zte umts load-monitoring and expansion guide

UMTS Network Load Monitoring and Expansion Guide

R1.0

UMTS Network Load Monitoring and Expansion Guide Internal Use Only▲

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Revision History

Product Version Document Version Serial Number Reason for Revision

RNC V3.09 R1.0 First published

Author

Date Document

Version Prepared by Reviewed by Approved by

2011-3-15 R1.0 Qiao Bin, Jin Zhengtuan, and Xu Yi

Ma Wei Wang Zhenhai


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Intended audience: UMTS network optimization engineers

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About This Document

Summary

Chapter Description

1 Overview Briefly introduces the background and the main contents of high-load network monitoring and optimization.

2 High-Load Network Monitoring Describes the classification of UMTS network elements (NEs) and the key performance indicators (KPIs) for network load monitoring.

3 High-Load Network Optimization Describes the process of network load optimization.

4 High-Load Network Expansion Describes the thresholds, judgment, and implementation of capacity expansion for high-load networks.


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TABLE OF CONTENTS

1 Overview ......................................................................................................... 1 1.1 Background ...................................................................................................... 1 1.2 Main Contents .................................................................................................. 2

2 High-Load Network Monitoring ...................................................................... 6 2.1 WCDMA NE Classification ................................................................................ 6 2.2 Network Load Monitoring Indicators .................................................................. 7 2.3 Key Indicators ................................................................................................... 7 2.3.1 Average Utilization of Non-HSDPA Code Resource.......................................... 7 2.3.2 Average Utilization of Non-HSDPA Carrier Transmit Power .............................. 9 2.3.3 Uplink Noise Rise ........................................................................................... 10 2.3.4 Average Throughput of HSDPA Cell ............................................................... 11 2.3.5 Average Throughput of HSDPA Single User ................................................... 11

3 High-Load Network Optimization ................................................................ 13 3.1 Network Load Optimization Stages ................................................................. 13 3.2 Network Load Optimization Process ............................................................... 14

4 High-Load Network Expansion .................................................................... 16 4.1 Expansion Process ......................................................................................... 16 4.1.1 Expansion Analysis Process ........................................................................... 16 4.2 Expansion Criteria and Methods ..................................................................... 17 4.2.1 Cell Expansion ................................................................................................ 17 4.2.2 Node B-CE Expansion .................................................................................... 26 4.2.3 IUB Transmission Expansion .......................................................................... 30 4.2.4 RNC Expansion .............................................................................................. 33


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FIGURES

Figure 1-1 High-Load Network Monitoring and Optimization ................................................ 3

Figure 1-2 High-Load Network Monitoring Process .............................................................. 4

Figure 1-3 High-Load Network Optimization Process ........................................................... 5

Figure 2-1 Relationship Between the Uplink Capacity and Noise ....................................... 10

Figure 3-1 Flowchart of Network Load Optimization ........................................................... 13

Figure 3-2 High-Load Network Optimization Process ......................................................... 15

Figure 4-1 Expansion Analysis Process ............................................................................. 17

Figure 4-2 Cell Expansion Decision Process ...................................................................... 18

Figure 4-3 Combination Chart of Cell Expansion Decision Formula ................................... 21

Figure 4-4 Relationship Between the Code Resource Utilization and Traffic ...................... 23

Figure 4-5 Relationship Between the Cell Carrier Transmit Power Utilization and TCP Limited Proportion ................................................................................................................ 24

Figure 4-6 Average Utilization Rates of Uplink and Downlink NodeB CE Resources in Shapingba, Chongqing, China .............................................................................................. 28

Figure 4-7 Maximum Utilization Rates of Uplink and Downlink NodeB CE Resources in Shapingba, Chongqing, China .............................................................................................. 29

TABLES

Table 2-1 Code Resource Distribution of Code Channel ...................................................... 8

Table 4-1 Cell Expansion Thresholds ................................................................................. 19

Table 4-2 Cell Expansion Implementation Rules ................................................................ 25

Table 4-3 Node B CE Expansion Thresholds and Expansion Methods .............................. 27


Table 4-5 Iub Transmission Expansion Thresholds ............................................................ 31


Table 4-7 Monitoring Indicators of RNC Hardware Expansion ............................................ 36

Table 4-8 Observation Indicators of RNC Hardware Expansion ......................................... 37

Table 4-9 Observation Indicators of RNC Hardware Expansion ......................................... 39

Table 4-10 RNC Expansion Implementation Rules ............................................................. 41


ZTE Confidential Proprietary © 2013 ZTE CORPORATION. All rights reserved. 1

1 Overview

1.1 Background

To monitor and optimize the high load and performance of UMTS network is one of the

key tasks in the network operation and maintenance stage. With the increase of the

subscriber number and service application, especially with the rapid development of the

wireless broadband service, the network load will keep increasing. When the network

load reaches a certain level, the network resources will be congested and the network

performance will deteriorate, affecting the end users’ service experience.

To provide the users with high-speed access experience and keep the competitiveness

of the UMTS network, the operators should perform real-time monitoring to the load and

performance of the whole network, alarm the network element (NE) exceeding the load

threshold, take timely measures of optimization and expansion to meet the requirement

of service development.

In the narrow sense, the load refers to the traffic loaded by the network or channel. In the

broad sense, except for the network traffic, the operators need to consider the resource

utilization of the software and hardware of each NE in the network. The higher the

utilization rate is, the heavier the load will be.

Compared with the 2G network, the monitoring and management of the UMTS network is

more complex. The reasons are as follows:

The UMTS is a soft capacity system. Its capacity is not only constrained by the hard

resources such as the CE and Iub configuration bandwidth, but also constrained by the

soft resources such as the OVSF code, uplink interference, and downlink power. Subject

to the requirements for the network coverage and service quality, the system capacity is

not a fixed value.

UMTS is a hybrid multi-service system. The system capacity is different due to different

service structure and different service model, so we cannot simply use the traffic of a

certain service to monitor the system capacity.



The UMTS may use the hybrid carrier strategy of R99+HSPA. R99 and HSPA share the

system resources, making it more complex to monitor the capacity of R99 and HSPA.

The UMTS is a network focusing on the data service. To judge the data network

congestion, we cannot simply follow the processing of the traditional voice-centric

network, that is, we cannot judge the network congestion according to whether there is a

admission rejection, but should judge the network congestion by combining the HSPA

user’s real-time experience rate with the network resource occupation.

Based on the network management counter of RNC V3.09, this manual gives the

definition of the monitoring indicators of UMTS network load and the suggestions for the

monitoring threshold.

1.2 Main Contents

The high-load network monitoring and optimization guide shall apply to the

communication network in the UMTS commercial operation and maintenance phase.

As shown in Figure 1-1, the high-load network monitoring and optimization transversely

aim at three levels of NEs: the cell of radio access network (RAN), Node B and RNC.

Longitudinally, there are three phases: high-load network monitoring, high-load network

optimization and high-load network expansion, respectively corresponding to the three

parts of this guide.



