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 and CN) the dedicated channel between the UE and the RNC is released and UE is moved to Cell_FACH or Cell_PCH cell state

UE is powered up

Read BCCH

Cell selection

Register with core network

Cell State Transitions

Radio frame synchronisatio

n

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

MACRLC-C

AAL2

FP

ATM

Phy

MACRLC-C

UE

Node 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

MACRLC-U

AAL2

FP

ATM

Phy

MACRLC-U

AAL5

ATM

Phy

GTP-U

AAL5

ATM

Phy

UE

Node 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




n

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




n

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




n

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




n

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




n

Cell search

Originating PS Call

UTRAN Specific Signalling Protocols

3G-MSC/VLR

3G-SGSN

UE Node BRNC

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


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


Node B

NBAP: Radio Link Setup Request

NBAP: Radio Link Setup Response

ALCAP: Establish Request

RRC Connection Setup Complete

ALCAP: Establish Confirm

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 RequestSCCP: Connection Request

• The RANAP: Initial UE Message message is accompanied with a SCCP: Connection Request message which is used to establish the Iu-PS connection orientated link

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)SCCP: Connection Confirm



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 ResponseDirect 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 ResponseDirect Transfer: Authentication and Ciphering RequestDownlink Direct Transfer: Authentication and Ciphering Request (DCH)





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)Uplink Direct Transfer: Authenication and Ciphering Response (DCH) Direct Transfer: Authentication and Ciphering Response

Direct Transfer: Authentication and Ciphering RequestDownlink Direct Transfer: Authentication and Ciphering Request (DCH)SCCP: Connection Confirm




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-ordinationUE RNC SGSNNode B

Secuirty Mode Complete (DCH)Security Mode CommandSecurity Mode Command (DCH)






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

Uplink Direct Transfer: Identity Response (DCH)Direct Transfer: Identity RequestDownlink Direct Transfer: Common ID (DCH)

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


Downlink Direct Transfer: Location Attach Accept (DCH)Direct Transfer: Attach CompleteUplink Direct Transfer: Attach Complete (DCH)

Summary of GPRS Attach

RRC Connection Setup Complete (DCH)

FP: Downlink SyncFP: Uplink Sync

NBAP: Synchronisation Indication


NBAP: Radio Link Setup RequestNBAP: Radio Link Setup Response

ALCAP: Establish RequestALCAP: Establish Confirm



UE RNC SGSNNode B




Initial Direct Transfer: GPRS Attach Request (DCH)Initial UE message : GPRS Attach Request

SCCP: Connection Request

Common ID


Downlink Direct Transfer: Location Attach Accept (DCH)Direct Transfer: Attach CompleteUplink Direct Transfer: Attach Complete (DCH)

L1 Synchronisation

RRC Connection Request (RACH)

PS CallUE is powered up

Read BCCH

Cell selection




n

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

Activate PDP Context 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 requestGPRS Attach

NAS – Message: Activate PDP Context 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 requestRAB Assignment 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

Uplink Direct Transfer : Activate PDP context request (DCH) Direct Transfer : Activate PDP context requestRANAP: 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 PS connection

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


RRC: Radio Bearer SetupRadio Bearer Setup Complete

• 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

RAB Assignment Response

GPRS Attach

Measurement ControlUE RNC SGSNNode B



RAB Assignment ResponseMeasurement 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 traffic volume measurements which are used for the UL capacity requests

Measurement Control

GPRS Attach

Activate PDP Context 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 ControlMeasurement Control

GPRS Attach

64kbps UL & DL Connection EstablishedUE RNC SGSNNode B



•UL: 64 DL: 64 kbps PS data call Established



Call Established


GPRS Attach

Measurement Reporting

Reporting Event 4a

UE RNC SGSNNode B





Packet Call Established


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



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



GPRS Attach

AAL2SIG:ECFAAL2SIG:ERQ


UE RNC SGSNNode B






Call Established




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



UE RNC SGSNNode B






Call Established





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



UE RNC SGSNNode B






Call Established





Radio Bearer Reconfiguration Complete

• The UE acknowledges the RRC: Radio Bearer Reconfiguration message with a RRC: Radio Bearer Reconfiguration Complete message

RRC: Radio Bearer Reconfiguration (DCH)RRC: Radio Bearer Reconfiguration Complete (DCH)

