TS 25.424
UTRAN – Iur Interface –
Data Transport and Transport Signalling
for Common Transport Channel Data Streams

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Rapporteur:: Mr. Zhang, Hongzhuo

Content for TS 25.424 Word version: 18.0.0

1 Scope p. 5

The present document shall provide a specification of the UTRAN RNC-RNC (Iur) interface Data Transport and Transport Signalling for Common Transport Channel data streams.

2 References p. 5

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]

ITU-T Recommendation I.361 (1995-11): "B-ISDN ATM Layer Specification".

[2]

ITU-T Recommendation I.363.2 (2000-11): "B-ISDN ATM Adaptation Layer type 2".

[3]

ITU-T Recommendation I.366.1 (1998-06): "Segmentation and Re-assembly Service Specific Convergence Sublayer for the AAL type 2".

[4]

ITU-T Recommendation Q.2630.1 (1999-12): "AAL Type 2 signalling protocol (Capability Set 1)".

[5]

ITU-T Recommendation E.191 (2000-03): "B-ISDN addressing".

[6]

TS 25.426: "UTRAN Iur and Iub interface data transport & transport signalling for DCH data streams".

[7] Void

[8]

ITU-T Recommendation Q.2630.2 (2000-12): "AAL Type 2 signalling protocol (Capability Set 2)".

[9]

ITU-T Recommendation X.213 (1995-11): "Information Technology - Open Systems Interconnection - Network Service Definition".

[10]

RFC 1661 (1994-07): "The Point-To-Point Protocol (PPP)".

[11]

RFC 1662 (1994-07): "PPP in HDLC-like Framing".

[12]

RFC 2507 (1999-02): "IP header compression".

[13]

RFC 1990 (1996-08): "The PPP Multilink Protocol (MP)".

[14]

RFC 2686 (1999-09): "The Multi-Class Extension to Multi-Link PPP".

[15]

RFC 2509 (1999-02): "IP Header Compression over PPP".

[16]

RFC 2460 (1998-12): "Internet Protocol, Version 6 (Ipv6) Specification".

[17]

RFC 791 (1981-09): "Internet Protocol".

[18]

RFC 2474 (1998-12): "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers".

[19]

RFC 768 (1980-08): "User Datagram Protocol".

[20]

RFC 3153 (2001-08): "PPP Multiplexing".

[21]

RFC 2364 (1998-07): "PPP over AAL5".

[22]

RFC 3031 (2001-01): "Multiprotocol Label Switching Architecture".

[23]

ITU-T Recommendation E.164 (1997-05): " The international public telecommunication numbering plan ".

3 Definitions and abbreviations p. 6

3.1 Definitions p. 6

Common Transport Channels are defined as transport channels that are shared by several users i.e. RACH, FACH, DSCH [TDD], USCH [TDD] and HS-DSCH.

3.2 Abbreviations p. 6

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

AAL2

ATM Adaptation Layer type 2

AAL5

ATM Adaptation Layer type 5

AESA

ATM End System Address

ALCAP

Access Link Control Application Part

ATM

Asynchronous Transfer Mode

CPS

Common Part Sublayer

DiffServ

Differentiated Services

DSCH

Downlink Shared Channel

FACH

Forward Access Channel

HDLC

High level Data Link Control

HS-DSCH

High Speed Downlink Shared Channel

Internet Protocol

IPv4

Internet Protocol, version 4

IPv6

Internet Protocol, version 6

IWF

Interworking Function

IWU

Interworking Unit

Link Characteristics

ML/MC PPP

Multilink-Multiclass PPP

MPLS

Multiprotocol Label Switching

MTP

Message Transfer Part

NNI

Network-Node Interface

NSAP

Network Service Access Point

PPP

Point-to-Point Protocol

PPPMux

PPP Multiplexing

Path Type

QoS

Quality of Service

RACH

Random Access Channel

SAAL

Signalling ATM Adaptation Layer

SDU

Service Data Unit

SSCOP

Service Specific Connection Oriented Protocol

SSCF

Service Specific Co-ordination Function

SSCS

Service Specific Convergence Sublayer

SSSAR

Service Specific Segmentation and Re-assembly sublayer

STC

Signalling Transport Converter

TNL

Transport Network Layer

UDP

User Datagram Protocol

UNI

User-Network Interface

USCH

Uplink Shared Channel

3.3 Specification Notations |R7| p. 7

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

[FDD]

This tagging of a word indicates that the word preceding the tag "[FDD]" applies only to FDD. This tagging of a heading indicates that the heading preceding the tag "[FDD]" and the section following the heading applies only to FDD.

