8 XwAP procedures

36.4633GPPEvolved Universal Terrestrial Radio Access Network (E-UTRAN) and Wireless Local Area Network (WLAN)Release 17TSXw application protocol (XwAP)

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

8.1 Elementary procedures

In the following tables, all EPs are divided into Class 1 and Class 2 EPs.

Table 8.1-1: Class 1 Elementary Procedures

Elementary Procedure	Initiating Message	Successful Outcome	Unsuccessful Outcome
Elementary Procedure	Initiating Message	Response message	Response message
Xw Setup	Xw SETUP REQUEST	Xw SETUP RESPONSE	Xw SETUP FAILURE
WT Configuration Update	WT CONFIGURATION UPDATE	WT CONFIGURATION UPDATE ACKNOWLEDGE	WT CONFIGURATION UPDATE FAILURE
WT Status Reporting Initiation	WT STATUS REQUEST	WT STATUS RESPONSE	WT STATUS FAILURE
WT Addition Preparation	WT ADDITION REQUEST	WT ADDITION REQUEST ACKNOWLEDGE	WT ADDITION REQUEST REJECT
eNB Initiated WT Modification	WT MODIFICATION REQUEST	WT MODIFICATION REQUEST ACKNOWLEDGE	WT MODIFICATION REQUEST REJECT
WT Initiated WT Modification	WT MODIFICATION REQUIRED	WT MODIFICATION CONFIRM	WT MODIFICATION REFUSE
WT Initiated WT Release	WT RELEASE REQUIRED	WT RELEASE CONFIRM
Reset	RESET REQUEST	RESET RESPONSE
LWIP Addition Preparation	LWIP ADDITION REQUEST	LWIP ADDITION REQUEST ACKNOWLEDGE	LWIP ADDITION REQUEST REJECT
eNB Initiated LWIP Modification	LWIP MODIFICATION REQUEST	LWIP MODIFICATION REQUEST ACKNOWLEDGE	LWIP MODIFICATION REQUEST REJECT
WT Initiated LWIP Release	LWIP RELEASE REQUIRED	LWIP RELEASE CONFIRM

Table 8.1-2: Class 2 Elementary Procedures

Elementary Procedure	Initiating Message
WT Status Reporting	WT STATUS REPORT
Error Indication	ERROR INDICATION
WT Association Confirmation	WT ASSOCIATION CONFIRMATION
eNB Initiated WT Release	WT RELEASE REQUEST
eNB Initiated LWIP Release	LWIP RELEASE REQUEST

8.2 Xw Setup

8.2.1 General

The purpose of the Xw Setup procedure is to exchange application level configuration data needed for the eNB and the WT to interoperate correctly over the Xw interface. This procedure erases any existing application level configuration data in the two nodes and replaces it by the one received. This procedure also resets the Xw interface.

The procedure uses non-UE-associated signalling.

8.2.2 Successful Operation

Figure 8.2.2-1: Xw Setup, successful operation

An eNB initiates the procedure by sending the Xw SETUP REQUEST message to a candidate WT. The candidate WT replies with the Xw SETUP RESPONSE message. The candidate WT shall reply with a list of relevant WLAN identifiers.

If the WLAN Usage IE is included in the WLAN Information IE, the eNB shall consider that the relevant WLAN identifier(s) may be used for both LWA and LWIP, or for LWIP only; otherwise, the relevant WLAN identifier(s) may be used for LWA only.

If the Neighbour eNB Information IE is included in the Xw SETUP RESPONSE message, the eNB shall consider the included information as the list of eNBs to which the WT is connected.

8.2.3 Unsuccessful Operation

Figure 8.2.3-1: Xw Setup, unsuccessful operation

If the candidate WT cannot accept the setup, it shall respond with an Xw SETUP FAILURE message with an appropriate cause value.

If the Xw SETUP FAILURE message includes the Time To Wait IE the initiating eNB shall wait at least for the indicated time before reinitiating the Xw Setup procedure towards the same WT.

