Monday, June 13, 2011

How is inter-frequency Handover triggered?

The network decides that inter frequency measurements need to be performed and sends the MEASUREMENT CONTROL MESSAGE with Measurement type set to Inter-Frequency measurements. Generally it will set an Event as well along with the measurements. The following are list of Events that can trigger Measurement Report.
  •  Event 2a: Change of Best Frequency
  •  Event 2b: The estimated quality of the currently used frequency is below a certain threshold and the    estimated quality of a non-used frequency is above a certain threshold
  •  Event 2c: The estimated quality of a non-used frequency is above a certain threshold
  •  Event 2d: The estimated quality of the currently used frequency is below a certain threshold
  •  Event 2e: The estimated quality of a non-used frequency is below a certain threshold
  •  Event 2f: The estimated quality of the currently used frequency is above a certain threshold
The Inter-Frequency Handover Evaluation bases its decision on P-CPICH quality measures on the currently used frequency and on one or more non-used frequencies. If the evaluation result is positive, one cell on a non-used frequency is proposed to Inter-Frequency handover Execution.
Inter-Frequency Handover is a hard handover where the UE is ordered by the network to tune to another frequency. This means that there will be small interruptions in the data flow to and from the UE.


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