08-WCDMA RF Optimization(lj2kh)

8/7/2019 08-WCDMA RF Optimization(lj2kh)

1/52


2/52

1Internal Use

qThis lecture introduces the various stages involved

in optimizing a 3G radio network and focuses on

the RF Optimization phase.

qStep-by-step approach for the analysis of drive test

data collected by Scanner and test UE is

presented. The analysis is carried out using the

post processing tool ,Genex Assistant.

q In addition, as the network matures, the

optimization work should be enhanced to take intoaccount traffic statistical data and key performance

index collected throughout the network.

PDF created with pdfFactory trial version www.pdffactory.com
http://www.pdffactory.com/http://www.pdffactory.com/


3/52

2Internal Use

Chapter 1Chapter 1 Optimization PhasesOptimization Phases

Chapter 2 RF Optimization

Chapter 3 RF Optimization methods

Chapter 4 Antenna Adjustment Example

Chapter 5 Drop Call Analysis Example



4/52

3Internal Use

Network Optimization PhasesNetwork Optimization Phases Flow ChartFlow Chart



5/52

4Internal Use

Single Site VerificationSingle Site Verification

qSingle Site Verification

To verify the functionality of every site.

qObjectives

To ensure there are no faults related to site installation or

parameter settings.



6/52


7/52

6Internal Use

Chapter 1 Optimization Phases

Chapter 2Chapter 2 RF OptimizationRF Optimization






8/52

7Internal Use

RF OptimizationRF Optimization -- PreparationPreparation

q Clutters

RF optimization should be carried out for groups or clusters of

sites rather than on single site basis.

q Drive Routes

Cluster drive test should include the coverage areas of per cell

and all the main roads , streets and any other important

locations.

q Tools

DTI scanner

Huawei U626

Assistant



9/52

8Internal Use

RF OptimizationRF Optimization TargetTarget

For e1a, e1b & e1c>95 %TargetSHO Success ratioAssuming 21 dBm max.


10/52

9Internal Use

Handover parametersHandover parameters

T T T

1 A E v e n t 1 B E v e n t N o t

t r i g g e r e d

R e p o r t i n g

R a n g e

H y s t

C

B

AC P I C H

E c / N o



11/52

10Internal Use

RF OptimizationRF Optimization -- SolutionsSolutions

q

Antenna tilt

qAntenna azimuth

qAntenna location

qAntenna height

qAntenna type

qSite location

qNew site



12/52

11Internal Use



Chapter 3Chapter 3 RF Optimization methodsRF Optimization methods





13/52

12Internal Use

RF Optimization methodsRF Optimization methods

q Dominant cell analysis

q Coverage analysis (PCPICH RSCP)

q interferential analysis (PCPICH Ec/Io)

q Uplink coverage analysis

q Pilot pollution analysis

q

Neighbor cell list analysis

q SHO Performance analysis

q Call drop analysis



14/52

13Internal Use

RF Optimization methodsRF Optimization methods Dominant cell analysisDominant cell analysis

qDead zone

A site was not emitting during the drive test

Very poor coverage can also be caused by blocking of the

antenna.

qOvershoot

This could be caused to a high site or non-optimum antenna

tilts.

Overshoot will cause interference to adjacent cells resulting in

poorer capacity.



15/52

14Internal Use

RF Optimization methodsRF Optimization methods Dominant cell analysisDominant cell analysis

q

No dominant cell in some area : Areas where there is not a dominant cell and where the best

server changes frequently.

Result:

No dominant cell in some area will cause soft handover

frequently and decrease the system efficiency and increase the

probability of call drops.

q UE vs. Scanner Best Serving Cells:

Comparison between the UE and scanner PSC plots. Significant

differences between the plots may indicate a missing neighbor

problem.



