Training wcdma rf optimization gsm to umts

HUAWEI TECHNOLOGIES CO., LTD. HUAWEI Confidential

Internal

www.huawei.com

WCDMA RF Optimization Process

GSM-to-UMTS Training Series V1.0

PDF 文件使用 "pdfFactory Pro" 试用版本创建 ÿ www.fineprint.com.cn

http://www.huawei.com

http://www.fineprint.com.cn


Page 1

Revision History

Cheng Fangyuan

The notes on major concepts are added in P10.The notes on the optimization process are added in P9.The concept of pilot pollution is added in P36.“Optimization principles for soft handover” is added in P41.

1.12009-01-12

Liu NanchuanThe notes are added in P20 and P22.1.2

2009-01-20

Gao BoFirst draft is completed.1.02008-12-31

AuthorDescriptionVersionDate




Page 2

As a phase in network optimization,

RF optimization is to optimize radio

frequency (RF) signals. RF optimization

can control the pilot pollution and soft

handover ratio in the drive test while

optimizing the signal coverage, thus

ensuring normal distribution of radio

signals before service parameters are

optimized.

PDF 文件使用 "pdfFactory Pro" 试用版本创建 www.fineprint.com.cn



Page 3

l Upon completion of this course, you

will be able to familiarize yourself with

the following contents:

[Position of RF optimization in the

entire optimization process

[Specific process for RF

optimization

[Troubleshooting for RF

optimization




Page 4

References

l W-RF Optimization Guideline

l W-Handover and Call Drop

Optimization Guideline

l W-Interference Processing

Guideline




Page 5

Chapter 1 Network Optimization

Process

Chapter 2 Overview of RF

Optimization Process

Chapter 3 RF Troubleshooting

Chapter 4 RF Optimization Cases




Page 6

New site access

Single site verification

Cluster of sites ready?

RF optimization

Service test and parameter optimization

Optimization objectives reached?

N Y Y

N

Network Optimization Flowchart

Optimization end




Page 7

Network Optimization Processl Single site verification

As the first phase of the optimization, the single site verification is to test the

functions of each new site. The objectives of the single site verification are to

ensure correct site installation and parameter configuration.

l RF optimization

Once the installation and verification of all the sites in the planned area are

complete, RF (or cluster) optimization starts immediately. As one of main

phases in network optimization, RF optimization can control the pilot pollution

and soft handover ratio in the drive test while optimizing the signal coverage,

thus ensuring normal distribution of radio signals before service parameters are

optimized. RF optimization covers the optimization of the hardware of the

antenna system and the list of neighboring cells. When RF optimization is

tested for the first time, all the cells in the area should be traversed as much as

possible to rectify hardware faults.




Page 8


Process








Page 9

RF Optimization Flowchart

PDF 文件使用 "pdfFactory Pro" 试用版本创建睆¿ www.fineprint.com.cn



Page 10

Objectives of RF OptimizationlRF optimization is to solve the problems such as signal coverage, pilot pollution, and soft handover ratio in the drive test. In practice, however, carriers have different KPI requirements, index definitions, and considerations. Therefore, the objectives of RF optimization should be to meet the requirements of coverage and handover KPIs in contracts (commercial office) or planning reports (pilot office) and the indexes should be defined according to the requirements of contracts.

≤5%Pilot pollution ratio

The soft handover ratio in the RF optimization phase should be 5% to 10% lower than the target value. This is because the later optimization will cause a rise of soft handover ratio.

30%-40%Soft handover ratio

Test result from the Scanner, with no service carried outdoors≥ 95%CPICH RSCP ≥ -95 dBm

Test result from the Scanner, with no service carried outdoors≥ 95%CPICH Ec/Io ≥ -12 dB

Perform test on the acceptance route that should not cover any area without coverage.The downlink CPICH Ec/Io of the planned full-coverage service is greater than or equal to -12 dB and the downlink CPICH RSCP is greater than or equal to -95 dBm.

