53505830 WCDMA RF Optimization Cases

8/14/2019 53505830 WCDMA RF Optimization Cases

1/120

www.huawei.com

Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.

WCDMA RadioFrequency Optimization


2/120

Page2Copyright 2007 Huawei Technologies Co., Ltd. All rights reserved.

ForewordRF (Radio Frequency) optimization is the most important

step to ensure the quality of the network.RF optimization will solve network problems related to

neighbor cell list, coverage and interference.


3/120


ObjectivesUpon completion of this course, you will be able to:

Know the steps of RF optimizationKnow how to solve the RF problems cased by neighbor cell list,

poor coverage and interference


4/120


ContentsRF Optimization Workflow

Typical Problems Analysis in RF optimization


5/120


RF Optimization WorkflowStart

Preparation:Set the optimization targetDivide the optimization clusterDraw out the test route linePrepare the DT tools

Data Collection:DT testIndoor DT testRNC configuration data

The DT result is satisfiedwith optimization target?

RF optimizationfinished

Y

Problem Analysisneighbor cell listpoor coveragepilot pollutionhandoverinterference

N

Adjustment:Engineering parameters adjustNeighbor cell list adjust


6/120


RF Optimization Workflow

5%Pilot pollutionPercentage

30%-40%SHO Percentage

Scanner result 95%CPICH RSCP

-95dBm

Scanner result

95%CPICH Ec/Io

-12dB

CPICH Ec/Io -12dB & RSCP -95dBm

95%Coverage Probability

RemarkReference

ValueTarget Item

Set RF optimization target, for example:


7/120


RF Optimization WorkflowRF optimization clusters division

Cluster is the area for one time drive test

One cluster should contains 15 to 25 sites

Cluster division should consider the following factor, such as:Terrain

Traffic

Route line


8/120


RF Optimization WorkflowPreparation for DT (drive test)

HardwareTest phoneScanner

GPS

SoftwareDrive test software, for example, GENEX Probe

Drive test post process software, for example, GENEXAssistant


9/120


ContentsPreparation of RF Optimization



10/120


ContentsTypical Problems Analysis in RF optimization

RF case related to neighbor cell listRF case related to bad coverage

RF case related to interference


11/120


Case 1Description

In DT, call drop happenedCheck the signaling trace at UE side

Call DropAfter call drop, begin

to readsystem information


12/120


Data analysis

Check cell information from UE active set and cell information

from scanner at call drop points.From ScannerFrom UE

No SC170 cell!!

Why?

Case 1


13/120


Data analysis

Checking monitor set

Missing neighbor cell

Delayed handover

Check monitor set forthe scramble measuredby scanner

SC 170 is not in monitor set

Case 1


14/120


Data analysis

Check the latest measurement control measurement control

Search for the latest intra-frequency measurement control

Call droppoint

Case 1


15/120


Measurement ID is 1. It is Intra-

frequency measurement control

Check the list of intra-frequencyneighbor cell in measurement

control and no SC 170

The primary scrambleof the cell is 6

Case 1


16/120


Solution

Add neighbor cells in neighbor cell list

Summary

In the beginning stage of network, it is very common thatmissing neighbor cell cased cause call drop.

Analysis with signaling procedure is the common way to find

and solve the problemSome problems can be avoided if the Combined Neighbor Cell

Algorithm is switched on.

Case 1


17/120


Phenomenon description

In DT, call drop

happened at cell A

Case 2

Cell B (PSC277)

Cell A(PSC58)


18/120


Phenomenon description

In Cell A, UE keeps reporting PSC 277 1A event.

RNC received this event and send Active Set Update to UE

according to the signaling trace record

UE send Active Set Update complete to RNC

Then, RNC send Active Set Update to delete PSC 277 from

active set

Finally call drop happened due to RL failure

Case 2


19/120


Problem Analysis

From the signaling trace of DT, it looks like the handover is

complete successfully.

