWP alarms of NodeB. For the method, see WCDMA Interference

Solution Guide.

Other causes may lead to unbalanced uplink and downlink, such as:

Uplink and downlink gain of repeaters and interference amplifier are faulty.

In an Rx/Tx detach system, the Rx diversity antenna-feeder system is faulty.

NodeB problems, such as power amplifier failure

For previous problems, check the work state whether there are alarms, whether it

is normal. Solve the problem by replacing NEs, isolating faulty NEs, and adjust

NEs.

5.1.4 No Primary Pilot

Introduction

No primary pilot areas refer to the areas where no primary pilot is or the primary

cell changes frequently. In no primary pilot areas, UE hands over frequently, so

the system efficiency is lowered and probability of call drop increases.

Solutions

In no primary pilot areas, you can enhance the coverage by strong signals of a

cell (or near cells) and reduce the coverage by weak signals of other cells (or far

cells) by adjusting antenna down tilt and azimuth.

5.2 Coverage Analysis Processes

5.2.1 Downlink Coverage Analysis

Downlink coverage analysis involves analyzing CPICH RSCP obtained by drive

test.

The quality standard of CPICH RSCP must be combined with the optimization

standard. Assume that the optimization standard is as below:

CPICH_RSCP ≥ –95 dBm >= 95% Scanner test result in outdoor unloaded



conditions

The corresponding quality standard is:

Good if CPICH_RSCP ≥ –85 dBm

Fair if –95 dBm ≤ CPICH_RSCP < –85 dBm

Poor if CPICH_RSCP < –95 dBm

Mark the areas with weak coverage or common seamless coverage of large

areas for further analysis. Mark the areas with downlink coverage voids, analyze

the distance relations with neighbor NodeBs and environments, and check the

following:

Whether the CPICH RSCP of neighbor sites is normal

Whether coverage can be enhanced by adjusting antenna down tilt and

azimuth.

During adjusting antennas, avoid new coverage voids while eliminating some

coverage voids. If the coverage voids cannot be eliminated by adjusting antennas,

construct sites to solve it.

Anayzing Pilot Coverage Strength

Usually, the strongest RSCP received by each scanner in the coverage area must

be above –95 dBm.

Start Assistant. Analyze scanner-based RSCP for 1st Best ServiceCell, and you

can obtain the distribution of weak coverage area, shown in 0.

In 0, weak coverage areas with RSCP smaller than –95 dBm in the DT route.

According to scanner and UE, the pilot RSCP is acceptable. If the scanner

antenna is mounted outside the car, and the UE is inside the car, there is a

penetration loss of 5 to 7 dB. Use scanner data to avoid incomplete pilot

information measured by UE due to missing neighbor cells.



RSCP for 1st Best ServiceCell

Analyzing Primary Pilot Cell

Cell primary pilot analysis is analyzing cell scramble information obtained in DT.

The content to be checked include (by Assistant):

Weak coverage cell

Start Assistant. Analyze scanner-based RSCP for SC, and you can obtain

the signal distribution of each cell (scramble). According to DT data, if the

scramble signals of a cell are not present, probably some sites cannot

transmit signals during test. If a cell cannot transmit signals during DT, the

DT of relative areas must be re-performed. Very weak coverage might be

result of blocked antennas, so you must check the survey report of the site

and check installation of on-site antennas. No (poor) coverage cell might be

due to that the DT route does not cover the cell coverage area. In this case,

reevaluate the DT route for the rationality and perform DT again.

Cross-cell coverage cell

Start Assistant. Analyze scanner-based RSCP for SC, and you can obtain

the signal distribution of each cell (scramble). If the signals of a cell are

widely distributed, even in the neighbor cells and the cells next to its

neighbor cells, the signals of the cell is present, the cell encounters a

cross-cell coverage which might be due to over high site or improper down

tilt of antenna. The cross-cell coverage cells interferes neighbor cells, so the

capacity declines. You can solve the problem by increasing the down tilt of

antenna or lowering the height of antenna. Avoid forming new weak

coverage areas while solving cross-coverage problems. Pay special

attention to the adjustment of engineering parameters which might cause



coverage voids. Be conservative that cross-cell coverage is better than

coverage voids if no other choices are available.

No primary pilot cell

Start Assistant. Analyze scanner-based SC for 1st Best ServiceCell, and

you can obtain the scramble distribution of the best cell. If multiple best cells

changes frequently in an cell, the cell is a no primary pilot cell, as shown in 0

No primary pilot cell forms due to the following causes:

Cross-cell non-seamless coverage due to over high site

Pilot pollution in some areas

Coverage voids at edges of coverage areas

Therefore intra-frequency interferences forms which causes ping-pong

handover and affects performances of service coverage.