≥95%Coverage ratio

RemarksReference

ValueAcceptance Item

PDF 文件使用 "pdfFactory Pro" 试用版本创建 Ý www.fineprint.com.cn



Page 11

Cluster division in a project

Preparations for RF Optimization

lDivide clusters and ensure that all the sites in clusters are working

Considering the characteristics of the UMTS system, for example, the coverage and capacity affect each other and the frequency reuse factor is 1, RF optimization should be implemented on the basis of a group of or a cluster of sites instead of a single site. In this way, the interference from an intra-frequency neighboring cell is also considered in RF optimization. Before adjusting a site, you must analyze the effect of the adjustment on neighboring sites in detail.




Page 12


l Determine the test route

[Before the drive test, you should determine the test route with

the customer. The test route should cover the route predefined

by the customer. If the route predefined by the customer cannot

be covered, you should notify the customer of the information in

time.

[The KPI test route is a core one in the test route of RF

optimization, and its optimization is a core task in RF

optimization. In addition, the test route should also cover main

streets, important places, and VIP/VIC.




Page 13


l Test route in a project




Page 14

Preparations for RF OptimizationArrange for test tools

Before RF optimization, you should arrange for necessary software, hardware, and documents to ensure smooth test and analysis. The preparations are listed as follows:

1. Software

Map display and route data makingMapinfo4

Performance analysis, health check, and problem locationGenex Nastar3

DT data analysis and neighboring cell checkGenex Assistant2

Drive testGenex Probe1

RemarksFunctionNameNo.




Page 15


Arrange for test tools

2. Hardware

DC converted to AC, more than 300 W

Vehicle-mounted inverter4

PM1.3G/512M/20G/USB/COM/PRNPortable PC3

At least two test terminals

U626, Qualcomm, and so onTest terminal and data cable2

DTI ScannerFrequency scanner1

RemarksContentEquipmentNo.




Page 16


Arrange for test tools

3. Documents

Used for indoor testYesPlan of floors to be tested7

NoChecklist for single site verification6

NoSite survey report5

YesNetwork configuration parameters4

YesKPI requirements3

Mapinfo or printed documentYesMap2

YesEngineering parameter table1

RemarksMandatoryDocumentNo.




Page 17


Process








Page 18

Chapter 3 RF

Troubleshooting

3.1 Coverage Analysis

3.2 Pilot Pollution

Analysis

3.3 Handover Analysis




Page 19

Coverage Analysis

l As a major content in RF optimization, coverage analysis focuses on signal distribution.

Classification of coverage problems:

l Poor coverage

l Cross coverage

l Uplink and downlink unbalance

l Area without dominant cell




Page 20

Poor Coverage

lConcept: The RSCP of pilot signals in the coverage area is smaller than -95 dBm.

lEnvironment: valley, mountainside back, elevator shaft, tunnel, underground garage, basement, inside of a high building, and so on.

lConsequence: Full-coverage services are difficult to access the network; the call drops; the UE cannot camp on a cell and even drops from the network due to failure to initiate location update and location registration requests.

Countermeasures:

lIncrease the pilot power, adjust the azimuth and tilt of the antenna, raise the antenna, and replace the antenna with an antenna with a higher gain to optimize the coverage.

lAdd new BTSs or increase the coverage of neighboring BTSs to extend the overlapped coverage between two BTSs and ensure an appropriate soft handover area. (Note that co-channel interference and adjacent-channel interference may be caused after the coverage is increased.)

lAdd new BTSs or RRUs to extend the coverage.

lUse the solutions such as the RRU, indoor distribution system, leaky cable, and directional antenna.




Page 21

Cross Coverage

lConcept: The area covered by a BTS exceeds the planned scope and discontinuous dominant areas are formed in the areas covered by other BTSs.

lEnvironment: hills and areas along roads and harbors

lConsequence: handover failure and “island” effect

Countermeasures:

lDo not have the antenna face the road or use surrounding buildings or other obstacles to decrease the cross coverage. (Note that co-channel interference with other BTSs may be caused.)

lFor a BTS that is located at a high place, replace the site address, adjust the pilot power, or use an RET antenna to decrease the coverage and eliminate the “island” effect.




