ETSI TS 143 130 V13.0.0 (2016-01)

Digital cellular telecommunications system (Phase 2+); Iur-g interface; Stage 2 (3GPP TS 43.130 version 13.0.0 Release 13)

RTS/TSGG-0143130vd00

General Information

• Status: Published
• Publication Date: 21-Jan-2016
• Technical Committee: 3GPP GERAN 1 - Radio aspects
• Current Stage: 12 - Completion
• Due Date: 19-Jan-2016
• Completion Date: 22-Jan-2016

Standards Content (Sample)

ETSI TS 1143 130 V13.0.0 (201616-01)






TECHNICAL SPECIFICATIONION
Digital cellular telecocommunications system (Phahase 2+);
Iur-g interface;
Stage 2
(3GPP TS 43.1.130 version 13.0.0 Release 13 13)

R
GLOBAL SYSTTEME FOR
MOBILE COMMUUNNICATIONS

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3GPP TS 43.130 version 13.0.0 Release 13 1 ETSI TS 143 130 V13.0.0 (2016-01)



Reference
RTS/TSGG-0143130vd00
Keywords
GSM
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3GPP TS 43.130 version 13.0.0 Release 13 2 ETSI TS 143 130 V13.0.0 (2016-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
http://webapp.etsi.org/key/queryform.asp.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI

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3GPP TS 43.130 version 13.0.0 Release 13 3 ETSI TS 143 130 V13.0.0 (2016-01)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 4
1 Scope . 5
2 References . 5
3 Definitions, symbols and abbreviations . 5
3.1 Definitions . 5
3.2 Symbols . 6
3.3 Abbreviations . 6
4 Motivation, principles and assumptions . 7
4.1 Motivation . 7
4.2 Principles . 7
4.3 Void . 8
5 General aspects . 8
5.1 Network architecture . 8
5.1.1 General . 8
5.1.2 MS Identifiers in Iu mode . 9
5.1.3 MS Identifiers in A/Gb mode . 10
5.2 Iur-g interface capabilities . 10
6 I Interface Protocols . 10
ur
6.1 General . 10
6.2 Functions of the Iur-g interface protocols . 11
6.3 Iur-g Interface protocol structure . 11
6.4 Radio signalling protocols . 12
7 Radio Network Layer: RNSAP protocol . 12
7.1 General . 12
7.2 Basic mobility procedures . 13
7.2.1 General . 13
7.2.2 Paging . 13
7.2.3 Cell Update . 14
7.2.4 Registration Area Update . 15
7.2.5 RRC Connection Release . 16
7.2.6 Radio Resource Reserve Handover . 16
7.2.6.1 General . 16
7.2.6.2 Successful operation. 17
7.2.6.3 Abnormal conditions . 18
7.2.6.3.1 BSS Radio Resource Reservation Failure . 18
7.2.6.3.2 Handover failure from MS/UE . 19
7.3 Void . 20
7.4 Global procedures. 20
7.4.1 General . 20
7.4.2 Error Indication . 20
7.4.3 Common Measurement Functions . 20
7.4.4 Information Exchange Functions . 21
Annex A (Informative): Change history . 22
History . 23

ETSI

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3GPP TS 43.130 version 13.0.0 Release 13 4 ETSI TS 143 130 V13.0.0 (2016-01)
Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI

