MME Voice Session Selection via SRVCC Capability Feedback
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Solution Overview
Problem
LTE systems face reliability issues in voice sessions due to mismatches in Single Radio Voice Call Continuity (SRVCC) capability settings, leading to potential voice session losses when handover to 2G/3G systems fails.
Innovation Solution
A method and device that determine a mobile terminal's capability for handover to 2G/3G systems by using Feature Group Indicator (FGI) bits and Information Elements (IEs) to instruct the terminal to use Voice over LTE (VoLTE) or Circuit Switched (CS) fallback, ensuring compatible handover capabilities between the terminal and the LTE system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MME relies on SRVCC capability indication from the UE to determine voice session initiation method, then VoLTE service can be provided, but voice session reliability deteriorates due to capability mismatch between UE and LTE system
Solution Approach 1:
The patent implements feedback by having the eNB send FGI bits to the MME, providing accurate capability information about the UE's handover capabilities. This feedback mechanism allows the MME to make informed decisions about voice session initiation, resolving the reliability issue caused by inaccurate capability indications from the UE.
Solution Approach 2:
The eNB acts as an intermediary between the UE and the MME. Instead of the UE directly indicating its capabilities to the MME (which may be inaccurate), the eNB receives capability information from the UE and forwards relevant FGI bits to the MME, ensuring accurate capability information transmission for reliable voice session management.
2Adaptability or versatility
If the UE indicates SRVCC capability in Attach Request, then VoLTE can be initiated, but voice session continuity deteriorates when handover to 2G/3G fails due to capability mismatch
Solution Approach 1:
The patent applies preliminary action by having the eNB determine the UE's handover capabilities (via FGI bits) before the MME makes the voice session initiation decision. This advance capability assessment ensures that the MME selects the appropriate voice service mode (VoLTE or CS fallback) in advance, preventing session continuity failures during handover.
Solution Approach 2:
The patent changes the parameter used for capability indication from generic SRVCC capability bits in the Attach Request to specific FGI bits that accurately reflect the UE's handover capabilities. This parameter change enables the MME to make more accurate decisions about voice session initiation, improving both adaptability and session continuity reliability.
3Ease of operation
If the MME uses UE's SRVCC capability indication for voice domain selection, then service initiation is simplified, but handover failure risk increases due to capability mismatch
Solution Approach 1:
The patent maintains the simple feedback mechanism of the MME making the voice domain selection decision, but improves the accuracy of the feedback information by using FGI bits from the eNB instead of generic SRVCC capability bits. This ensures that the simplified decision-making process is based on accurate capability information, maintaining ease of operation while improving handover success rate.
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AI summary
A method (100) for use in a Mobility Management Entity, an MME, in an LTE system, comprising (110) obtaining and determining the capability of a mobile terminal in the LTE system regarding the mobile terminal's capability for handover over from the LTE system to a 2G and/or a 3G system, comparing (115) the mobile terminal's capability and the LTE system's capability for Single Radio Voice Channel Continuity, SRVCC, handover over from the LTE system to a 2G and/or a 3G system, and, depending on the outcome of the comparison, instructing (120, 125) the mobile terminal to use Voice over LTE, VoLTE, or Circuit Switched, CS, fallback when initiating voice sessions.