7 Radio Network Layer: RNSAP protocol

3GPP43.130GSM/EDGE Iur-g interfaceRelease 16Stage 2TS

7.1 General

The following sub-clauses describe the applicability of the procedures that are supported on the Iur-g interface. The actual Iur-g interface procedures are further described in 3GPP TS 25.423 [5]. These sub-clauses show those procedures integrated with procedures on other interfaces and/or events in other network entities than the BSS or the RNC.

7.2 Basic mobility procedures

7.2.1 General

The Iur-g interface has no Radio Network User Plane functionality.

In Iu mode, SBSS/SRNS relocation is performed during every Cell Update procedure. Therefore, the only state when the MS is simultaneously known by two BSSs or one BSS and one RNC is in GERAN RRC-GRA_PCH state and UTRAN URA_PCH state.

In the GERAN RRC-GRA_PCH and UTRAN URA_PCH states, the following procedures related to the mobility of the MS are supported over the Iur-g interface:

– Paging;

– Cell Update;

– Registration Area Update; and

– RRC Connection Release.

In A/Gb mode, the following procedure related to the mobility of the MS is supported over the Iur-g interface:

– Radio Resource Reserve Handover.

The following sub-clauses describe how these procedures are performed over the Iur-g interface.

Elementary procedures over the Iur-g interface that support above mentioned mobility procedures are specified in 3GPP TS 25.423 [5] and are listed in the table below categorized by Iu mode and A/Gb mode respectively:

Table 2: Iur-g basic mobility procedures

Elementary Procedure

Initiating Message

Allowed Operating Mode for BSS

Uplink Signalling Transfer

GERAN UPLINK SIGNALLING TRANSFER INDICATION

Iu mode only

Downlink Signalling Transfer

DOWNLINK SIGNALLING TRANSFER REQUEST

Iu mode only

Relocation Commit

RELOCATION COMMIT

Both Iu mode and A/Gb mode

Paging

PAGING REQUEST

Iu mode only

Enhanced Relocation Resource Reserve

ENHANCED RELOCATION RESOURCE REQUEST

A/Gb mode only

Enhanced Relocation Resource Release

ENHANCED RELOCATION RESOURCE RELEASE COMMAND

A/Gb mode only

7.2.2 Paging

The MS/UE in the RRC-GRA_PCH and URA-PCH states may receive a CN initiated paging message. The Paging Request message received by the serving node (BSS or RNC) shall trigger paging over the registration area. In case registration area consists of cells belonging to different BSS/RNC, then the RNSAP Paging procedure over the Iur-g interface is used.. This procedure is used by the SBSS/SRNC to indicate to a CBSS/CRNC that an MS shall be paged in a cell or GRA/URA that is under the control of the CBSS/CRNC.

To illustrate further the usage of this procedure the following figure describes a scenario when the MS/UE has a context active towards PS domain and paging request is issued by the CS domain.

Figure 5: Example of Paging over Iur-g

7.2.3 Cell Update

In the RRC-GRA_PCH or URA_PCH states the MS/UE may initiate the Cell Update procedure for reasons of uplink activity, whether that is an answer to a page, periodic cell update or uplink data transfer. As explained in sub-clause 4.3, a Cell Update procedure shall always trigger the SRNC/SBSS relocation. The following figure describes the signalling flow for Cell Update procedure.

Figure 6: Cell Update with Relocation (Simplified)

1. MS/UE in RRC-GRA_PCH and URA_PCH states triggers the Cell Update procedure by sending RRC CELL UPDATE message to the DBSS/DRNC.

– DBSS/DRNC will use RNSAP Uplink Signalling Transfer procedure to forward the Cell Update message to the SBSS/SRNC. The message that is used for this is GERAN Uplink Signalling Transfer Indication. The procedure and the contents of the message are described in 3GPP TS 25.423 [5]. There are two messages already defined one for FDD and one for TDD. In case of the Iur-g interface, RNSAP GERAN UPLINK SIGNALLING TRANSFER INDICATION message (GERAN message) is used.

2. Upon reception of CELL UPDATE message, the SBSS/SRNC shall trigger the SBB/SRNC relocation. Steps 4, 5, and 6 are not relevant for this discussion so they are omitted.

