Radio interface ps_procedures

1 © Nokia Siemens Networks Presentation / Author / DateFor internal use

Signalling Flow:

PS Call

Establishment


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 and 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 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

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

MAC

RLC-U

AAL2

FP

ATM

Phy

MAC

RLC-U

AAL5

ATM

Phy

GTP-U

AAL5

ATM

Phy

UE

Node B

RNC SGSN

Uu Iub Iu,ps

UDP

IP

GTP-U

UDP

IP


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




Cell search

Originating PS Call


Cell Selection • 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




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




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 Connection Setup UE Node-B RNC CN

RRC Connection Setup Request ( CCCH on RACH)

Radio Link Setup Request NBAPNBAP

Radio Link Setup Response

NBAPNBAP

RRC Connection Setup Complete (DCCH on DCH)

RRC Connection Setup (CCCH on FACH)

Establish RequestALCAPALCAP

Establish ResponseALCAPALCAP

RRC RRC

RRCRRC

RRC RRC

Signalling Bearer

establishment


GPRS Attach

UEATTACH REQUEST ( )

(Identification Procedure)

Authentication and Ciphering Procedure

ATTACH ACCEPT ( )

e.g. new TMSIor P-TMSI

ATTACH COMPLETE ( )

3G-SGSN


Initial Direct Transfer

UE RNC MSC

RRC Connection Setup


CM Service RequestRRC RRC

Node-B

UE RNC SGSN Node-B

Initial UE Message

CM Service RequestRANAPRANAP


Attach Request GMMRRC RRC

Initial UE Message

Attach Request GMMRANAPRANAP

RRC Connection Setup


PS CallUE is powered up

Read BCCH

Cell selection




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 request

GPRS Attach


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

NAS: Activate PDP Context Request


RAB Assignment Request

UE RNC SGSNNode B

Uplink Direct Transfer : Activate PDP context request (DCH) Direct Transfer : Activate PDP context request

RAB 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


RANAP: RAB Assignment RequestRRC: Radio Bearer Setup

• Once the RANAP: RAB Assignment Request message has been received from PS CN and RNC has resources to setup the 0/0 kbps RB the RNC sends a RRC: Radio Bearer Setup message to the UE

GPRS Attach


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




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 Control

Measurement Control

GPRS Attach


PS call established

UE RNC SGSNNode B




•PS data call Established, but 0/0 kbps RB



Call Established

Measurement Control

Measurement Control

GPRS Attach


Radio Bearer Setup

UE Initiated PDP Context Activation

UE

3G-SGSN

GGSNACTIVATE PDP CONTEXT REQUEST ( )

ACTIVATE PDP CONTEXT ACCEPT ( )

CREATE PDP CONTEXT REQUEST

CREATE PDP CONTEXT RESPONSE

UPDATE PDP CONTEXT REQUEST

UPDATE PDP CONTEXT RESPONSE


Reporting event:4A: Transport Channel Traffic Volume becomes larger than an absolute threshold4B: Transport Channel Traffic Volume becomes smaller than an absolute threshold

time

TransportChannelTrafficVolume(TCTV)

Threshold

4B

4A

4B 4B

4A4A

Traffic Volume Measurements


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 Ready

UE RNC SGSNNode B

NBAP: Radio Link Reconfigure Prepare






Call Established

Measurement Control

Measurement Control


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

Measurement Control

Measurement Control


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

Measurement Control

Measurement Control


UL: 64kbps DL: 64 kbps Connection Established


GPRS Attach

64 kbps service established



• 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 inactivity i.e. no capacity requests from UE nor RNC the UE is further moved to Cell_PCH where the UE only listens to PCH (paging channel)

UE is powered up

Read BCCH

Cell selection




Cell search

Originating PS Call


AAL2SIG:ECFAAL2SIG:ERQ


UE RNC SGSNNode B


Call Established


FP: Downlink Sync

FP: Uplink SyncRadio Link Reconfiguration Commit

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


Radio Bearer Reconfiguration Complete

• 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


FP: Downlink Sync



Measurement Control


Data Flow

RRC: Radio Bearer Reconfiguration Complete (RACH)

GPRS Attach


UE in Cell_FACH

Measurement Control (FACH)



UE RNC SGSNNode B


GPRS Attach

Call Established


FP: Downlink Sync



Measurement Control


Data Flow


NBAP: Radio Link Deletion Response

NBAP: Radio Link Deletion Request

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










RRC: Cell Update (RACH)

• 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)


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


Radio Bearer Release

RANAP: RAB Assignment Request

RANAP: RAB Assignment Response

UE RNC SGSNNode B

GPRS Attach

Call Established

Data Flow


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)

NBAP: Radio Link Reconfiguration Prepare

NBAP: Radio Link Reconfiguration Ready

NBAP: Radio Link Reconfiguration Commit

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 Iu) but still GPRS Attached

RRC: Radio Bearer Release Complete (DCH)

Technology

Radio interface ps_procedures