8.2 E-RAB Management procedures

36.4133GPPEvolved Universal Terrestrial Radio Access Network (E-UTRAN)Release 17S1 Application Protocol (S1AP)TS

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

8.2.1 E-RAB Setup

8.2.1.1 General

The purpose of the E-RAB Setup procedure is to assign resources on Uu and S1 for one or several E-RABs and to setup corresponding Data Radio Bearers for a given UE. The procedure uses UE-associated signalling.

8.2.1.2 Successful Operation

Figure 8.2.1.2-1: E-RAB Setup procedure. Successful operation.

The MME initiates the procedure by sending an E-RAB SETUP REQUEST message to the eNB.

– The E-RAB SETUP REQUEST message shall contain the information required by the eNB to build the E-RAB configuration consisting of at least one E-RAB and for each E-RAB to setup include an E-RAB to be Setup Item IE.

Upon reception of the E-RAB SETUP REQUEST message, and if resources are available for the requested configuration, the eNB shall execute the requested E-RAB configuration. For each E-RAB and based on the E-RAB level QoS parameters IE the eNB shall establish a Data Radio Bearer and allocate the required resources on Uu. The eNB shall pass the NAS-PDU IE and the value contained in the E-RAB ID IE received for the E-RAB for each established Data Radio Bearer to the UE. The eNB does not send the NAS PDUs associated to the failed Data radio bearers to the UE. The eNB shall allocate the required resources on S1 for the E-RABs requested to be established.

If the Correlation ID IE is included in the E-RAB SETUP REQUEST message towards the eNB with L-GW function for LIPA operation, then the eNB shall use this information for LIPA operation for the concerned E-RAB.

If the SIPTO Correlation ID IE is included in the E-RAB SETUP REQUEST message towards the eNB with L-GW function for SIPTO@LN operation, then the eNB shall use this information for SIPTO@LN operation for the concerned E-RAB.

If the Bearer Type IE is included in the E-RAB SETUP REQUEST message and is set to "non IP", then the eNB shall not perform IP header compression for the concerned E-RAB.

If the Ethernet Type IE is included in the E-RAB SETUP REQUEST message and is set to "True", then the eNB shall, if supported, take this into account to perform header compression appropriately for the concerned E-RAB.

For each E-RAB for which the Security Indication IE is included in the E-RAB To Be Setup Item IEs IE of the E-RAB SETUP REQUEST message:

– if the Integrity Protection Indication IE is set to "required", then the eNB shall, if supported by the eNB and the UE, perform user plane integrity protection for the concerned E-RAB as specified in TS 33.401 [15], and otherwise it shall reject the establishment of the concerned E-RAB with an appropriate cause value.

– if the Integrity Protection Indication IE is set to "preferred", then the eNB should, if supported by the eNB and the UE, perform user plane integrity protection for the concerned E-RAB as specified in TS 33.401 [15].

– if the Integrity Protection Indication IE is set to "not needed", then the eNB shall not perform user plane integrity protection for the concerned E-RAB.

The E-RAB SETUP REQUEST message may contain

– the UE Aggregate Maximum Bit Rate IE.

If the UE Aggregate Maximum Bit Rate IE is included in the E-RAB SETUP REQUEST the eNB shall

– replace the previously provided UE Aggregate Maximum Bit Rate by the received UE Aggregate Maximum Bit Rate in the UE context;

– use the received UE Aggregate Maximum Bit Rate for non-GBR Bearers for the concerned UE.

If the UE Aggregate Maximum Bit Rate IE is not contained in the E-RAB SETUP REQUEST message, the eNB shall use the previously provided UE Aggregate Maximum Bit Rate which is stored in the UE context.

The eNB shall establish or modify the resources according to the values of the Allocation and Retention Priority IE (priority level and pre-emption indicators) and the resource situation as follows:

– The eNB shall consider the priority level of the requested E-RAB, when deciding on the resource allocation.

– The priority levels and the pre-emption indicators may (individually or in combination) be used to determine whether the E-RAB setup has to be performed unconditionally and immediately. If the requested E-RAB is marked as “may trigger pre-emption” and the resource situation requires so, the eNB may trigger the pre-emption procedure which may then cause the forced release of a lower priority E-RAB which is marked as “pre-emptable”. Whilst the process and the extent of the pre-emption procedure are operator-dependent, the pre-emption indicators shall be treated as follows:

1. The values of the last received Pre-emption Vulnerability IE and Priority Level IE shall prevail.

2. If the Pre-emption Capability IE is set to “may trigger pre-emption”, then this allocation request may trigger the pre-emption procedure.

