umts signaling flow-62

1. UMTS Signaling Flow
ZTE University

2. Content
 UE State transition
 Signaling flow

3. 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.

4. 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.

5. 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

6. UE State

7. 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 data 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.

8. 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.

9. 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

10. 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
Sketch of RRC State Transition

11. 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
Sketch of RRC State Transition

12. 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.
Sketch of RRC State Transition

13. Content
 UE State transition
 Signaling flow

14. 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.

15. Basic Conception (2)
 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).

16. Basic Conception (3)
 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.

17. Sketch of the basic conceptions

18. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

19. UE in Idle Mode

20. What Information needed for UE?
（1） Strongest cell
（2） Slot boundary
（3）Frame
boundary
（4） Primary SC
（5） Information in broadcasts
channel

21. 1st Step: Cell Selection and Slot
Synchronization

22. …
DL Scrambling Code Rule
2
18
-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
8176
8177
8191
8176：P-SC
8177：S-SC
…
8191：S-SC
#510 Scrambling Code
Group
8160
8161
8175
8160：主扰码
8161：辅扰码
…
8175：辅扰码
#504 Scrambling Code
Group
8064
8065
8079
8064：主扰码
8065：辅扰码
…
8079：辅扰码
…
#7 Scrambling Code
Group
112
113
127
8176：P-SC
8177：S-SC
…
8191：S-SC
#1 Scrambling Code
Group
1
6
1
7
3
1
16：P-SC
17：S-SC
…
31：S-SC
#0 Scrambling Code
Group
0
1
1
5
0：P-SC
1：S-SC
…
15：S-SC
#0 Scrambling Code Cluster
#63 Scrambling Code Cluster
… …

23. 2rd Step: Frame synchronization and
Scrambling code-group

24. 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.

25. 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

26. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

27. UE Initiate Random Access

28. Establish Dedicated RRC Connection
UE Node B SRNC
2.Allocate RNTI
L1 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

29. 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.

30. 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

31. 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

32. CS Location Update Process
MAP Cancel Location
ACK
MAP_Cancel_Location
Location Update
Request
MAP Update Location
MAP_Insert _Subscriber_Data
MAP_Update _Location_ACK
Location Update
Confirm ACK
TMSI_Allocation_Complete
UE RNS MSC Server/VLR PVLR HLR
MAP_Insert _Subscriber_Data_ACK
Release CN
Signaling Connection
Release RB
Establish RRC Connection
Establish CN Signaling Connection
Authentication and Security Mode

33. UE Calling Flow
Power on
Cell selection
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨
Location
Update
Idle Mode

34. 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
channel
Cell Reselection
High level
Signaling
Triger (CN)
Dedicated
Channel
RB Transport
Service

35. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

36. Procedure of Call Initiate

37. 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.

38. 3. NBAP RL Reconfigure
Prepare
RAB Establish Flow
UE Node B SRNC
1. RANAP RAB
Assignment Request
4. NBAP RL Reconfigure
Ready
MSC
2. ALCAP Establish and Synchronization
5. ALCAP Establish and Synchronization
6. NBAP RL Reconfigure
Commit
7. RRC RB Setup
8. RRC RB Setup Complete
9. RANAP RAB
Assignment Response

39. 8. ISUP IAM
UE Initiate Call
UE 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. ISUPACM
11. RRC DT(Alert)
12. ISUPANM
13. RRC DT(Connect)
14. RRC DT(Connect ACK)
15. Conversation
9. CN bearer establish

40. 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. ISUPACM
13. RRC DT(Connected)
14. ISUPANM
16. Conversation
15. RRC DT(Connect ACK)

41. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

42. 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

43. 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)

44. Soft Handover Flow
UE
NodeB
(DRNS)
DRNC
NodeB
(SRNS)
Measurement
report
RL creation request
RL 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

45. Hard Handover Flow
UE
Target
NodeB SRNC
Original
NodeB
Measurement report
RL setup request
Reconfiguration command
RL setup response
Reconfiguration completion
RL deletion request
RL deletion response

46. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

47. Forward Hard Handover
UE Source RNC CNTarget RNC
2. Uplink Signalling
Transfer 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 Complete
RRCRRC
3. Serving RNC Relocation

