WCDMA UTRAN Interface and Signaling Procedure
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Objectives
Upon completion of this course, you will be able to:
Understand UTRAN interface and structure
Understand the definitions about UTRAN network elements
Understand UTRAN signaling procedure
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Contents
UTRAN Network Overview
Basic Concepts about UTRAN
UTRAN Signaling Procedure
Page3
Contents
UTRAN Network Overview
Basic Concepts about UTRAN
UTRAN Signaling Procedure
Page4
The Position of UTRAN in WCDMA Network
Page5
UMTS Construction
UTRAN UMTS Terrestrial Radio Access Network
CN Core Network
UE User Equipment
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UMTS Structure
Uu Interface
Uu Interface
Uu Interface
General Protocol Mode for UTRAN Terrestrial Interface
The structure is based on the principle that the layers and planes are logically independent of each other.
General Protocol Mode for UTRAN Terrestrial Interface
The structure is based on the principle that the layers and planes are logically independent of each other.
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RNL Control Plane Application Protocol
NBAP ：Node B Application Part
RANAP：Radio Access Network Application Part
RNSAP：Radio Network Subsystem Application Part
RRC ：Radio Resource Control
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Iu-CS Interface
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Iu-PS Interface
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Iub Interface
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Iur Interface
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Contents
UTRAN Network Overview
Basic Concepts about UTRAN
UTRAN Signaling Procedure
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SRNC/DRNC
SRNC and DRNC are on a per connection basis between a UE and the UTRAN
The SRNC handles the connection to one UE, and may borrow radio resources of a certain cell from the DRNC
Drift RNCs support the Serving RNC by providing radio resources
A UE in connection state has at least one and only one SRNC, but can has 0 or multiple DRNCs
CN
SRNC
DRNC
Iu
Iur
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CRNC
The CRNC owns the radio resources of a cell
Dynamical control of power for dedicated channels, within limits admitted by CRNC, is done by the SRNC.
Scheduling of data for dedicated channels is done by the SRNC, while for common channels it is done by the CRNC
Iub
Node B
Cell
Cell
Cell
Node B
...
Iu
CRNC
CN
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RAB, RB and RL
RAB
RB
RL
NodeB
RNC
CN
UE
UTRAN
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UE Working Modes and States
Idle mode
Connected mode
Cell_DCH
Cell_FACH
Cell_PCH
URA_PCH
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Idle Mode
The UE has no relation to UTRAN, only to CN. For data transfer, a signalling connection has to be established.
UE camps on a cell
It enables the UE to receive system information from the PLMN
When registered and if the UE wishes to establish an RRC connection, it can do this by initially accessing the network on the control channel of the cell on which it is camped
UE can receive "paging" message from control channels of the cell.
It enables the UE to receive cell broadcast services.
The idle mode tasks can be subdivided into three processes:
PLMN selection and reselection;
Cell selection and reselection;
Location registration.
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Connected Mode
When at least one signalling connection exists, the UE is in connected mode and there is normally an RRC connection between UE and UTRAN. The UE position can be known on different levels:
UTRAN Registration Area (URA) level
The UE position is known on URA level. The URA is a set of cells
Cell level
The UE position is known on cell level. Different transport channel types can be used for data transfer:
Common transport channels (RACH / FACH, DSCH, CPCH)
Dedicated transport channels (DCH)
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Connected Mode
When at least one signalling connection exists, the UE is in connected mode and there is normally an RRC connection between UE and UTRAN. The UE position can be known on different levels:
UTRAN Registration Area (URA) level
The UE position is known on URA level. The URA is a set of cells
Cell level
The UE position is known on cell level. Different transport channel types can be used for data transfer:
Common transport channels (RACH / FACH, DSCH, CPCH)
Dedicated transport channels (DCH)
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Connected Mode
Cell-DCH
In active state
Communicating via its dedicated channels
UTRAN knows which cell UE is in.
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Connected Mode
Cell-FACH
In active state
Few data to be transmitted both in uplink and in downlink. There is no need to allocate dedicated channel for this UE.
Downlink uses FACH and uplink uses RACH.
UE need to monitor the FACH for its relative information.
UTRAN knows which cell UE is in.
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Connected Mode
Cell-PCH
No data to be transmitted or received.
Monitor PICH, to receive its paging.
lower the power consumption of UE.
UTRAN knows which cell UE is in.
UTRAN have to update cell information of UE when UE roams to another cell
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Connected Mode
URA-PCH
No data to be transmitted or received.
Monitor PICH.
UTRAN only knows which URA (UTRAN Registration Area, which consists of multiple cells) that UE is in.
UTRAN updates UE information only after UE has roamed to other URA.
A better way to reduce the resource occupancy and signaling transmission
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UE States
CELL_DCH
CELL_FACH
CELL_PCH
URA_PCH
IDLE
DEAD
- Scanning networks (PLMN)
- ”Camp on” cell
- Monitor paging channel
- cell re-selection
- Dedicated Channel
- Radio bearers Transmission Services
- upper layer Signaling
trigger (CN)
- Reduce action，DTX，and save power
RRC connection
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RNTI - Radio Network Temporary Identifier
Five Types of RNTI exist
Serving RNC RNTI (S-RNTI)
Drift RNC RNTI (D-RNTI)
Cell RNTI (C-RNTI)
UTRAN RNTI (U-RNTI)
HS-DSCH RNTI (H-RNTI)
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Contents
UTRAN Network Overview
Basic Concepts about UTRAN
UTRAN Signaling Procedure
Page32
Contents
UTRAN Signaling Procedure
3.1 Cell Setup
3.2 System Information Broadcast
3.3 Paging
3.4 Call Process
3.5 Handover


