Section: Annex F (normative): Dedicated bearer activation in combination with the default bearer activation at Attach and UE requested PDN connectivity procedures
Content: For WB-E-UTRAN, it shall be possible for the PDN GW to initiate the activation of dedicated bearers (as specified in clause 5.4.1) as part of the attach procedure (as specified in clause 5.3.2.1) or as part of the UE requested PDN connectivity procedure (as specified in clause 5.10.2) over WB-E-UTRAN. However, the result of the dedicated bearer activation procedure shall be logically separate from the Attach procedure, meaning that the result of the Attach procedure is not dependent on whether the Dedicated bearer activation procedure succeeds or not. On the other hand, the dedicated bearer activation may only be regarded as successful if the Attach procedure completes successfully. The messages of the Dedicated bearer activation can be sent together with the messages of the Attach procedure or of the UE requested PDN connectivity procedure (i.e. Attach accept or PDN Connectivity Accept), as shown in the Figure and explanation below. On the S1 and Uu interfaces the messages for the default bearer activation at Attach and UE requested PDN connectivity procedures and for the Dedicated Bearer Activation procedure are combined into a single message. If the MME has sent an Attach Accept message towards the eNodeB, and then the MME receives a Create Bearer Request before the MME receives the Attach Complete message, the MME shall wait for the Attach procedure to complete before the MME continues with Dedicated Bearer Activation procedure. It shall be possible that multiple dedicated bearers can simultaneously be activated in the signalling flow shown below. Figure F.1: Dedicated bearer activation in combination with the default bearer activation at attach or UE requested PDN connectivity NOTE 1: Parameters related to dedicated bearer activation are written in italics. Figure F.1 describes the activation of dedicated bearer(s) in combination with the default bearer activation either as part of the Attach procedure (with specific steps 1a, 7a, 10a) or as part of the UE requested PDN connectivity procedure (with specific steps 1b, 7b, 10b). The following steps below require special attention: 5. (On the P-GW-S-GW interface) Create Session Response message of the Attach procedure or UE-requested PDN connectivity procedure is combined with Create Bearer Request message of the Dedicated Bearer Activation Procedure 6. (On the S-GW-MME interface) Create Session Response message of the Attach procedure or UE-requested PDN connectivity procedure is combined with the Create Bearer Request message of the Dedicated Bearer Activation Procedure 7a. For Attach procedure: If the MME receives a Create Session Response message combined with a Create Bearer Request message, the MME shall send the S1-AP Initial Context Setup Request message to the eNodeB, including the NAS parts for both the Attach Accept message of the Attach procedure and the Bearer Setup Request of the Dedicated Bearer Activation Procedure. NOTE 2: The MME shall not send a Bearer Setup Request message of a new Dedicated Bearer Activation procedure to the eNodeB before sending the Attach Accept message of the Attach procedure to the eNodeB. If the MME has already sent the Attach Accept message of the Attach procedure to the eNodeB, the MME shall wait for the Attach Complete message to arrive before sending a separate Bearer Setup Request of a Dedicated Bearer Activation procedure. 7b. For UE requested PDN connectivity procedure: If the MME receives a Create Session Response message combined with a Create Bearer Request message, the MME shall send the S1-AP Bearer Setup Request message to the eNodeB, including the NAS parts for both the PDN Connectivity Accept message and the Bearer Setup Request of the Dedicated Bearer Activation Procedure. 8-9. The radio bearer establishment of the default and dedicated bearer(s) is performed in the same RRC message. 10a. For Attach procedure: The eNodeB sends the S1-AP Initial Context Setup Response message to the MME. The MME shall be prepared to receive this message either before or after, some or all, of the Uplink NAS Uplink Transport messages sent in step 12. 10b. For UE requested PDN connectivity procedure: The eNodeB sends the S1-AP Bearer Setup Response message to the MME. The MME shall be prepared to receive this message either before or after, some or all, of the Uplink NAS Uplink Transport messages sent in step 12. 11. For the Attach procedure: The UE sends the eNodeB a Direct Transfer message containing the Attach Complete (Session Management Response for the Default Bearer) message as response of the attach procedure, and Direct Transfer messages containing the Session Management Responses of the dedicated bearer setup procedure. For the UE requested PDN connectivity procedure: The UE NAS layer builds a PDN Connectivity Complete (Session Management Response) for the Default Bearer Activation and Dedicated Bearer Activation Procedures. The UE then sends Direct Transfer (PDN Connectivity Complete) message to the eNodeB. The NAS messages to establish the EPS bearers shall be handled individually by the UE and be sent in separate RRC Direct Transfer messages. 12. The eNodeB sends an Uplink NAS Transport message to the MME, which contains the NAS messages from the RRC message in step 11. There may be multiple Uplink NAS Transport messages when the UE sends multiple RRC messages containing NAS messages in step 11. 13. Upon reception of the response messages in both step 10 and step 12, the Modify Bearer Request message of the Attach procedure or UE requested PDN connectivity procedure is combined with the Create Bearer Response message of the Dedicated Bearer Activation Procedure. After that, the Serving GW continues with sending a Create Bearer Response message to the PDN GW.