Proactive Circuit Switched Fallback for Faster Voice Call Setup
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Solution Overview
Problem
The existing circuit switched fallback (CSFB) process in 5G communications systems results in a time-consuming voice call setup due to the need for user equipment (UE) to wait for network messages before initiating fallback to the circuit switched domain, especially when handovers to 4G or 2G networks fail.
Innovation Solution
The UE proactively determines the inability to set up a voice call bearer in the target network and immediately initiates CSFB without waiting for rejection messages, using methods such as signal strength analysis and time thresholds to expedite the process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits for network rejection messages before initiating CSFB, then the network can confirm call setup failure, but the call setup time increases significantly
Solution Approach 1:
The UE performs preliminary assessment of 4G network conditions (signal strength, network status) before attempting call setup, and proactively initiates CSFB when conditions indicate likely failure, rather than waiting for network rejection messages. This preliminary action prevents unnecessary waiting and reduces call setup time.
Solution Approach 2:
The UE skips the waiting period for network rejection messages by directly initiating CSFB based on pre-assessment of network conditions. This rushing through of the intermediate waiting step significantly reduces call setup time while maintaining reliability through conditional triggers.
2Loss of time
If the UE proactively initiates CSFB without waiting for network messages, then the call setup time is reduced, but the risk of unnecessary fallback increases
Solution Approach 1:
The UE applies preliminary anti-action by assessing network conditions (signal strength thresholds, network status) before initiating CSFB. This pre-check prevents unnecessary fallback to 2G/3G networks when 4G conditions are adequate, ensuring fallback accuracy while maintaining fast call setup.
Solution Approach 2:
The UE monitors changes in network parameters (signal strength, network status) and triggers CSFB only when parameters indicate actual failure conditions. This parameter-based triggering ensures accurate fallback decisions while maintaining reduced call setup time.
3Reliability
If the UE monitors network conditions continuously to determine fallback necessity, then the accuracy of fallback decision is improved, but the energy consumption increases
Solution Approach 1:
The UE performs periodic monitoring of network conditions at defined intervals rather than continuous monitoring. This periodic action maintains adequate fallback decision accuracy while significantly reducing energy consumption compared to continuous monitoring.
Solution Approach 2:
The UE performs preliminary network condition assessment before call setup and triggers CSFB only when conditions warrant it. This preliminary action avoids unnecessary continuous monitoring and reduces energy consumption while maintaining fallback decision accuracy.
Data Source
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AI summary
This application provides a circuit switched fallback method and apparatus. In the method, UE that initiates a calling process receives a first request sent by the first communications system, and after the UE is transferred to a second communications system and before the UE receives a first message from the second communications system, if the UE determines that a voice call bearer cannot be set up in the second communications system, the UE initiates CSFB in the second communications system, where the first message is used by the UE to determine that a call request fails. Therefore, the UE can perform CSFB in the second communications system without a need to wait for the first message sent by a network side of the second communications system, thereby shortening call waiting duration.