Figure 1-1 High-Load Network Monitoring and Optimization

1. High-load network monitoring

Horizontal: RNC, NodeB, and cell

User perception evaluation Network resource evaluation

Vertical

2. High-load network optimization

RF

optimization

Parameter optimization (handover threshold,

congestion control, and load balancing)

3. Expansion decision and implementation

Expansion decision -> Expansion implementation

Part 1 corresponds to Chapter 2 of this guide, mainly describing the indicators needed to

be monitored for the network load. As shown in Figure 1-2, the network load monitoring of

WCDMA system mainly aim to three levels of NEs: the cell of wireless access network,

NodeB and RNC. Each NE corresponds to different RAN. Mainly involving the air

interface resources such as the code resource and power resource, the cell NE closely

relates to the user’s experience rate and focuses on the user’s feeling. The Node B NE

mainly involves the transmission resource and CE resource. According to the RNC

configuration, the RNC NE mainly involves the indicators such as the occupation of RCP

and CPU as well as the use of RUP and CE resources.



Figure 1-2 High-Load Network Monitoring Process

High-load network

performance

monitoring and

evaluation

Cell-level monitoring,

analysis, and alarm

NodeB-level

monitoring, analysis,

and alarm

RNC-level monitoring,

analysis, and alarm

Perform

optimization to

solve the problem

of high load

Yes

Meet the cell capacity

expansion requirements

or not?

Meet the NodeB capacity


or not?

Meet the RNC capacity


or not?

Cell expansion

Add carriers or power

amplifiers

NodeB expansion

Add BPC boards or

transmission resources

RNC expansion

Software: Add licenses

Hardware: Add RUB or

RCB boards

No

Yes

Yes

Yes

No

Part 2 corresponds to Chapter 3 of this guide, mainly describing the optimization of the

high-load network performance. There are mainly 2 aspects: the high-load network

optimization process and common optimization methods. As shown in Figure 1-3, in the

optimization process of high-load network, you should optimize the RF and wireless

parameters according to the actual network situation. The wireless parameters

optimization mainly includes the parameters such as the handoff, congestion control,

load equalization, DRBC, power control and HSPA, so as to reduce the consumption of

various resources.



Figure 1-3 High-Load Network Optimization Process

RF optimization

High-load NE

RF neighbor optimization Primary pilot optimization

Vertical

Parameter optimization

Congestion control Load balancing

Cell-level NEs involve false load rises and

real load rises.

Reduce the soft handover ratio Reduce soft handoff overheads

DRBCPower control and HSPA

paremters

Neighbor optimization, only for cell-level NEs

Part 3 corresponds to Chapter 4 of this guide, mainly introducing the high-load network

expansion. As shown in Figure 1-2, the high-load WCDMA network will be respectively

expanded in the three levels of cell, Node B and RNC. The content contains the

expansion analysis process, expansion criteria, expansion methods and implementation

details.

Reading guide: If you want to understand the high-load network optimization measures

given in this guide, please directly go to Chapter 3. If you want to understand the

expansion criteria and methods, please directly go to Chapter 4. Any question about the

counter or indicators, you can directly refer to Chapter 2 or understand by other means.



2 High-Load Network Monitoring

2.1 WCDMA NE Classification

The NE level of WCDMA system can be classified into the RAN cell, Node B, RNC and

CN. We mainly focus on the load monitoring and evaluation of the three NE levels of the

RAN cell, Node B and RNC. For all NEs, we need to consider various scenarios of

service behaviors, find the reasonable monitoring indicators and set the monitoring

threshold, so as to perform the monitoring, alarm and load control.

For the same service behavior, different NE has different monitoring parameters. As to

the air interface, we mainly study the factors such as the cell throughput, single-user

throughput, downlink power, uplink interference and downlink code resource. As to the

NodeB, we mainly consider the utilization of hardware resources.

1. Cell level

The monitoring parameters of the NE in cell level mainly aim at the air interface,

such as the cell throughput, average throughput of HSDPA users, average

utilization of non-HSDPA carrier transmission power, average utilization of

non-HSDPA code resources and the uplink noise rise.

2. Node B level

The NE in Node B level mainly monitors the utilization of Node B hardware

resources, such as the utilization of uplink/downlink Node B CE resources, and the

utilization of Iub interface uplink/downlink bandwidth.

3. RNC level

The NE in RNC level mainly monitors the utilization of hardware resources,

including the CPU load (control plane), CE resource utilization (user plane) and

bandwidth utilization (interface board).



The RNC will also observe the traffic operation indicators of the existing network,

including the Erl, traffic, BHCA and the quantity of online users.

2.2 Network Load Monitoring Indicators

According to the classification of three NE levels of WCDMA system, each NE

respectively corresponds to different monitoring indicators and thresholds of the network

load performance. Please refer to the document attached below.

Expansion Monitoring Indicator System 20110315.xls

Unlike the non-flexible resource and load of Node B and RNC, the cell-level load

monitoring indicators are the most complex, so following we will mainly introduce the

cell-level load monitoring indicators.

2.3 Key Indicators

2.3.1 Average Utilization of Non-HSDPA Code Resource

Average occupancy of cell code resources = Quantity of code resources occupied by all

cell services/Total number of code resources

It basically reflects the overall utilization status of the cell code resources.

Average occupancy of cell non-HSDPA code resources = Quantity of code resources

occupied by non-HSDPA service/Total number of non-HSDPA service code resources

To some extent, it reflects the utilization status of R99 service code resources. The

background network management can directly calculate the average availability of the

cell code resources and the average occupancy of the HSDPA code resources.

According to the two indicators, we can get the statistics formula of the average

occupancy of non-HSDPA code resources, as shown below:



Average occupancy of non-HSDPA code resources = (1 – Average availability of the cell

code resources – Average occupancy of HSDPA code resources)/(1 – Average

occupancy of HSDPA code resources)

For the HSDPA code channel, our system can perform dynamic adjustment according to

the R99 service requirement. When the R99 traffic grows, the system can dynamically

reduce the HSDPA code channels to be the minimum distribution value. So the average

occupancy of non-HSDPA code resources can also be expressed as:

Average occupancy of non-HSDPA code resources = (1 – Average availability of the cell

code resources – Average occupancy of HSDPA code resources)/(1 – Minimum HSDPA

code channel)

For the hybrid carrier cell of R99+HSPA, the maximum code channel of R99 service is

affected by the configuration parameters of HSDPA code channel. When the quantity of

code channels that will be occupied by the R99 service exceeds the maximum of

available code channels of the R99 service, the R99 service will refuse to receive due to

insufficient DCH code resources.

Maximum of available code resources of R99 service = 256 – Quantity of code channels

occupied by common channel – Minimum of HS-PDSCH code channels × 16 – Quantity

of HS-SCCH code channels × 2 – Quantity of E-AGCH code channels × 1 – Quantity of

E-RGCH code channels × 2

Among which, the quantity of code channels occupied by common channel, the minimum

of HS-PDSCH code channels, the quantity of HS-SCCH code channels, the quantity of

E-AGCH code channels and the quantity of E-RGCH code channels come from the

background network management configuration.

