owo300040 wcdma coverage problem analysis issue1.00

5/20/2018 OWO300040 WCDMA Coverage Problem Analysis ISSUE1.00

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www.huawei.com

Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.

WCDMA Coverage

Problem Analysis


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Foreword

The coverage problem is common in WCDMA radio network

optimization. In this course, we will discuss how to find and

resolve the WCDMA coverage problems.

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Contents

1. Classification Of Coverage Problem

2. Coverage Optimization Flow

3. Case Analysis

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Classification Of Coverage Problem

Weak coverage

Coverage holes

Cross-cell coverage

Pilot pollution

Imbalanced between uplink and downlink

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Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved. Page5

Weak Coverage

Pilot signal is lower than the minimum access threshold of

UE. For example, RSCP threshold is -115dBm, and Ec/Io

threshold is -18dB

Solution

Adjust antenna for increasing coverage

Use RRU, repeaters or leakage cable

Construct a new NodeB

Use indoor distributed coverage system


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Coverage Holes

Pilot signal is higher than the minimum access level but

lower than the request of the services (voice, video phone

PS64 etc.)

Solution:

Adjust antenna for increasing coverage

Use RRU (Radio Remote Unit), repeater or mini site

Adjust the Max Radio Link power for the services


7/54Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved. Page7

Cross-Cell Coverage

Coverage areas of some NodeB are beyond the planned

range, and forms pilot areas satisfying full-coverage

services in coverage areas of other NodeBs.

Solution

Adjust tilt angel and azimuth of antenna

Avoid antenna propagation directed to the road

Adjust pilot power, and reduce coverage areas of NodeB



Pilot Pollution

Multiple pilot signals are received in one point, but there is no

primary pilot strong enough

Judgement

There are more than 3 cells

Pilot signal level CPICH_RSCP>-95dBm

(CPICH_RSCP1st- CPICH_RSCP4th)



Imbalanced between Uplink and Downlink

Uplink coverage is limited:

Transmit power of UE is maximum but cannot meet uplink

BLER requirements

Due to uplink interference

Downlink coverage is limited:

Transmit power of downlink dedicated channel code is

maximum but cannot meet downlink BLER requirements

Due to downlink interference


10/54Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.

Contents



3. Case Analysis

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Contents


2.1 Optimization Target in Different Stage

2.2 Preparation for Optimization

2.3 Coverage Data Analysis


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In Single Site Verification Stage

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Focus on:

Weak Coverage

Coverage Holes

Check whether the coverage area of cell is consistent with

planning


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In RF Optimization Stage

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Focus on:

Cross-Cell Coverage

Pilot pollution

Check:

Interference:

RTWP in uplink

RSSI measured by Scanner and UE in downlink

Ec/No with and without cell load

RSCP: Whether RSCP is strong enough


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In Parameter Optimization Stage

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Focus on:

Soft Handover Ratio

Too high soft handover ratio results in capacity limitation

Typical soft handover ratio: 30%~40%

Performance KPI

Whether the traffic distribution is consistent with planning


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Contents






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Preparation

Site Distribution, Site Configuration,Antenna Configuration

Pilot Prediction, Service Distribution

PlanningResult

Drive Test Tool

Performance Management tool

Signaling Analysis ToolAnalysis Tools

CPICH PowerMax FACH Power

Sintrasearch etc.

ConfigurationParameters


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Planning Result

Knowing planning result is important for coverage problem

analysis

Including

Site Distribution

Site Configuration

Antenna Configuration

Pilot Prediction

Service Distribution

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Analysis Tools

Including

Drive Test Tools, such as Genex Probe and Genex Assistant

Performance Management tool, such as iManager PRS

Signaling Analysis Tool, such as LMT

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Configuration Parameters

The radio configuration parameters to be adjusted for

solving coverage problems include

CPICH TX Power

MaxFACHPower

QqualminQrxlevmin

SintrasearchSintersearchSsearchrat

PreambleRetransMax

IntraFILTERCOEFIntraCellIndividualOffset

RLMaxDLPwrRLMinDLPwroriented to service

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PCPICHPower

Parameter name: PCPICH transmit power [0.1dBm]

Recommended value: 330, namely 33dBm

MaxFachPower

Parameter name: Max transmit power of FACH [0.1dB]

Recommended value: 10, namely 1dB

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Qqualmin

Parameter name: Min quality level

Recommended value: -18, namely -18dB

Qrxlevmin

Parameter name: Min Rx level

Recommended value: -58, namely -115dBm

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IdleSintrasearch

Parameter name: Intra-freq cell reselection threshold for idle

mode

Recommended value: 127, namely none

ConnSintrasearch

Parameter name: Intra-freq cell reselection threshold for

connected mode



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IdleSintersearch

Parameter name: Inter-freq cell reselection threshold for idle

mode


ConnSintersearch

Parameter name: Inter-freq cell reselection threshold for

connected mode



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SsearchRat

Parameter name: Inter-RAT cell reselection threshold



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PowerRampStep

Parameter name: Power increase step


PreambleRetransMax

Parameter name: Max preamble retransmission

Recommended value: 20


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FilterCoef

Parameter name: Intra-freq meas L3 filter coeff

Recommended value: D3, namely K=3

CIO

Parameter name: Cell oriented Cell Individual Offset


CIOOffset

Parameter name: Neighboring cell oriented CIO


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RlMaxDlPwr/RlMinDlPwr

Parameter name: RL Max/Min DL TX power

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ServiceRL Max Downlink Transmit

