Call Setup and Release

Call Setup and Release

DN99580908 © Nokia Networks Oy 1 (60)Issue 1-2 en Nokia Proprietary and Confidential


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Copyright © Nokia Networks Oy 2001. All rights reserved.

2 (60) © Nokia Networks Oy DN99580908Nokia Proprietary and Confidential Issue 1-2en

Contents

Contents 3

List of tables 4

List of figures 5

1 Purpose of call setup and release 7

2 Functionality of real-time services 9

3 Functionality of non-real-time services 15

4 Call setup and release procedures 274.1 Paging 284.1.1 Paging an idle mode MS (paging procedure) 284.1.2 Paging a connected mode MS (UE dedicated paging procedure) 294.1.3 RNC originated paging 314.2 RRC connection setup 314.3 RRC connection release 334.4 Radio link setup 334.5 Radio link reconfiguration 364.6 Radio link deletion 374.7 Radio access bearer setup 384.8 Radio access bearer reconfiguration 404.9 Radio access bearer release 424.10 Signalling connection release 434.11 Direct transfer 454.12 Ciphering and integrity protection setup 464.13 Cell update 474.14 URA update 494.15 Parameters 504.16 Statistics 504.17 Alarms 52

5 Related features 53

6 Restrictions 55

Glossary 57



List of tables

Table 1. MS cell states. 20


List of figures

Figure 1. Mobile originated call (CS), 1/2. 10

Figure 2. Mobile originated call (CS), 2/2. 11

Figure 3. Mobile terminated call (CS), 1/2. 12

Figure 4. Mobile terminated call (CS), 2/2. 13

Figure 5. Mobile originated call (PS), 1/2. 16

Figure 6. Mobile originated call (PS), 2/2. 17

Figure 7. Mobile terminated call (PS), 1/2. 18

Figure 8. Mobile terminated call (PS), 2/2. 19

Figure 9. MS cell state transitions. 20

Figure 10. CELL_DCH to CELL_FACH state transition using Radio BearerReconfiguration. 22

Figure 11. CELL_FACH to CELL_DCH UL state transition. 23

Figure 12. CELL_FACH to CELL_DCH DL state transition. 24

Figure 13. Cell update due to UL data transmission. 25

Figure 14. Paging an MS in idle mode. 29

Figure 15. Paging an MS in connected mode (CELL_FACH or CELL_DCHstate). 30

Figure 16. Paging an MS in connected mode (CELL_PCH or URA_PCH state). 30

Figure 17. RNC-originated paging. 31

Figure 18. Setting up an RRC connection. 32

Figure 19. RRC connection setup failure and retry. 32

Figure 20. RRC connection release in CELL_DCH state. 33

Figure 21. Radio link setup. 34

Figure 22. Radio link setup failure. 35

Figure 23. Synchronisation failure. 35

Figure 24. Synchronised radio link reconfiguration. 36

Figure 25. Radio link reconfiguration failure. 37

Figure 26. Radio link deletion. 38

Figure 27. Radio access bearer establishment procedure (DCH to DCH). 39

Figure 28. Failure in radio access bearer establishment. 40



Figure 29. Radio access bearer reconfiguration procedure (DCH to DCH). 41

Figure 30. Failure in radio access bearer reconfiguration. 42

Figure 31. Radio access bearer release. 43

Figure 32. Signalling connection release requested by the CN. 44

Figure 33. Signalling connection release requested by the MS (all flows are notreleased). 45

Figure 34. Signalling connection setup. 46

Figure 35. Setting up ciphering and integrity protection. 47

Figure 36. Cell update due to periodic update. 48

Figure 37. Periodic URA update. 50


Purpose of call setup and release

1 Purpose of call setup and releaseCall setup and release refers to setting up or releasing a speech or data connectionbetween the end-user mobile station (MS) and the core network. When the MS isin idle state, it has no radio resource control (RRC) connection to the radio accessnetwork. Radio resource control (RRC) connection is set up when the MSrequests it or when it is paged. The RRC connection is needed for radio accessbearer establishment. Radio access bearer services can involve a circuit switchedspeech call, a circuit switched data call or a packet switched call.

For more information, see:

2Functionality of real-time services

3Functionality of non-real-time services

Call setup and release procedures

Related features


Functionality of real-time services

2 Functionality of real-time servicesReal-time services involve mobile-originated and mobile-terminated speech ordata calls. The following figures illustrate the process of establishing these twotypes of call. Individual procedures mentioned in the figures are described insection Call setup and release procedures.



Figure 1. Mobile originated call (CS), 1/2.

MS BTS RNC MSC

AAL2 Setup

RRC:RRC CONNECTION SETUP

RANAP:INITIAL UE MESSAGE

NBAP:SYNCHRONIZATION INDICATION

RRC:CONNECTION SETUP COMPLETE

RRC:INITIAL DIRECT TRANSFER

NBAP:RADIO LINK SETUP REQUEST

RRC:RRC CONNECTION REQUEST

NBAP:RADIO LINK SETUP RESPONSE

MS-CN signalling

RANAP:COMMON ID

MS-CN signalling

RANAP:SECURITY MODE COMMAND

RRC:SECURITY MODE COMMAND

RRC:SECURITY MODE COMPLETE

RANAP:SECURITY MODE COMPLETE

L1 synchronisation



Figure 2. Mobile originated call (CS), 2/2.