GPRS Attach



UE RNC SGSNNode B






Call Established





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




n

Cell search

Originating PS Call



UE RNC SGSNNode B


Call Established




Radio Bearer Reconfiguration


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


• The UE acknowledges the RRC: Radio Bearer Reconfiguration message with a RRC: Radio Bearer Reconfiguration Complete message on RACH



UE RNC SGSNNode B


Call Established



Radio Link Reconfiguration CommitRRC: Radio Bearer Reconfiguration (DCH)

RRC: Radio Bearer Reconfiguration Complete (DCH)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)



UE RNC SGSNNode B


Call Established






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




UE RNC SGSNNode B


Call Established






Data Flow


NBAP: Radio Link Deletion Request

GPRS Attach

Radio Link Deletion Response




UE RNC SGSNNode B


Call Established






Data Flow


NBAP: Radio Link Deletion ResponseNBAP: Radio Link Deletion Request

GPRS Attach

UE in Cell_FACH




UE RNC SGSNNode B


GPRS Attach

Call Established






Data Flow



ALCAP: Release RequestALCAP: 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






UE in Cell_PCH, PDP Context Active and GPRS AttachedRRC: 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: Cell Update Confirm (FACH)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 Request

UE RNC SGSNNode B

GPRS Attach

Call Established

Data Flow







NBAP: Radio Link Setup ResponseNBAP: Radio Link Setup



As explained earlier: this time just set up 64/64

Radio Bearer Reconfiguration UE RNC SGSNNode B

GPRS Attach

Call Established

Data Flow











As explained earlier: this time just set up 64/64

UE RNC SGSNNode B

GPRS Attach

Call Established

Data Flow









FP: Downlink SyncFP: Uplink SyncNBAP: Synchronisation Indication

RRC: Radio Bearer Reconfiguration (FACH)


RRC: Radio Bearer Reconfiguration Complete (DCH)NBAP: Synchronisation Indication


UE RNC SGSNNode B

GPRS Attach

Call Established

Data Flow









FP: Downlink SyncFP: Uplink SyncNBAP: Synchronisation Indication

RRC: Radio Bearer Reconfiguration (FACH)


RRC: Radio Bearer Reconfiguration Complete (DCH)NBAP: Synchronisation Indication

Measurement Control


Measurement Control for intra-frequency measurements and stopping traffic volume measurements, as before

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

UE in Cell_DCH, PDP Context Active and GPRS Attached

Deactivate PDP Context Accept

UpLink Direct Transfer : Deactivate PDP Context Request (DCH) Direct Transfer : Deactivate PDP Context RequestDirect 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

RAB Assignment Request

RANAP: RAB Assignment Request

UE RNC SGSNNode B

GPRS Attach

Call Established

Data Flow

UE in Cell_DCH, PDP Context Active and GPRS AttachedUpLink 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 sends the RAB modification (release) request to the RNC by RANAP: RAB Assignment Request


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

RANAP: RAB Assignment RequestRANAP: RAB Assignment Response

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 PrepareNBAP: 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




NBAP: Radio Link Reconfiguration CommitRRC: 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




NBAP: Radio Link Reconfiguration CommitRRC: 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 Iu) but still GPRS Attached

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 AttachedRRC : 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 SetupNBAP : Radio Link Setup Response

RRC: Radio Bearer Reconfiguration (FACH)NBAP : Radio Link Synchronisation

RRC: Radio Bearer Reconfiguration Complete (DCH)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 DeactiveRRC : RRC Connection request (RACH)

RRC : RRC Connection Setup (FACH)

Initial UE Message : GPRS Service RequestRRC : RRC Connection Setup Complete (DCH)

NBAP : Radio Link SetupNBAP : 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 ResponseRRC: Measurement Control (DCH)RRC: Measurement Control (DCH)

RRC : Measurement Report (e4a) (DCH)NBAP : Radio Link Reconfiguration PrepareNBAP : Radio Link Reconfiguration Ready

NBAP : Radio Link Reconfiguration CommitRRC: Radio Bearer Reconfiguration (DCH)

RRC : Radio Bearer Reconfiguration Complete (DCH)RRC: Measurement Control (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 RequestRANAP: Direct Transfer : GPRS P-TMSI Reallocation CommandRRC: Downlink Direct Transfer : GPRS P-TMSI Reallocation Command (DCH)

Date post:	20-Mar-2017
Category:	Engineering
Upload:	sudhir-kumar
View:	47 times
Download:	2 times

Ps call flow

Engineering