Section: 5.3.8.2.2 UE-initiated Detach procedure for GERAN/UTRAN with ISR activated
Content: Figure 5.3.8.2-2 shows the case when UE with ISR Activated camps on GERAN/UTRAN and Detach Request is sent to SGSN. Refer to clause 6.6.1 of TS 23.060[ General Packet Radio Service (GPRS); Service description; Stage 2 ]  [7] for the UE-initiated Detach procedure when ISR is not activated. Figure 5.3.8.2-2: UE-Initiated Detach Procedure - UE camping on GERAN/UTRAN, ISR activated 1. The UE sends NAS message Detach Request (Detach Type, P-TMSI, P-TMSI-Signature, Switch Off) to the SGSN. Detach Type indicates which type of detach is to be performed, i.e. GPRS Detach only, IMSI Detach only or combined GPRS and IMSI Detach. Switch Off indicates whether detach is due to a switch off situation or not. The Detach Request message includes P-TMSI and P-TMSI Signature. P-TMSI Signature is used to check the validity of the Detach Request message. If P-TMSI Signature is not valid or is not included, the authentication procedure should be performed. If the SGSN 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 SGSN shall trigger a SGSN-initiated Detach procedure as specified in clause 5.3.8.3A. 2. The active EPS Bearers in the Serving GW regarding this particular UE are deactivated by the SGSN sending Delete Session Request (LBI, User Location Information (CGI/SAI)) per PDN connection to the Serving GW. Because ISR is activated, then the Serving GW shall not release the Control Plan TEID allocated for MME/SGSN until it receives the Delete Session Request message in step 5. If the UE Time Zone has changed, the SGSN includes the UE Time Zone IE in this message. 3. Because the Serving GW receives this message in ISR activated state, the Serving GW deactivates ISR and acknowledges with Delete Session Response (Cause). 4. Because ISR is activated, the SGSN sends Detach Notification (Cause) message to the associated MME. Cause indicates complete detach. 5. The active PDP contexts in the Serving GW regarding this particular UE are deactivated by the MME sending Delete Session Request (LBI, ECGI) per PDN connection to the Serving GW. If the UE Time Zone has changed, the MME includes the UE Time Zone IE in this message. 6. Serving GW deactivates ISR and sends Delete Session Request (LBI, User Location Information (ECGI or CGI/SAI)) 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 in step 2 and/or step 5, the S-GW includes the User Location Information and/or UE Time Zone with the least age in this message. 7. The PDN GW acknowledges with Delete Session Response (Cause). 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). 10. The MME sends Detach Acknowledge message to the SGSN. 11. If Switch Off indicates that detach is not due to a switch off situation, the SGSN sends a Detach Accept to the UE. 12. If the MS was GPRS detached, then the 3G SGSN releases the PS signalling connection.