UMTS Network Load Monitoring
and Expansion Guide
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UMTS Network Load Monitoring and Expansion Guide
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UMTS Network Load Monitoring and Expansion Guide
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Revision History
Product Version
Document Version
RNC V3.09
Serial Number
R1.0
Reason for Revision
First published
Author
Date
2011-3-15
Document
Version
R1.0
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Prepared by
Qiao Bin, Jin
Zhengtuan, and
Xu Yi
Reviewed by
Ma Wei
© 2013 ZTE CORPORATION. All rights reserved.
Approved by
Wang Zhenhai
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UMTS Network Load Monitoring and Expansion Guide
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Intended audience: UMTS network optimization engineers
Proposal: Before reading this document, you had better have the following knowledge and skills.
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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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UMTS Network Load Monitoring and Expansion Guide
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TABLE OF CONTENTS
1
1.1
1.2
Overview ......................................................................................................... 1
Background ...................................................................................................... 1
Main Contents .................................................................................................. 2
2
2.1
2.2
2.3
2.3.1
2.3.2
2.3.3
2.3.4
2.3.5
High-Load Network Monitoring...................................................................... 6
WCDMA NE Classification ................................................................................ 6
Network Load Monitoring Indicators .................................................................. 7
Key Indicators ................................................................................................... 7
Average Utilization of Non-HSDPA Code Resource.......................................... 7
Average Utilization of Non-HSDPA Carrier Transmit Power.............................. 9
Uplink Noise Rise ........................................................................................... 10
Average Throughput of HSDPA Cell ............................................................... 11
Average Throughput of HSDPA Single User ................................................... 11
3
3.1
3.2
High-Load Network Optimization ................................................................ 13
Network Load Optimization Stages ................................................................. 13
Network Load Optimization Process ............................................................... 14
4
4.1
4.1.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
High-Load Network Expansion .................................................................... 16
Expansion Process ......................................................................................... 16
Expansion Analysis Process ........................................................................... 16
Expansion Criteria and Methods ..................................................................... 17
Cell Expansion................................................................................................ 17
Node B-CE Expansion .................................................................................... 26
IUB Transmission Expansion .......................................................................... 30
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 4-4 Cell Expansion Implementation Rules ................................................................ 29
Table 4-5 Iub Transmission Expansion Thresholds ............................................................ 31
Table 4-6 Cell Expansion Implementation Rules ................................................................ 32
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
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UMTS Network Load Monitoring and Expansion Guide
1
Overview
1.1
Background
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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.
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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.
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Figure 1-1
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High-Load Network Monitoring and Optimization
Horizontal: RNC, NodeB, and cell
Vertical
1. High-load network monitoring
User perception evaluation
Network resource evaluation
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.
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Figure 1-2
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High-Load Network Monitoring Process
Yes
Cell-level monitoring,
analysis, and alarm
High-load network
performance
monitoring and
evaluation
NodeB-level
monitoring, analysis,
and alarm
RNC-level monitoring,
analysis, and alarm
Perform
optimization to
solve the problem
of high load
No
Meet the cell capacity
expansion requirements
or not?
Yes
Cell expansion
Add carriers or power
amplifiers
Meet the NodeB capacity
expansion requirements
or not?
Yes
NodeB expansion
Add BPC boards or
transmission resources
Meet the RNC capacity
expansion requirements
or not?
Yes
RNC expansion
Software: Add licenses
Hardware: Add RUB or
RCB boards
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.
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Figure 1-3
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High-Load Network Optimization Process
High-load NE
Cell-level NEs involve false load rises and
real load rises.
Vertical
RF optimization
Neighbor optimization, only for cell-level NEs
RF neighbor optimization
Primary pilot optimization
Reduce the soft handover ratio
Reduce soft handoff overheads
Parameter optimization
Congestion control
Load balancing
DRBC
Power control and HSPA
paremters
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.
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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).
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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:
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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
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E-AGCH
256
1
E-RGCH
128
1
CPICH
256
1
PCCPCH
256
1
SCCPCH
64
1
PICH
256
1
AICH
256
1
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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
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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
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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
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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
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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
Horizontal: RNC, NodeB, and cell
Vertical
1. High-load network monitoring
User perception evaluation
Network resource evaluation
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
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3.2
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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.
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Figure 3-2
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High-Load Network Optimization Process
High-load NE
Cell-level NEs involve false load rises and
real load rises.
Vertical
RF optimization
Neighbor optimization, only for cell-level NEs
RF neighbor optimization
Primary pilot optimization
Reduce the soft handover ratio
Reduce soft handoff overheads
Parameter optimization
Congestion control
Load balancing
DRBC
Power control and HSPA
paremters
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4
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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.
