An S1 handover is a fallback for scenarios where X2 interface is not available. … The MME and the SGW are involved during the handover procedure. An interesting part of LTE S1 handovers is the indirect tunnel that is established to carry the downlink data during the handover process.
What is X2 and S1 handover in LTE?
The X2 procedure is used to handover a UE from a source (H)eNB to a target (H)eNB for which the MME is unchanged. … The S1 procedure is used by the source eNB to initiate a handover through the S1-MME interface, see . This procedure may relocate the MME and/or the S-GW.
What is X2 interface?
X2 interface. A point-to-point logical interface between two eNodeBs with the E-UTRAN. It supports the exchange of signaling information between two eNodeBs and supports the forwarding of protocol data units (PDUs) to the respective tunnel endpoints. X2 Application Protocol (X2AP) Protocol used by the X2 interface.
What is handover command?
This message is sent by the MME to inform the source eNB that resources for the handover have been prepared at the target side.
What is X2AP?
Server. X2 Application protocol (X2AP) provides control plane signalling between two eNBs in E-UTRAN (or between eNB and gNB for EN-DC) over X2 interface. X2 interface is used in UE related mobility procedures, in dual connectivity procedures and in global procedures between two eNBs (or one eNB and one gNB for EN-DC).
How does handover happen?
Inter-BTS Intra BSC handover: This for of GSM handover or GSM handoff occurs when the mobile moves out of the coverage area of one BTS but into another controlled by the same BSC. … Inter-MSC handover: This form of handover occurs when changing between networks. The two MSCs involved negotiate to control the handover.