[TDD]

This tagging of a word indicates that the word preceding the tag "[TDD]" applies only to TDD, including 3.84Mcps TDD, 7.68Mcps TDD and 1.28Mcps TDD. This tagging of a heading indicates that the heading preceding the tag "[TDD]" and the section following the heading applies only to TDD, including 3.84Mcps TDD, 7.68Mcps TDD and 1.28Mcps TDD.

[3.84Mcps TDD]

This tagging of a word indicates that the word preceding the tag "[3.84Mcps TDD]" applies only to 3.84Mcps TDD. This tagging of a heading indicates that the heading preceding the tag "[3.84Mcps TDD]" and the section following the heading applies only to 3.84Mcps TDD.

[1.28Mcps TDD]

This tagging of a word indicates that the word preceding the tag "[1.28Mcps TDD]" applies only to 1.28Mcps TDD. This tagging of a heading indicates that the heading preceding the tag "[1.28Mcps TDD]" and the section following the heading applies only to 1.28Mcps TDD.

[7.68Mcps TDD]

This tagging of a word indicates that the word preceding the tag "[7.68Mcps TDD]" applies only to 7.68Mcps TDD. This tagging of a heading indicates that the heading preceding the tag "[7.68Mcps TDD]" and the section following the heading applies only to 7.68Mcps TDD.

[FDD - …]

This tagging indicates that the enclosed text following the "[FDD - " applies only to FDD. Multiple sequential paragraphs applying only to FDD are enclosed separately to enable insertion of TDD specific (or common) paragraphs between the FDD specific paragraphs.

[TDD - …]

This tagging indicates that the enclosed text following the "[TDD - " applies only to TDD including 3.84Mcps TDD, 7.68Mcps TDD and 1.28Mcps TDD. Multiple sequential paragraphs applying only to TDD are enclosed separately to enable insertion of FDD specific (or common) paragraphs between the TDD specific paragraphs.

[3.84Mcps TDD - …]

This tagging indicates that the enclosed text following the "[3.84Mcps TDD - " applies only to 3.84Mcps TDD. Multiple sequential paragraphs applying only to 3.84Mcps TDD are enclosed separately to enable insertion of FDD and TDD specific (or common) paragraphs between the 3.84Mcps TDD specific paragraphs.

[1.28Mcps TDD - …]

This tagging indicates that the enclosed text following the "[1.28Mcps TDD - " applies only to 1.28Mcps TDD. Multiple sequential paragraphs applying only to 1.28Mcps TDD are enclosed separately to enable insertion of FDD and TDD specific (or common) paragraphs between the 1.28Mcps TDD specific paragraphs.

[7.68Mcps TDD - …]

This tagging indicates that the enclosed text following the "[7.68Mcps TDD - " applies only to 7.68Mcps TDD. Multiple sequential paragraphs applying only to 7.68Mcps TDD are enclosed separately to enable insertion of FDD and TDD specific (or common) paragraphs between the 7.68Mcps TDD specific paragraphs.

4 Data Link Layer p. 7

4.1 ATM Transport Option p. 7

ATM shall be used in the transport network user plane and the transport network control plane according to ITU-T Recommendation I.361 [1]. The structure of the cell header used in the UTRAN Iur interface is the cell header format and encoding at NNI (see Figure 3/I.361 [1]).

4.2 IP Transport Option |R5| p. 8

A UTRAN Node supporting IP transport option shall support PPP protocol with HDLC framing (RFC 1661, RFC 1662).

An RNC using IP transport option having interfaces connected via slow bandwidth PPP links like E1/T1/J1 shall also support IP Header Compression (RFC 2507) and the PPP extensions ML/MC-PPP (RFC 1990), (RFC 2686). In this case, negotiation of header compression (RFC 2507) over PPP shall be performed via RFC 2509.

5 Iur Data Transport for Common Transport Channel Data Streams p. 8

5.1 Introduction p. 8

This clause specifies the transport layers that support Common Channels (FACH, RACH, DSCH [TDD], USCH [TDD], HS-DSCH) Iur data streams.

There are two options for the transport layer of the Common Channels data streams in Iur and Iub:

ATM based Transport (ATM transport option)
IP based Transport (IP transport option)

The following figure shows the protocol stacks of the two options.