But, according to the signaling trace from CDT, the handover

failed actually.

Case 2


20/120


Problem Analysis

Signaling trace from CDT shows:

Case 2

UE NodeB RNC

Measurement control (1A Event for PSC 227)

Radio Link Setup

Radio Link Setup Response

Active set update

Active set update complete

Radio Link Failure


21/120


Cell B (PSC277)

Cell A (PSC58)

Cell C (PSC277)Problem Analysis

After checking the

neighbor cell list, the

following problem is

found

Cell C has the same

PSC as Cell B

Case 2


22/120


277C

277B

58A

PSCCell ID

CA

AC

NCell IDCell ID

Cell B(PSC277)

Missingconfiguring

NCellMistake forconfiguring

NCell

Case 2Problem Analysis

The neighbor cell list shows

Cell C(PSC277)

Cell A(PSC58)


23/120


Problem Analysis

Based on the analysis above, the new NodeB is not the one of

cell B, but the one of cell C

Even the cell C prepared resource for UE according to the RNC

command of Radio Link Setup, it can not find the UE uplinksignal.

That does why the Radio Link Failure is sent by NodeB

Case 2


24/120


Solution

Change the wrong neighbor cell list

Case 2


25/120


Summary

Phenomenon for wrong neighbor cell listFrom DT, radio link branch is added into active set, then deleted

from active set repeatedly.

SHO success rate is lowRadio link failure is low in the wrong neighbor cell, for example, cell

C in case 2

Call drop is high in the cell with wrong neighbor cell, for example,cell A in case 2

Case 2


26/120


Summary

About SHO event, UE will only report PSC to RNC inMeasurement Report

RNC will find the right cell according to the neighbor cell list

between cell ID and PSCThis problem is mainly happened in dense urban when is PSC

is reused a lot

Case 2


27/120


DescriptionCase 3

14603 (Frequency A)

14602 (Frequency B) 14031 (Frequency B)

Inter-frequency handover based on coverage

14605 (Frequency C)

Inter-frequency handover based on capacity

Call drop rate high


28/120


Description

UE is in Cell 14602 with frequency B

When 14602 is in high load level, UE will be handed over to

14603 with another frequency A

When 14603 is in high load level, UE will be handed over to14605 with frequency C

Because frequency A and C are not used continuously at this

area, UE has to be handed over to Cell 14031 with frequency B

14603 and 14605 can share the load level, but the call drop

rate in 14603 is very high.

Case 3


29/120


Analysis

Because its difficult to do drive test for collecting signaling

trace, the IOS (Information of Subscriber) trace is used.

Based on the analysis for the call dropped UE, there is one

thing is common:Before call drop in 14603, all UEs initiated compress mode, and

send Measurement Report to RNC periodically, but handover is

not triggered.

Case 3


30/120


AnalysisCase 3

2D Event

Compressmode

Inter-frequencymeasurement

control

Inter-frequencyMeasurement

report


31/120


Analysis

Open Inter-frequency Measurement Control, the Cell 14605

with frequency C is put in the first place

And in the following measurement report, UE only report Cell

14605But the cell 14605 cell signal level is lower than -90dBm, which

can not trigger handover, till call drop.

Case 3


32/120


Analysis

Measurement Control

Case 3Cell 14605 with

Frequency C

Cell 14031 withFrequency B


33/120


Analysis

Measurement Report

Case 3

Cell 14605 withFrequency C

Cell 14605 CPICH& Ec/Io


34/120


Question

Why the handover can not be triggered?

Since the network give UE the information of cell 14605 and

cell 14031, Why UE only report cell 14605?

Did UE measure cell 14031, just not report it?Or, UE never measure cell 14031, just 14605?

Case 3


35/120


Analysis

UE report cell 14605 CPICH RSCP is 19, which is -96dBm.