7. The Relocation Commit procedure is used by the source BSS/RNC to execute the relocation. This procedure is described in 3GPP TS 25.423 [5]. The procedure is triggered by the RELOCATION COMMIT message.

9. Assuming a successful relocation the former DBSS/DRNC, the SBSS/SRNC shall send the CELL UPDATE CONFIRM message to the UE/MS.

7.2.4 Registration Area Update

The MS/UE shall trigger the GRA/URA Update Procedure when there is a change in registration area, or based on the timers related to the periodic GRA/URA update. The following figure shows an example of a successful GRA/URA Update. This example assumes no SBSS/SRNC relocation.

Figure 7: GRA Update, no relocation (Simplified)

1. The MS/UE in RRC-GRA or URA_PCH states triggers the GRA/URA Update procedure by sending RRC GRA/URA UPDATE message to the DBSS/DRNC.

– The DBSS/DRNC uses RNSAP Uplink Signalling Transfer procedure to forward the GRA/URA UPDATE message to the SBSS/SRNC. The GERAN UPLINK SIGNALLING TRANSFER INDICATION message is used for this. The procedure and the contents of the message are described in 3GPP TS 25.423 [5].

2. Upon reception of the GERAN UPLINK SIGNALLING TRANSFER INDICATION message containing the RRC GRA/URA UPDATE message, the SBSS/SRNC shall include the GRA/URA UPDATE CONFIRM message and use the Downlink Signalling Transfer procedure to request the DRNC/DBSS the transfer of the message to the MS/UE. The Downlink Signalling Transfer procedure is specified in 3GPP TS 25.423 [5]and it is triggered by DOWNLINK SIGNALLING TRANSFER REQUEST message. The content of this message is specified in 3GPP TS 25.423 [5]. The content of the message should be the same in case of the Iur-g interface, except for C-Id IE. In case of a DRNC, the C-Id is used, while in case of a DBSS, the CI IE shall be used.

3. The DBSS/DRNC shall send the GRA/URA UPDATE CONFIRM message to the UE/MS.

7.2.5 RRC Connection Release

The SBSS/SRNC may trigger the RRC Connection Release procedure for an MS/UE in RRC-GRA_PCH or URA_PCH states. In order to release the RRC connection, the SBSS/SRNC shall first trigger the paging procedure. The SBSS/SRNC, in response to the Cell Update procedure, may then use the DOWNLINK SIGNALLING TRANSFER INDICATION message to relay the RRC CONNECTION RELEASE message to the MS/UE.

In addition, the SBSS/SRNC, in response to any Cell Update or GRA/URA Update procedures, may decide to trigger the release of RRC Connection. In that case the SBSS/SRNC shall use the DOWNLINK SIGNALLING TRANSFER INDICATION message to relay the RRC CONNECTION RELEASE message to the MS/UE.

7.2.6 Radio Resource Reserve Handover

7.2.6.1 General

This procedure applies to intra and inter-MSC handover in case of CS domain handover/relocation from UTRA-NTDD RNS to GERAN BSS operating in A/Gb mode and it is used on purpose to reduce the handover preparation time when an inter-system CS handover is triggered from an RNS to a BSS.

This procedure allows the SRNS to request allocation of radio resources in the TBSS for an inter-system CS handover prior to the HANDOVER REQUEST message is received from the Core Network, allowing the SRNS to start the handover command process towards the MS/UE before the reception of the RELOCATION COMMAND message from the Core Network.

7.2.6.2 Successful operation

Figure 8: Iur-g HO with radio resource reservation in the TBSS

1) After receiving the measurement report from the MS/UE and having considered the GSM neighbor cells capacity and load information, the SRNS decides to handover the MS/UE to a neighbor GSM cell.

2) An Iur-g connection is established by the SRNS towards the BSS serving the targeted neighbour GSM cell. The SRNS sends the ENHANCED RELOCATION RESOURCE REQUEST message to the TBSS in order to reserve radio resources for the MS/UE.

3) At reception of the ENHANCED RELOCATION RESOURCE REQUEST message the TBSS allocates a D-RNTI (Drift-Radio Network Temporary Identity) for the MS/UE and reserves the radio resources according to the Speech Version parameter (the MS/UE preferences for GSM). The TBSS builds the L3 Information Container IE (containing the (RR) HANDOVER COMMAND message) and sends it together with the D-RNTI IE in the ENHANCED RELOCATION RESOURCE RESPONSE message to the SRNS.