Page 22

Uplink and Downlink Unbalance

lConcept: In the target coverage area, the uplink coverage of the symmetrical service is poor (the requirements of the uplink BLER cannot be met even if the transmit power of the UE reaches a maximum value), or the downlink coverage is poor (the requirements of the downlink BLER cannot be met even if the code transmit power of the downlink DCH reaches a maximum value).

lConsequence: The call is easy to drop due to poor uplink coverage.

Countermeasures:

lFor the uplink and downlink unbalance caused by uplink interference, monitor the RTWP alarm of the BTS to check whether the interference exists. For details, see the W-Interference Processing Guideline.

lFor poor uplink coverage, add a TMA.

lFor poor downlink coverage, adjust power settings if the capacity is sufficient, or replace the power amplifier with a larger one.




Page 23

Area Without Dominant Cell

lConcept: There is no dominant cell or the dominant cell changes frequently in the area.

lConsequence: Frequent handover occurs; the system efficiency falls; the call is easy to drop.

Countermeasures:

lFor the area without dominant cell, adjust the tilt and azimuth of the antenna to increase the coverage of a cell with good signals (or a near cell) and decrease the coverage of other cells with poor signals (or far cells).




Page 24

Questions

l Summarize the reasons, environments, phenomena, and countermeasures of coverage problems.

l What factors should be considered in planning to ensure smooth optimization?




Page 25

Process for Coverage Analysis

Downlink coverage analysis

Downlink coverage analysis is to analyze the CPICH RSCP obtained in the drive test. The quality standard of the CPICH RSCP should be defined on the basis of the optimization standard. Assume that the optimization standard of the CPICH RSCP is as follows:

The proportion of the CPICH_RSCP greater than or equal to -95 dBm is greater than or equal to 95%.

According to the test result from the Scanner with no service carried outdoors, the quality standard is defined as follows:

l Good: CPICH_RSCP ≥ -85 dBm

l Fair: -95 dBm ≤ CPICH_RSCP < -85 dBm

l Poor: CPICH_RSCP < -95 dBm

Analysis methods:

1. Analysis of pilot coverage intensity

2. Analysis of a dominant cell

3. Analysis of the coverage comparison between the UE

and Scanner




Page 26

Analysis of Pilot Coverage Intensity

RSCP for 1st Best ServiceCell




Page 27

Analysis of a Dominant Cell

l The analysis of a dominant cell is to analyze the cell

scrambling code information obtained in the drive test.

l The contents to be checked are as follows:

1. Cell with poor coverage

2. Cell with cross coverage

3. Area without dominant cell




Page 28

Area Without Dominant Cell

SC for the 1st Best ServiceCell




Page 29

Analysis of Coverage Comparison Between the UE and Scanner




Page 30

Process for Coverage Analysis

Uplink coverage analysis

Uplink coverage analysis is to analyze the UE Tx Power obtained in the drive test. The quality standard of the UE Tx Power should be defined on the basis of the optimization standard. Assume that the optimization standard of the UE Tx Power is as follows:

The proportion of the UE Tx Power smaller than or equal to 10 dBm is greater than or equal to 95%.

Assume that the maximum transmit power of the UE is 21 dBm, according to the test result of the voice services on the UE, the quality standard is defined as follows:

l Good: UE_Tx_Power ≤ 0 dBm

l Fair: 0 dBm < UE_Tx_Power ≤ 10 dBm

l Poor: UE_Tx_Power > 10 dBm

Analysis methods:

1. Analysis of uplink interference

2. Distribution of uplink transmit powers of the UE




Page 31

Distribution of Uplink Transmit Powers of the UE

UE Tx Power is too high.




