e1 1 umts signaling flow

UMTS Signaling Flow

ZTE University

Content

UE State transitionSignaling flow

Classification of Flows

In terms of protocol stack, signaling flows can be access layer signaling flows or non-access layer signaling flows.

In terms of network composition, signaling flows can be categorized as circuit-switched or packet-switched.

Access layer and non-access layer signaling flows are actually so named from the perspective of protocol stack.

Classification of Flows

The flows at the access layer include PLMN selection, cell selection, and radio resource management flows.

The radio resource management flows are the flows at the RRC layer, including the RRC connection setup flow, flow of the signaling setup between UEs and CNs, RAB setup flow, call release flow, handover flow, and SRNS redirection flow.

UE Working Modes

There are two basic working modes: Idle

UE stands by without any service. There’s no connection between UE and UTRAN.

Connected UE transferred to the connected mode after accomplishing

RRC Connection Setup. UE has 4 states under the connected mode:Cell-DCH, Cell-

FACH, Cell-PCH, URA-PCH

UE State

UE States Under the Connected Mode

Cell-DCH UE is activated, and in service using its dedicated

channels. There are dedicated channels in both uplink and

downlink. UTRAN knows exactly which cell the UE is in.

Cell-FACH UE is activated, but without too much date to transmit,

so there’s no need to assign dedicated channels to it. Downlink data transmitted in FACH, while uplink in

RACH. UTRAN knows exactly which cell the UE is in.

UE States Under the Connected Mode

Cell-PCH There is no data transmitted in both uplink and downlink. UE needs to listen to PICH for paging information. UE works in discrete receiving, which saves the power effectively. UTRAN knows exactly which cell the UE is in. UE needs to do cell update procedure when it passes cells.

URA-PCH There is no data transmitted in both uplink and downlink. UE needs to listen to PICH for paging information and receive

discretely. UTRAN only knows which URA (UTRAN Registration Area) UE

exists. UE updates its location information only when its URA changes,

which further reduces the signaling saves resource.

RRC State Transition (I)

After RRC Connection Setup, UE will transit to CELL_FACH or CELL_DCH.

CN indicates UE using dedicated channel (CELL_DCH) or common channel (CELL_FACH) according to the service request.

If there is no service right now, UE will be indicated into PCH mode or release RRC connection back to IDLE mode.

URA_PCH

CELL_DCH CELL_FACH

CELL_PCH

IDLE

DEAD

IDLE

DEAD

CELL_DCH CELL_FACH

IDLE

Sketch of RRC State Transition

—— Transit from IDLE Mode

URA_PCH

CELL_DCH

CELL_PCH

IDLE

DEAD

IDLE

DEAD

CELL_FACH

IDLE

RRC State Transition (II)

UE do not occupy dedicated channels In the mode of CELL_FACH.

UE receives downlink data through FACH(S-CCPCH).

UE transmits uplink data through RACH(PRACH).

——Transit from CELL_FACH Mode


URA_PCH

CELL_DCH CELL_FACH

CELL_PCH

IDLE

DEAD

IDLE

DEAD

CELL_DCH

IDLE

URA_PCH CELL_PCH

CELL_DCH

RRC State Transition (III)

UE transceives uplink and downlink data through dedicated channels (DPDCHs and DPCCHs).

During the time when there is no data transmitted, CN may indicate UE’s transiting to URA_PCH or CELL_PCH.

——Transit from CELL_DCH Mode


URA_PCH

CELL_DCH CELL_FACH

CELL_PCH

IDLE

DEAD

IDLE

DEAD

CELL_DCH

IDLE

CELL_DCH

URA_PCH CELL_PCH

CELL_FACH

——CELL_PCH 和 URA_PCH

RRC State Transition (IV)

UE has no activated uplink. Paging Information makes UE back to

CELL_FACH or CELL_DCH mode. In CELL_PCH, UE should transit to

CELL_FACH first to finish cell updating, and go back if no service request.

In URA_PCH, if URA changes, UE also transits to CELL_FACH to finish cell updating first before it goes back to URA_PCH.

System resource can be saved in these two modes.


Content

UE State transitionSignaling flow

Basic Conception (1)

RRC (Radio Resource Control) provides information transfer service to the NAS (Non

Access Stratum). responsible for controlling the configuration of UMTS

radio interface Layers 1 and 2. RRC Connection

A point to point bi directional connection between the RRC (Radio Resource Control) entities on the UE (User Equipment) and UTRAN (UMTS Terrestrial Radio Access Network).

The UE requires an RRC connection to access the services of the UMTS network.


RAB -Radio Access Bearer Identify the service the AS (Access Stratum) provides to

the NAS (Non Access Stratum) for transfer of user data between the UE (User Equipment) and the CN (Core Network).

