Timeplan for FS_ULBC Study Item

1. Introduction

This document outlines the timeplan for the Feasibility Study on Ultra Low Bitrate Speech Codec (FS_ULBC). The study focuses on developing a codec for ultra-low bit rate communication services, particularly for IMS Voice Call Using GEO Access as documented in TR 22.887.

Study Item Objectives

The FS_ULBC study has nine main objectives:

1. Application Scenarios: Document ultra-low bit rate communication service scenarios based on TR 22.887 use cases and requirements for IMS Voice Call Using GEO Access
2. GEO Channel Characteristics: Study GEO channel characteristics and derive service-related dependencies (bitrates, mouth-to-ear delay, loss/delay/jitter profiles)
3. Note: NB-IoT services impact is out of scope
4. Design Constraints: Identify relevant design constraints in coordination with other WGs:
5. Bit rates
6. Sample rate and audio bandwidth
7. Frame length
8. Complexity and memory demands
9. Algorithmic delay
10. Packet loss concealment (PLC)
11. Potential noise suppression integration
12. Discontinuous transmission (DTX) including VAD and comfort noise
13. Speech quality
14. Robustness to non-speech input
15. Feasibility Evidence: Provide evidence that design criteria can be met using existing reference codecs
16. Performance Requirements: Define performance requirements and identify test methodologies for:
17. Speech quality and intelligibility
18. Conversational quality
19. Clean and noisy speech conditions
20. Tandeming with existing IMS voice codecs
21. Clean channel and GEO channel conditions
22. Objective Measures: Identify or develop objective measures to verify design constraints (e.g., complexity and memory measurements)
23. Reference Codecs: Identify relevant reference codecs for comparison and evaluation
24. Coordination: Coordinate with other 3GPP groups (SA2, RAN, CT1, etc.)
25. Normative Work: Define potential normative work item objectives and timeline

2. Current Progress Status

Application Scenarios (85% Complete)

• Scenario 1: IMS Voice Call over GEO (TR 4.2, P-doc 4.1)
• Scenario 2: Multi-Party Voice Communication (TR 4.3)
• Scenario 3: IMS Voice Call with ULBC over other access types than GEO (TR 4.4)
• Next Steps: Finalize high-level prerequisites and resolve ENs
• Dependencies: SA2, RAN, CT

GEO Channel Characteristics & Simulation (75% Complete)

• NB-IoT system design and simulation parameters documented (TR 5.1.4, P-doc 5.2.2)
• SA4#135 Plans:
• Finalize remaining parameters
• Gather candidate Transport Block Sizes (TBS)
• Dependencies: SA2, RAN

Simulation Methodology (60% Complete)

• SA4#135 Plans: Discuss and confirm simulation methodology
• Dependencies: RAN

Company Simulation Results (40% Complete)

• Companies providing simulation results (P-doc 5.2.3)
• SA4#135 and Post Ad-hoc Plans:
• Select appropriate TBS
• Collect company simulation results
• SA4#136 Plans:
• Cross-check simulation results
• Finalize feasible TBS values and loss traces

Mouth-to-Ear Delay (95% Complete)

• Documented in TR 5.1
• Next Steps: Resolve ENs

Design Constraints Progress

Bit Rates (0% Complete)

• SA4#136 and Post Ad-hoc: Decide bit rates for ULBC (dependent on simulation results)
• Dependencies: RAN

Sample Rate and Audio Bandwidth (5% Complete)

• SA4#135 and Post Ad-hoc: Discuss supported audio bandwidth
• SA4#136 and Post Ad-hoc: Decide supported audio bandwidth

Frame Length (0% Complete)

• SA4#136 and Post Ad-hoc: Decide frame length for ULBC

Complexity and Memory Demands (80% Complete)

• Documented in TR 6.2.1, P-doc 6.1.1
• SA4#135 and Post Ad-hoc: Finalize complexity measurement metrics and resolve ENs

Algorithmic Delay (0% Complete)

• SA4#135 and Post Ad-hoc: Discuss algorithm delay for ULBC

Packet Loss Concealment (15% Complete)

• Documented in TR 7.1.5
• SA4#135 and Post Ad-hoc: Discuss PLC for ULBC

Noise Suppression (15% Complete)

• Documented in TR 7.4
• SA4#135 and Post Ad-hoc: Discuss noise suppression for ULBC

DTX (0% Complete)

• SA4#135 and Post Ad-hoc: Discuss DTX support for ULBC

Design Constraint Verification (5% Complete)

• P-doc 6.3.1
• Next Steps: Verify design constraints

Other Considerations (5% Complete)

