08-0-WCDMA Radio Network Optimization Exchange-122.ppt

WCDMA Radio Network Optimization Exchange

Content

Basic knowledge on WCDMA radio network optimization

WCDMA radio network optimization process and technology

Case analysis


Let’s start from the following aspects to understand network optimization:

What is network optimization? Service concept of network planning and

optimization Reasons for network optimization Types of network optimization

What is Network Optimization?

Radio network optimization refers to a rational adjustment process on radio communication network planning and design by means of various optimization measures.

Via optimization, network coverage can be improved, network capacity can be expanded, network QoS and network resource utilization enhanced, so that networks will be running more reliably and more economically.

Coverage

Q

Quality of service

Operator revenue

Operation cost

¥

Network capacity

Service Concept of Network Planning and Optimization

A top-notch network is demanded by customers, started from planning, improved during the process and gets its heyday via optimization

Quality:

Call drop

Handover failure

RRC connection failure

RAB assignment failure

Low data speed

Low access success rate

Low paging success rate

Time delay is too long

……..

Cause of Network Optimization

End user change/ New calling model / Subscriber change Environment change, new building, Road or Vegetation New structure change , coverage, capacity New technique, new equipment etc.

Types of Network Optimization

In different stages of UMTS network construction, the objectives of network optimization are also different from each other.

Depending on the time segment, work objectives and work content of its implementation, optimization can be divided into Engineering Optimization and operation/maintenance optimization .

Classification of Network Optimization

Engineering optimization Engineering optimization refers to the network optimization

conducted after the completion of network construction and before the number allocation. Its major purpose to enable the network to work normally and ensure that the network can fulfill the planned coverage and interference objectives.

The major work contents of Engineering Optimization include: Eliminating the hardware fault of the system Checking whether the cell configuration is consistent with the

planned objective of the network (Longitude, Latitude, Azimuth, Down tilt, Connection, Lac, RAC, CI, antenna height, etc )

Making the coverage and interference reach a satisfactory level

Classification of Network Optimization

Operation and maintenance optimization Operation and Maintenance (O&M) optimization

indicates to improve the network quality and customer’s degree of satisfaction through optimization during the operation of the network.

It includes three parts of contents: Routine maintenance Stage optimization Network operation analysis

Engineering Optimization

At different stages of UMTS network construction, the objectives of network optimization are also different.

The objectives of (Pre-launch) Engineering Optimization include: Enabling the network to work normally

Issues deserving attention: coverage function and interference


Eliminate the hardware fault of the system: It is very important to eliminate any hardware fault

from the system. Generally hardware faults are eliminated according to

the division of base station cluster. The elimination of hardware faults is the responsibility

of the equipment supplier. However, it is also very important for the operator to

understand the process of hardware fault elimination and obtain the ability for checking the equipment.


Check the cell configuration: Whether the site is in the correct position Whether the type of the antenna is correct Whether the installation height, direction angle and

downward tilt angle are all deployed according to the planned solution

Whether the type of the feeder is correct and whether its length is appropriate

Whether parameters (such as common channel power) of the cell are consistent with the planned parameters.


Objectives for coverage and interference optimization

Typical threshold: The intensity of the pilot received in 95% of the

coverage area is greater than -89dBm (in dense urban areas) or -94dBm (in general urban area).

The pilot Ec/Io measured in 95% of the coverage area is greater than -10dB.


Steps for improving the coverage: Conduct drive test and collect the drive test data. Analyze the drive test data to determine the holes of

the coverage. Assess the seriousness of the coverage holes and

order them according to the priority. Solve the coverage problems according to the priority

till the objective of the coverage optimization is fulfilled.


Steps for improving the interference: Determine the areas where the pilot Ec/Io is lower

than the threshold. Check the pilot level in these areas (which may have

more than 3 pilots). From the pilots received in these areas, find the pilots

unexpected (these pilots come from the cells that are not designed to provide coverage for these areas).

Reduce the intensity of these “unexpected” pilots (generally by increasing the downward tilt). Pay attention to the influence resulting therefrom on the coverage within the service range of the cell (the influence can be checked with the planning tool).