4) Receiving the ENHANCED RELOCATION RESOURCE RESPONSE message the SRNS sends the (RR) HANDOVER COMMAND message included in the L3 information container IE to the MS/UE encapsulated in the HANDOVER FROM UTRAN COMMAND message.

5) SRNS sends the RELOCATION REQUIRED message to the CN with the D-RNTI encapsulated in the Old BSS to New BSS IE.

6) The CN sends the HANDOVER REQUEST message to the TBSS with the D-RNTI encapsulated in the Old BSS to New BSS IE. The TBSS correlates the received D-RNTI in the HANDOVER REQUEST message with the D-RNTI identifying the previously reserved radio resources.

7) The TBSS sends the HANDOVER REQUEST ACKNOWLEDGE message to the CN.

8) The CN sends the RELOCATION COMMAND message to the SRNS.

9) The SRNS sends the RELOCATION COMMIT message to the TBSS for the concerned MS/UE (and D-RNTI).

10) The MS/UE is accessing the target GSM cell by sending the HANDOVER ACCESS message to the TBSS.

11) The TBSS sends the HANDOVER DETECT message to the CN since it has already received the RELOCATION COMMIT message from the SRNS. Otherwise if the RELOCATION COMMIT message for concerned MS/UE is not received in the TBSS, then the TBSS shall not send the HANDOVER DETECT message to the CN. In this case the TBSS shall wait for the RELOCATION COMMIT message before sending the HANDOVER DETECT message to the CN.

12) The MS/UE sends the HANDOVER COMPLETE message to the TBSS.

13) The TBSS forwards the message to the CN.

14) The CN sends the IU RELEASE COMMAND message to the SRNS after receiving the HANDOVER COMPLETE message.

15) After releasing the UTRAN resources and the Iur-g connection towards the TBSS, the SRNC sends the IU RELEASE COMPLETE message to the CN.

7.2.6.3 Abnormal conditions

7.2.6.3.1 BSS Radio Resource Reservation Failure

Figure 9: BSS Radio Resource Reservation Failure

1. SRNS sends the ENHANCED RELOCATION RESOURCE REQUEST message to the TBSS in order to reserve radio resources for the MS/UE.

2. If the TBSS can not reserve the requested radio resources, then the TBSS returns the ENHANCED RELOCATION RESOURCE FAILURE message to the SRNS with appropriate Cause value included in the message.

3. Upon reception of the ENHANCED RELOCATION RESOURCE FAILURE message the SRNS starts releasing the dedicated Iur-g connection towards the TBSS.

7.2.6.3.2 Handover failure from MS/UE

Figure 10: MS/UE Handover Failure

1. In case the handover process fails in the MS/UE, the MS/UE sends the HANDOVER FROM UTRAN FAILURE message to the SRNS.

2. The SRNS informs the TBSS of the handover failure by sending the ENHANCED RELOCATION RESOURCE RELEASE COMMAND message on the dedicated Iur-g connection. Upon reception of the ENHANCED RELOCATION RESOURCE RELEASE COMMAND message, the TBSS starts releasing the radio resources related to the MS/UE and returns the ENHANCED RELOCATION RESOURCE RELEASE COMPLETE message to the SRNS.

3. Upon reception of the ENHANCED RELOCATION RESOURCE RELEASE COMPLETE message, the SRNS starts releasing the dedicated Iur-g connection towards the TBSS.

7.3 Void

7.4 Global procedures

7.4.1 General

Table 3: Global procedures list

Elementary Procedure

Initiating Message

Allowed Operating Mode for BSS

Error Indication

ERROR INDICATION

Iu mode only

Common Measurement Initiation

COMMON MEASUREMENT INITIATION REQUEST

Both Iu mode and A/Gb mode

Common Measurement Reporting

COMMON MEASUREMENT REPORT

Both Iu mode and A/Gb mode

Common Measurement Termination

COMMON MEASUREMENT TERMINATION REQUEST

Both Iu mode and A/Gb mode

Common Measurement Failure

COMMON MEASUREMENT FAILURE INDICATION

Both Iu mode and A/Gb mode

Information Exchange Initiation

INFORMATION EXCHANGE INITIATION

Both Iu mode and A/Gb mode

Information Reporting

INFORMATION REPORT

Both Iu mode and A/Gb mode

Information Exchange Termination

INFORMATION EXCHANGE TERMINATION REQUEST

Both Iu mode and A/Gb mode

Information Exchange Failure

INFORMATION EXCHANGE FAILURE INDICATION

Both Iu mode and A/Gb mode

7.4.2 Error Indication

The Error Indication procedure is initiated by a node to report detected errors in a received message, provided they cannot be reported by an appropriate response message.