After checking the RNC configuration file, this CPICH RSCP

level can not trigger inter-frequency handover

Actually, because cell 14605 and 14603 are in one sector,their signal level should be same.

Case 3


36/120


Analysis

If UE can report cell 14031, the handover may be triggered

After analyze the compress mode principle, it is found that UE

can only monitor 1 WCDMA frequency in the gap of compress

mode.

Case 3


37/120


Analysis

Because UE can not measure cell 14031 with frequency B,

only monitor cell 14605 with frequency C, and meanwhile cell

14605 and 14603 signal level are the same, the call dropped

due to the poor signal of 14605 and 14603

How to make UE monitor cell 14031 with frequency B instead

of 14605 with frequency C?

Case 3


38/120


Solution

Delete the neighbor relation from 14603 with frequency A to

14605 with frequency C

Add the neighbor relation from 14602 with frequency B to

14605 with frequency C

Case 3


39/120


SolutionCase 3

14603 (Frequency A)

14602 (Frequency B) 14031 (Frequency B)

14605 (Frequency C)

Inter-frequency handover based on coverage

Inter-frequency handover based on capacity


40/120


Summary

Do not configure two different frequency neighbor cells in

WCDMA system

Case 3


41/120


Contents


RF case related to neighbor cell list

RF case related to bad coverage



42/120


Description

In drive test for RF optimization, call drop happened in the

circle area

Case 1


43/120


Analysis

After analyze the signal level of this area, the call drop is

caused by discontinuous coverage of the cell with PSC 442

Case 1

Problem Zone


44/120


Analysis

After checking the RF

transmission

environment, the signal

is blocked by the glass

wall

Case 1

The Wall

Call drop

Antenna


45/120


Solution

Solution 1: Decrease the downtilt to increase the signal level

Maybe the problem area will become better, but due to the wall,

this problem may still exist nearby.

Solution 2:Increase the antenna height

After checking the installation condition, its very hard to increase

the height

Even increased the height, the problem may still exist due to the

wall.

Case 1


46/120


Solution

Solution 3:

Move the antenna position if possible, and the main direction

antenna is parallel with the side of the wall

Case 1

OriginalPosition

New

Position

WallMove the antenna position to

right about 15 meters

considering the installation

condition


47/120


Solution

Solution 3:

About the antenna downtilt, two strategies are designed.

First, 10 degrees

Case 1

10 Degree


48/120


Solution

Solution 3:

Second, 5 degrees

Case 1

5 Degree


49/120


Summary

Before RF adjustment, site survey should be done.

Find the problem and the reason, design several strategies for

the adjustment

One time adjustment, and check the performance at the sametime. Adjustment and performance checking should be done at

the same to improve the work efficiency.

Case 1


50/120


Description

In drive test for RF optimization, the area Ec/Io is bad

Case 2


51/120


Analysis

Checking the cell distribution at this area

Case 2

PSC185

PSC184PSC186


52/120


Analysis

One site with 3 cells, PSC184, 185 and 186 cover this area

Two cells, PSC 184 and 185, are separated to two sectors to

cover different direction

Case 2


53/120


Analysis

The area is covered by different cell PSC 184 and 185

No dominant cell PSC 184 and 185 is the best cell crossly in

this area

Case 2


54/120


Solution

Change the sector PSC, or combine some sector

Previously, 3 cells

PSC 184: sector 1 & sector 3

PSC 185: sector 2 & sector 4PSC 186: sector 5

After adjustment, 2 cells:

PSC184: sector1 & sector3

PSC185: sector4 & sector5

Delete sector 2

Case 2


55/120


After adjustment, the drive test for PSC 184 and 185

Case 2


56/120


The comparison result for scanner Ec/Io

Case 2


57/120


The comparison result for UE Ec/Io

Case 2


58/120

C 3


59/120


Description

In drive test for RF optimization, bad Ec/Io is found on the

bridge

Case 3

C 3


60/120


Analysis

Check the RSCP value of scanner, the result shows the RSCP

value is good.