Power (dB)

RL Min Downlink

Transmit Power (dB)Downlink SF

CS Domain

12.2 kbps AMR -3 -18 128

28 kbps -2 -17 64

32 kbps -2 -17 64

64 kbps 0 -15 32

PS Domain

8 kbps -8 -23 128

32 kbps -4 -19 64

64 kbps -2 -17 32

144 kbps 0 -15 16

256 kbps 2 -13 8

384 kbps 4 -11 8


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Contents






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Coverage Data Analysis

Downlink Coverage

Analysis

RSCP

Dominant Cell

Comparison between UE

and Scanner

DL Tx Power Distribution

Soft Handover Ratio

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Uplink Coverage Analysis

Uplink Interference (RTWP)

UE Tx Power


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Downlink Coverage Analysis

RSCP Analysis

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The RSCP is lower than -95dBm

Coverage

hole


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Dominant Cell Analysis

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Dominant cell

changes frequently,

No Dominant Cell


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Comparison between UE and Scanner

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UE

Scanner

Boundary of cells are

shown more clearly by

Scanner than UE


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DL Tx Power Distribution

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Soft Handover Ratio

Soft Handover Ratio is defined by Drive Test:

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PointsofNumber

CriterionSHOeSatisfy thwhichPointsofNumberRatioHandoverSoft


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Soft Handover Ratio

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Number of Points

which are used to get

SHO Ratio

Pilot Pollution


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RTWP Analysis

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UE Tx Power

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Red Point shows the

UE Tx Power is higher

than 20dBm


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KPI Analysis

Coverage problem affects:

RRC Setup Successful Rate

RAB Setup Successful Rate

Call Drop Rate

Handover Successful Rate

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Contents



3. Case Analysis

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Case 1

From drive test, the RSCP in the blue circle is lower than -90dBm,which means the weak coverage

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Weak

Coverage


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Case 1

The simulation shows that signal in some zones is bad

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Weak

Coverage

If the distance between the

site is low, the RSCP is

more than -80dBm


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Case 1

The distribution of the sites is not density proportional:

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Smallest site

distance: 0.62km

Largest sitedistance: 1.37km


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Case 2

After swap, the uses complain the mobile cannot camp on

3G, and the distance between complaint point and site is

2km

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Case 2

Possible reasons:

Hardware fault

Installation fault, such as high VSWR

Engineering parameter fault

Cell Parameters fault, such as improper PCPICH power

There is no alarm, and VSWR is normal

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Case 2

The site of 3G_Westfort_NGA is built on the mountain, and

the height is 60meter

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3G_Westfort_NGA,

the SC of the 1st

Sector Cell is 138

Drive test result of

SC138

Mountain


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Case 2

The downtilt of Cell SC138 is set as 6 in engineering

parameter table

Check the tilt configuration in NodeB :

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Current Tilt is set as 6,

which means 0.6


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Case 2

Modify the Tilt from 6 to 60, the problem is resolved.

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Case 3

The RRC Setup Success Ratio of the following 2 cells are

around 92%:

Checking the relative counters, most of the RRC failure is

indicated with the counter RRC.FailConnEstab.NoReply

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Cell

ID

VS.RR

C.FailC

onnEstab.Cell

VS.RRC

.AttCon

nEstab.Cell

VS.RRC

.Rej.RL.

Fail

VS.RRC

.Rej.AA

L2.Fail

VS.RRC

.Rej.Po

wer.Cong

VS.RRC

.Rej.UL.

CE.Cong

VS.RRC

.Rej.DL.

CE.Cong

VS.RRC

.Rej.Co

de.Cong

VS.RRC

.Rej.Oth

er.Cong

RRC.Fai

lConnE

stab.NoReply

2242 2025 28361 0 0 0 18 0 0 0 2007

2722 1908 21414 0 0 0 0 0 0 0 1908

Cell RRC Setup Success Ratio

2242 92.86

2722 91.09


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Case 3: Analysis

Usually the counter RRC.FailConnEstab.NoReply is caused bythe weak coverage

Checking the IOS data, the Ec/No of most RRC requests are low.

This is the reason that NoReply from UE for RRC Connection

Setup

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Case 3: Analysis

Checking the states of neighbour cells: some WCDMA cell

are not activated yet, so the UEs located in other cells camp

on the Cell2242 and Cell2722

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Case 3: Solution

Modify the parameters of inter-RAT cell reselection to make

UE easier to reselect to 2G cell:

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Parameters Default Value Modified Value

Qqualmin -18dB -16dBQrxlevmin -115dBm -101dBm

SsearchRat 4dB 2dB


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Case 3: Result

After Modification, the RRC Connection Setup SuccessfulRate improved:

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Summary

In this course, we have discussed coverage relatedproblems:

Classification Of Coverage Problem

Weak coverage

Coverage holes

Cross-cell coverage

Pilot pollution

Imbalanced between uplink and downlink

Coverage Optimization Flow

Case Analysis

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owo300040 wcdma coverage problem analysis issue1.00

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