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3GPP TS 43.130 version 13.0.0 Release 13 5 ETSI TS 143 130 V13.0.0 (2016-01)
1 Scope
The present document provides an overview of the Iur-g interface. It describes the motivation, principles and
functionality of this interface. It does not contain the detailed description, which it is included in the stage 3 Technical
Specifications.
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.
[1] 3GPP TR 21.905, '3rd Generation Partnership Project; Technical Specification Group Services and
System Aspects; Vocabulary for 3GPP Specifications'
[2] 3GPP TS 23.236, '3rd Generation Partnership Project; Technical Specification Group Services and
System Aspects; Intra-domain connection of Radio Access Network (RAN) nodes to multiple
Core Network (CN) nodes'
[3] 3GPP TS 25.331, '3rd Generation Partnership Project; Technical Specification Group Radio
Access Network; RRC Protocol Specification'
[4] 3GPP TS 25.420, '3rd Generation Partnership Project; Technical Specification Group Radio
Access Network; UTRAN Iur Interface General Aspects and Principles'
[5] 3GPP TS 25.423, '3rd Generation Partnership Project; Technical Specification Group Radio
Access Network; UTRAN Iur Interface RNSAP Signalling'
[6] 3GPP TS 43.051, 'Technical Specification 3rd Generation Partnership Project; Technical
Specification Group GSM/EDGE Radio Access Network; Overall description - Stage 2; (Release
5)'
[7] 3GPP TS 44.118, '3rd Generation Partnership Project; Technical Specification Group GSM EDGE
Radio Access Network; Mobile radio interface layer 3 specification, Radio Resource Control
Protocol (RRC); Iu mode'
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 [1] and the following
ones apply:
A/Gb mode: mode of operation of the MS when connected to the Core Network via GERAN and the A and/or Gb
interfaces.
MS: Unless stated otherwise, this refers with no distinction to both MS and UE.
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3GPP TS 43.130 version 13.0.0 Release 13 6 ETSI TS 143 130 V13.0.0 (2016-01)
Iu mode: mode of operation of the MS when connected to the Core Network via GERAN or UTRAN and the Iu
interface.
RAN node: a BSS or a RNC.
3.2 Symbols
For the purposes of the present document, the following symbols apply:
A Interface between a BSS and an MSC
Gb Interface between a BSS and an SGSN
Iu Interface between a BSS/RNC and the CN
Iur Interface between two RNSs
Iur-g Interface between two BSSs or between a BSS and an RNS
Um Interface between a GERAN MS and a BSS
Uu Interface between a UE and the RNS
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
BSC Base Station Controller
BSS Base Station Sub-system
CBSS Controlling Base Station Sub-system
CN Core Network
CRNC Controlling Radio Network Controller
GERAN GSM/EDGE Radio Access Network
GPRS General Packet Radio Service
GRA GERAN Registration Area
LA Location Area
MS Mobile Station
MSC Mobile Switching Centre
NACC Network Assisted Cell Change
NNSF NAS Node Selection Function
RA Routeing Area
RAN Radio Access Network
RNC Radio Network Controller
RNS Radio Network Sub-system
RNSAP Radio Network Subsystem Application Part
RNTI Radio Network Temporary Identity
RRA RAN Registration Area
RRM Radio Resource Management
SBSC Serving BSC
SBSS Serving BSS
SGSN Serving GPRS Support Node
SRNC Serving RNC
TBSS Target BSS
UE User Equipment
UMTS Universal Mobile Telephony System
URA UTRAN Registration Area
UTRAN UMTS Terrestrial Radio Access Network
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3GPP TS 43.130 version 13.0.0 Release 13 7 ETSI TS 143 130 V13.0.0 (2016-01)
4 Motivation, principles and assumptions
4.1 Motivation
As part of the work to connect GERAN via the Iu interface to the CN, the GRA and RNTI concepts have also been
adopted for the GERAN. With these concepts, an inactive mobile in the RRC-GRA_PCH state (see
