Session Negotiation for Seamless Codec Switching in Cellular Systems
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Solution Overview
Problem
Introducing a new speech codec into a communication system is challenging due to interoperability issues with legacy equipment, which often requires additional transcoders or complex capability exchanges, leading to increased costs and potential speech quality degradations, especially in scenarios like multi-party conferencing and hand-over scenarios.
Innovation Solution
A method for negotiating a new codec type during an ongoing session by agreeing on a first codec type, exchanging media frames, and then providing an indication for a second codec type, allowing clients to switch seamlessly without requiring new session negotiation, utilizing existing SIP/SDP signaling and CMR bits for backward compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a new speech codec is introduced into the communication system, then service quality is improved, but interoperability with legacy equipment deteriorates
Solution Approach 1:
The patent uses SDP (Session Description Protocol) as an intermediary mechanism to negotiate codec compatibility between new and legacy terminals. The SDP capability exchange acts as a mediator that enables interoperability by allowing terminals to advertise and negotiate supported codecs before establishing a session, thus resolving the contradiction between introducing new codecs and maintaining compatibility with legacy equipment.
Solution Approach 2:
The patent implements preliminary capability exchange between terminals using SDP before the actual speech session is established. This preliminary action allows both terminals to identify common supported codecs in advance, ensuring interoperability is established before the session begins, thereby resolving the contradiction between new codec introduction and legacy compatibility.
2Adaptability or versatility
If transcoders are provisioned in media gateways to translate between new and old coding formats, then interoperability is improved, but network investment and maintenance costs increase
Solution Approach 1:
The patent extracts the codec translation function from the network infrastructure (media gateways and transcoders) and moves it to the terminal devices themselves. By enabling terminals to perform local codec selection and switching based on SDP capability exchange, the solution eliminates the need for network-based transcoders, thereby reducing network investment and maintenance costs while maintaining interoperability.
Solution Approach 2:
The patent enables terminals to self-negotiate codec compatibility through SDP capability exchange without requiring network-based transcoding services. Each terminal independently determines the common codec it can use with the other terminal, making the system self-sufficient and eliminating the need for expensive network transcoder infrastructure.
3Adaptability or versatility
If capability exchange between terminals is implemented prior to call, then interoperability is improved, but implementation complexity and technology licensing costs increase
Solution Approach 1:
The patent leverages the existing SDP protocol, which is already universally used in IMS for session description and capability exchange. By reusing this established protocol for codec negotiation purposes, the solution avoids the need for separate proprietary capability exchange mechanisms, thereby reducing implementation complexity and technology licensing costs while maintaining improved interoperability.
4Adaptability or versatility
If legacy codecs are provided alongside new codecs in terminals, then interoperability is improved, but implementation costs increase
Solution Approach 1:
The patent implements partial codec support in terminals by using SDP capability exchange to negotiate only the common codecs that both terminals support. Rather than requiring terminals to implement all possible codecs, the solution allows terminals to selectively support a subset of codecs and use SDP to negotiate compatibility, thereby reducing implementation and licensing costs while maintaining interoperability through selective codec usage.
Data Source
AI summary
In a method of improved session negotiation between first and second clients in a cellular telecommunication system, the two clients negotiating S10 and agreeing upon a first codec type for a session. The first and second clients then initiating the session and exchanging S20 media data frames according to the first codec type. Subsequently, during the initiated session, at least one of the first and second clients providing S30 an indication for a second codec type in at least one subsequent media data frame. Finally, upon receiving and recognizing said indication, the other of said first and second clients switching S40 to the indicated second codec type in a next media data frame, thereby enabling the first and second clients to exchange subsequent media frames utilizing the second codec type.