9.1.5 Service Request and Handover Procedures

23.1393GPP3GPP system - fixed broadband access network interworkingRelease 17Stage 2TS

This clause specifies the Service Request and Handover Procedures with updating the following information to fixed broadband access network: the HeNB local IP address and the UDP port if NAT/NAPT is detected.

This clause contains the following cases:

– UE initiated Service Request( clause 5.3.4.1, TS 23.401 [2])

– X2-based handover without Serving GW relocation(clause 5.5.1.1.2, TS 23.401 [2]),

– X2-based handover with Serving GW relocation(clause 5.5.1.1.3, TS 23.401 [2]),

– S1-based handover (clause 5.5.1.2.2 , TS 23.401 [2]),

– inter-RAT Handover from UTRAN Iu Mode to E-UTRAN (clause 5.5.2.2.2, TS 23.401 [2]),

– inter-RAT handover from GERAN A/Gb Mode to E-UTRAN(clause 5.5.2.4.2, TS 23.401 [2]).

The MME shall report changes in HeNB local IP address and/or port to the PCEF/PCRF if

– the PCRF has subscribed to reporting of changes of the local H(e)NB IP address and UDP port number; and

– the UE moves from one (e)NB to a HeNB, or from one HeNB to another HeNB with the fixed network backhaul changed, or the UE moves from a HeNB to a (e)NB.

The MME does not update the PCEF/PCRF in particular when the UE enter connected mode if there is no change in HeNB local IP address and UDP port number, or when the UE enters idle mode.

If the S-GW needs to update the PCEF/PCRF (e.g. send a Modify Bearer Request over S5/S8) for any other reasons not listed above (e.g. time zone change, S-GW relocation), the S-GW shall include the current values for H(e)NB local IP address and UDP port if the UE is accessing the network from a HeNB.

This following call flow only shows the changed steps, and the steps without change can be referred to the corresponding clauses in TS 23.401 [2].

Figure 9.1.5: Service Request and Handover Procedures

1. UE initiated Service request procedure, or intra-EUTRAN Handover procedure, or inter-RAT handover is initiated, which can be referred to the descriptions of the corresponding clause4 in TS 23.401 [2].

2. This step is the same as that in TS 23.401 [2], with the addition that target HeNB includes the following additional information: the target HeNB local IP address and the UDP port if NAT/NAPT is detected in the S1 message and sends them to MME. For the service request case, the S1 message carrying the "NAS: Service request" from UE to MME is Initial UE Message; for the X2 based handover case, the S1 message is the Path Switch Request message; for the S1 based handover or the inter-RAT handover, the S1 message is the Handover Notify Message.

3. This step is the same as that in TS 23.401 [2], with the following additional information included in create session request message or Modify bearer Request message sending between MME and S-GW, and Modify Bearer Request Message sending between S-GW and P-GW (when a Modify Bearer Request message needs to be sent over S5/S8): target HeNB Local IP address and the UDP port if NAT/NAPT is detected.

4. The P-GW sends IP-CAN session modification request message to the PCRF including the Target HeNB local IP address and the UDP port if NAT/NAPT is detected as defined in TS 23.203 [4].

If the Modify bearer Request message received by P-GW in step 3 contains none of the additional information: HeNB Local IP address and the UDP port if NAT/NAPT is detected. The P-GW determines that the UE leaves femto cell and will inform this event to PCRF.

5. If the UE moves from eNB to a HeNB, the PCRF will initiate PCRF-initiated Gateway control session establishment procedure as defined in TS 23.203 [4] if the UE is the first UE attaching the target HeNB for that PCRF; if the UE moves from one HeNB to another HeNB without fixed network backhaul changed or if the UE moves to a new HeNB and there has been one Gateway Control Session for that HeNB, the PCRF will initiate Gateway control and QoS rule provisioning procedure with BPCF as defined in TS 23.203 [4]. The HeNB local IP address and the UDP port if NAT/NAPT is detected shall be included in the PCRF-Initiated Gateway control session establishment procedure and in Gateway Control and QoS rule provisioning procedure.

6. The PCRF acknowledges the IP‑CAN session modification.

7. If UE moves from one HeNB toeNB, the PCRF will terminate the old Gateway control session if this is the last UE under the source HeNB for that PCRF; if the UE moves from eNB to a HeNB, or the UE moves from one HeNB to another HeNB without fixed network backhaul changed, or there are other UEs attached the source HeNB, this step will be skipped.

8. This step can refer to the corresponding procedure as in TS 23.401 [2].

NOTE: The interaction between the BPCF and the BNG is out of scope.