RANAP Document

38
Switching Core Network Signalling Radio Access Network Application Part (RANAP) Training Document M14/U4 © Nokia Siemens Networks 1 (38)

description

umts

Transcript of RANAP Document

Page 1: RANAP Document

Switching Core Network Signalling

Radio Access Network Application Part (RANAP)

Training Document M14/U4

© Nokia Siemens Networks 1 (31)

Page 2: RANAP Document

Legal notice

Intellectual Property Rights

All copyrights and intellectual property rights for Nokia Siemens Networks training documentation, product documentation and slide presentation material, all of which are forthwith known as Nokia Siemens Networks training material, are the exclusive property of Nokia Siemens Networks. Nokia Siemens Networks owns the rights to copying, modification, translation, adaptation or derivatives including any improvements or developments. Nokia Siemens Networks has the sole right to copy, distribute, amend, modify, develop, license, sublicense, sell, transfer and assign the Nokia Siemens Networks training material. Individuals can use the Nokia Siemens Networks training material for their own personal self-development only, those same individuals cannot subsequently pass on that same Intellectual Property to others without the prior written agreement of Nokia Siemens Networks. The Nokia Siemens Networks training material cannot be used outside of an agreed Nokia Siemens Networks training session for development of groups without the prior written agreement of Nokia Siemens Networks.

Indemnity

The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia Siemens Networks customers only for the purposes of the agreement under which the document is submitted, and no part of it may be used, reproduced, modified or transmitted in any form or means without the prior written permission of Nokia Siemens Networks. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation.

The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardware or software products are given “as is” and all liability arising in connection with such hardware or software products shall be defined conclusively in a separate agreement between Nokia Siemens Networks and the customer. However, Nokia Siemens Networks has made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia Siemens Networks will, if deemed necessary by Nokia Siemens Networks, explain issues which may not be covered by the document.

Nokia Siemens Networks will correct errors in the document as soon as possible. IN NO EVENT WILL NOKIA SIEMENS NETWORKS BE LIABLE FOR ERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDIRECT, INCIDENTAL OR CONSEQUENTIAL OR ANY MONETARY LOSSES,SUCH AS BUT NOT LIMITED TO LOSS OF PROFIT, REVENUE, BUSINESS INTERRUPTION, BUSINESS OPPORTUNITY OR DATA,THAT MAY ARISE FROM THE USE OF THIS DOCUMENT OR THE INFORMATION IN IT

This document and the product it describes are considered protected by copyrights and other intellectual property rights according to the applicable laws.

Wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark of Nokia Corporation. Siemens is a registered trademark of Siemens AG. 

Other product names mentioned in this document may be trademarks of their respective owners, and they are mentioned for identification purposes only.

Copyright © Nokia Siemens Networks 2008. All rights reserved.

2 (31) © Nokia Siemens Networks

Page 3: RANAP Document

Contents

Contents

1 Introduction...............................................................................5

2 Interface towards Radio Network............................................62.1 Base Station Subsystem Application Part (BSSAP)...................62.1.1 BSSAP Functions.......................................................................72.2 Radio Access Network Application Part (RANAP).....................82.2.1 RANAP Elementary Procedures.................................................92.3 Example of RAB Messages: RAB Assignment Request..........11

3 Examples of RANAP Procedures..........................................133.1 RANAP Messages in Location Update.....................................133.1.1 Initial UE Message....................................................................143.1.2 Direct Transfer..........................................................................153.1.3 Iu Release................................................................................153.2 RANAP Messages in Call Setup..............................................163.2.1 Location Reporting Control.......................................................183.2.2 RAB (Radio Access Bearer) Assignment.................................193.3 AAL type 2 Signalling Protocol.................................................193.3.1 Establish Request (ERQ).........................................................203.3.2 Establish Confirm (ECF)...........................................................203.3.3 Release Request (REL)............................................................203.3.4 Release Confirm (RLC)............................................................20

4 Examples of RANAP Functions............................................214.1.1 Relocating Serving RNC...........................................................214.1.2 Overall RAB Management........................................................234.1.3 Requesting RAB Release.........................................................234.1.4 Release all Iu Connection Resources......................................244.1.5 Requesting the Release of all Iu Connection Resources.........254.1.6 Controlling Overload in the Iu Interface....................................254.1.7 Resetting the Iu........................................................................264.1.8 Sending the UE Common ID (Permanent NAS UE Identity) to

RNC..........................................................................................274.1.9 Paging the User........................................................................284.1.10 Controlling the Tracing of UE Activity.......................................284.1.11 Transport of NAS Information between UE and CN.................294.1.12 Controlling the Security Mode in the UTRAN...........................304.1.13 Controlling Location Reporting.................................................314.1.14 Reporting General Error Situation............................................31

© Nokia Siemens Networks

3 (31)

Page 4: RANAP Document

Summary of changes

This module is an upgrade for M14/U4. There is additional picture of RANAP and BSSAP in Release 4 configuration. Example of RANAP message contents is outlined.

