Content for  TS 23.401  Word version:  19.0.0

If dynamic PCC is deployed, the PCRF sends a PCC decision provision (QoS policy) message to the PDN-GW. This corresponds to the initial steps of the PCRF-Initiated IP-CAN Session Modification procedure or to the PCRF response in the PCEF-initiated IP-CAN Session Modification procedure as defined in TS 23.203, 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. If dynamic PCC is not deployed, the PDN-GW may apply local QoS policy.

The PDN-GW uses this QoS policy to assign the EPS Bearer QoS, i.e., it assigns the values to the bearer level QoS parameters QCI, ARP, GBR and MBR; see clause 4.7.3. If this dedicated bearer is created as part of the handover procedure from non-3GPP access with GTP-based S2a/S2b, then the PDN-GW applies the Charging Id already in use for the corresponding dedicated bearer while the UE was in non-3GPP access (i.e bearer with the same QCI and ARP as in non-3GPP access). Otherwise, the PDN-GW generates a Charging Id for the dedicated bearer. The PDN-GW sends a Create Bearer Request message (IMSI, PTI, EPS Bearer QoS, Maximum Packet Loss Rate (UL, DL), TFT, S5/S8 TEID, Charging Id, LBI, Protocol Configuration Options) to the Serving-GW, the Linked EPS Bearer Identity (LBI) is the EPS Bearer Identity of the default bearer. The Procedure Transaction Id (PTI) parameter is only used when the procedure was initiated by a UE Requested Bearer Resource Modification Procedure - see clause 5.4.5. Protocol Configuration Options may be used to transfer application level parameters between the UE and the PDN-GW (see TS 23.228), and are sent transparently through the MME and the Serving-GW. For a QCI=1 bearer, the Maximum Packet Loss Rate (UL, DL) may be provided by the PDN-GW as described in TS 23.203.

The Serving-GW sends the Create Bearer Request (IMSI, PTI, EPS Bearer QoS, Maximum Packet Loss Rate (UL, DL), TFT, S1-TEID, PDN-GW TEID (GTP-based S5/S8), LBI, Protocol Configuration Options) message to the MME. If the UE is in ECM-IDLE state the MME will trigger the Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3). In that case the following steps 4-7 may be combined into Network Triggered Service Request procedure or be performed stand-alone. The MME checks if the UE can support the establishment of additional user plane radio bearer based on the maximum number of user plane radio bearers indicated by NB-IoT UE in the UE Network Capability IE as defined in clause 5.11.3 and for WB-E-UTRAN in clause 4.12. If the UE is in ECM-IDLE state and extended idle mode DRX is enabled for the UE, the MME will trigger Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3), and start a timer which is configured to a value smaller than the GTP re-transmission timer. If the MME receives no response from the UE before the timer expires, the MME sends a Create Bearer Response with a rejection cause indicating that the UE is temporarily not reachable due to power saving and, if a Delay Tolerant Connection indication was set for the PDN connection, the MME sets the internal flag Pending Network Initiated PDN Connection Signalling. The rejection is forwarded by the Serving-GW to the PDN-GW. In this case, the steps 4-11 are skipped.

The MME selects an EPS Bearer Identity, which has not yet been assigned to the UE. The MME then builds a Session Management Request including the PTI, TFT, EPS Bearer QoS parameters (excluding ARP), Protocol Configuration Options, the EPS Bearer Identity, the Linked EPS Bearer Identity (LBI) and a WLAN offloadability indication. If the UE has UTRAN or GERAN capabilities and the network supports mobility to UTRAN or GERAN, the MME uses the EPS bearer QoS parameters to derive the corresponding PDP context parameters QoS Negotiated (R99 QoS profile), Radio Priority, Packet Flow Id and TI and includes them in the Session Management Request. If the UE indicated in the UE Network Capability it does not support BSS packet flow procedures, then the MME shall not include the Packet Flow Id. The MME then signals the Bearer Setup Request (EPS Bearer Identity, EPS Bearer QoS, Maximum Packet Loss Rate (UL, DL), Session Management Request, S1-TEID) message to the eNodeB. 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.

The eNodeB maps the EPS Bearer QoS to the Radio Bearer QoS. It then signals a RRC Connection Reconfiguration (Radio Bearer QoS, Session Management Request, EPS RB Identity) message to the UE. The UE shall store the QoS Negotiated, Radio Priority, Packet Flow Id and TI, which it received in the Session Management Request, for use when accessing via GERAN or UTRAN. The UE NAS stores the EPS Bearer Identity and links the dedicated bearer to the default bearer indicated by the Linked EPS Bearer Identity (LBI). The UE uses the uplink packet filter (UL TFT) to determine the mapping of traffic flows to the radio bearer. The UE may provide the EPS Bearer QoS parameters to the application handling the traffic flow. The application usage of the EPS Bearer QoS is implementation dependent. The UE shall not reject the RRC Connection Reconfiguration on the basis of the EPS Bearer QoS parameters contained in the Session Management Request.

The UE acknowledges the radio bearer activation to the eNodeB with a RRC Connection Reconfiguration Complete message.

The eNodeB acknowledges the bearer activation to the MME with a Bearer Setup Response (EPS Bearer Identity, S1-TEID) message. The eNodeB indicates whether the requested EPS Bearer QoS could be allocated or not. The MME shall be prepared to receive this message either before or after the Session Management Response message (sent in step 9). The PSCell ID is included if Dual Connectivity is active for the UE in the RAN.

The UE NAS layer builds a Session Management Response including EPS Bearer Identity. The UE then sends a Direct Transfer (Session Management Response) message to the eNodeB.

The eNodeB sends an Uplink NAS Transport (Session Management Response) message to the MME.

