1. WCDMA RAN Protocols and Procedures Chapter 8 Iu Interface - RANAP Protocol
In this chapter we will look at the considerations that must be taken into account when planning a CDMA network.

2. Objectives of Chapter 8, Iu Interface - RANAP Protocol
After this chapter the participants will be able to:
Explain the Iu interface and the Radio Access Network Application Protocol (RANAP) protocol structure.
Explain the main functions and procedures of RANAP.

3. APPLICATION PART (RANAP)
RADIO ACCESS NETWORK
APPLICATION PART (RANAP)
PROTOCOL
---INTRODUCTION---

4. The Iu interface connects WCDMA RAN to the Core Network.
The Radio Access Network Application Part (RANAP) protocol is used over
the Iu interface
RANAP carries Non-Access Stratum (NAS) messages, which are relayed
between the CN nodes and the Ues.
The Iu interface is divided into two instances:
* the Iu Circuit Switched (CS) to connect WCDMA RAN to the MSC server
* the Iu Packet Switched (PS) to connect to the SGSN
The Iu interface is divided into:
* a control plane
* a user plane.

5. Iu-CS Interface (figure 8-1)
Physical Layer
RANAP
Iu UP protocol layer
RNL
TNL
TN User Plane
TN Control Plane
Control Plane
User Plane
ATM
SCCP
MTP3b Q Q
AAL2
NNI-SAAL

6. Iu-PS Interface (figure 8-2)
ATM
Physical Layer
RANAP
Iu UP protocol layer
RNL
TNL
TN User Plane
TN Control Plane
Control Plane
User Plane
SCCP
MTP3b
GTP-U
UDP IP
AAL5
NNI -SAAL

7. RANAP signaling over the lu interface (figure 8-3)
MSC/VLR
NAS-messages
MGW
RANAP
Iu UP Uu
Node B
(RBS 3000)
RNC
Iub
Iu UP
RANAP
SGSN
NAS-messages

8. APPLICATION PART (RANAP)
RADIO ACCESS NETWORK
APPLICATION PART (RANAP)
PROTOCOL
---RANAP PROTOCOL STACK---

9. 1. RANAP uses the SS7 over ATM protocol stack for signaling transport.
Signaling Connection Control Part (SCCP) are used to transmit RANAP
PDUs over the broadband MTP architecture:
(1) connection-oriented
For Dedicated control services: maintenance of an associated Iu signaling
connection for a specific UE (such as NAS messages ).
(2) connectionless services
For General control services : relate to the entire Iu interface instance
between an RNC and the CN (such as block and reset ).
For Notification services : relate to a single UE or all UE's in a specified
area (such as paging)

10. RANAP Protocol stack (figure 8-4)
SGSN
IuPS Uu
IuCS
Iub
SRNC
MSC
RANAP Signaling
RANAP
RANAP
SCCP SAP
SCCP SAP
SCCP
SCCP
MTP-3B
MTP-3B
NNI-SAAL
NNI-SAAL
Lower layer signaling
AAL5
AAL5
ATM
ATM
PHY
PHY

11. IU USER PLANE (UP)

12. 1. The Iu User Plane protocol is part of the Radio Network Layer.
2. The purpose of the User Plane protocol : to carry user data related to RABs
over the Iu interface.
3. The protocol supports two modes:
(1) Transparent Mode (TrM)
protocol does not perform any framing or control. For instance, the transfer
of GTP-U PDUs (packet data) could utilize the transparent mode of the Iu UP
protocol.

13. (2) Support Mode for Predefined SDU sizes (SMpSDU)
performs framing of the user data into segments of predefined size.
correspond to AMR speech frames, or derived from the data rate of a
CS data call.
control procedures for initialization and rate control are defined
functionality is specified for indicating the quality of the frame based, for
example, on CRC from the radio interface .