Case 3

Based on this, pilot pollution

need be considered in this

area.

Check the top N pilot RSCP

and Ec/Io in scanner result


61/120

C 3


62/120


Analysis

Case 3

Site 1 Cell A

Site 5 Cell C

Site 2 Cell C Site 3 Cell C

Site 4 Cell C

Case 3


63/120


Analysis

On the bridge, the signal from different cell can cover this area

due to reflection of the river and no building.

From DT, following cell cover this area:

Site 1 cell A

Site 2 cell C

Site 3 cell C

Site 4 cell CSite 5 cell C

Case 3

Case 3


64/120


Analysis

Need to find the

best cell

Check the map,

the site 6 is very

near to the

bridge.

Case 3

Site 1 Cell A

Site 5 Cell C


Site 4 Cell C

Site 6

Case 3


65/120


Analysis

After checking site 6 RF

environment, it is difficult to

increase the antenna height or

move site 6 position to avoid

the blocking caused by the

building

Case 3

The residence buildingsare much higher thanantenna, which block

the signal of site 6

Case 3


66/120


Analysis

Then, site 1 cell

A can be the

best cell to

cover this area

Case 3

Site 1 Cell A

Site 5 Cell C


Site 4 Cell C

Case 3


67/120


Analysis

Then, try to

increase the

signal of site 1

cell A, and

decrease other

cells

To confirm this,

DT for site 1 cell

A needs to be

done

Case 3

Site 1 Cell A

Site 5 Cell C


Site 4 Cell C

Case 3


68/120


Solution

Increase the signal of site 1 cell A

Change the antenna downtilt from 10 to 7

Increase CPICH Tx power 1.5 dB higher

Decrease other cell signal change the antenna downtilt

From 7 to 10 for site 2 cell C

From 5 to 8 for Site 3 cell C

From 9 to 11 for site 4 cell CFrom 9 to 11 for site 5 cell C

Case 3

Case 3


69/120


Confirmation

After the modification, the DT shows the pilot pollution area

as below

Case 3

Case 3


70/120


Confirmation

The Ec/Io comparison

Case 3

After

Before

Case 3


71/120


Summary

To solve the pilot pollution, the following issues has be

considered

Find the reason caused pilot pollution

Due to no strong signal

Due to too much strong signal

After the adjustment, the DT has to be done at this cluster to

confirm that no new problem appeared

Case 3

Case 4


72/120


Description

In DT, video call quality is decreased at the problem

area. Also, the PS call drop happened several times

Case 4

Problem Area

3G Antenna

2G Antenna

Case 4


73/120


Analysis

RSCP distribution in DT

Case 4

Problemarea

Case 4


74/120


Analysis

Ec/Io distribution in DT

Case 4

Problemarea

Problemarea

Case 4


75/120


Analysis

Checking the RF environment, the antenna is installed on 10-

meter platform

2G and 3G antenna are installed at one platform, but 3G

antenna is a little bit inner than 2G antenna.

After finishing DT in 2G, signal level is very stable

Case 4


76/120


Analysis

If 3G and 2G antenna are installed at the same place, the

problem may be solved.

Problem Area

3G Antenna

2G Antenna

The short wall of this

platform may block

the signal of 3G

Since 2G antenna is

near to the border, the

wall influence 2G little

Wall

Case 4


77/120


Solution

Solution 1

Increase the antenna height can solve this problem

Solution 2

Move the installation place near to the border

Solution 3

3G and 2G use the same place

Case 4


78/120


Solution

Solution 3 is adopted

Road

RX

RX

T

X/

RX

T

X/

RX

2G

BTS

3G

NodeB


79/120

Case 4


80/120


Summary

Sharing the same installation place for 3G and 2G is

very common, and several strategies can solve the

problem

In this situation, 3G and 2G can share the feeder

system, or can only share the installation platform.

