LTE RAN Pre-Registration for CSFB Return
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Solution Overview
Problem
The existing Circuit-Switched Fallback (CSFB) mechanism in LTE RANs leads to repeated pre-registration of UEs with the fallback RAN, burdening the LTE RAN's air-interface resources and causing service degradation due to extensive messaging.
Innovation Solution
The LTE RAN autonomously pre-registers UEs with the fallback network upon detecting their return after a CSFB service, using stored records of previous release-and-redirect operations, thereby reducing the need for UE-initiated pre-registration messages and managing air-interface capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE initiates pre-registration with the fallback RAN every time it returns from CSFB service, then the fallback RAN maintains accurate reachability information, but the LTE RAN air-interface resources are burdened by repeated messaging
Solution Approach 1:
The network performs pre-registration of the UE with the fallback RAN in advance, before the UE actually needs to access the fallback service. The MME stores the UE's fallback RAN identity information and proactively updates the fallback RAN with reachability information when the UE returns to LTE coverage, rather than waiting for the UE to initiate registration. This preliminary action ensures the fallback RAN has accurate reachability information while avoiding repeated messaging overhead on the air interface.
Solution Approach 2:
The MME acts as an intermediary between the UE and the fallback RAN for pre-registration purposes. Instead of the UE directly communicating with the fallback RAN multiple times, the MME receives the UE's identity information and autonomously performs the pre-registration with the fallback RAN by sending update messages containing the UE's fallback RAN identity. This intermediary role eliminates the need for repeated UE-initiated registration messages while maintaining accurate reachability information.
2Reliability
If the LTE RAN releases and redirects the UE to fallback RAN for voice calls, then voice service continuity is maintained, but the LTE RAN must manage additional signaling overhead for tracking and pre-registration
Solution Approach 1:
The MME autonomously performs pre-registration with the fallback RAN using stored UE identity information without requiring the UE to initiate registration messages. When the UE returns from CSFB service, the MME automatically updates the fallback RAN with current reachability information, making the system self-service the pre-registration function and reducing signaling overhead while maintaining voice service continuity.
Data Source
AI summary
Disclosed is a method and corresponding system for managing CSFB pre-registration. A first network serving a UE releases the UE from being served by the first network and redirects the UE to transition from being served by the first network to being served by a second network. The first network then detects that the UE has returned to be served by the first network. In response to detecting the return of the UE, and based on the previous releasing and redirecting of the UE, the first network then initiates a pre-registration of the UE with the second network to inform the second network that the UE is now reachable via the first network.