Ps call flow

Introduction
• This slide set provides a detailed illustration
of the message flow observed for an PS
call
• The message flow is focused upon
communication with the packet switched
core and does not include communication
with the circuit switched core.
• The UE starts by searching for candidate
cells by correlating the RSSI with the code
defining the primary SCH
• The UE then achieves radio frame
synchronisation and reads the BCCH logical
channel
• The BCCH provides system information
including the cell selection criteria
• If the cell passes the cell selection criteria
then the UE establishes an RRC connection
ad registers with the core network
• Having registered the UE activates the PDP
context with the CN using the existing CN
(assumption is that follow on request
pending is set)
• In case of no activity (no data nor
signalling data transmitted between the UE
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

Protocol Stacks
• Communication between the UE, RNC and packet
core makes use of
• Uu interface protocol stack
• Iub interface protocol stack
• Iu,ps interface protocol stack
Iub Iu,ps
Uu
Node B RNC SGSN

PS Radio Interface Control Plane
• The radio interface protocol control plane allows RRC signalling
between the RNC and UE
• RRC signalling is communicated across the Iub using the Iub
user plane protocol stack i.e. using Frame protocol and AAL2
based ATM
• Acknowledged or unacknowledged mode RLC is used between
the UE and RNC
WCDMA
L1
RRC
WCDMA
L1
AAL2
FP
ATM
Phy
MAC
RLC-C
AAL2
FP
ATM
Phy
MAC
RLC-C
UE
No de B
RNC
Uu Iub
RRC

PS User Plane
• The SGSN provides connectivity to the packet switched core
and applications
• Acknowledged mode RLC (or unacknowledged) is used between
the UE and RNC
• AAL2 based ATM is used to transfer user plane data across
the Iub and AAL5 based ATM across Iu,ps interface
WCDMA
L1
WCDMA
L1
AAL2
FP
ATM
Phy
MAC
RLC-U
AAL2
FP
ATM
Phy
MAC
RLC-U
AAL5
ATM
Phy
GTP-U
AAL5
ATM
Phy
UE
No de B
RNC SGSN
Uu Iub Iu,ps
UDP
IP
GTP-U
UDP
IP

Cell Search
• The UE keeps a record of the previously
used carrier. The cell search procedure
starts by scanning this carrier
• The cell search procedure is completed by
correlating RSSI against the known Primary
SCH code
• Peaks in the correlation result indicate the
presence of a cell as well as the multipath
associated with the propagation channel to
that cell
Correlation
Peaks
time
Correlation
result
• Once the UE has identified a cell the UE
attempts to synchronise with that cell
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

Radio Frame Synchronisation
Cp Cp Cp
Cs1 Cs1Cs2
Primary SCH
Secondary SCH
Primary CCPCH
256
chips
2560 - 256
chips
Slot 1 Slot 2 Slot 15 Slot 1
• The UE completes the three step radio frame
synchronisation process
• Step 1: Primary SCH identification and slot
synchronisation (completed during cell
search)
• Step 2: Code group identification and frame
synchronisation using the Secondary SCH
• Step 3: Scrambling code identification using
the CPICH
• Having completed these three steps the UE is
able to decode the Primary CCPCH -> BCH ->
BCCH
Primary CPICH
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

Read BCCH
• The BCCH encapsulates the System
Information message which includes the
Master Information Block (MIB), Scheduling
Blocks (SB) and System Information Blocks
(SIB)
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

Cell Selection
• Cell selection is standardised by 3GPP
within TS 25.304
• Cell selection is based upon the S-criteria
• UE extracts the S-criteria parameters
from SIB 3
• QqualMin
• QrxlevMin
• UE_TXPWR_MAX_RACH
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

Register with the Core Network
• The UE registers with the PS core
domain (the UE also registers with the
CS core domain but this slide set
concerns only the PS domain)
• PS domain registering is a GPRS attach
procedure
• Registering is achieved by establishing an
RRC connection and sending non-access
stratum messages to the 3G SGSN
• RRC Connection Establishment
• GPRS Attach
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

UTRAN Specific Signalling Protocols
3G-MSC/VLR
3G-SGSN
UE Node B
RNC
RNC
RNS
RNS
RRC
Iur: RNSAP
Iu-PS: RANAP
Iu-CS: RANAP
Iub: NBAP