14. Iu UP protocol layer in transparent occurrence over Iu interface (figure 8-5)
UTRAN CN
RNL-SAP
Iu UP layer in
Iu UP layer in
transparent mode
transparent mode
Radio Interface
Protocols
TNL-SAP
TNL-SAP

15. Iu UP protocol layer in support mode occurrence over Iu interface (figure 8-6)
UTRAN CN
RNL-SAP
Iu UP layer in
Iu UP layer in
support mode
support mode
Support Mode
Support Mode
Functions
Functions
Radio Interface
Protocols
Transfer of Iu
UP protocol
frames
TNL-SAP
TNL-SAP

16. Transport Network Control Plane for Iu CS (figure 8-7)
SRNC
MGW
Iub Uu Q
MTP-3B
NNI-SAAL
AAL5
ATM
PHY Q
Lower layer signaling
Q Signaling
IuCS

17. Transport Network User Plane for Iu CS (figure 8-8)Uu
IuCS
Iub
SRNC
MGW
Iu UP
Iu UP
AAL2
AAL2
ATM
ATM
PHY
PHY

18. Transport Network User Plane for Iu PS (figure 8-9)Uu
IuPS
Iub
SRNC
SGSN
Signaling
GTP-U
GTP-U
UDP
UDP IP
Lower layer signaling IP
AAL5
AAL5
ATM
ATM
PHY
PHY
a GTP-U tunnel is set up by RANAP.
It only needs an identifier for the tunnel and the IP addresses for the RNC and SGSN.
Further on a GTP-U tunnel is set up between the SGSN and the GGSN.

19. Iu Connections between RNC and the Core Network (figure 8-10)
User Plane/AAL2
Q.AAL2
RNC
RANAP
MGW
MSC
User Plane/GTP-U
RANAP
SGSN

21. FUNCTIONS OF RANAP

22. 1. RANAP supports functionalities that are implemented by various RANAP
Elementary Procedures (EPs). Each function may require the execution of one
or more EPs.
2. Three kinds of EPs are used:
Class 1: EPs with response (success and/or failure)
Class 2: EPs without response
Class 3: EPs with possibility of multiple responses

23. 3. RANAP has the following functions:
Paging
This function provides the CN for capability to page the UE.
• Common ID management
IMSI of the UE is sent from the CN to WCDMA RAN .
• Transport of NAS information between UE and CN.
provides transparent transfer of UE-CN signaling messages that are not
interpreted by WCDMA RAN.

24. • Security mode control
used to send the security keys and the algorithms (ciphering and integrity
protection) to the WCDMA RAN, and setting the operation mode for security
functions.
• Radio Access Bearer (RAB) Management
responsible for setting up, modifying and releasing RABs.
• Iu Release
Releases all resources (control and user plane) from a given instance of Iu
related to the specified UE.

25. • Relocating Serving RNC (SRNC)
* handles both SRNS relocation (not implemented) and hard handover.
* In SRNC relocation the serving Radio Network Subsystems (RNS)
functionality is relocated from one RNS to another without changing the
radio resources and without interrupting the user data flow. Only when all
Radio Links are already in the same DRNC that is target for the relocation.
• Management of overload
Controls the overload of the Iu interface.
• Reset
used to reset the Iu interface in error situations.

26. • Location reporting
allows the CN to receive information on the location of the given UE.
Data volume reporting
responsible for reporting unsuccessfully transmitted data

27. Class 1 EPs with response (table 8-1)
Elementary
Procedure
Initial
Message
Successful outcome
Unsuccessful outcome
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
SRNS Context Transfer
SRNS CONTEXT REQUEST
SRNS CONTEXT RESPONSE
Security Mode Control
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
SECURITY MODE REJECT
Data Volume Report
DATA VOLUME REPORT REQUEST
DATA VOLUME REPORT
Reset
RESET
RESET ACKNOWLEDGE

28. Class 2 EPs without response (figure 8-2)
Elementary Procedure
Initial message
Iu Release Request
IU RELEASE REQUEST
Relocation Detect
RELOCATION DETECT
Relocation Complete
RELOCATION COMPLETE
Paging
PAGING
Common ID
COMMON ID
CN Invoke Trace
CN INVOKE TRACE
CN Deactivate Trace
CN DEACTIVATE TRACE
Location Reporting Control
LOCATION REPORTING CONTROL
Location Report
LOCATION REPORT
Initial UE Message
INITIAL UE MESSAGE
Direct Transfer
DIRECT TRANSFER
Overload Control
OVERLOAD
Error Indication
ERROR INDICATION

29. Class 3 EPs with possibility of multiple responses (figure 8-3)
Elementary procedure
Initial message
Response message
RAB Assignment
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE x N (N>=1)