Distribution of pilot SC for the 1st Best ServiceCell

Analyzing comparison of UE and Scanner Coverage

Missing neighbor cells, improper parameters of soft handover, cell selection and

reselection cause the consistent between scanner primary pilot cell and camped

cell in idle mode or Best ServiceCell in the active set in connection mode of UE.

After optimization, the Ec/Io for 1st Best ServiceCell of UE and scanner is

consistent. In addition, the coverage map of UE is marked by clear bordering

lines of Best ServiceCell, as 0.



Analyzing comparison of UE and scanner coverage

5.2.2 Uplink Coverage Analysis

The corresponding quality standard is:

Good if CPICH_RSCP ≥ –85 dBm

Fair if –95 dBm ≤ CPICH_RSCP < –85 dBm

Poor if CPICH_RSCP < –95 dBm

Uplink coverage analysis is analyzing UE transmit power obtained in DT.

The quality standards of UE transmit power must be combined with optimization

standards. Assume the optimization indexes of UE transmit power as below:

UE_Tx_Power ≤ 10

dBm >= 95%

The test result of voice service by test

handset. Assume the maximum transmit

power of UE is 21 dBm.

The defined corresponding quality standards are:

Good if UE_Tx_Power ≤ 0 dBm

Fair if 0 dBm < UE_Tx_Power ≤ 10 dBm

Poor if UE_Tx_Power > 10 dBm

For areas with poor index, judge whether the increasing of UE transmit power is

due to call drop or poor uplink coverage. Geographically displayed on the map,

the former is as a point of sudden increment with call drop while the latter is an

area with seamless coverage unnecessarily with call drop.



Mark the areas with weak coverage or large common seamless coverage for

further analysis. Check whether downlink CPICH RSCP coverage voids exist in

the areas with uplink coverage voids. Solve the problem with both uplink and

downlink weak coverage by analyzing downlink coverage analysis. If only the

uplink coverage is poor without uplink interference (see WCDMA Interference

Solution Guide), solve the problems by adjusting down tilt and azimuth of antenna,

and adding TMAs.

Analyzing Uplink Interference

Check for uplink interference by tracing and analyzing RTWP data. For details,

see WCDMA Interference Solution Guide.

Distribution of UE Transmit Power

The distribution of UE transmit power reflects the distribution of uplink

interference and uplink path loss. In 0, UE transmit power is lower than 10 dBm

normally. Only when uplink interference and coverage area edge exist will the UE

transmit power increase sharply to 21 dBm (Some UEs that support HSDPA,

such as E620, with a power class of 3, the maximum transmit power is 24 dBm),

and the uplink is restricted. Comparatively restricted uplink coverage occurs

much easily in macro cells than in micro cells.

Distribution of UE transmit power



5.3 Coverage Problem Cases

5.3.1 Weak Coverage Cases Due to Improper Engineering Parameters

Phenomenon

In 0, the pilot RSCP is lower than –95 dBm in the marked red area. This belongs

to weak coverage, which might cause call drop.

Coverage near Xiajiao Sugar Plant (before optimization)

Analysis

In 0, the problem lies in that Xiajiao Sugar Plant sector B mainly covers the

marked area but Materials Building sector A partially covers the marked area.

Initially engineers consider enhancing the coverage of the marked area by

adjusting the two cells. According to the survey report, other buildings opposite

Materials Building prevent sector A from transmit signals, so adjusting antenna

fails to enhance the coverage of the areas.

Solutions

Keep the parameter configuration of Materials Building sector A, but adjust the

azimuth of Xiajiao Sugar Plant sector B from 170° to 165°, down tilt from 10° to

8°.

0 shows the coverage near Xiajiao Sugar Plant (after optimization)



Coverage near Xiajiao Sugar Plant (after optimization)

In 0, the coverage in the marked area is enhanced clearly after adjusting

engineering parameters of Xiajiao Sugar Plant.

5.3.2 Cross-cell Coverage Due to Improper NodeB Location

Phenomenon

In a trial office, the Erqi Rd. NodeB is 60-meter high, over 20 meters than nearby

buildings. This causes cross-cell coverage easily and brings intra-frequency

interference to other NodeBs, as shown in 0.



Cross-cell coverage before optimization

Aanalysis

For a high NodeB problem, adjust fixed electric down tilt of antenna from 2° to 6°.

Because the Erqi Rd. NodeB is at the edge of network coverage, reduce

interferences to other NodeBs by adjusting antenna down tilt and azimuth. In this

case, no equipment is removed. Engineers solve the cross-cell coverage by

increasing mechanism down tilt and adjusting azimuth.

