Spread Spectrum Acoustic Communication Using PONS Codes
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Solution Overview
Problem
Room environments pose challenges for reliable acoustic signal transmission due to extreme multi-path effects, where direct sound is often 20 dB below reverberant sound, making traditional communication methods unreliable.
Innovation Solution
The use of a spread spectrum acoustic communication system based on the Prometheus Orthonormal Set (PONS) codes, which generates orthogonal data and pilot eigenvectors to synchronize and transmit acoustic signals, overcoming multi-path interference by exploiting zero-autocorrelation zones and spread spectrum gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional acoustic communication methods are used in room environments, then the system is simple and easy to implement, but the reliability of signal transmission deteriorates due to multi-path interference and reverberation
Solution Approach 1:
The patent transforms the acoustic signal into the spread spectrum domain by changing its parameter representation. Instead of transmitting traditional acoustic tones and pulses directly, the system modulates the acoustic carrier signal with spread spectrum codes (PONS codes), transforming the signal parameters to include pseudo-random code sequences that provide processing gain and immunity to multi-path interference. This parameter transformation enables reliable communication in reverberant environments while managing system complexity through mathematical signal processing.
2Reliability
If spread spectrum modulation is applied to acoustic signals, then the reliability of communication improves in reverberant environments, but the device complexity increases
Solution Approach 1:
The patent segments the acoustic communication signal into distinct components: a pilot sequence for synchronization and channel estimation, and data sequences for information transmission. Each component is independently processed using PONS code modulation. The pilot sequence uses a specific PONS code (e.g., first row of the PONS matrix) while data sequences use other rows, allowing separate optimization of synchronization and data transmission functions. This segmentation reduces overall system complexity by breaking down the complex spread spectrum modulation into manageable, functionally-separated segments.
Solution Approach 2:
The patent introduces PONS codes as an intermediary mathematical structure that mediates between the acoustic carrier signal and the information to be transmitted. The PONS code matrix serves as an intermediate transformation layer that maps data bits to spread spectrum sequences with desirable autocorrelation and cross-correlation properties. This intermediary structure simplifies the modulation process by providing a systematic way to generate orthogonal sequences, reducing the complexity of signal processing while maintaining reliability in multi-path environments.
3Length of stationary object
If direct path sound is transmitted in a conference room, then the transmission distance can be 30 feet, but the direct sound becomes 20 dB below the reverberant sound, degrading signal quality
Solution Approach 1:
The patent converts the harmful effect of reverberation into a beneficial feature by exploiting the time-dispersive nature of the acoustic channel. Instead of trying to overcome reverberation, the spread spectrum system spreads the transmitted signal over time and frequency, allowing the receiver to correlate and accumulate energy from both direct and reflected paths. The processing gain from spread spectrum modulation (typically 10-20 dB) compensates for the 20 dB loss of direct sound below reverberant sound, transforming the previously harmful reverberant environment into a usable transmission medium that extends effective communication distance.
Data Source
AI summary
In a transmit method, a set of data eigenvectors that are based on a Prometheus Orthonormal Set (PONS) code construction and orthogonal to each other are stored, wherein the data eigenvectors are mapped to unique multi-bit words. A pilot sequence representing a pilot eigenvector that is based on the PONS code construction and orthogonal to each of the data eigenvectors is generated. Input data are grouped into multi-bit words and data eigenvectors among the data eigenvectors are selected based on the multi-bit words. A spread data sequence including the selected data eigenvectors and that is synchronized to the pilot sequence is generated. An acoustic signal including the synchronized pilot sequence and the spread data sequence is generated. The acoustic signal is transmitted.