Suppose the code channel parameter configuration of the HSPA and common channel is

as shown in Table 2-1.

Table 2-1 Code Resource Distribution of Code Channel

Channel Spreading Code Quantity of Code Channel

HS-PDSCH 16 8 at least

HS-SCCH 128 2



E-AGCH 256 1

E-RGCH 128 1

CPICH 256 1

PCCPCH 256 1

SCCPCH 64 1

PICH 256 1

AICH 256 1

We can see that the maximum of available code resources of R99 service = 256 – 8 – 8 ×

16 – 4 – 1 – 2 = 113. Because the quantity of code resources occupied by common

channel is fixed and small, usually we can ignore it for calculation.

So, when the utilization of cell code resources is very high, and even a congestion of

code resource occurs, we suggest you reduce the minimum of HSDPA code channel to

be 1.

2.3.2 Average Utilization of Non-HSDPA Carrier Transmit Power

The average utilization of cell non-HSDPA carrier transmit power can be calculated by

the statistic indicators in the network management. Here is its definition:

Average utilization of cell non-HSDPA carrier transmit power =Total downlink transmit

power of cell non-HSDPA code / Total downlink available power of cell non-HSDPA

For the hybrid carrier cell of R99+HSPA, when it determines to control the acceptance of

the DCH based on downlink power, one of the determination conditions is:

NOHSDSCHPower + deltaP ≤ R99 admission threshold

Among which, NOHSDSCHPower is the Transmitted carrier power of all codes not used

for HS-PDSCH or HS-SCCH transmission reported by the NodeB.

Currently, the acceptance threshold of R99 is usually set to be 85%, that is, 85% of the

maximum transmit power of the cell. When the RNC determines to accept the DCH

based on downlink power, if there are multiple requests of establishing connection at the

determination time, the system will add the predictive power of all the newly-established

connections based on the existing NOHSDSCHPower, and then compare with the power



acceptance threshold. When the predictive power is bigger than the acceptance

threshold, the system will reject all the requests of establishing connection. If there are

many requests of establishing connection, the predictive power deltaP will be large and it

is easy to refuse to accept.

2.3.3 Uplink Noise Rise

In WCDMA system, all the users share the same carrier, and the users are distinct from

each other by different spreading code and scrambling code. For the uplink, due to the

non-orthogonality of the user scrambling code, each user signal becomes a noise

(interference) to other user signals. Therefore, each signal is included in the broadband

interference background generated by other users. To access a call, the mobile station

power must be large enough to overcome the noise of other mobile stations in the

bandwidth.

The relationship between the uplink capacity and noise rise is as shown in Figure 2-1.

Figure 2-1 Relationship Between the Uplink Capacity and Noise



From the figure you can see that, there is a non-linear relationship between the NodeB

uplink noise rise and uplink capacity (load). When the uplink capacity (load) reaches a

certain threshold, the noise rise will increase sharply. Therefore, the UMTS radio network

planning is based on certain uplink load planning. Generally the uplink load is designed to

be 50%, corresponding to 3db of noise rise. When the uplink load is too large, both the

system uplink coverage and performance will obviously deteriorate due to the sharp

noise rise

The indicator of cell uplink noise rise cannot be calculated directly from the network

management. It formula is defined as follows:

Cell uplink noise rise = Average value of cell carrier received power – System noise floor

2.3.4 Average Throughput of HSDPA Cell

Mainly from the perspective of the total HSDPA throughput, we use the average

throughput of HSDPA cell to evaluate whether the cell is busy, and determine whether

the cell needs to be expanded by considering the Average Throughput of HSDPA Single

User at the same time.

Average throughput of HSDPA cell = Amount of user data confirmed by HSDPA MAC.

The unit is Kb. It indicates the average throughput of HSDPA cell in the data transmission

time.

If the average throughout of HSDPA cell is small, you need to analyze whether it is

because of poor coverage or insufficient transmission, or because the service demand of

the cell user is small, such as QQ online service. If the small data amount of the user

scheduling is caused by poor coverage or insufficient transmission, you need to optimize

in the perspective of coverage so as to improve the overall cell throughput. Only when the

HSDPA cell average throughput is relatively large, you need to further assess the

Average Throughput of HSDPA Single User.

2.3.5 Average Throughput of HSDPA Single User

For the HSDPA data service, except for the traditional indicators such as call connection

rate and call drop rate, there is another more important indicator used to measure the



user experience, that is, user average download rate. When the user experience rate of

the HSDPA users is below expectations, we need to optimize and expand the network.

When the average experience rate of the HSDPA users cannot meet expectations,

except for the possible causes mentioned above that the network coverage is poor or the

transmission bandwidth is insufficient, there is another cause that too many users initiate

the data transmission at the same time. If the low HSDPA user rate is caused by too

many users initiating the data transmission at the same time, we need to optimize and

expand the network. HS-PDSCH is a shared physical channel, and the transmission

bandwidth is shared by all the HSDPA users. If too many users initiate the data

transmission at the same time, the real-time transmission rate of each HSDPA user will

reduce. Therefore, except for the indicator of HSDPA user real-time experience rate, the

system should also provide the indicator of real-time transmission HSDPA user quantity,

which is used to judge whether the low real-time transmission rate of each HSDPA user

is caused by too many HSDPA users initiating the data transmission at the same time.

The Average Throughput of HSDPA Single User is defined as follows:

Average throughput of HSDPA single user (Kbps) = Amount of user data confirmed by

HSDPA MAC/Data transmission time of HSDPA users



3 High-Load Network Optimization

3.1 Network Load Optimization Stages

High-load network will cause many problems such as the access failure, handover failure,

call drop and HSPA low rate, badly affecting the user experience and thus needing to be

optimized or expanded urgently. Figure 3-1 shows the high-load network optimization

stage, that is, after the network load rise and before the network expansion. When the

network load is monitored to be high, we first need to optimize to reduce the network load.

If the load is still relatively high after the network optimization, we need to prepare for

expansion.

Figure 3-1 Flowchart of Network Load Optimization

1. High-load network monitoring

Horizontal: RNC, NodeB, and cell

User perception evaluation Network resource evaluation

Vertical

2. High-load network optimization

RF

optimization

Parameter optimization (handover threshold,

congestion control, and load balancing)

3. Expansion decision and implementation

Expansion decision -> Expansion implementation



3.2 Network Load Optimization Process

The network load optimization process is as shown in Figure 3-2. Actually the

optimization of high-load network aims to the cell air interface resources. The cell load

rise can be solved by RF optimization and parameter optimization. The RF optimization

mainly aims to the coverage, neighbor cell and interference optimization, so as to reduce

the excessive resource consumption resulted from overshooting, pilot pollution and

high-proportion switching. The parameter optimization includes the switching threshold

optimization, control methods of congestion acceptance (refuse and preempt), load

control, DRBC, power control and HSPA related parameters, as well as the intra-system

and inter-system cell load equalization. These optimizations can not only reduce the cell

load, some optimization methods can also reduce the Node B and RNC load, such as the

switching and DRBC downspeeding. Relatively speaking, the load rise of Node B and

RNC belongs to the consumption of its own hardware resource.