RRC: RRC Connection Request (RACH)
UE RNC
Node B
• If the cell from which the BCCH has been read is suitable
to camp upon then the UE follows the instructions in SIB1
to complete a GPRS attach with the PS core network
• UE must first establish an RRC connection
• The RRC Connection Request message is sent to the RNC
using unacknowledged mode RLC on the RACH
• The message is sent via the Node B which uses Frame
Protocol to encapsulate the transport blocks and send
them across the Iub via AAL2 based ATM
RRC Connection Request

• The RNC replies to the UE s original’ RRC Connection Request
message with an RRC Connection Setup message
• The RRC Connection Setup message is sent to the UE on the FACH
using unacknowledged mode RLC
UE RNC
Node B
NBAP: Radio Link Setup Request
NBAP: Radio Link Setup Response
ALCAP: Establish Request
RRC Connection Setup
ALCAP: Establish Confirm
FP: Downlink Sync
FP: Uplink Sync
RRC: RRC Connection Setup (FACH)

• UE transmits the RRC Connection Setup Complete message
using SRB 2 on the newly established DCH
UE RNC
Node B
RRC Connection Setup Complete
FP: Downlink Sync
FP: Uplink Sync
NBAP: Synchronisation Indication
L1 Synchronisation
RRC: RRC Connection Setup Complete (DCH)

GPRS Attach Request
RRC Connection Request (RACH)
RRC Connection Setup (FACH)
RRC Connection Setup Complete (DCH)
Initial Direct Transfer: GPRS Attach Request (DCH)
UE RNC SGSNNode B
• The UE has now established a dedicated communication link with
UTRAN and is in a position to send a message to the core
network (PS core in this case)
• The UE uses an uplink RRC: Initial Direct Transfer message to
encapsulate and send a GPRS MM : Attach Request message to
the RNC
• The Node B extracts the RRC: Initial Direct Transfer message
and encapsulates it within a DCH Frame Protocol frame
• The RNC extracts the Attach Request message and
encapsulates it within a RANAP: Initial UE Message message
prior to forwarding it to the SGSN
Initial UE message : GPRS Attach Request
SCCP: Connection Request
• The RANAP: Initial UE Message
message is accompanied with a
message which is used to
establish the Iu-PS connection

Connection Confirm
SCCP: Connection Confirm
• The SCCP layer of the Iu-PS protocol stack responds
to the Connection Request message with a Connection
Confirm message
• The link is specified as being connection orientated
UE RNC SGSNNode B

Direct Transfer: Authentication and Ciphering Request
Authentication and Ciphering Request
• Having received the Attach Request message the PS core
responds with an Authentication and Ciphering Request message
• The Authentication and Ciphering Request message is sent to
the RNC encapsulated within a RANAP Direct Transfer message
• The RNC extracts the Authentication and Ciphering Request
message and encapsulates it within an RRC Downlink Direct
Transfer message
• The RNC then encapsulates the RRC Downlink Direct Transfer
message within a downlink Frame Protocol data frame prior to
forwarding it to the Node B
• The Node B extracts the RRC Downlink Direct Transfer
message and forwards it to the UE
Downlink Direct Transfer: Authentication and Ciphering Request (DCH)
UE RNC SGSNNode B

Authentication and Ciphering
Response
Uplink Direct Transfer: Authenication and Ciphering Response (DCH)
• Having received the Authentication and Ciphering Request
message the UE responds with an Authentication and Ciphering
Response message
• The Authentication and Ciphering Response message is sent to
the Node B encapsulated within an RRC Uplink Direct Transfer
message
• The Node B encapsulates the RRC Uplink Direct Transfer
message within an uplink Frame Protocol data frame prior to
forwarding it to the RNC
• The RNC extracts the Authentication and Ciphering Response
message and encapsulates it within a RANAP Direct Transfer
message prior to forwarding it to the PS core
Direct Transfer: Authentication and Ciphering Response
Direct Transfer: Authentication and Ciphering RequestDownlink Direct Transfer: Authentication and Ciphering Request (DCH)
UE RNC SGSNNode B