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Figure 4-1
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Expansion Analysis Process
Yes
Cell-level monitoring,
analysis, and alarm
High-load network
performance
monitoring and
evaluation
NodeB-level
monitoring, analysis,
and alarm
Perform
optimization to
solve the problem
of high load
RNC-level monitoring,
analysis, and alarm
No
Meet the cell capacity
expansion requirements
or not?
Yes
Cell expansion
Add carriers or power
amplifiers
Meet the NodeB capacity
expansion requirements
or not?
Yes
NodeB expansion
Add BPC boards or
transmission resources
Meet the RNC capacity
expansion requirements
or not?
Yes
RNC expansion
Software: Add licenses
Hardware: Add RUB or
RCB boards
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.
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4.2.1.1
Internal Use Only▲
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
To evaluate user perception:
Average packet user-perceived rate;
Uu interface congestion conditions
No
Low transmission
rate and
congestion
Yes
Low resource utilization rates
Resource utilization
evaluation: code resources
and power resources
To evaluate network resources:
Utilization rates of UL and DL power
resources;
Utilization rate of code resources
High resource utilization rates
False load rise
No
Real load rise
Optimization
High-load decision
Yes
Expansion
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
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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
Indicator Name
No.
Alarm
Expansion
Threshold
Threshold
≤1 Mbps
≤512 Kbps
Expansion Method
Average
SPI1
Throughput of
HSDPA Single
HSPA+/Multi-carrier/add
User
NodeB
HSDPA cell
SPI2
average
≥100 MB
≥150 MB
≥60%
≥70%
≥60%
≥70%
≥6 dB
≥8 dB
throughput
Non-HSDPA code
SPI4
resource average
Multi-carrier/add NodeB
occupancy
Average
utilization of
SPI5
non-HSDPA
carrier transmit
Expand power
amplifier/add NodeB
power
SPI6
Uplink noise rise
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Admission
SPI8
rejection
Set to be a
proportion due to
fixed
limited downlink
value: 1
≥2%
Multi-carrier/add NodeB
code resources
Admission
SPI9
rejection
Set to be a
proportion duo to
fixed
limited downlink
value: 1
≥2%
Expand power
amplifier/add NodeB
power TCP
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.
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Figure 4-3
Internal Use Only▲
Combination Chart of Cell Expansion Decision Formula
High-load cell decision
User perception evaluation
SPI1 × SPI2 = 1
The cell has a heavy PS
service load and a low userperceived 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.
Network resource evaluation
SPI × SPI2 = 1
SPI4 × SPI8 + SPI5 ×
SPI9 + SPI6 × (SPI4 +
SPI5) > 1
Yes
Yes
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 highload cell.
The cell has a high resource
utilization rate and a high nonHSDPA service load; user
perception about access is bad.
Hence this cell is a high-load
cell.
No
False load rise
Real load rise
Optimization
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.
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3.
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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
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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
4.2.1.3.2
Relationship Between the Code Resource Utilization and Traffic
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.
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Figure 4-5
Internal Use Only▲
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
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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
Monitoring Mode 1
Mode
Monitoring
Object
Monitoring
Granularity
Monitoring Mode 2
Cell of the whole network
Cell of the whole network
Hour
Hour
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A week (7 × N: N refers to the fixed
Monitoring
Cycle
A week (7 × 24)
busy hours of each day, and the
busy hour is set according to the
existing network state.)
Utilization alarm threshold:
If in 1 week, S_cell > 0, N ≥ 10,
perform the monitoring
Alarm
optimization and expansion
Monitoring
assessment.
Trigger
Utilization expansion threshold:
Condition
If in 1 week, S_cell > 0, N ≥ 10,
add to the cell list of monitoring
optimization and expansion
assessment.
Expansion
Trigger
Condition
4.2.2
Utilization alarm threshold:
If in 1 week, S_cell > 0, N ≥ 3,
perform the monitoring optimization
and expansion assessment.
Utilization expansion threshold:
If in 1 week, S_cell > 0, N ≥ 3, add
to the cell list of monitoring
optimization and expansion
assessment.
Utilization expansion threshold:
Utilization expansion threshold:
Suppose Sn is the expansion
Suppose Sn is the expansion index,
index, Sn = S_cell_1 + S_cell_2
Sn = S_cell_1 + S_cell_2
+ ……S_cell_n (n = 7 × 24).
+ ……S_cell_n (n = 7 × 24).
When S ≥ 10, expand the cell.
