telecom • networking • design

an EventHelix.com blog


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S1AP View of Inter-MME S1 Handover

Here we look at the S1 handover that involves an MME change. The S1 handover is analyzed at the S1AP interface. S1AP messages involved in S1 handover are shown just before the message. The messages show a high level structure of the complex messages involved in the interaction.

Inter-MME-S1-handover

Additionally, you can click on any S1AP message to see the complete field level details like the one shown below.

PDCP-transfer


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LTE S1-interface handover between eNodeBs

LTE networks prefer using the X2 interface for performing inter eNodeB handovers. An S1 handover is a fallback for scenarios where X2 interface is not available.

As the name suggests, S1 handovers take place over the S1-interface. 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. Refer to the S1 handover call flow for a detailed signaling flow.

Inter eNodeB S1 handover in LTE