7.4.3 Common Measurement Functions

The Common Measurement function in the Iur-g interface is used to support the Improved RRM across BSS and BSS/RNC. This functionality is supported by adopting the Iur procedures for Common Measurements:

Common Measurement Initiation: This procedure is used by an RNC/BSS to request the initiation of measurements of common resources to another RNC/BSS. For measurements made in GERAN cells, only the following measurement types are applicable:

– Load

– RT load

– NRT load information

Common Measurement Reporting: This procedure is used by an RNC/BSS to report the result of measurements requested by another RNC using the Common Measurement Initiation.

Common Measurement Termination: This procedure is used by an RNC/BSS to terminate a measurement previously requested by the Common Measurement Initiation procedure.

Common Measurement Failure: This procedure is used by an RNC/BSS to notify another RNC/BSS that a measurement previously requested by the Common Measurement Initiation procedure can no longer be reported.

7.4.4 Information Exchange Functions

This Information Exchange functions are used to initiate, maintain and terminate information exchange between two RNC/BSS nodes. This functionality is supported by adopting the Iur procedures for Information Exchange:

– Information Exchange Initiation: This procedure is used by a BSS/RNC to request the initiation of an information exchange with another BSS/RNC. The procedure is initiated with an INFORMATION EXCHANGE INITIATION REQUEST message sent from BSS1 to BSS2/RNC2 or by RNC1 to BSS2. Upon reception, the BSS2/RNC2 shall provide the requested information according to the parameters given in the request.

– Information Reporting: This procedure is used by a BSS/RNC to report the result of information requested by another BSS/RNC using the Information Exchange Initiation.

– Information Exchange Termination: This procedure is used by a BSS/RNC to terminate the information exchange requested using the Information Exchange Initiation.

– Information Exchange Failure: This procedure is used by a BSS/RNC to notify another that the information exchange it previously requested using the Information Exchange Initiation can no longer be reported.

The information which can be requested on the Iur and Iur-g interfaces is shown in the table below marked with "X". For information which is not applicable on the Iur-g interface, the BSS shall regard the Information Exchange Initiation procedure as failed.

Table 4: Allowed Information types on Iur and Iur-g interfaces

Information Type

Interface

Iur

Iur-g

IPDL Parameters

X

DGPS Corrections

X

GPS Information

X

Cell Capacity Class

X

X

Cell capacity class for GERAN cells is defined by the number of configured carriers in specific GERAN cells which ranges from integer 1 to 100. The value 1 shall indicate the minimum cell capacity and the value 100 shall indicate the maximum cell capacity.

Annex A (Informative):
Change history

Date / TSG #

TSG Doc.

CR

Rev

Subject/Comment

New

GP-11

Conversion to Technical Specification based upon TR 43.930 v5.1.0

5.0.0

GP-23

Version for Release 6

6.0.0

GP-35

Version for Release 7

7.0.0

GP-40

Version for Release 8

8.0.0

GP-44

Version for Release 9

9.0.0

GP-49

GP-110493

0001

1

Enhancements of Iur-g interface

10.0.0

GP-55

Version for Release 11

11.0.0

GP-63

Version for Release 12 (frozen at SP-65)

12.0.0

GP-68

Version for Release 13 (frozen at SP-70)

13.0.0

Change history

Date

Meeting

TDoc

CR

Rev

Cat

Subject/Comment

New version

2017-09

RP-75

Release 14 version (frozen at TSG-75)

14.0.0

2017-09

RP-171597

0004

A

Removal of references to TS 44.118

14.1.0

2018-06

RP-80

Release 15 version (frozen at TSG-80)

15.0.0

2020-07

RP-88e

Upgrade to Rel-16 version without technical change

16.0.0