VoIP Multicast Audio Broadcasting Synchronization

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Solution Overview

Problem

VoIP communication systems do not support multicast transmission, leading to high bandwidth requirements and synchronization issues in broadcasting audio messages to multiple recipients, particularly in large areas like railway tunnels, where audio signals from multiple speakers can disturb message reception.

Innovation Solution

A communication system using VoIP technology with a multicast communication server that employs SIP protocol for establishing communication, SDP for RTP sessions, and IGMP for multicast session announcements, allowing for synchronized broadcasting of audio messages over an Ethernet network, ensuring high audio quality and minimal end-to-end delay.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If VoIP communication systems are used for multicast transmission, then network configuration and device management are simplified, but bandwidth requirements increase and synchronization of audio channels is not guaranteed

Engineering Contradiction:
Improvenetwork configuration and device managementVSAvoidsynchronization of audio channels
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The patent introduces a multicast communication server as an intermediary component that manages the VoIP multicast transmission. This server coordinates the audio streams from multiple sources, ensuring proper synchronization and timing while maintaining the simplicity of VoIP-based network configuration and device management through standardized protocols like SIP and IGMP.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Ease of manufacture

If traditional multi-conference systems with PBX are used, then audio mixing and distribution are achieved, but bandwidth consumption is high and synchronization is not guaranteed

Engineering Contradiction:
Improveaudio mixing and distribution capabilityVSAvoidbandwidth consumption
Core Design Contradiction:
Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent segments the audio transmission into synchronized multicast streams distributed over IP networks, replacing the monolithic PBX approach. This segmentation allows efficient bandwidth utilization by transmitting audio packets in synchronized intervals rather than continuous streams, reducing overall bandwidth consumption while maintaining audio mixing and distribution capabilities through software-based coordination.

Inventive Principle:
Principle #1Segmentation

3Area of stationary object

If audio messages are broadcast through multiple speakers in large areas, then coverage area is increased, but audio signal distortion occurs due to combination of contributions from multiple speakers

Engineering Contradiction:
Improvecoverage areaVSAvoidaudio signal distortion
Core Design Contradiction:
Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary timing adjustments and synchronization protocols before the audio broadcast begins. The multicast communication server pre-calculates transmission timing and synchronization parameters, ensuring that audio contributions from multiple speakers are coordinated to arrive at listeners' locations in a synchronized manner, preventing distortion while maintaining wide area coverage.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP2202915B1Communication system for broadcasting audio messages in multicast mode
Publication Date: 2017.08.16 ALSTOM TRANSPORT TECH SAS
  • EP2202915B1 patent drawingFigure 1
  • EP2202915B1 patent drawingFigure 2
  • EP2202915B1 patent drawingFigure 3

AI summary

A communication system for broadcasting audio messages in multicast mode, comprising: a Voice over IP (VoIP) audio communication network, which network comprises at least one transmit/receive client unit and one or more receiver units for broadcasting the audio message sent by the at least one transmit/receive unit and at least one exchange for connection of the transmit/receive client unit/s and the receiver unit via an Ethernet network, each transmit/receive client unit and each receiver unit being uniquely identified by an IP address, According to the invention, the connection exchange comprises a PBX for connecting the transmit/receive client units and the receiver units to a multicast communication server unit, which unit comprises a multicast streamer, a receive/transmit terminal connected to the PBX for communication with the transmit/receive client unit and means for transmitting a message in multicast mode to the receiver units or to a predetermined number of selected receiver units among the available receiver units.