Time-Varying Frequency Symbols for Sound Wave Communication
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Solution Overview
Problem
Existing sound wave communication techniques face challenges in maintaining effective transmission and reception due to deteriorating frequency characteristics of speakers and microphones, especially at higher frequencies, and require precise frequency synchronization, which complicates implementation and distance measurement.
Innovation Solution
A method and apparatus using time-varying frequency-based symbols that linearly or nonlinearly change with time, allowing for auto and cross correlation within the 20 Hz to 24 kHz sound wave band, independent of specific frequency responses, enabling efficient communication and distance measurement without the need for Phase Lock Loop synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If frequency-based symbols are used for sound wave communication, then data transmission capability is improved, but frequency synchronization complexity and device complexity increase
Solution Approach 1:
The patent changes the parameter of symbol representation from fixed frequency to time-varying frequency. By using symbols whose frequency changes over time (chirp signals), the system achieves better autocorrelation and cross-correlation properties without requiring complex frequency synchronization mechanisms like Phase Lock Loops. This parameter transformation resolves the contradiction by improving data transmission while reducing synchronization complexity.
Solution Approach 2:
The patent introduces dynamic frequency variation in the symbols rather than using static frequency representations. The time-varying frequency characteristics of the symbols allow the system to adapt to channel conditions and improve transmission reliability without adding complex synchronization hardware or algorithms.
2Speed
If high frequency sound waves are used for communication, then bandwidth and data rate are improved, but frequency response deterioration of speaker and microphone increases
Solution Approach 1:
The patent uses dynamic frequency modulation within the symbol structure itself, allowing the signal to sweep through different frequencies rather than remaining at a fixed high frequency. This time-varying approach enables the system to utilize higher bandwidth for faster transmission while the frequency sweeping compensates for the deteriorating frequency response of acoustic transducers at any single high frequency point.
Solution Approach 2:
By changing the frequency parameter over time within each symbol, the system effectively distributes the energy across a frequency range rather than concentrating it at a single high frequency where transducer response deteriorates. This transforms the static frequency limitation into a dynamic solution that maintains both high data rate and reliable transmission.
3Measurement precision
If time-varying frequency-based symbols are used, then autocorrelation and crosscorrelation performance are improved, but signal processing complexity increases
Solution Approach 1:
The patent changes the temporal parameter of the signal from constant frequency to time-varying frequency, which inherently provides superior autocorrelation and cross-correlation properties. The frequency modulation embedded in the symbol structure creates distinctive temporal patterns that are easily distinguishable, improving measurement precision without requiring complex correlation algorithms.
4Reliability
If frequency synchronization mechanisms are implemented, then communication reliability is improved, but device complexity and implementation difficulty increase
Solution Approach 1:
The patent uses dynamic frequency variation in symbols to achieve reliable communication without static frequency synchronization. The time-varying nature of the symbols provides inherent robustness against frequency offsets and drift, eliminating the need for complex Phase Lock Loop circuits or sophisticated synchronization algorithms while maintaining high communication reliability.
Data Source
AI summary
A method for transmitting sound waves using a time-varying frequency-based symbol includes the steps of: storing waveform data in a digital form; converting the waveform data in the digital form into an analog signal; and outputting the analog signal as sound waves through a speaker. Herein, the waveform data in the digital form includes a symbol the frequency of which changes with time within a sound wave band.