3. If the Pre-emption Capability IE is set to “shall not trigger pre-emption”, then this allocation request shall not trigger the pre-emption procedure.

4. If the Pre-emption Vulnerability IE is set to “pre-emptable”, then this E-RAB shall be included in the pre-emption process.

5. If the Pre-emption Vulnerability IE is set to “not pre-emptable”, then this E-RAB shall not be included in the pre-emption process.

6. If the Priority Level IE is set to “no priority” the given values for the Pre-emption Capability IE and Pre-emption Vulnerability IE shall not be considered. Instead the values “shall not trigger pre-emption” and “not pre-emptable” shall prevail.

– The E-UTRAN pre-emption process shall keep the following rules:

1. E-UTRAN shall only pre‑empt E-RABs with lower priority, in ascending order of priority.

2. The pre-emption may be done for E-RABs belonging to the same UE or to other UEs.

The eNB shall report to the MME, in the E-RAB SETUP RESPONSE message, the result for all the requested E-RABs.

– A list of E-RABs which are successfully established shall be included in the E-RAB Setup List IE.

– A list of E-RABs which failed to be established, if any, shall be included in the E-RAB Failed to Setup List IE.

In case of the establishment of an E-RAB the EPC must be prepared to receive user data before the E-RAB SETUP RESPONSE message has been received.

When the eNB reports unsuccessful establishment of an E-RAB, the cause value should be precise enough to enable the MME to know the reason for an unsuccessful establishment, e.g., “Radio resources not available”, “Failure in the Radio Interface Procedure”.

Interactions with Handover Preparation procedure:

If a handover becomes necessary during E-RAB Setup, the eNB may interrupt the ongoing E-RAB Setup procedure and initiate the Handover Preparation procedure as follows:

1. The eNB shall send the E-RAB SETUP RESPONSE message in which the eNB shall indicate, if necessary

– all the E-RABs fail with an appropriate cause value, e.g., ”S1 intra system Handover triggered”, “S1 inter system Handover triggered” or “X2 Handover triggered”.

2. The eNB shall trigger the handover procedure.

8.2.1.3 Unsuccessful Operation

The unsuccessful operation is specified in the successful operation section.

8.2.1.4 Abnormal Conditions

If the eNB receives a E-RAB SETUP 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 eNB shall consider the establishment of the corresponding E-RAB as failed.

If the eNB receives an E-RAB SETUP REQUEST message containing several E-RAB ID IEs (in the E-RAB To Be Setup List IE) set to the same value, the eNB shall report the establishment of the corresponding E-RABs as failed in the E-RAB SETUP RESPONSE with the appropriate cause value, e.g., “Multiple E-RAB ID instances”.

If the eNB receives an E-RAB SETUP REQUEST message containing a E-RAB ID IE (in the E-RAB To Be Setup List IE) set to the value that identifies an active E-RAB (established before the E-RAB SETUP REQUEST message was received), the eNB shall report the establishment of the new E-RAB as failed in the E-RAB SETUP RESPONSE with the appropriate cause value, e.g., “Multiple E-RAB ID instances”.

If the eNB receives an E-RAB SETUP REQUEST message containing both the Correlation ID and the SIPTO Correlation ID IEs for the same E-RAB, the eNB shall consider the establishment of the corresponding E-RAB as failed.

8.2.2 E-RAB Modify

8.2.2.1 General

The purpose of the E-RAB Modify procedure is to enable modifications of already established E-RABs for a given UE. The procedure uses UE-associated signalling.

8.2.2.2 Successful Operation

Figure 8.2.2.2-1: E-RAB Modify procedure. Successful operation.

The MME initiates the procedure by sending an E-RAB MODIFY REQUEST message to the eNB.

– The E-RAB MODIFY REQUEST message shall contain the information required by the eNB to modify one or several E-RABs of the existing E-RAB configuration.

Information shall be present in the E-RAB MODIFY REQUEST message only when any previously set value for the E-RAB configuration is requested to be modified.