Solutions

After adjustment of down tilt to 4°, the most cross-cell coverage areas are

eliminated, with only few cross-cell coverage areas, as shown in 0.



Few cross-cell coverage areas after optimization

For similar high NodeBs, you can combine adjustable down tilt of electric antenna

and mechanism antenna to better control signal coverage.

5.3.3 Coverage Restriction Due to Improper Installation of Antennas

Phenomenon

From 0, the antenna of a project is mounted on a roof (10-meter tall).

Coverage restriction due to antenna blocked by roof



At the optimization stage after network construction, in front of the traffic lights

below antennas, video quality declines due to VP mosaic and PS384K service is

reactivated.

Analysis

In terms of planning, 3G and 2G antennas are mounted in a co-location site.

According to coverage test data of 2G antenna, 2G signals does not fluctuate

sharply under the site and under the traffic lights. Namely, if the 3G and 2G

antennas are in the same location, 3G signals will cover the areas around traffic

lights. The problem lies in that the 3G antenna is mounted too close to the wall on

the roof and the wall blocks signals so the special installation conditions of

antennas are not met. In addition, the 2G antenna and its installation parts affect

the pattern of 3G antenna. This changes the radiation pattern of 3G antenna.

According to the installation scene, adjusting location of 3G antenna is difficult.

Solutions

According to discussion between 2G and 3G engineers, the minimum adjustment

solution without affecting 2G coverage is as below:

Connect the 3G and 2G TX/RX feeder to two feeders of outside wideband

polarization antenna

Connect the 3G and 2G RX feeder to two feeders of inner wideband antenna.

0 shows the connection.

Optimizing antennas by adjusting feeders



6 Pilot Pollution Problem Analysis

6.1 Pilot Pollution Definition and Judgment Standards

6.1.1 Definition

The pilot pollution is that excessive strong pilots exist in a point but no primary

pilot is strong enough.

6.1.2 Judgment Standards

Pilot pollution exists if all the following conditions are met:

The number of pilots that meet the following condition is more than ThN

CPICH_RSCP > ThRSCP_Absolute

(CPICH_RSCP1st - CPICH_RSCP(ThN +1)th)< ThRSCP_Relative

Assume that ThRSCP_Absolute = –100 dBm, ThN = 3, and ThRSCP_Relative = 5 dB, and

then pilot pollution exists if all the following conditions are met:

More than three pilots meet the following condition

CPICH_RSCP > –100 dBm.

(CPICH_RSCP1st - CPICH_RSCP4th) < 5 dB

6.2 Causes and Influence Analysis

6.2.1 Causes Analysis

Ideally the signals in a cell is restricted within its planned range. However the

signals cannot reach the ideal state due to the following factors of radio

environment:

Landform

Building distribution

Street distribution

Waters

Pilot pollution is the result of interaction among multiple NodeBs, so it occurs in

urban areas where NodeBs are densely constructed. Normally typical areas

where pilot pollution occurs easily include:

High buildings

Wide streets

Overhead structure

Crossroad

Areas round waters



Improper Cell Distribution

Due to restriction to site location and complex geographic environment, cell

distribution might be improper. Improper cell distribution causes weak coverage of

some areas and coverage by multiple strong pilots in same areas.

Over High NodeB or Highly-mounted Antenna

If a NodeB is constructed in a position higher than around buildings, most areas

will be with in the line-of sight range. Therefore signals are widely transmitted.

Over high site cause difficult control of cross-cell coverage, which causes pilot

pollution.

Improper Antenna Azimuth

In a network with multiple NodeBs, the antenna azimuth must be adjusted

according to the following factors:

NodeB distribution of the entire network

Coverage requirements

Traffic volume distribution

The sector azimuth of each antenna is set to cooperate with each other. If the

azimuth is improperly set:

Some factors might cover the same area. This causes excessive pilot

pollution.

Weak coverage exist in some areas without primary pilot.

The previous two situations might lead to pilot pollution. Therefore you must

adjust the antenna according to actual propagation.

Improper Antenna Down Tilt

Setting antenna down tilt depends on the following factors:

Relative height to around environment

Coverage range requirements

Antenna types

If the antenna down tilt is improper, signals are received in the areas which are

covered by this site. Therefore interferences to other areas causes pilot pollution.

Even worse, interferences might cause call drop.

Improper PICH Power

When the NodeBs are densely distributed with a small planned coverage rang

and the PICH power is over high, the pilot covers an area larger than the planned

area. This causes pilot pollution.



Ambient Factors

The signals cannot reach the planned state due to the following factors of radio

environment:

Landform

Building distribution

Street distribution

Waters

The ambient factors include:

High buildings or mountains block signals from spreading

The signals of a NodeB to cover a target area are blocked by high buildings

or mountains, so the target area will have no primary pilot. This causes pilot

pollution.