O&M Optimization

Objectives of post-launch o&m optimization: Improving the QoS Increasing the system capacity Increasing the coverage range of the service (for

example, increasing the coverage range of high-speed data service)

Providing better service for hot-spot areas Maximizing the return of the investment

O&M Optimization

The major work contents of the post-launch O&M Optimization include: Adding base station Further sectorizing existing base station Optimizing the parameters Reducing the interference Using more than 1 carriers Implementing the Hierarchical cell structure Providing the solution for indoor coverage

Flow for network operation analysis

Start

Retrieve background data

OMC engineer

Analyze data and network performance

Optimizing engineer

Background statistics data

Network running

analysis report

End

O&M Optimization Network operation analysis is suitable for a network in formal

operation. OMC performance statistic data can be extracted and analyzed periodically, possible equipment and network problems can be analyzed and then network operation analysis report can be submitted to provide a reference for the customer’s network adjustment and optimization.

Content



Case analysis

Simulation/plan report

Start

Preliminary setup

Frequency scan

Calibration test

Network data collection

Data analysis

Parameter check

Problem positioning

Making optimization plan

Carrying out optimization plan

Optimization verification

Network performance meets the requirements?

Optimization project acceptance

Data archive

Optimization project plan

Network evaluation report

Optimizing adjustment plan

Optimizing adjustment record

Network optimization report

End

Network Optimization Flow

A perfect work plan is the guarantee for the smooth implementation of network optimization and can also be used to monitor the optimization progress.

Preparations

Analyzing the Requirements Understand the coverage and capacity requirements. Confirm the setting of the optimization test parameters. Confirm the work division interface with the customer. Confirm the acceptance standard of each item.

Drawing the work plan The work plan should be drawn according to such

conditions as the network scale, human and equipment resources as well as the customer’s objective and requirement for the network optimization. Then output the Optimization Plan for WCDMA Radio Network in XX Service Area.

Preparations

Collecting and investigating materials Obtain the WCDMA Radio Network Simulation Report in XX

Service Area and WCDMA Radio Network Planning Report in XX Service Area at the network planning stage.

Obtain the site information, antenna feeder information and the setting of the system parameters in the current network.

Make clear the problems in the current network. Preparing optimization tool

DT tools are the basic tools for network optimization test. They include DT software, test mobile phone, receiver and GPS. Besides, some DT equipment requires a dual-serial-port card.

Possible signaling analyzer need be used for signaling tracing and locating. If interference test need be conduct, device such as spectrograph may be required; If the engineering parameters need be adjusted, then devices such as compass may be used.

Engineer and vehicle

Spectrum Scanning (Optional)

Spectrum scanning With the authorization from the customer, scan and

confirm the frequencies used by the network at present in the optimization area to ensure that the frequencies are clean and available.

Calibration Test(Optional)

Calibration test Calibration test of vehicle-mounted antenna Calibration test of the external antenna of the test

mobile phone Test of the average penetration loss of the vehicle

body Test of building loss

Collection of Network Data

Source of network optimization data: DT data CQT data OMC performance statistic data User complaint information Alarm information Other data

Parameter Requirement for Data Collection Only under the same load condition and on the same paging mode, can the

comparison be carried out between the network evaluations. Therefore, you should firstly understand the parameter selection of the network data.

The loads in the network evaluation test can be divided into types: on busy, with load and without load (or light load). For the network in running and with large number assignment, the “on busy” evaluation is adopted; for the newly created network, the “with load” or “without load” evaluation is adopted.

In terms of call duration, the call modes can be divided into continuous long call and periodic call.

The difference between this two call modes is the duration. The call duration for the continuous long call is as long as possible, while that for the periodic call is fixed (the duration is determined by the real situation.

The times of periodic call reflects the processing capability and the result is closer to the user’s usage, while the continuous long time call reflects the system’s switching capability.