8.2.4 Abnormal Conditions

If the first message received for a specific TNL association is not an Xw SETUP REQUEST, Xw SETUP RESPONSE, or Xw SETUP FAILURE message, then this shall be treated as a logical error.

8.3 WT Configuration Update

8.3.1 General

The purpose of the WT Configuration Update procedure is to update application level configuration data needed for an eNB and a WT to interoperate correctly over the Xw interface.

The procedure uses non-UE-associated signalling.

8.3.2 Successful Operation

Figure 8.3.2-1: WT Configuration Update, successful operation

A WT initiates the procedure by sending a WT CONFIGURATION UPDATE message to an eNB. Such message shall include an appropriate set of up-to-date configuration data, including, but not limited to, relevant lists of added, modified and deleted WLAN identifiers that the WT has just taken into operational use.

If the Neighbour eNB Information IE is included in the WT CONFIGURATION UPDATE message, the eNB shall consider the included information as the full updated list of eNBs to which the WT is connected.

8.3.3 Unsuccessful Operation

Figure 8.3.3-1: WT Configuration Update, successful operation

If the eNB cannot accept the update, it shall respond with a WT CONFIGURATION UPDATE FAILURE message with an appropriate cause value.

If the WT CONFIGURATION UPDATE FAILURE message includes the Time To Wait IE the WT shall wait at least for the indicated time before reinitiating the WT Configuration Update procedure towards the same eNB. Both nodes shall continue to operate the Xw with their existing configuration data.

8.3.4 Abnormal Conditions

Not applicable.

8.4 WT Status Reporting Initiation

8.4.1 General

This procedure is used by an eNB to request the reporting of load measurements to a WT.

The procedure uses non-UE-associated signalling.

8.4.2 Successful Operation

Figure 8.4.2-1: WT Status Reporting Initiation procedure, successful operation

The procedure is initiated with a WT STATUS REQUEST message sent from the eNB to the WT. Upon receipt, the WT shall initiate the requested measurement according to the parameters given in the request in case the Registration Request IE is set to "start" and shall stop all measurements and terminate the reporting in case the Registration Request IE is set to “stop".

If the Registration Request IE is set to "start" then the Report Characteristics IE shall be included in WT STATUS REQUEST message.

The Report Characteristics IE indicates the type of objects WT shall perform measurements on.

For each BSS, the WT shall include in the WT STATUS REPORT message:

– the BSS Load IE, if the first bit, “BSS Load” of the Report Characteristics IE included in the WT STATUS REQUEST message is set to 1;

– the WAN Metrics IE, if the second bit, “WAN Metrics” of the Report Characteristics IE included in the WT STATUS REQUEST message is set to 1;

– the Available Channel Utilization IE, if the third bit, “Available Channel Utilization” of the Report Characteristics IE included in the WT STATUS REQUEST message is set to 1.

If the Reporting Periodicity IE is included in the WT STATUS REQUEST message, the WT shall use its value as the time interval between two subsequent WT STATUS REPORT messages.

If the WT is capable to provide all requested resource status information, it shall initiate the measurement as requested by the eNB, and respond with the WT STATUS RESPONSE message.

If the WT is capable to provide some but not all of the requested resource status information and the Partial Success Indicator IE is present in the WT STATUS REQUEST, it shall initiate the measurement for the admitted measurement objects and include the Measurement Initiation Result IE in the WT STATUS RESPONSE message.

If the WT received a WT STATUS REQUEST message which includes the Registration Request IE set to "stop", it shall ignore the Report Characteristics, the BSS To Report List, the Reporting Periodicity, and the Partial Success Indicator IEs.

8.4.3 Unsuccessful Operation

Figure 8.4.3-1: WT Status Reporting Initiation procedure, unsuccessful operation

If none of the requested measurements can be initiated, the WT shall send a WT STATUS FAILURE message. The Cause IE shall be set to an appropriate value for each requested measurement object. The eNB may include the Complete Failure Cause Information IE in the WT STATUS FAILURE message.