16/52

15Internal Use

RF Optimization methodsRF Optimization methods



17/52

16Internal Use

RF Optimization methodsRF Optimization methods CPICH CoverageCPICH Coverage

qCheck areas of poor coverage, typical value as below:

Good: RSCP -85 dBm

Fair: -95 dBm RSCP < -85 dBm

Poor: RSCP < - 95 dBm

qCPICH Ec/Io

Good: Ec/Io -8 dB

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

Poor: Ec/Io < - 14 dB



18/52

17Internal Use


Because the RSCP Level is poor, andcause of low Ec/Io is poor coverage

Because the RSCP Level is poor, andcause of low Ec/Io is poor coverage

-15.5

-104

-20

-19

-18

-17

-16

-15

-14

Ec/Io RSCP

- 1 2 0

- 1 1 5

- 1 1 0

- 1 0 5

- 1 0 0

- 9 5

- 9 0

Whats theproblem?



19/52

18Internal Use




20/52

19Internal Use




21/52

20Internal Use

RF Optimization methodsRF Optimization methods InterferenceInterference

RSCP level is good, and thiswould imply strong systeminterference

RSCP level is good, and thiswould imply strong systeminterference

-15.5

-63

-20

-19

-18

-17

-16

-15

-14

Ec/Io RSCP

- 9 0

- 8 5

- 8 0

- 7 5

- 7 0

- 6 5

- 6 0 Whats theproblem?



22/52

21Internal Use

RF Optimization methodsRF Optimization methods UL CoverageUL Coverage

qUplink Coverage (UE Tx Power)

High UE Tx power means possible poor uplink coverage.

Areas of high uplink Tx power should be compared to the CPICH

pilots to verify if the problem only exists on the uplink.



23/52

22Internal Use

RF Optimization methodsRF Optimization methods UL CoverageUL Coverage



24/52


25/52

24Internal Use

RF Optimization methodsRF Optimization methods Pilot PollutionPilot Pollution

SC Count % in Pollution Set

8 206 12.9%

9 165 10.3%

10 157 9.8%

11 156 9.7%

12 148 9.2%

13 135 8.4%

16 95 5.9%17 94 5.9%

18 76 4.7%

19 74 4.6%

20 73 4.6%

21 56 3.5%

32 54 3.4%

35 39 2.4%

37 33 2.1%

43 19 1.2%

48 8 0.5%

53 7 0.4%

67 3 0.2%

80 2 0.1%

130 2 0.1%

Should be checked



26/52


27/52

26Internal Use

RF Optimization methodsRF Optimization methods Pilot PollutionPilot Pollution

qEstimated Active Set Size Example



28/52

27Internal Use

RF Optimization methodsRF Optimization methods Neighbor ListNeighbor List

q

Neighbor List Verification The neighbor list could be verified and optimized using the

Neighbor List Verification tool within GENEX assistant.

q Recommendations for Each Cell:

Retain: This indicates that those neighbors have been confirmed

from the drive test data.

Add: Missing neighbors

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

neighbor list.

Careful consideration is needed prior to removing neighbourssince the Actix/Assistant results are drive route dependent.



29/52

28Internal Use

RF Optimization methodsRF Optimization methods Neighbor ListNeighbor List

q Neighbor List Verification Example

009 576 Retain 018 82 14.2%Retain 010 46 8.0%Retain 016 31 5.4%Retain 032 20 3.5%Retain 011 18 3.1%Add 130 17 3.0%

Retain 021 17 3.0%

Retain 008 12 2.1%Retain 020 6 1.0%Retain 012 5 0.9%Retain 017 2 0.3%

Remove 053 0 0.0%Remove 019 0 0.0%

Remove 034 0 0.0%Remove 037 0 0.0%

Remove 013 0 0.0%Remove 051 0 0.0%

70548 Ajman Central 25.41204 55.447

Nbr SCSample

Count%Latitude Longitude

Sample

CountActionSC Cell Site



30/52


31/52

30Internal Use

RF Optimization methodsRF Optimization methods Call DropCall Drop

qCall Drop Analysis - RF related issues :

Poor coverage (RSCP & Ec/Io)