Network Data Collection- DT Data

The DT data to be collected includes: Ec/Io, Pilot Power, UE TX Power, Neighbours, Call

Success/Drops and Handover statistics; FER/BLER, Delay

DT devices include: Scanner, test mobile phone, DT software and GPS. As for the on-site test software, the special test software for WCDMA radio network optimization ZXPOS CNT1(UMTS Edition) can be adopted.

Scanner is used for to collect complete radio network information, and implement pilot analysis test and spectrum analysis test.


Both scanner and test mobile phone can be used for network data collection. However they are different from each other in some way.

Test mobile phone is used to know the situation of the users and collect the downlink information on the network. It implements the following functions:

Collecting the measurement data of the mobile phone, including pilot power, Ec/Io, UE Tx power, neighbor cells, RSSI and FER/BLER.

Call class event and performance statistics: including the statistics of call drop rate, blocking rate, call success rate, handover success rate, voice service quality and data

service rate.

Collecting the signaling of aerial interface: decoding L3 messages such as access, paging, synchronization and downlink/uplink service messages.


WCDMA system is a self-interference system. On different network

load conditions, the DT result will also be different. Thus, before the

test the network load need be confirmed.

An appropriate test time need be selected according to the load

selection of different networks.

Based on the area that the test path belongs to, DT can be divided into

urban DT and artery DT.

The test conditions shall be kept consistent for tests conducted before

and after the optimization.


DT Principles

Radial path and ring path shall be selected as the DT path.

The radial path can reflect the variation of the signal quality according to the change of the base station distance.

The ring path can provide the prediction of the signal quality in different directions of the base station.

During the optimization test, generally three test paths need be defined for each base station cluster. Besides, the test paths before and after the optimization shall be kept consistent.


Selection of test path


Consistency requirement for test conditions The same test tool and parameter setting shall be adopted

before and after the optimization whenever possible. The same test antenna and feeder shall be adopted before

and after the optimization. The same analyzers shall be sent to process the data. The test path shall be selected before and after the

optimization. To guarantee the consistency of the UE movement speed,

the distance-based sampling mode instead of time-based sampling mode is adopted for sampling the data. The DT tool cannot sample data in the distance-based mode, data collected can be paused when the vehicle stops in the case of red light.

Check whether the loaded test is conducted in the test area. Ensure that the test is conducted at the same time segment in each day to obtain the basically the same network load conditions.

Conduct the test in the same period.

Including the geographical location information

Subject to the restriction of selected test path, which influences the accuracy of the test

result


Features of DT data

Scenic spot, airport, railway station, bus station and port

Important hotels (star-level hotels) Catering and entertainment sites, large

shopping malls Important residential communities and office

areas Other important areas

Conduct the CQT at a fixed places and record various data at each place. At each test place several calls shall be originated.

Fixed-point CQT includes CS service test and PS service test. The specific test contents are related to the customer’s requirement and shall be determined according to the actual situation.

Network Data Collection-CQT Data

CQT refers to the fixed-point test conducted at important places in the coverage area.

Test time requirement The following factors shall be considered during the selection of test site:

The traffic of the area where the test point is located: for a network in formal operation, generally a site with large traffic shall be selected.

Geographical sector of the area where the test site is located: 80% of the test sites shall be indoor while 20% shall be outdoor. Besides, the sites shall be geographically distributed evenly.

Radio environment of the area where the test site is located: a place where repeater or indoor distribution system is installed shall be preferred as the test site.

Areas where there may be network problems: areas that may become coverage blind areas, for example, street canyons between high buildings or places in areas with multiple carriers


CQT principles

Including geographical location information

Subject to the restriction of the selected test path, which influences the accuracy of the

test result


Features of CQT data

Extraction

Concept

Features

The extraction of OMC performance statistic data is suitable for a network

that has already been commercially applied on a large scale. The data are

objective and abundant and reflect the operation quality of the whole

network from the point of view of statistics. The network performance

index obtained in this way can be used as the most important basis for

assessing the network performance.

The counter value required for calculating the network KPI can be

extracted flexibly. Besides, the statistics can be conducted flexibly

according to different statistic range, or performance statistics table can be

made according to the customer’s requirement.

Based on the statistics of large amount of sampling data, the background

NMS reflects the operation quality of the network under its management.

