Selective IMSI Detach for Circuit-Switched Service Continuity
Solution Overview
Problem
In LTE wireless communication systems, the existing detach procedures do not consider ongoing services, leading to service disruptions and inconvenience when a UE is implicitly detached by the network.
Innovation Solution
A communication device method that attaches to both circuit-switched and packet-switched domains, transmitting specific messages to handle detach notifications by performing an IMSI detach only for the packet-switched domain when a radio resource connection exists, thereby maintaining service continuity in the circuit-switched domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE performs a full detach procedure when notified of implicit detach, then the network can properly manage the UE's service status, but all ongoing services including circuit-switched services are dropped causing inconvenience to the user
Solution Approach 1:
The patent segments the detach procedure into domain-specific operations. Instead of performing a unified detach that affects all services, the UE selectively performs detach only for the packet-switched domain while maintaining attachment in the circuit-switched domain. This segmentation allows the network to properly manage PS services while preserving CS services, thus resolving the contradiction between reliable network management and user convenience.
2Ease of operation
If the UE maintains attachment in both circuit-switched and packet-switched domains, then service continuity is improved, but the device complexity and message handling requirements increase
Solution Approach 1:
The patent applies local quality by making the attachment status domain-specific rather than uniform. The UE maintains different attachment states in different domains: attached in the circuit-switched domain for service continuity, and detached in the packet-switched domain to respond to network notifications. This localized differentiation allows service continuity while managing complexity through domain-specific handling rather than global state changes.
Data Source
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AI summary
A communication device of handling a detach procedure comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The processing means is configured to execute the instructions stored in the storage unit. The instructions comprise attaching to a network in a Network Mode of Operation I (NMO I) for a circuit switched (CS) domain and a packet switched (PS) domain; transmitting a first General Packet Radio Service (GPRS) mobility management (GMM) message to the network; receiving a second GMM message comprising a GMM cause indicating an implicit detach from the network; and performing an International Mobile Subscriber Identity (IMSI) detach for the PS domain but not for the CS domain, when a Radio Resource (RR) connection exists.