Security Mode Command
RANAP: Security Mode Command
• The PS core sends a Security Mode Command message to the
UE
• The purpose of this procedure is to trigger the start or
stop of ciphering or to command the restart of the
ciphering with a new ciphering configuration, for the radio
bearers of one core network domain and for all signalling
bearers
• It is also used to start integrity protection or to modify
the integrity protection configuration for all signalling radio
bearers
Security Mode Command (DCH)
UE RNC SGSNNode B
Uplink Direct Transfer: Authenication and Ciphering Response (DCH) Direct Transfer: Authentication and Ciphering Response

Security Mode Complete
UE RNC SGSNNode B
Secuirty Mode Complete (DCH)
• The UE responds to the Security Mode Command message
with a Security Mode Complete message
Security Mode CommandSecurity Mode Command (DCH)

Common Id
• The purpose of the Common ID procedure is to inform the RNC
about the permanent NAS UE Identity (i.e. IMSI) of a user
• This is used by the RNC e.g. to create a reference between the
permanent NAS UE identity of the user and the RRC connection
of that user for UTRAN paging co-ordination
UE RNC SGSNNode B
Common ID

Identity Request
• The PS core may request the UE to provide its identity. This is
done using the Identity Request message
• The PS core sends the Identity Request message encapsulated
within a RANAP: Direct Transfer message
• The RNC sends the Identity Request message encapsulated within
a RRC: Downlink Direct Transfer message
Direct Transfer: Identity RequestDownlink Direct Transfer: Identity Request (DCH)
UE RNC SGSNNode B
Common ID

Identity Response
Uplink Direct Transfer: Identity Response (DCH)
• The UE sends the Identity Response message encapsulated within
a RRC: Uplink Direct Transfer message
• The RNC sends the Identity Response message encapsulated
within a RANAP: Direct Transfer message
Direct Transfer: Identity RequestDownlink Direct Transfer: Common ID (DCH)
UE RNC SGSNNode B
Common ID
Direct Transfer: Identity Response

Attach Accept
• The PS core responds to the Attach Request with a Attach
Accept message
• The Attach Accept is sent to the RNC encapsulated within a
RANAP: Direct Transfer message
• The RNC extracts the Attach Accept message and encapsulates
it within an RRC: Downlink Direct Transfer message
Direct Transfer: Attach Accept
UE RNC SGSNNode B
Common ID
Downlink Direct Transfer: Location Attach Accept (DCH)

Attach Complete
• The UE core responds to the Attach Accept with a Attach
Complete message in case there is new P-TMSI allocated by the
SGSN (sent in Attach Accept)
• The RNC extracts the Attach Complete message and
encapsulates it within a RANAP: Direct Transfer message
• The Attach Complete is sent to the RNC encapsulated within
RRC: Uplink Direct Transfer message
UE RNC SGSNNode B
Common ID
Direct Transfer: Attach CompleteUplink Direct Transfer: Attach Complete (DCH)

Summary of GPRS Attach
FP: Downlink Sync
FP: Uplink Sync
UE RNC SGSNNode B
Common ID
Direct Transfer: Attach CompleteUplink Direct Transfer: Attach Complete (DCH)
L1 Synchronisation

PS Call UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call
• The PS call can be either mobile originated or
mobile terminated
• The following slides present a mobile
originated call
• The first step is to establish an RRC
connection, however if the follow on“
request is SET in NAS Message GPRS” – ‘
Attach Request -> there is no Iu release as’
CN is waiting for additional signalling using the
same RRC (e.g. PDP context Activation)
• This means that RRC Connections for PS calls
are initiated with cause : registration

ActivatePDPContext Request
UE RNC SGSNNode B
Uplink Direct Transfer : Activate PDP context request (DCH)
• Having attached with the PS Core NW, UE sends
Activate PDP context request DCCH ->DCH -> DPCH
• By sending this message UE requests a service for the packet switched
connection establishment
• DCCH contains the RRC: Uplink Direct Transfer
message
• Message is sent using acknowledged mode RLC
Direct Transfer : Activate PDP context request
GPRS Attach

NAS– Message: ActivatePDPContext Request
IEI Information Element Type/Reference Presence Format Length
Protocol discriminator Protocol discriminator
10.2
M V 1/2
Transaction identifier Transaction identifier
10.3.2
M V 1/2– 3/2
Activate PDP context request
message identity
Message type
10.4
M V 1
Requested NSAPI Network service access point identifier
10.5.6.2
M V 1
Requested LLC SAPI LLC service access point identifier
10.5.6.9
M V 1
Requested QoS Quality of service
10.5.6.5
M LV 12
Requested PDP address Packet data protocol address
10.5.6.4
M LV 3 - 19
28 Access point name Access point name
10.5.6.1
O TLV 3 - 102
27 Protocol configuration options Protocol configuration options
10.5.6.3
O TLV 3 - 253