The statistic range varies from one another. In some cases the statistic unit

is RNC and in other cases the unit is logic cell.

Counters for calculating various network performance indices are

provided.

Network Data Collection-OMC Performance Statistic Data

Network Data Collection-User Complaint Information

As the end user of the network service, ordinary user has more direct experience of the network performance. The user complaint information most directly reflects

the disadvantage of the network. Users are most concerned with the problems included

in the complaints, which need be solved as soon as possible.

The complaint includes geographical location information.

Generally the problems complained include poor signal coverage quality, difficulty for call completion and frequent call drop.

Network Data Collection-Alarm Information

Alarm information includes the alarm information of the RNC, Node B and CN background NMS.

It reflects the abnormal or near-abnormal status in equipment use or network operation. During network optimization, the alarm information deserves close attention and need be viewed periodically, so that warning information or problems can be found in time to avoid the occurrence of accident.

Network Data Collection-Other Data

In addition to the data listed above, there are data obtained through the signaling analysis system, network flow test system and voice quality assessment system.

Data Analysis

Data analysis indicates to make clear the network operation quality, assess the network performance, find and locating the possible network problems and provide suggestions for network optimization by analyzing the DT data, CQT data, OMC performance statistic data, user complaint information and alarm information.

Common Analysis Methods

Common optimization analysis methods include: Multi-dimensional analysis Tendency analysis Accident analysis Comparative analysis Grading analysis Cause and influence analysis

Multi-dimensional analysis

“Dimension” here refers to the standing point of problem handling and the direction

problem solution.

The data can be analyzed from several different angles and the combinations of them.

For example: to solve the call drop problem, we shall not only pay attention

to drop, but also handover and access problems.


Tendency analysis Analyze the tendency of the change according to the change of time from the

angle of time sequence and find the regularities.


Accident analysis

Find abnormal data such as over-high /over-low data and too drastic change

from a large amount of data and, and find the data of the cause.

The call drop rate

is abnormally

high. We should

check whether

there is problems

in this time

segment.


Comparative analysis

It indices to compare different data sets from the same angle and find the

difference. If necessary, we can further find cause of the difference. This

method is generally used in signaling flow analysis.

Grading analysis

Find the Top N and Bottom N data from a large amount of data according to a

certain classification method. These data deserve special attention, for example,

the common worst cell method.


Cause and influence analysis

Find the influence factors from a large amount of data for a specific

result already generated and analyze the importance of the different

factors and or their combinations.

Each method has its orientation and restriction for problem analysis. Thus, it is difficult to only use a single method to locate a specific equipment problem parameter configuration problem (including engineering parameter and radio parameter) and network resources utility problem. Instead, the above analysis methods shall be combined and used together.


First summarize the network test and analysis conducted at the

early stage and output the WCDMA Radio Network Assessment

Report in XX Service Area.

The comprehensive score of the network assessment shall be

obtained by weighting and summating the DT score, CQT score

and OMC background index score.

The evaluation is used to discover the problems in the network,

provide guide for the network optimization at the next stage and

facilitate the comparison of the performance before and after the

network optimization.

Network evaluation

Check the base station

Check whether the base station is in the correct location, whether the type of the antenna

is correct, whether the height, direction angle and downward tilt of the antenna are

consistent with the planned solution, whether the type of the feeder is correct and the

length is appropriate and whether VSWR of the antenna feeder is appropriate.

Data analysis can help find bad indices in the network. If it is found that the parameter

configuration is unreasonable and influences the network performance, the parameter

configuration of the abnormal base station must be checked. The contents of the check

include:

Check whether the radio configuration parameter of the cell is consistent with the planned

value.

Check the relevant configuration parameters of the voice service and data service.

Parameter Check (Optional)

Problem Locating

The problems of radio network are found in the following major aspects: Equipment software and hardware problems Engineering parameter problem Radio parameter problem Network capacity problem

Making Optimization Solution

The major adjustment policies for network optimization includes: Adjust the software and hardware of the equipment.

