Hệ thống truyền thông di động WCDMA P5 docx

Customer interface management processService configuration Service planning/ development Service quality management Rating and discounting Service problem resolution Network provisioning

Operation System

Masafumi Onuki, Nobutaka Nakamura, Haruo Mizumoto, Takeshi

Yamashita, Kazuhiko Hara and Kazuaki Terunuma

5.1 Overview

As an extremely large number of network equipment are installed by telecom carriers tobuild a mobile communications network, there is a significant number of NEs that affectcommunication services because of faults It is important to monitor network equipments

24 hours a day to ensure the stable provision of high-quality services Operation AndMaintenance (OAM) by the Operation System (OpS) is therefore essential in communi-cation networks nowadays

Hitherto, mobile carriers had to resort to labor-intensive means to maintain the servicequality whenever the network was expanded In the future, it will be necessary to build

an operation framework that can take swift action based on strategic information agement and assure maximum quality with minimal personnel This chapter reviews thefunctions and the mechanism of OpS, which is expected to become increasingly impor-tant with the introduction of International Mobile Telecommunications-2000 (IMT-2000),with reference to actual system construction

man-5.1.1 Positioning of OpS

The layers depicted in Figure 5.1 show the OAM functions based on the communication Management Network (TMN) model generally specified by the ITU-Telecommunication Standardization Sector (ITU-T) [1] The bottom layer representsNetwork Element (NE), whereas the element management layer positioned above thatexecutes NE management on an individual basis The NW management layer abovethe element management layer realizes functions to manage the entire network, whichconsists of multiple NEs The service management layer above the NW managementlayer is positioned to support functions for managing services provided over the network

Tele-On the basis of such a TMN model, the 3rd Generation Partnership Project (3GPP),which is a standardization body for the next-generation mobile communications system,defines the standard interface between the Network Manager (NM) and the ElementManager (EM), and between EM and NE as shown in Figure 5.2 The definition of the

Copyright  2002 John Wiley & Sons, Ltd.

ISBN: 0-470-84761-1

Network element layer

Element management layer

Network management layer

Service management layer

Figure 5.1 TMN layer model under ITU-T

RNC

RNC element manager

Node B element manager

Node B

Figure 5.2 Management layer model under 3GPP

element and manager functions and the interfaces between them enable the interconnection

of NEs from various vendors and EMs and coordination with NM

The management functions required by these managers are defined in terms of OpenSystems Interconnection (OSI) management [2] The definition includes fault manage-ment, configuration management, accounting management, performance management andsecurity management 3GPP defines the management process groups using the Tele-com Operation Map (TOM) of the Tele Management Forum (TM Forum) that specifiesthese functions in further detail [3] By using the management processes referred to inFigure 5.3, interoperability is assured between network operators and service providers,including the exchange of fault information and billing information In addition, the distri-bution of software that implements management process functions can cut the investmentcosts incurred at the time of system development

Customer interface management process

Service configuration

Service

planning/

development

Service quality management

Rating and discounting

Service problem resolution

Network provisioning

Network

planning/

development

Network data management

Network maintenance

& restoration

Network inventory management Service development and operations processes

Network and systems management processes

Order handling

Problem handling

Customer QoS management

Physical network and information technology Element management, technology related

Service management

Network management

Figure 5.3 Telecom operation map of TM forum

For the provision of IMT-2000 services, the following enhancements were made tothe OAM technologies accumulated thus far in addition to the configuration of processgroups mentioned in the preceding text [4, 7, 8]:

1 the identification of network status and the enhancement of network control focusing

on improved service quality;

2 the establishment of a flow-through data stream used in construction, maintenance,quality management and planning tasks and

3 centralized OAM management of different Personal Digital Cellular (PDC) networksand IMT-2000 networks

(i) NE Monitoring System

NE monitoring systems are installed to monitor radio equipment, switching equipment,transmission equipment and other network facilities Each NE monitoring system managesthe status of NE faults, performance, files and the status of system data updating and

Network element management

Network Element (NE):