Page 32

Chapter 3 RF

Troubleshooting


3.2 Pilot Pollution

Analysis





Page 33

Definition and Decision Standard of the Pilot Pollution Definition: There are too many strong pilots at a point, but the point lacks a

dominant pilot that is strong enough.

When the following conditions are reached, the pilot pollution occurs at the point:

The number of pilots with CPICH_RSCP greater than ThRSCP_Absolute is greater than ThN.

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

If ThRSCP_Absolute = -100 dBm, ThN = 3, and ThRSCP_Relative = 5 dB,

the decision standard of the pilot pollution is as follows:

l 1. The number of pilots with CPICH_RSCP greater than -100 dBm is greater than three.

l 2. The difference between the strongest pilot and weakest pilot is smaller than 5 dB.

l When conditions 1 and 2 are both reached, the pilot pollution occurs.




Page 34

Causes and Impact

l Causes

[The layout of cells is improper.

[The position of the BTS or the height of the antenna is too

high.

[The azimuth of the antenna is set improperly.

[The tilt of the antenna is set improperly.

[The pilot power is set improperly.

[The coverage area is affected by the environment.




Page 35

Causes and Impact

l Impact

When the pilot pollution occurs, the following problems may be

caused:

1. Ec/Io decrease

2. Handover call drop

3. Capacity decrease




Page 36

How to Rectify Pilot Pollution

1. Adjust the antenna

2. Adjust the pilot power

3. Use the RRU or micro cell

PDF 文件使用 "pdfFactory Pro" 试用版本创建詺 www.fineprint.com.cn



Page 37

Chapter 3 RF

Troubleshooting


3.2 Pilot Pollution

Analysis





Page 38

Handover Analysis

In the RF optimization phase, the related handover problems can be

solved through optimizing neighboring cells and controlling the soft

handover ratio. You can control the size and location of a handover

area through adjusting RF parameters to decrease the call drop due

to sharp changes of signals and improve the handover success ratio.

For analysis of other handover problems, see the W-Handover and

Call Drop Optimization Guideline.




Page 39

Neighborhood Optimization

The optimization of neighboring cells covers two cases: adding a neighboring celland deleting a neighboring cell.

l Missed configuration of a neighboring cell: When a cell with strong signals does

not join the active set, the interference rises and even the call drops.

l Redundant neighboring cell: When there are too many messages of neighboring

cells, signaling overheads are increased greatly and a required neighboring cell cannot be added when neighboring cells are fully configured.

In the RF optimization phase, the missed configuration of a neighboring cell is a

major consideration. The specific analysis methods are follows:

1. Analysis based on the DT result

2. Analysis based on Scanner data

3. Analysis based on UE data




Page 40

Analysis of Soft Handover Ratio

Definition of soft handover ratio

According to the DT data collected on the Scanner, you

can obtain the soft handover ratio. The soft handover

ratio is defined as follows:

Soft handover ratio = Number of points matching handover

conditions collected on the Scanner in the DT / Total

number of points collected on the Scanner in the DT




Page 41

Analysis of Soft Handover Ratio

Optimization principles for soft handover:

1. The soft handover ratio in the RF optimization phase should be 5% to 10% lower

than the target KPI value.

2. If the large-scale coverage optimization and pilot pollution adjustment are complete,

and the soft handover ratio approximates to the target value, you do not need to

specially optimize the soft handover ratio and only need to properly adjust related

parameters in the parameter optimization phase.

3. If the soft handover ratio is too large, you should shrink the coverage area to

decrease or change the soft handover area. You should ensure that the

adjustment does not expand the existing area with poor coverage, cause a new

area with poor coverage, or cause more pilot pollutions.




Page 42


Process








Page 43

Chapter 4 RF Optimization

Cases

4.1 Cases for Coverage

Problems

4.2 Cases for Pilot Pollution

4.3 Cases for Missed

Neighboring Cell

Configuration




Page 44

Improper Settings of Engineering Parameters Cause Poor Coverage

Symptom: Coverage near Xiajiao Sugar Refinery (before optimization)




Page 45


Analysis

The RSCP of the pilot in the area in a red circle is smaller than -95

dBm, indicating poor coverage. In the area, the call may drop.

