SRVCC Prohibition for VoLTE Roaming Latency

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Solution Overview

Problem

The Single Radio Voice Call Continuity (SRVCC) handover process in the S8HR roaming architecture fails to meet the requirement of maintaining voice interrupt latency within 300 ms, leading to poor user experience in VoLTE services when LTE network coverage is poor.

Innovation Solution

A voice roaming method is implemented where the mobility management network element determines if a terminal is roaming and supports VoLTE, and if so, prohibits the SRVCC function, notifying the access network element to prevent SRVCC procedures, and converts VoLTE calls to CSFB when LTE signal quality is low to avoid call drops.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If SRVCC handover is implemented in S8HR roaming architecture, then voice service continuity is maintained, but voice interrupt latency exceeds 300 ms requirement

Engineering Contradiction:

Improvevoice service continuityVSAvoidvoice interrupt latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts and removes the SRVCC handover function from the S8HR roaming architecture for roaming terminals. By prohibiting the SRVCC function at the mobility management network element level, the system eliminates the source of excessive latency while maintaining voice service continuity through alternative mechanisms.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of enabling SRVCC handover to ensure voice continuity, the patent inverts the approach by explicitly prohibiting SRVCC for roaming terminals. This inversion resolves the latency issue by preventing the problematic handover mechanism from being triggered in the first place.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If SRVCC procedure is triggered in poor LTE coverage area, then voice service continuity is attempted, but call drops occur due to excessive latency

Engineering Contradiction:

Improvevoice service continuityVSAvoidcall drops

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by preemptively prohibiting the SRVCC function before it can be triggered in poor coverage areas. The mobility management network element is configured to reject SRVCC requests for roaming terminals, preventing call drops that would result from excessive handover latency in challenging radio conditions.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system performs preliminary action by pre-configuring the mobility management network element to identify and prohibit SRVCC for roaming terminals. This preliminary prohibition prevents the harmful SRVCC handover process from being initiated in the first place, thereby avoiding call drops in poor coverage areas.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10390209B2Voice roaming method, mobility management network element, and access network element

Publication Date: 2019.08.20 HONOR DEVICE CO LTD

AI summary

A voice roaming method, a mobility management network element, and an access network element are provided. When determining that a terminal is a roaming terminal and supports a voice over Long Term Evolution (VoLTE) service in a roaming network, the mobility management network element prohibits a single radio voice call continuity (SRVCC) function of the terminal, and notifies the access network element, so that the access network element prohibits triggering an SRVCC procedure for the terminal.