Section: 5.4.4.1 PDN GW initiated bearer deactivation
Content: The bearer deactivation procedure for a GTP based S5/S8 is depicted in figure 5.4.4.1-1. This procedure can be used to deactivate a dedicated bearer or deactivate all bearers belonging to a PDN address. If the default bearer belonging to a PDN connection is deactivated, the PDN GW deactivates all bearers belonging to the PDN connection. When the last bearer belonging to the last PDN connection of a given APN is released, the PGW may forward to the MME the APN Rate Control Status for storing it in the MM context according to clause 4.7.7.3. Figure 5.4.4.1-1: PDN GW Initiated Bearer Deactivation NOTE 1: Steps 3-8 are common for architecture variants with GTP based S5/S8 and PMIP-based S5/S8. For an PMIP-based S5/S8, procedure steps (A) and (B) are defined in TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [2]. Steps 1, 2, 9 and 10 concern GTP-based S5/S8. 1. If dynamic PCC is not deployed, the PDN GW is triggered to initiate the Bearer Deactivation procedure due either a QoS policy or on request from the MME (as outlined in clause 5.4.4.2) or on intra-node signalling request from the HeNB to release the LIPA PDN Connection. Optionally, the PCRF sends QoS policy to the PDN GW. This corresponds to the initial steps of the PCRF-initiated IP-CAN Session Modification procedure or the response to the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6], up to the point that the PDN GW requests IP-CAN Bearer Signalling. The PCC decision provision message may indicate that User Location Information and/or UE Time Zone Information is to be provided to the PCRF as defined in TS 23.203[ Policy and charging control architecture ]  [6]. If dynamic PCC is not deployed, the PDN GW may apply local QoS policy. The PDN GW initiated Bearer deactivation is also performed when handovers occur from 3GPP to non-3GPP, in which case, the default bearer and all the dedicated bearers associated with the PDN address are released, but the PDN address is kept in the PDN GW. For an emergency PDN connection the PDN GW initiates the deactivation of all bearers of that emergency PDN connection when the PDN connection is inactive (i.e. not transferring any packets) for a configured period of time or when triggered by dynamic PCC. For an PDN connection established towards the APN dedicated for Restricted Local Operator Services, the PDN GW initiates the deactivation of all bearers of the PDN connection per local operator policy e.g. when the duration of such PDN connection reaches a pre-configured period of time. 2. The PDN GW sends a Delete Bearer Request (PTI, EPS Bearer Identity, Causes and, optionally, APN Rate Control Status according to clause 4.7.7.3) message to the Serving GW. The Procedure Transaction Id (PTI) parameter in this step and in the following steps is only used when the procedure was initiated by a UE Requested Bearer Resource Modification Procedure - see clause 5.4.5. This message can include an indication that all bearers belonging to that PDN connection shall be released. The PDN GW includes 'Cause' IE in the Delete Bearer Request message and sets the IE to 'RAT changed from 3GPP to Non-3GPP' if the Delete Bearer Request message is caused by a handover from 3GPP to non-3GPP. 3a. The Serving GW sends the Delete Bearer Request (PTI, EPS Bearer Identity, Cause and, optionally, APN Rate Control Status) message to the MME. This message can include an indication that all bearers belonging to that PDN connection shall be released. 3b. If ISR is activated, the Serving GW sends the Delete Bearer Request (PTI, EPS Bearer Identity, Cause) message to the SGSN. This message can include an indication that all bearers belonging to that PDN connection shall be released, and the SGSN releases all bearer resources of the PDN connection. NOTE 2: If all the bearers belonging to a UE are released due to a handover from 3GPP to non-3GPP, the SGSN changes the MM state of the UE to IDLE (GERAN network) or PMM-DETACHED (UTRAN network). If ISR is activated, upon receiving Delete Bearer Request from SGW for the last PDN connection for a given UE, MME shall locally de-activate ISR. NOTE 3: In this case, SGSN locally de-activates ISR as well (see TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7]). If received, the MME stores the APN Rate Control Status in the MM context. Steps 4 to 7 are not performed if at least one of the following three conditions is fulfilled: (i) The UE is in ECM-IDLE and the last PDN connection of the UE is not being deleted and the Delete Bearer Request received from the Serving GW does not contain the cause "reactivation requested", which has been sent from the PDN GW; (ii) UE is in ECM-IDLE and the last PDN connection is deleted due to ISR deactivation; (iii) UE is in ECM-IDLE and the last PDN connection is deleted in 3GPP due to handover to non-3GPP access. When steps 4 to 7 are not performed, the EPS bearer state is synchronized between the UE and the network at the next ECM-IDLE to ECM-CONNECTED transition (e.g. Service Request or TAU procedure). 