Please note that, some optimization methods are especially for some kind of resource or

indicator, but may have a negative impact on another resource or indicator. For example,

by reducing the HSDPA code resource we can reduce the non-HSDPA code resource

utilization and R99 service congestion, but meanwhile the HSDPA service rate and user

experience will also be reduced.

So during the optimization, we need to comprehensively consider the balance of various

optimization methods and assessment indicators. If there are still some indicators being

limited after the optimization, we need to prepare or implement the expansion.



Figure 3-2 High-Load Network Optimization Process

RF optimization

High-load NE

RF neighbor optimization Primary pilot optimization

Vertical

Parameter optimization

Congestion control Load balancing

Cell-level NEs involve false load rises and

real load rises.

Reduce the soft handover ratio Reduce soft handoff overheads

DRBCPower control and HSPA

paremters

Neighbor optimization, only for cell-level NEs



4 High-Load Network Expansion

According to the development experience of the fixed broadband network, the data

service will grow explosively when it comes to a certain stage. But when will the explosive

turning point come relates to the tariff policies, terminal development status, network

quality and user behaviors, and thus it is difficult to predict. Therefore, we suggest that

the expansion indicator threshold setting can be divided into two stages: the monitoring

threshold and expansion threshold. In this way sufficient space can be left for the

expansion. The monitoring threshold means that, when the indicator reaches this

threshold, you need to prepare related expansion resources. When the expansion

threshold is reached, you need to implement corresponding expansion actions.

We also suggest you pay attention to relevant factors such as the tariff, terminal, network

quality and publicity. When relevant strategies change, you should consider the

possibility of expanding the network in advance.

4.1 Expansion Process

4.1.1 Expansion Analysis Process

For the network expansion, you can begin with the network load monitoring, respectively

perform corresponding monitoring, analysis and alarm for each level of NE, and expand

the NEs meeting the expansion criteria by proper expansion methods. The expansion

analysis process is as shown in Figure 4-1.



Figure 4-1 Expansion Analysis Process

High-load network

performance

monitoring and

evaluation

Cell-level monitoring,

analysis, and alarm

NodeB-level

monitoring, analysis,

and alarm

RNC-level monitoring,

analysis, and alarm

Perform

optimization to

solve the problem

of high load

Yes

Meet the cell capacity


or not?

Meet the NodeB capacity


or not?

Meet the RNC capacity


or not?

Cell expansion

Add carriers or power

amplifiers

NodeB expansion

Add BPC boards or

transmission resources

RNC expansion

Software: Add licenses

Hardware: Add RUB or

RCB boards

No

Yes

Yes

Yes

No

4.2 Expansion Criteria and Methods

For the WCDMA system, the high-load network expansion needs to respectively aim to

three NEs of the RAN cell, Node B and RNC. The cell load level only reflects the load

status of the cell itself to some extent. A Node B can have many cells and the different

quantity of cell results in different load of Node B. If a Node B contains too many cells,

although the cell itself does not have too much load, the Node B’s load may exceed the

limit. Similarly, the RNC load is affected by the quantity of its Node B and cells. So you

need to assess all the three NEs, and formulate different expansion criteria and methods

correspondingly.

The expansion criteria mainly include the expansion threshold and expansion

assessment formula, and the expansion methods respectively correspond to the limit of

different NEs and resources.

4.2.1 Cell Expansion

Among the three NEs, the WCDMA system cell is the NE closest to the actual users and

the minimum unit used to assess the network load. The cell load and performance level

directly affects the user experience, so the cell load monitoring and assessment will be

the key point in our daily monitoring and assessment, and the cell expansion is also the

core content of the WCDMA network expansion.



4.2.1.1 Cell Expansion Decision Process

As shown in Figure 4-2, the cell load decision focuses on the user experience, and

decides the cell load by combining the utilization of network resource indicators.

Figure 4-2 Cell Expansion Decision Process

Network load monitoring

Low transmission

rate and

congestion

Resource utilization

evaluation: code resources

and power resources

False load rise Real load rise

Optimization

To evaluate user perception:

Average packet user-perceived rate;

Uu interface congestion conditions

To evaluate network resources:

Utilization rates of UL and DL power

resources;

Utilization rate of code resources

High-load decision

Expansion

No

Yes

Low resource utilization rates High resource utilization rates

Yes

No

The indicators of assessing the user experience are mainly the data user experience rate

and cell resource congestion level. The network resources mainly refer to the air interface

code resource and power resource. For details please refer to the cell indicators

mentioned in Section 2.2.

4.2.1.2 Expansion Thresholds and Methods

The user experience is the most direct and effective reflection of the network load level.

In the past, the user experience was mainly assessed by some traditional indicators such

as the call connection rate and call drop rate. But for the 3G network, the increase of data

service users is an inevitable trend and the data service proportion will be bigger and



bigger. Therefore, the user experience of data service will also become the most

important factor to measure the 3G network load, and the best indicator to assess the

user experience of data service is the user download experience rate of data service.

According to the expansion principle of ―Focus on the user experience‖, we will regard

the HSDPA user average experience rate (throughput) as the core to assess the cell load,

and try to accurately assess the cell load by combining the air interface.

Each monitoring indicator of the cell load assessment has been set an expansion

indicator number. The expansion indicator SPI is a logical indicator, and the value can

only be 0 or 1. When the expansion indicator SPI reaches the threshold, the value will be

1, or else 0. We also provide corresponding expansion methods when each indicator

reaches the expansion threshold, for your reference.

Table 4-1 Cell Expansion Thresholds

Expansion

Indicator

No.

Indicator Name Alarm

Threshold

Expansion

Threshold Expansion Method

SPI1

Average

Throughput of

HSDPA Single

User

≤1 Mbps ≤512 Kbps

HSPA+/Multi-carrier/add

NodeB

SPI2

HSDPA cell

average

throughput

≥100 MB ≥150 MB

SPI4

Non-HSDPA code

resource average

occupancy

≥60% ≥70% Multi-carrier/add NodeB

SPI5

Average

utilization of

non-HSDPA

carrier transmit

power

≥60% ≥70% Expand power

amplifier/add NodeB

SPI6 Uplink noise rise ≥6 dB ≥8 dB Multi-carrier/add NodeB



SPI8

Admission

rejection

proportion due to

limited downlink

code resources

Set to be a

fixed

value: 1

≥2% Multi-carrier/add NodeB

SPI9

Admission

rejection

proportion duo to

limited downlink

power TCP

Set to be a

fixed

value: 1

≥2% Expand power

amplifier/add NodeB

According to the threshold setting of the cell load monitoring indicator SPI and the cell

expansion assessment process, we can get the combination chart of the cell expansion

decision formula, as shown in Figure 4-3.



Figure 4-3 Combination Chart of Cell Expansion Decision Formula

High-load cell decision

User perception evaluation

Network resource evaluation

SPI1 × SPI2 = 1

The cell has a heavy PS

service load and a low user-

perceived transmission rate;

the cell may be a high-load cell.

