Hệ thống truyền thông di động WCDMA P5 docx

5 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 to build a mobile communications network, there is a significant number of NEs that affect communication services because of faults. I t is important to monitor network equipments 24 hours a day to ensure the stable provision of high-quality services. Operation And Maintenance (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 service quality 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 man- agement and assure maximum quality with minimal personnel. This chapter reviews the functions 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. 5.1.1 Positioning of OpS The layers depicted in Figure 5.1 show the OAM functions based on the Tele- communication Management Network (TMN) model generally specified by the ITU- Telecommunication Standardization Sector (ITU-T) [1]. The bottom layer represents Network Element (NE), whereas the element management layer positioned above that executes NE management on an individual basis. The NW management layer above the element management layer realizes functions to manage the entire network, which consists of multiple NEs. The service management layer above the NW management layer is positioned to support functions for managing services provided over the network. 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 Element Manager (EM), and between EM and NE as shown in Figure 5.2. The definition of the W-CDMA: Mobile Communications System. Edited by Keiji Tachikawa Copyright  2002 John Wiley & Sons, Ltd. ISBN: 0-470-84761-1 278 W-CDMA Mobile Communications System 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 Iub Network manager Itf-N Option to switch O&M traffic via RNC Itf-B Itf-R Element management Network management 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 Open Systems Interconnection (OSI) management [2]. The definition includes fault manage- ment, configuration management, accounting management, performance management and security management. 3GPP defines the management process groups using the Tele- com Operation Map (TOM) of the Tele Management Forum (TM Forum) that specifies these functions in further detail [3]. By using the management processes referred to in Figure 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 investment costs incurred at the time of system development. Operation System 279 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 Invoicing/ collections Customer care processes Sales Customer Information systems management processes Physical network and information technology Element management, technology related Service management Network management Figure 5.3 Telecom operation map of TM forum 280 W-CDMA Mobile Communications System For the provision of IMT-2000 services, the following enhancements were made to the OAM technologies accumulated thus far in addition to the configuration of process groups 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) networks and IMT-2000 networks. 5.1.2 System Configuration Figure 5.4 illustrates the architecture of IMT-2000 OpS according to TMN layers. 5.1.2.1 NE Management Layer The NE management layer, which is in charge of OAM of each NE, consists of the following servers. (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 manages the status of NE faults, performance, files and the status of system data updating and so on. Also, the NE monitoring system informs the major alarm aggregate server of the most urgent alarms (major alarms). OSS Service management layer NW management layer NE management layer NE NE Management (NEM): Network element management Network Element (NE): Network Element BS BS RNC RNC Switching equipment Switching equipment HLR Transmission Service front terminal Setup terminals Quality analysis terminal Radio access network planning Radio access network design Switching network planning Switching network design Progress management Transmission network design System data management configuration management 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 OPE Call processing alarm aggregate Path management HLR NEM NW monitoring Figure 5.4 IMT-2000 OpS architecture Operation System 281 (ii) Major Alarm Aggregate Server The major alarm aggregate server collects a nd manages major alarms of all NEs via the NE monitoring systems. Major alarms from the server are notified to the backyard OPeration Equipment (OPE) that constitutes the control desk. This arrangement enables the 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 semi- normal processing from the radio equipment and switches. When semi-normal processing frequently occurs, the call-processing alarm server informs the backyard OPE, the NW- monitoring OPE and the service front terminal. Moreover, in response to the customer’s complaints about call abnormalities, the oper- ator can check the status of the abnormalities with reference to the database of the call-processing alarm server using the subscriber number as the key. (iv) NE File Management System This system manages the version of systems files of each NE and system data, and executes 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), and the operation data of various OpS equipment (server/OPE) is created and updated on the order of (NE file management system → OpS configuration management system → NE monitoring system/OPE). (v) OpS Configuration Management System This system appropriates NE files and system data from the system data management server, 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 OpS equipment. This makes it unnecessary for the operator to make new entries associated with the creation of data for various OpS equipment, and enables the updating of operation data 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 manage- ment layer in general. One OPE monitors and controls various NEs based on common operation. 