DTMF Tone Scheduling During Ring Pause Periods
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Solution Overview
Problem
Mobile devices face challenges in reliably detecting Dual Tone MultiFrequency (DTMF) tones over a voice channel while producing a ring progress tone, and often lack access to an active data communication path for status and control information transmission between a PBX server and mobile devices.
Innovation Solution
The system schedules DTMF tones to be processed during pause periods of a ring tone cycle, ensuring they are more likely to be detected by the mobile device, even when the device is generating a ring tone, by estimating delays and rescheduling transmissions accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DTMF tones are transmitted over a voice channel while the mobile device is producing a ring progress tone, then control and status information can be transmitted without requiring an active data path, but the mobile device fails to reliably detect the DTMF tones
Solution Approach 1:
The system performs preliminary actions by scheduling DTMF tone transmissions to occur during pause periods before the ring tone is generated, or by preemptively silencing the ring tone during critical transmission windows. This ensures the detection path is clear before tones are sent, resolving the conflict between maintaining ring progress indication and ensuring reliable tone detection.
Solution Approach 2:
The system utilizes the periodic nature of ring progress tones (alternating between sound and pause periods) to schedule DTMF tone transmissions during the pause periods when the detection path is clear. This periodic scheduling allows control information to be transmitted reliably without requiring a continuous data path, while maintaining the ring progress indication for the user.
2Ease of operation
If the mobile device produces a ring progress tone locally, then the user receives visual and audible feedback about incoming calls, but the device cannot simultaneously detect DTMF tones sent over the same voice channel
Solution Approach 1:
The system segments the communication timeline into distinct phases: ring tone generation periods for user feedback, and pause periods for DTMF tone transmission. By dividing the continuous operation into alternating segments, the device can provide ring progress indication during sound periods while maintaining DTMF detection capability during pause periods, eliminating the interference between these two functions.
Solution Approach 2:
The system exploits the periodic alternation between ring tone generation and pause periods to sequentially perform user feedback provision and control information reception. During pause periods when no ring tone is generated, the detection path becomes available for receiving DTMF tones, thus resolving the conflict between providing continuous user feedback and enabling reliable tone detection.
3Reliability
If a data channel is used for status and control information transmission, then reliable communication is achieved, but the data channel may not always be available
Solution Approach 1:
The voice channel is designed to serve multiple functions: carrying both the ring progress tone for user indication and DTMF tones for control information transmission. By making the voice channel multi-functional, the system eliminates the dependency on a separate data channel while maintaining reliable communication capabilities through intelligent scheduling of different functions during appropriate time periods.
Solution Approach 2:
The pause periods in the ring progress tone cycle act as an intermediary mechanism that enables the voice channel to switch between its two functions. During pause periods, the channel is available for DTMF reception; during ring periods, it provides user feedback. This intermediary timing mechanism allows a single channel to reliably handle both control and indication functions without requiring separate dedicated channels.
Data Source
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AI summary
A computer implemented method for transmitting dual tone multi-frequency (DTMF) tones is disclosed. The method includes sending an indication to a mobile device to start a cyclic ring back tone including ring and pause periods. The delay incurred to send a DTMF back tone to the mobile device is estimated. The server schedules the transmission of the DTMF tone to be received at the mobile device during a pause period of the cyclic ring back tone and the DTMF tone is sent as scheduled.