The following figure illustrates the mobile terminated circuit switched call. Theonly difference between a mobile originated and mobile terminated call is thatonly mobile terminated calls include paging the MS.

MS BTS RNCMS

AAL2 Setup

RANAP:RAB ASSIGNMENT REQUEST

NBAP:RADIO LINK RECONFIGURATION PREPARE

NBAP:RADIO LINK RECONFIGURATION READY

AAL2 Setup

Connection established

NBAP:RADIO LINK RECONFIGURATION COMMIT

RRC:RADIO BEARER SETUP

RRC:RADIO BEARER SETUP COMPLETE

RANAP:RAB ASSIGNMENT RESPONSE

MSC



Figure 3. Mobile terminated call (CS), 1/2.

MS BTS RNC MSC

AAL2 Setup









MS-CN signalling

RANAP:COMMON ID

MS-CN signalling





RRC: PAGING TYPE 1

RANAP: PAGING

L1 synchronisation



Figure 4. Mobile terminated call (CS), 2/2.

MS BTS RNCMS

AAL2 Setup




AAL2 Setup

Connection established





MSC


Functionality of non-real-time services

3 Functionality of non-real-time servicesNon-real-time services involve packet switched data calls. For NRT (non-realtime) services, the radio access bearer is created without immediately reservingradio resources. The resources are allocated on demand by using the signallinglink between the MS and the RNC. The following figures illustrate the process ofestablishing a packet switched call.



Figure 5. Mobile originated call (PS), 1/2.

MS BTS RNC SGSN

AAL2 Setup









MS-CN signalling

RANAP:COMMON ID

MS-CN signalling





L1 synchronisation



Figure 6. Mobile originated call (PS), 2/2.

The following figure illustrates the mobile terminated packet switched call. Theonly difference between mobile originated and mobile terminated calls is thatonly mobile terminated calls include paging the MS.

MS BTS RNCMS


GTP Tunnel setup

Connection established (CELL_DCH state)




SGSN



Figure 7. Mobile terminated call (PS), 1/2.

MS BTS RNC SGSN

AAL2 Setup









MS-CN signalling

RANAP:COMMON ID

MS-CN signalling





RRC:PAGING TYPE 1

RANAP: PAGING

L1 synchronisation



Figure 8. Mobile terminated call (PS), 2/2.

When the MS has a dedicated physical channel, it is in CELL_DCH state. Statetransitions are illustrated in the following figure:

MS BTS RNCMS


GTP Tunnel setup

Connection established (CELL_DCH state)




SGSN



Figure 9. MS cell state transitions.

URA_PCH

CELL_DCH

Idle Mode

CELL_FACH

RAN Connected Mode

CELL_PCH

Release RRC connectionRelease RRC connection

Establish RRC connection

Table 1. MS cell states.

MS cell state Description

CELL_DCH MS receives and transmits on the dedicated trafficchannel (DCH). The location of the MS is known on celllevel.

CELL_FACH MS receives on the forward access channel (FACH)and transmits on the random access channel (RACH).The location of the MS is known on cell level.

CELL_PCH MS receives on the paging channel (PCH). Thelocation of the MS is known on cell level. If the MS hassomething to transmit, it transfers to CELL_FACH state.

URA_PCH MS receives on the paging channel (PCH). Thelocation of the MS is known on URA level. If the MS hassomething to transmit, it transfers to CELL_FACH state.



When the RNC detects inactivity in either uplink or downlink, it starts aninactivity timer in that direction. If the timer in both directions expires and theinactivity continues, the RNC releases the dedicated resources and starts the MS'stransition from CELL_DCH to CELL_FACH state. The transition is usually donewith the radio bearer reconfiguration procedure. In some special cases it is donewith either the physical channel reconfiguration procedure or the radio bearerrelease procedure.

The radio bearer reconfiguration procedure is used, if the RLC parameters of theNRT RB need to be reconfigured when the DCH of the NRT RB is released.

The physical channel reconfiguration procedure is used, if the DCH of the NRTRB is released, and there are no other DCH allocations.

The radio bearer release procedure is used when a NRT RAB and a RT RAB aresimultaneously used for the same MS, and the NRT RAB has been inactive (theinactivity timer has expired) when the CN releases the RT RAB.

The following figure illustrates the state transition using radio bearerreconfiguration:



Figure 10. CELL_DCH to CELL_FACH state transition using RadioBearer Reconfiguration.

The transition from CELL_FACH state to CELL_DCH state is started when theRNC has user or control data waiting for transmission in downlink direction orwhen the MS requests capacity for user data in uplink direction. The RNC's RM(resource manager) checks that there are resources available and allocates therequested resources. It also requests a radio link setup procedure (refer to sectionRadio link setup).

Once a radio link is set up, the transition is done either with the transport channelreconfiguration procedure, the radio bearer reconfiguration procedure, or theradio bearer setup procedure.

The transport channel reconfiguration procedure is used, if a state transition isneeded and it does not need reconfiguration.

The radio bearer reconfiguration procedure is used, if the RLC parameters of theNRT RB need to be reconfigured.