Cell Setup
NBAP
NBAP
NBAP
NBAP
NBAP
NBAP
NBAP
NBAP
NBAP
NBAP
NCP: Resource Status Ind
NCP: Audit Req
NCP: Cell Setup Req
NCP: Cell Setup Rsp
RNC
NodeB
NCP: Audit Rsp
NBAP
NBAP
NCP: Comm TrCh Setup Req
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Contents
UTRAN Signaling Procedure
3.1 Cell Setup
3.2 System Information Broadcast
3.3 Paging
3.4 Call Process
3.5 Handover


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System Information Broadcast Flow
Page36
Introduction of System Information
MIB：
Contains PLMN tag and SB (scheduling information block) or the scheduling information for SIB (system info block)

SB1：
Contains scheduling information for SIB

SB2：
Contains scheduling information for SIB

SIB1：
Contains the system information for NAS and the timer/counter for UE

SIB2：
Contains the URA information

SIB3：
Contains the parameters for cell selection and cell re-selection
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Introduction of System Information
SIB4：
Contains parameters for cell selection and cell re-selection while UE is in connecting mode

SIB5：
Contains parameters for the common physical channels of the cell

SIB6：
Contains parameters for the common physical channels of the cell while UE is in connecting mode

SIB7：
Contains the uplink interference level and the refreshing timer for SIB7

SIB8：
Contains the CPCH static information
Page38
Introduction of System Information
SIB9：
Contains the CPCH dynamic information

SIB10：
Contains information to be used by UEs having their DCH controlled by a DRAC procedure
Used in FDD mode only
To be used in CELL_DCH state only
Changes so often, its decoding is controlled by a timer

SIB11：
Contains measurement controlling information

SIB12：
Contains measurement controlling information in connecting mode

SIB13：
Contains ANSI-41 system information
Page39
Introduction of System Information
SIB14:
Contains the information in TDD mode

SIB15:
Contains the position service information

SIB16:
Contains the needed pre-configuration information for handover from other RAT to UTRAN

SIB17:
Contains the configuration information for TDD

SIB18:
Contains the PLMN identities of the neighboring cells
To be used in shared networks to help with the cell reselection process
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System Information Block Type 1
System information type 1
The NAS system information
CS domain DRX：K ＝ 6，then DRX period is 2^k = 2 ^ 6 = 64 TTI = 640 ms
PS domain DRX：K ＝ 6，then DRX period is 2^k = 2 ^ 6 = 64 TTI = 640 ms
The different timers for UE in connecting mode and idle mode.
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System Information Block Type 2
System info type 2
URA information
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System Information Block Type 3
The references for cell selection and re-selection
Qhyst2s
Sintrasearch
Sintersearch
SinterRatsearch
Qqualmin
Qrxlemin
T reselection
Max Allowed UE TX power
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System Information Block Type 5
The configuration information for the following physical channels and the counterpart transport channels
PICH
AICH
PCCPCH
PRACH
SCCPCH
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System Information Block Type 7 and 11
System info type 7
Including the UL interference level which is used for open loop power control:
Preamble_Initial_Power=Primary CPICH DL TX power - CPICH_RSCP + UL interference + Constant Value
Including the Expiration Time Factor which is used for refreshing the SIB7 periodically
System info type 11
The neighbor cell information for cell re-selection in IDLE mode.
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Contents
UTRAN Signaling Procedure
3.1 Cell Setup
3.2 System Information Broadcast
3.3 Paging
3.4 Call Process
3.5 Handover


Page46
Paging Caused by CN
Page47
Paging Caused by CN
The paging information type which is sent by UTRAN is decided by UE mode.
If UE is in the CELL_FACH or CELL_DCH，UTRAN send paging type 2. In other modes, the paging information is type 1 and UE can use DTX method to detecting PICH.
Page48
Paging Caused by UTRAN
Page49
Contents
UTRAN Signaling Procedure
3.1 Cell Setup
3.2 System Information Broadcast
3.3 Paging
3.4 Call Process
3.5 Handover


