Call Handover Control During Call Attempt States
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Solution Overview
Problem
Current wireless communication technologies, such as 3GPP Release 7, do not support seamless handover of calls during a call attempt, specifically during ringing or ring-back tone periods when transferring between Circuit Switched (CS) and IP Multimedia Subsystem (IMS) domains, leading to call failures due to detachment of Media Gateways and lack of Answer message transfer.
Innovation Solution
A method and system that determine whether a User Equipment (UE) is engaged in a call attempt before initiating handover from one network to another, prohibiting handovers during call negotiation, ringing, or ring-back tone periods, and using pending messages to manage handover requests during these states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If handover is initiated during call attempt (ringing or ring-back tone period), then network flexibility and mobility are improved, but call completion reliability deteriorates due to Media Gateway detachment and Answer message transfer failure
Solution Approach 1:
The system performs preliminary detection of call attempt state before allowing handover. The network entity (MSC or SGSN) checks whether the UE is in a call attempt state (ringing or ring-back tone) prior to initiating handover. If a call attempt is detected, the handover is prohibited, preventing the reliability issues that would occur during Media Gateway detachment and Answer message transfer.
2Reliability
If handover is prohibited during call attempt, then call completion reliability is improved, but network mobility and adaptability deteriorate
Solution Approach 1:
The handover control mechanism is dynamic rather than static. The system adapts handover behavior based on the current call state: handover is permitted during normal operation and after call completion, but prohibited specifically during call attempt periods when reliability issues would occur. This dynamic approach maintains network mobility while protecting against reliability degradation.
3Productivity
If Media Gateway is detached during handover from CS to IMS domain, then network resource efficiency is improved, but ring-back tone delivery and call establishment reliability deteriorate
Solution Approach 1:
The network performs preliminary detection of call attempt state before initiating handover. By detecting whether the UE is in a call attempt state (where ring-back tone delivery is critical) before detaching the Media Gateway, the system prevents reliability issues while still enabling resource efficiency during appropriate handover scenarios.
4Difficulty of detecting and measuring
If Answer message transfer is blocked during handover, then network control precision is improved, but called UE communication reliability deteriorates
Solution Approach 1:
The network performs preliminary detection of call attempt state before allowing handover. By detecting the call state in advance, the network can precisely control whether handover (and thus Answer message transfer blocking) should occur, achieving both control precision and communication reliability through state-aware decision making.
Data Source
AI summary
A method for controlling a call handover between telecommunication networks includes determining whether a User Equipment (UE), in communication with a first network, is engaged in a call attempt when the UE is to be transferred from the first network to a second network, if the UE is engaged in a call attempt, maintaining the UE communicating with the first network, and if the UE is not engaged in a call attempt, initiating the handover from the first network to the second network.