Discussion of Using a Single DC Stream for Multi DC Application Data Transmission

Overview

This contribution from China Mobile discusses potential issues with the current DC (Data Channel) application data transmission mechanism and proposes enhancements to support multiple DC applications over a single DC stream.

Problems with Current DC Mechanism

Resource and Implementation Limitations

• Current standard requires each DC application to establish a dedicated ADC (Application Data Channel) with its server or peer terminal before data transmission
• Theoretical support exists for numerous DC channels per call session, but practical implementations face constraints:
• Resource consumption and power usage limitations
• Current chip implementations support only up to 4 ADC bearers per session
• Limited number of bearers cannot flexibly support diverse DC applications with different QoS requirements and destination endpoints

Latency and User Experience Issues

• Each DC application opening requires DC bearer negotiation, introducing 100-500 ms delay
• Sequential application switching (closing DC application 1 and immediately opening DC application 2) can cause negotiation conflicts with non-robust terminal implementations

Signaling Conflicts

• DC applications designed for immediate service upon call answering (e.g., call captioning, translation, background replacement, real-time transcription) face high risk of signaling conflicts
• When both calling and called parties have subscribed to related services, simultaneous DC negotiation requests at call answer time create conflict scenarios

Proposed Solution

Core Suggestion

Support a common DC channel shared among multiple DC applications with the following approach:

• For ordinary data interaction: DC applications can directly request data transmission without first establishing a dedicated DC bearer
• For special requirements: DC applications with specific transport protocol or QoS requirements still need to establish dedicated ADC before data transmission

Solution 1 Details

• Define a generic ADC with fixed stream IDs
• Enable DCSF (Data Channel Selection Function) to support distribution of data from multiple DC applications
• Extend the ADC concept to allow ADC channels with specific stream IDs to carry data for multiple DC applications

Proposal

Study whether to use and how to enhance DC to support multiple DC Application Data Transmission in a single DC stream.