EQUEST X2-AP HANDOVER REQUEST ACK RRC ConnectionReconfiguration X2-AP SN STATUS TRANSFER RRC Connection aReconfiguration Complete Traffic S1 Bearer S5 Bearer Incoming data X2 Bearer Radio Bearer Traffic Radio Bearer S1 Bearer S5 Bearer Outgoing data S1-AP PATH SWITH REQUEST 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 GTP-U EM Traffic Radio Bearer S1 Bearer S5 Bearer Incoming data S1-AP PATH SWITH REQUEST ACK X2-AP UE CONTEXT RELEASE Figure 7.2. Handover based on X2 without relocation procedure VoLTE and ViLTE 6) The target eNB entity starts the completion phase and transmits to the MME entity the message S1-AP SWITH PATH REQUEST containing the following information: - the TEID identifier of the S1 bearer that the SGW entity will use in the GTP-U header when it sends traffic to the target eNB entity; - the E-UTRAN cell global identifier (ECGI). 7) The MME determines that the SGW entity shall not change and transfers this information to the SGW entity in the message GTPv2-C MODIFY BEARER REQUEST. 8) The SGW entity transfers the ECGI identifier of the cell to the PGW entity in the message GTPv2-C MODIFY BEARER REQUEST. 9) The PGW entity transfers the ECGI identifier of the cell to the policy and charging rules function (PCRF) in the message DIAMETER credit- control-request (CCR). 10) The PCRF entity responds to the PGW entity with the message DIAMETER credit-control-answer (CCA) to acknowledge the request. 11) The PGW entity responds to the SGW entity with the message GTPv2-C MODIFY BEARER RESPONSE to acknowledge the request. 12) The SGW entity responds to the MME entity with the message GTPv2-C MODIFY BEARER RESPONSE message to acknowledge the request. 13) The target eNB entity transmits to the mobile the traffic received from the source eNB entity until it receives the GTP-U EM (End Marker) messages of the SGW entity, from which the traffic will be received directly. 14) The MME responds to the target e