Question: In an Evolved Packet System (EPS), when a User Equipment (UE) is in the EMM-REGISTERED and ECM-IDLE states with Radio Resource Control (RRC) in RRC_IDLE, what is the level of granularity at which the UE's position is known to the network?
Option 1: Cell level
Option 2: Tracking Area level
Option 3: Public Land Mobile Network (PLMN) level
Option 4: Not known by the network
Explanation: According to the EPS state model, when a UE is in EMM-REGISTERED and ECM-IDLE states with RRC in RRC_IDLE, the mobility management is characterized by cell reselection, and the UE's position is known by the network at the tracking area level. This indicates that while the UE is registered and idle from a connection management perspective, its location is updated and known to the network within the bounds of a tracking area, which is a larger geographical area than a single cell but smaller than an entire PLMN.