4 (31) © Nokia Siemens Networks

Page 5: RANAP Document

Examples of RANAP Functions

1 Introduction

Radio Access Network Application Part (RANAP) provides the signalling service between UTRAN (RNC) and CN (MSS). RANAP is transported over MGW via IuCS interface to the MSS via Sigtran (M3UA and SCTP). In IuCS the transport in M14/U4 is ATM. There is possibility of IP transport in the later version of U4.

RANAP for M14 is defined in 3GPP standard TS 25413 version 4.10.0

BSSAP as the signalling in 2 G network will be transported to MGW as well in the Release 4 configuration and end at MSS.

RANAP and BSSAP configuration in the Release 4 network is shown below.

5 © Nokia Siemens Networks Presentation / Author / Date / Document NumberFor public use – IPR applies

RANAP and BSSAP in MSS ConceptUser Plane DataControl Plane

BS BSC

RANAP

RANAP/

BSSAP

RANAP/

BSSAP

MSS

MSS

BS

BS

BS

BS

BS

A

A

A

A’

BSC BSC

RNC

RNC

RNC

Iu-CS

Iu-CS

RANAP/

BSSAP

Iu-CS

RANAP

RANAP

RANAP

BSSAP

BSSAPBSSAP BSSAP

BSSAP’

Mc

Mc

Mc

Nc BICC

MGWRel.4

MGWRel.4

MGWRel.4

MGWRel.99

© Nokia Siemens Networks

5 (31)

Page 6: RANAP Document

Examples of RANAP Functions

2 Interface towards Radio Network

Two different protocols are used in the communication between the Core Network and the Radio Access Network:

BSSAP is the protocol of the A interface – used in the 2G GSM Network

RANAP is the protocol of the Iu-CS interface – used in the 3G UMTS Network

In this document, the focus will be RANAP as this is new signalling in 3G Release 4.

2.1 Base Station Subsystem Application Part (BSSAP)

The BSSAP protocol is used in the A interface to provide communication between the MSC Server and the Base Station Controller. In the CCS7 protocol stack, BSSAP is considered a SCCP user or SCCP subsystem. Normally, the connection between the BSC and the Core Network is done via E1/T1 links.

Those links contain channels for the user data traffic (voice or circuit-switched data) and normally, some timeslots are reserved for signalling traffic. In Release 4, the MGW is used as a signalling gateway to change the lower layers of signalling transport between the MSS and the BSC.

6 (31) © Nokia Siemens Networks

Page 7: RANAP Document

Examples of RANAP Functions

Figure 1 - Protocol stack of A interface signalling in Release 4

2.1.1 BSSAP Functions

BSSAP uses SCCP services from:

Basic Connection-Oriented Services (Service Class 2) – that represents the majority of messages between those network elements

Basic Connectionless Services (Service Class 0)

Figure 2 Functions of BSSAP

© Nokia Siemens Networks

7 (31)

Page 8: RANAP Document

Examples of RANAP Functions

Connection-Oriented messages

Any communication that comes directly from the mobile station is encapsulated in a BSSAP message as a DTAP “packet”. Requests from the MSS to the mobile station also use this transport. Examples:

- Update Location Request

- Service Request (Mobile-Originated Call, for instance)

- Authentication Request / Authentication Response

- Etc.

Each user procedure is identified between the MSS and BSC with a Connection ID that is handled by the SCCP stack. This is why those messages use the SCCP Connection-Oriented Services.

Connectionless messages

Some messages between the core network and the 2G Radio Network are not user-related. One example is the Reset message, when the BSC changes its administrative state to UNLOCKED in the MSS. Those messages use the Connectionless Services from the SCCP.

Paging messages are also connectionless, because, in a first moment, the Core Network is searching for the user and cannot establish a user data channel yet. Only when the user responds (Paging Response message), the virtual connection between the user and the MSS is established and the communication begins to use Connection-Oriented messages.