If software problem is found through parameter check, the software version shall be confirmed and updated in time. Hardware problem is generally board fault, in which case the faulty board need be replaced by a normal one.

Adjust the network engineering parameters.This includes the adjustment of the direction angle, downward tilt angle, height and location of the antenna. After the network construction is completed, coverage and interference problems in the pre-launch network optimization shall be solved by adjusting the network engineering parameter.

Adjust the network radio parameters.This includes the adjustment of the access parameter, paging parameter, power control parameter, handover parameter and search parameter.

Adjust the neighboring cell list of the system. Optimize the neighboring cell list of the network through DT data analysis.

Capacity analysis or busy analysis. Possible measures include cell splitting, adding cells and micro cells, RF extension and use of multiple carriers.

Carrying out Optimization Plan

If the network scale is large, the network need be divided into different base stations clusters to locate and solve the network problems in different areas.

After the all base station clusters have been optimized, the global network can be optimized to solve global network problems and problems across different clusters. Then Evaluate the performance of the global network after the optimization and verify whether the network performance indices have meet the acceptance standard and reached optimization objectives.

The cluster division principles shall be adjusted according to the actual situation, generally according to the topography of the local area. neighboring areas that have special requirements for data or voice service shall be grouped in the same cluster to facilitate optimization debugging. Besides, cluster division can also be conducted according to the problems found in the network assessment before the optimization. There shall be overlap between two neighboring clusters.

The optimization of different clusters can be implemented either parallel or serially depending on the resources and time requirement.

Optimization Verification

After the network optimization solution is implemented, it is necessary to verify whether the network problems have been solved or whether the network performance is improved.

To implement the optimization verification, also first collect the network operation data and analyze the collected data.

After the optimization solution is implemented, assess the network performance again by analyzing the DT data, CQT data, OMC performance statistic data, user complaint and alarm data.

Compare the network performance indices before and after the optimization and verify whether the network problems are solved or the network performance has met the requirement after the optimization.

Project Acceptance

Acceptance test shall be conducted for the required network performance indices according to the contract requirements. Contents of the test such as the test path, test point and call mode shall be set according to the principle determined at the contract or requirement analysis stage. In principle the customer shall participate in the acceptance test.

Documentation Archiving

After the optimization verification and project acceptance, the network optimization report need be submitted and relevant documentations need be archived.

The network optimization report includes such contents as problem analysis, locating process, optimization measures adopted, comparison of the indices before and after the optimization, remaining problems of the network and suggestions for subsequent construction.

Content



Case analysis

Classification of Optimization Cases

Based on the difference in optimization contents, the current cases can be classified into the following types: Engineering parameter optimization Radio parameter optimization Integrated optimization

Signal distribution in the Donghu Road area before the optimization

Engineering parameter optimization-adjusting the direction angle of the antenna

Problem During the coverage optimization DT along Zhongshan Road No. 1 and Donghu

Road, it is found that the receiving power of the UE one Donghu Road between the Donghu base station and Shuqian Road base station is weak and less than -85dBm. In addition, the pilot signal quality Ec/Io is also poor and less than -13dB in this area (as shown in Area A in the figure below):

Triggering indices: pilot Ec, Ec/Io

Engineering Parameter Optimization-Adjusting the Direction Angle of the Antenna

Handling Idea Through the review of the DT data with optimization

analysis software ZXPOS CNA1 and the survey on the site, it is found that in front of Sector 2 (with the scramble 437) of the Shuqian Road base station, there are dense buildings which form a serious barrier and influences in the coverage of the sector. Besides, the areas within scores of meters in front of Sector 1 (with the scramble 439) of Donghu base station is also completely blocked by a row of high residential buildings, which makes Sector 1 unable to cover that area.

Solution Change the direction angle of Sector 2 in the Shuqian

Road base station from 240o to 230o to enhance the coverage of that area of Donghu Road.

Signal distribution in Donghu Road after the optimization

Engineering Parameter Optimization-Adjusting the Direction Angle of the Antenna

Effect assessment From the analysis of DT data, it can be seen that in this part of the Donghu

Road, the UE receiving power is >-85dBm and the pilot Ec/Io>-13dB, which meets the coverage requirement.