MS is in CELL_DCH state

Inactivity timer expires

RRC:RADIO BEARER RECONFIGURATION

RRC:RADIO BEARER RECONFIGURATION COMPLETE

MS is in CELL_FACH state

CELL UPDATE

CELL UPDATE CONFIRM

NBAP: RADIO LINK DELETION REQUEST

NBAP: RADIO LINK DELETION RESPONSE

RNCMS BTS



The radio bearer setup procedure is used, if a NRT RAB already exists and a newRT RAB must be established.

The following figure illustrates the state transition from CELL_FACH toCELL_DCH:

Figure 11. CELL_FACH to CELL_DCH UL state transition.

RNCMS BTS


RRC: RADIO BEARER RECONFIGURATION

RRC: RADIO BEARER RECONFIGURATION COMPLETE

NBAP Radio Link Setup

RRC:MEASUREMENT REPORT




Figure 12. CELL_FACH to CELL_DCH DL state transition.

Uplink data transmission may cause a cell update as illustrated in the figurebelow.

RNCMS BTS


RRC: RADIO BEARER RECONFIGURATION

RRC: RADIO BEARER RECONFIGURATION COMPLETE

NBAP Radio Link Setup


DL capacity need detected



Figure 13. Cell update due to UL data transmission.

RNCMS BTS

UL capacity need is detected by MAC

MS moves to CELL_FACH state

MS is in CELL_PCH state or URA_PCH state

RRC:CELL UPDATE CONFIRM

RRC:CELL UPDATE

RRC:RNTI REALLOCATION COMPLETE(only URA_PCH)




4 Call setup and release proceduresThis section describes the procedures involved in real-time and non-real-time callsetup and release. See sections Functionality of real-time services andFunctionality of non-real-time services for the illustration of call setup andrelease phases. This section also briefly describes parameters and statistics.

The signalling protocols mentioned in the figures are:

• RANAP (radio access network application part)

• RNSAP (radio network subsystem application part)

• NBAP (Node B application part)

• RRC (radio resource control)

RANAP layer

RANAP layer includes all the RANAP signalling entities of the RNC and therelated application for RANAP signalling entity management.

RANAP signalling entity is a serving RNC functionality responsible for theRANAP-connection-specific signalling and information management betweenthe RNC and core network for one MS.

RNSAP layer

RNSAP layer includes all the RNSAP signalling entities of the RNC and therelated application for RNSAP signalling entity management.

RNSAP signalling entity is an RNC functionality responsible for RNSAP-connection-specific signalling and information management between two RNCsfor one MS.

NBAP layer

NBAP layer includes all common and dedicated NBAP signalling entities of theRNC or the BTS and the related application for the NBAP signalling entitymanagement.



Common NBAP signalling entity is a BTS or a controlling RNC functionalityresponsible for the logical resource management, BCH management andcommunication context creation for one BTS.

Dedicated NBAP signalling entity is a BTS or a controlling RNC functionalityresponsible for the radio link management for a group of MSs.

RRC layer

RRC layer includes all RRC signalling entities of the RNC and the relatedapplication for RRC signalling entity management.

RRC signalling entity is a serving RNC functionality responsible for the RRC-connection-specific signalling and information management for one MS.

4.1 Paging

Core network (CN) requests the RNC to page an MS. RNC receives pagingrequests from the core network over the Iu interface.

The MS may use discontinuous reception (DRX) in idle mode to reduce powerconsumption. In discontinuous transmission, the MS only monitors one pageindicator (PI) in one paging occasion per DRX cycle. The DRX cycle is anindividual time interval between the monitoring paging occasions for a specificMS. The maximum DRX cycle is the time interval for the longest possible DRXcycle in a cell.

The MS may be attached to the circuit switched and packet switched corenetworks with different CN-domain-specific DRX cycle lengths. The MS storeseach domain-specific DRX cycle length for each CN domain it is attached to anduses the shortest of those DRX cycle lengths. If the CN sends a specific DRXcycle length coefficient, RAN uses it in the paging message. If there is no CN-specific coefficient, RAN uses the default value for CN-specific DRX cyclelength coefficient in the radio network database.

RNC sends paging requests to all WCDMA BTSs which belong to the pagingarea where the MS is currently registered. The cells in a single BTS may belongto different paging areas.

Each paging message on the Iu interface involves only one MS and therefore, theRNC has to pack the pages into the relevant radio interface paging message.

4.1.1 Paging an idle mode MS (paging procedure)

The RNC checks whether the paged MS is engaged in an ongoing radio resourcecontrol (RRC) connection. If there is no connection, the RNC starts the idle modepaging procedure. As a result, the MS starts the RRC connection setup procedure.



The procedure using the PAGING TYPE 1 message is referred to as pagingprocedure in the 3GPP RRC specification.

Figure 14. Paging an MS in idle mode.

4.1.2 Paging a connected mode MS (UE dedicated paging procedure)

The RNC checks whether the paged MS already has an RRC connection. If itdoes, the connected mode paging procedure is applied. RNC sends a pagingmessage (RRC:PAGING TYPE 2) to an RRC-connected MS through the existingRRC connection if the MS is in CELL_DCH or CELL_FACH state. If the MS isin CELL_PCH or URA_PCH state, the RNC originates the paging procedure(RRC:PAGING TYPE1).