Considering the factors of the installation and related

resource, a easiest and simplest method should be

adopted

Case 5


81/120


Description

In DT, call drop happened a lot in the area

Case 5


82/120


Description

Check the DT information, SC304 is in active set with

the signal level RSCP -76dBm and Ec/Io -18

Analysis

Consider the pilot pollutionBut only 1 cell in active set and 1 Cell in monitor set

Consider the missing neighbor cell

But the cell in monitor set has very good quality

RSCP -65dBm and Ec/Io -6

Case 5


83/120


Analysis

Check the signaling trace at UE sideBefore call drop, UEsends measurement

report to RNC with 1Aevent for cell 298

Case 5


84/120


Analysis

Check the signaling trace at RNC side

RNC sent Active Set Update toUE, but no response. Then, RNCsend release RRC connection

Call Drop

Case 5


85/120


Analysis

Based on the DT and signaling trace, this call drop

can be take as handover failure

For example

cell56 vs cell041

-30

-20

-10

0

time

E c

N o cell56

cell041

Case 5


86/120


Analysis

Around the corner, the original cell 304 signal level

drop very quickly because of the building

shadowing, and the neighbor cell 298 increase

very quickly.

After UE sent measurement report to RNC, cell

304 has become very bad when RNC sent active

set update.

Case 5


87/120


Adjustment

Since cell 298 has better coverage at this area,

handover can happen earlier

Decrease the coverage performance at this area Increase the downtilt from 5 to 9

Adjust the direction from 0 to 310

Increase the coverage performance at this area

Decrease the downtilt from 5 to 4

Adjust the direction from 300 to 270

Case 5


88/120


Adjustment

Result after adjustment

Handoverarea

HandoverareaBefore After

Case 5


89/120


Adjustment

Comparison of Ec/Io of UE

Before After

Case 5


90/120


Summary

Confirm the corner effect by analyzing signaling

trace at UE and RNC

About corner effect, Taking the method make the

handover happen earlier, such as RF optimizationOther method can also adopted

Modify 1A event

Modify CIO (Cell Individual Offset)

Contents


91/120



RF case related to neighbor cell list

RF case related to bad coverage


Case 1


92/120


-105.4-101.6-822006-5-16 17:00KwongYu3625031

-105.5-94.89-74.32006-5-16 17:00KwongYu2625021

-105.3-102.34-74.52005-5-16 17:00KwongYu1625011

VS.MinRTWPVS.MeanRTWPVS.MaxRTWPTime(As hour)CellNameCellIdRNCId

Description

From traffic statistic, the following RTWP problem is found

Case 1


93/120


Analysis

Connect to the problem NodeB, and monitor the RTWP

Cell 62501 RTWP

Case 1


94/120


Analysis

Cell 62502 RTWP

Case 1


95/120


Analysis

Cell 62503 RTWP

Case 1


96/120


Analysis

The main diversity antenna is interfered seriously

Can not find any relation between interference and time,

and the interference appears randomly

Check the neighbor site, no interference

Deduction

Inter-modulation cause the interference, could be

Inter-modulation caused by bad connectorsInter-modulation by GSM

Case 1


97/120


Analysis

Check the RF environment

Case 1


98/120


Analysis

Check the RF environment

No blocking or any reflection due to the glass wall

The site RF condition is very good

Case 1


99/120


Analysis

2G and 3G share the feeder system

Case 1


100/120


Analysis

Check 2G frequency planning

Sector 1 544 with hopping frequency 821

544 1811.6MHz & 821 1867MHz


538 1808.6MHz & 821 1867MHz


858 1874.4MHz & 821 1867MHz

Case 1


101/120


Analysis

Calculate the third order intermodulation

Cell 1 1922.4MHz

Cell 2 1925.4MHz

Cell 3 1859.6MHz

Check cell 2 uplink interference

The interval of 2 interference is

821-544

Case 1


102/120


Analysis

Conclusion

The third intermodulation of cell 1 and cell 2 is just in WCDMA

uplink band

Case 1


103/120


Solution

Change the hopping frequency of DSC

Confirmation

Check the RTWP again, the values are normal

Case 1


104/120


Summary

Characteristics of inner system interference

The RTWP result are not same at the main and diversity antenna

The amplitude of interference is big, and the difference is more than 10

dB

High RTWP will appear in a duration, and will not change so frequentlyHigh RTWP will not show in a certain time each day, but randomly