RB -Radio Bearer The service provided by the Layer 2 for the transfer of

user data between UE (User Equipment) and UTRAN (UMTS Terrestrial Radio Access Network).


RL (Radio Link) RL is a logical association between single UE (User

Equipment) and a single UTRAN (UMTS Terrestrial Radio Access Network) access point.

Its physical realization comprises one or more radio bearer transmissions.

It is possible for a UMTS mobile to have many radio links established, when this occurs the mobile is said to be in a soft handover.

Sketch of the basic conceptions

UE Calling FlowPower on

Cell selection

Location Update

Idle Mode

RRCEstablish

NASEstablish

Hand OverCell/

URA update

Channelreconfiguration

RB/RAB Modification

RAB Establish

RRCRelease

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

UE in Idle Mode

What Information needed for UE?

（ 1 ） Strongest cell（ 2 ） Slot boundary（ 3 ） Frame boundary

（ 4 ） Primary SC（ 5 ） Information in broadcasts

channel

1st Step: Cell Selection and Slot Synchronization

…

DL Scrambling Code Rule218-1 DL Scrambling Codes in total

(0..262142)

The left 8192

Scrambling codes

are used for

compression mode

The left 8192

Scrambling codes

are used for

compression mode

#511 Scrambling Code Group

81768177

8191

8176 ： P-SC8177 ： S-SC…8191 ： S-SC


81608161

8175

8160 ：主扰码8161 ：辅扰码…8175 ：辅扰码


80648065

8079

8064 ：主扰码8065 ：辅扰码…8079 ：辅扰码

…


112113

127

8176 ： P-SC8177 ： S-SC…8191 ： S-SC


1617

31

16 ： P-SC17 ： S-SC…31 ： S-SC


01

15

0 ： P-SC1 ： S-SC…15 ： S-SC

#0 Scrambling Code Cluster

#63 Scrambling Code Cluster… …

2rd Step: Frame synchronization and Scrambling code-group

Scrambling-code identification

CPICH is predefine sequence Spreading Factor is 256

(Cch,256,0) Scrambling by P-scrambling

code UE identified through symbol-

by-symbol correlation over the primary P-CPICH with all the scrambling codes within the code group.

Obtain broadcast information in P-CCPCH

P-CCPCH contain the current SFN and system broadcast information

P-CCPCH SF=256 (Cch,256,1)

P-CCPCH scrambling by primary scrambling code

UE can use obtained primary scrambling code to descrambling the P-CCPCH and obtain the BCH information


Cell selection

Location

Update

Idle Mode

RRCEstablish

NASEstablish

Hand OverCell/

URA update


RB/RAB Modification

RAB Establish

RRCRelease

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

UE Initiate Random Access

Establish Dedicated RRC Connection

UE Node B SRNC

2.Allocate RNTIL1 and L2 Parameters

1. RRC Connection Request

5. ALCAP Establish and Synchronization

3. NBAP RL Setup Request

7. RRC Connection Setup Complete

6. RRC Connection Setup

4. NBAP RL Setup Response

RRC Connection Rejection

If the RNC determines that the RRC connection cannot be established (for example, due to insufficient resources), the RNC directly sends the UE an RRC CONNECTION REJECT message which contains the reason for the rejection of the RRC connection.

1. RRC Initial Direct Transfer

Establish Signaling Link with CN

UE SRNC CN

3. SCCP CC(Success)

2. RANAP Initial UE Message

SCCP Connect Request

3. SCCP CJ(Failure)

4. RRC Direct Transfer

5. RRC Direct Transfer

1.1 Send Authentication Info

4. Security Mode Command

5. Security Mode Complete

6. Security Mode Complete

3.Security Mode Control

Authentication and Security Mode

UE RNS MSC Server/VLR

1. Authentication Request

2. Authentication Response

HLR

2.1 Send Authentication Info Ack

CS Location Update Process

MAP Cancel Location ACK

MAP_Cancel_Location

Location Update Request

MAP Update Location

MAP_Insert _Subscriber_Data

MAP_Update _Location_ACKLocation Update Confirm ACK

TMSI_Allocation_Complete

UE RNS MSC Server/VLR PVLR HLR

MAP_Insert _Subscriber_Data_ACK

Release CN Signaling ConnectionRelease RB

Establish RRC ConnectionEstablish CN Signaling Connection

Authentication and Security Mode


Cell selection

RRCEstablish

NASEstablish

Hand OverCell/

URA update


RB/RAB Modification

RAB Establish

RRCRelease

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

Location Update

Idle Mode

UE Work Mode Transforming

CELL_DCH CELL_FACH

CELL_PCHURA_PCH

IDLE

DEAD

RRC connection

All the Status exist in UTRAN and UE, and transparent for CN

Network Selection (PLMN)Cell Camping

Probe paging channelCell Reselection

High level Signaling Triger (CN)