8.4.4 Abnormal Conditions

If the eNB does not receive either WT STATUS RESPONSE message or WT STATUS FAILURE message, the eNB may reinitiate the WT Status Reporting Initiation procedure towards the WT, provided that the content of the new WT STATUS REQUEST message is identical to the content of the previously unacknowledged WT STATUS REQUEST message.

If the eNB receives the WT STATUS RESPONSE message including the Measurement Initiation Result IE containing no admitted measurements, the eNB shall consider the procedure as failed.

If the Registration Request IE is set to "start" and the Report Characteristics IE bitmap is set to "0" (all bits are set to "0") in the WT STATUS REQUEST message, then the WT shall initiate a WT STATUS FAILURE message, the cause shall be set to appropriate value e.g. "ReportCharacteristicsEmpty".

If the Registration Request IE is set to "start" and the Reporting Periodicity IE value is not specified, then the WT shall initiate a WT STATUS FAILURE message, the cause shall be set to appropriate value e.g. "No Report Periodicity".

If the WT received a WT STATUS REQUEST message which includes the Registration Request IE set to "start" and the eNB Measurement ID IE corresponding to an existing on-going load measurement reporting, then the WT shall initiate a WT STATUS FAILURE message, the cause shall be set to appropriate value e.g. "ExistingMeasurement ID".

If the Registration Request IE is set to "stop" and the WT STATUS REQUEST message does not contain WT Measurement ID IE, the WT shall consider the procedure as failed and respond with the WT STATUS FAILURE message, the cause shall be set to appropriate value e.g. "Unknown Measurement ID".

8.5 WT Status Reporting

8.5.1 General

This procedure is initiated by the WT to report the result of measurements admitted by the WT following a successful WT Status Reporting Initiation procedure.

The procedure uses non-UE-associated signalling.

8.5.2 Successful Operation

Figure 8.5.2-1: WT Status Reporting procedure, successful operation

The WT shall report the results of the admitted measurements in the WT STATUS REPORT message. The admitted measurements are the measurements that were successfully initiated during the preceding WT Status Reporting Initiation procedure.

8.5.3 Unsuccessful Operation

Not applicable.

8.5.4 Abnormal Conditions

Not applicable.

8.6 Error Indication

8.6.1 General

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

If the error situation arises due to reception of a message which used UE-associated signalling, then the Error Indication procedure uses UE-associated signalling. Otherwise the procedure uses non UE-associated signalling.

8.6.2 Successful Operation

Figure 8.6.2-1: Error Indication procedure, eNB originated. Successful operation.

Figure 8.6.2-2: Error Indication procedure, WT originated. Successful operation.

When the conditions defined in clause 10 are fulfilled, the Error Indication procedure is initiated by an ERROR INDICATION message sent from the receiving node.

The ERROR INDICATION message shall contain at least either the Cause IE or the Criticality Diagnostics IE. In case the Error Indication procedure is triggered by UE associated signalling, the eNB UE XwAP ID IE and the WT UE XwAP ID IE shall be included in the ERROR INDICATION message. If one or both of eNB UE XwAP ID IE and the WT UE XwAP ID IE are not correct, the cause shall be set to an appropriate value, e.g., “Unknown eNB UE XwAP ID”, “Unknown WT UE XwAP ID” or “Unknown pair of UE XwAP ID”.

8.6.3 Unsuccessful Operation

Not applicable.

8.6.4 Abnormal Conditions

Not applicable.

8.7 Reset

8.7.1 General

The purpose of the Reset procedure is to align the resources in the eNB and in the WT in the event of an abnormal failure. The procedure resets the Xw interface. This procedure does not affect the application level configuration data exchanged during, e.g., the Xw Setup procedure.