2.2 Radio Access Network Application Part (RANAP)

The overall protocol structure between the RNC and the Core Network (CN) is described in figures below. RANAP protocol (3G TS 25.413) is used between RNC and MSS. MGW.

The RANAP protocol is used in the Iu-CS interface to provide communication between the MSC Server and the Radio Network Controller. In the CCS7 protocol stack, RANAP is considered a SCCP user or SCCP subsystem. Normally, the connection between the RNC and the Core Network is done via ATM.

The ATM link contain virtual channels configured for user data traffic (voice or circuit-switched data). Virtual Channels are also configured for signalling traffic. In Release 4, the MGW is used as a signalling gateway

8 (31) © Nokia Siemens Networks

Page 9: RANAP Document

Examples of RANAP Functions

to change the lower layers of signalling transport between the MSS and the RNC.

Figure 3 Protocol stack of Iu-CS interface signalling in Release 4

2.2.1 RANAP Elementary Procedures

RANAP functions are implemented by one or several RANAP elementary procedures.

An Elementary Procedure (EP) consists of an initiating message and possibly aresponse message. Three kinds of EPs are used: class 1, class 2 and class 3.

2.2.1.1 Class 1 Elementary Procedures

Class 1 Elementary Procedures have a response (success and/or failure). For Class 1 EPs, the types of responses can be as follows:

Successful: A signalling message explicitly indicates that the elementary procedure completed successfully with receipt of response.

Unsuccessful: A signalling message explicitly indicates that the EP failed oron time supervision expiry (i.e. absence of expected response).

Successful and Unsuccessful: One signalling message reports both successful and unsuccessful outcome for the different included requests.

© Nokia Siemens Networks

9 (31)

Page 10: RANAP Document

Examples of RANAP Functions

Table 1. Class 1 Elementary Procedures

Elementary Procedure

Initiating Message

Successful Outcome Unsuccessful OutcomeResponse message Response message

Iu Release IU RELEASE COMMAND

IU RELEASE COMPLETE

Relocation Preparation

RELOCATION REQUIRED

RELOCATION COMMAND RELOCATION PREPARATION FAILURE

Relocation Resource Allocation

RELOCATION REQUEST

RELOCATION REQUEST ACKNOWLEDGE

RELOCATION FAILURE

Relocation Cancel

RELOCATION CANCEL

RELOCATION CANCEL ACKNOWLEDGE

Security Mode Control

SECURITY MODE COMMAND

SECURITY MODE COMPLETE

SECURITY MODE REJECT

Reset RESET RESET ACKNOWLEDGE

Reset Resource RESETRESOURCE

RESET RESOURCEACKNOWLEDGE

Location related Data

LOCATION RELATED DATA REQUEST

LOCATION RELATED DATA RESPONSE

LOCATION RELATED DATA FAILURE

2.2.1.2 Class 2 Elementary Procedures

Class 2 EPs are always considered successful.

Table 2. Class 2 Elementary Procedures

Elementary Procedure MessageRAB Release Request RAB RELEASE REQUESTIu Release Request IU RELEASE REQUESTRelocation Detect RELOCATION DETECTRelocation Complete RELOCATION COMPLETEPaging PAGINGCommon ID COMMON IDCN Invoke Trace CN INVOKE TRACELocation Reporting Control LOCATION REPORTING CONTROLLocation Report LOCATION REPORTInitial UE Message INITIAL UE MESSAGEDirect Transfer DIRECT TRANSFEROverload Control OVERLOADError Indication ERROR INDICATION

2.2.1.3 Class 3 Elementary Procedures

Class 3 EPs have one or several response messages reporting both successful/unsuccessful outcomes of requests and temporary status information about

10 (31) © Nokia Siemens Networks

Page 11: RANAP Document

Examples of RANAP Functions

requests. This type of EP only terminates through response(s) or EP timer expiry.

Table 3. Class 3 Elementary procedures

Elementary Procedure Initiating Message Response MessageRAB Assignment RAB ASSIGNMENT

REQUESTRAB ASSIGNMENT RESPONSE x N (N>=1)

2.3 Example of RAB Messages: RAB Assignment Request

Direction: CN --> RNC

17 © Nokia Siemens Networks Presentation / Author / Date / Document NumberFor public use – IPR applies

Example: RAB Assignment Request (1)Direction : CN RNC

IE/Group Name Presence Range IE type and reference

Semantics description

Criticality Assigned Criticality

Message Type M 9.2.1.1 YES reject RABs To Be Setup Or Modified List

O YES ignore

>RABs To Be Setup Or Modified Item IEs

1 to <maxnoofRABs>

>>First Setup Or Modify Item

M Grouping reason: same criticality

EACH reject

>>>RAB ID M 9.2.1.2 The same RAB ID must only be present in one group.