Page50
Introduction of Call Process
In WCDMA system, a call process includes the following basic signaling flows:
RRC connection flow
Iu interface signaling flow
Authentication flow (optional)
Security flow (optional)
RAB establish flow
Call proceeding
NAS signaling before correlative bearer release
Correlative bearer release
RRC Connection Establishment Flow (DCH)
When UE is in IDLE mode and the NAS of UE request the signaling connection, UE will send a RRC Connection Request. Each UE only can have on RRC Connection. The main function is to configure the signaling channel of UTRAN.
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Iu Interface Signaling Connection Establish
In Iu interface, radio network layer reports the RANAP information and NAS information. NAS information is taken as directed message in RANAP information.
And the process of Iu signaling connection is to establish the Iu interface connection of SCCP between RNC and CN.
Node B
RNC
CN
RRC
RRC
Initial DT
Initial UE message (Connect Request)
Connect Confirm
RANAP
Transport Network
User Plane
Control Plane
SSCOP
AAL5
MTP3b
SCCP
SSCF-NNI
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Iu Interface Signaling Connection Establish
In Iu interface, radio network layer reports the RANAP information and NAS information. NAS information is taken as directed message in RANAP information.
And the process of Iu signaling connection is to establish the Iu interface connection of SCCP between RNC and CN.
Node B
RNC
CN
RRC
RRC
Initial DT
Initial UE message (Connect Request)
Connect Confirm
RANAP
Transport Network
User Plane
Control Plane
SSCOP
AAL5
MTP3b
SCCP
SSCF-NNI
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Authentication and Security Flow
UE
RNC
CN
Initial DT
Initial UE Message
DL DT (Authentication Request)
DL DT (Authentication Request)
DL DT (Authentication Request)
DL DT (Authentication Request)
Common ID
Security Mode Command
Security Mode Command
Security Mode Command
Security Mode Command
RAB Assignment
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Common ID
Page56
RAB Establishment Flow
NodeB
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NAS Signaling (CS)
UE Terminating Call
UE
MSC
CM Service Request
RRC and NAS signaling Connection Setup
Authentication Request
Authentication Response
Security Mode Command
Security Mode Command
RAB Assignment
Setup
Call Proceeding
Alerting
Connect
Connect ACK
Disconnect
Release
Release Complete
UE Outgoing Call
UE
MSC
Paging Response
Authentication Request
Authentication Response
Security Mode Command
Security Mode Command
RAB Assignment
Setup
Call Confirmed
Alerting
Connect
Connect ACK
Disconnect
Release
Release Complete
Paging
RRC and NAS signaling Connection Setup
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NAS Signaling (PS)
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UE to UE (1)
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UE to UE (2)
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UE to UE (4)
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UE to UE (5)
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UE to UE (6)
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UE to UE (7)
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UE to UE (8)
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Activate PDP Context from UE
Activate PDP Context from UE

Activate PDP Context from Network
Activate PDP Context from Network
Page70
Contents
UTRAN Signaling Procedure
3.1 Cell Setup
3.2 System Information Broadcast
3.3 Paging
3.4 Call Process
3.5 Handover


Page71
Concepts about Soft Handover
Soft handover: the signals from different NodeBs are merged in RNC.
Softer handover: the signals from different cells, but from the same NodeB are merged in NodeB.
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Soft Handover Flow
Core Network
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Merged in NodeB
Soft Handover Flow
Core Network
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Soft Handover Flow
Core Network
Page75
Soft Handover Flow (SRNC-DRNC)
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Soft Handover Flow (SRNC Relocation)
Node B
Serving RNC
RNC
Core Network
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Before Handover
After Handover
During Handover
Soft Handover Flow（Intra-RNC）
CN
CN
CN
Page78
Soft Handover Flow （Add Branch in RNC）
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Soft Handover Flow （Add Branch in RNC）
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Soft Handover Flow （Del Branch in RNC）
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Before Handover
After Handover
Radio Link can not exist simultaneously
Hard Handover (Intra-RNC)
CN
CN
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Hard Handover (Intra-RNC)
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Hard Handover (Intra-RNC)
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SRNC Relocation
SRNS

Core Network

Iu

DRNS

Iur

UE

RNS

Core Network

Iu

SRNS

UE

After SRNS Relocation

Before SRNS Relocation

Cells

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Hard Handover with Relocation (CS)
Page86
Inter-System Handover Flow（UMTS->GSM）
Page87
Inter-System Handover Flow (GSM-UMTS)
Page88
Forward Handover
Forward Handover is sponsored by UE, including cell update and URA update. URA update is only used to make the URA re-selection for the UE which is in URA_PCH state, and check the RRC connection.
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Summary
This chapter mainly explains the basic signaling flow in UTRAN. This is very helpful for the CN signaling flow.