The procedure using the PAGING TYPE 2 message is referred to as UE dedicatedpaging procedure in the 3GPP RRC specification.

CNMS BTS

PAGING TYPE 1

RANAP:PAGING

MS has no RRC connection

RRC connection establishment

Paging response

RNC



Figure 15. Paging an MS in connected mode (CELL_FACH orCELL_DCH state).

Figure 16. Paging an MS in connected mode (CELL_PCH or URA_PCHstate).

CN 2MS BTS RNC CN 1

MS has signalling connection to CN1

MS is in CELL_FACH or CELL_DCH state

Paging response to CN 2

RRC:PAGING TYPE 2

RANAP:PAGING

CN 2MS BTS RNC CN 1

MS has signalling connection to CN1

MS is in CELL_PCH or URA_PCH state

Paging response to CN 2

RRC:PAGING TYPE 1

RANAP:PAGING



4.1.3 RNC originated paging

To save its battery, an MS may reside on common channels (the paging channel)while still maintaining the RRC connection to RNC. In such a case, the RNCneeds to page the MS when there is downlink user data or a downlink signallingmessage addressed to the MS. This is because in CELL_PCH or URA_PCH state,the DCCH logical channel cannot be used. Therefore, the RNC transmits a pagingrequest on the PCCH logical channel in the known cell or within the URA wherethe MS is located. RNC's RRC signalling entity starts the paging procedure. As aresponse, the MS moves to the CELL_FACH state and starts the cell updateprocedure with the cause “paging response”.

If an MS in CELL_PCH or URA_PCH state needs to transmit anything to theRAN, it moves to the CELL_FACH state and executes a cell update procedurewith the cause “UL data transmission”.

Figure 17. RNC-originated paging.

4.2 RRC connection setup

RRC connection is always started by the MS. MS sends a message to the RNCrequesting RRC connection setup. RNC sets up a radio link and sends the MS thephysical channel information. After the MS has synchronised itself to theWCDMA BTS, it transmits an acknowledgement to the RNC..

Once the MS has set up the RRC connection, it may send higher-layer messages,for instance, a call setup message.

MS BTS RNC

MS is in CELL_PCH or URA_PCH state

RRC: PAGING TYPE 1

DL data or DL signalling messages

MS makes a transition from CELL_PCH or URA_PCH to CELL_FACH state

MS performs a cell update with the cause "paging response"



Figure 18. Setting up an RRC connection.

The following figure illustrates an example of an RRC connection failure. TheRNC may fail in its attempt to set up a radio link due to hardware blocking, forinstance. Also, admission control may reject the setup attempt. In an errorsituation, the RNC transmits an RRC connection setup reject message, and theMS initiates an RRC connection setup retry timer. When the timer expires, theMS attempts to set up the RRC connection again.

Figure 19. RRC connection setup failure and retry.

RNCMS BTS

RRC: RRC CONNECTION SETUP

L1 synchronisation

Radio link setup

RRC: RRC CONNECTION SETUP REQUEST

RRC: RRC CONNECTION SETUP COMPLETE

MS BTS RNC

RRC: RRC CONNECTION REJECT





4.3 RRC connection release

Radio resource control connection is released when the MS no longer has anactive signalling connection to any core network node. MS and CN negotiateabout the release, and after that, the CN sends a release command. The MS inCELL_DCH state sends an acknowledgement message in unacknowledged modeto the radio access network. If the MS receives the release message while inCELL_FACH state, it responds in acknowledged mode to the RAN.

After the MS response, the RNC starts the radio link release procedure towardsBTS, releases transport bearers on the Iub interface, and sends anacknowledgement to the core network. The RNC can delete the RRC entity of theMS at the same time with the radio link release procedures.

Figure 20. RRC connection release in CELL_DCH state.

4.4 Radio link setup

Radio link setup procedure is started when a new radio link is needed, forinstance, when a new signalling link is set up or when handover is performed.RNC determines the radio link parameters and requests radio link activation at theBTS. In the first radio link setup, the BTS selects the traffic termination point forthe communication context and sends the identification of the associated NBAPsignalling link to the RNC. The radio link allocation is valid at the BTS until theRNC orders radio link deletion.

MS BTS RNC CN

MS has signalling connection to one CN

Radio link deletion procedure

RANAP: IU RELEASE COMMAND

RRC: RRC CONNECTION RELEASE

RANAP: IU RELEASE COMPLETE

RRC: RRC CONNECTION RELEASE COMPLETE



The procedure also starts the creation or modification of a communicationcontext. Communication context contains information about all activity in onetraffic termination point concerning one MS. It is used to associate a set of radiolinks together at the BTS.

Figure 21. Radio link setup.

Error situations that may occur during radio link setup are illustrated in thefollowing figures. Radio link setup may fail because resources are not availableor because the controlling RNC communication context is already in use, forexample. If radio link setup fails, the BTS sends a failure message to the RNCindicating the cause value. The BTS's L3 Common NBAP signalling entity sendsthe message to the RNC's L3 Common NBAP signalling entity.


AAL2 Setup


RRC:Assignment to MS

L1 synchronisation

MS RNCBTS




Figure 22. Radio link setup failure.