The procedure uses non UE-associated signalling.

8.7.2 Successful Operation

Figure 8.7.2-1: Reset, eNB-initiated. Successful operation.

Figure 8.7.2-2: Reset, WT-initiated. Successful operation.

The procedure is initiated with a RESET message sent from the initiating node. Upon receipt of this message, the receiving node shall abort any other ongoing procedures (except another Reset procedure) over Xw with the initiating node. The receiving node shall delete all the context information related to the initiating node, except the application level configuration data exchanged during Xw Setup or WT Configuration Update procedures, and release the corresponding resources. After completing the release of the resources, the receiving node shall respond with a RESET RESPONSE message.

8.7.3 Unsuccessful Operation

Not applicable.

8.7.4 Abnormal Conditions

If Reset procedure is ongoing and the receiving node receives the RESET message from the peer entity on the same Xw interface, the receiving node shall respond with the RESET RESPONSE message as described in 8.7.2.

8.8 WT Addition Preparation

8.8.1 General

The purpose of the WT Addition Preparation procedure is to request the WT to allocate resources for LWA operation for a specific UE.

The procedure uses UE-associated signalling and, in case of successful operation, establishes a new UE-associated logical Xw-connection.

8.8.2 Successful Operation

Figure 8.8.2-1: WT Addition Preparation, successful operation

The eNB initiates the procedures by sending the WT ADDITION REQUEST message to the WT.

The allocation of resources according to the values of the Allocation and Retention Priority IE included in the E-RAB Level QoS Parameters IE shall follow the principles described for the E-RAB Setup Procedure in TS 36.413 [8].

NOTE: Due to inherent features of the WLAN radio interface, it may not always be possible to guarantee a bit rate. If the GBR QoS Information IE is present in the WT ADDITION REQUEST, the WT may accept the request even though it may not be able to guarantee the bit rate signalled in the GBR QoS Information IE. The eNB may therefore need to monitor the bit rate of offloaded GBR bearers.

If the WT ADDITION REQUEST message contains the Serving PLMN IE, the WT may take it into account for the allocation of resources for LWA.

If the WT ADDITION REQUEST message contains the WT UE XwAP ID IE, the WT shall use the included information to identify the UE.

If the DRB-Identity IE is present in an item in the E-RABs To Be Added List IE in the WT ADDITION REQUEST message, the WT shall consider that the respective LWA bearer is configured for uplink.

At reception of the WT ADDITION REQUEST message the WT shall:

– use the information included in the Mobility Set IE as the WLAN Mobility Set configured for LWA, as defined in TS 36.300 [2];

– store the WLAN Security Information IE, if included, and use it to establish the required security relation towards the UE.

The WT shall report to the eNB, in the WT ADDITION REQUEST ACKNOWLEDGE message, the result for all the requested E-RABs in the following way:

– A list of E-RABs which are successfully established shall be included in the E-RABs Admitted To Be Added List IE.

– A list of E-RABs which failed to be established shall be included in the E-RABs Not Admitted List IE.

For each admitted uplink E-RAB to be added, the WT may include the LWA WLAN AC IE in the WT ADDITION REQUEST ACKNOWLEDGE message, and, if included, the eNB shall use the respective information as the LWA WLAN Access Category to be forwarded to the UE, as specified in TS 36.300 [2].

If the WT ADDITION REQUEST ACKNOWLEDGE message contains the WT MAC Address IE, the eNB shall, if supported, communicate this information to the UE.

8.8.3 Unsuccessful Operation

Figure 8.8.3-1: WT Addition Preparation, unsuccessful operation

If the WT is not able to accept at least one of the bearers or a failure occurs during the WT Addition Preparation, the WT sends the WT ADDITION REQUEST REJECT message with an appropriate cause value to the eNB.

