The present document defines a set of Circuit Bearer Services to be provided to PLMN subscribers by a PLMN itself and in connection with other networks. This TS should also be used as a reference for defining the corresponding required mobile network capabilities.
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TS 29.010: "Information element mapping between Mobile Station - Base Station System and BSS - Mobile-services Switching Centre (MS - BSS - MSC) Signalling procedures and the Mobile Application Part (MAP)".
Bearer Services are described by attributes, which are intended to be independent. These attributes are described and defined in TS 22.001. They are grouped into four categories:
Information transfer attributes, which characterize the network capabilities for transferring information from a user access point in a PLMN to a user access point in another network. (Refer to TS 22.001 ).
Access attributes, which describe the means for accessing network functions or facilities as seen at the access point in the PLMN (see TS 22.001).
Interworking attributes, which describe properties of the terminating network and its access point. The terminating network may include another PLMN or the originating PLMN.
General attributes, which deal with the service in general.
Figure 1 shows the relation between the groups of attributes and their fields of applicability.
Attributes that are not part of the minimal set provide further technical detail and are required to fully define the use of each Bearer Service.
See specifications TS 27.001, TS 27.002, TS 27.003, TS 27.005 for information about the Signalling Access Protocols, Information Access Protocols and related access attributes.
Supplementary services are defined in TS 22.004.
Intercommunication is required with services in the PSTN, ISDN and other PLMNs. The capabilities that describe the Interworking Attributes are described in specifications TS 29.002 to TS 29.007 and .
All Bearer Service categories provide information transfer between the reference points and allow the use of sub-rate information streams which are rate-adapted.
The Bearer Services can be grouped into the following categories:
Unrestricted Digital Information (UDI);
Provides the transfer of unrestricted digital information.
3,1 kHz (External to the PLMN);
Used to select a "3,1 kHz audio" interworking function at the MSC. This service category is used when interworking with the ISDN or PSTN "3,1 kHz audio" service and includes the capability to select a modem at the interworking function. "External to the PLMN" indicates that the "3,1 kHz audio" service is only used outside of the PLMN, in the ISDN/PSTN. The connection within the PLMN, user access point to the interworking function, is an unrestricted digital connection.
This clause provides a list of the existing Bearer Services and indicates the values for each attribute in the minimal set.
The following attributes have the same value for all Bearer Services. Their values are as follows:
Information Transfer Mode:
Information Transfer Rate:
Not applicable (note 1);
Establishment of Communication:
"Point to point".
All asynchronous NT Bearer Services may support data compression to enhance user data throughput.
NT Bearer Services 20 may support V.120 interworking, enabling data terminals connected to an UE to interwork with V.120  terminal adapters on the ISDN as shown in the Figure 2 below.
The Tables below describe the characteristics of the General Bearer Services. The indicated fixed network user rates are possible, but support of General Bearer Service does not imply support of all rates.