LS on Initiation of New Work Item Q.IMS-INT-RS "IMS Interconnection Restoration Architecture and Procedures"

Document Overview

This is a Liaison Statement (LS) from ITU-T Study Group 11 to 3GPP (for information) announcing the initiation of a new work item Q.IMS-INT-RS on "IMS interconnection restoration architecture and procedures" during the ITU-T SG11 meeting in Geneva, November 17-26, 2025.

Main Technical Contribution

New Work Item Initiation

ITU-T SG11 has initiated work on Q.IMS-INT-RS, which specifies restoration architecture and procedures based on a shared backup interconnection point to enhance service resilience in IMS interconnection scenarios.

Scope of Q.IMS-INT-RS

The draft Recommendation covers the following technical areas:

1. Restoration Architecture

• Defines the restoration architecture for IMS interconnection
• Focuses on shared backup interconnection point mechanisms

2. Service Interruption Conditions

• Specifies conditions under which IMS interconnection service interruptions occur
• Identifies scenarios requiring restoration procedures

3. Restoration Signaling Procedures

• Details the signaling procedures for IMS interconnection restoration
• Defines protocol interactions for failover and recovery

4. Interface Descriptions

• Provides interface descriptions specific to IMS interconnection restoration
• Defines reference points and protocols for restoration mechanisms

Collaboration Request

ITU-T SG11 is seeking collaboration with 3GPP on this subject matter, given the relevance to IMS interconnection which is a key area of 3GPP specifications.

Reference Documents

The baseline text of Q.IMS-INT-RS is available in SG11-TD657/GEN (attached to the LS).

Summary of DECT Liaison Statement on LC3plus 1.25ms Frame Duration Availability

Document Overview

This is a Liaison Statement from ETSI TC DECT to 3GPP SA4 (S4-260032) responding to a previous 3GPP request (S4-241377) regarding LC3plus integration in 3GPP ISAR. The document announces the availability of a new LC3plus specification version with ultra-low-delay capabilities.

Main Technical Contributions

New LC3plus Version Release

ETSI TC DECT announces the publication of ETSI TS 103 634 V1.6.1 (October 2025), which includes both updated specification text and reference software.

Ultra-Low-Delay Mode Specifications

The key technical addition is a new 1.25ms frame duration mode with the following characteristics:

• Frame duration: 1.25ms
• Total algorithmic delay: 2.5ms
• Bitrate range: 128 to 512 kbps per channel
• Target application: 3GPP audio services with very tight latency requirements

Additional Updates in V1.6.1

The revision includes several maintenance and compatibility improvements:

• Bug fixes and maintenance for all legacy modes
• Improved compatibility of floating-point software with the STL WMC (Weighted Million Operations) complexity estimation tool

Context and Future Updates

ETSI TC DECT indicates this update directly addresses 3GPP SA4's previous liaison regarding LC3plus integration in ISAR and commits to providing future updates on new revisions of ETSI TS 103 634.

Reply LS to CTA WAVE on CMCD Phase 2

Document Information

Meeting: 3GPP TSG-SA4 Meeting #135 (S4-260033)
Date: 9-13 February 2026, Goa, India
Response to: S4-251997
Release: Rel-20
Work Item: FS_AMD_Ph2, AMD_PRO-MED
Source: CTA WAVE
To: 3GPP TSG SA WG4
Cc: SVTA DASH-IF WG, ISO/IEC JTC1 SC29 WG03 (MPEG Systems)
Contact: Will Law (wilaw@akamai.com)

Overview

This is a Liaison Statement (LS) from CTA WAVE to 3GPP SA4 regarding CMCD (Common Media Client Data) Phase 2 development. The document serves as a reply to a previous LS (S4-251997).

Key Technical Contributions

CMCD Version 2 Status

The LS indicates that CTA WAVE has provided an email received and a CMCDv2 Release Candidate as attachments to this liaison statement.

Coordination Activities

This liaison represents ongoing coordination between: - CTA WAVE (Consumer Technology Association Web Application Video Ecosystem) - 3GPP SA4 (Service and System Aspects Working Group 4 - Codec and Media) - SVTA DASH-IF WG (Streaming Video Technology Alliance - DASH Industry Forum Working Group) - ISO/IEC JTC1 SC29 WG03 (MPEG Systems)

Work Item Context

The LS is associated with two work items: - FS_AMD_Ph2: Feasibility Study on Adaptive Media Delivery Phase 2 - AMD_PRO-MED: Adaptive Media Delivery for Professional Media

Purpose

This reply LS appears to be providing 3GPP SA4 with the latest CMCDv2 Release Candidate documentation for review and consideration in the context of the ongoing Adaptive Media Delivery Phase 2 work and Professional Media activities in Release 20.

LS on Subjective Quality Evaluation of AI-based Ultra-low Bitrate Voice Codecs

Document Information

Source: ITU-T Study Group 12
Reference: SG12-LS18 (SG12-TD298R1)
Date: Geneva, 9-18 September 2025
For Information to: 3GPP SA4
Deadline: June 2026

Background and Context

ITU-T SG12 reviewed multiple contributions during its September 2025 meeting addressing ML- and AI-based speech processing features and their evaluation using subjective tests and objective models. A key contribution (SG12-C40) from Rohde & Schwarz SwissQual AG presented P.800 listening test results that included several AI-based ultra-low bitrate codecs.

Main Technical Findings

Performance of AI-based Ultra-low Bitrate Codecs

The P.800 listening tests demonstrated that several AI-based ultra-low bitrate codecs scored better than traditional low-bitrate codecs, proving their usefulness in the telecommunication context.

Limitations of Current Test Methodologies

While the P.800 overall MOS rating procedure appears generally appropriate for evaluating these codecs, SG12 identified potential limitations:

• Timbre shifts may not be adequately reflected in traditional MOS ratings
• Small drops in information that could be critical in mission-critical calls might not be captured
• New test methods that better reflect these perceptual effects may be necessary

E-model Integration Concerns

SG12 concluded that it would be premature to incorporate these AI-based codecs into the E-model (by deriving equipment impairment factors) due to:

• Subjective effects not yet fully covered by available test methods
• Rapid evolution and changes in the respective codec technologies

Request for Feedback

ITU-T SG12 is seeking feedback from 3GPP SA4 based on their experience before deciding to:

• Start development of new appropriate subjective test methodologies
• Develop potential corresponding prediction models

The liaison includes attachment SG12-C40 describing a subjective ACR LOT testing of AI-based and ultra-low bitrate codecs in a full-scale real field context.