Radio access network planning Radio access network design

Switching network planning Switching network design

Progress management Transmission network design

System data management configurationmanagement

Service quality monitoring

NW control

Major alarm aggregate

Traffic data warehouse

Radio access equipment NEM

Switching equipment NEM

Transmission equipment NEM

NW monitor

and control OPE

Backyard

Path management

HLR NEM

NW monitoring

Figure 5.4 IMT-2000 OpS architecture

(ii) Major Alarm Aggregate Server

The major alarm aggregate server collects and manages major alarms of all NEs viathe NE monitoring systems Major alarms from the server are notified to the backyardOPeration Equipment (OPE) that constitutes the control desk This arrangement enablesthe operator to identify the activation status of all NE major alarms at one backyard OPE

(iii) Call-Processing Alarm Server

The call-processing alarm server gathers and stores call release factors because of normal processing from the radio equipment and switches When semi-normal processingfrequently occurs, the call-processing alarm server informs the backyard OPE, the NW-monitoring OPE and the service front terminal

semi-Moreover, in response to the customer’s complaints about call abnormalities, the ator can check the status of the abnormalities with reference to the database of thecall-processing alarm server using the subscriber number as the key

oper-(iv) NE File Management System

This system manages the version of systems files of each NE and system data, andexecutes the remote updating of files in coordination with the NE monitoring system

To let the data flow through using system data, system data is updated on the order of(design system→ NE file management system → NE monitoring system → NE), andthe operation data of various OpS equipment (server/OPE) is created and updated on theorder of (NE file management system→ OpS configuration management system → NEmonitoring system/OPE)

(v) OpS Configuration Management System

This system appropriates NE files and system data from the system data managementserver, automatically creates the data required for the operation of various OpS equipment(server operation data and OPE screen display data), and downloads the data to the OpSequipment This makes it unnecessary for the operator to make new entries associatedwith the creation of data for various OpS equipment, and enables the updating of operationdata of OpS equipment in sync with the updating of the system data of NE itself

(vi) Backyard OPE

This is a control desk for carrying out maintenance tasks associated with the NE ment layer in general One OPE monitors and controls various NEs based on commonoperation

manage-5.1.2.2 NetWork (NW) Management Layer

NW Monitoring System

In coordination with the NE monitoring system and the NW control system, the NW itoring system gathers fault information and performance information (status of resourceusage) of radio equipment and switching equipment required for network control, as well

mon-as traffic data such mon-as circuit connection status and call loss state, and notifies the NWmonitor and control OPE

This enables the operator to simultaneously identify the service quality status in theentire network – from the access network up to the switching network – and the status of

NW components, that is, the network status

NW Control System

The NW control system gathers fault information and performance information on ing equipment, detects congestion and executes network control by ordering restrictioncontrol to the switching equipment and Radio Network Controller (RNC) as required.This enables prompt and accurate network control aimed at assuring service qualityand maximizing the utilization of networks

switch-Traffic Data Warehouse

The traffic data warehouse gathers traffic information of the radio equipment and theswitching equipment on a regular basis, via the NE monitoring system and the NW con-trol system The primary database, in which the data is stored, is designed for nonstandardforms, that is, the user can freely create the forms Parts of the data stored in the pri-mary database are automatically edited and processed at nighttime to suit standard formsrequired for periodic management, such as weekly reports, monthly reports and annualreports, and are stored in the secondary database

The quality management operator applies general-purpose On-Line Analytical ing (OLAP) tools to the network data stored in these databases to promptly analyzevarious data

Process-Path Management Server

The path management server receives the circuit order information of the transmissiondesign system, automatically opens the circuit and manages the transmission path con-figuration information It also detects faults in the path and informs the operator of suchfaults

NW Monitor and Control OPE

This is a control desk for accessing the NW monitoring system and the NW controlsystem, for the purpose of monitoring and controlling the network

5.1.2.3 Service Management Layer

Service Monitoring System

The service monitoring system provides the service front with network information that isuseful for identifying the service quality, including the call loss status and call-processingalarms identified by the NW monitoring system in the network management layer.This enables the service front to identify the network quality status at real time anddeal with customers accordingly

Planning System

The planning system receives traffic information from the traffic data warehouse, assessesthe traffic records, forecasts the traffic and develops facility plans

Design System

On the basis of the planning information from the planning system, the design system is

in charge of the logical NW design such as the allocation of NEs and physical designs

including path design and capacity design It also creates system data based on the designinformation.