Signal distribution of Baishi Road before the optimization

Engineering Parameter Optimization-Adjusting the Direction Angle and Downward Tilt Angle of the Antenna

Problem Through the analysis of the DT data of Baishi Road, it is

found that pilot strength received in the middle part of road is less than -95dBm, as shown in Area A in the figure below:

Triggering index: the pilot signal is not strong enough.

Engineering Parameter Optimization- Adjusting the Direction Angle and Downward Tilt Angle of the Antenna

Handling Idea Through DT data analysis it is found that the coverage

of this area is provided by Sector 2 of Shenzhen University base station. The direction angle of Sector 2 is 110° and the downward tilt angle is 4°. Both shall be adjusted to enhance the coverage of Baishi Road.

Solution Adjust the antenna direction angle of Sector from 110°

to 120° and the downward tilt angle from 4° to 12°.

Pilot coverage of Baishi Road after the optimization

Engineering Parameter Optimization- Adjusting the Direction Angle and Downward Tilt Angle of the Antenna

Effect assessment Conduct DT on the Baishi Road after the optimization. From the DT

result below it can be seen that the pilot strength is improved to more than 90dBm.

Base station distribution in the case of miss of neighboring cell configuration

Radio Parameter Optimization-Neighboring Cell List

Problem During the drive test call drop is found between the Huacheng base station and

Yunshan Hotel base station. Through several times of drive test, it is found that call drop will occur in the handover from Huacheng base station to Yunshan Hotel base station, while no call drop is found during the handover in the reverse direction.

Triggering index: unidirectional handover failure

Radio Parameter Optimization-Neighboring Cell List

Handling Idea Through DT analysis, it is found that the area about 20m from the call drop

point is covered by the signal of Sector 3 (with the scramble 426) of Huacheng base station, instead of the signal of Sector 1 (with the scramble 426) of Huacheng base station. The cause is found to be the barrier of high-storey buidling scores of meters in front of Sector 3 (with scramble 426) and the signal is reflected to a part of road about 20m long between Huacheng base station and Yunshan Hotel base station. By checking the neighboring cell list, it is found that Sector 3 (with the scramble 414) is configured with Sector 3 of Huacheng base station as its neighboring cell, while Sector 3 (with the scramble 426) of Huacheng base station has not been configured with Sector 3 of Yunshan base station as its neighboring cell. This results in unidirectional handover failure and further causes call drop. Thus, the call drop is caused by the problem in the mutual configuration of neighboring cells.

Solution Configure Sector 3 (with the scramble 414) of Yunshan Hotel base station as

the neighboring cell of Sector 3 (with the scramble 426) of Huacheng base station.

Effect assessment After the neighboring cell configuration is improved, drive test has been

conducted repeatedly between Huacheng base station and Yunshan Hotel base station, no call drop has occurred again.

Pilot Signal Distribution

Radio Parameter Optimization-Power Parameter

Problem There are two call drop points on an express way in the network (In Tunis),

as shown in the figure below: Triggering index: call drop


Handling Idea Point A is about 2.7km away from Sousse2 site. It is the

entrance to a inter-city highway and has a bend of about 90°. Here the signal of Cell 228 of Erriadh TT suddenly becomes weak as it is blocked. Point B is about 2km away from from CTT Skanes site. The altitude of the coastal express way where B is located is lower than that of CTT Skanes site. Thus, the signals of Cell 332 of CTT Skanes site can only reach the mobile phone after penetrating houses of 2~3 storeys. As result, the pilot strength near Point B has decreased to less than –100dBm.

Due to the restriction of the environment, the altitude of the Sahaling site is only 25m high and there is little room to increase the height. Therefore, the transmitting power of the cell need be adjusted appropriately to enhance the signal coverage of the call drop point.