High interference and poor Ec/Io

Poor uplink coverage (insufficient UE Tx power)

Poor dominant cell (best cell changes too frequently resulting in

too many SHO events)

Pilot pollution

Missing neighbors

Fast change of RF conditions (e.g. turning a corner)



32/52

31Internal Use


qDrop Call Analysis Example 1

Call Drop

RSCP & Ec/Io degradesBOTH for scanner and UE

Check for Coverage problems



33/52

32Internal Use



Call Drop

Ec/Io (and RSCP) degrades for UEONLY while scanner shows no degradation

Ec/Io (and RSCP) degrades for UEONLY while scanner shows no degradation

UE camp on new cell immediatelyafter drop, and UE did not

measure this cell before Drop

UE camp on new cell immediatelyafter drop, and UE did not

measure this cell before Drop

Check the NeighborCheck the Neighbor



34/52

33Internal Use



Call Drop

Too many and too quick changesof best server

Too many and too quick changesof best server

UE to perform measurementsand SHO in time difficultly

UE to perform measurementsand SHO in time difficultly

Ping-Pong Handover, need to

improve cell dominance

Ping-Pong Handover, need to

improve cell dominance



35/52


36/52

35Internal Use

Antenna Adjustment ExampleAntenna Adjustment Example

qRSCP Coverage before Adjustment



37/52

36Internal Use


qRSCP Coverage after Adjustment



38/52

37Internal Use


qRSCP Distribution

CPICH RSCP Distribution

1.4

4%

20.31% 2

9.33%

30.27%

18.65%

0.0

2%

5.4

7%

25.98%

31.04%

37.48%

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

-105

to-9

5

-95t

o-85

-85t

o-75

-75t

o-65

>-65

Before Adjustment After Adjustment



39/52

38Internal Use


qTilt from 4 to 6 Result



40/52


41/52

40Internal Use





Chapter 5Chapter 5 Drop Call Analysis ExampleDrop Call Analysis Example



42/52

41Internal Use

Drop Call Analysis ExampleDrop Call Analysis Example

q Call Drop Distribution (from best server cell)



43/52

42Internal Use


qThere are total 5 drop calls in the plot.

qThe example of drop call 1 is analyzed to show the process

of analysis in the following.

qDrop call 1 occurred at an area of frequent change of best

server as shown by the scanner scrambling code plot



44/52

43Internal Use




45/52

44Internal Use


qCPICH RSCP and Ec/Io before the Call Drop

q

Compare Ec/Io from both scanner and UE at the time of the drop asshown in Figure. This clearly shows the UE Ec/Io to drop to < -21 dBwhile the scanner remained above -11 dB.

UE Ec/Io

degrades before

call drop



46/52

45Internal Use


qBest server before and after the Call Drop

1

2



47/52

46Internal Use


qComparing the best servers from the UE and the scanner at

the time of drop:

Drop Call 1 (UE vs. scanner best server) shows that for the

scanner and UE SC009 is the best server prior to the drop.

However, about 30 seconds before the drop, the scanner

selected SC018 as the best server while the UE continued to

have only SC009 in its active set resulting in the drop call.

Immediately after the drop, the UE camps on SC018.



48/52

47Internal Use


qUE Active Set and Monitor Set Before and After the Call Drop

UE

SC018

SC018 was notmeasured by UE prior tocall drop



49/52


50/52


51/52

50Internal Use


qSolution:

Looking at drop call Figure clearly shows that at the location of

the drop, SC018 should not be the best server.

Cell SC018 clearly requires some down tilting to control its

interference into the area of Drop 1. To illustrate this, RSCP

coverage of SC018 shows clearly that the cells is extending into

a large area. E.g. around the location of drop call, SC018 RSCP

is > -75dBm.


Date post:	08-Apr-2018
Category:	Documents
Upload:	ocira-oyaro
View:	226 times
Download:	0 times

08-WCDMA RF Optimization(lj2kh)

Documents