-

>>>NAS Synchronisation Indicator

O 9.2.3.18 -

>>>RAB Parameters

O 9.2.1.3 Includes all necessary parameters for RABs (both for MSC and SGSN) including QoS.

-

>>>User Plane Information

O -

>>>>User Plane Mode

M 9.2.1.18 -

>>>>UP Mode Versions

M 9.2.1.19 -

>>>Transport Layer Information

O -

>>>>Transport Layer Address

M 9.2.2.1 -

>>>>Iu Transport Association

M 9.2.2.2 -

>>>Service Handover

O 9.2.1.41 -

© Nokia Siemens Networks

11 (31)

Page 12: RANAP Document

Examples of RANAP Functions

18 © Nokia Siemens Networks Presentation / Author / Date / Document NumberFor public use – IPR applies

Example: RAB Assignment Request (2)Direction : CN RNC

>>Second Setup Or Modify Item

M Grouping reason: same criticality

EACH ignore

>>> PDP Type Information

O 9.2.1.40 -

>>>Data Volume Reporting Indication

O 9.2.1.17 -

>>>DL GTP-PDU Sequence Number

O 9.2.2.3 -

>>>UL GTP-PDU Sequence Number

O 9.2.2.4 -

>>>DL N-PDU Sequence Number

O 9.2.1.33 -

>>>UL N-PDU Sequence Number

O 9.2.1.34 -

>>>Alternative RAB Parameter Values

O 9.2.1.43 YES ignore

RABs To Be Released List

O YES ignore

>RABs To Be Released Item IEs

1 to <maxnoofRABs>

EACH ignore

>>RAB ID M 9.2.1.2 The same RAB ID must only be present in one group.

-

>>Cause M 9.2.1.4 -

19 © Nokia Siemens Networks Presentation / Author / Date / Document NumberFor public use – IPR applies

RANAP Message Content Explanation

•Abbreviation Used

•Criticality

Abbreviation Meaning M IEs marked as Mandatory (M) shall always be included in the

message. O IEs marked as Optional (O) may or may not be included in the

message. C IEs marked as Conditional (C) shall be included in a message only if

the condition is satisfied. Otherwise the IE shall not be included.

Abbreviation Meaning

– No criticality information is applied explicitly. YES Criticality information is applied. This is usable only for non-

repeatable IEs GLOBAL The IE and all its repetitions together have one common criticality

information. This is usable only for repeatable IEs. EACH Each repetition of the IE has its own criticality information. It is not

allowed to assign different criticality values to the repetitions. This is usable only for repeatable IEs.

12 (31) © Nokia Siemens Networks

Page 13: RANAP Document

Examples of RANAP Functions

3 Examples of RANAP Procedures

3.1 RANAP Messages in Location Update

RNC CN

Authentication and key generation

SECURITY MODE COMMAND

SECURITY MODE COMPLETE

INITIAL DIRECT TRANSFER(Location Update Request)

DIRECT TRANSFER(Location Update Accept)

RNCRNC CNCN

Authentication and key generation

SECURITY MODE COMMANDSECURITY MODE COMMAND

SECURITY MODE COMPLETESECURITY MODE COMPLETE

INITIAL DIRECT TRANSFER(Location Update Request)INITIAL DIRECT TRANSFER(Location Update Request)

DIRECT TRANSFER(Location Update Accept) DIRECT TRANSFER(Location Update Accept)

Figure 4 Location Update Procedure

A new SCCP connection is established when information related to the communication between UE and the network has to be exchanged between RNC and CN and no SCCP connection exits for the concerned UE. The SCCP signalling connection establishment is initiated by the RNC at the reception of the first layer 3 non access stratum message from the UE. The RNC sends SCCP CONNECTION REQUEST message to the CN. A RANAP INITIAL UE MESSAGE is included in the user data field of this SCCP message. L3 MM message LOCATION UPDATE REQUEST is included in RANAP INITIAL UE MESSAGE.