As shown in the figure in P44, the area is mainly covered by cell B

of Xiajiao Sugar Refinery and partially covered by cell A of Materials

Building. The first consideration is to adjust the two cells to enhance

the coverage in the area. According to the site survey report, cell A

of Materials Building is facing high buildings. In this case, the

problem cannot be solved through adjusting the antenna in the cell.




Page 46


lAdjustment measures: Keep the antenna parameters in cell A of Materials Building unchanged and adjust the antenna azimuth in cell B of Xiajiao Sugar Refinery from 170° to 165° and the tilt from 10° to 8°.

Coverage near Xiajiao Sugar Refinery (after optimization)




Page 47

Improper Site Address Causes Cross Coverage

Cross coverage before optimization




Page 48

Improper Site Address Causes Cross Coverage

Analysis

In a pilot office, the height of the site on the Erqi Road exceeds 60 m, which is about 20 m higher than the average height of its surrounding buildings. Therefore, the cross coverage is easy to form, which causes co-channel interference with other sites.

Generally, if a site is located at a high place, you can replace the antenna with the fixed electrical tilt 2° with an antenna with the fixed electrical tilt 6°. As the site on the Erqi Road is located on the coverage edge, you can adjust the azimuth and tilt of the antenna to decrease the interference with other sites. In this optimization, the preferable solution to the cross coverage is to increase the mechanical tilt and adjust the azimuth instead of to replace the antenna.




Page 49

Improper Site Address Causes Cross CoveragelAdjustment measures: Increase the tilt to 4°. After the adjustment, the cross coverage is improved greatly. The cross coverage, however, still occurs in some areas on the road.

Cross coverage in some areas after optimization




Page 50

Improper Antenna Installation Causes Limited Coverage

Limited coverage caused when the antenna is installed without considering platform blocking




Page 51

Improper Antenna Installation Causes Limited CoverageAnalysis

In a project, the antennas of the site are placed on the platform (10 m high), as shown in the figure in P50. In the optimization phase after network construction, VP mosaics often increase before the traffic light under the antennas. In this case, the image quality becomes poor and the PS 384k service is re-activated.

According to the planning, the 3G network and 2G network share a site address. According to the 2G test data, the signals do not fluctuate greatly at the intersection and under the site. That is, if the 3G and 2G antennas are located at the same place, the 3G coverage at the intersection should also come from the site. Therefore, the causes for the problem are summarized as follows: (1) The 3G antenna is installed close to the wall of the platform, which blocks the propagation of signals. (2) The 2G antenna and its installation parts affect the pattern of the 3G antenna, which makes the radiation pattern of the 3G antenna vary. According to the installation scenario of the antennas, it is very difficult to replace the location of the 3G antenna.




Page 52

Improper Antenna Installation Causes Limited CoveragelAdjustment measures: To avoid affecting 2G coverage, use the following solution with the minimum changes: Connect the 3G Tx/Rx feeder and 2G Tx/Rx feeder to two ends of the wideband polarized antenna close to the road, and then connect the 3G Rx feeder and 2G Rx feeder to two ends of the wideband polarized antenna far from the road, as shown in the following figure.

Feeder optimization




Page 53


Cases


Problems



Neighboring Cell

Configuration




Page 54

Data Analysis Before Optimization:1. Find a pilot pollution point

Pilot pollution near the Yuxing Road: cell 270 is designed to cover the area.