Upon reception of the E-RAB MODIFY REQUEST message, and if resources are available for the requested target configuration, the eNB shall execute the modification of the requested E-RAB configuration. For each E-RAB that shall be modified and for which the Transport Information IE is not included and based on the new E-RAB level QoS parameters IE the eNB shall modify the Data Radio Bearer configuration and change allocation of resources on Uu according to the new resource request. The eNB shall pass the NAS-PDU IE received for the E-RAB to the UE when modifying the Data Radio Bearer configuration. The eNB does not send the NAS PDUs associated to the failed Data radio bearers to the UE. The eNB shall change allocation of resources on S1 according to the new resource request.

If the E-UTRAN failed to modify an E-RAB the E-UTRAN shall keep the E-RAB configuration as it was configured prior the E-RAB MODIFY REQUEST.

The E-RAB MODIFY REQUEST message may contain the

– the UE Aggregate Maximum Bit Rate IE,

– the Secondary RAT Data Usage Request IE.

If the UE Aggregate Maximum Bit Rate IE is included in the E-RAB MODIFY REQUEST, the eNB shall

– replace the previously provided UE Aggregate Maximum Bit Rate by the received UE Aggregate Maximum Bit Rate in the UE context;

– use the received UE Aggregate Maximum Bit Rate for non-GBR Bearers for the concerned UE.

If the UE Aggregate Maximum Bit Rate IE is not contained in the E-RAB MODIFY REQUEST message, the eNB shall use the previously provided UE Aggregate Maximum Bit Rate which is stored in the UE context.

The modification of resources according to the values of the Allocation and Retention Priority IE shall follow the principles described for the E-RAB Setup procedure.

If the Transport Information IE is included in the E-RAB MODIFY REQUEST message, the eNB shall use the included information as the new S-GW address and uplink packet destination for the relevant E-RAB as defined in TS 23.401 [11], and it shall ignore the E-RAB Level QoS Parameters and NAS-PDU IEs for the same E-RAB.

The eNB shall report to the MME, in the E-RAB MODIFY RESPONSE message, the result for all the requested E-RABs to be modified.

– A list of E-RABs which are successfully modified shall be included in the E-RAB Modify List IE.

– A list of E-RABs which failed to be modified, if any, shall be included in the E-RAB Failed to Modify List IE.

When the eNB reports unsuccessful modification of an E-RAB, the cause value should be precise enough to enable the MME to know the reason for an unsuccessful modification, e.g., “Radio resources not available”, “Failure in the Radio Interface Procedure”.

In case of a modification of an E-RAB the EPC must be prepared to receive user data according to the modified E-RAB profile prior to the E-RAB MODIFY RESPONSE message.

If the Secondary RAT Data Usage Request IE set to "requested" was included in the E-RAB MODIFY REQUEST message, and the eNB supports EN-DC, LAA, LWA or LWIP and has secondary RAT usage data to report, then the Secondary RAT Usage Report List IE shall be included in the E-RAB MODIFY RESPONSE message.

Interactions with Handover Preparation procedure:

If a handover becomes necessary during E-RAB modify, the eNB may interrupt the ongoing E-RAB Modify procedure and initiate the Handover Preparation procedure as follows:

1. The eNB shall send the E-RAB MODIFY RESPONSE message in which the eNB shall indicate, if necessary

– all the E-RABs fail with an appropriate cause value, e.g., “S1 intra system Handover triggered”, “S1 inter system Handover triggered” or “X2 Handover triggered”.

2. The eNB shall trigger the handover procedure.

8.2.2.3 Unsuccessful Operation

The unsuccessful operation is specified in the successful operation section.

8.2.2.4 Abnormal Conditions

If the eNB receives a E-RAB MODIFY 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]) for a E-RAB previously configured as a non-GBR bearer (as defined in TS 23.203 [13]), and which does not contain the GBR QoS Information IE, the eNB shall consider the modification of the corresponding E-RAB as failed.

If the eNB receives an E-RAB MODIFY REQUEST message containing several E-RAB ID IEs (in the E-RAB to be Modified List IE) set to the same value, the eNB shall report the modification of the corresponding E-RABs as failed in the E-RAB MODIFY RESPONSE with the appropriate cause value, e.g., “Multiple E-RAB ID instances”.

If the eNB receives an E-RAB MODIFY REQUEST message containing some E-RAB ID IEs that eNB does not recognize, the eNB shall report the corresponding invalid E-RABs as failed in the E-RAB MODIFY RESPONSE with the appropriate cause value, e.g., “Unknown E-RAB ID”.