• TR 6.4.1
• Next Steps: Document additional design considerations and resolve ENs

Existing Codec Technologies (85% Complete)

• Reference codecs documented (e.g., DAC, Lyra) in TR 7
• SA4#135 and Post Ad-hoc: Continue documenting evidence of existing technologies and resolve ENs

Performance Requirements (0% Complete)

• SA4#136 and Post Ad-hoc: Define performance requirements

Test Methodologies (50% Complete)

• Subjective test methodologies documented in TR 9.1.3
• SA4#135 and Post Ad-hoc: Identify appropriate test methodologies

Coordination with Other WGs

• Analysis of current liaisons from RAN, CT, and SA2 available (S4aA250139)
• Ongoing coordination as needed

3. Detailed Timeplan

TSG SA#107 (March 12-14, 2025, Incheon, KR)

• Approval of FS_ULBC study item

SA4#131-bis-e (April 11-17, 2025)

• Start documenting application scenarios for ultra-low bit rate communication services
• Start studying GEO channel characteristics and service-related dependencies
• Start identifying relevant reference codecs
• Start coordinating with other 3GPP groups

Audio SWG Telco (May 5, 2025)

• Focus on application scenarios and technical contributions

SA4#132 (May 19-23, 2025, Fukuoka, JP)

• Finalize application scenarios documentation
• Progress GEO channel characteristics study
• Progress reference codec identification
• Progress coordination with other WGs
• Start identifying/developing objective measures for design constraint verification
• Start identifying relevant design constraints (bit rates, sample rate, frame length, complexity, algorithmic delay, PLC, noise suppression, DTX, speech quality, robustness)
• Start providing feasibility evidence using existing reference codecs
• Start defining performance requirements and test methodologies for speech quality
• If time permits: Start documenting additional application scenarios

Audio SWG Telcos (June-July 2025)

Multiple telcos scheduled to:
- Progress GEO channel characteristics study
- Perform RAN-related simulations within SA4
- Align on RAN link-level simulations
- Power to send LS to SA2 and RAN WGs if needed

SA4#133-e (July 21-25, 2025)

• Progress all ongoing work items:
• GEO channel characteristics
• Coordination with other WGs
• Reference codec identification
• Objective measures development
• Design constraints identification
• Feasibility evidence
• Performance requirements and test methodologies
• If time permits: Progress additional application scenarios

F2F Ad-hoc Meeting (September 23-25, 2025, Erlangen, Germany)

• Hosted by Fraunhofer IIS
• Electronic participation on best effort basis

Audio SWG Telcos (October 2025)

• Opportunity for feedback from other WGs
• Progress work on:
• GEO channel characteristics study
• Existing technologies documentation
• Design constraints identification
• Performance requirements and test methodologies
• Application scenarios if time permits

SA4#134 (November 17-21, 2025, Dallas, US)

Major milestone meeting:
- Finalize:
- GEO channel characteristics study
- Coordination with other WGs
- Reference codec identification
- Design constraints: bit rates, sample rate, audio bandwidth, frame length, PLC, noise suppression, DTX
- Progress:
- Feasibility evidence
- Objective measures development
- Design constraints: complexity, algorithmic delay, speech quality, robustness
- Performance requirements and test methodologies
- Start defining potential normative work item objectives and timeline
- If time permits: Finalize additional application scenarios

Audio SWG Telcos (December 2025 - January 2026)

• Finalize GEO channel characteristics study
• Progress:
• Simulation parameters for end-to-end simulation
• Existing technologies documentation
• Design constraints identification
• Performance requirements and test methodologies
• Application scenarios if time permits
• Power to send reply LS for incoming LS postponed during SA4#134

SA4#135 (February 9-13, 2026, India)

• Finalize objective measures for design constraint verification
• Progress:
• Design constraints: complexity, algorithmic delay, speech quality, robustness
• Feasibility evidence
• Performance requirements and test methodologies

TSG SA#111 (March 10-13, 2026, Japan)

• TR for information

SA4#136 (April 13-17, 2026)

• Finalize:
• Design constraints: complexity, algorithmic delay, robustness to non-speech input
• Feasibility evidence
• Progress:
• Design constraints: speech quality
• Performance requirements for speech quality

SA4#137 (May 11-15, 2026)

Final study meeting:
- Finalize:
- Design constraints: speech quality
- Performance requirements and test methodologies (clean/noisy speech, tandeming, clean/GEO channel conditions)
- Potential normative work item objectives and timeline

TSG SA#112 (June 9-12, 2026, Singapore)

• TR for approval - Study completion