Case 2


105/120


Description

In a commercial network of country U, the following RTWP

problem is found from traffic statistic

-105.65-92.65-97.722005-11-15 2:00Pocitos_C11643201

-104.65-96-97.12005-11-15 20:00Palacio_C11461201

-105.65-91-96.742005-11-15 0:00Ciudad Vieja_C11623201

-97.65-93.65-96.622005-11-15 17:00Centro_C11932201

-105.66-87.65-95.862005-11-15 4:00Centenario_C11942201

-105.66-88.65-93.942005-11-15 4:00Aguada_C11912201

RTWP_MINRTWP_MAXRTWP_MEANTime(As hour)CellNameCellIdRNCId

Case 2


106/120


Analysis

Connect to the problem NodeB, and monitor the RTWP

Take one site as example

Case 2

A l i


107/120


Analysis

The main and diversity antenna have the same

interference trend

The different between main and diversity is less than

10dB

Case 2

A l i


108/120


Analysis

Check the location of the sites with high RTWP

High

Medium

Low

Case 2

A l i


109/120


Analysis

All the problem cells are in the third sector of the NodeB,

and the direction is to the northwest

Many cells at this area show high interference, and the

cells with low RTWP are at low place

Case 2

Analysis


110/120


Analysis

Analyze the RTWP in the nearly one month, the

interference shows randomly, but if appears, usually onewhole day, or several days

The interference shows with high traffic, and also with

low traffic. No evidence shows it is related to the traffic

Case 2

Analysis


111/120


Analysis

Maybe the interference comes from outside and the

northwest direction

Case 2

Analysis


112/120


Analysis

Use YBT250 to do the interference checking

Case 2

Analysis


113/120


Analysis

All the test results show the interference comes from the

same direction to the country A

But the distance to country A from the test place is

around 50Km to 200Km

Case 2

Analysis


114/120


Analysis

Frequency analysis

U Country UMTS frequency

1900MHz

A country GSM frequency

1900MHz

Case 2

Analysis


115/120


Analysis

Maybe the interference comes from A country, but looks

like impossible because the distance (50 to 200Km) isbeyond the transmission

To confirm this problem, use A country cell phone at the

area with high RTWP

The result shows the phone does receive the A country

DSC

Case 2

Conclusion


116/120


Conclusion

The interference comes from A country GSM

Even the distance is very far, the area between the

border is covered by a large water area

Due to reflection the water, the signal can be transmitted

far away

Case 2

Conclusion


117/120


After known the reason, the following character of this

kind of interference is foundRelated to the weather

Rain day, no interference

Cloudy day, less interference Sunny day, high interference

Related to the seasons also

Problems show at Summer more than Winter

Case 2

Summary


118/120


y

Characteristics of external interference

The RTWP result are same at the main and diversity antenna

The amplitude of interference is small, and the difference is less than 10

dB

The interference exists at large area, not just one cell, also including

neighbor cells

The direction of external interference is obvious

The cell with high antenna is easier to be interferenced

Summary

RF optimization


119/120


Neighbor cell list optimization

Coverage performance optimization

Interference optimization


120/120

Thank youwww.huawei.com

Date post:	04-Jun-2018
Category:	Documents
Upload:	yass-rami
View:	234 times
Download:	3 times

53505830 WCDMA RF Optimization Cases

Documents