Streets or waters influences signals

When the antenna direction is pointing a street, the coverage range is

expanded by the street. When the coverage range of a NodeB overlaps with

the coverage range of other NodeBs, pilot pollution occurs.

High buildings reflect signals

When high glassed buildings stand near a NodeB, they will reflect signals to

the coverage range of other NodeBs. This causes pilot pollution.

6.2.2 Influence Analysis

Pilot pollution causes the following network problems.

Ec/Io Deterioration

Multiple strong pilots interferes useful functional signals, so Io increases, Ec/Io

decreases, BLER increases, and network quality declines.

Call Drop Due to Handover

More than three strong pilots or no primary pilot exists in multiple pilots, frequent

handover occurs among these pilots. This might cause call drop.

Capacity Decline

The interference of the areas with pilot pollution increases, the system capacity

declines.

6.3 Solutions to Pilot Pollution

6.3.1 Antenna Adjustment

According to the test, change pilot signal strength of an area with pilot pollution by

adjusting antenna down tilt and azimuth. This changes the distribution of pilot



signals in the area. The principle for adjustment is enhancing primary pilot and

weakening other pilots.

To enhance pilot coverage of an area, adjust the antenna azimuth pointing the

area. To weakening pilot coverage of an area, adjust the antenna azimuth

pointing the opposite direction of the area. Adjusting down tilt is similar. You can

increase the cell coverage range by reducing antenna down tilt and reduce cell

coverage range by increasing antenna down tilt.

Adjusting antennas is restricted to a range. If the down tilt is over small, you might

enhance cell coverage but causes cross-cell coverage. If the down tilt is over

large, you might weaken cell coverage but you might change the antenna pattern.

0 shows the pilot pollution due to improper antenna azimuth.

Pilot pollution due to improper antenna azimuth

In 0, the area marked in black encounters pilot pollution due to improper azimuth

of the antenna of SC100 sector (scramble No. is 100). The SC100 sector covers

the area with an antenna azimuth of 90°, so the coverage is poor with weak

signals and no primary pilot, which cause pilot pollution.

After adjustment of the antenna azimuth from 90° to 170°, the primary pilot

signals become stronger and pilot pollution is eliminated.

0 shows the pilot pollution due to improper antenna down tilt.

Pilot pollution due to improper antenna down tilt



In 0, the area marked in blacked encounters pilot pollution due to improper

antenna down tilt. The down tilt of SC360 cell is 2°, so the coverage area is large,

cross-cell coverage is difficult to control, and interferences to other areas form.

After adjustment of antenna down tilt of SC360 cell from 2° to 7°, the cross-cell

coverage by SC360 cell is eliminated and pilot pollution is eliminated.

Some areas with pilot pollution is inapplicable to the previous adjustment. You

can use the following methods based on actual situation:

Change the antenna to a different type

Add reflection device or isolation device

Adjust installation position of antenna

Adjust NodeB location

6.3.2 PICH Power Adjustment

Pilot pollution is caused by the coverage by multiple pilots. A direct method to

solve the problem is to form a primary pilot by increasing the power of a cell and

decreasing the power of other cells.

An over large down tilt causes aberration of antenna pattern. To reduce coverage

range by pilot, you can decrease PICH power. Over small down tilt causes

cross-cell coverage. To increase coverage range by pilot, you can increase PICH

power. Adjusting power and adjusting antenna must cooperate.

0 shows the pilot pollution due to improper distribution of cells.

Pilot pollution due to improper distribution of cells

In 0,



The distance between NodeB A and NodeB B is 1260 meters.

The distance between NodeB A and NodeB C is 2820 meters.

The distance between NodeB B and NodeB C is 2360 meters.

The distances is unbalanced, so the pilot pollution is difficult to eliminate.

The optimization is to reduce weak pilot strength and eliminate pilot pollution,

detailed as below:

Ensure seamless coverage between cells by not adjusting transmit power of

SC20 and SC30 cells.

Decrease the PICH power of SC10, SC40, and SC50 cells by 3 dB. These

cells have little impact on seamless coverage.

6.3.3 Using RRU or Micro Cells

If adjusting power and antenna is not effective to solving pilot pollution, use RRU

or micro cells.

Using RRU or micro cells aims to bring a strong-signal coverage in the area with

pilot pollution, so the relative strength of other signals decreases.

When a network expansion is necessary or more requirements is on network

quality, using RRU or micro cells is recommended. Micro cells are used in traffic

hot spot areas, they support multiple carriers. Micro cells are used if large

capacity is needed. Compared with using RRU, using micro cells is more

expansive.

0 shows pilot pollution due to ambient factors.