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 mon- itoring system gathers fault information and performance information (status of resource usage) of radio equipment and switching equipment required for network control, as well as traffic data such as circuit connection status and call loss state, and notifies the NW monitor and control OPE. 282 W-CDMA Mobile Communications System This enables the operator to simultaneously identify the service quality status in the entire 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 switch- ing equipment, detects congestion and executes network control by ordering restriction control to the switching equipment and Radio Network Controller (RNC) as required. This enables prompt and accurate network control aimed at assuring service quality and maximizing the utilization of networks. Traffic Data Warehouse The traffic data warehouse gathers traffic information of the radio equipment and the switching 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 nonstandard forms, 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 forms required for periodic management, such as weekly reports, monthly reports and annual reports, and are stored in the secondary database. The quality management operator applies general-purpose On-Line Analytical Process- ing (OLAP) tools to the network data stored in these databases to promptly analyze various data. Path Management Server The path management server receives the circuit order information of the transmission design 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 such faults. NW Monitor and Control OPE This is a control desk for accessing the NW monitoring system and the NW control system, 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 is useful for identifying the service quality, including the call loss status and call-processing alarms 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 and deal with customers accordingly. Planning System The planning system receives traffic information from the traffic data warehouse, assesses the 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 Operation System 283 including path design and capacity design. It also creates system data based on the design information. As described in the preceding text, the IMT- 2000 OpS is adapted to large-scale opera- tions by integrating various servers and systems. The following sections explain network monitoring, network control, NE monitoring and NE management, which have been espe- cially reinforced in the IMT-2000 OpS. 5.2 Network Monitoring NTT DoCoMo’s existing NW monitoring OpS monitors the switching network by cal- culating the call volume and the connection rate between switching equipment through common channel signal monitoring. In other words, it is a monitoring system specializing in switching 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 concepts [6]. 1. Monitor the traffic status of the entire network, from the access network to the switching network and 2. Monitor the connection status between switches, and monitor call losses. Execute monitoring in a manner that complies with the customers’ perception. The NW monitoring OpS focuses especially on fault information and performance infor- mation (status of resource utilization) of the radio equipment and switching equipment required for network control and on traffic data including link connection status and call loss status. 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 the network as a whole, from the access network to the switching network, on the basis of coordination between the NW-monitoring Core Network (CN) server, the NW-monitoring Radio-Access Network (RAN) server and the NW-monitoring fault server, as shown in Figure 5.5. NW-Monitoring CN Server NW-monitoring CN server gathers information on the status of resource utilization and the status of link connection from the switching NE in the switching equipment, in addition to various traffic data relating to call loss via the NW control system. The gathered information is subject to threshold decision and notified to the NW monitor and control 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 c all loss that 284 W-CDMA Mobile Communications System Traffic MJ alarm Call processing alarm Control Control NE management layer NEM:NE management server Network management layer NE NW fault-monitoring server (MJ alarm managed by network) CN traffic CN traffic RAN traffic MJ alarm Radio NEM Switching NEM SCPNEM Transmission NEM MJ alarm Call processing alarm RAN traffic BS NMSCP NW-monitoring RAN server (RAN traffic monitoring) NW control server Major alarm aggregate server NW-monitoring CN server (CN traffic monitoring) 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 the traffic data, information of abnormal call processing in excess of the threshold in the radio equipment and the switching equipment are notified via the call-processing alarm system. The information notified to these servers is passed on to the NW monitor and control OPE at real time. NW-Monitoring Fault Server NW-monitoring fault server is informed of significant faults in BS, switching equipment and transmission path via the major alarm aggregate server. The information notified to these 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 the characteristics of NW monitoring. (i) Total Monitoring: from Access Network to Switching Network The operator monitors the service quality status of the nationwide network from RAN through CN. The operator a lso checks the level of impact on services in the event of access 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 the call-terminating switching equipment, end-to-end. This makes it possible to monitor the connection quality and determine, for example, where it is difficult to establish calls. Operation System 285 Osaka Sapporo RAN quality monitoring (impact on area) (End-to-end call loss between originating LS and terminating LS) Identity overall status of RAN∼CN Service monitoring NW monitoring NE monitoring (Each NE) Monitoring of call loss in zones and connection status Monitoring of NE performance and faults NW monitoring CN Mapping of individual faults and performance information on NW configuration TS TS LS LS LS LS LS NW monitoring RAN NW monitoring OPE NW monitoring OPE Fault Poorer performance Monitoring by traffic BS Switching equipment RNC Transmission CN quality monitoring 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 c ontrol with reference to such detailed information. The operator can also identify the effects of control in a quantitative manner by checking the call 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 on the items monitored in the service-monitoring layer. Information to be monitored by operators involved in element maintenance is mainly based on items monitored in the NE-monitoring layer. Using the information handled in these monitoring layers, NW monitoring and NE monitoring tasks are coordinated with each other so as to monitor, analyze and take measures with respect to NW and NE in a comprehensive manner. Figure 5.7 shows the operation flow of NW monitoring and NE monitoring. 