ansfers the ECGI identifier of the cell to the PGW entity in the message GTPv2-C MODIFY BEARER REQUEST. 14) The PGW entity transfers the ECGI identifier of the cell to the PCRF entity in the DIAMETER CCR message. 15) The PCRF entity responds to the PGW entity with the DIAMETER CCA message to acknowledge the request. 16) The PGW entity responds to the SGW entity with the message GTPv2-C MODIFY BEARER RESPONSE to acknowledge the request. 17) The SGW entity responds to the MME entity with the message GTPv2-C MODIFY BEARER RESPONSE to acknowledge the request. 18) The target eNB entity transmits to the mobile the traffic received from the source eNB entity by the temporary bearer until it receives a Handover GTP-U EM message from the SGW entity from which the traffic will be received directly from the S1 bearer. 19) The release of the context of the mobile at the source eNB entity is triggered by the MME entity by sending the message S1-AP UE CONTEXT RELEASE REQUEST. 20) The source eNB entity responds to the MME entity with the message S1-AP and acknowledges the message received. 21) The release of the temporary bearer at the SGW entity is triggered by the MME entity by sending the message GTPv2-C DELETE INDIRECT FORWARDING TUNNEL REQUEST. 22) The SGW entity responds to the MME entity with the message GTPv2-C DELETE INDIRECT FORWARDING TUNNEL RESPONSE to acknowledge the received message. 7.3.2. Handover based on S1 with relocation The functional architecture for the handover based on S1 with the relocation of the MME and SGW entities is described in Figure 7.6. E-UTRAN Source Former S1-MME Former LTE-Uu LTE-Uu S1-MME Target Figure 7.6. Handover based on S1 with relocation functional architecture 212 VoLTE and ViLTE 7.3.2.1. Preparation phase The S1-based handover procedure with the relocation of the MME and SGW entities is described in Figure 7.7 for the preparation phase. 1) The source eNB entity initializes the preparation phase of the handover by sending the message S1-AP HANDOVER REQUIRED to the former MME entity.