RAB Assignment Request
UE RNC SGSNNode B
Uplink Direct Transfer : Activate PDP context request (DCH) Direct Transfer : Activate PDP context request
• Having received the Activate PDP Context Request message
the PS core sends the RANAP: RAB Assignment Resuest
message to the RNC
• The RANAP: RAB Assignment Resuest message requests the RNC
to establish a RAB with a specified set of QoS parameters
• The PS core requests these QoS parameters based upon the
subscription and the service being requested (as seen from
Activate PDP Context Request message the QoS is based
entirely on the subscription)
GPRS Attach

Radio Bearer Setup
UE RNC SGSNNode B
RANAP: RAB Assignment Request
RRC: Radio Bearer Setup
• Once the RANAP: RAB Assignment Request message
has been received from PS CN and RNC has
resources to setup the RB the RNC sends a RRC:
Radio Bearer Setup message to the UE
GPRS Attach

Example: RB Setup for UL: 64 DL: 64 PSconnection
Higher layer RAB/Signalling RB RAB
RLC Logical channel type DTCH
RLC mode AM
Payload sizes, bit 320
Max data rate, bps 64 000
AMD PDU header, bit 16
MAC MAC header, bit 0
MAC multiplexing N/A
Layer 1 TrCH type DCH
TB sizes, bit 336
TFS TF0, bits 0x336
TF1, bits 1x336
TF2, bits 2x336
TF3, bits 3x336
TF4, bits 4x336
TTI, ms 20
Coding type TC
CRC, bit 16
Max number of bits/TTI after channel coding 4 236
Uplink: Max number of bits/radio frame before rate matching 2 118
RM attribute 130 to 170

Radio Bearer Setup Complete
UE RNC SGSNNode B
• The UE acknowledges the RRC: Radio Bearer Setup
message with a RRC: Radio Bearer Setup Complete
message
GPRS Attach

RAB Assignment Response
UE RNC SGSNNode B
• Once the radio bearer establishment has been
acknowledged, the RNC indicates to the PS core
that the RAB has been established using the RANAP:
RAB Assignment Response message
GPRS Attach

Measurement Control
UE RNC SGSNNode B
Measurement Control
• Once the RAB has been established the RNC sends a
measurement control messages
•For traffic volume measurements (UE internal)
•For intra and inter frequency measurements
• Prior to receiving this message, the UE uses the measurement
control information from the SIBs (inter and intra freq.
Measurements traffic volume measurements are not–
performed prior to measurement control)
• Measurement control defines the reporting thresholds for
Measurement Control
GPRS Attach

ActivatePDPContext Accept
UE RNC SGSNNode B
• Once the radio access bearer establishment has been
acknowledged, (measurement control messages can be sent
before or after the Activate PDP Context Accept) the PS
CN indicates to the UE that the PDP Context Ativation has
been successfully established using the RANAP: Activate PDP
Context Accept message
• RNC receives the Direct Transfer : Activate PDP Context
Accept message and forwards it as Downlink Direct
Transfer : Activate PDP Context Accept message to the UE
Direct Transfer: Activate PDP Context AcceptDownlink Direct Transfer : Activate PDP Context Accept (DCH)
Measurement Control
Measurement Control
GPRS Attach

64kbpsUL & DL Connection Established
UE RNC SGSNNode B
• UL: 64 DL: 64 kbps PS data call Established
Call Established
Measurement Control
Measurement Control
GPRS Attach

Reporting Event 4a
UE RNC SGSNNode B
Packet Call Established
Measurement Control
Measurement Control
Measurement Report : e4a
• Once the UE determines that an event 4a has occurred it
sends a measurement report to the RNC. This is done using
the RRC: Measurement Report message
• As instructed, the UE sends measurement report when the
RLC buffer absolute payload exceeds the threshold
• The measurement identity reflects that provided within the
measurement control message
GPRS Attach