30. Class 1 EPs: Class 2 EPs: Class 3 EPs: Iu Release RAB Release Request
Relocation Preparation
Relocation Resource Allocation
Relocation Cancel
SRNS Context Transfer
Security Mode Control
Data Volume Report
Reset
Reset Resource
RAB Release Request
Iu Release Request
Relocation Detect
Relocation Complete
SRNS Data Forwarding Initiation
SRNS Context Forwarding from Source RNC to CN
SRNS Context Forwarding to Target RNC from CN
Paging
Common ID
CN Invoke Trace
CN Deactivate Trace
Location Reporting Control
Location Report
Initial UE Message
Direct Transfer
Overload Control
Error Indication
Class 3 EPs:
RAB Assignment

31. RANAP PROCEDURES

32. RANAP Procedures for Mobile Terminated call
RNC CN
PAGING
Only for UE terminated
Signaling Connection Establishment
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

33. Paging
RNC CN
PAGING
Only for UE terminated
Signaling Connection Establishment
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE
When the paging is received by the UE, a RRC Connection Establishment is performed

34. Paging Paging is used by the CN to page a UE
This procedure uses connectionless signaling
The PAGING message includes:
Permanent NAS UE Identity (i.e. IMSI) for calculation of paging group and also for WCDMA RAN paging co-ordination.
* paging coordination means that if a Radio Resource Control (RRC) connection already exists for this UE, the radio-interface paging-message will be sent via this RRC connection instead of via the broadcast paging channel.
The DRX Cycle Length Coefficient (if available) may be included in the Paging message, which used for calculating the paging occasions for the UE.
Temporary UE ID (that is, the TMSI). Used over the paging channel. If TMSI is not included the RNC shall use the Permanent NAS UE Identity instead,
Paging Cause shall indicate the reason for sending the paging message.
Non Searching Indication.
If set to non-searching, the RNC does not need to do WCDMA RAN paging co-ordination.
Paging Area.
Can be the LAI, RAI and (if omitted) the whole RNC area.

35. Initial UE Message (figure 8-11)
RNC CN
PAGING
Only for UE terminated
Signaling Connection Establishment
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

36. Initial UE Message
The Initial UE Message procedure is used to establish an Iu signaling connection between a CN domain and the RNC.
This procedure uses connection oriented signaling.
The SRNC sends a SSCP Connect Request (CR) message to the CN. The SCCP Connection Request message carries the RANAP Initial UE message.
The Initial UE Message carries the NAS messages with the establishment cause, the UE identity and the current location, on cell level of the UE.
The SRNC receives confirmation that the signaling connection has been setup by a SCCP Connection Confirm (CC) message. The SCCP CC message may include a RANAP message, for example “Common Id”

37. Common ID (figure 8-11) RNC CN : PAGING Only for UE terminated
Signaling Connection Establishment
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

38. Common ID
The Common ID procedure informs the RNC about the permanent NAS UE Identity (i.e. IMSI).
This procedure uses connection oriented signaling.
The permanent NAS UE Identity is tied to the RRC connection and is used at Paging to check if an RRC connection already exists for this UE;
That is WCDMA RAN paging co-ordination.
The WCDMA RAN also needs the permanent NAS UE Identity from this message in order to be able to calculate the paging group in case of WCDMA RAN initiated paging.

39. Direct Transfer (figure 8-11)
RNC CN
PAGING
Only for UE terminated
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

40. Direct Transfer
The Direct Transfer procedure is used to transfer NAS information between the CN and the RNC or vice versa.
This procedure uses connection oriented signaling.
Besides NAS-PDU for the NAS information, this message also includes
SAPI for indicating the priority of the message. SAPI 0 for high priority and SAPI 3 for low priority (SMS). Only used downlink.
LAI + RAC. Needed in connection with Routing Area Update. Only used towards the PS domain.
In this specific case Direct Transfer is used for Authentication and Ciphering Request and Response.

41. Security Mode Control (figure 8-11)
RNC CN
PAGING
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

42. Security Mode Control
The Security Mode Control procedure is used by the CN to pass cipher and integrity protection information to the WCDMA RAN.
This procedure uses connection oriented signaling.
Messages
If WCDMA RAN can support the requested ciphering and integrity protection, the message SECURITY MODE COMPLETE is returned.
Otherwise the message SECURITY MODE REJECT with an appropriate cause value is returned.

43. Security Mode Control continued
In case a UE has RABs towards both the PS and CS CNs (not supported), the following is valid:
User data for RABs towards CS are ciphered with the ciphering key received from the CS domain.
User data for RABs towards PS are ciphered with the ciphering key received from the PS domain.
Signaling data is ciphered and integrity protected with the latest received keys.

