This document summarizes the signaling flow between a UE, RNC, and MSC server during the establishment and release of a circuit switched call. It involves the following key steps: 1. The UE sends an RRC Connection Request to the RNC to initiate a call, and the RNC forwards this to the MSC server. 2. The MSC server and RNC then perform authentication and security procedures with the UE. 3. Once authenticated, the call is established with radio bearer setup between the UE and RNC and exchange of call signaling messages between the UE and MSC server. 4. Upon call completion, signaling is exchanged to release the radio bearers and disconnect the call.

1. UE RNC
UTRA_Idle
RRC Connection Request
[CCCH] RRC
Initial UE ID = IMSI|TMSI+LAI,
Est.Cause = originating conversational call
Initial UE MessageRANAP
CN domain = cs, LAI, SAI, RNC-ID,
NAS-PDU = CM Service Request
call request (User)
RRC Connection Setup[CCCH] RRC
U-RNTI, C-RNTI, signalling radio bearer
RB1..RB4, TrCH configuration, PhCH
configuration, radio access capability
update requirementRRC Connection Setup Complete[DCCH] RRC
Initial Direct Transfer[DCCH] RRC
CN domain = cs, NAS-PDU = MM-
message: CM Service Request
CELL_DCH
UE
UE radio access capabilities
Direct TransferRANAP
SAPI=0, NAS-PDU =
Authentication Req.
Downlink Direct Transfer[DCCH] RRC
CN domain = cs, NAS-PDU =
MM-
message: Authentication Request
UplinkDirect Transfer[DCCH] RRC
CN domain = cs, NAS-PDU = MM-
message: Authentication Response LAI, SAI, NAS-PDU =
Authentication Resp.
Direct TransferRANAP
Security Mode Command
RANAP Security Mode Command
permitted UIA, IK,
permitted UEA, CK, …
selected UIA, selected UEA,
ciphering activation time, …
[DCCH] RRC
[DCCH] RRC Security Mode Complete
Security Mode CompleteRANAP
selected UIA, selected UEA
[DCCH] RRC Uplink Direct Transfer
CN domain = cs, NAS-PDU =
CC-message: Setup
RANAP Direct Transfer
LAI, SAI, NAS-PDU = Setup
RANAP Paging
CN domain = cs, LAI, IMSI,
TMSI, cause
[PCCH] RRC
UE-ID = TMSI|IMSI,
cause = terminating
conversation call|
terminating cause
unknown
UTRA_Idle
MSC Server
…
Paging Type 1
RNC

2. UE RNC
RRC Connection Request
[CCCH] RRC
CN domain = cs, LAI, SAI, RNC-ID,
NAS-PDU = Paging Response
RRC Connection
Setup Complete
Initial Direct Transfer[DCCH] RRC
CN domain = cs, NAS-PDU = MM
message: Paging Response
UE
UE radio access capabilities
Direct Transfer
Authentication Req.
Downlink Direct Transfer[DCCH] RRC
CN domain = cs, NAS-PDU =
MM-
message: Authentication Request
UplinkDirect Transfer[DCCH] RRC
LAI, SAI, NAS-PDU =
Authentication Resp.
Direct TransferRANAP
RANAPSecurity Mode Command
permitted UIA, IK,
permitted UEA, CK, …
selected UIA, selected UEA,
ciphering activation time, …
[DCCH] RRC
[DCCH] RRCSecurity Mode Complete
Security Mode Completeselected UIA, selected UEA
[DCCH] RRC
CN domain = cs,
NAS-PDU = CC-
message: Setup
RANAP Direct Transfer
LAI, SAI, NAS-PDU = Setup
Initial UE ID = IMSI|TMSI+LAI,
Est.Cause = Terminating
conversational call
U-RNTI, C-RNTI, signalling
radio bearer RB1..RB4,
TrCH configuration, PhCH
configuration, radio access
capability update requirement
[CCCH] RRC RRC Connection Setup
[DCCH] RRC
Initial UE MessageRANAP
RANAP
Security Mode Command
RANAP
Downlink Direct Transfer
MSC Server RNC
CELL_DCH
CN domain = cs, NAS-PDU
= MM-message: Authentication
Response

