8 Operation and maintenance

08.023GPPBase Station System - Mobile Services Switching Centre (BSS-MSC) Interface - Interface PrinciplesRelease 1999TS

Operation and maintenance information is required to flow between the BSS and O & M functions. The BSS to MSC interface provides for this type of information see 3GPP TSĀ 12.01.


DTAP – Direct Transfer Application Part

BSSMAP – BSS Management Application Part

BSS OMAP – BSS Operation and Maintenance Application Part

SCCP – Signalling Connection and Control Part

MTP – Message Transfer Part

BSS – Base Station System

MSC – Mobile services Switching Centre

NOTE: X.25 can be used for transferring O and M information.

Figure 1: Signalling protocol reference model

Annex A (informative):
Remote Mobile Switching Unit (RMSU)

A.1 Introduction

Between the MSC and some of the BSS sites served by this MSC , it may be advantageous to include a line concentrator, an RMSU. The main purpose of introducing this unit is to reduce the number of terrestrial circuits needed between BSS site and MSCs (signalling and traffic circuits). The benefits of introducing an RMSU will depend on:

– relative costs of the transmission plant for the particular administrations;

– the costs involved in operating the RMSU;

– the complexity of the RMSU, i.e. if it allows interworking with the ISDN or the PSTN for mobile originated calls.

In the 3GPP Technical Specifications the RMSU will be regarded as a remotely controlled part of the MSC, and therefore no detailed specification of the RMSU or the signalling functions needed between the RMSU and the MSC will be given.

A.2 Functions provided by the RMSU

Below is listed some examples of functions which may be provided by the RMSU:

– setting up and clearing of circuits to the BSS and the MSC (remotely controlled by the MSC);

– switching of the circuits between MSC and the various BSSs;

– blocking and unblocking of circuits;

– possibly interworking with the PSTN or ISDN for mobile originated calls, including information exchange with remote control from the MSC;

– Operation and maintenance functions of the RMSU.

A.3 General requirements

In order to be able to establish a BSS configuration without using an RMSU, and then later on introducing this unit, the interface between the BSSs and the RMSU should have the same characteristics as the interface between a BSS and an MSC.

The number of subscribers served by an RMSU will be large compared to the number of subscribers served by a single BSS. Therefore, if the RMSU or the signalling links between the RMSU and the MSC go down, this will have a serious impact on the mobile service in a large geographical area.

The implementation of the RMSU and the signalling between the RMSU and the MSC therefore has to be made in such a way that the overall reliability requirements specified for the MSC are fulfilled.

Some O and M facilities may be required in the RMSU, and the necessary signalling between the RMSU and the O and M functions has to be provided.

Annex B (informative):
Change History

Meeting / Date




New version


ETSI Publication




Definition of a circuit pool



Release 1996 version





CR on 3GPP TS 08.02 on Circuit allocation by the BSS



Release 1997 version



Release 1998 version



Release 1999 version


May 2002

Update to 3GPP TS style. References corrected. Annex headings corrected.