SPI8 × SPI9 = 1

The cell has severe congestion

and user perception is bad; the

cell may be a high-load cell.

SPI × SPI2 = 1

SPI4 × SPI8 + SPI5 ×

SPI9 + SPI6 × (SPI4 +

SPI5) > 1

The cell has a high network

resource utilization rate and a

high PS service load; user

perception about PS service is

bad. Hence this cell is a high-

load cell.

The cell has a high resource

utilization rate and a high non-

HSDPA service load; user

perception about access is bad.

Hence this cell is a high-load

cell.

Yes Yes

Optimization

Real load rise

No

False load rise

From above we can get the general formula of the high-load cell decision:

S_cell = SPI1 × SPI2 + SPI4 × SPI8 + SPI5 × SPI9 + SPI6 × (SPI4 + SPI5)

Formula description:

1. S_cell is the cell load index.

2. SPI1 × SPI2 is mainly used to filter the high-load cell focusing on the data service,

that is, need to meet the requirements of low user rate and high cell throughput.



3. SPI4 × SPI8 + SPI5 × SPI9 + SPI6 × (SPI4 + SPI5) is mainly used to filter the

high-load cell focusing on the non-HSDPA service. The purpose of SPI1 × SPI2 is to

perform mutual correction of two counters. Two SPIs meeting the criteria can

basically determine that the cell is in a high-load state.

SPI4 × SPI8 means the average utilization of non-HSDPA code resources is

relatively high and the situation of refusing to accept is serious. If the average

utilization of non-HSDPA code resources is relatively high but there is no situation of

refusing to accept, it means that, although the load is high, it does not meet the

expansion criteria. If the situation of refusing to accept is serious but the average

utilization of non-HSDPA code resources is not high, it may be caused by the virtual

load rise due to improper resource allocation.

SPI5 × SPI9 means the same as SPI4 × SPI8.

SPI6 × (SPI4 + SPI5) means at least two indicators meet the criteria. There are two

causes, one is that the uplink may be interfered, and the other is that the automatic

noise floor update is false. So we use the two indicators of the code resource and

power resource to correct, so as to ensure the cells we filtered are really the cells

with relatively high load.

4. When S_cell > 0, it means that the cell enters a high-load state and needs to be

expanded, and we need to perform monitoring optimization and load assessment.

5. The bigger value of S_cell means the heavier load of the current cell. The minimum

of S_cell is 0 and the maximum is 5.

4.2.1.3 Threshold Setting Methods and Foundations

For different networks, the expansion thresholds may be different. Following is the brief

introduction to the threshold setting of each indicator.

4.2.1.3.1 Average Occupancy of Non-HSDPA Code Resources

As shown in Figure 4-4, for the cell with the CS traffic of the whole network in a certain

area greater than 1Erl, the average occupancy of non-HSDPA code resources reflects

the cell R99 traffic level to some extent, and is in proportional to the cell CS traffic. So in



the cell load assessment, when the indicator of average occupancy of non-HSDPA code

resources is used, it means the indicator of CS traffic is indirectly used too. The average

occupancy of non-HSDPA code resources not only reflects the occupancy of cell R99

code resources and the situation of refusing to accept, but also reflects the cell CS traffic

load level.

Figure 4-4 Relationship Between the Code Resource Utilization and Traffic

4.2.1.3.2 Average Utilization of Non-HSDPA Carrier Transmit Power

In some networks, when the average utilization of non-HSDPA carrier transmit power is

greater than 40%, there will be a situation of refusing to accept due to the limited

downlink power. It relates to the measurement and decision cycle of refusing to accept —

2 ms. If too many services are accepted in 2 ms at the same time, it will cause the

situation of refusing to accept.



Figure 4-5 Relationship Between the Cell Carrier Transmit Power Utilization and TCP

Limited Proportion

4.2.1.3.3 Uplink Noise Rise

Definition of uplink noise rise: Total average received power of cell uplink-RTWP NodeB

noise floor

Currently ZTE uplink acceptance control switch is closed, but the HSUPA scheduling is

controlled by the parameter of MaxRTWP. The default configuration of MaxRTWP is 6dB.

We suggest setting the expansion threshold of the uplink noise rise to be 8dB

(corresponding to 85% uplink loads). Theoretically, 6dB means the cell has 75% uplink

loads, obviously not indicating a high-load load. But 8dB corresponds to 85% uplink loads.

So we suggest setting the expansion threshold of the uplink noise rise to be 8dB and

setting the alarm threshold to be 6 dB.

4.2.1.3.4 HSDPA User Average Throughput & HSDPA Cell Average Throughput

When the real-time experience rate of the HSDPA users cannot meet expectations due to

the capacity reason, we need to expand the network capacity. The real-time experience

rate of HSDPA users can be directly obtained from the network management background.

Besides, the low HSDPA user rate may be caused by the poor coverage, insufficient

transmission bandwidth and heavy network load. We need to expand the network

capacity only when the low HSDPA user rate may be caused by the heavy network load.

Therefore, except for monitoring the Average Throughput of HSDPA Single User, we also



need to monitor the HSDPA cell average throughput, and use the two indicators to

determine whether the network capacity needs to be expanded.

When the Average Throughput of HSDPA Single User is less than 512 Kbps, we need to

make the next-step decision of the capacity monitoring.

The HSDPA cell average throughput indicates the service volume of cell data

transmission. The HSDPA cell average throughput is too low may be because the

application layer flow is not enough or the cell coverage is poor. In this situation, we

should not perform the expansion. Therefore, we suggest considering the expansion

when the HSDPA cell average throughput > 150 MB.

In general, when the Average Throughput of HSDPA Single User is less than 512 Kbps

and the HSDPA cell average throughput is greater than 150 MB, the cell capacity should

be expanded.

4.2.1.3.5 Admission Rejection Proportion

When the call congestion ratio is over 2%, the user experience will be badly affected.

Therefore, we set the alarm and expansion threshold of this KPI as 2%.

4.2.1.4 Expansion Implementation Rules

The NodeB expansion implementation rules mainly set the hour as the granularity. The

monitoring and assessment cycle is 1 week. Because each cell has different user

behavior and different busy hours, we recommend implementing 7 × 24 hour monitoring

mode. The implementation rules are as shown in Table 4-2.

Table 4-2 Cell Expansion Implementation Rules

Monitoring

Mode Monitoring Mode 1 Monitoring Mode 2

Monitoring

Object Cell of the whole network Cell of the whole network

Monitoring

Granularity Hour Hour



Monitoring

Cycle A week (7 × 24)

A week (7 × N: N refers to the fixed

busy hours of each day, and the

busy hour is set according to the

existing network state.)

Alarm

Monitoring

Trigger

Condition

Utilization alarm threshold:

If in 1 week, S_cell > 0, N ≥ 10,

perform the monitoring

optimization and expansion

assessment.

Utilization expansion threshold:


add to the cell list of monitoring


assessment.



perform the monitoring optimization

and expansion assessment.


If in 1 week, S_cell > 0, N ≥ 3, add

to the cell list of monitoring


assessment.