8.8.4 Abnormal Conditions

If the WT receives a WT ADDITION REQUEST message containing multiple E-RAB ID IEs (in the E-RABs To Be Added List IE) set to the same value, the WT shall consider the establishment of the corresponding E-RAB as failed.

If the WT receives a WT ADDITION REQUEST message containing an E-RAB Level QoS Parameters IE which contains a QCI IE indicating a GBR bearer (as defined in TS 23.203 [13]), and which does not contain the GBR QoS Information IE, the WT shall consider the establishment of the corresponding E-RAB as failed.

If the WT receives a WT ADDITION REQUEST message containing the WT UE XwAP ID IE but it is not able to identify the UE, it shall reply with the WT ADDITION REQUEST REJECT message with an appropriate cause value.

8.9 eNB Initiated WT Modification

8.9.1 General

This procedure is used to enable an eNB to request a WT to modify the UE context at the WT.

The procedure uses UE-associated signalling.

8.9.2 Successful Operation

Figure 8.9.2-1: eNB initiated WT Modification, successful operation

The eNB initiates the procedure by sending the WT MODIFICATION REQUEST message to the WT.

The WT MODIFICATION REQUEST message may contain within the UE Context Information IE:

– E-RABs to be added within the E-RABs To Be Added Item IE;

– E-RABs to be modified within the E-RABs To Be Modified Item IE;

– E-RABs to be released within the E-RABs To Be Released Item IE;

– WLAN security information in the WLAN Security Information IE.

If the WLAN Security Information IE is included in the WT MODIFICATION REQUEST message the WT shall store the information contained in this IE, and use it to establish the required security relation towards the UE.

NOTE: Due to inherent features of the WLAN radio interface, it may not always be possible to guarantee a bit rate. If the GBR QoS Information IE is present in the WT MODIFICATION REQUEST, the WT may accept the request even though it may not be able to guarantee the bit rate signalled in the GBR QoS Information IE. The eNB may therefore need to monitor the bit rate of offloaded GBR bearers.

If the DRB-Identity IE is present in an item in the E-RABs To Be Added List IE in the WT MODIFICATION REQUEST message, the WT shall consider that the respective LWA bearer is configured for uplink.

If the WT MODIFICATION REQUEST message contains the Serving PLMN IE, the WT may take it into account for the allocation of resources for LWA.

If at least one of the requested modifications is admitted by the WT, the WT shall modify the related part of the UE context accordingly and send the WT MODIFICATION REQUEST ACKNOWLEDGE message back to the eNB.

The WT shall include the E-RABs for which resources have been either added or modified or released at the WT either in the E-RABs Admitted To Be Added List IE or the E-RABs Admitted To Be Modified List IE or the E-RABs Admitted To Be Released List IE. The WT shall include the E-RABs that have not been admitted in the E-RABs Not Admitted List IE with an appropriate cause value.

For each admitted uplink E-RAB to be added or modified, the WT may include the LWA WLAN AC IE in the WT MODIFICATION REQUEST ACKNOWLEDGE message, and, if included, the eNB shall use the respective information as the LWA WLAN Access Category to be forwarded to the UE, as specified in TS 36.300 [2].

For each E-RAB to be modified, if the WT MODIFICATION REQUEST message includes the eNB GTP Tunnel Endpoint IE in the E-RABs To Be Modified Item IE, the WT shall act as specified in TS 36.300 [2].

For each E-RAB to be released, if the DL Forwarding GTP Tunnel Endpoint IE is included within the E-RABs To Be Released Item IE in the WT MODIFICATION REQUEST message, the WT may perform data forwarding of downlink packets for that bearer.

If the E-RAB level QoS parameter IE is included in the WT MODIFICATION REQUEST message for an E-RAB to be modified, the WT shall allocate respective resources as described in TS 36.300 [2].

For an E-RAB to be modified, the WT may include in the WT MODIFICATION REQUEST ACKNOWLEDGE message the WT GTP Tunnel Endpoint IE.