Dedicated ChannelRB Transport Service


Cell selection

Location Update

Idle Mode

RRC

Establish

NAS

Establish

Hand OverCell/

URA update


RB/RAB Modification

RAB

Establish

RRCRelease

Call

Initiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

Procedure of Call Initiate

Call Setup Flow

CN initiates a paging message to RNC. RNC judges the paging message from the CN and then sends a

paging message to the corresponding UE. If no RRC connection is available, UE will send a RRC connection

setup request message (RRC Connection Request) to RNC. RNC determines to set up a RRC connection according to the service

request and system resource occupation then sends a RRC connection setup message (RRC Connection Setup) to UE.

After signaling connection setup, the higher layer of UE (NAS) sends a service request message to CN through a directly transfer message.

CN sends a RAB assignment message (RAB Assignment Request) to the RNC to allocate resource for UE’s request.

3. NBAP RL Reconfigure Prepare

RAB Establish FlowUE Node B SRNC

1. RANAP RAB Assignment Request

4. NBAP RL Reconfigure Ready

MSC



6. NBAP RL Reconfigure Commit

7. RRC RB Setup

8. RRC RB Setup Complete

9. RANAP RAB Assignment Response

8. ISUP IAM

UE Initiate CallUE RNS MSC Called MSC

1. RRC establish

6. RRC DT(Call Proceeding)

3. RRC DT(CM Service Request)

2. CN signaling establish

4. Authentication and Security

5. RRC DT(Setup)

7. RAB establish

10. ISUP ACM11. RRC DT(Alert)

12. ISUP ANM13. RRC DT(Connect)

14. RRC DT(Connect ACK)

15. Conversation

9. CN bearer establish

UE Receiving Call

1. ISUP IAM

UE RNS Called MSC Calling MSC

4. RRC establish

8. RRC DT(Setup)

6. RRC DT(Paging Response)

5. CN signalling establish

7. Authentication and Security

9. RRC DT(Call Confirm)

10. RAB establish

2. Paging 3. Paging

11. RRC DT(Alerting)12. ISUP ACM

13. RRC DT(Connected)14. ISUP ANM

16. Conversation

15. RRC DT(Connect ACK)


Cell selection

Location Update

Idle Mode

RRCEstablish

NASEstablish

Hand OverCell/

URA update


RB/RAB Modification

RAB Establish

RRCRelease

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

Handover Category

Intra-system handover Softer handover, soft handover, hard handover Depending on the Ec/No of CPICH

Inter-system handover Between FDD and TDD

Handover with different system 2G/3G handover Compression mode

Softer/Soft Handover Gain and Costs

Softer/Soft Handover Gain: The optimal fast close loop power control (MS always keep connection with the

most powerful cell) Seamless handover, without RB interruption When MS moves to the edge of the cell, and could not obtain enough signal power,

it can obtain Macro diversity from multiple cells The UL signaling quality can be improved through obtaining Macro diversity when

Node B (Softer HO) and RNC (Soft HO) combine the receiving signal and lower the required Transport power of UE.

Softer/Soft Handover Costs: Additional Rake receiver channel on Node B Additional DL channelization code Additional DL power Additional Rake receiver channel on MS Additional transport link between Node B and RNC (RNC internal Soft Handover) Additional transport link between S-RNC and D-RNC (Soft handover between

RNCs)

Soft Handover Flow

UE NodeB(DRNS) DRNCNodeB

(SRNS)Measurement

report

RL creation requestRL setup request

Active set update command

SRNC

RL setup response RL setup response

Active set update completion

RL Deletion request

RL Deletion response

A

B

Hard Handover Flow

UE TargetNodeB SRNCOriginal

NodeB

Measurement report

RL setup request

Reconfiguration command

RL setup response

Reconfiguration completion

RL deletion request

RL deletion response


Cell selection

Location Update

Idle Mode

RRCEstablish

NASEstablish

Hand OverCell/

URA update


RB/RAB Modification

RAB Establish

RRCRelease

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

Forward Hard Handover

UE Source RNC CNTarget RNC

2. Uplink SignallingTransfer Indication

[new C-RNTI, D-RNTI,UL message]

1.CCCH: Cell Update

[Cell Update Cause,U-RNTI,Measured results on PRACH]

RRC-relayRRC

RNSAP RNSAP

4.DCCH: Cell Update Confirm

[S-RNTI, SRNC-ID, new S-RNTI, new SRNC-ID, new C-RNTI]

RRCRRC

5.DCCH: RNTI Reallocation CompleteRRCRRC

3. Serving RNC Relocation

SRNC Relocation

2. Relocation RequiredRANAP RANAP

RANAP RANAP

6. RelocationRequest Ack.

RANAP RANAP1. Relocation Required

UE Node B RNCSource

RNCTarget

MSC/SGSN SGSN/MSC

RANAP RANAP4. Relocation Request

RANAP RANAP3. Relocation Request

RANAP RANAP7. Relocation Request Ack.

