Dynamic Vocoder Assignment in Group Calls
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Solution Overview
Problem
Current group communication systems, such as Push-to-Talk over Cellular (PoC), face challenges in maintaining optimal voice quality when new members join or network conditions change, as existing solutions require cumbersome negotiations and transcoding, which is inefficient, especially for mobile devices with limited resources.
Innovation Solution
A dynamic vocoder assignment method that evaluates and adjusts the optimal vocoder in real-time during a group call based on participant capabilities and network changes, using weighting factors to maximize voice quality and minimize transcoding, with SIP UPDATE and floor control messaging to inform participants of the best available codec.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a server transcodes the call for a terminal that does not have the capability for a particular codec, then voice quality can be maintained for all participants, but device complexity and processing overhead increase significantly
Solution Approach 1:
The system dynamically determines the optimal vocoder selection based on real-time evaluation of participant capabilities and network conditions, rather than using a static least-capable approach. The controller continuously monitors participant capabilities and adjusts vocoder assignment to maximize overall voice quality while minimizing transcoding requirements.
Solution Approach 2:
The system changes the parameter of vocoder selection from a fixed least-capable approach to a dynamic optimization based on multiple parameters including participant capabilities, network conditions, and call environment. This allows the system to select the best available vocoder that balances quality and complexity.
2Adaptability or versatility
If the system configures a group call to use a vocoder of the least capable member, then compatibility is maximized, but voice quality deteriorates for participants with higher capabilities
Solution Approach 1:
Instead of applying a uniform least-capable vocoder to all participants, the system allows different participants to experience different quality levels based on their individual capabilities. The controller evaluates each participant's capability and assigns vocoders accordingly, so that participants with higher capabilities can enjoy better voice quality while maintaining overall compatibility.
Solution Approach 2:
The system transitions from a static least-capable vocoder assignment to a dynamic selection process that continuously evaluates participant capabilities and network conditions. This allows the system to adapt vocoder assignment in real-time to maximize both compatibility and voice quality based on current system state.
3Ease of operation
If new members join an existing group call through traditional negotiation, then session establishment is achieved, but the process is cumbersome and existing terminals must be updated based on new terminal capabilities
Solution Approach 1:
The controller pre-evaluates participant capabilities and determines optimal vocoder selection before the actual call establishment. When new members join, the controller already has the capability information and can immediately determine the best vocoder assignment without requiring lengthy renegotiation protocols, thus reducing join time and complexity.
Solution Approach 2:
The system uses capability feedback from participants to dynamically adjust vocoder assignment. When new members join, their capability information is fed back to the controller, which then updates the vocoder selection for the entire group call, eliminating the need for cumbersome re-negotiation and reducing setup time.
4Reliability
If dynamic feedback is provided from user terminal to information sender, then voice quality can be optimized, but processing resources and system overhead increase considerably
Solution Approach 1:
The system enables participants to self-optimize their voice quality by having the controller automatically evaluate capabilities and select optimal vocoders without requiring explicit feedback requests or complex processing. The controller independently determines the best vocoder based on capability evaluation, reducing the processing burden on individual terminals while maintaining high voice quality.
Data Source
AI summary
An apparatus and method for dynamic vocoder assignment in a communication system that supports multiple vocoders includes a first step (30) of detecting changing a call environment in a group call. A next step (32) includes dynamically determining a list of vocoders in order of system preference in response to the change in call environment. A next step (34) includes communicating the ordered list of vocoders in an existing floor control message to the participants in the call. A next step (36) includes selecting, by at least the current transmitting participant, the first vocoder that it supports from the list of preferred vocoders, for use in that participant's next transmission in the group session.