Inter-RAT Registration Optimization via SGs Interface Indication
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Solution Overview
Problem
Current wireless communication systems lack standardized methods for differentiating between circuit switched fallback (CSFB) and circuit switched (CS) over evolved packet system (EPS) messages, leading to uncertainty for wireless transmit/receive units (WTRUs) when performing inter-system changes, which results in delayed call setup times due to the need for decoding system information and performing independent registration procedures.
Innovation Solution
Incorporating information in mobility messages about the support of non-packet switched services (NPSS) and circuit switched services in the target radio access technology (RAT) network, allowing WTRUs to determine the appropriate registration procedure and interface usage, such as including indicators for CSFB, SMS, VoIP, and emergency call support, to facilitate inter-RAT transfers and reduce registration complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the network does not broadcast or advertise the existence of the SGs interface, then signaling overhead is reduced, but WTRUs cannot determine whether to perform combined registration or independent registration procedures
Solution Approach 1:
The network performs preliminary action by broadcasting system information messages that indicate the existence of the SGs interface before the WTRU needs to make registration decisions. This allows the WTRU to know in advance whether to perform combined EPS/IMSI attach or independent registration, eliminating the need for trial-and-error approaches and reducing signaling overhead from repeated registration attempts.
2Reliability
If the WTRU performs independent registration procedures without knowing about combined registration capability, then registration reliability is improved, but call setup time increases due to delayed service availability
Solution Approach 1:
The system implements feedback by broadcasting system information messages that provide real-time information about the SGs interface availability and combined registration support. The WTRU uses this feedback to make informed decisions about which registration procedure to perform, ensuring both reliability (by choosing the appropriate procedure) and speed (by avoiding unnecessary independent registration steps).
3Adaptability or versatility
If the network provides detailed information about NPSS support in mobility messages, then service differentiation is improved, but signaling overhead increases
Solution Approach 1:
The information about NPSS support is segmented into different system information messages and mobility management messages, each carrying specific indicators for different services (CSFB, SMS, VoIP, emergency calls). This segmentation allows the network to provide comprehensive service differentiation information without overwhelming the signaling channel with a single large message, enabling WTRUs to efficiently parse and act on relevant information.
Data Source
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AI summary
A method and apparatus are described for providing non-packet switched service to a target radio access technology (RAT) network. A circuit switched (CS) service notification message is received by a wireless transmit/receive unit (WTRU). If the WTRU has been allocated a valid temporary mobile subscriber identity (TMSI), a paging response message including the valid TMSI is transmitted after an inter-system change is performed from a source RAT network to a target RAT network. The CS service notification message is for terminating a CS call request. The source RAT network may be a long term evolution (LTE) network, and the target RAT network may be a third generation partnership project (3GPP) network. Alternatively, if the WTRU has not been allocated a valid TMSI, a paging response message including an international mobile subscriber identity (IMSI) that identifies the WTRU is transmitted after the inter-system change.