Pilot pollution due to ambient factors

The area marked in black encounters pilot pollution due to ambient factors. The

area is covered by SC60 cell of NodeB A, SC110 cell or NodeB B, and SC130 cell

of NodeB C. However, shown in 0, hills prevent NodeB A from transmitting signals,

high buildings prevent NodeB B and NodeB C from transmitting signals, so the

signals from NodeB A, NodeB B, and NodeB C are weak. On the contrary, SC240



and SC250 cells of NodeB D have good propagation conditions in this direction.

Therefore the cross-cell coverage is serious and pilot pollution occurs.

Survey photo of each cell related to pilot pollution

High buildings or hills blocks the area, so no strong pilot is present in the area.

For this problem, adjusting antenna down tilt has little effect on eliminating pilot

pollution. Instead adding RRU helps solve the problem.

6.4 Process for Analyzing Pilot Pollution Problem

The process for analyzing pilot pollution problem proceeds as below:

Start Assistant. Analyze scanner-based RSCP for 1st Best ServiceCell and EcIo

for 1st Best ServiceCell. Select the areas with high RSCP and poor EcIo as

candidate areas with pilot pollution.

Analyze scanner-based Whole PP. Select the areas corresponding to candidate

areas as the key areas with pilot pollution.

Locate the cells that cause pilot pollution of the key areas.

Based on RSCP for 1st Best ServiceCell, judge whether the pilot pollution is

caused by existence of multiple strong pilots or lack of a strong pilot. For the

former cause, you can solve the problem by weakening other strong pilots.

For the latter cause, you can solve the problem by strengthening some

strong pilot.

Analyze the RSCP and Ec/Io distribution of areas related to pilot pollution and

confirm the cells that need eliminating the coverage of an area and that need

enhancing the coverage of an area. Based on the actual environment,

analyze the specific causes to pilot pollution (for analyzing causes, see



6.2.1). For specific causes, provide solutions to pilot pollution (for solution,

see 6.3). While eliminating pilot pollution in an area, consider the influence to

other areas and avoid causing pilot pollution or coverage voids to other

areas.

Retest after adjustment. Analyze RSCP, Ec/Io and Whole PP. If they cannot meet

KPI requirements, re-optimize the network by selecting new key areas until

KPI requirements are met.

Note:

In the new optimization, do not adjust the cells that was adjusted in last

optimization. You can add other key areas analyzed by Whole PP (the part that

does not correspond to the candidate areas)

6.5 Optimization Cases for Eliminating Pilot Pollution

The following sections take an optimization by a project and describes the

process for analyzing pilot pollution. 1

6.5.1 Data Analysis before Optimization

Locating Pilot Pollution Point

0 shows the pilot pollution point near Yuxing Rd. SC270 cell is planned to cover

the area with pilot pollution.

Pilot pollution near Yuxing Rd.

1 No new complete case is available, so an old case is used here. The future version will

provide new cases.



Analyzing Signal Distribution of Cells Near Pilot Pollution Point

Best ServiceCell near Yuxing Rd.

The 2nd best ServiceCell near Yuxing Rd.



The 3rd best ServiceCell near Yuxing Rd.

The 4th best ServiceCell near Yuxing Rd.



Composition of pilot pollution near Yuxing Rd.

From 0, 0, 0, 0, and 0, though SC20 cell is planned to cover the area, but the best

ServiceCell is as listed in the following table:

Best ServiceCell Primary Others

1st best ServiceCell SC220 SC260 and SC270

2nd best ServiceCell SC270 SC260, SC220, and SC200

3rd

best ServiceCell SC200 SC270 and SC260

4th best ServiceCell SC200 SC270 and SC260

Analyzing RSSI Distribution Near Pilot Pollution Point

0 shows the RSSI near Yuxing Rd..

RSSI near Yuxing Rd.

0 shows the RSCP of Best ServiceCell near Yuxing Rd..



RSCP of Best ServiceCell near Yuxing Rd.

As shown in 0, the RSSI of the areas with pilot pollution is not large, about –100

dBm to –90 dBm. As shown in 0, the RSCP of Best ServiceCell is between –105

dBm to –100 dBm. The pilot pollution of the area is caused by no strong pilot, so

you can solve the problem by strengthening a strong pilot.

Analyzing RSCP Distribution of Related Cells

0 shows the RSCP of SC270 cell near Yuxing Rd.

RSCP of SC270 cell near Yuxing Rd.

The SC270 cell is planned to cover the area. 0 shows RSCP of RSCP distribution

of SC270 cell. The signals from SC270 cell are weak in the area with pilot

pollution.

According to on-site survey, the residential area is densely distributed by 6-floor

or 7-floor buildings. The test route fails to cover the major streets, and is

performed in narrow streets with buildings around, so the signals are blocked.