Solution Increase the transmitting power of the pilot channel and

other common channels. Effect assessment

The coverage effect has been obviously improved and the call drop rate along the express way has decreased obviously. Channel Before the Adjustment After the Adjustment

CPICH 10% 15%

BCH -3dB -3dB

FACH 0dB 3dB

PCH -3dB -2dB

PSCH -4dB -3dB

SSCH -4dB -3dB

PICH -7dB -7dB

AICH -7dB -7dB

Adjusting the Power Parameter of the Cell

Call Drop Points of the Express Way

Radio Parameter Optimization-Handover Parameter

Problem (In Libya), in the test of a pre-commercial network, the call drop

rate on the coastal express way from TRI002 to TRI004 is high and the call drop points are shown in the figure below:

Triggering index: call drop

Barrier high buildings before the sky plane of Cell 404 in TRI002 base station

Radio Parameter Optimization-Handover Parameter

Handling Idea From the test data analysis the coverage distance of cell 404 near the call drop

point is very short. However the vehicle speed on this express way is generally greater than 120Km/h. From the sky plane it can be seen that there are several high buildings in front of the sky plane of 404, which form barriers. As the handover distance is very short and the call drop point on the coastal express way is only more than 400m away from TRI002 site, the signal is very strong when it appears and but quickly disappears. Thus, the strong signal of the neighboring cell of Cell 404 joins the activation set very slowly and there are may ping-pong handover phenomena, which is very easy to result in call drop, as shown in the figure below:


Solution Optimize the handover parameter: adjust 1A and 1B

event handover parameters so that joining event can easily occur while it is difficult and slow for deletion event to occur. Adjust the values of the handover parameters 1C and 1D, reduce the handover threshold to the strongest pilot but increase the handover observation time. This helps increase the ratio of the strongest and more stable scrambles used by the user. The optimization adjustment solution is shown in the following table.

Effect assessmentThrough the handover parameter adjustment above, the call drop problem has been solved.


Parameter Name Before the Adjustment After the Adjustment

1A event

Reporting Range Constant 3 5

Hysteresis 3.5 2

Reporting deactivation Threshold

3 3

Time to trigger 200ms 200ms

1B event

Reporting Range Constant 7 6

Hysteresis 3.5dB 4


1C event

Hysteresis 6dB 4


1D event

Hysteresis 6 4dB


Call Drop Points on Shuqian Road

The figure shows the Pilot Ec/Io DT result on Zhongshan Road No. 1 (due to the influence of the signals of Huacheng base station, the Ec/Io in Area A in the figure is poor and call drop may easily occur here. However, the pilot strength in this area is good enough).

Integrated Optimization-High Base Station

Problem Huacheng base station is located on the Gaoxun Building beside the Quzhuang

cloverleaf junction and is 70m high. Through drive test it is found that Cell 426 (scramble) of Huacheng base station has cross-cell coverage and the signal of the cell received on Zhongshan road that is far from Huacheng is still very strong. As Cell 426 is not configured as the neighboring cell of Cell 436 of Sector 1 of Shuqian base station on Zhongshan Road, call drop may easily occur in this area, as shown in the figure below.

Trigger Index: call drop

Handling Idea Due to the barrier of the tall buildings in the south of Huacheng

base station, there is shade attenuation and the occurrence of the following events can be seed from the update report from the activation set (together with the figure):

Base station distribution and radio environment


Analysis of Call drop cause

• Cell2 becomes the cell of best service. • Cell1 is deleted from the activation set. • Cell3 is not in the neighboring cell list of

Cell2. The strong signal of Cell3 makes the Ec/Io poor, which causes call drop.


Handling Idea Due to the barrier of the tall buildings in the south of Huacheng base station,

there is shade attenuation and the occurrence of the following events can be seed from the update report from the activation set (together with the figure):


Solution Increase the mechanical downward tilt of the antenna

of Cell 426 in Huacheng base station. Add Cell 426 of Huacheng base station into the

neighboring cell list of Shuqian base station. Make 3dB lower the maximum transmitting power,

common channel power and pilot channel power of Cell 426 of Huacheng base station.

Effect assessment After the optimization, the pilot Ec/Io in Area A is

greatly improved and call drop no longer occurs.

08-0-WCDMA Radio Network Optimization Exchange-122.ppt

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