Page 55

Data Analysis Before Optimization:2. Analyze the distribution of cell signals

near the pilot pollution point

Best serving cell near the Yuxing Road

2nd best serving cell near the Yuxing Road




Page 56

Data Analysis Before Optimization:2. Analyze the distribution of cell signals near the pilot pollution point

3rd best serving cell near the Yuxing Road 4th best serving cell near the Yuxing Road

Composition of pilot pollution on the Yuxing Road




Page 57

Data Analysis Before Optimization:3. Analyze the distribution of RSSIs near

the pilot pollution point

RSSIs near the Yuxing Road

RSCPs for the best serving cell near the Yuxing Road




Page 58

Data Analysis Before Optimization:4. Analyze the distribution of RSCPs in

related cells

RSCPs in cell 270 near the Yuxing Road




Page 59

Data Analysis After Optimization

Pilot pollution near the Yuxing Road after optimization

Best serving cell near the Yuxing Road after optimization




Page 60

Data Analysis After Optimization

RSCPs for the best serving cell near the Yuxing Road after optimization

RSCPs for cell 270near the Yuxing Road after optimization




Page 61


Cases


Problems



Neighboring Cell

Configuration




Page 62

Missed Neighboring Cell Configuration Causes Call Drop lAccording to the measurement result of the active set on the UE, the Ec/Io quality near the place where the call drops is very poor, and the signal strength of the serving cell is very poor (continuously lower than -15 dB) before the call drop, and the current serving cell corresponds to scrambling code 209, as shown in the following figure.

Ec/Io information in the active set measured on the UE before the call drop




Page 63

Missed Neighboring Cell Configuration Causes Call DroplAccording to the measurement data on the Scanner, the signal measured on the Scanner is always good at the place where the signal measured on the UE is very poor before the call drop, and the signal belongs to the cell corresponding to scrambling code 128, as shown in the following figure.

Ec/Io information in the active set measured on the Scanner before the call drop




Page 64

Missed Neighboring Cell Configuration Causes Call DropAnalysis

l As shown in the figures in P62 and P63, the neighboring cell corresponding to scrambling code 128 may not be configured. To confirm the inference, view the message process near the place where the call drops. Find the latest intra-frequency measurement control message, and then check whether scrambling code 128 is contained in the list of intra-frequency neighboring cells. According to the result, scrambling code 128 is not contained in the list of intra-frequency neighboring cells. Therefore, the call drop is caused by missed neighboring cell configuration.

l If only the UE data is available in the test, you can determine whether a required neighboring cell is not configured in the following way:

[ Determine the scrambling codes of all the cells in the active set and monitored set measured on the UE before the call drop.

[ Determine the scrambling code of the cell on which the UE camps after the call drop, and then compare the scrambling code with the scrambling codes in the active set and monitored set before the call drop. If the scrambling code is not in the list of scrambling codes in the active set and monitored set, the call drop may be caused by missed neighboring cell configuration.

[ Check the list of neighboring cells for confirmation.




Page 65

Common Adjustment Measures in RF Optimization

The adjustment measures in the RF optimization phase cover two aspects: list of neighboring cells and engineering parameters. Most coverage and interference problems can be solved through adjusting the following engineering parameters (arranged in descending order by priority):

[ Antenna tilt

[ Antenna azimuth

[ Antenna height

[ Antenna location

[ Antenna type

[ TMA (for example, add a TMA)

[ Site type (for example, change the site supporting a 20 W power amplifier to the site supporting a 40 W power amplifier)

[ Site location

[ Site or RRU (for example, add a site or an RRU)




Page 66

Summary

l RF optimization focuses on improving the distribution of network

signals to provide a good radio environment for subsequent

optimization of service parameters.

l The DT is a main test method in RF optimization and other test

methods serve as a supplement.

l The coverage, pilot pollution, and handover problems are mainly

analyzed in RF optimization, and the analysis of other problems serve

as a supplement. Based on the analysis of the three problems, you can

solve related handover, call drop, access, and interference problems.

l The engineering parameters are mainly adjusted in RF optimization,

and the cell parameters are adjusted in the parameter optimization

phase (except the adjustment of the list of neighboring cells).



Thank Youwww.huawei.com


http://www.huawei.com


Training wcdma rf optimization gsm to umts

Education