RANAP RANAP9. Relocation Command

RANAP RANAP8. Relocation Command

RANAP RANAP

12. RelocationComplete

RANAP RANAP11. Relocation Complete

RNSAP RNSAP

10. RelocationCommit

RANAP13. Iu Release Command

RANAP

RANAP14. Iu Release Command

RANAP

5. ALCAP Iu DataTransport Bearer Setup

15. ALCAP Iu Data Transport Bearer Relelase

RANAP16. Iu Release Complete

RANAP

RANAP17. Iu Release Complete

RANAP


Cell selection

Location Update

Idle Mode

RRCEstablish

NASEstablish

Hand OverCell/

URA update

Channel

reconfiguration

RB/RAB

Modification

RAB Establish

RRCRelease

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

DCH-DCH Transport Channel Reconfiguration

UE Node BDrift RNS

Node BServing RNS

DriftRNC

ServingRNC

CN

RNSAP RNSAP5. Radio Link Reconfiguration

Ready

RRCRRC13. DCCH : Transport Channel Reconfiguration Complete

NBAPNBAP6. Radio Link Reconfiguration Ready

NBAPNBAP4. Radio Link Reconfiguration Ready

NBAPNBAP11. Radio Link Reconfiguration Commit

RNSAP RNSAP

9. Radio Link ReconfigurationCommit

NBAPNBAP10. Radio Link Reconfiguration Commit

RRCRRC12. DCCH : Transport Channel Reconfiguration

8. ALCAP Iub Data Transport Bearer Set-up

RNSAP RNSAP

1. Radio Link ReconfigurationPrepare

NBAPNBAP2. Radio Link Reconfiguration Prepare

NBAPNBAP3. Radio Link Reconfiguration Prepare

ALCAP Iur Bearer Set-up7. ALCAP Iub Data Transport Bearer Set-up

15. ALCAP Iub Data Transport Bearer Release

ALCAP Iur Bearer Release14. ALCAP Iub Data Transport Bearer Release

Cell-FACH to Cell-DCH State TransformUE Node B

Drift RNSDriftRNC

ServingRNC

6. NodeB-SRNC Data Transport Bearer Sync.

RNSAP RNSAP

1. Radio Link SetupRequest

Start TXdescription

NBAP NBAP2. Radio Link Setup

Request

RNSAP RNSAP

4. Radio Link SetupResponse

NBAP NBAP

3. Radio Link SetupResponse

Start RXdescription

Decision to switch toCell_DCH state

RRCRRC8. DCCH : Physical Channel Reconfiguration Complete

RRCRRC7. DCCH : Physical Channel Reconfiguration

ALCAP Iur Bearer Setup5. ALCAP Iub Bearer Setup

RNSAP RNSAP

9. Common Transp. ChannelResources Release Request

Cell-DCH to Cell-FACH Transform UE Node B DRNC SRNC

RNSAP 6. Radio Link Deletion Request

RNSAP

RNSAP RNSAP 9. Radio Link Deletion Response

3. ALCAP Iur bearer setup (if needed)

RRC 4. DCCH : Physical Channel Reconfiguration RRC

决定切换到 Cell_FACH状态

state

RRC 5. DCCH : Physical Channel Reconfiguration Complete RRC

NBAP 7. Radio Link Deletion Request

NBAP

NBAP NBAP 8. Radio Link Deletion Response

ALCAP Iur bearer release

RNSAP 1. Common Transp. Channel Resources

Initialization Request

RNSAP

RNSAP RNSAP

2. Common Transp. Channel Resources Initialization Response

10. ALCAP Iub bearer release

[C-RNTI, Primary CPICH Info [FDD], optional: Secondary CCPCH Info, PRACH Info]


Cell selection

Location Update

Idle Mode

RRCEstablish

NASEstablish

Hand OverCell/

URA update


RB/RAB Modification

RAB Establish

RRC

Release

CallInitiate

①

②

③

④ ⑤ ⑥

⑦

⑧

⑨

RAB Release Flow

RRC Connection Release

UE NodeB SRNC

1. RRC£ ºRRC CONNECTION RELEASE

2. RRC£ ºRRC CONNECTION RELEASE COMPLETE

3. RL DELETION4. RL DELETION RESPONSE

5. ALCAPÊ Í· Å5. ALCAP Release

Call setup flow (1)

Call setup flow (2)

Call setup flow (3)

Call setup flow (4)

Call setup flow (5)

Call setup flow (6)

e1 1 umts signaling flow

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