CSFB Delay Reduction via Pre-collected RAT Information
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Solution Overview
Problem
The existing Circuit Switched Fallback (CSFB) procedure in LTE networks often experiences delays and call failures due to lack of information about the target Radio Access Technology (RAT) during voice calls, leading to network congestion and temporary radio-related issues.
Innovation Solution
A method and system where User Equipment (UE) switches to a target radio access network based on information received from the LTE network or generated through a background scan, maintaining a RAT information table to minimize delays in obtaining CS services by quickly identifying and switching to the appropriate RAT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the UE follows the existing 3GPP standard redirection based CSFB procedure without maintaining RAT information, then the device complexity is reduced, but the call setup time increases due to delayed RAT selection
Solution Approach 1:
The UE performs background scans to detect and store RAT information (frequency, cell ID, signal strength) in advance before CSFB is needed. This preliminary action ensures that when CSFB is triggered, the UE already has pre-collected RAT information to immediately switch to the appropriate legacy RAT, thereby reducing call setup time without significantly increasing device complexity
Solution Approach 2:
The patent introduces an intermediary mechanism (RAT information table with frequency, cell ID, and signal strength parameters) that mediates between the LTE network and the CS domain. This intermediary structure stores pre-collected RAT information, allowing the UE to quickly select the target RAT during CSFB without complex real-time scanning, thus reducing call setup time while maintaining manageable device complexity
2Reliability
If the UE performs background scan to collect RAT information, then the reliability of CSFB is improved, but the energy consumption increases
Solution Approach 1:
The UE performs background scans periodically rather than continuously, collecting RAT information at scheduled intervals. This periodic action ensures that RAT information is updated regularly to maintain CSFB reliability, while avoiding continuous scanning that would cause excessive energy consumption. The periodic scans balance the need for reliable RAT information with energy conservation
Solution Approach 2:
The background scan collects RAT information in advance during periods when CSFB is not immediately needed, preparing the RAT information table with frequency, cell ID, and signal strength data. This preliminary collection of information ensures high CSFB reliability when needed, while spreading the energy consumption over time rather than concentrating it during critical call setup moments
3Productivity
If the UE switches to legacy RAT without pre-collected RAT information, then the device complexity is minimized, but the productivity decreases due to call delays
Solution Approach 1:
The UE performs background scans to pre-collect and store RAT information (frequency, cell ID, signal strength) in a RAT information table before CSFB is required. This preliminary action enables the UE to quickly identify and switch to the appropriate legacy RAT during CSFB, significantly improving call setup efficiency. The pre-collected information is readily available, allowing immediate switching decisions without complex real-time analysis, thus enhancing productivity while keeping device complexity manageable
Data Source
AI summary
A method and system for minimizing delay in circuit-switched fallback (CSFB) procedure is disclosed. The disclosed method provides two different approaches for optimizing the delay during the CSFB procedure. In the first approach, user equipment (UE) receives a Location Area Identifier (LAI along with the Radio Access Technology (RAT) information from the network (LTE network). The UE uses the received RAT information from the network for switching to the target Radio Access Network (RAN) without informing to the LTE network. In another approach, the UE obtains the RAT information by performing a background scan in idle mode, when the UE receives LAI without RAT information from the network.