SDP TTY Tone Signaling via Segmented Attributes
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Solution Overview
Problem
Current communication networks lack a method to signal whether an endpoint will be sending TTY tones, leading to inefficient resource usage and poor user experiences due to incompatible calls being established.
Innovation Solution
A new format-specific parameter in the SDP attribute line is introduced to indicate support for TTY tones, allowing devices to determine compatibility and avoid establishing unsupported calls, thereby saving resources and improving user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If endpoints only advertise codec support without indicating media format (TTY tones vs audio), then the signaling protocol remains simple, but incompatible calls are established wasting network resources
Solution Approach 1:
The patent segments the codec advertisement into two distinct parts: codec type identification and media format indication (TTY vs audio). This is achieved by introducing separate SDP attributes (a=tty and a=media-format) that independently signal TTY capability and media format, allowing receivers to make informed compatibility decisions without conflating codec and format information.
Solution Approach 2:
The patent applies preliminary action by having the sending endpoint indicate its intended media format (TTY tones or audio) in advance during the call setup phase via SDP attributes. This allows the receiving endpoint to assess compatibility before the call is fully established, preventing resource waste from incompatible calls.
2Reliability
If the network establishes all calls based on codec compatibility alone, then call establishment is straightforward, but TTY-capable endpoints may be connected to non-TTY endpoints causing poor user experience
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of SDP attributes (a=tty and a=media-format) that act as compatibility indicators between endpoints. These attributes provide the receiving endpoint with critical information about the sending endpoint's TTY capability and intended media format, enabling informed compatibility assessment before call establishment.
Solution Approach 2:
The receiving endpoint performs preliminary compatibility assessment by examining the SDP attributes during the call setup phase. This preliminary check determines whether the receiving endpoint should accept or reject the call based on TTY capability matching, ensuring reliable connectivity before resources are committed.
3Adaptability or versatility
If no media format indication is provided in SDP, then the protocol remains backward compatible, but network operators cannot avoid allocating resources for unsupported calls
Solution Approach 1:
The patent segments the SDP protocol into existing codec advertisement elements and new media format indication elements. The new attributes (a=tty and a=media-format) are added as optional extensions that do not interfere with existing SDP processing, allowing backward compatibility while enabling advanced format indication for modern endpoints.
Solution Approach 2:
The patent creates a universal signaling mechanism that serves multiple functions: it maintains backward compatibility with legacy endpoints that ignore the new attributes, while enabling format indication and compatibility assessment for modern TTY-capable endpoints. The SDP attributes can be optionally included or excluded based on endpoint capability.
Data Source
AI summary
A Session Initiation Protocol (SIP) message containing a Session Description Protocol (SDP) offer for a communications session is sent to 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. An error response is received that indicates the device has rejected the first parameter. Based on the error response to the first endpoint, a modified SIP message containing the SDP offer for the communications session is sent to the first endpoint. The SDP offer of the modified message excludes the first parameter indicating whether the communications session will include media encoding TTY data, audio data, or both TTY data and audio data.