CSFB Call Setup Optimization via Pre-stored System Information
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Solution Overview
Problem
The existing mobile communication systems using Circuit Switched Fallback (CSFB) service experience significant degradation in Quality of Service (QoS) due to the additional time required for switching from LTE to 2G/3G legacy systems and receiving system information, which prolongs the setup time for voice calls.
Innovation Solution
The method and apparatus reduce the time required to set up a voice call by switching from a high-speed packet-based system to a voice call-based system, determining if system information reception for CSFB is complete, and performing the CSFB procedure without additional system information reception, including pre-storing system information and omitting unnecessary system information blocks and security procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE switches from LTE to 2G/3G legacy system and receives system information before setting up a voice call, then the call can be established in the legacy system, but the QoS degrades due to the additional time required for switching and receiving system information
Solution Approach 1:
The patent applies preliminary action by having the UE receive and store system information from the 2G/3G legacy system before the actual voice call setup is needed. The UE proactively camps on the legacy system, receives system information blocks (SIBs), and stores them in memory during idle periods or when data services are not actively being used. When a voice call is subsequently initiated, the UE can immediately use the pre-stored system information to quickly establish the call without needing to perform time-consuming system information reception procedures, thus reducing call setup time while maintaining reliable call establishment capability
Solution Approach 2:
The patent implements dynamics by making the UE's operational state flexible and adaptive. The UE dynamically switches between different operational modes: during data service usage, it operates on LTE for high-speed data; when voice call conditions arise, it dynamically transitions to the 2G/3G legacy system. The system dynamically manages the UE's camped state, allowing it to temporarily camp on the legacy system to acquire system information, then return to LTE for data services, optimizing performance based on current service requirements
2Reliability
If the UE performs complete system information reception from the 2G/3G legacy system, then all necessary information is available for call setup, but the process time increases significantly
Solution Approach 1:
The patent applies the extraction principle by selectively receiving only the essential system information blocks (SIBs) required for voice call setup from the 2G/3G legacy system, rather than receiving all available system information. The UE identifies and extracts specifically the SIBs containing parameters necessary for circuit-switched call establishment, such as cell access parameters, channel configuration, and mobility management information, while omitting optional or non-essential system information blocks. This selective extraction approach ensures that all necessary information for reliable call setup is obtained while significantly reducing the time required for system information reception
3Speed
If the UE camps on the LTE system for data services, then high-speed data transmission is achieved, but voice call setup requires additional switching overhead
Solution Approach 1:
The patent applies preliminary action by having the UE perform preparatory actions while camped on the LTE system for data services. Specifically, the UE proactively camps on the 2G/3G legacy system in idle mode, receives system information blocks, and stores them in memory before a voice call is actually needed. This preliminary preparation ensures that when a voice call is initiated, the UE can quickly switch to the legacy system and immediately use the pre-stored system information to establish the call, avoiding the need to perform time-consuming system information reception procedures during the call setup process
Solution Approach 2:
The patent uses the 2G/3G legacy system as an intermediary between the LTE data service environment and the voice call establishment process. The UE maintains a relationship with both systems: it camps on LTE for high-speed data services while simultaneously monitoring or periodically accessing the legacy system to acquire system information. The legacy system acts as an intermediary that provides the necessary system information and call setup parameters, enabling the UE to quickly establish voice calls without fully leaving the LTE data service context, thus reducing the complexity and time of system switching
Data Source
AI summary
The time required to set up a voice call in an exemplary embodiment, in which Circuit Switched Fallback (CSFB) is used, is reduced to provide a voice call service to a User Equipment (UE) in a Long Term Evolution (LTE) system. If a voice call occurs in a UE while the UE accesses the LTE system, the UE using CSFB switches to a 2G/3G legacy system, recycles system information for a 2G/3G cell that the UE has accessed before, and immediately proceeds with voice call setup without receiving system information unnecessary for a CSFB process.