48. SRNC Relocation
2. Relocation Required
RANAP RANAP
RANAP RANAP
6. Relocation
Request Ack.
RANAP RANAP
1. Relocation Required
UE Node B RNC
Source
RNC
Target
MSC/SGSN SGSN/MSC
RANAP RANAP
4. Relocation Request
RANAP RANAP3. Relocation Request
RANAP RANAP
7. Relocation Request Ack.
RANAP RANAP
9. Relocation Command
RANAP RANAP
8. Relocation Command
RANAP RANAP
12. Relocation
Complete
RANAP RANAP
11. Relocation Complete
RNSAP RNSAP
10. Relocation
Commit
RANAP
13. Iu Release Command
RANAP
RANAP
14. Iu Release Command
RANAP
5. ALCAP Iu Data
Transport Bearer Setup
15. ALCAP Iu Data Transport Bearer Relelase
RANAP
16. Iu Release Complete
RANAP
RANAP
17. Iu Release Complete
RANAP

49. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

50. DCH-DCH Transport Channel
Reconfiguration
UE Node B
Drift RNS
Node B
Serving RNS
Drift
RNC
Serving
RNC
CN
RNSAP RNSAP
5. Radio Link Reconfiguration
Ready
RRCRRC
13. DCCH : Transport Channel Reconfiguration Complete
NBAPNBAP
6. Radio Link Reconfiguration Ready
NBAPNBAP
4. Radio Link Reconfiguration Ready
NBAPNBAP
11. Radio Link Reconfiguration Commit
RNSAP RNSAP
9. Radio Link Reconfiguration
Commit
NBAPNBAP
10. Radio Link Reconfiguration Commit
RRCRRC
12. DCCH : Transport Channel Reconfiguration
8. ALCAP Iub Data Transport Bearer Set-up
RNSAP RNSAP
1. Radio Link Reconfiguration
Prepare
NBAPNBAP
2. Radio Link Reconfiguration Prepare
NBAPNBAP
3. 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

51. Cell-FACH to Cell-DCH State Transform
UE Node B
Drift RNS
Drift
RNC
Serving
RNC
6. NodeB-SRNC Data Transport Bearer Sync.
RNSAP RNSAP
1. Radio Link Setup
Request
Start TX
description
NBAP NBAP
2. Radio Link Setup
Request
RNSAP RNSAP
4. Radio Link Setup
Response
NBAP NBAP
3. Radio Link Setup
Response
Start RX
description
Decision to switch to
Cell_DCH state
RRCRRC
8. DCCH : Physical Channel Reconfiguration Complete
RRCRRC
7. DCCH : Physical Channel Reconfiguration
ALCAP Iur Bearer Setup5. ALCAP Iub Bearer Setup
RNSAP RNSAP
9. Common Transp. Channel
Resources Release Request

52. Cell-DCH to Cell-FACH Transform
UE Node B DRNC SRNC
RNSAP
6. Radio Link Deletion Request
RNSAP
RNSAPRNSAP
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 ReconfigurationComplete
RRC
NBAP
7. Radio Link Deletion Request
NBAP
NBAPNBAP
8. Radio Link Deletion Response
ALCAP Iur bearer release
RNSAP
1. Common Transp. ChannelResources
Initialization Request
RNSAP
RNSAPRNSAP
2. Common Transp. Channel Resources
Initialization Response
10. ALCAP Iub bearer release
[C-RNTI, Primary CPICH Info [FDD],
optional: Secondary CCPCH Info, PRACHInfo]

53. UE Calling Flow
Power on
Cell selection
Location
Update
Idle Mode
RRC
Establish
NAS
Establish
Hand Over
Cell/
URA update
Channel
reconfiguration
RB/RAB
Modification
RAB
Establish
RRC
Release
Call
Initiate
①
②
③
④ ⑤ ⑥
⑦
⑧
⑨

54. RAB Release Flow

55. RRC Connection Release
UE NodeB SRNC
1. RRC£ ºRRC CONNECTION RELEASE
2. RRC£ ºRRC CONNECTION RELEASECOMPLETE
3. RL DELETION
4. RL DELETION RESPONSE
5. ALCAPÊ Í· Å5. ALCAP Release

56. Call setup flow (1)

57. Call setup flow (2)

58. Call setup flow (3)

59. Call setup flow (4)

60. Call setup flow (5)

61. Call setup flow (6)