Expansion

Trigger

Condition


Suppose Sn is the expansion

index, Sn = S_cell_1 + S_cell_2

+ ……S_cell_n (n = 7 × 24).

When S ≥ 10, expand the cell.

Actually, the formula means, Sn

is the sum of S_cell meeting the

criteria (S_cell > 0).

Greater Sn indicates greater cell

expansion demand.


Suppose Sn is the expansion index,

Sn = S_cell_1 + S_cell_2

+ ……S_cell_n (n = 7 × 24).


Actually, the formula means, Sn is

the sum of S_cell meeting the

criteria (S_cell > 0).


expansion demand.

4.2.2 Node B-CE Expansion

Node B NE lies in the intermediate level of the 3-level NEs, mainly providing the

baseband resource pool for the cell and performing the data transmission of the cell. This

section mainly introduces the NodeB CE resource expansion.

4.2.2.1 CE Expansion Thresholds and Methods

The Node B expansion mainly inspects the shared resource utilization of the cell under

Node B, for example, the CE resource and transmission resource. This section mainly

introduces the CE resource.



The Node B CE resource load assessment is as shown in the table. An indicator number

SPI is set for each monitoring indicator. The expansion indicator SPI is a logical indicator

and its value can only be 0 or 1. When the indicator reaches the expansion threshold, the

value will be 1, or else 0. Meanwhile, we provide the expansion method corresponding to

each indicator reaching the expansion threshold. The expansion threshold and method

are as shown in Table 4-3.

Table 4-3 Node B CE Expansion Thresholds and Expansion Methods

Expansion

Indicator

No.


Threshold

Expansion

Threshold

Expansion

Method

SPI11 Average utilization of

uplink NodeB CE resource 60% 70% Expand the

BPC board

Expand the

BPC board SPI12

Average utilization of

downlink NodeB CE

resource

60% 70%

SPI13 Maximum utilization of

uplink NodeB CE resource 80% 90%

Expand the

BPC board

SPI14

Maximum utilization of

downlink NodeB CE

resource

80%% 90% Expand the

BPC board

SPI15 Admission rejection rate of

uplink CE

Set as a

fixed

value: 1

≥2% Expand the

BPC board

SPI16 Admission rejection rate of

downlink CE

Set as a

fixed

value: 1

≥2% Expand the

BPC board

According to the expansion threshold setting shown in Table 4-3, we use the expansion

decision formula to assess the Node B load and expansion demand.

S_nodeb_CE = (SPI11 + SPI3) × SPI15 + (SPI12 + SPI4) × SPI16


1. S_nodeb_CE is the Node B CE expansion index.



2. (SPI11+SPI3) × SPI15 is mainly used to filter the uplink CE high-load cell, indicating

that the uplink average or maximum utilization is relatively high, and meanwhile the

uplink CE refuses to accept. If there is only high utilization but no CE admission

rejection, it means the indicator does not reach the expansion threshold. If there is

only admission rejection but no high utilization, it may be caused by uneven

distribution of resources.

3. (SPI12+SPI4) × SPI16 is the same as above.

When S_nodeb_CE > 0, it means the NodeB enters a high-load state and falls into our

monitoring scope for monitoring optimization and expansion assessment.

Greater value of S_nodeb_CE means greater Node B expansion demand. The minimum

of S_node_CE is 0 and the maximum can be 2.

4.2.2.2 Expansion Threshold Setting Method and Foundation

When the average utilization of CE resources is 70%, we think the NodeB is in a

high-load state and needs to be expanded. But as shown in Figure 4-6 and Figure 4-7,

due to the independence of uplink and downlink CE resource, in the high-load state, the

uplink CE resource utilization of some networks is much larger (even twice) than

downlink CE resource utilization. So we need to perform joint monitoring for the uplink

and downlink CE resource indicators but expand the uplink and downlink CE resources

respectively.

Figure 4-6 Average Utilization Rates of Uplink and Downlink NodeB CE Resources in

Shapingba, Chongqing, China



Figure 4-7 Maximum Utilization Rates of Uplink and Downlink NodeB CE Resources in

Shapingba, Chongqing, China


The NodeB expansion implementation rules mainly set the hour as the granularity. The

monitoring and assessment cycle is 1 week. Because each NodeB has different user

behavior and different busy hours, we recommend implementing 7 × 24 hour monitoring

mode. The implementation rules are as shown in Table 4-4.


Monitoring


Monitoring


Monitoring


Monitoring








Monitoring


Alarm

Monitoring

Trigger

Condition


If in 1 week, S_nodeb_CE > 0, N

≥ 10, perform monitoring


assessment.


If in 1 week, S_nodeb_CE > 0, N

≥ 10, add to the NodeB list of

monitoring optimization and

expansion assessment.


If in 1 week, S_nodeb_CE > 0, N ≥

3, perform monitoring optimization



If in 1 week, S_nodeb_CE > 0, N ≥

3, add the NodeB list of monitoring


assessment.

Expansion

Trigger

Condition


Suppose Sn is the expansion

index, Sn = S_nodeb_CE_1 +

S_nodeb_CE_2

+ …S_nodeb_CE_n (n = 7 × 24).



is the sum of S_nodeb_CE

meeting the criteria

(S_nodeb_CE > 0).


expansion demand.


Suppose Sn is the expansion index,

Sn = S_nodeb_CE_1 +

S_nodeb_CE_2

+ …S_nodeb_CE_n (n = 7 × 24).



the sum of S_nodeb_CE meeting

the criteria (S_nodeb_CE > 0).


expansion demand.

4.2.3 IUB Transmission Expansion

The IUB expansion also belongs to the second level of the radio network, responsible for

the data transmission. Its capacity constraint will directly affect each KPI.

4.2.3.1 IUB Interface Transmission Expansion Thresholds and Methods

The IUB resource load assessment is as shown in the table. The expansion indicator

number SPI is set for each monitoring indicator. The expansion indicator SPI is a logical

indicator and the value can only be 0 or 1. When the indicator reaches the threshold, the

value will be 1, or else 0. The corresponding expansion method is also provided here for



your reference when each indicator reaches the expansion threshold. The expansion

threshold and methods are as shown in Table 4-5.

Table 4-5 Iub Transmission Expansion Thresholds

Expansion

Indicator

No.


Threshold

Expansion

Threshold

Expansion

Method

SPI17

Maximum forward

accepted bandwidth

proportion of IP

80% 90%

Expand the

transmission.

SPI18

Maximum backward

accepted bandwidth

proportion of IP

80% 90%

SPI19 Average forward accepted

bandwidth proportion of IP 60% 70%

Expand the

transmission.

SPI20

Average backward

accepted bandwidth

proportion of IP

60% 70% Expand the

transmission.

SPI21

Maximum forward

accepted bandwidth

proportion of ATM

80% 90% Expand the

transmission.

SPI22

Maximum backward

accepted bandwidth

proportion of ATM

80% 90% Expand the

transmission.

SPI23

Average forward accepted

bandwidth proportion of

ATM

60% 70% Expand the

transmission.