8.2.3 E-RAB Release

8.2.3.1 General

The purpose of the E-RAB Release procedure is to enable the release of already established E-RABs for a given UE. The procedure uses UE-associated signalling.

8.2.3.2 Successful Operation

8.2.3.2.1 E-RAB Release – MME initiated

Figure 8.2.3.2.1-1: E-RAB Release procedure. Successful operation.

The MME initiates the procedure by sending an E-RAB RELEASE COMMAND message.

The E-RAB RELEASE COMMAND message shall contain the information required by the eNB to release at least one E-RAB in the E-RAB To Be Released List IE. If a NAS-PDU IE is contained in the message, the eNB shall pass it to the UE.

Upon reception of the E-RAB RELEASE COMMAND message, the eNB shall execute the release of the requested E-RABs. For each E-RAB to be released the eNB shall release the corresponding Data Radio Bearer and release the allocated resources on Uu. The eNB shall pass the value contained in the E-RAB ID IE received for the E-RAB to the radio interface protocol for each Data Radio Bearer to be released. The eNB shall release allocated resources on S1 for the E-RABs requested to be released.

The E-RAB RELEASE COMMAND message may contain

– the UE Aggregate Maximum Bit Rate IE.

If the UE Aggregate Maximum Bit Rate IE is included in the E-RAB RELEASE COMMAND the eNB shall

– replace the previously provided UE Aggregate Maximum Bit Rate by the received UE Aggregate Maximum Bit Rate in the UE context; the eNB shall use the received UE Aggregate Maximum Bit Rate for non-GBR Bearers for the concerned UE.

If the UE Aggregate Maximum Bit Rate IE is not contained in the E-RAB RELEASE COMMAND message, the eNB shall use the previously provided UE Aggregate Maximum Bit Rate which is stored in the UE context.

The eNB shall report to the MME, in the E-RAB RELEASE RESPONSE message, the result for all the E-RABs to be released.

– A list of E-RABs which are released successfully shall be included in the E-RAB Release List IE.

– A list of E-RABs which failed to be released, if any, shall be included in the E-RAB Failed to Release List IE.

The eNB shall be prepared to receive an E-RAB RELEASE COMMAND message on an established UE-associated logical S1-connection containing an E-RAB Release List IE at any time and shall always reply to it with an E-RAB RELEASE RESPONSE message.

The eNB shall, if supported, report in the E-RAB RELEASE RESPONSE message location information of the UE in the User Location Information IE.

After sending an E-RAB RELEASE RESPONSE message containing an E-RAB ID within the E-RAB Release List IE, the eNB shall be prepared to receive an E-RAB SETUP REQUEST message requesting establishment of an E-RAB with this E-RAB ID.

If the User Location Information IE is included in the E-RAB RELEASE RESPONSE message, the MME shall handle this information as specified in TS 23.401 [11].

If the Secondary RAT Usage Report List IE is included in the E-RAB RELEASE RESPONSE message, the MME shall handle this information as specified in TS 23.401 [11].

8.2.3.2.2 E-RAB Release Indication – eNB initiated

Figure 8.2.3.2.2-1: E-RAB Release INDICATION procedure. Successful operation.

The eNB initiates the procedure by sending an E-RAB RELEASE INDICATION message towards the MME.

The E-RAB RELEASE INDICATION message shall contain at least one E-RAB released at the eNB, in the E-RAB Released List IE.

The eNB shall, if supported, report in the E-RAB RELEASE INDICATION message location information of the UE in the User Location Information IE.

Upon reception of the E-RAB RELEASE INDICATION message the MME shall normally initiate the appropriate release procedure on the core network side for the E-RABs identified in the E-RAB RELEASE INDICATION message.

If the User Location Information IE is included in the E-RAB RELEASE INDICATION message, the MME shall handle this information as specified in TS 23.401 [11].

If the Secondary RAT Usage Report List IE is included in the E-RAB RELEASE INDICATION message, the MME shall handle this information as specified in TS 23.401 [11].

Interaction with UE Context Release Request procedure:

If the eNB wants to remove all remaining E-RABs, e.g., for user inactivity, the UE Context Release Request procedure shall be used instead.

8.2.3.3 Abnormal Conditions

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

If the MME receives an E-RAB RELEASE INDICATION message containing multiple E-RAB ID IEs (in the E-RAB Released List IE) set to the same value, the MME shall initiate the release of one corresponding E-RAB and ignore the duplication of the instances of the selected corresponding E-RABs.

