SSRC Value Exchange in Multi-Talker MCPTT Floor Control

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Solution Overview

Problem

There is no defined mechanism in 3GPP Mission Critical Services (MCX) specs to exchange the SSRC value between client and server for implicit floor requests in Multi-Talker MCPTT calls.

Innovation Solution

The method involves sharing the SSRC value as a Format Specific Parameter (FMTP) media attribute of a Session Description Protocol (SDP) in an outgoing INVITE request from the client to the server, and receiving the same or a new SSRC value formatted in the 200 OK response, depending on its availability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If implicit floor request method is used in MCPTT calls, then the floor control process is simplified, but there is no mechanism defined to exchange SSRC value between client and server

Engineering Contradiction:

Improvefloor control processVSAvoidSSRC value exchange mechanism

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The patent merges the SSRC value exchange mechanism into the existing SDP offer/answer procedure. The client includes the SSRC value in the SDP offer of the INVITE request, and the server responds with the same or a new SSRC value in the SDP answer of the 200 OK response. This combining of functions allows implicit floor requests to work seamlessly without requiring a separate SSRC exchange mechanism.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The SDP (Session Description Protocol) acts as an intermediary mechanism to facilitate SSRC value exchange. By using SDP attributes within the SIP signaling framework, the patent provides a standardized way for clients and servers to exchange SSRC values indirectly through the offer/answer model, resolving the missing mechanism issue.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple clients transmit simultaneously in MCPTT calls, then communication flexibility is improved, but SSRC value collision may occur without proper management

Engineering Contradiction:

Improvecommunication flexibilityVSAvoidSSRC value uniqueness

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The server provides feedback to the client regarding the SSRC value status. When the client sends its desired SSRC value in the SDP offer, the server responds in the SDP answer with either the same SSRC value (indicating availability) or a new SSRC value (indicating the original was in use). This feedback mechanism ensures SSRC value uniqueness while allowing multiple clients to transmit simultaneously.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The client performs preliminary action by including its desired SSRC value in the SDP offer before the actual media transmission begins. This advance declaration of SSRC intent allows the server to check for conflicts and resolve them before the call is established, preventing collisions during simultaneous transmissions.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12342412B2Method and apparatus for communication in communication system supporting multi-talker mission critical push-to-talk (MCPTT)

Publication Date: 2025.06.24 SAMSUNG ELECTRONICS CO LTD

AI summary

In an example embodiment of present disclosure, a method and apparatus to exchange an SSRC value between a client and a server for implicit floor requests are disclosed. In an embodiment, the exchange of the SSRC value between the client and the server for implicit floor requests is being done with Explicit Grant Support during a Multi-Talker MCPTT call where the SSRC sharing in FMTP media attribute of Session Description Protocol (SDP). In an embodiment, exchange of the SSRC value between the client and the server for implicit floor requests is being done with Implicit Grant Support during a Multi-Talker MCPTT call where the SSRC sharing in FMTP media attribute of SDP. In an embodiment, exchange of the SSRC value between the client and the server for implicit floor requests is being done with Implicit/Explicit Grant Support during a Multi-Talker MCPTT call where the SSRC sharing in SSRC and FMTP media attribute of SDP.