© Nokia Siemens Networks

13 (31)

Page 14: RANAP Document

Examples of RANAP Functions

3.1.1 Initial UE Message

The purpose of the Initial UE Message is to establish an Iu signallingconnection between a CN domain and the RNC and to transfer the initial NAS-PDU to the CN. When RNC receives from radio interface a NAS message to be forwarded to a CN domain for which an Iu signalling connection for the UE does not exist, RNC initiates the Initial UE Message procedure and sends the INITIAL UE MESSAGE to the CN. Main parameters in this message are:

CN domain indicator : CS or PS domain

LAI: MM within CN shall rely on this information

SAI

NAS-PDU

Iu signalling connection indicator: allocated by RNC

Global RNC-ID

3.1.2 Direct Transfer

The purpose of the Direct Transfer message is to carry UE - CN signallingmessages over the Iu Interface when signalling connection already exists. The UTRAN does not interrupt the UE – CN signalling messages (MM or CM messages). The UE - CN signalling messages are transported as aparameter in the DIRECT TRANSFER messages. The Direct Transfer message can be originated both CN or UTRAN. The use of the SAPI included in the DIRECT TRANSFER message from CN to RNC enables theUTRAN to provide specific service for the transport of the messages.

Main parameters in this message are: NAS-PDU

SAPI: in case of SMS SAPI=3 otherwise SAPI=0

3.1.3 Iu Release

The purpose of the Iu Release procedure is to enable the CN to release the Iuconnection and all UTRAN resources related to the Iu connection to be released. The following conditions can intitiate the Iu Release procedure:

14 (31) © Nokia Siemens Networks

Page 15: RANAP Document

Examples of RANAP Functions

Completion of transaction between UE and CN.

UTRAN generated reasons, i.e. reception of IU RELEASE REQUEST.

Completion of successful SRNS relocation.

Relocation cancellation upon successful completion of the Relocation Resource Allocation procedure.

The CN initiates the procedure by sending an IU RELEASE COMMANDmessage to the UTRAN. After the IU RELEASE COMMAND has been sent, the CN will not send further RANAP connection-oriented messages on this particular connection. Reception of an IU RELEASE COMPLETE message terminates the procedure in the CN. IU RELEASE COMMAND contains cause like normal release, successful relocation or release due UTRAN generated reasons.

© Nokia Siemens Networks

15 (31)

Page 16: RANAP Document

Examples of RANAP Functions

3.2 RANAP Messages in Call Setup

Figure 5 MOC call setup

16 (31) © Nokia Siemens Networks

Page 17: RANAP Document

Examples of RANAP Functions

Figure 6 Clearing the call

3.2.1 Location Reporting Control

The purpose of the Location Reporting Control procedure is to allow the CN torequest information on the location of a given UE. The CN initiates the procedure by generating a LOCATION REPORTING CONTROL message. The Request Type IE instructs the serving RNC to report on the change of Service Area or report directly geographical area. In addition to other possible location reporting requests for e.g. geographical coordinates, the Multimedia Gateway rel99 initiates the

© Nokia Siemens Networks

17 (31)

Page 18: RANAP Document

Examples of RANAP Functions

Location Reporting Control procedure after every successful SCCP connection establishment. The RNC is called upon to report on the change of Service Area.

The LOCATION REPORT message serves as a response for theLOCATION REPORTING CONTROL message. This information is used forcharging and provides statistics. If the RNC is unable to deliver the location information as requested by the CN, the RNC reports the UE location as 'Undetermined' by omitting the Area Identity IE. A cause value is added to provide an explanation for the undetermined location.

3.2.2 RAB (Radio Access Bearer) Assignment

The purpose of the RAB Assignment procedure is to enable modifications and/or releases of already established RABs and/or the establishment of new RABs for a given UE.

The CN initiates the procedure by sending a RAB ASSIGNMENT REQUESTMessage. The CN may request UTRAN to establish, modify or releaseone or several RABs with one RAB ASSIGNMENT REQUEST message.The message contains information required by the UTRAN for building the newRAB configuration.

UTRAN reports to CN in the first RAB ASSIGNMENT RESPONSE message the result for all the requested RABs.

Main parameters in RAB ASSIGNMENT REQUEST message are:

RAB ID: Equals to stream identifier at CC level

User plane mode

User plane mode version: MGW always uses version 1

Transport layer address: MGW AAL2 address

Iu transport association: Binding identifier between RANAP and AAL2

18 (31) © Nokia Siemens Networks

Page 19: RANAP Document

Examples of RANAP Functions

3.3 AAL type 2 Signalling Protocol

This signalling is to control the bearer between RNC and MGW (or MGW-MGW) using ATM as transport. AAL type 2 Signalling (AAL2SIG) is discussed more detail in AAL2SIG module.