As described in the preceding text, the IMT-2000 OpS is adapted to large-scale tions by integrating various servers and systems The following sections explain networkmonitoring, network control, NE monitoring and NE management, which have been espe-cially reinforced in the IMT-2000 OpS

opera-5.2 Network Monitoring

NTT DoCoMo’s existing NW monitoring OpS monitors the switching network by culating the call volume and the connection rate between switching equipment throughcommon channel signal monitoring In other words, it is a monitoring system specializing

cal-in switchcal-ing networks

NTT DoCoMo has developed a NW monitoring system with the following two

objec-tives in mind in order to identify the network status and execute network control focusing

on the improvement of service quality, which is one of NTT DoCoMo’s basic OpS

infor-5.2.1 Configuration of Network Monitoring Functions

Figure 5.5 illustrates an example of the configuration of NW monitoring functions.The NW monitoring system monitors the traffic status and the equipment status of thenetwork as a whole, from the access network to the switching network, on the basis ofcoordination between the NW-monitoring Core Network (CN) server, the NW-monitoringRadio-Access Network (RAN) server and the NW-monitoring fault server, as shown inFigure 5.5

NW-Monitoring CN Server

NW-monitoring CN server gathers information on the status of resource utilization andthe status of link connection from the switching NE in the switching equipment, inaddition to various traffic data relating to call loss via the NW control system Thegathered information is subject to threshold decision and notified to the NW monitor andcontrol OPE

NW-Monitoring RAN Server

NW-monitoring RAN server is informed of the status of resource usage from the access

NE of the Base Station (BS) and RNC, and various traffic data relating to call loss that

NW monitor and control OPE

Call-processing alarm server

Switching equipment

Switching equipment RNC

Transmission channel

Figure 5.5 Configuration of network monitoring functions (example)

exceed the threshold via radio Network Element Management (NEM) Apart from thetraffic data, information of abnormal call processing in excess of the threshold in theradio equipment and the switching equipment are notified via the call-processing alarmsystem The information notified to these servers is passed on to the NW monitor andcontrol OPE at real time

NW-Monitoring Fault Server

NW-monitoring fault server is informed of significant faults in BS, switching equipmentand transmission path via the major alarm aggregate server The information notified tothese servers is passed on to the NW monitor and control OPE at real time

5.2.2 Characteristics of Network Monitoring

Figure 5.6 illustrates how NW monitoring works The following is the description of thecharacteristics of NW monitoring

(i) Total Monitoring: from Access Network to Switching Network

The operator monitors the service quality status of the nationwide network from RANthrough CN The operator also checks the level of impact on services in the event ofaccess network failure by displaying the affected area in the map

(ii) End-to-End Call Loss Monitoring

CN monitors the call loss status from the call-originating switching equipment to thecall-terminating switching equipment, end-to-end This makes it possible to monitor theconnection quality and determine, for example, where it is difficult to establish calls

Sapporo

RAN quality monitoring

Identity overall status of RAN∼CN

Figure 5.6 NW monitoring image

(iii) NE Performance Information and Fault Information are Displayed to Identify the Causes of NW Failure According to RAN Strata and CN Strata, Other than Traffic Information Relating to Call Loss and Connection Status

The operator executes NW control with reference to such detailed information Theoperator can also identify the effects of control in a quantitative manner by checking thecall loss status

Table 5.1 shows the monitored items in the monitoring layer referred to in Figure 5.6.Information to be monitored by operators engaged in network control mainly con-cerns the items monitored in the service-monitoring layer and the NW-monitoring layer.Information to be monitored by service staff at the service front is primarily based onthe items monitored in the service-monitoring layer Information to be monitored byoperators involved in element maintenance is mainly based on items monitored in theNE-monitoring layer

Using the information handled in these monitoring layers, NW monitoring and NEmonitoring tasks are coordinated with each other so as to monitor, analyze and takemeasures with respect to NW and NE in a comprehensive manner

Figure 5.7 shows the operation flow of NW monitoring and NE monitoring

Table 5.1 Monitoring layers and monitoring items

Monitoring layer Objective and

overview of monitoring

Monitoring item Monitoring

– RAN connection quality items:

traffic CH busy rate, PCH busy rate, call origination/termination completion rate etc.

