Here i write very small notes about How Seamless Handover in LTE which is very basic and some require techniques for real time data handover in LTE.
Seamless handover is applied for user plane radio bearers mapped on RLC unacknowledged mode. These types are usually quite tolerant of losses, but less tolerant of delay (e.g. voice services). Therefore, seamless handover is designed to minimize complexity and delay, but can lead to loss of SDUs.
In teaching, for radio bearers to which seamless handover, PDCP entities including header compression contexts are reset and COUNT values are set to zero.
As a new key is generated from teaching anyway, there is no security reason to keep COUNT values . PDCP SDUs for transmission has not yet started will be sent after delivery to the target cell. At eNodeB , PDCP SDUs that have not yet been transmitted may be transmitted through X2 interface to the target eNodeB .
How Seamless Handover Happens in LTE
Seamless handover in LTE means the user can move between cells without dropping the connection or interrupting ongoing services like calls or video. This is managed by the network using measurements from the UE and fast coordination between eNodeBs.
The UE keeps checking nearby cells and reports signal quality back to its serving eNodeB. When the current cell’s signal gets weaker and a stronger neighbor is detected, the serving eNodeB prepares the target eNodeB for handover. It transfers the UE’s context, including security info and session data.
Once the target eNodeB is ready, the UE is told to switch, and it connects to the new cell immediately. Since all user data is forwarded between the two eNodeBs during the process, you don’t feel any break — that’s why it’s seamless. This approach uses X2 or S1 interfaces depending on how the cells are connected.