3.3.1 Establish Request (ERQ)

ERQ message is used to establish AAL type 2 point-to-point connection between MGW and RNC.

Main parameters are:

Connection element Identifier (CEID) which has two parts: AAL2 Path Identifier and channel identifier (CID)

Destination NSAP/E164 service endpoint address (NSEA/ESEA)

Destination signalling association identifier (DAID)

Originating signalling association identifier (OSAID)

ALC link characteristics (ALC): contains max/average CPS-SDU bit rate and max/average CPS-SDU size

Served user generated reference (SUGR): Binding identifier

3.3.2 Establish Confirm (ECF)

ECF message is the response message for ERQ message including parameters Destination signalling association identifier and Originating signalling association identifier.

3.3.3 Release Request (REL)

REL message is used to release AAL type 2 point-to-point connection between MGW and RNC. The message includes Destination Signalling association identifier (DAID) and cause .

3.3.4 Release Confirm (RLC)

RLC is acknowledgement for REL message containing the Destination signalling association Identifier.

© Nokia Siemens Networks

19 (31)

Page 20: RANAP Document

Examples of RANAP Functions

4 Examples of RANAP Functions

The main functions of RANAP protocol towards CS domain are explained in the following chapters. It is assumed that MSC /CN Node in the pictures below is MSC server while role of MGW is of SGW.

4.1.1 Relocating Serving RNC

This function enables to change the serving RNC functionality as well as the related Iu resources (RAB(s) and Signalling connection) from one RNC to another.

UE Source RNC Target RNCMSC

1. Relocation Required2. Relocation Request

3. Relocation Request Acknowledge4. Relocation Command

6. "Handover Access"

8. Relocation Complete8. Iu Release Command

10. Iu Release Complete

7. Relocation Detect7. RRC procedures

Relocation Decision

5. RRC: "Handover Command"

Figure 7 Relocation

4.1.1.1 Relocation Preparation

The source RNC initiates the procedure by generating a RELOCATION

20 (31) © Nokia Siemens Networks

Page 21: RANAP Document

Examples of RANAP Functions

REQUIRED message. The source RNC determines whether to initiate intra-system Relocation or inter-system handover. In intra-system Relocation, thesource RNC indicates the source RNC's RNC-ID in the Source ID IE, and thetarget RNC's RNC-ID in the Target ID IE. In inter-system handover, the sourceRNC indicates the Service Area Identifier in the Source ID IE, and the cell global identity of the target system in the Target ID IE. The source RNC indicates the appropriate cause value for Relocation in the Cause IE. Typical cause values are "Time critical Relocation", "Resource optimisation" and "Relocation desirable for radio reasons".When preparation, including resource allocation in the target system, is complete and the CN has chosen to continue the relocation of SRNS, the CN will send a RELOCATION COMMAND message to the source RNC.

4.1.1.2 Relocation Resource Allocation

The purpose of the Relocation Resource Allocation procedure is to allocateresources from target RNC. The CN initiates the procedure by generating a RELOCATION REQUEST message. In UTRAN to UTRAN relocation, this message contains information required by the UTRAN to build the same RAB configuration as existed for the UE before relocation.When all necessary resources, including the initialized Iu user plane, for accepted RAB have been allocated, target RNC will send a RELOCATION REQUEST ACKNOWLEDGE message to CN.

4.1.1.3 Relocation Detect

The purpose of the Relocation Detect procedure is to signal detection of SRNSrelocation execution to the CN by the Target RNC. Target RNC sends a RELOCATION DETECT message to CN when a relocation execution trigger is received. Upon receipt of the RELOCATION DETECT message, CN switches the userplane from source RNC to target RNC.

4.1.1.4 Relocation Complete

The Relocation Complete procedure signals completion of SRNS relocation tothe CN by the Target RNC. When the new SRNC-ID + S-RNTI exchange successfully with the UE by radio protocols, the target RNC initiates the Relocation Complete procedure by sending a RELOCATION COMPLETE message to the CN.

© Nokia Siemens Networks

21 (31)

Page 22: RANAP Document

Examples of RANAP Functions

4.1.2 Overall RAB Management

This function is responsible for setting up, modifying and releasing RABs.

