UE Attach Procedure for IMS Call Request in LTE Networks
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Solution Overview
Problem
In LTE networks, certain conditions lead to undefined operations, resulting in detrimental actions such as dropped IMS calls or missing data, particularly when timers like T3411, T3402, T3346, T3410, and T3430 expire or fail, causing UE to remain in states like EMM-Deregistered.Attempting-to-Attach or EMM-Registered.Attempting-to-Update, leading to delayed service requests and user-initiated event stalls.
Innovation Solution
Modifying the 3GPP TS specifications to include triggers for multimedia telephony service requests, such as MMTel voice or video calls, to immediately initiate combined/normal attach or tracking area update procedures when timers like T3346 are not running, ensuring timely service activation without delay for user-initiated events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE waits for timer expiration before initiating attach or tracking area update procedures, then the network can manage resource allocation efficiently, but user-initiated services like IMS calls experience delays and may be dropped
Solution Approach 1:
The patent applies dynamics by making the attach and tracking area update procedures conditional rather than static. When a user-initiated service request arrives, the UE dynamically initiates attach or tracking area update procedures based on its current state, bypassing timer wait conditions. This dynamic behavior ensures service activation occurs immediately when needed, rather than waiting for timer expiration.
Solution Approach 2:
The patent applies preliminary action by having the UE proactively initiate attach or tracking area update procedures in response to user-initiated service requests, before the actual service can be activated. This preliminary action ensures the UE is in a proper registered state ready to receive service, eliminating delays that would occur if the UE had to wait for timer expiration or network-initiated procedures.
2Reliability
If the UE remains in Attempting-to-Attach or Attempting-to-Update states due to timer failures, then the network can prevent premature service activation, but legitimate user services are blocked and data may be lost
Solution Approach 1:
The patent applies local quality by differentiating the handling of service requests based on their origin. User-initiated service requests are treated differently from network-initiated procedures. When a user-initiated request arrives, the UE locally determines to immediately initiate attach or tracking area update procedures, giving priority to user services while maintaining network control for other scenarios.
Solution Approach 2:
The patent applies parameter changes by modifying the UE's operational parameters based on the type of service request. Upon receiving a user-initiated service request, the UE changes its state transition parameters to immediately initiate attach or tracking area update procedures, rather than waiting for timer expiration. This parameter change enables service accessibility while maintaining reliability through proper state management.
3Stability of the object's composition
If the network uses strict timer-based state management, then it can maintain proper UE registration states, but user experience deteriorates due to service delays and dropped calls
Solution Approach 1:
The patent applies preliminary anti-action by preemptively counteracting the harmful effect of timer-based delays before they occur. When a user-initiated service request arrives, the UE immediately initiates attach or tracking area update procedures, preventing the service quality degradation that would result from waiting for timer expiration. This preliminary anti-action maintains state management stability while eliminating service delays.
Data Source
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AI summary
Devices and methods of reducing delay in responding to UE user-initiated events are generally described. When a T3411 or T3402 timer is running and a MMTel voice or video call, or originating SMS is initiated at the UE, the UE ignores the timer and immediately initiates an Attach or TAU procedure. The UE does not immediately initiate the procedure when the event is a non-user-initiated event or when the T3346 timer is running. In certain circumstances, the UE also immediately initiates an Attach or RAU procedure when in Iu mode and a T3311 or T3302 timer is running.