VoIP Call Setup Failure Circuit-Switched Fallback Mechanism
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Solution Overview
Problem
VoIP call setup failures occur due to overloading of VoIP call servers, communication issues between packet gateways and VoIP call servers, or license limitations that prevent the assignment of dedicated VoIP bearers, resulting in poor user experience when the called party is available.
Innovation Solution
A method and apparatus that detect VoIP call setup failures and invoke a circuit-switched-fallback (CSFB) call by signaling between a fallback RAN and the UE, transitioning the UE to be served by a fallback RAN such as CDMA or GSM, allowing the setup of an alternate call via the fallback network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VoIP call setup is attempted through the packet-switched network, then the user can communicate using modern IP-based protocols, but the call setup may fail due to server overloading, communication issues, or license limitations
Solution Approach 1:
The system dynamically changes the network protocol parameter from VoIP (packet-switched) to circuit-switched fallback when detection indicates VoIP setup failure. This parameter change allows the call to succeed over an alternative protocol path, resolving the contradiction between maintaining VoIP reliability and adapting to network conditions.
Solution Approach 2:
The network node acts as an intermediary that detects VoIP call setup failures and initiates the fallback to circuit-switched calling. This intermediary function enables seamless transition between protocols without user involvement, improving call reliability while maintaining protocol flexibility.
2Ease of operation
If the system maintains a single calling method (VoIP), then the architecture remains simple, but the user experience deteriorates when VoIP setup fails
Solution Approach 1:
The system provides self-service fallback by automatically detecting VoIP call setup failures and initiating circuit-switched calling without user intervention. This self-service mechanism improves ease of operation while the automated detection and transition minimize the perceived complexity for the user.
Solution Approach 2:
The system prepares the fallback calling mechanism in advance by establishing the capability to detect VoIP failures and initiate circuit-switched calls. This preliminary preparation ensures that when VoIP setup fails, the fallback is already ready to execute, improving user experience without requiring complex real-time decision-making.
3Reliability
If dedicated VoIP bearers are assigned to UEs, then voice quality is improved with guaranteed bit rate, but license limitations prevent assignment in certain scenarios
Solution Approach 1:
Instead of insisting on dedicated VoIP bearers for quality assurance, the system inverts the approach by using circuit-switched calling as the primary reliable path when VoIP bearer assignment is blocked by license limitations. This inversion maintains voice quality through circuit switching while adapting to licensing constraints.
Data Source
AI summary
A network node through which VoIP call setup signaling passes between a user equipment device (UE) and a VoIP call server detects VoIP call setup failure and responsively invokes setup of an alternate call between the UE and the called destination. For instance, a packet-gateway in an LTE network may detect VoIP call setup failure and may responsively invoke setup of a circuit-switched fallback call between the UE and the called destination.