4a. If the last PDN connection of a UE that does not support "Attach without PDN connectivity" is being released and the bearer deletion is neither due to ISR deactivation nor due to handover to non-3GPP accesses, the MME explicitly detaches the UE by sending a Detach Request message to the UE. If the UE is in ECM-IDLE state the MME initiates paging via Network Triggered Service Request procedure in clause 5.3.4.3 from step 3a onwards in order to inform UE of the request. Steps 4b to 7b are skipped in this case, and the procedure continues from step 7c. 4b. If the UE is in ECM-IDLE state and the reason for releasing PDN connection is "reactivation requested", the MME initiates paging via Network Triggered Service Request procedure in clause 5.3.4.3 from step 3a onwards in order to inform UE of the request and step 4c is performed after completion of the paging. 4c. If the release of the bearer in E-UTRAN has already been signalled to the MME, steps 4c to 7 are omitted. Otherwise, if this is not the last PDN connection for the UE which is being released, the MME sends the S1-AP Deactivate Bearer Request (EPS Bearer Identity) message to the eNodeB. The MME builds a NAS Deactivate EPS Bearer Context Request message including the EPS Bearer Identity and a WLAN offloadability indication, and includes it in the S1-AP Deactivate Bearer Request message. When the bearer deactivation procedure was originally triggered by a UE request, the NAS Deactivate EPS Bearer Context Request message includes the PTI. The MME may include an indication whether the traffic of this PDN Connection is allowed to be offloaded to WLAN as described in clause 4.3.23 if the PDN connection is not released. 5. The eNodeB sends the RRC Connection Reconfiguration message including the EPS Radio Bearer Identity to release and the NAS Deactivate EPS Bearer Context Request message to the UE. 6a. The UE RRC releases the radio bearers indicated in the RRC message in step 5, and indicates the radio bearer status to the UE NAS. Then the UE NAS removes the UL TFTs and EPS Bearer Identity according to the radio bearer status indication from the UE RRC. The UE responds to the RRC Connection Reconfiguration Complete message to the eNodeB. 6b. The eNodeB acknowledges the bearer deactivation to the MME with a Deactivate Bearer Response (EPS Bearer Identity, ECGI, TAI, PSCell ID, Secondary RAT usage data) message. If the PLMN has configured secondary RAT usage reporting and the eNodeB has Secondary RAT usage data to report, the Secondary RAT usage data is included. The PSCell ID is included if Dual Connectivity is active for the UE in the RAN. The MME shall be prepared to receive this message either before or after the Session Management Response message sent in step 7b, and before or after, any Detach Request message sent in step 7c. 7a The UE NAS layer builds a Deactivate EPS Bearer Context Accept message including EPS Bearer Identity. The UE then sends a Direct Transfer (Deactivate EPS Bearer Context Accept) message to the eNodeB. 7b. The eNodeB sends an Uplink NAS Transport (Deactivate EPS Bearer Context Accept) message to the MME. 7c. If the UE receives the Detach Request message from the MME in the step 4a, the UE sends a Detach Accept message to the MME any time after step 4a. The eNodeB forwards this NAS message to the MME along with the TAI+ECGI of the cell which the UE is using. NOTE 4: The UE may not be able to send this message, e.g. when the UE is out of coverage of E-UTRAN due to mobility to non-3GPP access. 7a,b,c If Dual Connectivity is active for the UE, the PSCell ID shall be included in the Uplink NAS Transport sent by the eNodeB. 