3. UE RNC
[DCCH] RRC
UE
RANAP
Uplink Direct Transfer[DCCH] RRC
CN domain = cs, NAS-PDU =
CC-message: Call Confirmed
LAI, SAI, NAS-PDU =
Call Confirmed
RANAP Direct Transfer
SAPI=0, NAS-PDU =
Call Proceeding
RANAP Direct Transfer
[DCCH] RRC
CN domain = cs, NAS-PDU = CC
-message: Call Proceeding
Downlink Direct Transfer
Radio Bearer Setup
RAB Assignment Request
RABSetupOrModifyItem
RAB Parameter
[DCCH] RRC
RRC state = CELL_DCH
, RAB to setup radio bearer to
setup, signalling radio bearer
, transport channels to add, physical
channel
Radio Bearer Setup Complete[DCCH] RRC
RAB Assignment
Response
successful setup
[DCCH] RRCRAB Assignment Request
RABSetupOrModifyItem
RAB Parameter [DCCH] RRC
Radio Bearer Setup
RAB Assignment ResponseRANAP
[DCCH] RRC
successful setup
Uplink Direct Transfer[DCCH] RRC
LAI, SAI, NAS-PDU = Alerting
Direct TransferRANAP
SAPI=0, NAS-PDU = Alerting
Direct TransferRANAP
CN domain = cs, NAS-PDU =
CC-message: Alerting
Downlink Direct Transfer[DCCH] RRC
Uplink Direct Transfer[DCCH] RRC
LAI, SAI, NAS-PDU = Connect
Direct TransferRANAP
SAPI=0, NAS-PDU = Connect
Direct TransferRANAP
CN domain = cs, NAS-PDU =
CC-message: Connect
Downlink Direct Transfer
[DCCH] RRC
MSC Server RNC
RRC state = CELL_DCH
, RAB to setup radio bearer to
setup, signalling radio bearer
, transport channels to add, physical
channel
Radio Bearer Setup Complete
CN domain = cs, NAS-PDU =
CC-message: Alerting
CN domain = cs, NAS-PDU =
CC-message: Connect

4. UE RNC UE
LAI, SAI, NAS-PDU =
Connection ACK
Direct TransferRANAP
SAPI=0, NAS-PDU = Connection ACK
Direct TransferRANAPCN domain = cs, NAS-PDU =
CC-message: Connection ACK
Uplinkdirect Transfer[DCCH] RRC
Downlink Direct Transfer
[DCCH] RRC
call active
LAI, SAI, NAS-PDU =
Disconnect
Direct TransferRANAP
SAPI=0, NAS-PDU = Disconnect
Direct TransferRANAPCN domain = cs, NAS-PDU =
CC-message: Disconnect
Uplinkdirect Transfer
[DCCH] RRC
[DCCH] RRC
Downlink Direct Transfer
CN domain = cs, NAS-PDU =
CC-message: Disconnect
LAI, SAI, NAS-PDU =
Release
Direct TransferRANAP
SAPI=0, NAS-PDU = Release
Direct TransferRANAP
CN domain = cs, NAS-PDU =
CC-message: Release
Down linkdirect Transfer
[DCCH] RRC
Uplink Direct Transfer
CN domain = cs, NAS-PDU =
CC-message: Release
LAI, SAI, NAS-PDU =
Release complete
Direct TransferRANAP
SAPI=0, NAS-PDU = Release completeDirect TransferRANAPCN domain = cs, NAS-PDU =
CC-message: Release complete
Uplinkdirect Transfer
[DCCH] RRC
Downlink Direct Transfer
[DCCH] RRC
Iu Release Command
cause = normal event
[DCCH] RRC
cause = normal event
[DCCH] RRC
RRC Connection Release Complete
Iu Release Complete
RRC Connection Release
RANAP
released RAB
Iu Release Command
[DCCH] RRC
cause = normal event
[DCCH] RRC
RRC Connection Release Complete
Iu Release Complete
RRC Connection Release
RANAP
released RAB
cause = normal event
RANAP
RANAP
LAI, SAI, NAS-PDU =
Connection ACK
[DCCH] RRC
UTRA_Idle UTRA_Idle
MSC Server RNC
CN domain = cs, NAS-PDU =
CC-message: Release complete