Section: 5.3.8.2.1 UE-initiated Detach procedure for E-UTRAN
Content: Figure 5.3.8.2-1 shows the case when UE camps on E-UTRAN and Detach Request is sent to MME. Figure 5.3.8.2-1: UE-Initiated Detach Procedure - UE camping on E-UTRAN NOTE 1: For a PMIP-based S5/S8, procedure steps (A) are defined in TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [2]. Steps 6, 7 and 8 concern GTP based S5/S8 1. The UE sends NAS message Detach Request (GUTI, Switch Off) to the MME. This NAS message is used to trigger the establishment of the S1 connection if the UE was in ECM-IDLE mode. Switch Off indicates whether detach is due to a switch off situation or not. The eNodeB forwards this NAS message to the MME along with the TAI+ECGI of the cell which the UE is using. If the MME receives a Detach Request via a CSG cell with Switch Off parameter indicating that detach is not due to a switch off situation, and the CSG subscription for this CSG ID and associated PLMN is absent or expired, the MME shall trigger a MME-initiated Detach procedure as specified in clause 5.3.8.3. If Dual Connectivity is active for the UE, the PSCell ID shall be included in the Uplink NAS Transport that carries the Detach Request message. NOTE 2: Security procedures may be invoked if the NAS message is used to establish the S1 connection. NOTE 3: For emergency attached or RLOS attached UEs that were not successfully authenticated, security procedures are not performed. 2. If the UE has no activated PDN connection, then steps 2 to 10 are not executed. If the PLMN has configured secondary RAT usage data reporting, the MME shall wait for step 11, if applicable, and shall perform step 12 before step 2 onwards. For any PDN connection to the SCEF, the MME indicates to the SCEF that the PDN connection for the UE is no longer available according to TS 23.682[ Architecture enhancements to facilitate communications with packet data networks and applications ]  [74] and steps 2 to 10 are not executed. For PDN connections to the P-GW, the active EPS Bearers in the Serving GW regarding this particular UE are deactivated by the MME sending Delete Session Request (LBI, User Location Information (ECGI), Secondary RAT usage data, PSCell ID) per PDN connection to the Serving GW. If ISR is activated, then the Serving GW shall not release the Control Plane TEID allocated for MME/SGSN until it receives the Delete Session Request message in step 5. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. If Secondary RAT usage data report was received from RAN, the MME includes this in the Delete Session Request message. If MME has received PSCell ID from eNodeB, the MME includes it in Delete Session Request. 3. When the S-GW receives the first Delete Session Request message from the MME or SGSN in ISR activated state, the Serving GW deactivates ISR, releases the related EPS Bearer context information and responds with Delete Session Response (Cause). When the S-GW receives the Delete Session Request message from the MME or SGSN in ISR deactivated state, the Serving GW releases the related EPS Bearer context information and jumps to step 6 by sending a Delete Session Request (LBI) message per PDN connection to the PDN GW. After step 7 the Serving GW responds back to the MME/SGSN with the Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3) message. 4. If ISR is activated, MME sends Detach Indication (Cause) message to the associated SGSN. The Cause indicates complete detach. 5. The active PDP contexts in the Serving GW regarding this particular UE are deactivated by the SGSN sending Delete Session Request (LBI, CGI/SAI) per PDN connection to the Serving GW. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message. 6. If ISR is activated, Serving GW deactivates ISR. If ISR is not activated in the Serving GW, the Serving GW sends Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI), Secondary RAT usage data) per PDN connection to the PDN GW. If ISR is not activated, this step shall be triggered by step 2. This message indicates that all bearers belonging to that PDN connection shall be released. If the MME and/or SGSN sends UE's Location Information, and/or UE Time Zone Information, and/or Secondary RAT usage data in step 2 and/or step 5, the S-GW includes the User Location Information, and/or UE Time Zone, and/or User CSG Information with the least age in this message and/or Secondary RAT usage data information. 7. The PDN GW acknowledges with Delete Session Response (Cause and, optionally, APN Rate Control Status according to clause 4.7.7.3). 8. The PDN GW employs a PCEF initiated IP-CAN Session Termination Procedure as defined in TS 23.203[ Policy and charging control architecture ]  [6] with the PCRF to indicate to the PCRF that EPS Bearer is released if PCRF is applied in the network. 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]. 9. The Serving GW acknowledges with Delete Session Response (Cause and, optionally, APN Rate Control Status). 10. The SGSN sends Detach Acknowledge message to the MME (optionally APN Rate Control Status). If received, the MME stores the APN Rate Control Status in the MM context. 11. If Switch Off indicates that detach is not due to a switch off situation, the MME sends a Detach Accept to the UE. 12. The MME releases the S1-MME signalling connection for the UE by sending S1 Release Command to the eNodeB with Cause set to Detach. The details of this step are covered in the "S1 Release Procedure", as described in clause 5.3.5. NOTE 4: In the "S1 Release Procedure", if Dual Connectivity was active at the time of the release, the eNodeB includes the PSCell ID.