Copy of original 3GPP image for 3GPP TS 25.424, Fig. 1: Transport network layer for DCH data streams over Iur and Iub interfaces

Figure 1: Transport network layer for DCH data streams over Iur and Iub interfaces
(⇒ copy of original 3GPP image)

5.2 ATM Transport Option p. 8

ATM (ITU-T Rec. I.361 [1]), AAL type 2 (ITU-T Recommendations I.363.2 [2] and ITU-T Rec. I.366.1 [3]) is used as the standard transport layer for RACH, FACH, USCH [TDD], DSCH [TDD] and HS-DSCH Iur data streams.

These AAL2 connections are established via the transport signalling protocol described in clause 5.

Figure 1 shows the protocol stack for the transport of RACH, FACH, USCH [TDD], DSCH [TDD] and HS-DSCH Iur data streams using the ATM Transport Option. Service Specific Segmentation and Re-assembly (SSSAR) is used for the segmentation and re-assembly of AAL2 SDUs (i.e. SSSAR is only considered from ITU-T Recommendation I.366.1 [3]).

5.3 IP Option |R5| p. 9

UDP (RFC 768) over IP shall be used as the transport for RACH, FACH, USCH [TDD], DSCH [TDD] and HS-DSCH data streams on Iur. The data link layer is as specified in subclause 4.2.

An IP UTRAN Node shall support IPv6 (RFC 2460). The support of IPv4 (RFC 791) is optional.

IP dual stack support is recommended for the potential transition period from IPv4 to IPv6 in the transport network.

The transport bearer is identified by the UDP port number and the IP address (source UDP port number, destination UDP port number, source IP address, destination IP address).

IP Differentiated Services code point marking (RFC 2474) shall be supported. The mapping between traffic categories and Diffserv code points shall be configurable by O&M. Traffic categories are implementation-specific and may be determined from the application parameters.

6 I ur Transport Signalling Application for Common Transport Channel Data Streams p. 9

6.1 Introduction p. 9

This clause specifies the transport signalling protocol(s) used to establish the user plane transport bearers. The protocol stack is shown in TS 25.426.

6.2 Transport Signalling in case of ATM option p. 9

AAL2 signalling protocol Capability Set 2, ITU-T Recommendation Q.2630.2 [8], is the signalling protocol to control the AAL2 connections on Iur interfaces. ITU-T Rec. Q.2630.2 [8] adds new optional capabilities to ITU-T Rec. Q.2630.1 [4].

AAL2 transport layer addressing is based on embedded E.164 or other AESA variants of the NSAP addressing format ITU-T Rec. E.191 [5], ITU-T Rec. X.213 [9]. Native E.164 (ITU-T Rec. E.164 [23]) addressing shall not be used.

Binding ID provided by the radio network layer shall be copied in SUGR parameter of ESTABLISH.request primitive of ITU-T Rec. Q.2630.2 [8]. The binding identifier shall already be assigned and tied to a radio application procedure when the Establish Request message is received over the Iur interface in the Drift RNC.

User Plane Transport bearers are established by the ALCAP in Serving RNC, and in all normal cases released by the ALCAP in the RNC which established the AAL2 connection.

The Link Characteristics parameter (LC) shall be included in the Establish Request message and in the Modification Request message of AAL2 signalling protocol.

If there is an AAL2 switching function in the transport network layer of the interface, the Path Type parameter (PT) may be included in the Establish Request message of AAL2 signalling protocol for prioritisation at ATM level.

If the value in either the Maximum CPS-SDU Bit Rate or the Average CPS-SDU Bit Rate of the Link Characteristics(LC) in AAL 2 signalling messages as specified in reference ITU-T Rec. Q.2630.2 [8] is 2048 Kbit/s, it shall be interpreted as bit rate 2048 Kbit/s or higher.

6.3 Transport Signalling in case of IP Transport Option |R5| p. 10

An ALCAP protocol is not required in case both RNCs are using the IP transport option.

7 Signalling Bearer for ALCAP on Iur Interface p. 10

7.1 ATM Transport Option |R5| p. 10

The signalling bearer for the ALCAP on the Iur interface for common transport channels data streams is the same as the signalling bearer for the ALCAP on the Iur interface for DCH data streams, defined in TS 25.426.

7.2 IP Transport Option |R5| p. 10