Mobile Unit Priority Call Handling Across LTE and 3G Systems
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Solution Overview
Problem
In the context of multimedia priority service in LTE and CS fallback to 3G systems, priority call information from LTE may not be reflected in 3G, leading to potential barring of priority calls due to access class barring, resulting in missed terminating calls.
Innovation Solution
A mobile device capable of receiving priority call information from an LTE system and access class barring information from a 3G system, allowing it to connect and process priority calls regardless of 3G access class barring, or by treating such calls as emergency calls exempt from barring, ensuring proper terminating call handling across different radio communication systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mobile device follows access class barring information of 3G after performing CSFB from LTE to 3G, then the device complies with 3G access control rules, but priority call information of LTE is not reflected and priority calls may be barred
Solution Approach 1:
The mobile device performs preliminary actions by storing the priority call information received from LTE before performing CSFB to 3G. This stored information is then used during the 3G access process to override access class barring restrictions, ensuring priority calls are not blocked despite following 3G access control rules.
Solution Approach 2:
The mobile device acts as an intermediary between LTE priority call information and 3G access class barring mechanisms. It receives and stores priority information from LTE, then uses this information to modify its behavior in 3G by overriding access class barring when appropriate, thus mediating between the two systems' conflicting requirements.
2Reliability
If the mobile device overrides access class barring information to process priority calls in 3G, then priority calls are received correctly, but the device may violate 3G access control protocols
Solution Approach 1:
The mobile device applies different access control qualities to different call types. For normal calls, it strictly follows 3G access class barring information. For priority calls identified from stored LTE information, it applies a different quality by overriding the barring restrictions, thus treating different objects (call types) with different access control qualities.
Solution Approach 2:
The mobile device changes the access control parameter dynamically based on call priority. When a priority call is detected, it changes the access class barring parameter from enforced to overridden, allowing the priority call to proceed despite the general restriction. This parameter change resolves the conflict between protocol compliance and priority call reliability.
3Reliability
If the mobile device stores priority call information from LTE, then it can make informed decisions in 3G, but additional memory and processing are required
Solution Approach 1:
The mobile device extracts only the essential priority call information from LTE before CSFB, storing only the critical parameters needed to identify and handle priority calls in 3G. This extraction approach provides sufficient information for reliable priority call handling while minimizing the storage burden and processing complexity.
Data Source
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AI summary
A mobile device (300) is wirelessly connectable to an LTE system configured to notify the mobile device of priority call information indicating a priority level of processing for an terminating call, and a 3G system configured to inform the mobile device of access class barring information specifying barring of an terminating call depending on an access class of the terminating call. If the terminating call is a priority call whose priority level in the priority call information indicates a higher processing priority than other calls and the barring by the access class barring information is set, the mobile device (300) executes connection to 3G system (20) and processes the terminating call, regardless of the access class barring information.