When S ≥ 3, expand the cell.
Actually, the formula means, Sn
Actually, the formula means, Sn is
is the sum of S_cell meeting the
the sum of S_cell meeting the
criteria (S_cell > 0).
criteria (S_cell > 0).
Greater Sn indicates greater cell
Greater Sn indicates greater cell
expansion demand.
expansion demand.
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.
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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
Indicator Name
No.
SPI11
Average utilization of
uplink NodeB CE resource
Alarm
Expansion
Expansion
Threshold
Threshold
Method
60%
70%
BPC board
Average utilization of
SPI12
downlink NodeB CE
60%
70%
80%
90%
80%%
90%
resource
SPI13
Maximum utilization of
uplink NodeB CE resource
Maximum utilization of
SPI14
downlink NodeB CE
resource
SPI15
SPI16
Admission rejection rate of
uplink CE
Admission rejection rate of
downlink CE
Expand the
Set as a
fixed
≥2%
value: 1
Set as a
fixed
≥2%
value: 1
Expand the
BPC board
Expand the
BPC board
Expand the
BPC board
Expand the
BPC board
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
Formula description:
1.
S_nodeb_CE is the Node B CE expansion index.
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2.
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(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
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Figure 4-7
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Maximum Utilization Rates of Uplink and Downlink NodeB CE Resources in
Shapingba, Chongqing, China
4.2.2.3
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 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.
Table 4-4
Cell Expansion Implementation Rules
Monitoring
Monitoring Mode 1
Mode
Monitoring
Object
Monitoring
Granularity
Monitoring Mode 2
Cell of the whole network
Cell of the whole network
Hour
Hour
A week (7 × N: N refers to the fixed
Monitoring
Cycle
A week (7 × 24)
busy hours of each day, and the
busy hour is set according to the
existing network state.)
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Monitoring
Monitoring Mode 1
Mode
Utilization alarm threshold:
If in 1 week, S_nodeb_CE > 0, N
≥ 10, perform monitoring
Alarm
optimization and expansion
Monitoring
assessment.
Trigger
Utilization expansion threshold:
Condition
If in 1 week, S_nodeb_CE > 0, N
≥ 10, add to the NodeB list of
monitoring optimization and
expansion assessment.
Utilization expansion threshold:
Suppose Sn is the expansion
index, Sn = S_nodeb_CE_1 +
S_nodeb_CE_2
+ …S_nodeb_CE_n (n = 7 × 24).
Expansion
Trigger
Condition
When S ≥ 10, expand the cell.
Actually, the formula means, Sn
is the sum of S_nodeb_CE
meeting the criteria
(S_nodeb_CE > 0).
Greater Sn indicates greater cell
expansion demand.
4.2.3
Internal Use Only▲
Monitoring Mode 2
Utilization alarm threshold:
If in 1 week, S_nodeb_CE > 0, N ≥
3, perform monitoring optimization
and expansion assessment.
Utilization expansion threshold:
If in 1 week, S_nodeb_CE > 0, N ≥
3, add the NodeB list of monitoring
optimization and expansion
assessment.
Utilization expansion threshold:
Suppose Sn is the expansion index,
Sn = S_nodeb_CE_1 +
S_nodeb_CE_2
+ …S_nodeb_CE_n (n = 7 × 24).
When S ≥ 3, expand the cell.
Actually, the formula means, Sn is
the sum of S_nodeb_CE meeting
the criteria (S_nodeb_CE > 0).
Greater Sn indicates greater cell
expansion demand.
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
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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
Indicator Name
No.
Alarm
Expansion
Expansion
Threshold
Threshold
Method
80%
90%
Maximum forward
SPI17
SPI18
accepted bandwidth
proportion of IP
Expand the
Maximum backward
transmission.
accepted bandwidth
80%
90%
60%
70%
60%
70%
80%
90%
80%
90%
60%
70%
60%
70%
proportion of IP
SPI19
Average forward accepted
bandwidth proportion of IP
Average backward
SPI20
accepted bandwidth
proportion of IP
Maximum forward
SPI21
accepted bandwidth
proportion of ATM
Maximum backward
SPI22
accepted bandwidth
proportion of ATM
Average forward accepted
SPI23
bandwidth proportion of
ATM
Average backward
SPI24
accepted bandwidth
proportion of ATM
Expand the
transmission.
Expand the
transmission.
Expand the
transmission.
Expand the
transmission.
Expand the
transmission.
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:
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S_trans = SPI17 + SPI18 + SPI19 + SPI20 + SPI21 + SPI22 + SPI23 + SPI24
Formula description:
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.
