Content for  TS 23.402  Word version:  18.3.0

This clause contains the procedure steps that vary between the GTP and PMIP variant of S5 and S8 for the TAU with MME without Serving-GW change procedure defined in clause 5.3.3.2 of TS 23.401 as well as Inter-eNodeB Handover without Servig GW change procedures as described in clauses 5.5.1.1.2 and 5.5.1.2.2 of TS 23.401. The procedure is shown in Figure 5.7.2-1. The parameters to be provided to the PGW, as described in TS 23.401, are sent by the Serving-GW via the PCRF to the PGW.

This clause contains the procedure steps that vary between the GTP and PMIP variant of S5 and S8 for the TAU with MME and Serving-GW change procedure defined in clause 5.3.3.1 of TS 23.401 as well as Inter-eNodeB Handover with CN Node Relocation described in clause 5.5.1.2 of TS 23.401. In case of a Serving-GW relocation, the target Serving-GW must establish a Gateway Control Session with the PCRF to perform policy controlled functions such as Bearer-Binding. The source Serving-GW relinquishes its Gateway Control Session with the PCRF in step B.

This procedure concerns both the non-roaming (S5) as in Figure 4.2.1-1 and roaming case (S8) as in Figure 4.2.1-2. In the roaming case, the vPCRF in the VPLMN forwards messages between the Serving-GW and the hPCRF in the HPLMN. In the case of Local Breakout as in Figure 4.2.3-4, the vPCRF also forwards messages sent between the PDN-GW and the hPCRF. In the non-roaming case, the vPCRF is not involved at all. The optional interaction steps between the gateways and the PCRF in the procedures in Figure 5.7.1-1 only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateway. Steps between A.4 and B.1 are described in clauses 5.3.3.1 and 5.5.1 of TS 23.401. Procedures on the MME for X2 and S1 handover are described in clause 5.5 of TS 23.401. If the MME receives a rejection to an S1 interface procedure (e.g. EPS bearer(s) request) from the eNodeB with an indication that an X2/S1 handover is in progress and if during the handover procedure the MME detects that the Serving-GW or/and the MME needs be relocated, the MME rejects any EPS bearer(s) request received since handover procedure started and includes an indication that the request has been temporarily rejected due to handover procedure in progress. For PMIP based S5/S8, if dynamic PCC is deployed and with Serving-GW relocation, when the Source Serving-GW receives an indication from the MME that the PCRF initiated dedicated bearer procedure was temporarily rejected due to handover, the Source Serving-GW starts a locally configured guard timer. The Source Serving-GW shall re-attempt, up to a pre-configured number of times, at expiry of the guard timer or abort the procedure if it determines that Serving-GW is relocated based on receiving the Delete Session request message from the MME.

In case of inter-RAT TAU/RAU or handovers, the Serving-GW may or may not be relocated. The PMIP based S5/S8 variants procedure steps for inter-RAT TAU/RAU or handover without Serving-GW relocation are shown in Figure 5.7.2-1 and those corresponding to a change of Serving-GW are shown in Figure 5.7.2-2. The procedures in this clause correspond to the following Figures in TS 23.401:

• Figure 5.3.3.2-1: [UTRAN Iu mode to E-UTRAN] Tracking Area Update.
• Figure 5.3.3.3-1: E-UTRAN to UTRAN/GERAN RA Update.
• Figure 5.3.3.6-1: E-UTRAN to GERAN A/Gb mode Routeing Area Update.
• Figure 5.5.2.1.3-1: E-UTRAN to UTRAN Iu mode Inter RAT HO, execution phase.
• Figure 5.5.2.2.3-1: UTRAN Iu mode to E-UTRAN Inter RAT HO, execution phase.
• Figure 5.5.2.3.3-1: E-UTRAN to GERAN A/Gb mode Inter RAT HO, execution phase.
• Figure 5.5.2.4.3-1: GERAN A/Gb mode to E-UTRAN Inter RAT HO, execution phase.

In TS 23.401, the clauses corresponding to Figure 5.7.2-1 and Figure 5.7.2-2 cover both the case of Serving-GW relocation and no Serving-GW relocation. In case of no Serving-GW relocation, Steps (A) in the above figures are between the un-changed Serving-GW and the PCRF and the Steps (B) in those figures do not apply, as shown in Figure 5.7.2-1. In case of Serving-GW relocation, Steps (A) in the above Figure are between the target Serving-GW and the PCRF and the Steps (B) is between the source Serving-GW and the PCRF, as shown in Figure 5.7.2-2. In case of no Serving-GW relocation, the S-GW signals the change of RAT to the PCRF. In addition, if the Serving-GW has received the User Location Information IE or the user CSG information from the MME, this information is also sent to the PCRF. If PCC rules provided to the PDN-GW have changed, the PCRF updates these rules at the PDN-GW. The PCRF sends the RAT Type change or User Location Information and user CSG information, if received from the Serving-GW, to the PDN-GW. The user plane already exists between the Serving-GW and the PDN-GW and remains unchanged. In case of RAU or handover to 2G/3G, user plane routing is assumed to proceed over the S4 interface towards the S2/S3 SGSN. When an inter-RAT TAU occurs, the enhanced packet core may signal this event to the PDN-GW, for example to inform the PDN-GW of a RAT type change. In the case of a PMIP-based S5 and S8, a Modify Bearer Request is not sent from the Serving-GW to the PDN-GW. Instead, the PCRF in the HPLMN reports the change of event. The PCRF signals any change in the policy resulting from the event to the PDN-GW, provisioning updated policy and charging rules. In case dynamic PCC is not deployed, a change of RAT type will not be signalled to the PDN-GW using PMIP based S5/S8 interfaces, if no change of Serving-GW has occurred.

This procedure applies to the Non-Roaming (Figure 4.2.1-1), Roaming (Figure 4.2.1-2) and Local Breakout (Figure 4.2.3-4) cases. For the Roaming and Local Breakout cases, the vPCRF forwards messages between the Serving-GW and the hPCRF. In the Local Breakout case, the vPCRF forwards messages between the PDN-GW and the hPCRF. The optional interaction steps between the gateways and the PCRF in the procedures in Figure 5.7.2-1 only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateway. If dynamic PCC is deployed and during the handover with MME relocation without serving GW relocation, when the Serving-GW receives an indication from the MME that the PCRF initiated dedicated bearer procedure was temporarily rejected due to handover, the Serving-GW starts a locally configured guard timer. The Serving-GW shall re-attempt, up to a pre-configured number of times, when it either detects that the handover is completed or failed using message reception or at expiry of the guard timer. The following procedure describes inter-RAT TAU/RAU or Handover in the case of Serving Gateway relocation for PMIP-based S5/S8.

This procedure concerns both the non-roaming (S5) as in Figure 4.2.1-1 and roaming case (S8) as in Figure 4.2.1-2. In the roaming case, the vPCRF in the VPLMN forwards messages between the Serving-GW and the hPCRF in the HPLMN. In the case of Local Breakout as in Figure 4.2.3-4, the vPCRF forwards messages sent between the PDN-GW and the hPCRF as well. In the non-roaming case, the vPCRF is not involved at all. If dynamic policy provisioning is not deployed, the optional steps in the procedure are not applied. Steps between A.4 and B.1 are described in the clauses of TS 23.401, containing the figures referenced in Figure 5.7.2-1 above.