Question: What is the primary purpose of the UE History Information Element (IE) in the X2 Application Protocol (X2AP) within an Evolved Universal Terrestrial Radio Access Network (E-UTRAN)?
Option 1: To manage the Quality of Service (QoS) for ongoing sessions of a User Equipment (UE) in idle state.
Option 2: To provide information about cells that a User Equipment (UE) has been served by in an active state prior to the current (target) cell.
Option 3: To facilitate handover decisions based on UE's historical location in passive listening mode.
Option 4: To optimize network resource allocation for incoming UEs based on their past data usage patterns.
Explanation: The correct answer, Option 2, accurately reflects the purpose of the UE History Information IE as it pertains to tracking and sharing information about cells that have actively served a UE before it moved to the current cell. This is crucial for network optimization, handover management, and ensuring seamless connectivity. The other options are incorrect because they either refer to idle state, passive listening mode which isn't directly related to the IE's purpose, or past data usage patterns not mentioned in the context of UE History Information IE.