Radio Link Reconfigure Prepare
UE RNC SGSNNode B
• Assuming that the admission control procedure within
the RNC decides to accept the capacity request from
UE, the RNC prepares to reconfigure the radio link at
the Node B by sending the NBAP: Radio Link Reconfigure
Prepare message
NBAP: Radio Link Reconfigure Prepare
Call Established
Measurement Control
Measurement Control
GPRS Attach

Radio Link Reconfigure Ready
• The Node B responds to the NBAP: Radio Link
Reconfigure Prepare message with a NBAP: Radio Link
Reconfigure Ready message
UE RNC SGSNNode B
Call Established
Measurement Control
Measurement Control
GPRS Attach

AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
Measurement Control
Measurement Control
FP: Downlink Sync
FP: Uplink Sync
Radio Link Reconfiguration Commit
• Once the transmission resouce allocations have been
configured the RNC sends a NBAP: Radio Link
Reconfiguration Commit message to the Node B
GPRS Attach

AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
Measurement Control
Measurement Control
FP: Downlink Sync
FP: Uplink Sync
Radio Bearer Reconfiguration
• Once the reconfiguration of radio link at Node-B is
done the RNC sends a RRC: RRC: Radio Bearer
Reconfiguration message to UE
RRC: Radio Bearer Reconfiguration (DCH)
GPRS Attach

AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
Measurement Control
Measurement Control
FP: Downlink Sync
FP: Uplink Sync
Complete
• The UE acknowledges the RRC: Radio Bearer
Reconfiguration message with a RRC: Radio Bearer
Reconfiguration Complete message
RRC: Radio Bearer Reconfiguration Complete (DCH)
GPRS Attach

AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
Measurement Control
Measurement Control
FP: Downlink Sync
FP: Uplink Sync
UL: 64kbps DL: 128/384 kbps Connection
Established
GPRS Attach

Cell State Transitions
• When the RNC notices that there is
nothing being transmitted between UE
and RNC, inactivity timers will start to
run and in case of expiry of those
timers the UE is moved to use common
channels i.e. cell state transition from
Cell_DCH to Cell_FACH occurs
• In order to save some UE battery
power (as in Cell_FACH the UE has to
read FACH channel all the time) in case
of further in activity i.e. no capacity
requests from UE nor RNC the UE is
further moved to Cell_PCH where the UE
only listens PCH (paging channel)
UE is
powered up
Read BCCH
Cell selection
Register with
core network
Cell State
Transitions
Radio frame
synchronisation
Cell search
Originating PS
Call

AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
FP: Downlink Sync
FP: Uplink Sync
Measurement Control
Data Flow
• In case the RNC decides to move the UE to Cell_FACH state it
sends RRC: Radio Bearer Reconfiguration
GPRS Attach

Complete
• The UE acknowledges the RRC: Radio Bearer
Reconfiguration message with a RRC: Radio Bearer
Reconfiguration Complete message on RACH
AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
FP: Downlink Sync
FP: Uplink Sync
Measurement Control
Data Flow
RRC: Radio Bearer Reconfiguration Complete (RACH)
GPRS Attach

Measurement Control
• RNC sends RRC: Measurement Control message to the UE
to setup the UE traffic volume measurements for the
UE capacity requests (e4a)
Measurement Control (FACH)
AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
FP: Downlink Sync
FP: Uplink Sync
Measurement Control
Data Flow
GPRS Attach

Radio Link Deletion Request
• RNC sends NBAP: Radio Link Deletion Request message to
the BTS to delete the dedicated resources from the BTS
for the UE moved to the Cell_FACH
AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
FP: Downlink Sync
FP: Uplink Sync
Measurement Control
Data Flow
NBAP: Radio Link Deletion Request
GPRS Attach

Radio Link Deletion Response
AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
Call Established
FP: Downlink Sync
FP: Uplink Sync
Measurement Control
Data Flow
NBAP: Radio Link Deletion Response
GPRS Attach

UE in Cell_FACH
AAL2SIG:ECF
AAL2SIG:ERQ
UE RNC SGSNNode B
GPRS Attach
Call Established
FP: Downlink Sync
FP: Uplink Sync
Measurement Control
Data Flow
ALCAP: Release Request
ALCAP: Release Confirm
UE in Cell_FACH, PDP Context Active and GPRS Attached