If the BTS fails to establish synchronisation at the time defined, the BTS's L3Dedicated NBAP signalling entity generates a failure message indicating thecause “synchronisation failure”.

Figure 23. Synchronisation failure.

MS

NBAP:RADIO LINK SETUP FAILURE


BTS RNC


AAL2 Setup



MS BTS RNC

NBAP:RADIO LINK FAILURE (SYNC FAIL)



4.5 Radio link reconfiguration

Synchronised radio link reconfiguration is used to add, delete or modify a DCH(dedicated channel) or to modify the radio links belonging to the samecommunication context. The resource manager of the RNC initiates thereconfiguration procedure.

The situations that may trigger the radio link reconfiguration procedure are:

• radio access bearer setup (AAL2 setup)

• radio access bearer negotiation (possible AAL2 setup, switching, andrelease)

• radio access bearer release (AAL2 release)

• NRT radio access bearer scheduling (AAL2 setup, possible AAL2switching, AAL2 release).

Figure 24. Synchronised radio link reconfiguration.

MS BTS RNC


AAL2 Setup if needed



AAL2 Switching if needed

AAL2 Release if needed




Radio link reconfiguration may fail because of a BTS capability failure orbecause there are not enough resources, for example. The BTS responds with afailure message to the RNC's prepare message. The failure message indicates thefailed radio links and the cause value for the failure.

Figure 25. Radio link reconfiguration failure.

4.6 Radio link deletion

RNC starts the radio link deletion procedure to release one or more radio links ina communication context. Resets and other error situations may trigger thisprocedure.

If the RNC does not receive a response from the BTS before a timer expires, itsends the deletion message again three times. After that, if there is still no answer,the resource manager in the RNC starts recovery actions.

MS BTS RNC

NBAP:RADIO LINK RECONFIGURATION FAILURE




Figure 26. Radio link deletion.

4.7 Radio access bearer setup

The procedure builds a radio access bearer service between the MS and the CN(core network). The service is negotiated between MS and CN via the signallinglink between the MS and RAN (radio access network) and via the signallingconnection between RAN and CN.

Once the CN has all the necessary information, it forwards it to the RNC. RNCanalyses the parameters for radio access bearer service and checks whether theresources needed exist. After that, the RNC activates or modifies the physicaluplink and downlink radio channels from the WCDMA BTS and creates thetransmission channels at the Iub and Iur interfaces according to the reserved radioresources.

RNC then sends the new radio link parameters to the MS on the existingsignalling link. Once the MS informs the RNC that it uses the new radio linkparameters, the RNC acknowledges the information to the CN and radio accessbearer establishment is then complete.

The same procedure is also used for adding radio access bearers.

For NRT (non-real time) services, the radio access bearers are created withoutimmediate reservation of radio resources. Instead, radio resources are allocatedon demand by using the signalling link between the MS and the RNC.

MS BTS RNC

AAL2 Release

NBAP:RADIO LINK DELETION REQUEST

NBAP:RADIO LINK DELETION RESPONSE



Figure 27. Radio access bearer establishment procedure (DCH to DCH).

Setting up a radio access bearer may fail, for instance, because the RNC cannotprovide the resources requested. If the requested channel type or resource (e.g.channel rate, etc.) indicated in the RANAP:RAB ASSIGNMENT REQUESTmessage is not available in the RAN, a RANAP:RAB ASSIGNMENTRESPONSE message is sent to the CN. The message contains the appropriatefailure cause.

Signalling link established, MM and CC signalling ...

BTS RNC CNMS

AAL2 Setup (real time RAB)

CC continues...

RANAP:RAB Assignment Request

RANAP:RAB Assignment Response

RRC:RB Setup

RRC:RB Setup Complete

Radio link reconfiguration(real time RAB)

AAL2 Setup (real time RAB)



Figure 28. Failure in radio access bearer establishment.

4.8 Radio access bearer reconfiguration

The MS and CN negotiate about the radio access bearer reconfiguration. MS orCN can request the procedure for radio access bearer reconfiguration. Theprocedure is the same whether MS or CN requests the modification.

If downgrading the radio access bearer parameters is requested, the CNimmediately accepts it and acknowledges the service modification to the MS. TheCN then requests the RNC to modify the RAN radio access bearer. If themodification is allowed, the MS and the WCDMA BTS are informed, and alsothe transmission channels are modified if needed. The RAN acknowledges to theCN that the radio access bearer service was modified.

If upgrading the radio access bearer parameters is requested, the CN first requeststhe RNC to modify radio access bearer services. If the modification is allowed,the MS and WCDMA BTS are informed, and also the transmission channels aremodified if needed.

RNC CN

Required resourcesnot available

RANAP:RAB Assignment Request

RANAP:Assignment Response(cause)

CN may send a new RAB AssignmentRequest to establish a new RAB orIu release Command to release allreserved resources.



Figure 29. Radio access bearer reconfiguration procedure (DCH toDCH).

If the requested channel type or resource (e.g. channel rate, etc.) indicated in theRANAP:RAB ASSIGNMENT REQUEST message is not available in the RAN,a RANAP:RAB ASSIGNMENT RESPONSE message is sent to the CN. Themessage contains the appropriate failure cause.

