SRVCC Handover Identification via RAB Info Elements

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Solution Overview

Problem

Existing inter-RAT handover procedures between LTE and UTRAN networks face challenges in determining whether a handover is an SRVCC handover and in performing the handover efficiently, particularly due to the absence or presence of specific information elements in handover command messages.

Innovation Solution

The system and method for determining and performing SRVCC handovers involve receiving handover command messages with or without 'RAB info to replace' information elements, using a circuit-switched RAB from the 'RAB information for setup' element to facilitate handovers, and discarding invalid messages to prevent unnecessary handovers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the handover command message includes 'RAB info to replace' information element, then the SRVCC handover procedure can be properly identified and executed, but the message format becomes more complex and requires additional processing

Engineering Contradiction:

ImproveSRVCC handover execution reliabilityVSAvoidhandover command message structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the parameter state of the handover command message by conditionally including or excluding the 'RAB info to replace' information element. When performing SRVCC handover, this element is included to enable proper identification and execution of the handover procedure. For non-SRVCC handovers, the element is omitted, simplifying the message structure. This parameter-based approach allows the system to adapt the message format to the specific handover type being performed.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the handover command message does not include 'RAB info to replace' information element, then the message structure remains simple, but the UE cannot properly determine whether to perform SRVCC handover

Engineering Contradiction:

Improvehandover command message structureVSAvoidSRVCC handover identification information

Core Design Contradiction:

Device complexityVSLoss of information

Solution Approach 1:

The patent applies preliminary action by preparing the 'RAB info to replace' information element in advance when the network determines that an SRVCC handover is required. This element is included in the handover command message before transmission to the UE, allowing the UE to proactively identify and execute the SRVCC handover procedure without ambiguity. The network performs this information preparation beforehand, ensuring the UE receives complete and unambiguous handover instructions.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the UE discards handover command messages without 'RAB info to replace' information element, then invalid messages are filtered out, but legitimate SRVCC handover messages may be incorrectly rejected

Engineering Contradiction:

Improvehandover message validationVSAvoidhandover execution efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent implements feedback mechanisms where the network monitors UE responses to handover command messages. When a UE discards a message or reports failure, the network receives this feedback and can adjust its message generation accordingly. For SRVCC handovers, the network ensures the 'RAB info to replace' element is included, preventing incorrect rejection. This feedback loop allows the system to learn from validation outcomes and improve message generation accuracy.

Inventive Principle:

Principle #23Feedback

4Stability of the object's composition

If the UE attempts to perform handover without proper SRVCC information elements, then handover continuity may be maintained, but the handover may fail due to missing critical information

Engineering Contradiction:

Improvehandover continuityVSAvoidhandover execution success

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent applies beforehand cushioning by including the 'RAB info to replace' information element in advance within the handover command message for SRVCC handovers. This preemptive inclusion of critical information elements ensures that the UE has all necessary data to successfully execute the handover procedure. By preparing and transmitting this information beforehand, the system cushions against potential handover failures that would occur if the UE attempted to perform handover with incomplete information.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentEP2365708B1Method and apparatus for handling SRVCC in an inter radio access technology handover

Publication Date: 2015.11.11 HTC CORP

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AI summary

The techniques introduced herein provide a system and method for determining whether an inter-RAT handover is an SRVCC handover, and for performing the subsequent SRVCC handover. The techniques include receiving a handover command message that does not include SRVCC related information elements, for example "RAB info to replace," but continuing with an SRVCC handover using a circuit-switched RAB provided in the information for setup. The techniques also include receiving a handover command message that does include SRVCC related information elements and performing the SRVCC handover by an alternative method.