If the Mobility Set IE is included in the WT MODIFICATION REQUEST message, the WT shall use the information included in this IE as the WLAN Mobility Set configured for LWA, as defined in TS 36.300 [2].

8.9.3 Unsuccessful Operation

Figure 8.9.3-1: eNB initiated WT Modification, unsuccessful operation

If the WT does not admit any modification requested by the eNB, or a failure occurs during the eNB initiated WT Modification, the WT shall send the WT MODIFICATION REQUEST REJECT message to the eNB. The message shall contain the Cause IE with an appropriate value.

8.9.4 Abnormal Conditions

If the WT receives a WT MODIFICATION REQUEST message containing multiple E-RAB ID IEs (in the E-RABs To Be Added List IE and/or the E-RABs To Be Modified List IE) set to the same value, the WT shall not admit the action requested for the corresponding E-RABs.

If the WT receives a WT MODIFICATION REQUEST message containing multiple E-RAB ID IEs (in the E-RAB To Be Released List IE) set to the same value, the WT shall initiate the release of one corresponding E-RAB and ignore the duplication of the instances of the selected corresponding E-RABs.

If the WT receives a WT MODIFICATION REQUEST message containing a E-RAB Level QoS Parameters IE which contains a QCI IE indicating a GBR bearer (as defined in TS 23.203 [13]), and which does not contain the GBR QoS Information IE, the WT shall not admit the corresponding E-RAB.

Interaction with the WT initiated WT Modification procedure:

If the eNB, after having initiated the eNB initiated WT Modification procedure, receives the WT MODIFICATION REQUIRED message, the eNB shall refuse the WT initiated WT Modification procedure with an appropriate cause value in the Cause IE.

8.10 WT Initiated WT Modification

8.10.1 General

This procedure is used by the WT to modify the UE context in the WT. In particular, in this Release of the specification, this procedure is used to request to the eNB the release of LWA bearers, or change their WT GTP Tunnel Endpoints.

The procedure uses UE-associated signalling.

8.10.2 Successful Operation

Figure 8.10.2-1: WT initiated WT Modification, successful operation

The WT initiates the procedure by sending the WT MODIFICATION REQUIRED message to the eNB.

The WT MODIFICATION REQUIRED message may contain

– E-RABs to be released within the E-RABs To Be Released Item IE;

– E-RABs to be modified within the E-RABs To Be Modified Item IE.

If the WT GTP Tunnel Endpoint IE is present in the E-RABs To Be Modified Item IE for a particular E-RAB, the eNB shall use this information to change the Xw transport bearer associated to the concerned E-RAB.

For each uplink E-RAB to be modified, the WT may include the LWA WLAN AC IE in the WT MODIFICATION REQUIRED message, and, if included, the eNB shall use the respective information as the LWA WLAN Access Category to be forwarded to the UE, as specified in TS 36.300 [2].

If the eNB is able to perform at least one of the modifications requested by the WT, the eNB shall send the WT MODIFICATION CONFIRM message to the WT with the appropriate information in the E-RABs Confirmed To Be Released List and/or E-RABs Confirmed To Be Modified List IEs. For each E-RAB to be released, if the DL Forwarding GTP Tunnel Endpoint IE is included within the E-RABs Confirmed To Be Released Item IE in the WT MODIFICATION CONFIRM message, the WT may perform data forwarding of downlink packets for that bearer.

8.10.3 Unsuccessful Operation

Figure 8.10.3-1: WT initiated WT Modification, unsuccessful operation

In case none of the requested modifications can be performed successfully the eNB shall respond with the WT MODIFICATION REFUSE message to the WT with an appropriate cause value in the Cause IE.

8.10.4 Abnormal Conditions

If the value received in the E-RAB ID IE of any of the E-RABs To Be Released Item IE or of the E-RABs To Be Modified Item IE is not known at the eNB, the eNB shall regard the procedure as failed and may take appropriate actions like triggering the eNB initiated WT Release procedure.