BTS RNC CNMS

AAL2 modification

RRC:RB Reconfiguration Complete

RANAP:RAB Assignment Request (modify)

CC/SM signalling, modification complete


CC/SM signalling between MS and CN, modification of RAB required

RRC:RB Reconfiguration

AAL2 modification



Figure 30. Failure in radio access bearer reconfiguration.

4.9 Radio access bearer release

The MS and CN negotiate about releasing the radio access bearer services. TheCN then commands the RAN (radio access network) to release a radio accessbearer service. RNC sends an indication of the release to the MS, and eitherreleases the radio link or modifies the radio link parameters if all radio accessbearers are not released.

The radio links are also released or modified at the WCDMA BTS, andtransmission channels are released both on the Iu and Iub interfaces. Also Iurbranches are released if the MS had branches via another (drifting) RNC.

The CN may also request releasing the signalling link if all radio access bearersrelated to the CN are released. Then the signalling connection between the RNCand CN is released. The signalling link between the RNC and MS is also releasedif the MS has no active connection to another CN.

MS BTS RNC CN

CC/SM signaling between MS and CN, modification of Radio Access Bearer required

RL reconfiguration

AAL2 modification

RANAP:RAB AssignmentRequest (modify)

RRC:RB Reconfiguration

RANAP:RAB Assignment Response (cause)

RRC:RB Reconfiguration Failure

CC/SM signaling, modify failure



Figure 31. Radio access bearer release.

From the Iu interface's point of view, radio access bearer release is alwayssuccessful. The MS may return a release failure message to the RNC. In this case,the MS uses the old configuration.

4.10 Signalling connection release

Signalling connection release can be requested by the CN or by the MS. The MSmay have an ongoing signalling connection to one circuit-switched and onepacket-switched core network simultaneously. If one network then requests therelease of the signalling connection by running the Iu release procedure, the RNCdetects that there is still another signalling connection using the current RRCconnection. The RRC connection is not released, but the MS is informed that oneof the signalling connections is released.

BTS RNC CNMS

AAL2 release

RL Reconfiguration

AAL2 release

RANAB:RAB Assignment Request (release)


RRC:RB Release

RRC:RB Release Complete



Figure 32. Signalling connection release requested by the CN.

When the MS requests the release of a signalling connection, either the signallingconnection release or the RRC connection release procedure is run as a response.If the signalling connection is released (as in the figure), the MS continues to havea signalling connection to one core network, but not two. If the RRC connectionis released, the MS no longer has connections to a core network.

RNC CN 1 CN 2BTSMS

MS-CN 1 signalling connection



RANAP:IU RELEASE COMMAND

RANAP:IU RELEASE COMPLETE

RRC:SIGNALLING CONNECTION RELEASE



Figure 33. Signalling connection release requested by the MS (all flowsare not released).

4.11 Direct transfer

After having established an RRC connection, the MS starts setting up a signallingconnection to the core network (CN). MS sends a message to the RNC whichgenerates a different message to the CN, depending on whether or not there is anactive signalling connection to the CN domain.

If low priority DCCH usage is configured in the RNC, SRB#4 (low priority) isused in the downlink direction for the NAS-PDUs using SAPI value 3. If lowpriority DCCH usage is not configured, or the SAPI value of a NAS-PDU is 0,then SRB#3 (high priority) is used.

If the RNC fails in transferring the message to the MS, the CN does not get anindication of the failure. Higher layers are used to repeat the message.

RNC CN 1 CN 2BTSMS




RANAP:IU RELEASE REQUEST

RANAP:IU RELEASE COMPLETE

RRC:SIGNALLING CONNECTION RELEASE REQUEST

Release of one signalling flow

RANAP:IU RELEASE COMMAND



Figure 34. Signalling connection setup.

4.12 Ciphering and integrity protection setup

In RNC, two security mechanisms are available: ciphering and integrityprotection. When RRC connection has been set up, the MS sends the RRCCONNECTION SETUP COMPLETE message to the RNC. The messageincludes the HFN (hyperframe number) to be used as part of the input parametersfor the ciphering and integrity algorithms, respectively.

The MS sends an initial L3 message with the MS Classmark information whichthe network needs to start security mode setup. The message is unprotected, butthe MS can verify that the correct information reached the network when thesystem returns a protected message including the MS Classmark received. Thispart is transparent to the radio access network.

Once the initial L3 message is received, user authentication can be done and newsecurity keys (integrity key and ciphering key) as well as a new key set identifier(KSI) are generated. The core network also determines which UMTS encryptionand integrity algorithms (UEAs and UIAs) are used.

Core network starts integrity protection (and possibly ciphering) by sending theSECURITY MODE COMMAND message to the serving RNC. This messagecontains the UIAs and the integrity key (IK) to be used and possibly the UEAsand the ciphering key (CK).

MS BTS RNC CN

RRC: INITIAL DIRECT TRANSFER

RANAP: INITIAL UE MESSAGE

RANAP: DIRECT TRANSFER

RRC: DOWNLINK DIRECT TRANSFER

RRC: UPLINK DIRECT TRANSFER

RANAP: DIRECT TRANSFER



The serving RNC selects the first UIA and UEA it supports from the CN's list.SRNC generates a random value FRESH and starts the downlink integrityprotection by generating the SECURITY MODE COMMAND message. Basedon input parameters, the RNC generates the message authentication code forintegrity protection (MAC-I) which is included in the message. All downlinksignalling messages after that are integrity protected and possibly ciphered.