The suggestion is to adjust the azimuth of SC270 cell from 150° to 130° and the

down tilt from 5° to 3°. This enhances the coverage of SC270 cell.

6.5.2 Data Analysis after Optimization

After analysis of DT data, the expected result after adjustment is that the

coverage area by SC270 cell increases and the coverage is enhanced.

0 shows the pilot pollution near Yuxing Rd. after optimization.

Pilot pollution near Yuxing Rd. after optimization

0 shows the best ServiceCell near Yuxing Rd. after optimization.

Best ServiceCell near Yuxing Rd. after optimization

0 shows the RSCP of best ServiceCell near Yuxing Rd. after optimization.



RSCP of best ServiceCell near Yuxing Rd. after optimization

0 shows the RSCP of SC270 cell near Yuxing Rd. after optimization.

RSCP of SC270 cell near Yuxing Rd. after optimization

According to the DT data, the pilot pollution near Yuxing Rd. after optimization is

eliminated, the signals from SC270 cell after optimization are stronger, and the

SC270 becomes the best ServiceCell. This complies with the expected result.



7 Handover Problem Analysis

During RF optimization stage, the involved handover problem is about neighbor

cell optimization and SHO Factor based on DT control.

Control the size and location of handover areas by adjusting RF parameters. You

can eliminate handover call drop due to sharp fluctuation and increase handover

success rate.

For other handover problems, see WCDMA Handover and Call Drop Problem

Optimization Guide.

7.1 Neighbor Cell Optimization

The neighbor cell optimization includes adding and removing neighbor cells.

Missing neighbor cells causes that a strong-pilot cell cannot be listed into the

active set so the interference increases as strong as call drop occurs. For missing

neighbor cell, you must add necessary neighbor cells.

Redundant neighbor cells causes that the neighbor cell information is excessive

and unnecessary signals cost occurs. When the neighbor cell list is fully

configured, the needed neighbor cell cannot be listed. For this problem, remove

redundant neighbor cells.

During RF optimization stage, missing neighbor cell is a key problem. The

methods for adding neighbor cells are listed below.

7.1.1 DT Data Analysis

Scanner Data Analysis

The daemon analysis tools can usually check for missing neighbor cells. The

principle is as below:

Compare the pilots scanned by scanner and the configured pilots of neighbor

cell list.

Locate these pilot scrambles that meet the handover conditions and that are

not in the neighbor cell list. Output them as a missing neighbor cell report.

The following checks and methods related to missing neighbor cells are based on

Assistant.

Type information about NodeB and neighbor cells

For details, see Assistant User Manual.

Decide conditions for judging neighbor cells

Change the conditions for judging neighbor cells by selecting Modify

Dataset Property. The default configuration is that if the difference between



the pilot of candidate cell and the base cell is within 5 dB the candidate cell

can be listed as a neighbor cell. The configuration must comply with the

actual configuration of system (overall parameters), as shown in 0.

Changing conditions for judging neighbor cells

The parameters and meanings are as below (according to default

configuration of RNC1.5, you just list the parameters to be changed):

Parameter Meaning Recommended

value

1A Threshold 1A event threshold 3 dB

1A Hysteresis 1A event hysteresis 0 dB

1A Time to

Trigger Time to trigger 1A event 0.320s

1B Threshold 1B event threshold 6 dB

1B Hysteresis 1B event hysteresis 0 dB

1C Hysteresis 1C event hysteresis 4 dB

1D hysteresis 1D event hysteresis 4 dB

Count Threshold Times threshold for judging

neighbor cells 10

Generate a missing neighbor cell report



Generating neighbor cell analysis report by using Assistant

Proceed as shown in 0, the Assistant generates a neighbor cell analysis

report in the format of Excel. This Excel-formatted report contains four sheets:

Scanner Statistic, Scanner Result, Imported Config, and Scanner vs Config.

Wherein, the Scanner vs Config sheet is for comparing neighbor cells

generated by scanner and the configured neighbor cells.

0 shows the result of missing neighbor cells.

Result of missing neighbor cells



For the missing neighbor cells generated automatically by Assistant, you must

check according to the location information of the cell on the map whether to add

the missing neighbor cells to the neighbor cell list. For the missing neighbor cells

due to cross-cell coverage, the primary task is to solve coverage problem by

adjusting RF parameters. If this fails, you can temporarily solve the problem by

adding neighbor cells.