3GPP TS 44.118 [7]) will perform signalling to the network whenever it changes the GRA. Since GRAs need not be
constrained by BSC coverage areas, it is possible that the MS reselects a cell on a different BSC but on the same GRA.
In order maintain the ability to page the mobile in the GRA with the correct RNTI, as well as to enable a path for a
GRA update procedure with the serving BSC, it is necessary to have an Iur-g interface between the BSSs.
The same principle applies for dual-RAN capable mobiles. The architecture specifications permit network operators to
design networks that alleviate the potential problem caused by dual mode mobiles frequently toggling between UTRAN
and GERAN coverage areas (e.g. in indoor coverage situations): for instance, common LAIs and RAIs for GERAN and
UTRAN cells in the same geographical area. Defining GERAN and UTRAN cells in common LAs and RAs permits an
inactive mobile to change from GERAN to UTRAN coverage or, vice versa, without any signalling to the network.
Prior to Release 5, this is possible because GSM/GPRS is does not use the connection oriented Iu interface. From
Release 5 on, an inactive MS would signal to the network when a cell change involving change of RAN takes place. To
prevent this, operators may configure GRA IDs and URA IDs to indicate the same registration area. To enable paging
across these registration areas, as well as to enable the possibility to perform GRA/URA update procedures with the
serving BSC/RNC, it is necessary to have an Iur-g interface between the BSS and the RNC.
The definition of GRAs/URAs has the following benefits:
- It increases the MT call success rate: by reducing the frequency of updates, it reduces the time during which the
MS is believed by the RAN to be in the old registration area, when paging requests would fail.
- It reduces the amount of signalling on the radio interface, since the mobile does not need to indicate cell changes
when moving within a GRA/URA.
- For the same reason, it reduces the amount of signalling in the network, thus decreasing the number of updates
and of SRNC/SBSC relocation procedures.
The Iur-g may bring other benefits:
- Support for the SRNC/SBSC relocation procedure: the current SRNS relocation procedure defined for UTRAN
using the Iur interface could be reused, improving the performance of the procedure. The Cell Update and
Relocation Commit messages could be transferred over this interface.
4.2 Principles
The Iur-g interface shall be designed based on the following principles:
- The Iur-g interface shall be open.
- From a logical standpoint, this interface is a point to point interface between one BSS and one BSS or RNC
within a PLMN. From a physical point of view, the interface could share Iu or other transmission resources.
- The Iur-g interface is optional. The presence of the Iur-g shall be transparent to the MS: the 3GPP specifications
shall ensure that all mobiles function correctly irrespective of the presence or absence of the Iur-g interface.
- This interface shall support the exchange of signalling information between a BSS and a BSC/RNC. The Iur-g
interface shall not carry user information.
- A GRA contains one or more GERAN cells and zero or more UTRAN cells. A URA contains one or more
UTRAN cells and zero or more GERAN cells.
NOTE: The term RAN Registration Area (RRA) is used in this document to refer to a registration area
irrespective of whether it contains GERAN cells, UTRAN cells or both types of cells. The terms GRA
and URA will be used in GERAN and UTRAN specifications, respectively, where GRAs may contain
UTRAN cells and URAs may contain GERAN cells.
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UTRA-NTDD
UTRAN
3GPP TS 43.130 version 13.0.0 Release 13 8 ETSI TS 143 130 V13.0.0 (2016-01)
- In Iu mode, the BSC has been allocated an identifier (BSC-Id) from the same pool of numbers as the RNC-Id.
4.3 Void