8a. After reception of both the Deactivate Bearer Response message in step 6b and the Deactivate EPS Bearer Context Accept message in step 7b, the MME deletes the bearer context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the Serving GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (ECGI), RAN/NAS Release Cause, Secondary RAT usage data, PSCell ID) message. If the MME received Secondary RAT usage data in step 6b, the MME shall include it in this message. If the MME received PSCell ID in step 6b, the MME shall include it in this message. If extended idle mode DRX is enabled, then the MME acknowledges the bearer deactivation to the Serving GW and at the same time the MME initiates the deactivation towards the UE. If the S1 connection had already been released by the eNodeB due to radio link failure and the MME receives a Delete Bearer Request while it is still deferring the sending of the S1 release (see clause 5.3.5), the MME shall include in the Delete Bearer Response the RAN/NAS Cause received in the S1 Release due to radio link failure procedure. 8b The SGSN deletes PDP Context related to the deactivated EPS bearer and acknowledges the bearer deactivation to the Serving GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (CGI/SAI)) message. If extended idle mode DRX is enabled, then the SGSN acknowledges the bearer deactivation to the Serving GW and at the same time the SGSN initiates the deactivation towards the UE. 9. If ISR is activated, after receiving the two Delete Bearer Response messages from the MME and the SGSN, or if ISR is not activated, after receiving the Delete Bearer Response messages from the MME, the Serving GW deletes the bearer context related to the deactivated EPS bearer acknowledges the bearer deactivation to the PDN GW by sending a Delete Bearer Response (EPS Bearer Identity, User Location Information (ECGI or CGI/SAI), Secondary RAT usage data) message. If the MME and/or SGSN sent UE's Location Information and/or UE Time Zone in step 8a and/or step 8b, the Serving GW includes the User Location Information and/or UE Time Zone Information with the least age in this message. The Serving GW includes the Secondary RAT usage data if it was received in step 8a and if PGW secondary RAT usage data reporting is active. 10. The PDN GW deletes the bearer context related to the deactivated EPS bearer. If the dedicated bearer deactivation procedure was triggered by receiving a PCC decision message from the PCRF, the PDN GW indicates to the PCRF whether the requested PCC decision was successfully enforced by completing the PCRF-initiated IP-CAN Session Modification procedure or the PCEF initiated IP-CAN Session Modification procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6], proceeding after the completion of IP-CAN bearer signalling. If requested by the PCRF the PDN GW indicates User Location Information and/or UE Time Zone Information to the PCRF as defined in TS 23.203[ Policy and charging control architecture ]  [6]. If available, the PDN GW shall send RAN/NAS Release Cause to the PCRF as defined in TS 23.203[ Policy and charging control architecture ]  [6]. 11. If the UE is being explicitly detached, the MME releases the S1-MME signalling connection for the UE by sending an S1 Release Command (Cause) message to the eNodeB. The details of this step are covered in the "S1 Release Procedure", as described in clause 5.3.5 by step 4 to step 6. NOTE 5: In the "S1 Release Procedure", if Dual Connectivity was active at the time of the release, the eNodeB includes the PSCell ID. NOTE 6: The exact signalling of step 1 and 10 (e.g. for local break-out) is outside the scope of this specification. This signalling and its interaction with the dedicated bearer activation procedure are to be specified in TS 23.203[ Policy and charging control architecture ]  [6]. Steps 1 and 10 are included here only for completeness. If all the bearers belonging to a UE that does not support "Attach without PDN connectivity" are released, the MME shall change the MM state of the UE to EMM-DEREGISTERED and the MME sends the S1 Release Command to the eNodeB, which initiates the release of the RRC connection for the given UE if it is not released yet, and returns an S1 Release Complete message to the MME. If all bearers of an emergency attached or RLOS attached UE are deactivated the MME may initiate the explicit MME-Initiated Detach procedure. Regardless of the outcome of any explicit Detach procedure the MME changes the EMM state of the UE to EMM-DEREGISTERED and the MME sends the S1 Release Command to the eNodeB if it is not yet released. If the default bearer belonging to a PDN connection is deactivated, the MME determines the Maximum APN Restriction for the remaining PDN connections and stores this new value for the Maximum APN Restriction. In addition if ISR is activated the SGSN determines the Maximum APN Restriction for the remaining bearer contexts and stores this new value for the Maximum APN Restriction.