Interaction with the eNB initiated WT Modification Preparation procedure:

If the WT, after having initiated the WT initiated WT Modification procedure, receives the WT MODIFICATION REQUEST message, the WT shall

– regard the WT initiated WT Modification Procedure as failed,

– be prepared to receive the WT MODIFICATION REFUSE message from the eNB, and

– continue with the eNB initiated WT Modification procedure as specified in Section 8.9.

8.11 eNB Initiated WT Release

8.11.1 General

The eNB initiated WT Release procedure is triggered by the eNB to initiate the release of the resources for a specific UE.

The procedure uses UE-associated signalling.

8.11.2 Successful Operation

Figure 8.11.2-1: eNB initiated WT Release, successful operation

The eNB initiates the procedure by sending the WT RELEASE REQUEST message. Upon reception of the WT RELEASE REQUEST message the WT shall stop providing user data to the UE. The eNB may provide appropriate information within the Cause IE.

For each E-RAB, if the DL Forwarding GTP Tunnel Endpoint IE is included within the E-RABs To Be Released Item IE in the WT RELEASE REQUEST message, the WT may perform data forwarding of downlink packets for that bearer.

Upon reception of the WT RELEASE REQUEST message containing the UE Context Kept Indicator IE set to "True", the WT shall, if supported, only initiate the release of the resources related to the UE-associated signaling connection between the eNB and the WT.

8.11.3 Unsuccessful Operation

Not applicable.

8.11.4 Abnormal Conditions

Not applicable.

8.12 WT Initiated WT Release

8.12.1 General

This procedure is triggered by the WT to initiate the release of the resources for a specific UE.

The procedure uses UE-associated signalling.

8.12.2 Successful Operation

Figure 8.12.2-1: WT initiated WT Release, successful operation

The WT initiates the procedure by sending the WT RELEASE REQUIRED message to the eNB.

Upon reception of the WT RELEASE REQUIRED message, the eNB replies with the WT RELEASE CONFIRM message. For each E-RAB, if the DL Forwarding GTP Tunnel Endpoint IE is included within the E-RABs To Be Released Item IE in the WT RELEASE CONFIRM message, the WT may perform data forwarding of downlink packets for that bearer.

The WT may start data forwarding and stop providing user data to the UE upon reception of the WT RELEASE CONFIRM message.

8.12.3 Unsuccessful Operation

Not applicable.

8.12.4 Abnormal Conditions

Not applicable.

8.13 WT Association Confirmation

8.13.1 General

This procedure is initiated by the WT to give confirmation to the eNB that a certain UE successfully associated with the WLAN following a successful WT Addition Preparation procedure.

The procedure uses UE-associated signalling.

8.13.2 Successful Operation

Figure 8.13.2-1: WT Association Confirm procedure, successful operation

The WT initiates the procedure by sending the WT ASSOCIATION CONFIRMATION message to the eNB.

Upon reception of the WT ASSOCIATION CONFIRMATION message, the eNB shall consider that the UE is associated with the WLAN, and that user plane data for that UE may be sent to the WT.

8.13.3 Unsuccessful Operation

Not applicable.

8.13.4 Abnormal Conditions

Not applicable.

8.14 LWIP Addition Preparation

8.14.1 General

The purpose of the LWIP Addition Preparation procedure is to request the WT to configure tunnel resources for LWIP operation for a specific UE.

The procedure uses UE-associated signalling and, in case of successful operation, establishes a new UE-associated logical Xw-connection.

8.14.2 Successful Operation

Figure 8.14.2-1: LWIP Addition Preparation, successful operation

The eNB initiates the procedures by sending the LWIP ADDITION REQUEST message to the WT.

At reception of the LWIP ADDITION REQUEST message the WT shall use the received information to configure resources for LWIP for the UE, as defined in TS 36.300 [2].

