ges 11 to 22. VoLTE and ViLTE Source Target Traffic Radio Bearer S1 Bearer S5 Bearer Incoming data Outgoing data S1-AP HANDOVER REQUIRED S1-AP HANDOVER REQUEST S1-AP HANDOVER REQUEST ACK GTPv2-C CREATE INDIRECT FORWARDING TUNNEL REQUEST GTPv2-C CREATE INDIRECT FORWARDING TUNNEL RESPONSE S1-AP HANDOVER COMMAND RRC ConnectionReconfiguration S1-AP eNB STATUS TRANSFER S1-AP MME STATUS TRANSFER RRC ConnectionReconfiguration Complete Traffic S1 Bearer S5 Bearer Incoming data Temporary Bearer Radio Bearer Temporary Bearer Traffic Radio Bearer S1 Bearer S5 Bearer Outgoing data S1-AP HANDOVER NOTIFY GTPv2-C MODIFY BEARER REQUEST GTPv2-C MODIFY BEARER REQUEST DIAMETER CCR DIAMETER CCA GTPv2-C MODIFY BEARER RESPONSE GTPv2-C MODIFY BEARER RESPONSE GTP-U EM (Bearer S1) GTP-U EM (Bearer temporaire) GTP-U EM (Bearer temporaire) Traffic Radio Bearer S1 Bearer S5 Bearer Incoming data S1-AP UE CONTEXT RELEASE REQUEST S1-AP UE CONTEXT RELEASE COMPLETE GTPv2-C DELETE INDIRECT FORWARDING TUNNEL REQUEST GTPv2-C DELETE INDIRECT FORWARDING TUNNEL RESPONSE Figure 7.5. Handover based on S1 without relocation procedure Handover 1) The source eNB entity initiates the preparation phase of the handover by sending the message S1-AP HANDOVER REQUIRED to the MME entity. 2) The MME entity sends to the target eNB entity the message S1-AP HANDOVER REQUEST to perform the reservation of resources. 3) The target eNB entity responds to the MME entity with the message S1-AP HANDOVER REQUEST ACK containing the following information: - the TEID identifier of the temporary bearer that the SGW entity will use in the GTP-U header when it sends traffic to the target eNB entity; - the TEID identifier of the S1 bearer that the SGW entity will use in GTP-U header when it sends traffic to the target eNB entity; - the technical characteristics of the radio interface in the information element handover command. 4) The MME entity forwards the TEID identifier relating to the temporary bearer to the SGW entity in the message GTPv2-C CREATE INDIRECT FORWARDING TUNNEL R