4.2.3.3
Expansion Implementation Rules
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.
Table 4-6
Cell Expansion Implementation Rules
Monitoring
Monitoring Mode 1
Mode
Monitoring
Object
Monitoring
Granularity
Monitoring Mode 2
Cell of the whole network
Cell of the whole network
Hour
Hour
A week (7 × N: N refers to the fixed
Monitoring
Cycle
A week (7 × 24)
busy hours of each day, and the
busy hour is set according to the
existing network state.)
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Monitoring
Monitoring Mode 1
Mode
Utilization alarm threshold:
If in 1 week, S_trans > 0, N ≥ 10,
perform the monitoring
Alarm
optimization and expansion
Monitoring
assessment.
Trigger
Utilization expansion threshold:
Condition
If in 1 week, S_trans > 0, N ≥ 10,
add to the NodeB list of
monitoring optimization and
expansion assessment.
Utilization expansion threshold:
Suppose the expansion index is
Sn,
Sn = S_trans_1 +
S_trans_2 + ……S_trans_n (n =
Expansion
7 × 24 hrs).
Trigger
When S ≥ 10, expand the cell.
Condition
Actually, the formula means, Sn
is the sum of S_trans meeting the
criteria (S_trans > 0).
Greater Sn indicates greater cell
expansion demand.
4.2.4
Internal Use Only▲
Monitoring Mode 2
Utilization alarm threshold:
If in 1 week, S_trans > 0, N ≥ 3,
perform the monitoring optimization
and expansion assessment.
Utilization expansion threshold:
If in 1 week, S_trans > 0, N ≥ 3, add
to the NodeB list of monitoring
optimization and expansion
assessment.
Utilization expansion threshold:
Suppose the expansion index is Sn,
Sn = S_trans_1 + S_trans_2
+ ……S_trans_n (n = 7 × 24 hrs).
When S ≥ 3, expand the cell.
Actually, the formula means, Sn is
the sum of S_trans meeting the
criteria (S_trans > 0).
Greater Sn indicates greater cell
expansion demand.
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.
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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
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UMTS Network Load Monitoring and Expansion Guide
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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
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UMTS Network Load Monitoring and Expansion Guide
iii.

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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
Indicator Name
No.
SPI31
SPI32
Average utilization of
RUP CE resources
Maximum utilization of
RUP CE resources
Monitoring
Expansion
Expansion
Threshold
Threshold
Method
60%
70%
80%
90%
SPI33
RCP CPU average load
60%
70%
SPI34
RCP CPU peak load
80%
90%
NodeB quantity
140/pair of RCB
Cell quantity
420/pair of RCB
Expand the
RUB board.
Expand the
RUB board.
Expand the
RCB board.
Expand the
RCB board.
Expand the
RCB board.
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.
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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)
Formula description:
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
Related Monitoring
Name
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
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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.
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Table 4-9
Observation Indicators of RNC Hardware Expansion
Indicator Name
Average bandwidth utilization in the
ATM interface board transmit direction
Average bandwidth utilization in the
ATM interface board receiving direction
Average bandwidth utilization in the IP
interface board transmit direction
Average bandwidth utilization in the IP
interface board transmit direction
Maximum bandwidth utilization in the
IP interface board transmit direction
Maximum bandwidth utilization in the
IP interface board transmit direction
4.2.4.1.2
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Monitoring
Expansion
Expansion
Threshold
Threshold
Method
Expand the
70%
80%
ATM interface
board
Expand the
70%
80%
ATM interface
board
70%
80%
70%
80%
70%
90%
50%
90%
Expand the IP
interface board
Expand the IP
interface board
Expand the IP
interface board
Expand the IP
interface board
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:
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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
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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.
4.2.4.3
Expansion Implementation Rules
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
Monitoring
Object
Monitoring
Granularity
Monitoring
Cycle
Monitoring
Trigger
Condition
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Implementation Rule 2
RNC of the whole network
RNC of the whole network
Hour
Hour
A week (7 × 24)
A week (busy hours of each day)
If in 1 week, S_hard ≥ 1, N ≥ 10,
If in 1 week, S_hard ≥ 1, N ≥ 3,
perform the monitoring
perform the monitoring
optimization and expansion
optimization and expansion
assessment.
assessment.
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UMTS Network Load Monitoring and Expansion Guide
Expansion
Trigger
Condition
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If in 1 week, S_hard ≥ 1, N ≥ 10,
If in 1 week, S_hard ≥ 1, N ≥ 3,
perform the capacity expansion.
perform the capacity expansion.
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