Chapter 4_Location Update Procedure

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4 Location Update Procedure

About This Chapter

A location update is performed for the UE to report its location to the CN. This chapter describes

the location u pdate in terms of protocols, triggering conditions, signaling procedure of successful

location update, signaling tracing on the RNC LMT, and elementary procedures. This chapter

also describes the elementary procedures in terms of functions, triggering conditions, procedure,

and signaling in abnormal conditions.

4.1 Protocols Related to Location Update

The location update procedure complies with some 3GPP TS25 protocols and an ITU-T protocol.

4.2 Triggering Conditions of Location Update

Location update is triggered after the UE is powered on.

4.3 Signaling Procedure of Successful Location Update

This part describes the signaling procedure of a successful location update. For the messages

related to location update failures, refer to the elementary procedures.

4.4 Using the RNC LMT to Trace the Location Update Procedure

The signaling tracing function of the RNC LMT can be used to trace the signaling of a location

update.

4.5 Elementary Procedures of Location Update

This part describes the elementary procedures of location update in terms of triggering conditions

and signaling procedures in normal and abnormal conditions.

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4.1 Protocols Related to Location Update

The location update procedure complies with some 3GPP TS25 protocols and an ITU-T protocol.

The compliance protocols are as follows:

l 3GPP TS25.331 "Radio Resource Control (RRC)"

l 3GPP TS25.413 "UTRAN Iu interface RANAP signalling"

l 3GPP TS25.433 "UTRAN Iub interface Node B Application Part (NBAP) signalling"

l ITU-T Q.2630 "AAL type 2 Signalling Protocol"

4.2 Triggering Conditions of Location Update

Location update is triggered after the UE is powered on.

After being powered on, the UE searches for a cell and then receives broadcast messages. Then,

the UE triggers the location update procedure.

4.3 Signaling Procedure of Successful Location Update

This part describes the signaling procedure of a successful location update. For the messages

related to location update failures, refer to the elementary procedures.

Figure 4-1 shows the signaling procedure of a successful location update.


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Figure 4-1 Signaling procedure of a successful location update

Note the following information about the procedure shown in Figure 4-1:

l The RRC connection can be set up on a DCH or a CCH. This procedure takes the RRC

connection set up on the DCH as an example.

l If IP transport is applied to the Iub interface, the ALCAP procedure is not performed on

the Iub interface when radio links are set up or deleted.

4.4 Using the RNC LMT to Trace the Location UpdateProcedure

The signaling tracing function of the RNC LMT can be used to trace the signaling of a location

update.

Prerequisite

l The RNC LMT works properly.

l You have logged in to the RNC with an account authorized to perform tracing management.

Context

Table 4-1 lists the messages to be traced.

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Table 4-1 Messages to be traced

InterfacesandProtocols to

Be Traced

Message Name on the LMT Message Name in Protocols

Uu

RRC_RRC_CONNECT_REQ RRC CONNECTION REQUEST

RRC_RRC_CONN_SETUP RRC CONNECTION SETUP

RRC_RRC_CONN_REJ RRC CONNECTION REJECT

RRC_RRC_CONNECT_SET

UP_CMP

RRC CONNECTION SETUP

COMPLETE

RRC_INIT_DIRECT_TRANS

FINITIAL DIRECT TRANSFER

RRC_DL_DIRECT_TRANSF DOWNLINK DIRECT TRANSFER

RRC_UL_DIR_TRANSF UPLINK DIRECT TRANSFER

RRC_RRC_CONN_REL RRC CONNECTION RELEASE

RRC_RRC_CONN_REL_CM

P

RRC CONNECTION RELEASE

COMPLETE

Iub

NBAP_RL_SETUP_REQ RADIO LINK SETUP REQUEST

NBAP_RL_SETUP_RSP RADIO LINK SETUP RESPONSE

NBAP_RL_SETUP_FAIL RADIO LINK SETUP FAILURE

NBAP_RL_RESTORE_IND RADIO LINK RESTORE INDICATION

NBAP_RL_DEL_REQ RADIO LINK DELETION REQUEST

NBAP_RL_DEL_RSP RADIO LINK DELETION RESPONSE

Iu

RANAP_INITIAL_UE_MES

SAGEINITIAL UE MESSAGE

RANAP_COMMON_ID COMMON ID

RANAP_DIRECT_TRANSF

ER DIRECT TRANSFER

RANAP_IU_RELEASE_CO

MMANDIU RELEASE COMMAND

RANAP_IU_RELEASE_CO

MPLETEIU RELEASE COMPLETE

Procedure

Step 1 Create a Uu tracing task by referring to Creating an RNC Tracing Task .