If the eNB receives an E-RAB RELEASE COMMAND message containing some E-RAB ID IEs that eNB does not recognize, the eNB shall report the corresponding invalid E-RABs as failed in the E-RAB RELEASE RESPONSE message with the appropriate cause, e.g., “Unknown E-RAB ID”.

8.2.4 E-RAB Modification Indication

8.2.4.1 General

The purpose of the E-RAB Modification Indication procedure is to enable the eNB to request modifications of already established E-RABs for a given UE. The procedure uses UE-associated signalling.

8.2.4.2 Successful Operation

Figure 8.2.4.2-1: E-RAB Modification Indication procedure. Successful operation.

The eNB initiates the procedure by sending an E-RAB MODIFICATION INDICATION message to the MME.

The Transport Layer Address IE and DL GTP TEID IE included in the E-RAB To Be Modified Item IEs IE in the E-RAB MODIFICATION INDICATON message shall be considered by the MME as the new DL address of the E-RABs. The Transport Layer Address IE and DL GTP TEID IE included in the E-RAB Not To Be Modified Item IEs IE in the E-RAB MODIFICATION INDICATION message shall be considered by the MME as the E-RABs with unchanged DL address

If the Secondary RAT Usage Report List IE is included in the E-RAB MODIFICATION INDICATION message, the MME shall handle this information as specified in TS 23.401 [11].

The E-RAB MODIFICATION CONFIRM message shall contain the result for all the E-RABs that were requested to be modified according to the E-RAB To Be Modified Item IEs IE of the E-RAB MODIFICATION INDICATION message as follows:

– A list of E-RABs which are successfully modified shall be included in the E-RAB Modify List IE.

– A list of E-RABs which failed to be modified, if any, shall be included in the E-RAB Failed to Modify List IE.

– A list of E-RABs which are to be released, if any, shall be included in the E-RAB To Be Released List IE.

If the E-RAB Failed to Modify List IE is received in the E-RAB MODIFICATION CONFIRM message, the eNB shall either

– release all corresponding E-UTRA and E-UTRAN resources for the concerned E-RAB or

– keep the previous transport information before sending the E-RAB MODIFICATION INDICATION message unchanged for the concerned E-RAB.

If the E-RAB To Be Released List IE is received in the E-RAB MODIFICATION CONFIRM message, the eNB shall release all corresponding E-UTRA and E-UTRAN resources for the concerned E-RAB.

If the CSG Membership Info IE is included in the E-RAB MODIFICATION INDICATION message, the MME shall use the information for CSG membership verification as specified in TS 36.300 [14] and provide the result of the membership verification in the CSG Membership Status IE contained in the E-RAB MODIFICATION CONFIRM message.

If PLMN Identity IE is received in the CSG Membership Info IE in the E-RAB MODIFICATION INDICATION message, the MME shall use it for CSG membership verification as specified in TS 36.300 [14].

When the MME reports unsuccessful modification of an E-RAB, the cause value should be precise enough to enable the eNB to know the reason for an unsuccessful modification.

If the Tunnel Information for BBF IE is received in the E-RAB MODIFICATION INDICATION message, the MME shall, if supported, use it in the core network as specified in TS 23.139 [37].

If the User Location Information IE is included in the E-RAB MODIFICATION INDICATION message, the MME shall handle this information as specified in TS 23.401 [11].

Interactions with E-RAB Setup procedure or E-RAB Modify procedure:

If the E-RAB MODIFICATION INDICATION message is received by the MME during an ongoing E-RAB Setup procedure or an ongoing E-RAB Modify procedure, the MME shall proceed with the E-RAB Modification Indication procedure.

8.2.4.3 Unsuccessful Operation

The unsuccessful operation is specified in the successful operation section.

8.2.4.4 Abnormal Conditions

Interaction with UE Context Release Request procedure:

If the E-RAB MODIFICATION INDICATION message does not contain all the E-RABs previously included in the UE Context, the MME shall trigger the UE Context Release procedure.

If the E-RAB MODIFICATION INDICATION message contains several E-RAB ID IEs set to the same value, the MME shall trigger the UE Context Release procedure.

If the CSG Membership Info IE in the E-RAB MODIFICATION INDICATION message does not contain the Cell Access Mode IE set to "hybrid", the MME shall trigger the UE Context Release procedure.