Question: In Iu mode, how does a User Equipment (UE) in RRC-IDLE state obtain information about the Routing Area Identity (RAI) and Cell Identity to determine if a Routeing Area Update is required?
Option 1: Via an "MM Information" message from the Serving RNC at the Non-Access Stratum (NAS) layer.
Option 2: By comparing its stored International Mobile Subscriber Identity (IMSI) with the broadcast IMSI from the network.
Option 3: Through a dedicated signaling connection established for location management.
Option 4: From the broadcast system information at the Radio Resource Control (RRC) layer.
Explanation: In RRC-IDLE state, the UE is not actively connected to the network for dedicated signaling. Therefore, it relies on broadcasted information for updates. The correct method for a UE in RRC-IDLE state to obtain RAI and Cell Identity for determining Routeing Area Updates is through the broadcast system information at the RRC layer, as this is how the network disseminates such information to idle UEs. This process allows the UE to stay informed without needing a dedicated connection, aligning with the power-saving and efficiency goals of the IDLE state.