Figure 4-2 shows an example of Uu signaling tracing result.


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Figure 4-2 Example of Uu signaling tracing result

Step 2 Create an Iub tracing task by referring to Creating an RNC Tracing Task .

Figure 4-3 shows an example of Iub signaling tracing result.

Figure 4-3 Example of Iub signaling tracing result

Step 3 Create an Iu tracing task by referring to Creating an RNC Tracing Task .

Figure 4-4 shows an example of Iu signaling tracing result.

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Figure 4-4 Example of Iu signaling tracing result

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4.5 Elementary Procedures of Location Update

This part describes the elementary procedures of location update in terms of triggering conditions

and signaling procedures in normal and abnormal conditions.

4.5.1 RRC Connection Setup Procedure

The RRC connection setup procedure is performed for the UE to set up a signaling connection

to the SRNC. RRC connection setup is always initiated by the UE. One UE has a maximum of

one RRC connection at a time.

4.5.2 Location Update Procedure

The location update procedure is performed to update the location of a UE.

4.5.3 Iu Release Procedure

The Iu release procedure is performed for the CN to release an Iu connection and all the UMTS

Terrestrial Radio Access Network (UTRAN) resources related only to that Iu connection.

4.5.4 RRC Connection Release Procedure

The RRC connection release procedure is performed to release the signaling connection and all

radio bearers between the UE and the UTRAN.

4.5.1 RRC Connection Setup Procedure

The RRC connection setup procedure is performed for the UE to set up a signaling connection

to the SRNC. RRC connection setup is always initiated by the UE. One UE has a maximum of

one RRC connection at a time.

Triggering Conditions

The UE in idle mode shall initiate the RRC connection setup procedure when the NAS of theUE requests the establishment of a signaling connection.


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Procedure

When the SRNC receives an RRC CONNECTION REQUEST message from the UE, the Radio

Resource Management (RRM) module of the RNC determines whether to accept or reject the

RRC connection request according to a specific algorithm. If accepting the request, the RRM

module determines whether to set up the RRC connection on a Dedicated Channel (DCH) or on

a Common Channel (CCH) according to a specific RRM algorithm. Typically, an RRC

connection is set up on the DCH.

I. RRC Connection Setup on a DCH

Figure 4-5 shows the procedure for setting up an RRC connection on a DCH.

Figure 4-5 RRC connection setup procedure (on a DCH)

The procedure shown in Figure 4-5 is described as follows:

1. The UE sends an RRC CONNECTION REQUEST message to the SRNC through the

uplink Common Control Channel (CCCH), requesting the establishment of an RRC

connection.

2. Based on the cause in the RRC connection request and the system resource status, the SRNC

determines to set up the RRC connection on a DCH and allocates the Radio Network

Temporary Identity (RNTI), radio resources, and L1 and L2 resources.

3. The SRNC sends a RADIO LINK SETUP REQUEST message to the NodeB, requesting

the NodeB to allocate the specific radio link resources required for an RRC connection.

4. The NodeB responds with a RADIO LINK SETUP RESPONSE message to the SRNC

after successfully preparing the resources.

5. The SRNC uses the ALCAP protocol to set up the Iub user plane transport bearer and

performs the synchronization between the SRNC and the NodeB.

6. The SRNC sends an RRC CONNECTION SETUP message to the UE through the downlink

CCCH. The message contains the information about the DCH allocated by the SRNC.

7. The UE sends an RRC CONNECTION SETUP COMPLETE message to the SRNC

through the uplink Dedicated Control Channel (DCCH) that is just set up.

The RRC connection setup procedure ends.

II. RRC Connection Setup on a CCH

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Figure 4-6 shows the procedure for setting up an RRC connection on a CCH.

Figure 4-6 RRC connection setup procedure (on a CCH)


1. The UE sends an RRC CONNECTION REQUEST message to the SRNC through the

uplink CCCH, requesting the establishment of an RRC connection.

2. Based on the cause in the RRC connection request and the system resource status, the SRNC

determines to set up the RRC connection on a CCH.

3. The SRNC maps the logical channel of the UE onto a CCH in the cell.

4. The SRNC sends an RRC CONNECTION SETUP message to the UE through the downlink

CCCH. The message contains the information about the CCH.

