Handover
Handover
Everybody who has experience with dealing with field trouble would know that this is never ending story, regardless of whether it is UE side issue or Network side issue.This means that this technote will never be complete. I will be updated forever and you have to revisit this page forever as well -:)
State Machine Overview
The main topic on this page is to go through the state sequence (s0)->(a1)->(b1)->(c1)->(e1)->(f1)->(g1)->(g2). But other state transition sequence involving two cells will be treated as well.
Overview of Handover Process - LTE to LTE The simplest way to define the word 'handover' would be "chaging the partner".
Who is chaning the partner ?
I meant "UE (Mobile Phone)".
Who is the parter in this case ?
I meant "Cell".
Therefore "Handover" is the process in which UE changes the cell. Overall logic is simple and this process are the same (or at least very similar) in every technology. A UE is in connection with a cell (let's call this 'Cell A').
Now a situation that requires handover happened.
Network send "signal quality measurement" command to UE for the garget cell ('Cell B') to which it will handover to.
UE performance the measurement and report the "measurement result" to the network via the current cell (Cell A).
Network evaluate the measurement result reported by UE.
If the evaluation result turns out to be good for handover, Network send 'Change Cell' command to UE.
UE perform the cell change process.
If cell change process is completed properly, UE send 'cell change completion' message to the network via the target cell (Cell B).
I used very generic term e.g, "signal quality measurement command", "measurement result", "Change Cell Command", "Cell Change Completion Message" etc. These generic commands can be translated to a specific jargon for each technology. For example, if I translate these for UMTS, they would be as follows : "Signal quality measurement command" ==> Measurement
Everybody who has experience with dealing with field trouble would know that this is never ending story, regardless of whether it is UE side issue or Network side issue.This means that this technote will never be complete. I will be updated forever and you have to revisit this page forever as well -:)
State Machine Overview
The main topic on this page is to go through the state sequence (s0)->(a1)->(b1)->(c1)->(e1)->(f1)->(g1)->(g2). But other state transition sequence involving two cells will be treated as well.
Overview of Handover Process - LTE to LTE The simplest way to define the word 'handover' would be "chaging the partner".
Who is chaning the partner ?
I meant "UE (Mobile Phone)".
Who is the parter in this case ?
I meant "Cell".
Therefore "Handover" is the process in which UE changes the cell. Overall logic is simple and this process are the same (or at least very similar) in every technology. A UE is in connection with a cell (let's call this 'Cell A').
Now a situation that requires handover happened.
Network send "signal quality measurement" command to UE for the garget cell ('Cell B') to which it will handover to.
UE performance the measurement and report the "measurement result" to the network via the current cell (Cell A).
Network evaluate the measurement result reported by UE.
If the evaluation result turns out to be good for handover, Network send 'Change Cell' command to UE.
UE perform the cell change process.
If cell change process is completed properly, UE send 'cell change completion' message to the network via the target cell (Cell B).
I used very generic term e.g, "signal quality measurement command", "measurement result", "Change Cell Command", "Cell Change Completion Message" etc. These generic commands can be translated to a specific jargon for each technology. For example, if I translate these for UMTS, they would be as follows : "Signal quality measurement command" ==> Measurement