44. RAB Assignment (figure 8-11)
RNC CN
PAGING
Only for UE terminated
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

45. RAB Assignment
The RAB Assignment procedure is used to establish one or more new RABs for a given UE and/or to modify or release already existing RABs.
This procedure uses connection oriented signaling.
The RAB Establishment consists of two parts:
Iu bearer setup between the CN and the SRNC.
Radio Bearer Setup between the UE and the SRNC.
The RAB ASSIGNMENT REQUEST message contains:
list of RABs to establish with their bearer characteristics
list of RABs to modify with their bearer characteristics
list of RABs to release

46. RAB Assignment continued
Upon reception of RAB ASSIGNMENT REQUEST, the WCDMA RAN executes the requested configuration. The result is reported to CN in one or more RAB(s)
ASSIGNMENT RESPONSE messages. The first of these messages contains:
successfully established RABs
successfully modified RABs
released RABs
RABs failed to establish, modify or release
queued RABs

47. RAB Assignment continued
The subsequent messages are used for reporting the outcome of the queued RABs. (The procedure is not completed until all RABs have been reported.)
The following outcomes are possible:
successfully established or modified
failed to establish or modify
failed to establish due to timer expiry

48. Some information elements (IEs) included in RAB Assignment Request
For RABs to be setup or modified:
IE name
Description
RAB ID
The identity of the RAB.
RAB parameters
Gives attributes for the RAB like: Bit rate, SDU size, Transfer Delay, Priority, Traffic Class.
Data Volume Reporting Indication
Indicates if unsuccessfully transmitted data shall be recorded and reported to CN.
User Plane Mode
Gives mode of operation for the user plane.
UP Mode Versions
Gives which user plane versions that are supported.
Transport Layer Address
Address information for the user plane.
Iu Transport Association
Associates the RAB to the user plane.
DL GTP-PDU Seq. No
These four IEs are used for preserving PDU sequence numbers at handover between GPRS and UMTS. The first two are also used to allow the CN to preserve the sequence numbers at re-establishment of an Iu-connection.
UL GTP-PDU Seq. No.
DL N-PDU Seq. No.
UL N-PDU Seq. No.

49. Some information elements (IEs) included in RAB Assignment Request
For RABs to be released:
IE name
Description
RAB ID
The identity of the RAB.
Cause
Gives the cause for the release.

50. Some information elements (IEs) included in RAB Assignment Response
For RABs to be setup or modified:
For RABs failed to setup or modified:
IE name
Description
RAB ID
The identity of the RAB.
Transport Layer Address
Address information for the user plane.
Iu Transport Association
Associates the RAB to the user plane.
IE name
Description
RAB ID
The identity of the RAB.
Cause
Gives the cause for the release.

51. Some information elements (IEs) included in RAB Assignment Response
For RABs released:
For RABs failed to release:
IE name
Description
RAB ID
The identity of the RAB.
Unsuccessfully Transmitted DL Data Volume
Data received from CN but not successfully sent to the UE.
Data Volume Reference
Indicates when the Data Volume was recorded.
DL GTP-PDU Seq. No.
To be preserved by the CN in case the Iu connection is re-established.
UL GTP-PDU Seq. No.
IE name
Description
RAB ID
The identity of the RAB.
Cause
Gives the cause for the release.

52. Some information elements (IEs) included in RAB Assignment Response
For RABs queued:
IE name
Description
RAB ID
The identity of the RAB.

53. Iu Release (figure 8-11) RNC CN : PAGING Only for UE terminated
INITIAL UE MESSAGE
COMMON ID
DIRECT TRANSFER
E.g. Authentication
SECURITY MODE COMMAND
SECURITY MODE COMPLETE
RAB ASSIGNMENT REQUEST
RAB ASSIGNMENT RESPONSE :
RAB ASSIGNMENT RESPONSE
IU RELEASE COMMAND
IU RELEASE COMPLETE

54. Iu Release (figure 8-12)
The Iu Release procedure is used to release an Iu connection and all WCDMA RAN resources related to that Iu connection.
This procedure uses connection oriented signaling.
Any RABs still existing for the UE will also be released.
RNC CN
”Iu Release Command”
”Iu Release Complete ”

55. Iu Release Request
This procedure is used by WCDMA RAN to ask the CN to initiate the release of an Iu connection.
This procedure uses connection oriented signalling.
The CN can follow the request and initiate the Iu Release procedure. It can, however, also choose to take some other action, including ignoring the request.
RNC CN
”Iu Release Request”