Emergency Call Cell Search Optimization in Out-of-Service UEs
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Solution Overview
Problem
Current wireless telecommunications systems, particularly in UMTS, face challenges in efficiently handling out-of-service emergency calls due to the time-consuming process of cell selection, which can delay the establishment of emergency connections when a user is outside service coverage.
Innovation Solution
The method involves initiating a search for an acceptable cell to establish emergency calls without waiting for the completion of a full cell scan, allowing the user equipment to prioritize emergency call setup by changing search criteria to any Public Land Mobile Network and camping on the first available cell, thereby reducing the time required to establish an emergency connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the device performs a full cell scan to find an acceptable cell for emergency calls, then the reliability of cell selection is improved, but the time required to establish emergency calls increases
Solution Approach 1:
The device performs cell selection and camps on an acceptable cell before the emergency call is actually initiated. The cell search and selection processes are completed in advance, so when an emergency call is triggered, the device can immediately use the pre-selected cell without waiting for the call setup to begin the search, thus resolving the contradiction between thorough cell selection and fast emergency call establishment
Solution Approach 2:
The device dynamically adjusts its operation mode based on the detection of emergency call initiation. Upon detecting an emergency call, the device transitions from normal operation to emergency mode, where it prioritizes rapid cell selection by modifying search criteria to accept any suitable cell rather than requiring optimal cell conditions, thus balancing reliability and speed based on the operational context
2Reliability
If the device waits for complete cell scan before establishing emergency calls, then the quality of cell connection is improved, but the speed of emergency call setup deteriorates
Solution Approach 1:
The device completes cell selection and camps on an acceptable cell in advance before the emergency call is initiated. This preliminary cell preparation ensures that when the emergency call starts, the device already has a validated cell to use, eliminating the need to wait for cell scan completion during call setup, thus achieving both good connection quality and fast setup speed
Solution Approach 2:
The device changes the cell selection parameters and criteria dynamically. During normal operation, it uses standard cell selection criteria for optimal connection quality. Upon detecting emergency call initiation, it switches to emergency cell selection mode with relaxed criteria that accept any suitable cell, thereby improving setup speed while maintaining adequate connection quality for emergency purposes
Data Source
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AI summary
Apparatus and a method for handling out of service emergency calls in a wireless telecommunications system user equipment (UE) are disclosed. When an emergency call is initiated on a UE when the UE is in an out of service area, the UE in response to the initiating of an emergency call initiates a search for an acceptable cell rather than continuing with a search for suitable cells. The UE checks whether an acceptable cell is found. If an acceptable cell is found then the emergency call is connected.