Wireless Terminal Redirection Failure Handling
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Solution Overview
Problem
The existing release-with-redirect process for wireless user terminals switching from a packet-switched to a circuit-switched connection is unreliable and time-consuming, often resulting in repeated failures to establish a new connection, leading to service disruptions and delays, with operators struggling to identify and address the underlying issues.
Innovation Solution
The process is improved by allowing the terminal to inform the network of the failure cause, enabling the network to send a modified redirect message based on the identified cause, and providing this information to the network management for long-term adaptation of the redirect process, such as examining system information distribution and cell availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If release-with-redirect is used to switch from packet-switched to circuit-switched connection, then connection establishment speed is improved, but connection reliability deteriorates due to repeated attach failures
Solution Approach 1:
The terminal provides feedback about attach failure causes to the network by sending failure indication information in connection requests. This feedback loop enables the network to identify whether failures are due to invalid system information, radio conditions, or other issues, allowing for targeted corrections to improve subsequent attach success rates while maintaining the fast redirect mechanism
Solution Approach 2:
The network modifies redirect parameters based on failure analysis. When invalid system information is detected as the failure cause, the network changes the system information parameters in subsequent redirect messages. When radio conditions are problematic, the network adjusts frequency or cell selection parameters, thereby improving connection reliability without sacrificing the speed advantage of release-with-redirect
2Reliability
If regular handover is used to switch connections, then connection reliability is improved through evaluation of target cells, but connection establishment time increases
Solution Approach 1:
The network performs partial evaluation by selectively analyzing failure causes only when attach attempts fail, rather than evaluating all potential target cells in advance as regular handover does. This partial action approach maintains the speed advantage of release-with-redirect while improving reliability through targeted corrections based on actual failure data
Solution Approach 2:
The network performs preliminary analysis of failure causes by examining failure indication information from terminals. This preliminary action allows the network to identify systematic issues with system information or cell selection before they cause repeated failures, enabling proactive adjustments that improve reliability without requiring full handover evaluation procedures
3Loss of energy
If blind redirect without system information is sent, then network signaling overhead is reduced, but attach success rate deteriorates due to terminal inability to properly attach
Solution Approach 1:
The network dynamically adjusts the inclusion of system information in redirect messages based on failure analysis. When failures are attributed to invalid system information, the network switches to including system information in subsequent redirects. When failures are due to other causes, the network maintains the low-overhead approach of excluding system information, thereby optimizing the balance between signaling overhead and attach success rate
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Methods and arrangements for handling shortcomings when a wireless user terminal (200), currently using a first connection (2:1) with a first network node (202), is redirected to a second connection in a release-with-redirect process. The first network node sends a first redirect message (2:2) to the terminal with an instruction to attach to the second connection. The terminal then sends a message (2:5) to the first network node which comprises a failure indication indicating that the terminal has made a failed attempt (2:3) to attach to the second connection. The first network node then identifies (2:6) a cause for the failed attempt by using the failure indication. The first network node also performs at least one of: sending (2:7) a second redirect message to the terminal based on the identified cause, and providing (2:9) the identified cause to a network management function, to enable adaptation of the release-with-redirect process.