VoLTE Mobile-Originated (MO) Call Creation Call Flow
This section describes the VoLTE MO call creation call flow.

Step | Description |
---|---|
1 | UE requests for establishment of the IMS default bearer, PDU session, through PCF. After establishing the session, the UE receives the P-CSCF addresses from PCF. |
2 | UE sends the requested bearer resource modification information to MME. |
2a | MME sends the bearer resource command to S-GW. |
2b | S-GW sends the bearer resource command to SMF+PGW-C. |
3 | SMF+PGW-C sends the NPCF SM policy control update request to PCF. |
4 | PCF sends the NPCF SM Policy control update response back to SMF+PGW-C. |
5 | UE initiates SIP signaling toward P-CSCF (AF). |
5a | P-CSCF sends NPCF Policy Authorization Update message to PCF through CHF. |
6 | PCF sends the NPCF SM policy control update notify request to SMF+PGW-C. |
6a | SMF+PGW-C sends the NPCF SM Policy control update notify response back to PCF. |
7 | SMF sends ChargingDataUpdateReq by including Multi-Unit-Usage with Rating-Group-Id that are received as part of Charging_Description of Sm_PolicyControl_UpdateNotify_Request to install PCC Rules. |
8 | CHF provides ChargingDataUpdateResp with Multi-Unit-Information for received Rating-Group values in requested message. CHF also provides params changes for Session-Level and Rating-Group values. |
9 | SMF sends N4 Session Modification Request to the UPF by including Create ULPDRs and Create ULFARs. Create ULPDRs include SDFs and QER Info which are received as part of PCC Rule Installation. |
10 | UPF responds back with N4 Session Modification Response to SMF by including Created ULPDR and Created ULFAR. Create ULFAR contains UL Tunnel Information of UPF for the dedicated bearer creation. |
11 | SMF+PGW-C sends the GTPv2 create bearer request to S-GW. |
12 | S-GW sends the GTPv2 create bearer request to MME. |
13 | MME sends the bearer setup request and session management request to eNodeB. |
14 | RRC connection reconfiguration starts between UE and eNodeB. |
15 | The eNodeB sends the bearer setup response to MME. |
16 | UE initiates a direct transfer toward eNodeB. |
17 | eNodeB sends the session management response to MME. |
18 | MME sends the GTPv2 create bearer response to S-GW. |
19 | S-GW sends the GTPv2 create bearer response to SMF+PGW-C. |
20 | SMF+PGW-C sends the N4 session modification request or response to UPF+PGW-U. |
21 | SMF+PGW-C sends the NPCF SM policy control update request to PCF. |
22 | PCF sends the NPCF SM policy control update response back to SMF+PGW-C. |
23 | PCF sends the NPCF policy authorization notify request to P-CSCF (AF). |
24 | Establishes SIP-signaling and voice call between end-users through UE and P-CSCF (AF). |
Note |
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