Main Handover Events for 3G (UTRA FDD)

by Kamal Vij

In GSM there was a dedicated channel for periodically reporting the controller (BSC) with the current situation faced by UE. But in 3G, the measurements can be set to Periodic or Event-triggered. Almost unanmously, all operators decided for Event-triggered measurements.

The following categories of measurement events are defined for UTRA FDD

  • 1-series (event 1A to 1F):
    • Intra-frequency events
  • 2-series (event 2A to 2F):
    • inter-frequency events
  • 3-series (event 3A to 3D):
    • inter-RAT events
  • 4-series (event 4A and 4B):
    • traffic volume events
  • 5-series (event 5A):
    • quality event
  • 6-series (event 6A to 6G):
    • UE internal events
  • 7-series (event 7A to 7C):
    • UE positioning events

From all the above events, the most commonly discussed are the Series 1 Events because they lead to start and stop of Soft Handover. Event 1A, 1B and 1C are the king of all events.

  • 1A:
    • A Primary CPICH enters the reporting range.
  • 1B
    • A primary CPICH leaves the reporting range. Similar concept as in 1A.
  • 1C:
    • A non-active primary CPICH becomes better than an active primary CPICH
  • 1D:
    • Change of best cell
  • 1E:
    • A Primary CPICH becomes better than an absolute threshold
  • 1F:
    • A Primary CPICH becomes worse than an absolute threshold

More about these can be read in the Chapter 5 of book under Radio Resource Management Chapter.