SPI24

Average backward

accepted bandwidth

proportion of ATM

60% 70% Expand the

transmission.

For SPI17–24 in the above table, we need to start the measurement on the OMCB for at

least 1 week, and then close.

According to the expansion threshold setting in the above table, we can use the

expansion decision formula to assess the IUB transmission load and the expansion

demand, as shown below:



S_trans = SPI17 + SPI18 + SPI19 + SPI20 + SPI21 + SPI22 + SPI23 + SPI24


S_trans refers to the IUB transmission expansion index.

When S_trans>0, it means the transmission enters a high-load state and falls into our

monitoring scope for monitoring optimization and expansion assessment.

A bigger value of S_nodeb means bigger expansion demand of the IUB transmission.

The minimum of S_trans is 0 and maximum is 8.

4.2.3.2 Expansion Threshold Setting Methods and Foundations

In a high-load state, the expansion threshold of the Iub interface uplink and downlink

transmission bandwidth utilization should be 70% of the total transmission bandwidth.


The IUB expansion implementation rules mainly set the hour as granularity, and the

monitoring and assessment cycle is 1 week. Because each NodeB user has different

behavior and different busy hour, we recommend implementing the 7 × 24 hour

monitoring, and the monitoring implementation rules are as shown in Table 4-6.


Monitoring


Monitoring


Monitoring


Monitoring








Monitoring


Alarm

Monitoring

Trigger

Condition


If in 1 week, S_trans > 0, N ≥ 10,



assessment.



add to the NodeB list of

monitoring optimization and

expansion assessment.



perform the monitoring optimization



If in 1 week, S_trans > 0, N ≥ 3, add

to the NodeB list of monitoring


assessment.

Expansion

Trigger

Condition


Suppose the expansion index is

Sn, Sn = S_trans_1 +

S_trans_2 + ……S_trans_n (n =

7 × 24 hrs).



is the sum of S_trans meeting the

criteria (S_trans > 0).


expansion demand.


Suppose the expansion index is Sn,

Sn = S_trans_1 + S_trans_2

+ ……S_trans_n (n = 7 × 24 hrs).



the sum of S_trans meeting the

criteria (S_trans > 0).


expansion demand.

4.2.4 RNC Expansion

The RNC is at the highest level of the radio network, responsible for the work scheduling

and processing of NodeBs and cells in its charge.

In the perspective of software and hardware constraints, the RNC expansion can be

divided into RNC hardware expansion and RNC software expansion.

RNC hardware expansion refers to the expansion triggered by the constraint of RNC

hardware processing capability. The expansion can be performed by increasing the

hardware boards.



RNC software expansion means that the software license is close to or reaches the

committed capacity and thus the expansion is triggered. The expansion can be

performed by increasing the software licenses.

The RNC hardware expansion and software expansion may occur at the same time or

occur respectively. Their association depends on the project hardware configuration

mode and the software quotation mode. We need to monitor each project respectively

according to related parameters of the RNC hardware expansion and RNC software

expansion.

In the perspective of modeling configuration, the RNC expansion can be divided into

modeling expansion and non-modeling expansion.

The modeling expansion means that the RNC hardware and software use the modeling

configuration quotation. The expansion will be performed in the unit of model.

The non-modeling expansion means that the RNC hardware and software do not use the

modeling configuration quotation. The expansion will be performed in the unit of board.

4.2.4.1 Expansion Thresholds and Method

4.2.4.1.1 RNC Hardware Expansion

The RNC hardware can be classified into the common hardware, capacity hardware and

interface hardware.

Expansion of common hardware:

The common hardware mainly includes rack, frame and common board.

Rack: The rack expansion depends on the quantity of frame. Each 4 frames need 1

rack.

Frame: including the control frame, resource frame and exchange frame

The expansion of control frame depends on the increase amount of the control

plane processing board RCB. When there is the exchange frame, the main

control frame can be inserted 6 RCBs, and the rest can be inserted 14. When



there is no exchange frame, the main control frame can be inserted 2 RCBs

and the rest can be inserted 14.

The expansion of resource frame depends on the increase amount of the user

plane processing board RUB and the interface board. Each resource frame

can be inserted 15 RUBs and interface boards.

For the exchange frame, the system configures 1 exchange frame at most.

When there are more than 2 resource frames, the exchange frame must be

configured. When there are 2 or less resource frames, it is defaulted and

recommended to configure the exchange frame.

Common board: including the global processing board and system exchange board

Global processing boards: including ROMB, CLKG and SBCX. The quantity is

a fixed configuration and has nothing to do with the capacity, so usually there is

no issue of expansion. If no active and standby boards are divided at the

beginning, later we need to expand them to be active and standby according to

the operation’s requirement.

System exchange boards: including THUB, GUIM, UIMC, PSN and GLI.

Configuring a pair of THUB for the whole RNC is a fixed configuration. A pair of

GUIM is configured for each resource frame. A pair of UIMC is configured for

each control frame or exchange frame. A pair of PSN is configured for each

exchange frame. A pair of GLI is configured for every 2 resource frames.

Expansion of capacity hardware:

The capacity hardware can be divided into the control plane processing board RCB and

the user plane processing board RUB.

The monitoring indicators of control plane hardware expansion (RCB expansion)

include:

i. RCP CPU load

ii. NodeB quantity



iii. Cell quantity

The monitoring indicators of user plane hardware expansion (RUB expansion)

include:

RUP CE resource utilization

The monitoring indicators of the hardware expansion of RNC capacity hardware resource

are as shown in Table 4-7.

Table 4-7 Monitoring Indicators of RNC Hardware Expansion

Indicator

No. Indicator Name

Monitoring

Threshold

Expansion

Threshold

Expansion

Method

SPI31 Average utilization of

RUP CE resources 60% 70%

Expand the

RUB board.

SPI32 Maximum utilization of

RUP CE resources 80% 90%

Expand the

RUB board.

SPI33 RCP CPU average load 60% 70% Expand the

RCB board.

SPI34 RCP CPU peak load 80% 90% Expand the

RCB board.

NodeB quantity 140/pair of RCB Expand the

RCB board.

Cell quantity 420/pair of RCB Expand the

RCB board.

For the NodeB quantity and cell quantity, we do not set the monitoring counter. When

expand the NodeB, we need to assess whether the RCB needs to be expanded.

For the utilization of RUB CE resources and the load of RCB CPU, we need to set the

monitoring indicators.

An expansion indicator number (SPI31–34) is set for each monitoring indicator, and the

value can only be 0 or 1. When the indicator reaches the expansion threshold, the value

will be 1, or else 0.



According to the expansion threshold setting in the table, we can assess the RNC load

and expansion demand by the expansion decision formula, as shown below:

S_hard_Ctrl = SPI31 × (1 + SPI32)

S_hard_User = SPI33 × (1 + SPI34)


S_hard is the RNC expansion index, and the value can be 0, 1 and 2.

When S_hard = 0, it means neither the peak nor average value meets the criteria. So we

do not need to expand.

