DTMF Tone Timing Serialization for Telephony Control
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Solution Overview
Problem
Voice telephony systems, particularly in third-party call control scenarios, face challenges in reliable transmission and error handling of DTMF tones over voice channels due to the lack of sequencing and error recovery mechanisms, leading to inefficiencies in feature code transmission and response processing.
Innovation Solution
The implementation of a method that serializes timers for DTMF tone transmission and reception, introducing delays and retry mechanisms to ensure accurate feature code transmission and error correction, even in the absence of a data channel, by using a mobile device with a processing module capable of handling voice channel processing and DTMF tone synthesis and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DTMF tones are transmitted over voice channels without sequencing mechanisms, then transmission simplicity is maintained, but reliability of feature code transmission deteriorates
Solution Approach 1:
The patent segments the DTMF transmission process into distinct phases: tone generation phase, inter-digit silence phase, and reception phase. By dividing the continuous transmission into discrete time segments with specific durations, the system achieves reliable feature code transmission through structured timing without requiring complex continuous monitoring mechanisms.
Solution Approach 2:
The patent implements preliminary timing actions by pre-configuring inter-digit gaps and tone durations before transmission begins. The system prepares the timing sequence in advance, establishing the rhythm and structure of DTMF transmission beforehand, which ensures reliable execution during actual transmission without real-time decision complexity.
2Reliability
If DTMF tones are transmitted without error recovery mechanisms, then system simplicity is maintained, but error handling capability deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the receiving端 monitors incoming DTMF tones and provides implicit feedback through acknowledgment of received feature codes. The system uses timing-based feedback to detect transmission errors and trigger retry sequences, achieving reliable error handling through structured feedback loops rather than complex error correction algorithms.
Solution Approach 2:
The patent prepares error recovery measures in advance by pre-configuring retry counters and timeout thresholds. Before transmission errors occur, the system establishes the parameters for error recovery, including maximum retry attempts and inter-retry timing, which cushion against potential transmission failures without requiring complex real-time error analysis.
3Measurement precision
If inter-digit gaps are extended to prevent tone overlap, then transmission accuracy is improved, but call setup time increases
Solution Approach 1:
The patent optimizes the balance between accuracy and speed by dynamically adjusting inter-digit gap parameters based on transmission conditions. The system modifies timing parameters such as gap duration and tone frequency to achieve the minimum necessary separation for accurate detection, thereby preventing tone overlap while minimizing call setup time through parameter optimization rather than fixed conservative timing.
Data Source
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AI summary
Control and status information between a mobile device and another device can be signaled over a voice channel using DTMF tones, e.g., a pre-defined sequence of DTMF tones can signal a desired message (more generally, a feature code). Tones sent are separated from each other by a time gap (Tgap timer). If a receiving device does not receive a sequence of DTMF tones that can be matched to stored definitions of feature codes, then the receiving device generates a negative ACK. Also, if the sending device does not receive either negative or positive ACK, then sending device resends all tones of the feature code after a retry delay (Tretry timer). Rather than having the Tretry timer start when tones for a feature code start to be transmitted, the Tretry timer is started after the Tgap timer expires for the last tone of a feature code. Thus, only one timer is running (either Tgap or Tretry), rather than having multiple timers running concurrently. Race conditions between the timers are avoided.