TMN Realization in GSM Networks

TMN and GSM were standardized approximately at the same time, so that there was a good opportunity to apply TMN principles and methods in a complete TMN system for network management in GSM from the beginning and from ground up. For this purpose, specific working groups were founded for the five TMN categories (Figure 10.1) as well as for architecture and protocol questions which were supposed to develop as much as possible of the TMN system and its services, while following the top-down methodology [13,14] recommended by the ITU-T. This objective could be pretty much achieved, only that the development methodology was complemented by a bottom-up approach which was rooted in the detailed knowledge about the network components being specified at the same time. The intent was to reach the objective of a complete standard earlier [43,57]. The five TMN categories are essentially realized for all of the GSM system; however, there are some limitations in failure, configuration, and security management. Failure and configuration management are specified only for the BSS; the reasons are that on one hand the databases (HLR, VLR) were assigned to accounting management, and on the other hand standardization efforts were to concentrate on GSM-specific areas. Concentration on GSM-specific areas thereby excluded failure and configuration management for the MSC, which from the management point of view is essentially a standard ISDN switching exchange. For the same reasons, security management is also limited to GSM-specific areas.

The resulting GSM TMN architecture is shown schematically in Figure 10.4. In GSM, the BSC and the MSC have a Q3 interface as network elements to the OS. Besides the BSS

Bss Interface Drawing
Figure 10.4: A simple TMN architecture of a GSM system (according to [57])
Tmn Architecture

M NAP Management Network Access Point Figure 10.5: Potential signalling interfaces in a GSM TMN

management, the BSC NE always contains a Mediation Function (MF) and a Qx interface to the NE supporting the BTS functionality.

An object-oriented information model of the network has been defined for the realization of the GSM TMN services. The model contains more than lOO Managed Object Classes (MOCs) with a total of about 5OO attributes. This includes the ITU-T standard objects as well as GSM-specific objects, which include the GSM network elements (BSS, HLR, VLR, MSC, AUC, EIR) on one hand, but also represent network and management resources (e.g. for SMS service realization or for file transfer between OS and NE) as managed objects. These objects usually contain a state space and attributes which can be checked or changed (request) as well as mechanisms for notification, which report the state or attribute changes. In addition, there are commands for creation or deletion of objects, e.g. in the HLR with create/modify/delete subscriber or create/modify/delete MSISDN or in the EIR with create/interrogate/delete equipment [57]. File transfer objects are used especially in the information model dealing with the registers, since it involves movement of large amounts of data.

Create Modify Delete

CMISE Common Management Information Service Element

QMAP Operatio n. M aintena nee a n d Adm i ni strata Part

FTAM File Transfer Access and Management

ROSE Remote Operation Service Element

ACSE Association Control Service Element

CMISE Common Management Information Service Element

QMAP Operatio n. M aintena nee a n d Adm i ni strata Part

FTAM File Transfer Access and Management

ROSE Remote Operation Service Element

ACSE Association Control Service Element

Figure 10.6: GSM network management protocols at the Q3-interface

The TMN communication platform to be used as Data Communication Network (DCN) can be either an OSI X.25 packet network or the SS#7 signaling network (MTP and SCCP). Both offer a packet switching service which can be used to transport management messages. Each network element is connected to this management network over a Management Network Access Point (MNAP); see Figure 10.5.

If the TMN uses X.25, the DCN can be the public PSPDN or a dedicated packet switching network within the PLMN with the MSC as a packet switching node. In addition, the MSC

can include an interworking function for protocol conversion from an external X.25 link to the SS#7 SCCP, which realizes the connection of the OMC to the PLMN through an external X.25 link. Further transport of management messages is then performed by the SS#7 network internal to the PLMN.

The framework defined for the GSM TMN protocol stack at the Q3 interface is presented in Figure 10.6. The end-to-end transport of messages between OS and NE is realized with the OSI Class 2 transport protocol (TP2), which allows the setup and multiplexing of end-to-end transport connections over an X.25 or SCCP connection. Error detection and data security are not provided in TP2; they are not needed since X.25 as well as SCCP offer a secure message transport service already.

Of course, the OSI protocol stack also needs the protocols for the data link and presentation layers. The OSI Common Management Information Service Element (CMISE) plays the central role in GSM network management. Its services are used by a System Management Application Process (SMAP) to issue commands, to receive notifications, to check parameters, etc. For file transfer between objects, GSM TMN uses the OSI File Transfer Access and Management Protocol (FTAM). It is designed for the efficient transport of large volumes of data.

CMISE needs a few more Service Elements (SEs) in the application layer for providing services: the Association Control Service Element (ACSE) and the Remote Operations Service Element (ROSE). The ACSE is a sublayer of the application layer which allows application elements (here CMISE) to set up and take down connections between each other. The ROSE services are realized with a protocol which enables initiation or execution of operations on remote systems. This way ROSE implements the paradigm also known as Remote Procedure Call (RPC).

Figure 1O.7: Operation and maintenance of the BSS

There is also a management system for the signaling components of a GSM system. This SS#7 SMAP uses the services of the Operation Maintenance and Administration Part (OMAP) which allows observation, configuration, and control of the SS#7 network resources. Essentially, the OMAP consists of two Application Service Elements (ASEs), the MTP Routing Verification Test (MRVT) and the SCCP Routing Verification Test (SRVT) which allow verification of whether the SS#7 network works properly on the MTP or SCCP planes. Another Management Application Part is the Base Station System Operation and Maintenance Application Part (BSSOMAP) which is used to transport management messages from OMC to BSC through the MSC over the A interface and to execute management activities for the BSS (Figure 10.7, and compare it with Figure 7.11) [53].

Nmc Omc Diagram
Figure 10.8: Hierarchical organization of network management within Germany

Network management is usually organized in a geographically centralized way. For the remote surveillance and control of network management functions there are usually one or more Operation and Maintenance Centers (OMCs). For efficient network management, these OMCs can be operated as regional subcenters according to the LLA hierarchy of the various TMN management planes, and they can be combined under a central Network Management Centre (NMC); see Figure 10.8.

GSM Switching, Services and Protocols: Second Edition. Jorg Eberspacher, Hans-Jorg Vogel and Christian Bettstetter Copyright © 2001 John Wiley & Sons Ltd Print ISBN 0-471-49903-X Online ISBN 0-470-84174-5

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  • duenna
    How gsm network architecture?
    8 years ago

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