What are the agreed state transitions between 2G/3G and LTE?


The agreed state transitions that will be supported between 2G/3G and LTE are shown in Figure below. The methods to execute the supported state transitions are the following:

A) = PDP Context establishment needed, if no PDP context exists.

  • Network controlled, prepared handover, for UEs in connected state
  • Network controlled Cell Change Order (CCO) with Network Assisted Cell Change (NACC) to GERAN, for UEs in connected state
  • UE based cell reselection, for UEs in idle state

The network controlled, prepared handover based state transition is executed via the 2G/3G-LTE inter-system handover procedure, while the cell reselection based state change is executed via a Routing Area Update (LTE to 2G/3G) or via a Tracking Area Update (2G/3G to LTE) procedure.