If SRNC supports no UIAs on the list, it sends a rejection message to the corenetwork.

The MS computes the expected MAC-I value (XMAC-I) and verifies the integrityof the message by comparing the received MAC-I with the generated XMAC-I.The MS acknowledges the RNC's message with SECURITY MODECOMPLETE message which starts the uplink integrity protection. All uplinksignalling messages after that are integrity protected and possibly ciphered.

Figure 35. Setting up ciphering and integrity protection.

4.13 Cell update

Cell update procedure is mainly used to update the RNC information on the MSlocation after a cell reselection. When the MS selects a new cell, it informs theRNC in a cell update. In other words, cell update is used instead of handover. TheMS also performs periodic cell updates according to system information.

After the MS has switched to a new cell, it sends a cell update message to theRNC's RRC (radio resource control). The MS message contains the cell updatecause, which can be:

• cell reselection

• periodic cell update

MS BTS RNC CN







• uplink data transmission

• paging response

• re-entering service area

• radio link failure

• RLC unrecoverable error.

If the cell update was caused by cell reselection, the RNC updates the MS locationinformation and resets the CELL_FACH or CELL_PCH state supervision timer.RNC's confirmation message to the MS includes a radio network temporaryidentifier for the cell (C-RNTI). If the cell update was performed to a cell notresiding under the serving RNC (SRNC), the message also contains the radionetwork temporary identifier for the RAN (U-RNTI). If the MS is moving veryfast and performs frequent cell updates due to cell reselection, the RNC may orderthe MS to move to URA_PCH state.

If the cause was a periodic cell update, the RNC updates the MS locationinformation and resets the CELL_FACH or CELL_PCH state supervision timer.RNC may also instruct the MS to update its location on URA level. If the MSperforms a certain number of cell updates due to periodic cell update and isinactive (in other words, is not transmitting or receiving user data), the RNC mayorder the MS to move to URA_PCH state.

If the cause was uplink data transmission, the RNC sends a confirmation andpossibly a radio network temporary identifier (RNTI). The RNTI for a cell (C-RNTI) is sent if the MS transferred from URA_PCH state. The RNTI for RAN(U-RNTI) is sent if the cell update was performed to a cell not residing under theserving RNC (SRNC). The MS remains in CELL_FACH state.

If the cell update cause was paging response, the RNC updates the MS locationinformation. The RNC sends a confirmation and possibly a new radio networktemporary identifier for cell (C-RNTI). The MS remains in CELL_FACH state.

Figure 36. Cell update due to periodic update.

RRC:CELL UPDATE

RRC:CELL UPDATE CONFIRM

RNCMS BTS

MS is in CELL_FACH or CELL_PCH state



4.14 URA update

MS mainly uses the UTRAN registration area (URA) update procedure to informthe RNC that it has switched to a new radio access network registration area. Theprocedure is triggered after a change of cell when the MS has decoded the URAidentifiers of the cell. URA updates are also performed periodically after a timerexpires.

RAN (UTRAN) registration areas may be hierarchical to avoid excessivesignalling. This means that several URA identifiers may be broadcast in one celland that different MSs in one cell may reside in different URAs.

When the MS is in URA_PCH state and has switched to a new URA, it sends anupdate message with the U-RNTI (radio network temporary identifier) and URAupdate cause to the RNC. The cause is either URA reselection or periodic URAupdate.

If the update was due to URA reselection, the RNC registers the change of URAand sends a confirmation message to the MS. The message includes a radionetwork temporary identifier for cell (C-RNTI), if the MS remains inCELL_FACH state after the URA update. The message includes a radio networktemporary identifier for RAN (UTRAN, U-RNTI), if the URA update wasperformed to a cell not residing under the serving RNC (SRNC).

If multiple URAs are valid in the cell, RNC assigns the URA to the MS.

If the update was a periodical one, the RNC resets the periodic URA update timerand sends a confirmation message to the MS.



Figure 37. Periodic URA update.

4.15 Parameters

For operator-definable parameters, see Radio Network Parameter Dictionary.

4.16 Statistics

The following measurement types are relevant to call setup and release:

Service level measurements

Measurement includes statistics collected from:

• RRC connection setup and access (including RRC connection activereleases and failures)

• Incoming HOs and relocations

• RAB setup, access and reconfiguration.

For more information, see the Service level measurements in RNC PerformanceCounters.

RNCMS BTS

MS is in URA_PCH state

RRC:URA UPDATE

RRC:URA UPDATE CONFIRM

MS moves to URA_PCH state

MS moves to CELL_FACH state



L3 signalling measurements on Iub


• NBAP procedures for radio link setup, addition, deletion andreconfiguration.

For more information, see the L3 signalling measurements on Iub in RNCPerformance Counters.

L3 signalling measurements on Iur


• RNSAP procedures for radio link setup, addition, deletion andreconfiguration over Iur

• RNSAP and RANAP procedures for serving RNC relocation

• RNSAP and RANAP procedures for inter-RNC hard handover.

For more information, see the L3 signalling measurements on Iur in RNCPerformance Counters.

