TTY Tone Support Signaling Through SDP Format Parameters

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Solution Overview

Problem

Existing communication networks fail to indicate whether an endpoint will send TTY tones, leading to inefficient resource use and poor user experience due to incompatible calls, as endpoints may not have TTY capability, resulting in wasted bandwidth and incorrect interworking.

Innovation Solution

Introduce a new format specific parameter in the Session Description Protocol (SDP) attribute line to signal the support of TTY tones, allowing devices to determine compatibility and avoid establishing unsupported calls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If endpoints advertise supported codecs without indicating media format (TTY tones vs audio), then calls can be connected based on codec compatibility, but network resources are wasted on incompatible calls and user experience deteriorates

Engineering Contradiction:

Improvecall connection efficiencyVSAvoidnetwork resource waste

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by introducing a format specifier parameter in the SDP offer that indicates whether TTY tones will be sent before the call is actually established. This allows the receiving endpoint and intermediate devices to determine compatibility in advance and reject incompatible calls before allocating network resources, thus preventing resource waste while maintaining efficient call connection for compatible endpoints

Inventive Principle:

Principle #10Preliminary action

2Reliability

If endpoints send TTY media without indicating format, then codec matching can be established, but TTY capability mismatch occurs causing poor user experience

Engineering Contradiction:

Improvecodec matching reliabilityVSAvoidTTY compatibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent uses an intermediary approach by introducing a format specifier parameter that acts as a mediator between the codec advertisement and the actual media transmission. This parameter provides additional information about the media format (TTY tones vs audio) that allows intermediate devices and receiving endpoints to properly assess compatibility, ensuring both codec matching and TTY capability alignment

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If no format indication is provided in SDP, then call setup is simple, but incompatible calls cannot be detected early

Engineering Contradiction:

ImproveSDP signaling complexityVSAvoidcall establishment time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent applies parameter changes by extending the existing SDP format specifier parameter to include media format information (TTY tones indication). This modification adds only a small amount of information to the existing signaling protocol, maintaining simplicity while enabling early detection of incompatible calls and preventing wasted call establishment time

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12425516B2Indication of tone support via format specifier

Publication Date: 2025.09.23 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

A device receives a Session Initiation Protocol (SIP) message containing a Session Description Protocol (SDP) offer for a communications session from a first endpoint. The SDP offer includes a first parameter indicating whether the communications session will include media encoding TTY data, audio data, or both TTY data and audio data. The device reads the first parameter and sends an SDP answer including a second parameter indicating whether the device is configured to process media encoding TTY data, audio data, or both TTY data and audio data.