5 General aspects
5.1 Network architecture
5.1.1 General
The Iur-g interface is the logical interface between two BSSs in Iu mode or between an RNS and a BSS in Iu mode or
between a BSS in A/Gb mode and a UTRA-NTDD RNS. The different Iur-g interface combinations are depicted in
Figure 1 and Figure 1a.


3G Core Network
Iu Iu Iu
Iur-g
Iur-g
BSS BSS RNS
Um
MS/UE


Figure 1: Reference architecture for the Iur-g interface (BSS in Iu mode).
3G/2G Core Network
Iu
A Gb A Gb
Iur-g
BSS BSS RNS
Um
MS/UE

Figure 1a: Reference architecture for the Iur-g interface (BSS in A/Gb mode)

ETSI
GERAN
GERAN

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3GPP TS 43.130 version 13.0.0 Release 13 9 ETSI TS 143 130 V13.0.0 (2016-01)
5.1.2 MS Identifiers in Iu mode
The Radio Network Temporary Identities (RNTI) are used as MS/UE identifiers within the GERAN/UTRAN and in
signalling messages between MS/UE and GERAN. Four types of RNTI exist:
1) Serving BSS/RNC RNTI (S-RNTI);
2) Drift BSS/RNC RNTI (D-RNTI);
3) Cell RNTI (C-RNTI);
4) UTRAN RNTI (U-RNTI) or GERAN RNTI (G-RNTI);
The S-RNTI is used:
- by the MS/UE to identify itself to the Serving BSS/RNC;
- by the SBSS/SRNC to address the MS/UE; and
- by the DBSS/DRNC to identify the MS/UE to serving BSS/RNC.
The S-RNTI is allocated for all MSs/UEs having an RRC connection. It is allocated by the serving BSS/RNC and it is
unique within the serving BSS/RNC. The S-RNTI is reallocated always when the serving BSS/RNC for the RRC
connection is changed.
The D-RNTI is used by the serving BSS/RNC to identify the MS/UE to the drift BSS/RNC.
NOTE: The D-RNTI is never used on the Um/Uu interface.
The D-RNTI is allocated by the drift BSS/RNC upon drift MS/UE contexts establishment and it shall be unique within
the drift BSS/RNC. Serving BSS/RNC shall know the mapping between the S-RNTI and the D-RNTIs allocated in the
drift BSS for the same MS/UE. The drift BSS/RNC shall know the S-RNTI and SBSS-ID/RNC-ID related to the
existing D-RNTI within the drift BSS/RNC.
The C-RNTI is used this identifier is used only in UTRAN:
- in case of the Iur-g interface between UTRAN and GERAN (specifically the case of a SBSS and DRNC);
- by the UE to identify itself to the controlling RNC; and
- by the controlling RNC to address the UE.
The C-RNTI is allocated by the controlling RNC upon UE accessing a new cell. The C-RNTI shall be unique within the
accessed cell. The controlling RNC shall know the D-RNTI associated to the C-RNTI within the same logical RNC (if
any).
The G-RNTI/U-RNTI is allocated to an MS/UE having an RRC connection and it identifies the MS/UE within
GERAN/UTRAN. The G-RNTI/U-RNTI is composed of:
- SBSS/SRNC identity; and
- S-RNTI.
Each BSS/RNC has a unique identifier within the GERAN/UTRAN part of the PLMN, denoted by BSS/RNC identifier
(BSS-ID/RNC-ID). This identifier is used to route GERAN/UTRAN interface messages to the correct BSS/RNC. The
BSS-ID/RNC-ID of the serving BSS/RNC together with the S-RNTI is a unique identifier of the MS/UE in the
GERAN/UTRAN part of the PLMN.
From this architecture, there are three possible scenarios for a particular MS/UE:
a) Both the serving and the controlling RAN nodes are BSCs.
b) The serving RAN node is a BSC and the controlling RAN node is an RNC.
c) The serving RAN node is an RNC and the controlling RAN node is a BSC.
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UTRAN
UTRA-NTDD
UTRAN
UTRAN
3GPP TS 43.130 version 13.0.0 Release 13 10 ETSI TS 143 130 V13.0.0 (2016-01)
These scenarios are shown in Figure 2.

3G Core Network 2G/3G Core Network 3G/2G Core Network
Iu Iu Iu Iu Iu Iu Iu Iu Iu
Iur-g Iur-g Iur-g Iur-g
Iur-g Iur-g
CBSS SBSS RNS BSS BSS CBSS SRNS
SBSS CRNS
Um Um
Uu
MS/UE MS/UE MS/UE
a) b)
c)

Figure 2: Scenarios using the Iur-g interface (BSS in Iu mode)
5.1.3 MS Identifiers in A/Gb mode
The Radio Network Temporary Identity (RNTI) is used as a MS/UE identifier within the GERAN/UTRAN. One type of
RNTI exists:
- Drift RNTI (D-RNTI)
The D-RNTI is allocated by the TBSS and is used to identify the MS/UE during a handover via the Iur-g interface.
There is one possible scenario in which the D- RNTI is used:
a) The serving RAN node is a UTRA-NTDD RNC and the target RAN node is a BSS