UE Data Analysis

The daemon analysis tool can seldom analyze UE data automatically and

generate missing neighbor cells, so RNO engineers must analyze the missing

neighbor cells one by one for confirmation. Missing neighbor cell might cause call

drop or access failure or cause Ec/Io to deteriorate for a period. Based on data

analysis by scanner, you can easily locate these points with missing neighbor

cells, detailed as below:

Compare the active set Ec/Io distribution diagram measured by UE and that

measured by scanner

The spots with missing neighbor cells has a poor Ec/Io measured by UE and

a strong Ec/Io scanned by scanner. Locate the areas for further analysis.

Check the points with poor Ec/Io and check whether the strongest scramble by

scanner is neither in active set nor in monitoring set. If yes, move to the third

step for confirmation. If the scramble exists in the monitoring set, the

problem is not about missing neighbor cell but about Ec/Io deterioration due

to handover (reselection) delay and soft handover failure.

Check the latest intra-frequency measurement control whether the neighbor cell

list contains the strong scrambles by scanner

You can also directly check the neighbor cells continuation of the base cell

under the RNC for deciding missing neighbor cells.

The following paragraphs describes a case about call drop due to missing

neighbor cell.

Check the Ec/Io coverage information of active set measured by UE, and you can

find that the Ec/Io of the active set is weak near call drop point and the signals are

as weak as lower than –15 dB. The base cell is SC209 cell, as shown in 0.



Variation of active set Ec/Io recorded by UE before call drop

You also need to check data from scanner about the call drop point for the points

with poor signals. The signals , from SC128 cell, measured by scanner is strong,

as shown in 0.

Variation of active set Ec/Io recorded by scanner before call drop

From 0 and 0, SC128 encounters missing neighbor cell. For confirmation, check

the message process behind to front for intra-frequency measurement control

message. Check whether SC128 exists in the list of intra-frequency neighbor

cells. The result is that SC128 is not in the list of intra-frequency neighbor cells,

therefore the call drop is caused by missing neighbor cell.

If only UE recorded data in the test without data from scanner, confirm by the

following method whether the problem is caused by missing neighbor cell:

Check scrambles of all cells listed in active set measured by UE before call drop

Check scramble information of the cell where UE camps again after call drop and

check whether the scrambles are in active set and monitoring set before call



drop

If yes, the call drop might be due to missing neighbor cell.

Check the list of neighbor cells

7.1.2 Removing Redundant Neighbor Cells

According to the protocol, the maximum WCDMA neighbor cells is 32. The base

cell itself is also included in the intra-frequency neighbor cell list, so the actual

intra-frequency neighbor cell is 31 at most. If there are already 31 or more

neighbor cells, adding necessary neighbor cells in optimization is difficult.

Therefore, you must remove some redundant neighbor cells.

Principles

You must be very careful to remove redundant neighbor cells. If the necessary

neighbor cells are removed, problems like call drop occur. Therefore follow the

principles below:

Before removing neighbor cells, check the revision records of neighbor cells

whether the neighbor cells to be removed are those that were added in

previous DT and optimization.

After removing neighbor cells, perform comprehensive test, including DT and

call quality test (CQT) in important indoor spots, and check for abnormalities.

If there are abnormalities, restore the data configuration.

Possible Removals

During RF optimization stage, you might remove neighbor cells in the following

situations:

Remove the neighbor cells related to cross-cell coverage on the precondition

that the cross-cell coverage problem is solved and no new weak coverage

areas are appear.

Remove neighbor cells according to experiences while referring to the

network topology structure. This applies to that the original neighbor cell list

is full and new neighbor relations must be added. Perform test after removal

and confirm that the removal does not cause bigger problems. Otherwise,

you must reselect the neighbor cells to be removed.

In the later stages, you can refer to removing traffic measurement statistics. For

details, see WCDMA Handover and Call Drop Problem Optimization Guide.

7.2 SHO Factor based on DT Analysis

7.2.1 Definition of SHO Factor based on DT

According to the DT data from scanner, you can obtain the SHO Factor based on

DT, defined as below:



DTin points collected-scanner totalofNumber

conditionshandover meet the that DTin points collected-scanner ofNumber ＝RatioHandoverSoft

No subscribers are using the network during RF optimization stage, so UE DT

data of entire network in a time is used and geographically averaged by 5 meters.

You can obtain the ratio of the points in soft handover state to all DT points. Set

the scanner consistent to the system parameters with default configuration, such

as 1A and 1B threshold.

7.2.2 General Principles and Methods in Optimization

The SHO Factor based on DT during RF optimization stage must be 5%–10%2

lower than the KPI target value, because the following optimizations cause SHO

Factor based on DT to increase and brings difficulties in ensuring traffic

measurement SHO Factor based on DT.

At the end of large-scale coverage optimization and pilot pollution optimization,

the SHO Factor based on DT will be within or close to the target range. Upon this,

no specific optimization on SHO Factor based on DT is necessary, and you can

adjust the ratio during parameter optimization. If the SHO Factor based on DT still

cannot meet the requirements after large-scale adjustment, you must optimize

the SHO Factor based on DT.