5. The UE sends an RRC CONNECTION SETUP COMPLETE message to the SRNC

through the uplink CCCH.

The RRC connection setup procedure ends.

III. RRC Connection Rejected

Figure 4-7 shows the RRC connection rejected procedure.

Figure 4-7 RRC connection rejected procedure


1. The UE sends an RRC CONNECTION REQUEST message to the SRNC through theuplink CCCH, requesting the establishment of an RRC connection.


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4. The SRNC transparently sends the contents of the DIRECT TRANSFER message to the

UE through a DOWNLINK DIRECT TRANSFER message.

5. The UE receives the LOCATION UPDATE ACCEPT information and sends an UPLINK

DIRECT TRANSFERUE message to the SRNC. The message contains the information

such as the NAS information and the CN ID.6. The SRNC transparently sends the contents of the UPLINK DIRECT TRANSFERUE

message to the CN through a DIRECT TRANSFER message. The DIRECT

TRANSFERUE message indicates TMSI REALLOCATION COMPLETE.

4.5.3 Iu Release Procedure

The Iu release procedure is performed for the CN to release an Iu connection and all the UMTS

Terrestrial Radio Access Network (UTRAN) resources related only to that Iu connection.


The Iu release procedure can be triggered in one of the following conditions:

l The transaction between the UE and the CN is complete.

l The UTRAN requests the CN to release the resources on the Iu interface by, for example,

sending an IU RELEASE REQUEST message.

l The Serving Radio Network Subsystem (SRNS) is relocated.

l The SRNS relocation is canceled after a relocation resource allocation procedure is

complete.

ProcedureFigure 4-9 shows the Iu release procedure.

Figure 4-9 Iu release procedure


1. The CN sends an IU RELEASE COMMAND message to the SRNC to initiate the Iu release procedure. The message indicates the cause for the release of the signaling connection.


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NOTE

After sending the IU RELEASE COMMAND message, the CN shall not send further RANAP

connection-oriented messages on this particular connection.

2. The SRNC releases the related UTRAN resources and then sends an IU RELEASE

COMPLETE message to the CN.

4.5.4 RRC Connection Release Procedure

The RRC connection release procedure is performed to release the signaling connection and all

radio bearers between the UE and the UTRAN.


After an RAB is released, the SRNC judges whether the RRC connection carries any other RAB

of the UE. If judging that the RRC connection does not carry any other RAB of the UE, the

SRNC initiates an RRC connection release procedure.

Procedure

According to the resource occupied by the RRC connection, there are two types of RRC

connection release procedure: release of an RRC connection from a DCH and release of an RRC

connection from a CCH.

NOTE

If an RRC connection needs to be released after an outgoing call succeeds, the RRC connection on the

DCH is released. If a radio bearer fails to be set up, the RRC connection on the CCH is released.

I. Releasing an RRC Connection from a DCH

Figure 4-10 shows the procedure for releasing an RRC connection from a DCH.

Figure 4-10 RRC connection release procedure (from a DCH)


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1. The SRNC sends an RRC CONNECTION RELEASE message to the UE through the

DCCH.

NOTE

The SRNC may send the RRC CONNECTION RELEASE message several times to increase the

probability of proper reception of the message by the UE. The RRC SNs of these messages are thesame. The number of retransmissions and the transmission intervals are determined by the SRNC. If

the SRNC does not receive an RRC CONNECTION RELEASE COMPLETE message from the UE

after sending the RRC CONNECTION RELEASE message for four times, the SRNC regards that

the UE has released the RRC connection.

2. The UE sends an RRC CONNECTION RELEASE COMPLETE message to the SRNC.

3. The SRNC sends to the NodeB a RADIO LINK DELETION REQUEST message,

requesting the NodeB to delete the radio link resources in the NodeB.

4. After releasing the resources, the NodeB sends a RADIO LINK DELETION RESPONSE

message to the SRNC.

5. The SRNC uses the ALCAP protocol to initiate an Iub user plane transport bearer release

procedure.

The RRC connection release procedure ends.

II. Releasing an RRC Connection from a CCH

Figure 4-11 shows the procedure for releasing an RRC connection from a CCH.

Figure 4-11 RRC connection release procedure (from a CCH)


1. The SRNC sends an RRC CONNECTION RELEASE message to the UE through the

CCCH.

2. The UE sends an RRC CONNECTION RELEASE COMPLETE message to the SRNC.


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Chapter 4_Location Update Procedure

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