When S_hard = 1, it means the average value meets the criteria but the peak does not,

and the RNC enters a high-load state. So we need to expand the control plane or the

user plane.

When S_hard = 2, it means both the peak and average value meet the criteria, and the

expansion is urgent.

Except for the monitoring indicators mentioned above, we can also set some observation

indicators to observe the actual network service state when the hardware is close to or

reaches the expansion threshold, as shown in Table 4-8.

Table 4-8 Observation Indicators of RNC Hardware Expansion

Observation Indicator

Name

Related Monitoring

Indicator Affected Board

BHCA SPI33/SPI34 RCB board

CS traffic SPI31/SPI32 RUB board

PS flow SPI31/SPI32 RUB board

Quantity of online users SPI31/SPI32/SPI33/SPI34 RCB board and RUB board

Expansion of interface hardware:

There are several factors causing the interface hardware expansion, including:

1. Capacity



2. Separation of logical interface

3. For example, in a Unicom project, the Iu/Iub interfaces in many provinces share the

IP interface board in the beginning, later it is required that the interface boards of

Iu/Iub interfaces should be separated. Therefore, we need to separately expand the

interface boards without changing the capacity hardware. This kind of expansion is

resulted from the operator’s requirement and does not need any expansion

foundation. We just need to re-calculate the flow of each interface after separation.

4. Change of interface type

5. For example, the ATM interface boards are used previously, now we need to

increase the IP interface boards because the network develops to the all-IP

technology. This kind of expansion is resulted from the operator’s requirement and

does not need any expansion foundation. We just need to re-calculate according to

the new interface board algorithm.

6. Quantity increase of NEs or Ports

7. Many kinds of interface boards are related to the quantity of NEs and ports. For

example, the interface boards will be increased by increasing the NodeB quantity,

increasing the E1 quantity for each NodeB, increasing the Iur quantity, or increasing

the Iu-flex function. In this case, we need to re-calculate the quantity of interface

boards according to the new NodeB/port demands.

8. Change of redundancy protection mode

9. It is also triggered by the operator’s demand. For example, we calculate the

interface boards only according to the flow redundancy in the beginning, later the

operator requires the port redundancy or board redundancy, or requires both the

interfaces and boards are configured in 1+1 mode. We need to increase according

to the demand.

For Case 2 to Case 5 mentioned above, we do not need to set the monitoring indicators,

and perform the expansion correspondingly when it is necessary. For Case 1, we need to

monitor the bandwidth usage of the interface boards. The monitoring parameters are as

shown in Table 4-9.



Table 4-9 Observation Indicators of RNC Hardware Expansion

Indicator Name Monitoring

Threshold

Expansion

Threshold

Expansion

Method

Average bandwidth utilization in the

ATM interface board transmit direction 70% 80%

Expand the

ATM interface

board

Average bandwidth utilization in the

ATM interface board receiving direction 70% 80%

Expand the

ATM interface

board

Average bandwidth utilization in the IP

interface board transmit direction 70% 80%

Expand the IP

interface board

Average bandwidth utilization in the IP

interface board transmit direction 70% 80%

Expand the IP

interface board

Maximum bandwidth utilization in the

IP interface board transmit direction 70% 90%

Expand the IP

interface board

Maximum bandwidth utilization in the

IP interface board transmit direction 50% 90%

Expand the IP

interface board

4.2.4.1.2 RNC Software Expansion

The RNC software expansion is closely related to the quotation means of software

feature. Each project has different quotation unit of the software feature, and in the same

project, different software has different quotation unit.

Software expansion in the dimensions of NodeB quantity and cell quantity:

Some projects and some features are quoted in the units of NodeB quantity and cell

quantity. If the NodeB quantity and cell quantity exceed the quotation quantity, we need

to perform the software expansion.

For example, in one project, the RNC hardware can support 210 cells and has 100 cells

actually, and the software feature is quoted 100cells. Then, the increase of cell quantity

will trigger the software expansion. When there are almost 210 cells, we need to trigger

both the software expansion and hardware expansion at the same time.

Software expansion in the dimension of NodeB CE:



In some projects, some features are quoted in the unit of NodeB’s CE. So we need to

monitor the CE operating indicators of all the NodeBs, and should trigger the software

expansion when the indicators exceed the quotation unit. (For the monitoring indicators

please refer to CE Monitoring Indicators of NodeB)

Software expansion in the dimensions of Erl and flow:

In some projects, some features are quoted in the unit of Erl and flow. So we need to

monitor the indicators of Erl and flow, and should trigger the software expansion when

the indicators exceed the quotation unit. (For the monitoring indicators, please refer to

RNC Hardware Expansion Observation Indicators.)

For example, in one project, the RNC hardware configuration is 250 Mbps and software

is quoted 100 Mbps. When the flow indicator of existing network exceeds 100 Mbps, we

need to expand the software license, that is, to quote the software feature for the

increased flow. When the flow is almost 250 Mbps, we need to perform the hardware

expansion.

4.2.4.1.3 Modeling Expansion and Non-Modeling Expansion

For both the software expansion and hardware expansion, there are two methods:

modeling expansion and non-modeling expansion. To use which method depends on

whether the modeling method is used in the preliminary software and hardware

configuration quotation.

For the software expansion, the different between the modeling expansion and

non-modeling expansion only lies in the expansion granularity. The modeling expansion

must be based on the model granularity.

For the hardware expansion, except for different expansion granularity, the difference

between the modeling expansion and non-modeling expansion also lies in whether the

user plane, control plane, and interface board are bound.

If the non-modeling method is used, the control plane, user plane and interface board can

be expanded respectively. For example, in one project, if the RCP CPU is monitored to

be a little bit high-load but other indicators are normal, we only need to expand the RCB

and do not need to add the RUB or interface board. Similarly, if the user plane and



interface board are monitored to be load-rising, we can also expand the RUB or interface

board separately.

If the modeling method is used, the control plane and user plane boards need to be

linked according to the model. In some projects, the interface board is also contained in

the model, so we need to link the control plane, user plane and interface board. For

example, in one project, if the RCP CPU is monitored to be a little bit high-load but other

indicators are normal, we need to expand the whole model to the upper capacity level but

not only to expand the RCB.

4.2.4.2 Expansion Threshold Setting Foundation

When the average utilization of RUP CE resources reaches 70% and the average load of

CPU reaches 70%, it means the RNC becomes high-load and needs to be monitored and

assessed for expansion.


In the WCDMA network, the RNC’s reflection during busy hours is relatively obvious and

uniform, so we can monitor the RNC load in two ways, as shown in Table 4-10.

Table 4-10 RNC Expansion Implementation Rules

Implementation Rule 1 Implementation Rule 2

Monitoring

Object RNC of the whole network RNC of the whole network

Monitoring


Monitoring

Cycle A week (7 × 24) A week (busy hours of each day)

Monitoring

Trigger

Condition

If in 1 week, S_hard ≥ 1, N ≥ 10,



assessment.




assessment.



Expansion

Trigger

Condition


perform the capacity expansion.


perform the capacity expansion.

zte umts load-monitoring and expansion guide

Engineering