286 W-CDMA Mobile Communications System Table 5.1 Monitoring layers and monitoring items Monitoring layer Objective and overview of monitoring Monitoring item Monitoring user Service- monitoring layer Monitoring focusing on identification of service quality status – 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 o f 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 Individual NE NE fault NE status Solutions to fix faults in element NE monitoring Element maintenance tasks Network monitoring NW status analysis NW status analysis Solutions Solutions Switching equipment 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 [...]... switching distriacquis• MMS monitoring and equipment bution ition control Operation OpS configuration management system data • Operation data managedistribution ment Operation AIN NEM • Operation data distribution data • AIN monitoring and control status management by distribution Radio station data OpS design terminal NE file management NE file management • NE data of radio access equipment Radio NEM... possible to distinguish the version applicable to each NE unit This helps prevent the selection of the wrong file Registration terminal File forwarding order OPE Registration NE file management system • Files other than station files e.g system files • NE • File • NE file management • File injection status management by unit status display forwarding order HLR File forwarding Aguisition File forwarding HLR... Information and Itemization The functions to gather information including traffic data should be standardized so that the maintenance staff would not have to worry about the differences in vendors Also, data processing should be made easier (3) Standardized Signal Interface Between NE and OpS The signal interface should be standardized for all NE types, so that all NEs can be accommodated in one NE... equipment is displayed in terms of the connection rate, so that Figure 5.8 Example of nationwide network monitoring 288 W-CDMA Mobile Communications System Figure 5.9 Example of CN strata display and VP bandwidth display Operation System 289 Figure 5.10 Example of RAN strata display the traffic status of the switching equipment can always be identified The impact of the event is therefore visually discernable... (example) 5.3.2 Coordination between Systems in Different Types of Networks NTT DoCoMo’s IMT network shares HLR with its PDC network, and is connected to the PDC network via a switching equipment in the gateway strata Because of such a system arrangement, network control is executed in coordination with the network monitor and control system of the PDC network It is also coordinated to distribute information... station data OpS design terminal NE file management NE file management • NE data of radio access equipment Radio NEM Operation • Monitoring and control of radio access data distribution equipment MMS File forwarding AIN File forwarding File forwarding RNC/MPE/BTS Manual entry of operation data Entry terminal • Operation data entry Other OpS equipment Definition of arrows: : Flow of NE files : Flow of... Transceiver Station (BTS), the RNC and the Multimedia Signal Processing Equipment (MPE), as discussed in Section 3.4.1 of Chapter 3 Each equipment is supplied by multiple vendors, and dozens of different types of NEs require operation As illustrated in Figure 5.17, the design philosophy varies between vendors even if the equipment is the same, resulting in a totally different equipment configuration Thus, in... monitoring conditions and the information gathered vary between each NE, it would be difficult to monitor the entire network, analyze the information and promptly deal with faults in a uniform manner At the worst, it would increase the number of OpS units and maintenance tasks For the network element operation of a multivendor radio-access system, NTT DoCoMo considered the following factors, including NE,... confirmed upon recovery by the display of the connection rate Also, the connection rate in zones between specific switching equipment can be displayed, which offers a means to pin down the causes of the deteriorating connection rate Figure 5.10 shows the RAN strata screen, which displays the NEs and each sector of the BS It is possible to switch from this screen to the RAN area display illustrated in Figure... operation absorbing differences among vendors 300 W-CDMA Mobile Communications System The function and the screen do not depend on the equipment vendor as far as functional blocks are concerned The status of equipment can be discerned and the impact on services can be identified commonly among vendors Figure 5.21 Example of monitoring screen (display common to functional units) Display of functional . 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. OAM management of different Personal Digital Cellular (PDC) networks and IMT-2000 networks. 5.1.2 System Configuration Figure 5.4 illustrates the architecture of IMT-2000 OpS according to TMN layers. 5.1.2.1. bandwidth display Operation System 289 Figure 5.10 Example of RAN strata display the traffic status of the switching equipment can always be identified. The impact of the event is therefore visually discernable