Physical Channel Reconfiguration
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
RRC: Physical Channel Reconfiguration (FACH)
RRC: Physical Channel Reconfiguration Complete (RACH)
• RNC sends RRC: Physical Channel Reconfiguration message
to the UE to move the UE to Cell_PCH state

UE in Cell_PCH
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
UE in Cell_PCH, PDP Context Active and GPRS Attached

Cell Update
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
RRC: Cell Update (RACH)
• In case the UE has something to send it has to send
RRC: Cell Update message to the RNC to move the UE to
Cell_FACH state to get dedicated resources

Cell Update Confirm
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
• RNC acknowledges the UE message RRC: Cell Update with
RRC: Cell Update Confirm message and instructs UE to
move to Cell_FACH state
RRC: Cell Update Confirm (FACH)

Utran Mobility Information Confirm
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
• UE acknowledges the RNC message RRC: Cell Update
Confirm and the parameters given to UE in that message
with RRC: Utran Mobility Information Confirm message
RRC: Utran Mobility Information Confirm (RACH)

Measurement Control
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
• Measurement Control message for Traffic Volume
Measurement reporting is sent to UE
RRC: Measurement Control (FACH)

Radio Link Setup & Establishment
RequestUE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
AAL2SIG:ECF
AAL2SIG:ERQ
NBAP: Radio Link Setup
FP: Downlink Sync
FP: Uplink Sync
As explained
earlier: this
time just set
up 64/64

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
AAL2SIG:ECF
AAL2SIG:ERQ
FP: Downlink Sync
FP: Uplink Sync
As explained
earlier: this
time just set
up 64/64

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
AAL2SIG:ECF
AAL2SIG:ERQ
FP: Downlink Sync
FP: Uplink Sync
RRC: Radio Bearer Reconfiguration (FACH)
• The UE
acknowledges the
RRC: Radio Bearer
Reconfiguration
message with a
RRC: Radio Bearer
Reconfiguration
Complete
message
Complete

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
AAL2SIG:ECF
AAL2SIG:ERQ
FP: Downlink Sync
FP: Uplink Sync
• The UE
acknowledges the
RRC: Radio Bearer
Reconfiguration
message with a
RRC: Radio Bearer
Reconfiguration
Complete
message
Measurement Control
Measurement Control
Measurement Control
Measurement
Control for intra-
frequency
measurements and
stopping traffic

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
UE in Cell_DCH, PDP Context Active and GPRS Attached
Deactivate PDP Context Request
UpLink Direct Transfer : Deactivate PDP Context Request (DCH) Direct Transfer : Deactivate PDP Context Request (DCH)
• The UE requests deactivation of PDP context by
sending the Deactivate PDP Context Request
towards the PS core encapsulated within RRC:
Uplink Direct Transfer

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
Deactivate PDP Context Accept
UpLink Direct Transfer : Deactivate PDP Context Request (DCH) Direct Transfer : Deactivate PDP Context Request
Direct Transfer : Deactivate PDP Context AcceptDownlink Direct Transfer : Deactivate PDP Context Accept (DCH)
• The PS CN acknowledges the deactivation of PDP
context by sending Deactivate PDP Context
Accept to the UE encapsulated within RRC:
Downlink Direct Transfer

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
• The PS CN sends the RAB modification (release)
request to the RNC by RANAP: RAB Assignment
Request

RANAP: RAB Assignment Response
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
• The RNC acknowledges the RAB modification
(release) and sends RANAP: RAB Assignment
Response to the PS CN

Radio Link Reconfiguration Prepare
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
NBAP: Radio Link Reconfiguration Prepare
• The RNC starts RB modifications by sending
modification information to the BTS NBAP: Radio
Link Reconfiguration Prepare

Radio Link Reconfiguration Ready
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
NBAP: Radio Link Reconfiguration Ready
• The BTS acknowledges the RB modifications by
sending NBAP: Radio Link Reconfiguration Ready

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
NBAP: Radio Link Reconfiguration Commit
• After receiving successful response from BTS
the RNC orders BTS to take the modifications
into use by sending NBAP: Radio Link
Reconfiguration Commit

Radio Bearer Release
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
RRC: Radio Bearer Release (DCH)
• Then the RNC is ready to inform the UE about
the changes in the RB by sending RRC: Radio
Bearer Release