3G/2G Core Network
Iu
A Gb A Gb
Iur-g Iur-g
BSS TBSS SRNS
Uu
MS/UE

Figure 2a: Scenario using the Iur-g interface (BSS in A/Gb mode)

5.2 Iur-g interface capabilities
The Iur-g interface provides capability to support radio interface mobility between BSSs or between a BSS and an RNS
of UEs having a connection with the GERAN or the UTRAN. This capability includes the support of paging, cell
update, registration area update and handover between BSSs or between a BSS and an RNS. Further, Iur-g interface
provides capability to support information exchange between two BSSs or between a BSS and RNS.
6 I Interface Protocols
ur
6.1 General
There shall exist a clear separation between the Radio Network Layer and the Transport Layer. Therefore, the radio
network signalling is separated from the data transport resource and traffic handling as shown in Figure 3. This
separation is also present in the Iur interface (see 3GPP TS 25.420 [4]).
ETSI
GERAN
GERAN
GERAN
GERAN

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3GPP TS 43.130 version 13.0.0 Release 13 11 ETSI TS 143 130 V13.0.0 (2016-01)
Since the Iur-g does not carry user data information, neither data transport resources nor Transport Signalling are
present on this interface. These elements, present in the Iur interface but not in the Iur-g, are shown in dotted lines in
Figure 3.
Radio
Radio User Plane
Signalling
Framing
Network
Protocols
Protocols
Layer
Transport
Signalling
Transport
Layer Signalling Data
Bearer Transport

Figure 3: Separation of Radio Network Protocols and transport over Iur-g.
The following Table lists all stage 3 specifications that are used for Iur-g interface:
Table 1: Stage 3 Iur-g interface specifications
Spec. No Spec. Name
TS 25.401 UTRAN Overall Description
TS 25.420 UTRAN Iur Interface: General Aspects and Principles
TS 25.421 UTRAN Iur interface Layer 1
TS 25.422 UTRAN Iur Interface Signalling Transport
TS 25.423 UTRAN Iur Interface RNSAP Signalling

6.2 Functions of the Iur-g interface protocols
The list of functions on the Iur-g interface is the following:
- Paging. This function allows the SBSS/SRNC to page a MS/UE in a GRA/URA or a cell in the DBSS/DRNS;
- Relocation Execution. This function allows the SBSS/SRNC to finalise a Relocation previously prepared via
other interfaces;
- Reporting of General Error Situations. This function allows reporting of general error situations, for which
function specific error messages have not been defined.
- Measurements on Common Resources. This function allows an BSS/RNC to request from another BSS/RNC
to initiate measurements on Common Resources. The function also allows the requested BSS/RNC to report the
result of the measurements.
Radio Resource Reserve Handover. This function allows the SRNC to request allocation of radio resources in
the TBSS prior to the HANDOVER REQUEST message is received from the Core Network.

6.3 Iur-g Interface protocol structure
The Iur interface protocol architecture consists of two functional layers:
- Radio Network Layer: it defines the procedures related to the interaction of two BSSs or between a BSS and an
RNC within a PLMN. The radio network layer consists of a Radio Network Control Plane and a Radio Network
User Plane. The functionality of the Radio Network User Plane of the Iur-g interface is null.
- Transport Layer: it consists of two planes:
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3GPP TS 43.130 version 13.0.0 Release 13 12 ETSI TS 143 130 V13.0.0 (2016-01)
a) Transport Network Control Plane: it defines procedures for establishing physical connections between two
BSSs or between a BSS and an RNC within a PLMN. The functionality of the Transport Network Control
Plane of the Iur-g interface is null.
b) Transport Network User Plane: it provides means for the transport of the Radio Network Layer
information.


Radio
Contro
...