DTMF Digit Detection in Wireless Systems
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Solution Overview
Problem
DTMF digits experience severe degradation during transmission in wireless communication systems, making it difficult for receiving devices to differentiate between them.
Innovation Solution
A system and method for robust DTMF digit detection, including an automatic gain controller, single tone detector, dual tone detector, and DTMF digit determiner, which adjust energy levels, identify frequencies, and determine the presence of DTMF digits by analyzing energy levels and frequency ratios within incoming frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DTMF digits are transmitted through the speech signal routing path in a conventional wireless system, then the transmission can be performed using existing infrastructure, but the DTMF digits experience severe degradation making differentiation difficult
Solution Approach 1:
The patent segments the DTMF detection process into distinct functional modules: automatic gain controller, single tone detector, dual tone detector, and DTMF digit determiner. Each module handles a specific aspect of the detection process, allowing for specialized optimization of each component to improve overall detection accuracy despite transmission degradation.
Solution Approach 2:
The automatic gain controller performs preliminary energy level adjustment on the received signal before it reaches the tone detectors. By pre-processing the signal to normalize energy levels, the system prepares the input for subsequent detection stages, improving the reliability of frequency differentiation even when the original transmission was degraded.
2Measurement precision
If automatic gain control is applied to adjust energy levels of tone samples, then detection accuracy is improved, but system complexity increases due to additional processing components
Solution Approach 1:
The automatic gain controller serves multiple functions: it normalizes energy levels for accurate detection, prevents saturation of subsequent detection stages, and maintains consistent signal levels across varying transmission conditions. This multi-functionality justifies the added component by providing multiple benefits from a single processing stage.
Solution Approach 2:
The automatic gain controller acts as an intermediary component between the received signal and the tone detectors. It mediates the energy levels of the input signal, ensuring that the subsequent detection stages receive optimally conditioned signals without being overwhelmed by excessive energy or lost due to insufficient energy.
3Measurement precision
If frequency analysis is performed to identify tone frequencies, then DTMF digit identification is enabled, but processing time and computational resources increase
Solution Approach 1:
The frequency analysis is segmented into two separate detection stages: single tone detector identifies individual frequency components, and dual tone detector combines these to identify DTMF digits. This segmentation allows each detector to focus on specific frequency ranges and patterns, improving computational efficiency while maintaining accurate frequency identification.
Solution Approach 2:
The system performs frequency analysis with sufficient precision to accurately identify DTMF digits by detecting the characteristic frequency pairs. Rather than performing exhaustive spectral analysis across all possible frequencies, the detectors focus on the specific frequency ranges relevant to DTMF signaling, achieving adequate precision with reduced computational effort.
Data Source
AI summary
In a system for performing dual-tone multi-frequency (DTMF) digit detection, an automatic gain controller receives an incoming frame carrying at least one tone sample and adjusts the energy level of the at least one tone sample responsive to the energy level exceeding a frame energy threshold. A single tone detector determines at least one frequency of the at least one tone sample in the incoming frame. A dual tone detector identifies an energy level of each of the determined frequencies and generates an indication of whether a DTMF digit is present in the incoming frame responsive to a first determined frequency corresponding to a frequency in a first grouping of frequencies and a second determined frequency corresponding to a frequency in a second grouping of frequencies. A DTMF digit determiner for determining a DTMF digit based on the indication.