If the SHO Factor based on DT is over large, decrease or change the handover

areas by using the following methods for shrinking coverage areas:

Increase the down tilt

Adjust azimuth

Decrease the antenna height

Decrease the PICH power

The precondition for adjustment is that the adjustment will not cause new

coverage voids, coverage blind zone, and more pilot pollution.

The adjustment proceeds as below:

Start Assistant

Analyze scanner-based RSCP for 4th Best ServiceCell and RSCP for 3rd Best

ServiceCell

Select candidate cells in the 4th Best ServiceCell and 3rd Best ServiceCell

0 shows the RSCP for the candidates in 4th Best ServiceCell. List the SC136

cell as a candidate cell.

At this stage, the pilot pollution comes to an end. RSCP for 3rd Best ServiceCell

is more useful in terms of reference. Select the sites or cells to which the

2 Further research will be on how to define the range of difference of SHO Factor based

on DT between RF optimization and KPI



adjustment is applicable and does not break the preconditions. If the actual SHO

Factor based on DT after adjustment is still different from the KPI one, select

candidate cells from RSCP for 2nd Best ServiceCell. The sites are densely

distributed in microcell coverage areas, so the SHO Factor based on DT is much

higher.

RSCP for candidate of 4th Best ServiceCell



8 Adjustment Methods

The adjustment during RF optimization stage include adjusting neighbor cell list

and adjusting engineering parameters.

Most coverage and interference problems can be solved after adjusting the

following site engineering parameters (from superior to inferior):

Adjust antenna down tilt

Adjust antenna azimuth

Adjust antenna height

Adjust antenna location

Change antenna type

Add TMAs

Change site type (such as changing a site supporting 20 W power amplifier to a

site supporting 40 W power amplifier)

Change site location

Construct new site or add RRU



9 Summary

This document describes the content of RF optimization in network optimization.

RF optimization concern the improvement of signal distribution, and it helps to

provide a good radio signal environment for the following parameter optimization.

The test during RF optimization is usually DT, with other tests as supplementary.

The problems to be analyzed during RF optimization is primarily about coverage,

pilot pollution, and handover, with problem as supplementary. RF optimization

help to solve handover, call drop, access, and interference problems. The

parameters to be adjusted during RF optimization are primarily engineering

parameters. Cell parameters are adjusted during parameter optimization stage

(excluding adjusting neighbor cell list).

This document is mainly for RF optimization of new network. How to optimize an

existing network for expansion needs further tracing. The methods for optimize

SHO Factor based on DT and the judgment conditions for removing neighbor

cells are still under research, and they will be supplemented in the future

versions.



10 Appendix: Coverage Enhancement Technologies

10.1 Coverage-enhancing Technologies

10.1.1 TMAs

Using TMAs helps to reduce the total noise figure of NodeB receiver subsystem,

so the uplink coverage performance is improved. The coverage gain depends on

the mechanism of receiver subsystem and loss of related feeders. If the system

downlink capacity is restricted, using TMAs will shrink system capacity. The

typical capacity shrinkage is 6%–10%.

10.1.2 Receive and Transmit Diversity

Increase the number and improve the quality of RAKE receivers of UE by using

time switched transmit diversity (TSTD) and space and time transmit diversity

(STTD) in the downlink. Therefore the coverage range is expanded, system

capacity increases, and the number of NodeBs decreases.

Using four-antenna receiver diversity reduces requirements on Eb/No needed in

demodulation. In line of sight, compared with the gains of 2 antennas with 2

receiver diversity, the gain of 2 antennas with 4 receiver diversity is 2.5–3.0 dB.

You can adjust the uplink sensitivity by 2.5–3.0 dB and reduce the sites by

25%–30%.

10.1.3 RRU

Remote radio unit (RRU) physically detach NodeB RF module from baseband

module, so you can place RF module afar without using very long feeders. The

uplink and downlink link budget is improved. Remote RF indicates that the

coverage performance is improved but the system capacity remains the same.

Compared with remote RF, using TMAs increases maximum path loss and lowers

NodeB EIRP due to bringing insertion loss.

10.1.4 Micro Cells

NodeBs are densely distributed in urban and dense urban areas, so selecting a

site is difficult. Using micro cells is a solution to high capacity and caters for urban

and dense urban environment. A feature of using micro cells is that buildings are

used to block signals so that the interference from neighbor cells is lowered and

downlink capacity is increased.



References

[1] GENEX Probe Radio Air Interface Test Software User Manual

[2] GENEX Nastar WC MA User Manual (DCHN)

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