UTRANRNC

CN Node

MSC

n. RAB Assignment Response...

2. RAB Assignment Response (RABs setup or modified,

RABs released, RABs failed to setup or modify, RABsfailed to release, RABs queued)

1. RAB Assignment Request (RABs to be setup or modified,

RABs to be released) Radio &Iu setup

Radio &Iu setup,

Queued RABs

Figure 8 RAB Assignment

4.1.3 Requesting RAB Release

While the overall RAB management is a function of the CN, the RNC has the capability to request the release of RAB. The RNC initiates the procedure by generating a RAB RELEASE REQUEST message towards the CN. RABs to be released IE indicates the list of RABs requested to release. The Cause IE associated with each RAB indicate reason for the release.

Upon receipt of the RAB RELEASE REQUEST message, the CN initiates anappropriate release procedure for the identified RABs in the RAB RELEASEREQUEST message. It is up to the CN to react to the request.

22 (31) © Nokia Siemens Networks

Page 23: RANAP Document

Examples of RANAP Functions

CN Node

MSC

UTRANRNC

1. RAB Assignment Request (RABs to be released)2. RAB Assignment Response (RABs released)

Normal RAB Assignment (release)

1. RAB Release Request (RABs to be released)

Figure 9 RAB Release Request

4.1.4 Release all Iu Connection Resources

This function is used to explicitly release all resources related to one Iu connection.

CN Node

MSC

UTRANRNC

1. Iu Release Command (Cause)

2. Iu Release Complete

Release of allRadio and Iuresourcesfor that CNdomain

Figure 10 Iu Release

© Nokia Siemens Networks

23 (31)

Page 24: RANAP Document

Examples of RANAP Functions

4.1.5 Requesting the Release of all Iu Connection Resources

While the Iu release is managed from the CN, the RNC has the capability to request the release of all Iu connection resources from the corresponding Iu connection.

CN NodeMSC

1. Iu Release Request (Cause)

1. Iu Release Command2. Iu Release Complete

Normal Iu Release

Figure 11 Iu Release Request

4.1.6 Controlling Overload in the Iu Interface

This function allows adjusting the load in the Iu interface. The purpose of this procedure is to give a degree of signalling flow control. "Processor Overload" and "Overload in the Capability to Send Signalling Messages to the UE" are catered for at the UTRAN. "Processor Overload" is catered for at the CN.

The underlying philosophy is to stem traffic at source with known effect onservice. In Nokia implementation, steps are sequential (one step at atime).The CN sends an OVERLOAD message to two most burdening RNCs to indicate that it is in a congested state. The CN can send multiple OVERLOAD messages to further reduce traffic intensity or maintain a traffic level.Receipt of the message by UTRAN triggers reduction in traffic to the CN node,which sends the message.

24 (31) © Nokia Siemens Networks

Page 25: RANAP Document

Examples of RANAP Functions

If the UTRAN is unable to send signalling messages to the UE, due to overload, the UTRAN sends an OVERLOAD message to the CN. As the CN is unable todecrease overload in an overloaded UTRAN, O&M is informed.

UTRANRNC

CN NodeMSC

1. Overload (Number of Steps, CN domain ind.)

1. Overload (Number of Steps, Global RNC-ID, CN domain ind.)

Figure 12 Overload Control

4.1.7 Resetting the Iu

This function is used for resetting an Iu interface. The purpose of the Reset procedure is to initialise the UTRAN if the CN fails, and vice versa.

CN NodeMSC

1. Reset (Cause, CN Domain indicator, Global CN-ID)

2. Reset Acknowledge (CN Domain indicator, Global RNC-ID)

1. Reset (Cause, CN Domain indicator, Global RNC-ID)

2. Reset Acknowledge (CN Domain indicator, Global CN-ID)

© Nokia Siemens Networks

25 (31)

Page 26: RANAP Document

Examples of RANAP Functions

Figure 13 Reset

4.1.8 Sending the UE Common ID (Permanent NAS UE Identity) to RNC

This function makes the RNC aware of the UE's Common ID. The purpose of the Common ID procedure is to allow the RNC to create a reference between the user's permanent NAS UE Identity (IMSI) and RRC connection for UTRAN paging co-ordination. When the Iu signalling connection has been established and IMSI is available, the CN will send a COMMON ID message to the RNC. The RNC associates the permanent identity to that user's RRC Connection and saves it for the duration of the RRC connection.