Upon reception of the Bearer Setup Response message in step 7 and the Session Management Response message in step 9, the MME acknowledges the bearer activation to the Serving-GW by sending a Create Bearer Response (EPS Bearer Identity, S1-TEID, User Location Information (ECGI), PSCell ID) message.

The Serving-GW acknowledges the bearer activation to the PDN-GW by sending a Create Bearer Response (EPS Bearer Identity, S5/S8-TEID, User Location Information (ECGI)) message.

If the dedicated bearer activation procedure was triggered by a PCC Decision Provision message from the PCRF, the PDN-GW indicates to the PCRF whether the requested PCC decision (QoS policy) could be enforced or not, allowing the completion of the PCRF-Initiated IP-CAN Session Modification procedure or the PCEF-initiated IP-CAN Session Modification procedure as defined in TS 23.203, 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. If the dedicated bearer activation is rejected with a cause indicating that the UE is temporarily not reachable due to power saving, then the PDN-GW re-attempts the same procedure after it receives the indication that the is UE available for end to end signalling in the subsequent Modify Bearer Request message.

If dynamic PCC is deployed, the PCRF sends a PCC decision provision (QoS policy) message to the PDN-GW. This corresponds to the beginning of the PCRF-initiated IP-CAN Session Modification procedure or to the PCRF response in the PCEF-initiated IP-CAN Session Modification procedure as defined in TS 23.203, 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. If dynamic PCC is not deployed, the PDN-GW may apply local QoS policy.

The PDN-GW uses this QoS policy to determine that a service data flow shall be aggregated to or removed from an active bearer. The PDN-GW generates the TFT and determines that no update of the EPS Bearer QoS is needed. The PDN-GW then sends the Update Bearer Request (PTI, EPS Bearer Identity, APN-AMBR, TFT, Retrieve Location) message to the Serving-GW. The Procedure Transaction Id (PTI) parameter is used when the procedure was initiated by a UE Requested Bearer Resource Modification procedure - see clause 5.4.5. "Retrieve Location" is indicated if requested by the PCRF. If the PDN-GW initiated bearer modification procedure was triggered by a UE requested bearer resource modification procedure and if 3GPP PS Data Off UE Status was present in the Bearer Resource Command PCO, the PDN-GW shall include the 3GPP PS Data Off Support Indication in the Update Bearer Request PCO.

The Serving-GW sends the Update Bearer Request (PTI, EPS Bearer Identity, APN-AMBR, TFT, Retrieve Location) message to the MME. If the UE is in ECM-IDLE state (and extended idle mode DRX is not enabled) the MME will trigger the Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3). In that case the following steps 4-7 may be combined into Network Triggered Service Request procedure or be performed stand-alone. If both the PCO and the TFT are absent and the APN-AMBR has not been modified, the MME shall skip the following steps 4-7. If the UE is in ECM-IDLE state and extended idle mode DRX is enabled for the UE, the MME will trigger Network Triggered Service Request from step 3 (which is specified in clause 5.3.4.3) and start a timer which is configured to a value smaller than the GTP re-transmission timer. If the MME receives no response from the UE before the timer expires, the MME sends an Update Bearer Response with a rejection cause indicating that UE is temporarily not reachable due to power saving and then sets the internal flag Pending Network Initiated PDN Connection Signalling. The rejection is forwarded by the Serving-GW to the PDN-GW. In this case, the steps 4-9 are skipped.

The MME builds a Session Management Request message including the TFT, APN-AMBR, EPS Bearer Identity and a WLAN offloadability indication. The MME then sends a Downlink NAS Transport (Session Management Configuration) message to the eNodeB. If the APN-AMBR has changed, the MME may also update the UE-AMBR. And if the UE-AMBR is updated, the MME signal a modified UE-AMBR value to the eNodeB by using S1-AP UE Context Modification Procedure. 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.

The eNodeB sends the Direct Transfer (Session Management Request) message to the UE. The UE uses the uplink packet filter (UL TFT) to determine the mapping of traffic flows to the radio bearer. The UE stores the modified APN-AMBR value and sets the MBR parameter of the corresponding non-GBR PDP contexts (of this PDN connection) to the new value. The UE shall set its TIN to "GUTI" if the modified EPS bearer was established before ISR activation.

The UE NAS layer builds a Session Management Response including EPS Bearer Identity. The UE then sends a Direct Transfer (Session Management Response) message to the eNodeB.

The eNodeB sends an Uplink NAS Transport (Session Management Response) message to the MME.

If the procedure is performed without steps 4-7 and location retrieval is requested and the UE is ECM_CONNECTED and unless the MME is configured not to retrieve ECGI from the eNodeB under this condition, the MME uses the Location Reporting Procedure described in clause 5.9.1 to retrieve the ECGI from the eNodeB. The MME acknowledges the bearer modification to the Serving-GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message. The MME includes the last known User Location information.

The Serving-GW acknowledges the bearer modification to the PDN-GW by sending an Update Bearer Response (EPS Bearer Identity, User Location Information (ECGI)) message.

If the bearer modification procedure was triggered by a PCC Decision Provision message from the PCRF, the PDN-GW indicates to the PCRF whether the requested PCC decision (QoS policy) could be enforced or not by sending a Provision Ack message. This then allows the PCRF-Initiated IP-CAN Session Modification procedure or the PCEF-initiated IP-CAN Session Modification procedure as defined in TS 23.203 to continue and eventually conclude, 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. If the bearer modification is rejected with a cause indicating that the UE is temporarily not reachable due to power saving, then the PDN-GW re-attempts the same procedure after it receives the indication that the is UE available for end to end signalling in the subsequent Modify Bearer Request message.