Content for  TS 23.236  Word version:  16.0.0

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0  IntroductionWord‑p. 5
UMTS will build on the success of GSM and is likely to become even more widespread, increasing the importance of a flexible network structure to permit the different operational configurations in which these networks will be deployed. The requirements to have a RNC or BSC controlled by a single MSC server or SGSN lead to certain limitations. Allowing the BSCs and RNCs to connect to a number of MSC servers or SGSNs increases the networks performance in terms of scalability, distributing the network load amongst the serving entities, and reducing the required signalling as the user roams.

1  ScopeWord‑p. 6
This document covers the details for the Intra Domain Connection of RAN Nodes to Multiple CN Nodes for GERAN and UTRAN based systems. In particular, it details the impacts to GSM and UMTS systems and the stage 2 procedures for the support of connecting a RNC or BSC to multiple MSC servers or SGSNs. The overall solution is described, and the detailed impacts on the existing specifications are identified. The description of a broadly similar concept for E-UTRAN based systems is not described in the document: instead, it is described in TS 23.401.
The reference model to which these procedures apply can be found within TS 23.002. Detailed architectural requirements within the subsystems are contained within the remainder of the 23 series of specifications e.g. the requirements for the Packet Switched (PS) domain are contained within TS 23.060 and the requirements for the Bearer Independent CS Core Network are contained in TS 23.205.

2  References

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 23.002: "Network Architecture".
TS 23.060: "General Packet Radio Service (GPRS) Service description; Stage 2".
TS 23.012: "Location management procedures".
TS 25.331: "Radio Resource Control (RRC) Protocol Specification".
TS 25.301: "Radio interface protocol architecture".
TS 25.303: "UE functions and inter-layer procedures in connected mode".
TR 21.905: "3G Vocabulary".
TS 25.413: "UTRAN Iu interface RANAP signalling".
TS 25.410: "UTRAN Iu Interface: General Aspects and Principles".
TS 23.228: "IP Multimedia Subsystem - Stage 2".
TS 43.051: "GSM/EDGE Radio Access Network (GERAN) overall description (Stage 2)".
TS 23.153: "Out of Band Transcoder Control - Stage 2".
TS 23.205: "Bearer Independent CS Core Network - Stage 2".
TR 25.931: "UTRAN Functions, examples on signalling procedures".
GSM 08.18: "General Packet Radio Service (GPRS);Base Station System (BSS) -Serving GPRS Support Node (SGSN); BSS GPRS Protocol (BSSGP)".
TS 48.008: "Mobile-services Switching Centre - Base Station System (MSC - BSS) interface; Layer 3 specification".
TS 23.003: "Numbering, addressing and identification".
TS 43.068: "Voice Group Call Service (VGCS); Stage 2".
TS 43.069: "Voice Broadcast Service (VBS); Stage 2".
TS 23.251: "Network Sharing; Architecture and functional description".
TS 23.401: "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access".
TR 23.924: "Feasibility Study on NAS Node Selection Function above BSC/RNC".

3  Definitions, symbols and abbreviationsWord‑p. 7

3.1  Definitions

For the purposes of the present document, the terms defined in TR 21.905 apply:
CN node:
for the purpose of this specification, and unless otherwise stated, a CN node is either an MSC or an SGSN.
NAS node selection Function:
The function used to assign specific network resources (i.e. MSC or SGSN) to serve a mobile station and subsequently route the traffic to the assigned network resource.
Network Resource Identifier:
A specific parameter used to identify the CN node assigned to serve a mobile station.
Non-broadcast LAI/RAI:
Each CN node in a pool have to be assigned one unique non-broadcast LAI/RAI that it use in case it want to be offloaded. Each CN node in the pool has to be aware of the non-broadcast LAI/RAI assigned to the other CN nodes in the pool, because in case of re-distribution the 'target CN node' will retrieve data (e.g. IMSI, security context, MM & PDP contexts) from the 'offloaded CN node' based on non-broadcast LAI/RAI.
A 'null-NRI' indicates to a radio node (BSC/RNC) that the NAS Node Selection Function shall be used for selecting a CN node to receive a message. There is one unique 'null-NRI' in a PLMN supporting pool functionality. In MOCN shared networks (see TS 23.251) with multiple CN Operators, there is one unique 'null-NRI' per CN operator. That is, in MOCN networks the RAN Operator handles multiple 'null-NRIs'.
A pool area is an area within which a MS may roam without need to change the serving CN node. A pool area is served by one or more CN nodes in parallel. All the cells controlled by a RNC or BSC belong to the same one (or more) pool area(s).
RAN node:
for the purpose of this specification, and unless otherwise stated, a RAN node is either an RNC or a BSC.
RAN node service area:
This area contains all the cells controlled by the RNC or BSC.

3.2  Symbols

For the purposes of the present document, the following symbols apply:

3.3  Abbreviations

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
Access Stratum
Base Station Controller
BSSGP Virtual Connection Identifier
Core Network
Circuit Switched
Circuit Switched Media Gateway
Dedicated Core Network
Directory Name Server
Intra Domain NAS Node Selector
Location Area
Location Area Identity
Multi-Operator Core Network
Mobile Station
Mobile Switching Centre
Non Access Stratum
Network Resource Identifier
Operation and Maintenance
Packet Switched
Routing Area
Routing Area Identity
Radio Access Network
Radio Network Controller
Serving Radio Network Subsystem
Temporary Mobile Station Identity
Temporary Logical Link Identifier
User Equipment

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