L3 signalling measurements on Iu


• RANAP procedures for radio access bearer establishment/release and Iuconnection setup/release.

For more information, see the L3 signalling measurements on Iu in RNCPerformance Counters.

RRC signalling measurements


• RRC connection management (that is, RRC connection setup/release,paging) procedures

• RRC mobility management (that is, cell and URA updates) procedures

• packet data transition states (that is, transitions between CELL_DCH,CELL_FACH, CELL_PCH and URA_PCH states)

For more information, see the RRC signalling measurements in RNCPerformance Counters.



4.17 Alarms

There are no alarms relevant to call setup and release.


Related features

5 Related featuresThe features related to call setup and release are:

• Handover control algorithm

• Power control algorithm

• Load control algorithm

• Admission control algorithm

• Resource manager algorithm

• Packet scheduler algorithm


Restrictions

6 RestrictionsThere are no restrictions relevant to call setup and release.


Glossary

Abbreviations

BCCH (broadcastcontrol channel)

BCH (broadcastchannel)

CK (ciphering key)

DCCH (dedicatedcontrol channel)

DCH (dedicatedtraffic channel)

FACH (forwardaccess channel)

HFN (hyperframenumber)

HLR (home locationregister)

IK (integrity key)

KSI (key setidentifier)

MAC-I (messageauthentication codefor integrityprotection)

MS (mobile station)

MSC (mobileservices switchingcentre)

MT (mobiletermination)

PCCH (pagingcontrol channel)

PCH (pagingchannel)



RACH (randomaccess channel)

RAN (radio accessnetwork)

RAN corresponds to UTRAN, UMTS RAN in 3GPP vocabulary.

RNC (radio networkcontroller)

RRC (radio resourcecontrol)

TE (terminalequipment)

UE (userequipment)

In 3GPP vocabulary used instead of mobile station (MS).

UEA (UMTSencryptionalgorithm)

UIA (UMTSintegrity algorithm)

UTRAN (universalterrestrial radioaccess network)

In 3GPP vocabulary used instead of radio access network (RAN).

VLR (visitorlocation register)

XMAC-I (expectedMAC-I value)

Terms

cell RNTI (C-RNTI)

C-RNTI is allocated for an MS by each controlling RNC through which the MSis able to communicate on DCCH.

communicationcontext

Communication context contains information about all activity in one traffictermination point concerning one MS. It can be used to associate a set of radiolinks together at the BTS. Radio links belonging to the same communicationcontext are in softer or soft handover.

connected mode The MS is in connected mode after it has set up an RRC connection to the RAN.

controlling RNC(CRNC)

Controlling is a role an RNC can take with respect to a specific set of BTSs. Thecontrolling RNC has the overall control of the logical resources of its BTSs. Thereis only one controlling RNC for any BTS.


drifting RNC(DRNC)

Drifting is a role an RNC can take with respect to a specific connection betweenan MS and RAN. The drifting RNC supports the serving RNC with radioresources when the connection between the RAN and the MS needs to use thecells controlled by this RNC.

drifting RNTI (D-RNTI)

D-RNTI is used by the serving RNC to identify the MS to the drifting RNC.

idle mode The MS is in idle mode when it is switched on but has no RRC connection to theRAN.

Iu interface Iu is interface between the radio network controller (RNC) and the core network(CN).

Iub interface Iub is the interface between the radio network controller (RNC) and the WCDMABTS.

Iur interface Iur is the interface between two radio network controllers (RNC).

non-access stratum(NAS)

Non-access stratum refers to the protocols between the MS and the core networkthat are not terminated in the radio access network.

radio networktemporary identifier(RNTI)

RNTI is an identifier for the MS when an RRC connection exists. For instance, itis used by the MAC protocol on common transport channels (RACH, FACH,PCH). See also cell RNTI, serving RNTI, drifting RNTI and UTRAN RNTI.

RRC connection Radio resource control connection is a logical connection between the MS andradio access network (RAN) which supports the exchange of upper layerinformation.

serving RNC(SRNC)

Serving is a role an RNC can take with respect to a specific connection betweenan MS and RAN. There is one serving RNC for each MS that has a connection toRAN. The serving RNC is in charge of the radio connection between an MS andRAN. The serving RNC terminates the Iu for this MS.

serving RNTI (S-RNTI)

S-RNTI is allocated to an MS for communicating with the serving RNC. It is alsoused by the drifting RNC to identify the MS to the serving RNC.

signallingconnection

Signalling connection is an acknowledged mode link between the MS and thecore network (CN) to transfer higher layer information between the entities in thenon-access stratum.

signalling link Signalling link provides an acknowledged mode link layer to transfer thesignalling messages between the MS and RAN as well as between the MS and CN(as part of the signalling connection).

UTRAN RNTI (U-RNTI)

UTRAN radio network temporary identifier is allocated to an MS that has an RRCconnection. The U-RNTI identifies the MS within RAN and in signallingmessages between the MS and RAN. U-RNTI consists of the serving RNCidentifier and the S-RNTI.



UTRANregistrationarea (URA)

URA is a predefined group of cells, which the RNC radio resource control usesto administer the location of the MS in URA connected state. URA id is broadcaston the BCCH. The MS must make a URA update when it enters a cell with a newURA id.


Call Setup and Release

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