CN NodeMSC

UTRANRNC

1. Common ID (Permanent NAS UE Identity)

Figure 14 Common Id

4.1.9 Paging the User

This function provides the CN for capability to page the UE.

26 (31) © Nokia Siemens Networks

Page 27: RANAP Document

Examples of RANAP Functions

CN Node

MSC

UTRANRNC

1. Paging (CN Domain Indicator, IMSI, TMSI, Paging Area ID

Paging Cause, Non Searching Indication)

Figure 15 Paging

4.1.10 Controlling the Tracing of UE Activity

This function allows setting the trace mode for a given UE.

CN Node

MSC

UTRANRNC

1. CN Invoke Trace (Trace Type, Trace Reference, Trigger ID, UE Identity, OMC ID)

Figure 16 Trace

4.1.11 Transport of NAS Information between UE and CN

This function has two sub-classes:

© Nokia Siemens Networks

27 (31)

Page 28: RANAP Document

Examples of RANAP Functions

1. Transport of the initial NAS signalling message from the UE to CN. This function transfers transparently the NAS information. As a consequence also the Iu signalling connection is set up.

2. Transport of NAS signalling messages between UE and CN, This function transfers transparently the NAS signalling messages on the existing Iu signalling connection. It also includes a specific service to handle signalling messages differently.

CN NodeMSC

UTRANRNC

1. Initial UE Message (CN Domain Id, LAI, SAI, NAS-PDU, Iu signalling conn. id, Global RNC-ID)

1. Direct Transfer (NAS-PDU, SAPI)

1. Direct Transfer (NAS-PDU, SAPI). . .

Figure 17 Transport of NAS Signalling

4.1.12 Controlling the Security Mode in the UTRAN

This function is used to send the security keys (ciphering and integrity protection) to the UTRAN, and setting the operation mode for security functions. The UTRAN uses this information to select and load the encryption device for user and signalling data with the appropriate parameters and to store the appropriate parameters for the integrity algorithm.

The CN starts the procedure by sending a SECURITY MODE COMMAND message to the UTRAN. This message specifies which ciphering, if any, andintegrity protection algorithms may be used by the UTRAN. Upon receipt of the SECURITY MODE COMMAND message, the UTRAN selects internally appropriate algorithms, taking into account UE/UTRAN capabilities. The UTRAN then triggers the execution of the

28 (31) © Nokia Siemens Networks

Page 29: RANAP Document

Examples of RANAP Functions

corresponding radio interface procedure and, if applicable, invokes the encryption device and startsthe integrity protection.

Upon successful completion of the radio interface procedure, UTRAN returns aSECURITY MODE COMPLETE message to the CN. This message includes the chosen integrity protection and encryption algorithms. The set of permitted algorithms specified in the SECURITY MODE COMMAND message remain applicable for subsequent RAB Assignments and Intra-UTRAN Relocations.

UTRANRNC

CN NodeMSC

1. Security Mode Command (Integrity Protection Info Encryption Info, Key status)

2. Security Mode Reject (Cause)Or

2. Security Mode Complete (Selected Algorithms, Criticality Diagnostics)

Figure 18 Security Mode Control

4.1.13 Controlling Location Reporting

Location Reporting Control function allows the CN to operate the mode in which the UTRAN reports the location of the UE. Location reporting function is used for transferring the actual location information from RNC to the CN.

© Nokia Siemens Networks

29 (31)

Page 30: RANAP Document

Examples of RANAP Functions

CN Node

MSC

UTRANRNC

UTRANRNC

1. Location Reporting Control (Request Type)

Event based Report

Direct Report

1. Location Report (Area Identity, Cause)

DetermineLocation (SA)

1. Location Report (Area Identity, Cause)

1. Location Report (Area Identity, Cause)

. . .

Event,DetermineLocation (SA)

Event,DetermineLocation (SA)

Figure 19 Location Reporting

4.1.14 Reporting General Error Situation

This function allows reporting of general error situations. If errors in an incoming message cannot be reported by an appropriate failure message, a node initiates the Error Indication procedure to report the errors.

CN Node

MSC

UTRANRNC

1. Error Indication (Cause, Criticality Diagnostics, CN Domain Ind., Global CN-ID )

1. Error Indication (Cause, Criticality Diagnostics, CN Domain Ind, Global RNC-ID )

30 (31) © Nokia Siemens Networks

Page 31: RANAP Document

Examples of RANAP Functions

Figure 20 Error Indication

© Nokia Siemens Networks

31 (31)