Radio Bearer Release Complete
UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
RRC: Radio Bearer Release (DCH)
• Then the RNC is ready to inform the UE about the
changes in the RB by sending RRC: Radio Bearer Release
• After this there is only signalling link active between
the UE and PS CN and the UE can be moved to
Cell_FACH and to Cell_PCH still maintaining the signalling
link or the signalling link can be deactivated by doing
GPRS detach or by releasing the RRC connection (and
RRC: Radio Bearer Release Complete (DCH)

UE GPRS Attached and PDP Deactivated in
Cell_PCH (I)
• In case the UE is GPRS Attached and in Cell_PCH state
the UE needs to send RRC: Cell Update message
indicating UL capacity request after that the PDP
Context activation procedure as above where the
messaging is as explained earlier
• Then PDP Context is activated using common channels,
RAB and RB setup
• UE internal measurements are activated and in case UE
has something to send in addition to just activating
PDP Context
• In case UE sends Measurement Report for event 4a
the dedicated resources are setup with radio bearer
reconfiguration
•This is also reconfiguration from Cell_FACH to Cell_DCH

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
UE in Cell_PCH, GPRS Attached
RRC : Cell Update (RACH)
RRC : Cell Update Confirm (FACH)
UpLink Direct Transfer : Activate PDP Context Request (RACH) Direct Transfer : Activate PDP Context Request
Direct Transfer : Activate PDP Context AcceptDownlink Direct Transfer : Activate PDP Context Accept (FACH)
RRC : Utran Mobility Information Confirm (RACH)
RANAP : RAB Assignment Request
RANAP : RAB Assignment Response
RRC : Radio Bearer Setup (FACH)
RRC : Radio Bearer Setup Complete (RACH)
RRC : Measurement Control (FACH)
RRC : Measurement Control (FACH)
RRC : Measurement Report (E4a) (RACH)
NBAP : Radio Link Setup
NBAP : Radio Link Setup Response
NBAP : Radio Link Synchronisation
RRC : Measurement Control (DCH)
RRC : Measurement Control (DCH)
UE GPRS Attached and PDP Deactivated in Cell_PCH (II)

UE GPRS attached and PDP Deactivated in Idle Mode
(I)
• In case the UE has deactivated PDP
Context and is moved to idle mode (still
attached) the UE must initiate RRC
Connection Setup procedure before it can
request new PDP context activation
• The RNC has to re-establish the Iu
resources for the UE by CM service
request

UE RNC SGSNNode B
GPRS Attach
Call Established
Data Flow
UE in idle, GPRS Attached, PDP Context Deactive
RRC : RRC Connection request (RACH)
RRC : RRC Connection Setup (FACH)
Initial UE Message : GPRS Service Request
RRC : RRC Connection Setup Complete (DCH)
NBAP : Radio Link Setup
NBAP : Radio Link Setup Response
NBAP : Radio Link Synchronisation
Initial Direct Transfer : GPRS Service Request (DCH)
Security Mode Complete (DCH)
Security Mode Command
RANAP: Direct Transfer : GPRS Activate PDP Context AcceptRRC: Downlink Direct Transfer : GPRS Activate PDP Context Accept (DCH)
RANAP: Direct Transfer : GPRS P-TMSI Reallocation CompleteRRC: Uplink Direct Transfer : GPRS P-TMSI Reallocation Complete (DCH)
RANAP: RAB Assignment RequestRRC: Radio Bearer Setup (DCH)
RRC : Radio Bearer Setup Complete (DCH)
RANAP :RAB Assignment Response
RRC: Measurement Control (DCH)
RRC : Measurement Report (e4a) (DCH)
NBAP : Radio Link Reconfiguration Prepare
NBAP : Radio Link Reconfiguration Ready
NBAP : Radio Link Reconfiguration Commit
RRC : Radio Bearer Reconfiguration Complete (DCH)
UE GPRS Attached and PDP Deactivated in Idle Mode (I)
RRC: Uplink Direct Transfer: GPRS Activate PDP Context Request (DCH) RANAP: Direct Transfer: GPRS Activate PDP Context Request
RANAP: Direct Transfer : GPRS P-TMSI Reallocation CommandRRC: Downlink Direct Transfer : GPRS P-TMSI Reallocation Command (DCH)

Ps call flow

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