LTE Basic lnformations

#LTE💘

1- LTE UE Stack Architecture
2- LTE eNB Stack architecture

3- L Handover procedure in LTE for UEs in active mode.

Handover procedure in LTE for UEs in active mode:

1) S1-handover procedure-The S1-handover procedure is performed between two eNBs without the X2 interface

2) X2-handover procedure-The X2 handover is used when direct connectivity between source and target eNBs exists.

During the handover, the Transmission Control Protocol (TCP) endpoints must be moved from the Source eNB to the Target eNB.

The Source eNB collects the UE measurements of the link quality and assists in the function control of the UE’s handover.

As a next step, source eNB makes a decision based on the measurement reports and RRM information to hand off the UE and it issues a handover request message to the Target eNB.

After that, admission control may be performed by the Target eNB according to the received quality of service information.

The Target eNB prepares the handover and sends the handover request acknowledgement to the Source eNB.

Such a message may also include information about Radio/Transport Network Layer (RNL/TNL) for the forwarding tunnels.

When handover request acknowledgement is received, data forwarding from the Source eNB to the Target eNB through the router may be initiated.

The Source eNB generates the handover command (RRC message) towards the UE. Then, the UE performs synchronization to Target eNB and accesses the target cell. Then it sends a handover message to indicate that the handover procedure is completed.

The Target eNB can now start sending data to the UE and at the same time send a path switch message to the server MME to inform that the UE has changed the cell.
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