Question: Upon receiving an SGsAP-PAGING-REQUEST message for a UE in EMM-IDLE mode without Location Area Identity (LAI), how does the Mobility Management Entity (MME) behave, according to 3GPP specifications?
Option 1: The MME immediately sends an SGsAP-SERVICE-REQUEST message to the Visitor Location Register (VLR) with default parameters.
Option 2: The MME waits for the UE to enter EMM-CONNECTED mode before sending an SGsAP-SERVICE-REQUEST to the VLR.
Option 3: The MME rejects the paging request and sends an SGsAP-PAGING-REJECT message to the VLR due to missing LAI.
Option 4: The MME behaves according to a standardized procedure for handling CS fallback in EPS, as specified for such scenarios.
Explanation: This option is correct because, when the UE is in EMM-IDLE mode and the SGsAP-PAGING-REQUEST message is received without LAI, the MME's behavior follows a standardized procedure for CS fallback in EPS, ensuring interoperability and consistent network behavior.