– CN connection quality items:

blocking probability, connection completion rate – Call-processing alarm

Service front network control

Network-monitoring

layer

Identification of NW status focusing on network congestion and restriction control

– NE resource utilization status – NE restriction status

– Major faults in NE – Connection status, call loss and number of completed calls between NE and NE.

Network control

NE monitoring

layer

Identification of element status focusing on maintenance of individual NEs

– Major and minor faults in NE – Operation status of NE (system, resources and file updating)

Element maintenance

Note: CH: Call Hold; PCH: Paging Channel

Traffic

MJ alarm, NE status

Flow of NW monitor & control

Flow of NE monitor & control

Legends

Monitoring of poor network quality

Network

Identification of causes of NW faults

(Call loss, causes of poor connection and

causes of congestion)

Recovery of service quality

→NW control Bypass control, restriction control

End-to-end call loss rate Zone call loss rate, Connection rate Equipment congestion

NW monitor and control tasks

Switching equipment BS

Request of solutions to faults

Identification of causes of faults

Monitoring of faults in NE

Figure 5.7 Operation flow of NW monitoring and NE monitoring

5.2.3 Building a Network Monitoring System

Monitoring the network built by NTT DoCoMo involves the identification of causes inthe event of faults in NEs nationwide, NW congestion, restriction display and changes inthe call connection rate and call loss rate To monitor the nationwide network, the screenshown in Figure 5.8 is used

In the event of faults and congestion, the CN strata screen shown in Figure 5.9 isdisplayed to clarify the source of the event The important task here is to be able toconstantly identify the status real time With the displayed screen, it is easy to identifythe status of NE and NW with reference to icon types and different colors Also, thedisplay of strata makes it easier to identify the impact of the event on other switchingequipment and work out the necessary solutions

In particular, for the identification of the connection status, the usage status of the setbandwidth in VP (Virtual Path) units of the Asynchronous Transfer Mode (ATM) linkset up between switching equipment is displayed in terms of the connection rate, so that

Figure 5.8 Example of nationwide network monitoring

Figure 5.9 Example of CN strata display and VP bandwidth display

Figure 5.10 Example of RAN strata display

the traffic status of the switching equipment can always be identified The impact of theevent is therefore visually discernable and the status can be confirmed upon recovery bythe display of the connection rate Also, the connection rate in zones between specificswitching equipment can be displayed, which offers a means to pin down the causes ofthe deteriorating connection rate

Figure 5.10 shows the RAN strata screen, which displays the NEs and each sector ofthe BS It is possible to switch from this screen to the RAN area display illustrated inFigure 5.11, and the service status can be visually represented in combination with thegeographical location where the service is actually provided

Services can always be provided in a stable manner as faults in NEs and the status of

NW congestion and restrictions can always be identified using the NW monitoring screen

5.3 Network Control

Normally, elements of the communication network are designed in accordance with trafficvolume If a large volume of traffic in excess of the element capacity flows in, thenetwork would suffer from congestion and stop functioning The congestion patternsand the automatic control algorithms in the IMT-2000 network is summarized below onthe basis of past records relating to the congestion patterns and automatic Congestion-control algorithms in PDC and Personal Digital Cellular-Packet (PDC-P) networks ofNTT DoCoMo

Figure 5.11 Example of RAN area display

Congestion Patterns

• Congestion caused by disasters and so on;

• Congestion due to many calls terminating at a particular phone number (fixed/mobilephone);

• Congestion due to traffic generated by events, for example, congratulation calls;

• Spot congestion at concerts and cherry-blossom viewing parties;

• Congestion caused by i-mode mail and large-volume Packet-Switched (PS)

communi-cations and

• Congestion caused by wide bandwidth communications, for example, audiovisual munications (assuming IMT services)