If the LWIP ADDITION REQUEST message contains the Serving PLMN IE, the WT may take it into account for the allocation of resources for LWIP.

If the LWIP ADDITION REQUEST message contains the Mobility Set IE, the WT shall use the included information as described in TS 36.300 [2].

If the LWIP ADDITION REQUEST message contains the eNB GTP Tunnel Endpoint IE, the WT shall use the included information to configure the LWIP user plane for the UE.

The WT shall respond to the eNB with the LWIP ADDITION REQUEST ACKNOWLEDGE message.

If the LWIP-SeGW GTP Tunnel Endpoint IE is included in the LWIP ADDITION REQUEST ACKNOWLEDGE message, the eNB shall use the included information to configure the LWIP user plane for the UE.

8.14.3 Unsuccessful Operation

Figure 8.14.3-1: LWIP Addition Preparation, unsuccessful operation

If the WT is not able to configure tunnel resources for LWIP operation for the UE or a failure occurs during the LWIP Addition Preparation, the WT sends the LWIP ADDITION REQUEST REJECT message with an appropriate cause value to the eNB.

8.14.4 Abnormal Conditions

Not applicable.

8.15 eNB Initiated LWIP Modification

8.15.1 General

This procedure is used to enable an eNB to request a WT to modify the UE context for LWIP at the WT.

The procedure uses UE-associated signalling.

8.15.2 Successful Operation

Figure 8.15.2-1: eNB initiated LWIP Modification, successful operation

The eNB initiates the procedure by sending the LWIP MODIFICATION REQUEST message to the WT.

If the LWIP MODIFICATION REQUEST message contains the Serving PLMN IE, the WT may take it into account for the allocation of resources for LWIP.

If the Mobility Set IE is included in the LWIP MODIFICATION REQUEST message, the WT shall use the information included in this IE as defined in TS 36.300 [2].

If at least one of the requested modifications is admitted by the WT, the WT shall modify the related part of the UE context accordingly and send the LWIP MODIFICATION REQUEST ACKNOWLEDGE message back to the eNB.

8.15.3 Unsuccessful Operation

Figure 8.15.3-1: eNB initiated LWIP Modification, unsuccessful operation

If the WT does not admit any modification requested by the eNB, or a failure occurs during the eNB initiated LWIP Modification, the WT shall send the LWIP MODIFICATION REQUEST REJECT message to the eNB. The message shall contain the Cause IE with an appropriate value.

8.15.4 Abnormal Conditions

Not applicable.

8.16 eNB Initiated LWIP Release

8.16.1 General

The eNB initiated LWIP Release procedure is triggered by the eNB to initiate the release of tunnel resources for LWIP operation for a specific UE.

The procedure uses UE-associated signalling.

8.16.2 Successful Operation

Figure 8.16.2-1: eNB initiated LWIP Release, successful operation

The eNB initiates the procedure by sending the LWIP RELEASE REQUEST message. Upon reception of the LWIP RELEASE REQUEST message the WT shall release LWIP tunnel resources for the UE. The eNB may provide appropriate information within the Cause IE.

8.16.3 Unsuccessful Operation

Not applicable.

8.16.4 Abnormal Conditions

Not applicable.

8.17 WT Initiated LWIP Release

8.17.1 General

This procedure is triggered by the WT to initiate the release of tunnel resources for LWIP operation for a specific UE.

The procedure uses UE-associated signalling.

8.17.2 Successful Operation

Figure 8.17.2-1: WT initiated LWIP Release, successful operation

The WT initiates the procedure by sending the LWIP RELEASE REQUIRED message to the eNB.

Upon reception of the LWIP RELEASE REQUIRED message, the eNB replies with the LWIP RELEASE CONFIRM message.

The WT may stop providing user data for LWIP operation to the UE upon reception of the LWIP RELEASE CONFIRM message.

8.17.3 Unsuccessful Operation

Not applicable.

8.17.4 Abnormal Conditions

Not applicable.