DTMF Signal Extraction in VoIP Switching Devices
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Solution Overview
Problem
In VoIP environments, the recognition of DTMF characters by switching devices like PABX is hindered because the payload channel, where DTMF signals are transmitted, is not routed through the exchange, preventing the control of performance features during conversations.
Innovation Solution
A method where a signal processing device, separate from the switching device, recognizes and filters out DTMF characters from the payload stream based on SIP or SDP signals, allowing these signals to be transmitted independently to the switching device for processing, even if the payload channel bypasses the switching device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the payload channel is routed directly between terminal devices without passing through the switching device, then the communication efficiency and speed are improved, but the switching device cannot recognize DTMF characters and control performance features
Solution Approach 1:
The payload stream is segmented into regular voice data and DTMF signals. The signal processing device extracts DTMF characters from the payload stream and forwards them separately to the switching device, while the main payload stream continues flowing directly between terminal devices. This segmentation allows both direct communication and DTMF recognition to coexist without compromising speed or information loss.
Solution Approach 2:
A signal processing device acts as an intermediary between the direct payload channel and the switching device. This intermediary extracts DTMF signals from the payload stream and relays them to the switching device, enabling the switching device to recognize DTMF characters without the payload channel needing to route through it. The intermediary preserves the direct communication path while enabling signal recognition.
2Reliability
If digital signal processors are integrated into the payload channel to recognize DTMF characters, then DTMF recognition capability is improved, but the device complexity and cost increase
Solution Approach 1:
The signal processing device serves as a specialized intermediary component that handles DTMF recognition. Rather than embedding complex DSP functionality throughout the entire communication system, the intermediary is strategically placed to extract and process only the DTMF signals from the payload stream, forwarding them to the switching device. This localized approach maintains reliability while minimizing overall system complexity.
Solution Approach 2:
The DTMF recognition function is extracted from the main payload channel and handled by a dedicated signal processing device. This extraction allows the primary communication path to remain simple and direct, while the specialized DTMF processing is handled separately by the intermediary, reducing the complexity burden on the core switching and transmission infrastructure.
3Productivity
If the payload channel is bypassed from the switching device, then network efficiency is improved, but the ability to control performance features during conversation is lost
Solution Approach 1:
The signaling function is segmented from the main payload channel. While the payload channel maintains its efficient direct path for voice data, the DTMF signaling is extracted and routed separately to the switching device. This segmentation enables the switching device to receive control signals and manage performance features without compromising the network efficiency of the primary communication path.
Solution Approach 2:
The signal processing device acts as an intermediary that bridges the gap between the bypassed payload channel and the switching device. It captures DTMF signals from the efficient direct path and delivers them to the switching device, enabling performance feature control to be maintained even though the payload channel does not route through the switch, thus preserving both network efficiency and adaptability.
Data Source
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AI summary
A method is specified for the handling of a telecommunications connection between at least two subscribers, wherein the telecommunications connection has a signalling channel for transmission of a signalling stream and a payload channel for the transmission of a payload stream, wherein frequency-coded signals are transmitted in the payload stream, wherein at least one subscriber among the at least two subscribers is assigned to a network which has a switching device and a signal processing device provided separately from the switching device, and wherein the frequency-coded signals are recognised in the signal processing device and are transmitted independently of the payload stream to the switching device. The invention also relates to a telecommunications arrangement, a switching device and a network coupling device.